0001193125-21-269987 | S-1 | XBRL Viewer

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Cover Page	6 Months Ended
Cover Page	Jun. 30, 2021
Cover [Abstract]
Document Type	S-1
Amendment Flag	false
Entity Registrant Name	TANGO THERAPEUTICS, INC.
Entity Central Index Key	0001819133
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 50,902	$ 28,381	$ 22,889
Marketable securities	147,452	161,939	17,536
Accounts receivable	2,000	2,000	0
Prepaid expenses and other current assets	1,707	1,312	1,231
Total current assets	202,061	193,632	41,656
Property and equipment, net	4,397	3,823	3,442
Operating lease right-of-use assets	6,988	7,480	8,387
Restricted cash	2,279	2,279	2,279
Other assets	1,515	38	0
Total assets	217,240	207,252	55,764
Current liabilities:
Accounts payable	5,242	1,841	670
Accrued expenses and other current liabilities	6,434	6,140	4,932
Operating lease liabilities	1,047	959	655
Deferred revenue	24,500	31,977	19,594
Total current liabilities	37,223	40,917	25,851
Operating lease liabilities, net of current portion	6,384	6,925	7,884
Deferred revenue, net of current portion	118,742	120,805	14,106
Other long-term liabilities	0	5	18
Total liabilities	162,349	168,652	47,859
Commitments and contingencies
Stockholders' deficit:
Common stock	15	13	13
Additional paid-in capital	8,040	5,127	3,311
Accumulated other comprehensive income	2	17	10
Accumulated deficit	(119,700)	(103,101)	(51,129)
Total stockholders' deficit	(111,643)	(97,944)	(47,795)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	217,240	207,252	55,764
Series A Preferred Stock [Member]
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	55,700	55,700	55,700
Stockholders' deficit:
Total stockholders' deficit	55,700	55,700	55,700
Series B Preferred Stock [Member]
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	59,751	29,761	0
Stockholders' deficit:
Total stockholders' deficit	59,751	29,761	0
Series B 1Preferred Stock [Member]
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	51,083	51,083	0
Stockholders' deficit:
Total stockholders' deficit	$ 51,083	$ 51,083	$ 0

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Common Stock, Shares Authorized	166,000,000	166,000,000	80,800,000
Common Stock, Shares, Issued	14,817,103	13,301,649	13,334,856
Common Stock, Shares, Outstanding	14,817,103	13,301,649	13,334,856
Series A Preferred Stock [Member]
Temporary Equity, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Temporary Equity, Shares Authorized	55,700,000	55,700,000	55,700,000
Temporary Equity, Shares Issued	55,700,000	55,700,000	55,700,000
Temporary Equity, Shares Outstanding	55,700,000	55,700,000	55,700,000
Temporary Equity, Liquidation Preference	$ 55,700	$ 55,700	$ 55,700
Series B Preferred Stock [Member]
Temporary Equity, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Temporary Equity, Shares Authorized	45,372,050	45,372,050	0
Temporary Equity, Shares Issued	45,372,050	22,686,025	0
Temporary Equity, Shares Outstanding	45,372,050	22,686,025	0
Temporary Equity, Liquidation Preference	$ 60,000	$ 30,000	$ 0
Series B 1Preferred Stock [Member]
Temporary Equity, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Temporary Equity, Shares Authorized	27,152,255	27,152,255	0
Temporary Equity, Shares Issued	27,152,255	27,152,255	0
Temporary Equity, Shares Outstanding	27,152,255	27,152,255	0
Temporary Equity, Liquidation Preference	$ 51,182	$ 51,182	$ 0

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 18,153	$ 5,064	$ 24,539	$ 9,775
Operating expenses:
Research and development	19,079	11,129	34,079	21,951	$ 49,991	$ 32,274
General and administrative	3,630	2,378	7,097	4,331	9,865	7,537
Total operating expenses	22,709	13,507	41,176	26,282	59,856	39,811
Loss from operations	(4,556)	(8,443)	(16,637)	(16,507)	(52,200)	(15,162)
Other income:
Interest income	104	27	208	87	108	684
Other (expense) income, net	(62)	24	(117)	114	120	383
Total other income, net	42	51	91	201	228	1,067
Net loss before income taxes	(4,514)	(8,392)	(16,546)	(16,306)
Benefit from (provision for) income taxes	21	0	(53)	0	0	0
Net loss	$ (4,493)	$ (8,392)	$ (16,599)	$ (16,306)	$ (51,972)	$ (14,095)
Net loss per common share – basic and diluted	$ (0.31)	$ (0.75)	$ (1.17)	$ (1.49)	$ (4.53)	$ (1.57)
Weighted average number of common shares outstanding – basic and diluted	14,485,746	11,193,065	14,214,543	10,913,053	11,461,011	8,985,710
Net loss	$ (4,493)	$ (8,392)	$ (16,599)	$ (16,306)	$ (51,972)	$ (14,095)
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities	(30)	(14)	(15)	1	7	17
Comprehensive loss	(4,523)	(8,406)	(16,614)	(16,305)	(51,965)	(14,078)
Collaboration Revenue [Member]
Total revenue	7,153	4,720	13,539	9,106	$ 7,656	$ 24,649
License Revenue [Member]
Total revenue	$ 11,000	$ 344	$ 11,000	$ 669

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Series B 1Preferred Stock [Member]
Balance at the beginning at Dec. 31, 2018	$ (35,426)	$ 14	$ 1,601	$ (7)	$ (37,034)	$ 44,700	$ 0	$ 0
Balance at the beginning (in shares) at Dec. 31, 2018		14,522,360				44,700,000	0	0
Issuance of redeemable convertible preferred stock						$ 11,000
Issuance of redeemable convertible preferred stock, (in shares)						11,000,000
Repurchases of restricted common stock awards		$ (1)	1
Repurchases of restricted common stock awards, (in shares)		(1,187,504)
Vesting of restricted common stock awards	15		15
Stock based compensation expense	1,694		1,694
Other comprehensive income (loss)	17			17
Net loss	(14,095)				(14,095)
Balance at the ending at Dec. 31, 2019	(47,795)	$ 13	3,311	10	(51,129)	$ 55,700	$ 0	$ 0
Balance at the ending (in shares) at Dec. 31, 2019		13,334,856				55,700,000	0	0
Repurchases of restricted common stock awards, (in shares)		(75,000)
Vesting of restricted common stock awards	3		3
Stock based compensation expense	408		408
Other comprehensive income (loss)	15			15
Net loss	(7,914)				(7,914)
Balance at the ending at Mar. 31, 2020	(55,283)	$ 13	3,722	25	(59,043)	$ 55,700	$ 0
Balance at the ending (in shares) at Mar. 31, 2020		13,259,856				55,700,000	0
Balance at the beginning at Dec. 31, 2019	(47,795)	$ 13	3,311	10	(51,129)	$ 55,700	$ 0	$ 0
Balance at the beginning (in shares) at Dec. 31, 2019		13,334,856				55,700,000	0	0
Net loss	(16,306)
Balance at the ending at Jun. 30, 2020	(63,270)	$ 13	4,141	11	(67,435)	$ 55,700	$ 29,761
Balance at the ending (in shares) at Jun. 30, 2020		13,279,543				55,700,000	22,686,025
Balance at the beginning at Dec. 31, 2019	(47,795)	$ 13	3,311	10	(51,129)	$ 55,700	$ 0	$ 0
Balance at the beginning (in shares) at Dec. 31, 2019		13,334,856				55,700,000	0	0
Issuance of redeemable convertible preferred stock							$ 29,761	$ 51,083
Issuance of redeemable convertible preferred stock, (in shares)							22,686,025	27,152,255
Exercise of stock options	40		40
Exercise of stock options, (in shares)		81,870
Repurchases of restricted common stock awards, (in shares)		(115,077)
Vesting of restricted common stock awards	12		12
Stock based compensation expense	1,764		1,764
Other comprehensive income (loss)	7			7
Net loss	(51,972)				(51,972)
Balance at the ending at Dec. 31, 2020	(97,944)	$ 13	5,127	17	(103,101)	$ 55,700	$ 29,761	$ 51,083
Balance at the ending (in shares) at Dec. 31, 2020		13,301,649				55,700,000	22,686,025	27,152,255
Balance at the beginning at Mar. 31, 2020	(55,283)	$ 13	3,722	25	(59,043)	$ 55,700	$ 0
Balance at the beginning (in shares) at Mar. 31, 2020		13,259,856				55,700,000	0
Issuance of redeemable convertible preferred stock							$ 29,761
Issuance of redeemable convertible preferred stock, (in shares)							22,686,025
Exercise of stock options	9		9
Exercise of stock options, (in shares)		19,687
Vesting of restricted common stock awards	3		3
Stock based compensation expense	407		407
Other comprehensive income (loss)	(14)			(14)
Net loss	(8,392)				(8,392)
Balance at the ending at Jun. 30, 2020	(63,270)	$ 13	4,141	11	(67,435)	$ 55,700	$ 29,761
Balance at the ending (in shares) at Jun. 30, 2020		13,279,543				55,700,000	22,686,025
Balance at the beginning at Dec. 31, 2020	(97,944)	$ 13	5,127	17	(103,101)	$ 55,700	$ 29,761	$ 51,083
Balance at the beginning (in shares) at Dec. 31, 2020		13,301,649				55,700,000	22,686,025	27,152,255
Issuance of redeemable convertible preferred stock							$ 29,990
Issuance of redeemable convertible preferred stock, (in shares)							22,686,025
Exercise of stock options	440	$ 1	439
Exercise of stock options, (in shares)		895,093
Vesting of restricted common stock awards	2		2
Stock based compensation expense	950		950
Other comprehensive income (loss)	15			15
Net loss	(12,106)				(12,106)
Balance at the ending at Mar. 31, 2021	(108,643)	$ 14	6,518	32	(115,207)	$ 55,700	$ 59,751	$ 51,083
Balance at the ending (in shares) at Mar. 31, 2021		14,196,742				55,700,000	45,372,050	27,152,255
Balance at the beginning at Dec. 31, 2020	(97,944)	$ 13	5,127	17	(103,101)	$ 55,700	$ 29,761	$ 51,083
Balance at the beginning (in shares) at Dec. 31, 2020		13,301,649				55,700,000	22,686,025	27,152,255
Net loss	(16,599)
Balance at the ending at Jun. 30, 2021	(111,643)	$ 15	8,040	2	(119,700)	$ 55,700	$ 59,751	$ 51,083
Balance at the ending (in shares) at Jun. 30, 2021		14,817,103				55,700,000	45,372,050	27,152,255
Balance at the beginning at Mar. 31, 2021	(108,643)	$ 14	6,518	32	(115,207)	$ 55,700	$ 59,751	$ 51,083
Balance at the beginning (in shares) at Mar. 31, 2021		14,196,742				55,700,000	45,372,050	27,152,255
Exercise of stock options	324	$ 1	323
Exercise of stock options, (in shares)		620,361
Vesting of restricted common stock awards	3		3
Stock based compensation expense	1,196		1,196
Other comprehensive income (loss)	(30)			(30)
Net loss	(4,493)				(4,493)
Balance at the ending at Jun. 30, 2021	$ (111,643)	$ 15	$ 8,040	$ 2	$ (119,700)	$ 55,700	$ 59,751	$ 51,083
Balance at the ending (in shares) at Jun. 30, 2021		14,817,103				55,700,000	45,372,050	27,152,255

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Jun. 30, 2020	Dec. 31, 2020
Series B Preferred Stock [Member]
Issuance of redeemable convertible preferred stock, net of issuance costs	$ 0.1		$ 0.2
Series B 1Preferred Stock [Member]
Issuance of redeemable convertible preferred stock, net of issuance costs		$ 0.2	$ 0.1

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (16,599)	$ (16,306)	$ (51,972)	$ (14,095)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	416	341	718	643
Noncash operating lease expense	492	442	907	831
Stock-based compensation	2,146	815	1,764	1,694
Other, net	118	(98)	(17)	(347)
Changes in operating assets and liabilities:
Accounts receivable			(2,000)	0
Prepaid expenses and other current assets	(395)	361	(119)	(590)
Other long-term assets	13	0
Accounts payable	2,749	1,440	1,171	(976)
Accrued expenses and other liabilities	(78)	34	1,196	2,964
Operating lease liabilities	(454)	(377)	(655)	(678)
Deferred revenue	(9,539)	(9,775)	119,081	(14,249)
Net cash used in operating activities	(21,131)	(23,123)	70,074	(24,803)
Cash flows from investing activities
Purchase of property and equipment	(367)	(518)	(1,106)	(1,817)
Sales and maturities of marketable securities	100,471	16,327	63,220	35,246
Purchases of marketable securities	(86,117)	(32,316)	(207,540)	(32,581)
Other			(40)	0
Net cash provided by (used in) investing activities	13,987	(16,507)	(145,466)	848
Cash flows from financing activities
Proceeds from issuance of preferred stock, net of issuance costs of $0.3 million and $0 during the periods ended December 31, 2020 and 2019, respectively	29,990	29,850	80,844	11,000
Proceeds from issuance of common stock upon exercise of stock options	764	9	40	0
Payment of merger with BCTG and PIPE financing transaction costs	(1,089)	0
Net cash provided by financing activities	29,665	29,859	80,884	11,000
Net change in cash, cash equivalents and restricted cash	22,521	(9,771)	5,492	(12,955)
Cash, cash equivalents and restricted cash, beginning of period	30,660	25,168	25,168	38,123
Cash, cash equivalents and restricted cash, end of period	53,181	15,397	30,660	25,168
Supplemental cash flow information:
Cash paid for leases	907	880	1,782	1,735
Supplemental disclosure of noncash investing and financing activity:
Purchases of property and equipment included in accounts payable and accrued expenses	653	48	$ 29	$ 0
Merger with BCTG and PIPE financing deferred offering costs included in accounts payable and accrued expenses	$ 401	$ 0

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Payments of Stock Issuance Costs	$ 0.3	$ 0.0

Nature of the Business and Basis of Presentation	6 Months Ended	12 Months Ended
Nature of the Business and Basis of Presentation	Jun. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Tango Therapeutics, Inc (“Tango” or the “Company”) is a precision oncology company committed to the discovery and development of novel new drugs in defined patient populations with high unmet medical need. The Company is subject to risks common to early-stage companies in the biotechnology industry. Principal among these risks are the uncertainties of the development process, development of the same or similar technological innovations by competitors, protection of proprietary technology, dependence on key personnel, compliance with government regulations and approval requirements, and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance-reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval, or that any approved products will be commercially viable. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. If the Company fails to become profitable or is unable to sustain profitability on a continuing basis, then the Company may be unable to continue its operations at planned levels and be forced to reduce or terminate its operations. The Company expects to incur substantial operating losses and negative cash flows from operations for the foreseeable future. Since inception, the Company has generated recurring net losses, including net losses of $4.5 million and $16.6 million for the three and six months ended June 30, 2021, respectively, and net losses of $8.4 million and $16.3 million for the three and six months ended June 30, 2020, respectively. The Company had an accumulated deficit of $119.7 million as of June 30, 2021. Since inception and through the issuance date of these unaudited condensed consolidated financial statements, the Company has raised an aggregate of approximately $166.9 million of gross proceeds from the sale of preferred shares, approximately $352.9 million in gross proceeds through the closing of the BCTG Business Combination and PIPE Investment transactions and another $202.1 million through our collaboration with Gilead. The Company expects operating losses and negative cash flows from operations to continue for the foreseeable future as it continues to develop, manufacture and commercialize its products. As of June 30, 2021, and with the additional gross proceeds of approximately $352.9 million received on August 10, 2021 from the consummation of the BCTG Business Combination and PIPE Investment transactions, the Company expected that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of the unaudited condensed consolidated financial statements. The future viability of the Company beyond that point may be dependent on its ability to raise additional capital to finance its operations. The Company may seek additional funding in the future, from one or more equity or debt financings, collaborations, or other sources, in order to carry out all of its planned research and development and commercialization activities. However, there is no assurance that the Company will be able to obtain additional funding under acceptable terms, if at all. If the Company is unable to obtain additional financing, the Company may be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. Merger with BCTG Acquisition Corporation On April 13, 2021, the Company and BCTG Acquisition Corp. (“BCTG”) signed a definitive merger agreement memorializing the terms of BCTG’s acquisition of 100% of the Company’s issued and outstanding equity securities in exchange for $550.0 million worth of consideration in the form of BCTG common stock (the “Business Combination”). The Business Combination was approved on August 9, 2021 by shareholders of BCTG, resulting in BCTG acquiring 100% of our issued and outstanding equity securities on August 10, 2021. The Business Combination was accounted for as a “reverse recapitalization” in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Under the reverse recapitalization model, the Business Combination was treated as Tango issuing equity for the net assets of BCTG, with no goodwill or intangible assets recorded. Under this method of accounting, BCTG was treated as the “acquired” company for financial reporting purposes. This determination was primarily based on the fact that subsequent to the Business Combination, the Company’s stockholders possess a majority of the voting power of the combined company, the Company comprises all of the ongoing operations of the combined entity, the Company comprises a majority of the governing body of the combined company, and the Company’s senior management comprises all of the senior management of the combined company. As a result of the Business Combination, BCTG was renamed Tango Therapeutics, Inc. Tango received gross proceeds of $166.8 million upon the closing of the Business Combination. Tango continues to operate under the current Tango management team. Subsequent to the closing of the Business Combination, an aggregate of 18.6 million shares of common stock (the “PIPE Financing”) were purchased, resulting in gross proceeds of an additional $186.1 million upon the closing of the PIPE Financing. Total transaction costs and redemptions approximated $27.3 million, resulting in total net proceeds of $325.6 million. Subject to the terms of the merger agreement, upon the closing of the Business Combination (the “Effective Time”), each share of the Company’s redeemable convertible preferred stock (the “Preferred Stock”) issued and outstanding immediately prior to the Effective Time was converted into a share of the Company’s common stock. At the Effective Time, each option to purchase the Company’s common stock became an option, respectively, to purchase shares of common stock of the surviving entity, subject to adjustment in accordance with the exchange ratio. Completion of the PIPE Financing and merger transaction were subject to approval of BCTG stockholders and the satisfaction or waiver of certain other customary closing conditions. Impact of COVID-19 At the end of 2019, a novel strain of a virus named SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), or coronavirus, which causes COVID-19 has spread to most countries across the world, including all 50 states within the U.S., including Cambridge, Massachusetts, where the Company’s primary office and laboratory space is located. The coronavirus pandemic led to the implementation of various responses, including government-imposed quarantines, travel restrictions and other public health safety measures. The extent to which the coronavirus, including any novel variants such as the “Delta variant,” impacts the Company’s operations or those of its third-party partners, including preclinical studies or clinical trial operations, will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the duration of the outbreak, new information that will emerge concerning the severity of the coronavirus and the actions to contain the coronavirus or treat its impact, among others. The continued spread of COVID-19 globally could adversely impact the Company’s preclinical or clinical trial operations in the U.S., including its ability to recruit and retain patients and principal investigators and site staff who, as healthcare providers, may have heightened exposure to COVID-19 if an outbreak occurs in their geography. The Company is monitoring the potential impact of the COVID-19 pandemic on its business and financial statements. To date, COVID-19 has not had a material impact on operations, and the Company has not incurred significant delays related to its research and development programs. Additionally, the Company has not incurred impairment losses in the carrying values of its assets as a result of the pandemic and it is not aware of any specific related event or circumstance that would require it to revise its estimates reflected in these condensed consolidated financial statements. The extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations, financial condition and liquidity, including research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19, the actions taken to contain or treat it, and the duration and intensity of the related effects. Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with U.S. GAAP. The year-end balance sheet data was derived from audited financial statements, but do e s not include all disclosures required by U.S. GAAP. The accompanying unaudited condensed consolidated financial statements reflect the operations of Tango and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated. The functional and reporting currency of the Company and its subsidiary is the U.S. dollar. In the opinion of management, all adjustments necessary for a fair statement of the financial information, which are of a normal and recurring nature, have been made for the interim periods reported. Results of operations for the three and six months ended June 30, 2021 and 2020 are not necessarily indicative of the results for the year ending December 31, 2021, any other interim periods, or any future year or period. The unaudited condensed consolidated financial statements for the three and six months ended June 30, 2021 and 2020 have been prepared on the same basis as and should be read in conjunction with the audited consolidated financial statements and notes for the year ended December 31, 2020 included in the Company’s effective proxy statement/prospectus, on file with the SEC on July 16, 2021.	1. Nature of the Business and Basis of Presentation Tango Therapeutics, Inc (“Tango” or the “Company”) is a precision oncology company committed to the discovery and development of novel new drugs in defined patient populations with high unmet medical need. The Company is subject to risks common to early-stage companies in the biotechnology industry. Principal among these risks are the uncertainties of the development process, development of the same or similar technological innovations by competitors, protection of proprietary technology, dependence on key personnel, compliance with government regulations and approval requirements, and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical, clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance-reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval, or that any approved products will be commercially viable. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. If the Company fails to become profitable or is unable to sustain profitability on a continuing basis, then the Company may be unable to continue its operations at planned levels and be forced to reduce or terminate its operations. The Company expects to incur substantial operating losses and negative cash flows from operations for the foreseeable future. Since inception, the Company has generated recurring net losses, including a net loss of $52.0 million and $14.1 million for the years ended December 31, 2020 and 2019, respectively. The Company had an accumulated deficit of $103.1 million and $51.1 million as of December 31, 2020 and 2019, respectively. Since inception and through the issuance date of these consolidated financial statements, the Company has raised an aggregate of approximately $166.9 million of gross proceeds from the sale of preferred shares. The Company expects operating losses and negative cash flows from operations to continue for the foreseeable future as it continues to develop, manufacture and commercialize its products. As of April 12, 2021, the issuance date of the consolidated financial statements for the year ended December 31, 2020, the Company expected that its cash, cash equivalents and marketable securities, and the $30.0 of additional proceeds from the closing of the second tranche of the Series B convertible preferred stock purchase agreement (see Note 14) received in March 2021, will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of the annual consolidated financial statements. The future viability of the Company beyond that point may be dependent on its ability to raise additional capital to finance its operations. The Company may seek additional funding in the future, from one or more equity or debt financings, collaborations, or other sources, in order to carry out all of its planned research and development and commercialization activities. However, there is no assurance that the Company will be able to obtain additional funding under acceptable terms, if at all. If the Company is unable to obtain additional financing, the Company may be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. Merger with BCTG Acquisition Corporation (Unaudited) On April 13, 2021, the Company and BCTG Acquisition Corp. (“BCTG”) signed a definitive merger agreement, which will result in BCTG acquiring 100% of the Company’s issued and outstanding equity securities. The proposed merger will be accounted for as a “reverse recapitalization” in accordance with U.S. GAAP. Under the reverse recapitalization model, the Business Combination will be treated as Tango issuing equity for the net assets of BCTG, with no goodwill or intangible assets recorded. Under this method of accounting, BCTG will be treated as the “acquired” company for financial reporting purposes. This determination is primarily based on the fact that subsequent to the merger, the Company’s stockholders are expected to have a majority of the voting power of the combined company, the Company will comprise all of the ongoing operations of the combined entity, the Company will comprise a majority of the governing body of the combined company, and the Company’s senior management will comprise all of the senior management of the combined company. As a result of the proposed merger, BCTG will be renamed Tango Therapeutics, Inc. The boards of directors of both BCTG and Tango have approved the proposed merger transaction. BCTG is expected to receive net proceeds of approximately $156.9 million upon the closing of the proposed merger transaction, assuming no redemptions are affected by stockholders of BCTG, and will operate under the current Tango management team upon the closing of the proposed merger. In connection with the proposed merger, BCTG has entered into agreements with existing and new investors to subscribe for and purchase an aggregate of 18.6 million shares of its common stock (the “PIPE Financing”) that will result in net proceeds of an additional $179.7 million upon the closing of the PIPE Financing. The closing of the proposed merger is a precondition to the PIPE Financing. Subject to the terms of the merger agreement, at the effective time of the merger (the “Effective Time”), each share of the Company’s redeemable convertible preferred stock “Preferred Stock” issued and outstanding immediately prior to the Effective Time shall be converted into a share of the Company’s common stock. At the Effective Time, each option to purchase the Company’s common stock shall become an option, respectively, to purchase shares of common stock of the surviving entity, subject to adjustment in accordance with the exchange ratio. Completion of the PIPE Financing and proposed merger transactions is subject to approval of BCTG stockholders and the satisfaction or waiver of certain other customary closing conditions. The approval from BCTG stockholders is expected in the third quarter of 2021. Impact of COVID-19 At the end of 2019, a novel strain of a virus named SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), or coronavirus, which causes COVID-19 has spread to most countries across the world, including all 50 states within the U.S., including Cambridge, Massachusetts, where the Company’s primary office and laboratory space is located. The coronavirus pandemic led to the implementation of various responses, including government-imposed quarantines, travel restrictions and other public health safety measures. The extent to which the coronavirus impacts the Company’s operations or those of its third-party partners, including preclinical studies or clinical trial operations, will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the duration of the outbreak, new information that will emerge concerning the severity of the coronavirus and the actions to contain the coronavirus or treat its impact, among others. The continued spread of COVID-19 globally could adversely impact the Company’s preclinical or clinical trial operations in the U.S., including it’s ability to recruit and retain patients and principal investigators and site staff who, as healthcare providers, may have heightened exposure to COVID-19 if an outbreak occurs in their geography. The Company is monitoring the potential impact of the COVID-19 pandemic on its business and financial statements. To date, COVID-19 has not had a material impact on operations, and the Company has not incurred significant delays related to its research and development programs. Additionally, the Company has not incurred impairment losses in the carrying values of its assets as a result of the pandemic and it is not aware of any specific related event or circumstance that would require it to revise its estimates reflected in these consolidated financial statements. The extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations, financial condition and liquidity, including research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19, the actions taken to contain or treat it, and the duration and intensity of the related effects. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The accompanying consolidated financial statements reflect the operations of Tango and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated. The functional and reporting currency of the Company and its subsidiary is the U.S. dollar.

Summary of Significant Accounting Policies

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Other than policies noted below, there have been no significant changes from the significant accounting policies disclosed in Note 2,

Summary of Significant Accounting Policies

, of the audited consolidated financial statements and notes for the year ended December 31, 2020 included in the Company’s effective proxy statement/prospectus, on file with the SEC on July 16, 2021.

Recently Adopted Accounting Pronouncements

In December 2019, the FASB issued ASU

2019-12,

Simplifying the Accounting for Income Taxes,

(“ASC 740”). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis

step-up

in goodwill obtained in a transaction that is not a business combination, separate financial statements of entities not subject to tax, the intra-period tax allocation exception to the incremental approach, ownership changes in investments, changes from a subsidiary to an equity method investment, interim-period accounting for enacted changes in tax law, and the

year-to-date

loss limitation in interim-period tax accounting. This guidance is effective for the Company for annual and interim periods beginning after December 31, 2020; however, early adoption was permitted The Company adopted this standard as of January 1, 2021 on a prospective basis. The adoption did not have a material impact on the Company’s condensed consolidated financial statements.

In August 2020, the FASB issued ASU

2020-06,

Debt

— Debt with Conversion and Other Options (Subtopic

470-20)

and Derivatives and Hedging

— Contracts in Entity’s Own Equity (Subtopic 815

— 40)

settled in cash or shares impact the diluted earnings per share (“EPS”) computation. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. The Company elected to early adopt this guidance on January 1, 2021. The Company issued the second tranche of its redeemable convertible Series B preferred stock in March 2021 at an original issue price of $1.32 per share, which would have resulted in the recognition of a beneficial conversion feature of $28.4 million prior to the adoption of ASU

2020-06.

Recently Issued Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements.

2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of consolidated financial statements requires that the Company make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, equity, revenues and expenses and related disclosure of contingent assets and liabilities. Significant estimates and assumptions made in the consolidated financial statements include, but are not limited to, the revenue recognized from collaboration agreements, the valuation of common shares and stock-based awards and the accrual for research and development expenses. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets, liabilities and equity and the amount of revenues and expenses. As of the date of issuance of these consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update estimates, judgments or revise the carrying value of any assets or liabilities related to COVID-19. Actual results may differ from these estimates under different assumptions or conditions. Changes in estimates are reflected in reported results in the period in which they become known.

Segment Information

Operating segments are defined as components of an enterprise for which separate financial information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company operates in one operating segment, the business of discovering and developing precision oncology therapies.

Cash Equivalents

All highly liquid marketable securities purchased with an original maturity date of 90 days or less at the date of purchase are considered to be cash equivalents. Cash equivalents consisted of money market funds and U.S Treasury bills as of December 31, 2020 and 2019.

Investments in Marketable Securities

Marketable debt securities consist of investments with original maturities greater than 90 days. The Company classifies its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. The Company considers its investment portfolio of marketable securities to be

available-for-sale.

Accordingly, these investments are recorded at fair value, which is based on quoted market prices. Unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity (deficit). Amortization and accretion of premiums and discounts are recorded in interest income. Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other income, net in the consolidated statements of operations.

The Company evaluates its investments with unrealized losses for impairment. When assessing investments for unrealized declines in value, the Company considers whether the decline in value is related to a credit loss or

non-credit

loss. For credit losses, the Company reduces the investment to fair value through an allowance for credit losses recorded to the balance sheet and corresponding charge to the statement of operations. The allowance for credit losses and corresponding impairment charge is adjusted each period for changes in fair value. For

non-credit

losses, the Company reduces the investment to fair value through a charge to the statement of comprehensive loss, reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. No such credit losses were recorded during the periods presented.

Prior to the early adoption of ASU

2016-13

, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,

on January 1, 2020, the Company evaluated its investments with unrealized losses for other-than-temporary impairment. If any adjustment to fair value reflected a decline in the value of the investment that the Company considered to be “other than temporary,” the Company would reduce the investment to fair value through a charge to the consolidated statements of operations.

Fair Value Measurements

The accounting standard for fair value measurements defines fair value, establishes a framework for measuring fair value in accordance with U.S. GAAP, and requires certain disclosures about fair value measurements. Under this standard, fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

Level 1 — Fair values are determined utilizing prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access.

•

Level 2 — Fair values are determined by utilizing quoted prices for identical or similar assets and liabilities in active markets or other market observable inputs such as interest rates, yield curves, and foreign currency spot rates.

•

Level 3 — Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

The fair value of the Company’s cash equivalents and marketable securities are determined according to the fair value hierarchy described above (see Note 4). The carrying values of the Company’s accounts receivable, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

Concentration of Credit Risk and Significant Suppliers

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist of cash, cash equivalents and marketable debt securities. The Company’s cash, cash equivalent and marketable securities balances are held by major financial institutions that management believes to be creditworthy. The Company uses multiple financial institutions to limit the amount of credit exposure to any one financial institution. Substantially all the Company’s cash, cash equivalent and marketable debt securities were invested in money market funds, U.S. Treasury bills, and U.S. government agency bonds at December 31, 2020 and 2019. At times, the Company’s cash deposits may exceed the amount of federal insurance provided on such deposits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company relies, and expects to continue to rely, on a small number of vendors to perform research activities that continue to progress its product candidates for its development programs. These programs could be adversely affected by a significant interruption in the related processes of these vendors.

Restricted Cash

Cash accounts with any type of restriction are considered restricted cash and are classified on the balance sheet based on the length of the restrictive obligation. As of both December 31, 2020 and 2019, the Company recorded restricted cash of $2.3 million, all of which was related to security deposits associated with the Company’s facility leases in Boston, Massachusetts and Cambridge, Massachusetts, and is recorded as long term in its balance sheet because the deposit is required for the duration of the lease which is greater than a year.

The reconciliation of cash and cash equivalents and restricted cash to amounts presented in the consolidated statements of cash flows are as follows:


	December 31,
	2020		2019
	(in thousands)
Cash and cash equivalents	$	28,381	$	22,889
Restricted cash		2,279		2,279

Cash, cash equivalents and restricted cash	$	30,660	$	25,168

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful lives of each asset.

Estimated useful lives are periodically assessed to determine if changes are appropriate. The estimated useful lives of the Company’s property and equipment are as follows:


Asset		Estimated useful life
Computer equipment		3 years
Computer software		5 years
Office equipment		5 years
Furniture and fixtures		7 years
Laboratory equipment		7 years
Leasehold improvements		Shorter of remaining lease term or 10 years

The Company reviews long-lived assets, such as property and equipment, for impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. If indicators of impairment are present, the assets are tested for recoverability by comparing the carrying amount of the assets to the related estimated future undiscounted cash flows that the assets are expected to generate. If the expected cash flows are less than the carrying value of the asset group, then the asset group is considered to be impaired and its carrying value is written down to fair value, based on the related estimated discounted future cash flows. To date, no such impairment losses have been recorded.

Costs for assets not yet placed into service are capitalized as

construction-in-progress

and depreciated or amortized in accordance with the above useful lives once placed into service. Upon retirement or sale, the related cost and accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in the consolidated statements of operations. Repairs and maintenance costs are expensed as incurred.

Operating Leases

The Company accounts for leases in accordance with ASC Topic 842,

Leases

, which it early adopted on January 1, 2018.

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on specific facts and circumstances and the existence of an identified asset(s), if any, and its control over the use of the identified asset(s), if applicable. Upon lease commencement, operating lease liabilities and their corresponding

right-of-use

assets are recorded on the balance sheet based at the present value of lease payments over the expected lease term. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Lease expense is recognized over the expected term on a straight-line basis.

Lease payments are discounted at the lease commencement date using the interest rate implicit in the lease contract. As this rate is typically not readily determinable, the Company determines an incremental borrowing rate that is used to discount lease payments, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. Certain prospective adjustments to the

right-of-use

asset may be required for items such as initial direct costs paid or incentives received.

The Company elected to account for lease and

non-lease

components as a single lease component, however

non-lease

components that are variable, such as common area maintenance and utilities, are generally paid separately from rent based on actual costs incurred and therefore are not included in the

right-of-use

asset and

operating lease liability and are reflected as an expense in the period incurred. The Company’s lease terms often include renewal options. The amounts determined for the Company’s

right-of-use

assets and lease liabilities generally do not assume that any renewal options or any early-termination provisions, if any, are exercised, unless it is reasonably certain that the Company will exercise such options.

Revenue Recognition

At contract inception, the Company assesses whether the collaboration arrangements are within the scope of ASC Topic 808, Collaborative Arrangements, or ASC 808, to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed based on the responsibilities of all parties in the arrangement. For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the arrangement are within the scope of ASC 808 and which elements are within the scope of ASC 606. For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, either by analogy to authoritative accounting literature or by applying a reasonable and rational policy election. To date, the Company has not entered into any arrangements within the scope of ASC 808.

The Company’s revenues are generated through its license and collaboration agreements with Gilead. Refer to Note 3, “Collaboration Agreements.”

Effective January 1, 2017, the Company early adopted ASC Topic 606,

Revenue from Contracts with Customers

(“ASC 606”), and related amendments using the retrospective transition method, which had no impact on the Company’s financial statements. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. ASC 606 provides a five-step framework whereby revenue is recognized when control of promised goods or services is transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) performance obligations are satisfied. The Company only applies this framework to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses whether the goods or services promised within each contract are distinct and, therefore, represent a separate performance obligation. Goods and services that are determined not to be distinct are combined with other promised goods and services until a distinct bundle is identified. The Company then allocates the transaction price (that is, the amount of consideration the Company expects to be entitled to from a customer in exchange for the promised goods or services) to each performance obligation and recognizes the associated revenue when (or as) each performance obligation is satisfied. The Company’s estimate of the transaction price for each contract includes all variable consideration to which the Company expects to be entitled, subject to the constraint on variable consideration. Variable consideration is not constrained if the potential reversal of cumulative revenue recognized at the contract level is not significant.

In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under active agreements, the Company must use its judgment to determine: (a) the number of performance

obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; (c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and (d) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to the identified performance obligations on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. In certain instances, the timing of satisfying these obligations can be difficult to estimate. Accordingly, the Company’s estimates may change in the future and those changes could be material. Such changes to estimates would result in a change in amounts of revenue recognized. If these estimates and judgments change over the course of these agreements, it may affect the timing and amount of revenue that the Company recognizes and records in future periods.

Amounts due to the Company for satisfying the revenue recognition criteria or that are contractually due based upon the terms of the collaboration agreements are recorded as accounts receivable in the Company’s consolidated balance sheet. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the one year following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the one year following the balance sheet date are classified as deferred revenue, net of current portion. Amounts recognized as revenue, but not yet received or invoiced are generally recognized as contract assets.

Exclusive License Rights

— If the license to the Company’s intellectual property is determined to be distinct from the other promises or performance obligations identified in the arrangement, which generally include research and development services, the Company recognizes revenue from

non-refundable,

upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a license is distinct from the other promises, the Company considers relevant facts and circumstances of each arrangement, including the research and development capabilities of the collaboration

partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promises, whether the value of the license is dependent on the unsatisfied promises, whether there are other vendors that could provide the remaining promises and whether it is separately identifiable from the remaining promises. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation and whether the license is the predominant promise within the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. If the license is the predominant promise, and it is determined that the license represents functional intellectual property (“IP”), revenue is recognized at the point in time when control of the license is transferred. If it is determined that the license does not represent functional IP, revenue is recognized over time using an appropriate method of measuring progress.

Research and Development Services

— The obligations under the Company’s collaboration agreements may include research and development services to be performed by the Company to benefit the collaboration partner. For performance obligations that include research and development services, the Company generally recognizes revenue allocated to such performance obligations based on an appropriate measure of progress. The Company utilizes judgment to determine the appropriate method of measuring progress for purposes of recognizing

revenue, which is generally an input measure such as costs incurred. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and thereby periods of which revenue should be recognized, are subject to estimates by management and may change over the course of the contract. Reimbursements from the partner that are the result of a collaborative relationship with the partner, instead of a customer relationship, such as

co-development

activities, are recorded as a reduction to research and development expense. No collaborative arrangements existed that would result in such reimbursements for the periods presented.

Customer Options

— The Company’s arrangements may provide a collaborator with the right to acquire additional goods or services in the future. Under these agreements, fees may be due to the Company (i) upon the exercise of the customer option or (ii) in equal installment payments over an agreed upon period. If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the additional goods and services underlying the customer options are evaluated in order to determine if these additional goods or services are distinct from those included as a performance obligation at the outset of the arrangement. If the additional services are not determined to be distinct, the variable consideration pertaining to the customer option is added to the initial transaction price at the time in which the option exercise becomes probable, so long as a potential for reversal of cumulative revenue recognized at the contract level is not significant. Any such adjustments to the transaction price are recorded on a cumulative

catch-up

basis, which would affect revenues and earnings in the period of adjustment. If the additional services are distinct, the Company evaluates the customer options for material rights, or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the inception of the arrangement. The Company allocates the transaction price to material rights based on the relative stand-alone selling price, which is determined based on the identified discount and the probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised or expires.

Milestone Payments

— At the inception of an arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative

catch-up

basis, which would affect revenues and earnings in the period of adjustment. If a milestone or other variable consideration relates specifically to the Company’s efforts to satisfy a single performance obligation or to a specific outcome from satisfying the performance obligation, the Company generally allocates the milestone amount entirely to that performance obligation once it is probable that a significant revenue reversal would not occur.

Royalties

— For arrangements that include sales-based royalties, including milestone payments based on a level of sales, where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to

which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from licensing agreements.

Research and Development Expenses

Research and development expenses include costs directly attributable to the conduct of research programs, including the cost of salaries, employee benefits, stock-based compensation expense, materials, supplies, depreciation on and maintenance of research equipment, the cost of services provided by outside contractors to conduct research and development activities and the allocable portions of facility costs, such as rent, utilities, and general support services. All costs incurred to fulfill the Company’s obligations under the collaboration with Gilead are classified as research and development expenses. All costs associated with research and development are expensed as incurred.

Management estimates the Company’s accrued research and development expenses as of each balance sheet date in the Company’s financial statements based on facts and circumstances known to the Company at that time. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Nonrefundable advance payments for goods and services are deferred and recognized as expense in the period that the related goods are consumed or services are performed.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock-Based Compensation

The Company measures the cost of employee services received in exchange for stock-based awards based on the grant-date fair value of the awards. The Company calculates the fair value of restricted stock awards based on the grant date fair value of the underlying common stock. The Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period of the awards for service-based awards, which is generally the vesting period. The Company recognizes stock-based compensation for performance-based awards when the underlying performance conditions are considered probable of occurrence and recognizes the cumulative effect of current and prior period changes in the period of change. The Company also has the right and option to repurchase an individual’s shares of common stock or vested stock options to acquire common stock subsequent to employment termination.

The fair value of common stock underlying stock-based awards is based on an estimate at each grant date. The valuation provided by the board of directors is derived from a recommendation by an unrelated third-party valuation firm. The Company determines the estimated per share fair value of its common stock at various dates considering contemporaneous and retrospective valuations that incorporate objective and subjective factors, including actual and forecasted financial results, market conditions and performance of comparable publicly traded companies, developments and milestones of the Company, the rights and preferences of common and redeemable convertible preferred stock, advice from the third-party valuation specialists, and transactions involving the Company’s stock. The estimated per share fair value of the Company’s common stock is determined in accordance with the guidance outlined in the American Institute of Certified Public Accountants

Practice Aid,

Valuation of Privately-Held Company Equity Securities Issued as Compensation

. The fair value of each restricted common stock award is estimated on the date of grant based on the fair value of the Company’s common stock on that same date. The fair value of each stock option grant is determined using assumptions discussed below.

Expected Term

: The expected term of the stock options is estimated using the “simplified method,” as prescribed in SEC’s Staff Accounting Bulletin (SAB) No. 107, as the Company has no historical information from which to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. The simplified method is the midpoint between the vesting period and the contractual term of the option.

Expected Volatility

: Since there is limited historical data for the Company’s common stock and limited company-specific historical volatility, the Company has determined the share price volatility for options granted based on an analysis of the volatility used by a peer group of publicly traded companies. In evaluating similarity, the Company considers factors such as industry, stage of life cycle and size.

Risk-free Interest Rate

: The risk-free rate is based on the U.S. Treasury yield curve commensurate with the expected life of the option.

Dividend Rate

: The expected dividend was assumed to be zero as the Company has never paid dividends and has no current plans to do so.

The assumptions used in estimating the fair value of stock-based awards represent management’s estimate and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards.

Stock-based compensation is classified in the accompanying consolidated statements of operations and comprehensive loss based on the function to which the related services are provided. Forfeitures are accounted for as they occur. Any consideration paid by employees on exercising stock options and the corresponding portion previously credited to additional

paid-in

capital are credited to share capital.

Classification of Convertible Preferred shares

The Company’s convertible preferred shares are classified outside of stockholders’ deficit because the holders of such shares have liquidation rights in the event of a deemed liquidation that, in certain situations, are not solely within the control of the Company. Further, the Company’s convertible preferred shares are redeemable at the option of the holder after March 2023. The Company records convertible preferred shares at fair value upon issuance, net of any issuance costs or discounts.

Share Issuance Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with

in-process

equity financings as deferred offering costs until such financings are consummated. After consummation of an equity financing, these costs are recorded as a reduction of the proceeds from the offering, either as a reduction to the carrying value of the preferred exchangeable shares or convertible preferred

shares or in shareholders’ equity (deficit) as a reduction of additional

paid-in

capital generated as a result of the offering. Should an

in-process

equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. As of December 31, 2020 and 2019, the Company had no deferred offering costs.

Income Taxes

The Company accounts for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are exp

cted to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period corresponding to the enactment date. A valuation allowance is established when it is more likely than not that all or some portion of the deferred tax assets will not be realized through generating sufficient future taxable income.

The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not such tax position will be sustained on examination by the taxing authorities, based solely on the technical merits of the respective tax position. The tax benefits recognized in the financial statements from such a tax position should be measured based on the largest benefit having a more likely than not likelihood of being realized upon ultimate settlement with the tax authority. The recognition and measurement of tax benefits requires significant judgments that are subject to change as new information becomes available.

Penalties and interest expense related to income taxes are included as components of income tax expense and interest expense, respectively, as necessary.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive loss for the years ended December 31, 2020 and 2019 was unrealized gains on investments in marketable securities.

Net Loss Per Share

Basic net loss per share attributable to common stockholders is computed by dividing net loss by the weighted-average number of shares of common shares outstanding during each reporting period. The weighted-average number of shares of common stock outstanding used in the basic net loss per share calculation does not include unvested restricted stock awards as these instruments are considered contingently issuable shares until they vest. Diluted net loss per share attributable to common stockholders includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock and stock options, which would result in the issuance of incremental shares of common stock. For diluted net loss per share, the weighted-average number of shares of common stock is the same for basic net loss per share due to the fact that when a net

loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive. The Company’s convertible preferred stock and unvested restricted stock entitles the holder to participate in dividends and earnings of the Company, and, if the Company were to recognize net income, it would apply the

two-class

method to calculate earnings per share. The

two-class

method is not applicable during periods with a net loss, as the holders of the convertible preferred stock and unvested restricted stock have no obligation to fund losses.

The

two-class

method of computing net loss per share would be applicable in a reporting period that resulted in a net income position, as the Company has issued shares that meet the definition of participating securities. The

two-class

method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The

two-class

method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Commitments and Contingencies

Liabilities for loss contingencies arising from claims, assessments, litigation, fines and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred.

Subsequent Events

The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.

Emerging Growth Company Status (Unaudited)

The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act (“JOBS Act”), and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. Section 107 of the JOBS Act provides that an emerging growth company can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, its consolidated financial statements may not be comparable to companies that comply with public company effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of an initial public offering or such earlier time that it is no longer an emerging growth company. However, the Company has not yet delayed the adoption of any new accounting standards.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU

2016-13

, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments

. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For

available-for-sale

debt securities, entities are required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities are no longer permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. For public entities, the guidance was effective for annual reporting periods beginning after December 15, 2019 and for interim periods within those fiscal years. Early adoption was permitted. The Company early adopted this standard as of January 1, 2020 on a prospective basis. The adoption did not have a material impact on the Company’s consolidated financial statements.

In August 2018, the FASB issued ASU

2018-13,

Changes to the Disclosure Requirements for Fair Value Measurement

. The amendments become effective for the Company’s fiscal year beginning January 1, 2020. Early adoption of the amendments in full or only the provisions that eliminate or modify the disclosure requirements for fair value measurements is permitted. Adoption of this standard on January 1, 2020 did not have a material impact on the Company’s consolidated financial statements and related disclosures.

In August 2018, the FASB issued ASU

2018-15,

Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract

. The new standard requires a customer in a cloud computing arrangement to determine which implementation costs to capitalize as assets or expense as incurred. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. The new standard became effective for the Company’s fiscal year beginning January 1, 2020. Early adoption was permitted. The early adoption of this standard on January 1, 2020 did not have a material impact on the Company’s consolidated financial statements and related disclosures.

Recently Issued Accounting Pronouncements

In December 2019, the FASB issued ASU

2019-12,

Simplifying the Accounting for Income Taxes,

(“ASC 740”). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis

step-up

in goodwill obtained in a transaction

that is not a business combination, separate financial statements of entities not subject to tax, the intra-period tax allocation exception to the incremental approach, ownership changes in investments, changes from a subsidiary to an equity method investment, interim-period accounting for enacted changes in tax law, and the

year-to-date

loss limitation in interim-period tax accounting. This guidance is effective for the Company for annual and interim periods beginning after December 31, 2020; however, early adoption is permitted. The adoption is not expected to have a material impact on the Company’s consolidated financial statements.

In August 2020, the FASB issued ASU

2020-06,

Debt

— Debt with Conversion and Other Options (Subtopic

470-20)

and Derivatives and Hedging

— Contracts in Entity’s Own Equity (Subtopic 815

— 40)

. The amendments in this update affect entities that issue convertible instruments and/or contracts indexed to and potentially settled in an entity’s own equity. The new ASU eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, the new guidance modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. The Company elected to early adopt this guidance on January 1, 2021. Adoption of the ASU

2020-06

guidance as of January 1, 2021 has no impact on its consolidated financial statements for the year ended December 31, 2020.

The Company issued the second tranche of its redeemable convertible Series B preferred stock in March 2021 at an original issue price of $1.32 per share, which would have resulted in the recognition of a beneficial conversion feature of $28.4 million prior to the adoption of ASU

2020-06.

As such, the adoption of this guidance is expected to have a material impact on the Company’s financial statements for the year ending December 31, 2021.

From time to time, new account pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements.

Collaboration Agreements

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Collaboration Agreements [Abstract]

Collaboration Agreements

3. Collaboration Agreements

2018 Gilead Agreement

In October 2018, the Company entered into a Research Collaboration and License Agreement (the “2018 Gilead Agreement”) with Gilead Sciences, Inc. (“Gilead”). Pursuant to the 2018 Gilead Agreement, the Company performed target discovery and validation activities in accordance with an agreed-upon multi-year research plan. During the initial three-year research term, Gilead had the option to obtain exclusive, worldwide licenses to develop and commercialize up to five validated programs (“Gilead Program License”).

In 2018, Gilead paid the Company a $50.0 million

non-refundable

upfront payment upon the execution of the 2018 Gilead Agreement. The Company was eligible to receive milestone payments of up to $1.7 billion across all programs and royalties on future sales of commercialized products, if any. For up to two programs licensed by Gilead, the Company had the option to

co-develop

and

co-promote

certain programs licensed by Gilead in the U.S. and was eligible to receive royalties on

ex-U.S.

sales.

The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Gilead, was a customer. The Company identified a single performance obligation under the arrangement consisting of the combination of participating on the joint steering committee and the research and development services provided during the research term. The identified promises were determined to not be individually distinct due to the specialized nature of the early-stage research services to be provided by the Company and the interdependent relationship between the promises. The Company determined that the option for Gilead to extend the term of the arrangement was not priced at a discount, and therefore did not provide Gilead with a material right. This option will be excluded from the transaction price until exercised. At the inception of the 2018 Gilead Agreement, the Company also determined that the Gilead program license options provided to Gilead did not include a material right.

The total transaction price, subject to variable consideration constraints, was allocated to the combined single performance obligation. The Company determined that the single combined performance obligation is satisfied over time as the customer is simultaneously receiving and consuming the benefit of the Company’s performance. The future milestone payments represent variable consideration that is fully constrained at inception of the arrangement as the achievement of the milestone events are highly uncertain.

Amended Gilead Agreement

In August 2020, Gilead made an equity investment of $20.0 million into the Company as a participant in the Company’s Series

B-1

preferred stock offering. At the time of the original investment, as well as of the December 31, 2020 balance sheet date, Gilead maintains an ownership of less than 10% of the Company and is thus not considered to be a related party to the Company.

In August 2020, the Company and Gilead also entered into an Amended Research Collaboration and License Agreement (the “Gilead Agreement”), which superseded and replaced the 2018 Gilead agreement. The Gilead Agreement represents a continuation of the initial target discovery and validation research and development efforts begun under the 2018 Gilead Agreement. Under the Gilead Agreement:

•

The Company received upfront,

non-refundable

consideration of $

125.0

million from Gilead upon execution of the Gilead Agreement in 2020;

•

The term of the 2018 Gilead Agreement ended on the date the Gilead Agreement was executed. The Gilead Agreement has a research term of seven years;

•

Gilead expanded its option to license up to 15 programs for which Gilead may obtain exclusive, worldwide licenses to develop and commercialize therapies, subject to applicable license fees;

•

Prior to exercising its option to license a program, Gilead may “extend” such program, in which case Gilead will pay research extension fees and the Company will continue to collaborate with Gilead to discover and develop programs, potentially through early clinical development.

•

For up to five programs licensed by Gilead, the Company has the option to

co-develop

and

co-promote

the lead product in the U.S., subject to certain exceptions, and is eligible to receive tiered royalties in the first decile on

ex-U.S.

sales.

The Company is eligible to receive up to $410.0 million per program in license, research extension, and clinical, regulatory, and commercial milestones.

The Gilead Agreement was accounted for as a modification of the 2018 Gilead Agreement under ASC 606 as both the scope and price of the contract were changed under the Gilead Agreement. The additional goods and services to be provided under the Gilead Agreement are not distinct from the combined performance obligation identified under the 2018 Gilead Agreement which was only partially satisfied at the date of contract modification. As such, the Company identified a single combined performance obligation under the Gilead Agreement consisting of the research services and continued participation on the joint steering committee during the research term. As a result, the Company’s progress towards completing its research services to Gilead over the seven-year term of the Amended Gilead Agreement was lower than its progress under the three-year term of the 2018 Gilead Agreement and a cumulative

catch-up

adjustment was recorded during the third quarter of 2020 resulting in a reduction of $11.3 million of revenue previously recognized through the date of the Gilead Agreement.

In December 2020, Gilead elected to extend a program for a research extension fee of $12.0 million. The Company determined that the additional goods and services relating to the continued research services were not distinct from the early-stage research services already promised to Gilead under the

on-going

research plan. Consideration pertaining to the research extension is paid to the Company in equal quarterly installment payments over an agreed upon payment schedule. Although future research installment payments are not payable in the event of scientific failure, the Company determined that the variable consideration of $12.0 million should not be constrained as the potential for a significant reversal of cumulative revenue recognized at the contract level is remote, and therefore the research extension consideration was added to the transaction price under the Gilead Agreement.

In April 2021, Gilead licensed a program for a $11.0 million fee. The $11.0 million license fee was received and recognized as revenue in the second quarter of 2021 since Tango has no continued involvement in the advancement of the program, Gilead can benefit from the license on its own and the license is separately identifiable from the research services.

Gilead Revenue Recognized

The total transaction price allocated to the combined performance obligation under the Gilead Agreement was $187.0 million at June 30, 2021. The total transaction price was comprised of the $50.0 million upfront payment

pursuant to the 2018 Gilead Agreement, the $125.0 million upfront payment pursuant to the Gilead Agreement, and the $12.0 million pursuant to the research extension fee in December 2020. During the three and six months ended June 30, 2021, the Company recognized $7.2 million and $13.5 million, respectively, and during the three and six months ended June 30, 2020, the Company recognized $4.7 million and $9.1 million, respectively, of revenue associated with the Gilead Agreements based on performance completed during each period. During the three and six months ended June 30, 2021, the Company recognized revenue of $11.0 million, associated with the payments received in the second quarter of 2021 pursuant to the April 2021 program license. During the three and six months ended June 30, 2020, the Company recognized revenue of $0.3 million and $0.7 million, respectively, associated with the payments rec

ived in 2019 pursuant to the program license and Gilead Letter Agreement. The consideration allocated to the Gilead License was recognized upon delivery of the underlying license in 2019 as Gilead could benefit from the license on its own and the Gilead License was separately identifiable from the Gilead Letter Agreement research services.

The Company reevaluates the transaction price and the total estimated costs expected to be incurred to satisfy the performance obligations at the end of each reporting period and as uncertain events, such as changes to the expected timing and cost of certain research and development activities that the Company is responsible for, are resolved or other changes in circumstances occur. As of June 30, 2021 and December 31, 2020, the Company had short-term deferred revenue of $24.5 million and $32.0 million, respectively, and long-term deferred revenue of $118.7 million and $120.8 million, respectively, related to the Gilead collaboration. The remaining long-term revenue is expected to be recognized proportionally to the completed obligations over an expected remaining contractual term of approximately 6.1 years.

As of June 30, 2021, $4.0 million of the total research extension fee amount of $12.0 million had been received, $2.0 million had been recorded as accounts receivable and the remaining $6.0 million was determined to be conditional upon the satisfaction of additional research obligations, and thus a contract asset.

The contract asset balance is presented net of the deferred revenue contract liability.

Costs incurred pursuant to the Gilead Agreements are recorded as research and development expense.

3. Collaboration Agreements

2018 Gilead Agreement

In October 2018, the Company entered into a Research Collaboration and License Agreement (the “2018 Gilead Agreement”) with Gilead Sciences, Inc. (“Gilead”). Pursuant to the 2018 Gilead Agreement, the Company performed target discovery and validation activities in accordance with an agreed-upon a multi-year research plan. During the initial three-year research term, Gilead had the option to obtain exclusive, worldwide licenses to develop and commercialize up to five validated programs (“Gilead Program License”).

In 2018, Gilead paid the Company a $50.0 million

non-refundable

upfront payment upon the execution of the 2018 Gilead Agreement. The Company was eligible to receive milestone payments of up to $1.7 billion across all programs and up to low double-digit tiered percentage royalties on future sales of commercialized products, if any. For up to two programs licensed by Gilead, the Company had the option to

co-develop

and

co-promote

certain programs licensed by Gilead in the U.S. and was eligible to receive milestone payments and royalties on

ex-U.S.

sales.

The Company determined that the transaction price at the inception of the arrangement was equal to the total upfront payment received in the aggregate amount of $50.0 million. The total transaction price, subject to variable consideration constraints, was allocated to the combined single performance obligation. The Company determined that the single combined performance obligation is satisfied over time as the customer is simultaneously receiving and consuming the benefit of the Company’s performance. The future milestone payments represent variable consideration that is fully constrained at inception of the arrangement as the achievement of the milestone events are highly uncertain.

In May 2019, Gilead licensed (the “Gilead License”) its first program under the 2018 Gilead Agreement and paid the Company a $7.5 million license fee. Gilead obtained a license to develop and commercialize therapies

associated with the nominated program. At the inception of the 2018 Gilead Agreement, the Company determined that the licenses provided to Gilead through the 2018 Gilead Agreement did not include a material right as the license fees were not priced at a discount. At the time of the exercise of the license option by Gilead for the specified nominated program, the Company’s obligations for the nominated program were completed. As such, the Gilead license of the nominated program was determined to be distinct and accounted for as a separate contract.

In July 2019

, the Company and Gilead also entered into a letter agreement (the “Gilead Letter Agreement”) whereby the Company would perform additional research services on behalf of Gilead associated with the first program licensed und

r the 2018 Gilead Agreement. Upon execution of the Gilead Letter Agreement, Gilead made a $2.6 million payment to the Company as consideration for the performance of additional research services as stipulated in the Gilead Letter Agreement. The Company concluded that the Gilead Letter Agreement should be combined with the Gilead License and accounted for as a single contract. The Company determined that the Gilead License and the research services included in the Gilead Letter Agreement were each distinct as Gilead could benefit from the Gilead License without receiving the additional research services from the Company. As such, the Company allocated the transaction price for the combined agreement between the two distinct performance obligations in proportion to their relative standalone selling prices.

Amended Gilead Agreement

In August 2020, Gilead made an equity investment of $20.0 million into the Company as a participant in the Company’s Series

B-1

•

The Company received upfront,

non-refundable

consideration of $125.0 million from Gilead upon execution of the Gilead Agreement in 2020;

•

The term of the 2018 Gilead Agreement ended on the date the Gilead Agreement was executed. The Gilead Agreement has a research term of seven years;

•

Gilead expanded its option to license up to 15 programs for which Gilead may obtain exclusive, worldwide licenses to develop and commercialize therapies, subject to applicable license fees;

•

For up to five programs licensed by Gilead, the Company has the option to

co-develop

and

co-promote

the lead product in the U.S., subject to certain exceptions, and eligible to receive milestone payments and royalties on

ex-U.S.

sales.

The Company is eligible to receive up to $410.0 million per program in license, research extension, and clinical, regulatory, and commercial milestones. The Company is also eligible to receive up to low double-digit tiered royalties on net sales by Gilead, if any, on a

country-by-country

and

product-by-product

basis until the later of (a) the expiration of the last valid claim of the Company’s patents or, in some instances, certain Gilead patents, in

each case, covering such product in such country or (b) ten years after the first commercial sale of such product in such country. For those programs the Company

co-develops

and

co-promotes

in the U.S., the Company and Gilead would share equally in the development costs as well as the profits and losses in the U.S. For such products, the Company remains eligible to receive certain clinical and regulatory milestone payments as well as commercial milestone payments and up to low double-digit tiered royalties based on net sales outside the U.S.

catch-up

adjustment was recorded during the third quarter of 2020 resulting in a reduction of $11.3 million of revenue previously recognized through the date of the Gilead Agreement.

on-going

price

under the Gilead Agreement.

Gilead Revenue Recognized

The total transaction price allocated to the combined performance obligation under the Gilead Agreement was $187.0 million at December 31, 2020. The total transaction price was comprised of the $50.0 million upfront payment pursuant to the 2018 Gilead Agreement, the $125.0 million upfront payment pursuant to the Gilead Agreement, and the $12.0 million pursuant to the research extension fee in December 2020. During the years ended December 31, 2020 and 2019, the Company recognized $7.0 million and $15.2 million, respectively, of revenue associated with the Gilead Agreements based on performance completed during each period. During the years ended December 31, 2020 and 2019, the Company recognized revenue of $0.7 million and $9.4 million, respectively, associated with the payments received in 2019 pursuant to the program license and Gilead Letter Agreement. The consideration allocated to the Gilead License was recognized upon delivery of the underlying license in 2019 as Gilead could benefit from the license on its own and the Gilead License was separately identifiable from the Gilead Letter Agreement research services.

$120.8 million and $14.1 million, respectively, related to the Gilead collaboration. Of the total short-term deferred revenue at December 31, 2019, $18.6 million related to the 2018 Gilead Agreement and the other $1.0 million related to the Gilead Letter Agreement.

Amounts due to the Company that have not yet been received are recorded as accounts receivable and amounts received that have not yet been recognized as revenue are recorded as deferred revenue on the Company’s consolidated balance sheet. As of December 31, 2020, $2.0 million of the total research extension fee amount of $12.0 million had been recorded as accounts receivable and the remaining $10.0 million was determined to be conditional upon the satisfaction of additional research obligations, and thus a contract asset. The contract asset balance is presented net of the deferred revenue contract liability.

Costs incurred pursuant to the Gilead Agreements are recorded as research and development expense.

Fair Value Measurements

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	Fair Market Value Measurements as of June 30, 2021
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	30,440	$	—	$	—	$	30,440
U.S. Treasury bills		—		—		—		—
Marketable debt securities:
U.S. Treasury bills		—		126,953		—		132,953
U.S. government agency bonds		—		20,499		—		20,499

Total assets	$	30,440	$	147,452	$	—		177,892


	Fair Market Value Measurements as of December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents
Money market funds	$	12,698	$	—	$	—	$	12,698
U.S. Treasury bills		—		7,175		—		7,175
Marketable debt securities
U.S. Treasury bills		—		131,939		—		131,939
U.S. government agency bonds		—		30,000		—		30,000

Total assets	$	12,698	$	169,114	$	—	$	181,812

There were no transfers between fair value levels during the six months ended June 30, 2021.

4. Fair Value Measurements

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	Fair Market Value Measurements as of December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents
Money market funds	$	12,698	$	—	$	—	$	12,698
U.S. Treasury bills		—		7,175		—		7,175
Marketable debt securities
U.S. Treasury bills		—		131,939		—		131,939
U.S. government agency bonds		—		30,000		—		30,000

Total assets	$	12,698	$	169,114	$	—	$	181,812


	Fair Market Value Measurements as of December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	18,508	$	—	$	—	$	18,508
Marketable debt securities:
U.S. Treasury bills		—		17,536		—		17,536

Total assets	$	18,508	$	17,536	$	—	$	36,044

There were no transfers between f

air v

alue levels during the years ended December 31, 2020 and 2019.

Marketable Securities

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

5. Marketable Securities

rvable transactions. At each balance sheet date, observable market inputs may include trade information, broker or dealer quotes, bids, offers or a combination of these data sources.

The following table summarizes the Company’s marketable debt securities, classified as

available-for-sale:


	Fair Value Measurements as of June 30, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss			Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	126,954	$	5	$	(6	)	$	126,953
U.S. government agency bonds		20,496		9		(6	)		20,499

	$	147,450	$	14	$	(12	)	$	147,452


	Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	131,927	$	12	$	—	$	131,939
U.S. government agency bonds		29,995		5		—		30,000

	$	161,922	$	17	$	—	$	161,939

The Company holds investment grade marketable securities, and none were considered to be in an unrealized loss position as of June 30, 2021 and December 31, 2020. As a result, the Company did not record any reserves for credit losses related to its marketable debt securities during the periods then ended. Marketable securities include $0.1 million in accrued interest at June 30, 2021 and December 31, 2020.

5. Marketable Securities

The Company values its marketable securities using independent pricing services which normally derive security prices from recently reported trades for identical or similar securities, making adjustments based on significant observable transactions. At each balance sheet date, observable market inputs may include trade information, broker or dealer quotes, bids, offers or a combination of these data sources.

The following table summarizes the Company

’s m

arketable debt securities, classified as

available-for-sale:


	Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	131,927	$	12	$	—	$	131,939
U.S. government agency bonds		29,995		5		—		30,000

	$	161,922	$	17	$	—	$	161,939


	Fair Value Measurements as of December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	17,526	$	10	$	—	$	17,536

	$	17,526	$	10	$	—	$	17,536

The Company holds investment grade marketable securities, and none were considered to be in an unrealized

loss

position as of December 31, 2020 and 2019. As a result, the Company did not record any reserves for credit losses related to its marketable debt securities during the years then ended. Marketable securities include $0.1 million in accrued interest for each of the years ended December 31, 2020 and December 31, 2019.

Supplemental Balance Sheet Information

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Supplemental Balance Sheet Information

6. Supplemental Balance Sheet Information

Property and Equipment

Property and equipment, net as of June 30, 2021 and December 31, 2020 consists of the following:


	June 30, 2021			December 31, 2020
	(in thousands)
Laboratory equipment	$	5,337		$	4,580
Computer equipment		172			172
Computer software		125			125
Furniture and fixtures		459			384
Leasehold improvements		246			246
Construction in process		158			—

		6,497			5,507
Less: Accumulated depreciation		(2,100	)		(1,684	)

Property and equipment, net	$	4,397		$	3,823

Depreciation expense was $0.2 million for each of the three months ended June 30, 2021 and 2020 and $0.4 million and $0.3 million for the six months ended June 30, 2021 and 2020, respectively.

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 include the following:


	June 30, 2021		December 31, 2020
	(in thousands)
Payroll and employee-related costs	$	2,046	$	2,652
Research and development costs		3,691		2,695
Other		697		793

Total accrued expenses and other current liabilities	$	6,434	$	6,140

Restricted Cash

As of both June 30, 2021 and June 30, 2020, the Company maintained a restricted cash balance of $2.3 million, all of which was related to security deposits associated with the Company’s facility leases. The cash will remain restricted in accordance with the lease agreements absent the event of a lease termination of modification. The reconciliation of cash and cash equivalents and restricted cash to amounts presented in the condensed consolidated statements of cash flows are as follows:


	June 30, 2021		June 30, 2020
	(in thousands)
Cash and cash equivalents	$	50,902	$	13,118
Restricted cash		2,279		2,279

Cash, cash equivalents and restricted cash	$	53,181	$	15,397

6. Supplemental Balance Sheet Information

Property and Equipment

Property and equipment, net as of December 31, 2020 and 2019 consists of the following:


	December 31,
	2020			2019
	(in thousands)
Laboratory equipment	$	4,580		$	3,823
Computer equipment		172			172
Computer software		125			9
Furniture and fixtures		384			246
Leasehold improvements		246			230

		5,507			4,480

Less: Accumulated depreciation		(1,684	)		(1,038	)

Property and equipment, net	$	3,823		$	3,442

Depreciation expense was $0.7 million and $0.6 million for the years ended December 31, 2020 and 2019, respectively.

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of December 31, 2020 and 2019 include the following:


	December 31,
	2020		2019
	(in thousands)
Payroll and employee-related costs	$	2,652	$	1,830
Research and development costs		2,695		2,764
Other		793		338

Total accrued expenses and other current liabilities	$	6,140	$	4,932

Leases

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Leases

7. Leases

Operating Leases

In July 2017, the Company entered into a lease of office and laboratory space at 100 Binney Street in Cambridge, Massachusetts for the Company’s corporate headquarters. The lease commenced in March 2018 and rent commenced in June 2018. This lease has a

non-cancelable

term of eight years with an option to extend for one additional three-year period.

Upon commencement of the lease, the Company recorded an operating lease liability in the amount of $9.5 million and related operating lease

right-of-use

asset in the amount of $9.8 million. Upfront payments totaling $0.3 million for rent and tenant improvements were included as a reduction in the calculation of the lease liability amount upon the commencement of the lease. There were no tenant obligation payments made for leasehold improvements for the periods ended December 31, 2020 and 2019. The fixed annual rent payable under the lease is $1.7 million, increasing by 3% annually from the rent commencement date. The minimum rent payments to be paid over the

non-cancelable

term of this lease totaled $15.6 million. The additional rental payments associated with the renewal option are not included in the calculation of the operating lease

right-of-use

asset and associated operating lease liability as the renewal is not considered probable of occurring. The lease agreement required the Company to provide a letter of credit for $0.6 million that is collateralized with cash that is recorded as restricted cash in the accompanying balance sheet.

In September 2019, the Company entered into a new lease for office and laboratory space at 201 Brookline Avenue in Boston, Massachusetts. As of December 31, 2020, the space was undergoing construction and the lease is expected to commence in 2022. The Company is not deemed to be the accounting owner of the construction project due to the nature of the work being performed and the Company’s lack of control over the project. In conjunction with executing the lease, the Company provided the landlord a letter of credit for $1.7 million. The letter of credit is collateralized with cash that is recorded as restricted cash in the accompanying balance sheet as of December 31, 2020. Upon delivery date notice of the lease, which is estimated to occur in the second half of 2021, the Company will be required to provide an additional letter of credit in the amount of $1.7 million.

Upon commencement of the 201 Brookline Avenue lease, the Company will determine the appropriate classification of the lease, the amount of the associated lease liability and the amount of the

right-of-use

asset that will be recognized on the balance sheet. The lease has a

non-cancelable

term of ten years with an option to extend for up to two five-year periods. The fixed annual rent payable under the lease is $5.1 million, increasing

annually from the rent commencement date. The Company is entitled to a tenant improvements allowance of up

to $

12.7

million.

The Company’s rent payments for the lease at 100 Binney Street are classified as operating lease costs in the chart below. The lease is a net lease and therefore the

non-lease

components, such as common area maint

nance, are paid separately from rent based on actual costs incurred; therefore, the

non-lease

components are not included in the

right-of-use

asset and liability and are reflected as an expense in the period incurred. The

non-lease

components are classified as variable costs in the chart below. As of December 31, 2020 and 2019, assets under the operating lease totaled $7.5 million and $8.4 million, respectively. The elements of lease cost were as follows:


	Year Ended December 31,
Operating leases	2020			2019
Operating lease cost	$	1,889		$	1,889
Short-term lease cost		93			36
Variable lease cost		643			541

Total operating lease costs	$	2,625		$	2,466


Other information	December 31, 2020			December 31, 2019
Operating cash flows used for operating leases	$	1,782		$	1,735
Weighted average remaining lease term in years		5.5			6.5
Weighted average discount rate		12	%		12	%

Future minimum lease payments under

non-cancelable

leases that have commenced as of December 31, 2020 are as follows:


Year Ended December 31,	Maturity of Lease Liabilities
2021	$	1,836
2022		1,891
2023		1,948
2024		2,007
2025		2,067
Thereafter		1,046

Total lease payments		10,795
Less: imputed interest		(2,911	)

Total operating lease liabilities	$	7,884

Commitments and Contingencies	6 Months Ended	12 Months Ended
Commitments and Contingencies	Jun. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Research Collaboration Agreement In September 2017, the Company entered into a Research Collaboration Agreement (the “HitGen Agreement”) with HitGen Ltd (“HitGen”). Under the terms of the HitGen Agreement, HitGen would use its DNA-encoded library technology to screen up to three targets and deliver to the Company the structures of certain compounds that bind to the targets. The Company would provide certain materials containing each target for purposes of the screen. The Company could have been obligated to make certain milestone payments. The Company and HitGen mutually agreed to terminate the HitGen Agreement in March 2021. No milestones were achieved or paid upon the termination of the agreement. Guarantees The Company enters into certain agreements with other parties in the ordinary course of business that contain indemnification provisions. These typically include agreements with directors and officers, business partners, contractors, landlords and clinical sites. Under these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of the Company’s activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification provisions is unlimited. However, to date the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these obligations is minimal. Litigation The company, from time to time, may be party to litigation arising in the ordinary course of business. The company was not subject to any material legal proceedings as of June 30, 2021, and no material legal proceedings are currently pending or threatened.	8. Commitments and Contingencies Research Collaboration Agreement In September 2017, the Company ent e red into a Research Collaboration Agreement (the “HitGen Agreement”) with HitGen Ltd (“HitGen”). Under the terms of the HitGen Agreement, HitGen would use its DNA-encoded library technology to screen up to three targets and deliver to the Company the structures of certain compounds that bind to the targets. The Company would provide certain materials containing each target for purposes of the screen. The Company could have been obligated to make certain milestone payments. The Company and HitGen have mutually agreed to terminate the HitGen Agreement in March 2021. No milestones were achieved or owed upon the termination of the agreement and the Company is under no obligation to make any payments upon termination of the HitGen Agreement. License Agreement In March 2020, the Company entered into a License Agreement (the “Medivir Agreement”) with Medivir AB (“Medivir”), pursuant to which the Company obtained an exclusive license to all patents, know-how and other intellectual property associated with a preclinical-stage research program. Pursuant to the Medivir Agreement, the Company made an upfront payment of $0.4 million. Under the terms of the Medivir Agreement, the Company is obligated to pay Medivir in connection with development, regulatory and commercial activities. The Company has agreed to make certain milestone payments of $1.4 million in the aggregate for the first licensed product that achieves specified clinical milestones, plus $25.0 million for the first licensed product that achieves specified regulatory approval and sales milestones, in each case, in either of the first two specified genetic contexts and $0.7 million in the aggregate if that first licensed product achieves specified clinical milestones, plus $5.0 million if that first licensed product achieves specified regulatory and sales milestones for a third genetic context or the second licensed product achieves such specified development, regulatory and sales milestones in either of the first two specified genetic contexts. The Company has the right to reduce these milestone payments by a specified amount in the event the licensed product is not covered by Medivir’s patents or if payments are due to a third party for a license under such third party’s intellectual property rights. The Company is also obligated to pay Medivir a low single-digit royalty on net sales of any product covered by a licensed patent. The Medivir Agreement expires on the date of expiration of all royalty obligations. Either party may terminate the Medivir Agreement earlier upon an uncured material breach of the other party. Upfront fees paid pursuant to the Medivir License Agreement were recorded to research and development expense. No milestones have been achieved to date. Guarantees The Company enters into certain agreements with other parties in the ordinary course of business that contain indemnification provisions. These typically include agreements with directors and officers, business partners, contractors, landlords and clinical sites. Under these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of the Company’s activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification provisions is unlimited. However, to date the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these obligations is minimal. Litigation The company, from time to time, may be party to litigation arising in the ordinary course of business. The company was not subject to any material legal proceedings as of December 31, 2020, and no material legal proceedings are currently pending or threatened.

Redeemable Convertible Preferred Stock

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Stockholders' Equity Note [Abstract]

Redeemable Convertible Preferred Stock

8. Redeemable Convertible Preferred Stock

In March 2017, the Company executed a stock purchase agreement to sell 55,000,000 shares of redeemable convertible series A preferred stock (“Series A”). This agreement was subsequently amended in July 2017 to increase the authorized capital to 55,700,000 shares of Series A. The Series A stock purchase agreement was structured to close in three tranches, each contingent upon the achievement of certain specified milestones.

Pursuant to the initial closing of the Series A stock purchase agreement, the Company issued an aggregate of 18,700,000 shares of Series A convertible preferred stock for $1.00 per share, resulting in net proceeds of $14.0 million after deducting $4.7 million related to the settlement of the convertible notes and accrued interest that were previously outstanding. During the year-ended December 31, 2018, the Company issued 26,000,000 additional shares of Series A preferred stock at a price of $1.00 per share upon the achievement of specified development milestones in connection with the second tranche of the Series A stock purchase agreement. Total proceeds from this issuance was $26.0 million. In January 2019, the Company issued 11,000,000 additional shares of Series A preferred stock at a price of $1.00 per share upon the achievement of specified development milestones in connection with the third tranche of the Series A stock purchase agreement. Total proceeds from this issuance was $11.0 million. The aggregate issuance costs associated with the issuance of all three tranches of Series A preferred stock was less than $0.1 million.

In April 2020, the Company executed a stock purchase agreement to sell shares of redeemable convertible series B preferred stock (“Series B”). The Series B stock purchase agreement allows for the issuance of up to 45,372,051 shares. In April 2020, the Company issued 22,686,025 shares of Series B at a price of $1.32 per share. Proceeds from this issuance totaled $29.8 million, net of $0.2 million in issuance costs. In March 2021, the Company sold 22,686,025 additional shares of Series B redeemable convertible preferred stock at a price of $1.32 per share upon the achievement of specified development milestones in connection with the second tranche of the Series B stock purchase agreement. Proceeds from this issuance totaled $30.0 million. Total issuance costs associated with the second tranche of the Series B preferred stock was less than $0.1 million.

In August 2020, the Company executed a stock purchase agreement to sell shares of redeemable convertible series

B-1

preferred stock (“Series

B-1”).

The Series

B-1

stock purchase agreement allows for the issuance of up

to 27,152,255 shares. All 27,152,255 shares of Series

B-1

were issued at a price of $1.89 per share in August 2020. Proceeds from this issuance was $51.1 million, net of $0.1 million in issuance costs.

As of June 30, 2021 and December 31, 2020, redeemable convertible preferred stock consisted of the following (in thousands, except share amounts):


	June 30, 2021
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		45,372,050		59,751		60,000		45,372,050
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		128,224,305	$	166,534	$	136,882		128,224,305


	December 31, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		22,686,025		29,761		30,000		22,686,025
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		105,538,280	$	136,544	$	136,882		105,538,280

The rights, preferences and privileges of the Company’s redeemable convertible preferred stock are as follows:

Par Value Per Share

The par value of all preferred stock is $0.001 per share.

Future Tranche Right Feature

The Company determined that the future tranche rights under the Series A and Series B preferred stock purchase agreements (the “future tranche rights”) did not meet the definition of freestanding financial instruments because, while separately exercisable, they were not legally detachable.

The future tranche rights were evaluated for any beneficial conversion features or embedded derivatives, including the conversion option, that could require bifurcation and receive separate accounting treatment. The Company determined that the embedded future tranche obligations did not require bifurcation for accounting purposes as they did not meet the definition of a derivative.

Voting Rights

The holders of the convertible preferred stock are entitled to the number of votes equal to the number of shares of common stock into which each share of convertible preferred stock could be converted on the record date for the vote or consent of stockholders, except as otherwise required by law, and has voting rights and powers equal to the voting rights and powers of the holders of common stock voting as a single class.

Liquidation

holders, an amount equal to the greater of a) original issue price per share plus any noncumulative dividends declared but unpaid, or b) the amount per share that would have been owed had all preferred shares been converted into Common Stock immediately prior to the liquidation event. In the event that assets are insufficient to pay the full amount, distribution will be on a pro rata basis. After payment of all preferential amounts required to be paid to the preferred stockholders, the remaining assets of the Company available for distribution to stockholders shall be distributed among the holders of common stock on a pro rata basis.

A deemed liquidation event is defined as either a merger or consolidation, or the sale, lease, transfer, exclusive license, or other disposition, in a single transaction or series of related transactions, of all or substantially all of the assets of the Company, unless the holders of a majority in voting power of the outstanding Preferred Stock elect otherwise by written notice sent to the Company at least ten days prior to the effective date of any such event.

Conversion

Each share of convertible preferred stock is convertible at the option of the holder into a specified number of shares of common stock based on a conversion ratio subject to adjustment under specified terms and conditions. The initial conversion price and conversion value of Series A convertible preferred stock is $1.00 per share. The initial conversion price and conversion value of Series B convertible preferred stock is $1.32 per share. The initial conversion price and conversion value of Series

B-1

convertible preferred stock is $1.89 per share. Certain terms exist to protect the conversion rights of the holders of the convertible preferred stock in the event of the issuance of additional shares of common stock or a merger or reorganization of the Company.

In the event of a firm commitment underwritten public offering of the Company’s common stock with aggregate proceeds of at least $60.0 million and the Company’s common stock is listed on Nasdaq, all shares of convertible preferred stock will automatically be converted into shares of common stock at the then effective conversion rate.

Redemption

On or after March 31, 2023, upon the vote or written consent of the holders of the Series A, Series B, and Series

B-1

preferred shares then outstanding, each preferred share shall be redeemed, to the extent permitted under law, for the price equal to the original issue price per share plus any noncumulative dividends declared but unpaid in three annual installments commencing no later than 60 days after receipt by the Company. Distributions shall be made out of sufficient funds legally available. Upon and after the date of redemption of preferred shares and payment in full by the Company for each redeemed preferred share, all rights of the holder of such shares, except the right to receive the redemption price without interest upon surrender of the certificates, would cease and terminate. All preferred shares acquired by the Company through redemption would be cancelled and eliminated from the pool of preferred shares authorized for the Company to issue.

The Company has a stock-based compensation plan under which stock options, restricted stock awards (“RSAs”), unrestricted stock awards, restricted stock units, or any combination of the forgoing may be granted to eligible employees, officers, directors, consultants, or other key persons who provide services to the Company. The Company recorded stock-based compensation expense in the following expense categories in its accompanying condensed consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(in thousands)
Research and development	$	552	$	230	$	1,012	$	449
General and administrative		644		177		1,134		366

Total	$	1,196	$	407	$	2,146	$	815

Stock Option Activity

The following table summarizes the stock option activity of the Company’s 2017 Plan for the six months ended June 30, 2021:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511
Granted		8,625,312		$	1.56
Exercised		(1,515,454	)	$	0.50
Cancelled		(158,924	)	$	1.22

Options outstanding as of June 30, 2021		18,903,296		$	1.06		8.90	$	44,555,609
Options exercisable as of June 30, 2021		3,864,800		$	0.58		7.87	$	10,973,189

As of June 30, 2021, total unrecognized compensation expense related to stock options was $13.7 million, which the Company expects to recognize over a remaining weighted-average period of 3.1 years.

Restricted Stock Awards

During the six months ended June 30, 2021, 739,618 RSAs vested. Stock-based compensation expense attributable to RSAs during the six months ended June 30, 2021 totaled $0.3 million.

9. Redeemable Convertible Preferred Stock

In April 2020, the Company executed a stock purchase agreement to sell shares of redeemable convertible series B preferred stock (“Series B”). The Series B stock purchase agreement allows for the issuance of up to 45,372,051 shares. In April 2020, the Company issued 22,686,025 shares of Series B at a price of $1.32 per share. Proceeds from this issuance totaled $29.8 million, net of $0.2 million in issuance costs. In March 2021, the Company sold 22,686,026 additional shares of Series B redeemable convertible preferred stock at a price of $1.32 per share upon the achievement of specified development milestones in connection with the second tranche of the Series B stock purchase agreement. Proceeds from this issuance totaled $30.0 million. Total issuance costs associated with the second tranche of the Series B preferred stock was less than $0.1 million.

In August 2020, the Company executed a stock purchase agreement to sell shares of redeemable convertible series

B-1

preferred stock (“Series

B-1”).

The Series

B-1

stock purchase agreement allows for the issuance of up to 27,152,255 shares. All 27,152,255 shares of Series

B-1

were issued at a price of $1.89 per share in August 2020. Proceeds from this issuance was $51.1 million, net of $0.1 million in issuance costs.

As of December 31, 2020 and 2019, redeemable convertible preferred stock consisted of the following (in thousands, except share amounts):


	December 31, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		22,686,025		29,761		30,000		22,686,025
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		105,538,280	$	136,544	$	136,882		105,538,280


	December 31, 2019
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000

		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000

The rights, preferences and privileges of the Company’s redeemable convertible preferred stock are as follows:

Par Value Per Share

The par value of all preferred stock is $0.001 per share.

Future Tranche Right Feature

Voting Rights

Liquidation

In the event of any liquidation event, deemed liquidation event, dissolution or winding up of the Company, the holders of preferred stock then outstanding shall receive a distribution prior to any distribution to the common holders, an amount equal to the greater of a) original issue price per share plus any noncumulative dividends declared but unpaid, or b) the amount per share that would have been owed had all preferred shares been converted into Common Stock immediately prior to the liquidation event. In the event that assets are insufficient to pay the full amount, distribution will be on a pro rata basis. After payment of all preferential amounts required to be paid to the preferred stockholders, the remaining assets of the Company available for distribution to stockholders shall be distributed among the holders of common stock on a pro rata basis.

Conversion

B-1

Redemption

On or after March 31, 2023, upon the vote or written consent of the holders of the Series A, Series B, and Series

B-1

Net Loss Per Share

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

10. Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	(in thousands, except per share data)
	2021			2020			2021			2020
Numerator:
Net loss	$	(4,493	)	$	(8,392	)	$	(16,599	)	$	(16,306	)

Net loss attributable to common stockholders – basic and diluted		(4,493	)		(8,392	)		(16,599	)		(16,306	)

Denominator:
Weighted-average common stock outstanding – basic and diluted		14,485,746			11,193,065			14,214,543			10,913,053

Net loss per share attributable to common stockholders – basic and diluted	$	(0.31	)	$	(0.75	)	$	(1.17	)	$	(1.49	)

The Company’s potential dilutive securities, which include convertible preferred stock, common stock options and unvested restricted common stock, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding

13. Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Year Ended December 31,
	(in thousands, except per share data)
	2020			2019
Numerator:
Net loss	$	(51,972	)	$	(14,095	)

Net loss attributable to common stockholders – basic and diluted	$	(51,972	)	$	(14,095	)

Denominator:
Weighted-average common stock outstanding – basic and diluted		11,461,011			8,985,710

Net loss per share attributable to common stockholders – basic and diluted	$	(4.53	)	$	(1.57	)


	Year Ended December 31,
	2020		2019
Convertible preferred stock (as converted to common stock)		105,538,281		55,700,000
Stock options to purchase common stock		11,951,362		6,902,873
Unvested restricted common stock		755,868		3,028,540

Total		118,245,511		65,631,413

at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	June 30,
	2021		2020
Convertible preferred stock (as converted to common stock)		128,224,305		78,386,025
Stock options to purchase common stock		18,903,296		11,475,430
Unvested restricted common stock		16,250		1,764,036

Total		147,143,851		91,625,491

Common Stock	12 Months Ended
Common Stock	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Common Stock	10. Common Stock The Company’s Certificate of Incorporation, as amended, authorizes the Company to issue shares of common stock with a par value of $0.001 per share. The holder of each share of common stock is entitled to one vote in respect of each share of stock held. In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, after the payment of all preferential amounts required to be paid to the holders of shares of Convertible Preferred Stock, the remaining funds and assets available for distribution to the stockholders of the Company will be distributed among the holders of shares of common stock, pro rata based on the number of shares of common stock held by each such holder. The holders of Common Stock are also entitled to receive dividends whenever funds and assets are legally available and when declared by the Board of Directors, subject to the prior rights of holders of all classes of redeemable convertible preferred stock outstanding. No dividends have been declared as of December 31, 2020. The Company increased the number of shares of common stock authorized by 2,800,000 to 80,800,000 during 2019 and by 85,200,000 to 166,000,000 during 2020. As of December 31, 2020 and 2019, there were 13,301,649 and 13,334,856 shares of common stock issued and outstanding, respectively.

Equity Incentive Plans

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Equity Incentive Plans

11. Equity Incentive Plans

Founder and Advisor Awards

During 2017, the Company issued 4,690,000 shares of restricted common stock outside of the Company’s 2017 Stock Option and Grant Plan to nonemployee founders and advisors (the “Founders and Advisors”).

The following table summarizes the Company’s Founders and Advisors restricted common stock activity as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Grant-Date Fair Value
Unvested restricted common stock outstanding as of December 31, 2018		2,221,875		$	0.001

Vested		(987,496	)	$	0.001
Forfeited		(109,379	)	$	0.001
Unvested restricted common stock outstanding as of December 31, 2019		1,125,000		$	0.001
Vested		(950,000	)	$	0.001
Forfeited		—			—

The shares are issued under the terms of the respective restricted common stock agreements and are subject to repurchase by the Company at the original purchase price per share upon the termination of the grant

e’s service relationship with the Company. As the restrictions are released and the awards vest, the value is recorded as common stock and excess of par value is recorded as additional paid in capital on the accompanying balance sheet.

As of December 31, 2020, the unrecognized compensation cost related to shares of unvested founder and advisor restricted stock awards (“RSAs”) expected to vest was less than $0.1 million, which is expected to be recognized over an estimated weighted-average amortization period of 0.22 years. The aggregate fair value of awards that vested during both years ended December 31, 2020 and 2019 was $0.5 million.

2017 Stock Option and Grant Plan

In March 2017, the Company’s stockholders approved the 2017 Stock Option and Grant Plan (the “Plan”), under which stock options, RSAs, unrestricted stock awards, restricted stock units, or any combination of the forgoing may be granted to eligible employees, officers, directors, consultants, or other key persons who provide services to the Company. Such issuances are subject to vesting, forfeiture and other restrictions as deemed appropriate by the board of directors (“Board of Directors”). Upon approval, the maximum number of common stock shares reserved and available for issuance under the Plan was 10,000,000 shares. The Company increased the number of shares available for grant under the plan by 6,700,000 million and 2,800,000 million during the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, the maximum number of common stock shares reserved and available for issuance under the Plan was 30,600,000 shares. As of December 31, 2020, there were 11,783,597 shares available for future grant under the 2017 Plan.

The terms of stock option award agreements and RSAs, including vesting requirements, are determined by the Board of Directors at the time of issuance. To date, options granted generally vest over a period of three or

four years with 25% cliff vesting upon the first anniversary of the issuance date and monthly vesting thereafter.

Vesting criteria for awards vary by grant as determined by the Board of Directors. Options and RSAs generally have a

ten-year

term from the date of grant but may be less in the event that the award is granted to a 10% shareholder. The exercise price of an award generally shall not be less than 100% of the estimated fair value of the shares on the date of grant, respectively, as determined by the Board of Directors. The exercise price of an award granted to a 10% shareholder shall not be less than 110% of the estimated fair value of the shares on the date of grant, respectively, as determined by the Board of Directors.

Restricted Stock Awards

The following table summarizes the RSA activity of the Company’s Plan as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Grant-Date Fair Value
Unvested restricted common stock outstanding as of December 31, 2018		4,888,460		$	0.35


Vested		(1,744,301	)	$	0.32
Forfeited		(1,078,125	)	$	0.42

Unvested restricted common stock outstanding as of December 31, 2019		2,066,034		$	0.33

Vested		(1,370,089	)	$	0.33
Forfeited		(115,077	)	$	0.08

Unvested restricted common stock outstanding as of December 31, 2020		580,868		$	0.38

RSAs represent an unsecured promise to grant at no cost a set number of shares of common stock upon vesting. RSA recipients are not entitled to cash dividends and have no voting rights during the vesting period. The RSAs are issued under the terms of the respective RSA agreements and are subject to repurchase upon the holder’s termination of their service relationship with the Company. The award restrictions are released as the awards vest. Upon vesting, the value is recorded as common stock and excess of par value as is recorded as additional paid in capital on the accompanying balance sheets. The common stock is subject to the Company’s right to repurchase at the original purchase price per share.

As of December 31, 2020, the unrecognized compensation cost related to shares of unvested RSAs expected to vest was $0.2 million, which is expected to be recognized over an estimated weighted-average amortization period of 0.43 years. The aggregate fair value of RSAs that vested during the years ended December 31, 2020 and 2019 was $0.5 million and $0.6 million, respectively.

Stock Options

The following table summarizes the stock option activity of the Company’s 2017 Plan as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2019		6,902,873		$	0.50		8.97	$	420,140
Granted		5,716,368		$	0.79
Exercised		(81,870	)	$	0.48
Cancelled		(586,009	)	$	0.51

Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511

Options exercisable as of December 31, 2020		3,611,387		$	0.51		7.65	$	2,466,634

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options th

t had exercise prices lower than the fair value of the Company’s common stock. The total fair value of options vested during the years ended December 31, 2020 and 2019, was $0.9 million and $0.3 million, respectively.

The total intrinsic values of options exercised totaled less than $0.1 million for the year ended December 31, 2020. There were no options exercised for the year ended December 31, 2019. The weighted-average grant date fair value per share of stock options granted was $0.49 and $0.34 for years ending December 31, 2020 and 2019, respectively. Substantially all options outstanding as of December 31, 2020 are expected to vest.

Stock Option Valuation

The weighted average assumptions used to estimate the grant date fair value of the stock options using the Black-Scholes option pricing model were as follows:


	2020	2019

Expected option life (in years)	5.0 – 6.1	5.0 – 6.1
Expected volatility	67% – 72%	70% – 75%
Risk-free interest rate	0.4% – 1.4%	1.6% – 2.6%
Expected dividend yield	— %	— %

Stock-Based Compensation Expense

The Company measures stock-based awards at their grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the awards. The Company recorded stock-based compensation expense in the following expense categories in its accompanying statements of operations:


	Year Ended December 31,
	2020		2019
	(in thousands)
Research and development	$	1,003	$	817
General and administrative		761		877

Total	$	1,764	$	1,694

As of December 31, 2020, there was approximately $3.3 million of unrecognized stock-based compensation expense, which is expected to be recognized over a weighted-average period of approximately 2.84 years.

Income Taxes

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

The Company’s effective income tax rate was (0.3)% and 0.0% for the three months ended June 30, 2021 and 2020, respectively, and was (0.3)% and 0.0% for the six months ended June 30, 2021 and 2020, respectively. The benefit from income taxes was $21 thousand and $0 for the three months ended June 30, 2021 and 2020, respectively, and the provision for income taxes was $53 thousand and $0 for the six months ended June 30, 2021 and 2020, respectively. The change in the benefit from and provision for income taxes for the three and six months ended June 30, 2021, respectively, compared to the three and six months ended June 30, 2020 was primarily due to taxable deferred revenue partially offset by the utilization of federal and state net operating losses and federal and state tax credits.

The effective income tax rate for the three and six months ended June 30, 2021 and 2020 differed from the federal statutory rate primarily due to the valuation allowance maintained against the Company’s deferred tax assets.

12. Income Taxes

During the years ended December 31, 2020 and 2019, the Company recorded no tax provision or benefit due to the losses incurred and the need for a full valuation allowance against its deferred tax assets. All of the Company’s operating losses since inception have been generated in the United States.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2020			2019
Income tax benefit at U.S. federal statutory rate		21.0	%		21.0	%
State income taxes, net of federal benefit		5.9			5.4
Federal and state research and development tax credits		4.4			14.0
Nondeductible/nontaxable permanent items		(0.7	)		(2.7	)
Other		(1.7	)		0.2
Change in valuation allowance		(28.9	)		(37.9	)

Effective tax rate		—	%		—	%

The tax effects of temporary differences that give rise to significant components of the deferred tax assets and liabilities are as follows:


	Year Ended December 31,
	2020			2019
	(in thousands)
Deferred tax assets
Net operating loss carryforwards	$	11,085		$	3,958
Research and development credit carryforwards		5,213			3,076
Operating lease liability		2,154			2,373
Deferred revenue		11,891			8,948
Accruals and reserves		648			479
Capitalized research costs		2,506			—
Other		88			52
Total gross deferred tax assets		33,585			18,886
Valuation allowance		(30,945	)		(15,906	)
Net deferred tax assets		2,640			2,980
Deferred tax liabilities
Depreciation		(597	)		(689	)
Right-of-use asset		(2,043	)		(2,291	)

Total gross deferred tax liabilities		(2,640	)		(2,980	)

Net deferred taxes	$	—		$	—

As of December 31, 2020, the Company had U.S. federal and state net operating loss (“NOL”) carryforwards of $41.0 million and $39.1 million, respectively, which may be available to offset future taxable income. The federal NOLs include $3.3 million which expire at various dates beginning in 2035 and

40.5

million which carry forward indefinitely. The state NOLs expire at various dates beginning in

2035

. As of December

2020

, the Company also had U.S. federal and state research and development tax credit carryforwards of $

3.4

million and $

2.2

million, respectively, which may be available to offset future tax liabilities and begin to expire in

2034

and

2030

, respectively. During the year ended December

2020

, deferred tax assets, before valuation allowance, increased by approximately $

15.0

million mainly due to the operating loss incurred by the Company during that period.

Utilization of the U.S. federal and state net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code, and corresponding provisions of state law, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income or tax li

bilities. In general, an ownership change results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company has performed an analysis of ownership changes through August 17, 2020 and determined that on February 6, 2017 and August 17, 2020 ownership changes had occurred. Based on this analysis, the Company’s ability to use its

pre-change

tax attributes to offset federal and state taxable income are subject to annual limitations and a portion of the attributes generated prior to February 6, 2017 will expire unutilized, which could potentially result in an increased future tax liability. The Company has adjusted its deferred tax assets and valuation allowance balance for the affected tax attribute carryforwards to reflect the expiration of the attributes.

ASC 740 requires a valuation allowance to reduce the deferred tax assets reported, if based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 2020 and 2019. Management reevaluates the positive and negative evidence at each reporting period. The Company had a net increase in the valuation allowance of $15.0 million during 2020 related primarily to the increase in net operating loss carryforwards and research and development tax credit carryforwards, as follows:


	Year Ended December 31,
	2020		2019
	(in thousands)

Valuation allowance as of beginning of year	$	15,906	$	10,559
Increases recorded to income tax provision		15,039		5,347

Valuation allowance as of end of year	$	30,945	$	15,906

The Coronavirus Aid, Relief, and Economic Security (CARES) Act was enacted on March 27, 2020. Among the business provisions, the CARES Act provided for various payroll tax incentives, changes to net operating loss carryback and carryforward rules, business interest expense limitation increases, and bonus depreciation on qualified improvement property. Additionally, the Consolidated Appropriations Act of 2021 was signed on December 27, 2020 which provided additional COVID relief provisions for businesses. The Company has evaluated the impact of both Acts and has determined that any impact is not material to its financial statements.

As of December 31, 2020 and 2019, the Company had not recorded any amounts for unrecognized tax benefits. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. As of December 31, 2020 and 2019, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts had been recognized in the Company’s consolidated statements of operations and comprehensive loss.

The Company files income tax returns in the U.S. federal and Massachusetts jurisdictions, as prescribed by tax laws. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. The statute of limitations for federal and state tax authorities is generally closed for years prior to December 31, 2017, although carryforward attributes that were generated prior to 2017 may still be subject to change upon examination if they are utilized to offset taxable income in subsequent tax years. There are currently no federal or state income tax audits in progress.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Subsequent Events	6 Months Ended	12 Months Ended
Subsequent Events	Jun. 30, 2021	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events Merger with BCTG Acquisition Corporation On April 13, 2021, the Company and BCTG Acquisition Corp. (“BCTG”) signed a definitive merger agreement memorializing the terms of BCTG’s acquisition of 100% of the Company’s issued and outstanding equity securities in exchange for $550.0 million worth of consideration in the form of BCTG common stock (the “Business Combination”). The Business Combination was approved on August 9, 2021 by shareholders of BCTG, resulting in BCTG acquiring 100% of our issued and outstanding equity securities on August 10, 2021. The Business Combination was accounted for as a “reverse recapitalization” in accordance with U.S. GAAP. Under the reverse recapitalization model, the Business Combination was treated as Tango issuing equity for the net assets of BCTG, with no goodwill or intangible assets recorded. Under this method of accounting, BCTG was treated as the “acquired” company for financial reporting purposes. This determination was primarily based on the fact that subsequent to the Business Combination, the Company’s stockholders possess a majority of the voting power of the combined company, the Company comprises all of the ongoing operations of the combined entity, the Company comprises a majority of the governing body of the combined company, and the Company’s senior management comprises all of the senior management of the combined company. As a result of the Business Combination, BCTG was renamed Tango Therapeutics, Inc. Tango received gross proceeds of $166.8 million upon the closing of the Business Combination. Tango continues to operate under the current Tango management team. Subsequent to the closing of the Business Combination, an aggregate of 18.6 million shares of common stock (the “PIPE Financing”) were purchased, resulting in gross proceeds of an additional $186.1 million upon the closing of the PIPE Financing. Total transaction costs and redemptions approximated $27.3 million, resulting in total net proceeds of $325.6 million. Subject to the terms of the merger agreement, upon the closing of the Business Combination (the “Effective Time”), each share of the Company’s redeemable convertible preferred stock (the “Preferred Stock”) issued an d outstanding immediately prior to the Effective Time was converted into a share of the Company’s common stock. At the Effective Time, each option to purchase the Company’s common stock became an option, respectively, to purchase shares of common stock of the surviving entity, subject to adjustment in accordance with the exchange ratio. Completion of the PIPE Financing and merger transaction were subject to approval of BCTG stockholders and the satisfaction or waiver of certain other customary closing conditions. In connection with the preparation of the consolidated financial statements, the Company evaluated the events subsequent to the balance sheet date of June 30, 2021 through August 13, 2021, the date the unaudited condensed consolidated financial statements were available for issuance, and determined that all material transactions have been recorded and disclosed.	14. Subsequent Events Grants of Stock Options under 2017 Plan In January 2021, the Company granted options for the purchase of 6,805,312 common shares, at an exercise price of $1.19 per share, to officers, employees, and consultants of the Company. The aggregate grant-date fair value of these option grants was $8.8 million, which is expected to be recognized as share-based compensation expense over a weighted-average period of 3.8 years. In March 2021, the Company granted options for the purchase of 1,010,000 common shares, at an exercise price of $2.57 per share, to directors, employees, and consultants of the Company. The aggregate grant-date fair value of these option grants was $1.7 million, which is expected to be recognized as share-based compensation expense over a weighted-average period of 3.8 years. Issuance of Redeemable Convertible Series B Preferred Stock Tranche In March 2021, the Company sold 22,686,026 additional shares of Series B redeemable convertible preferred stock at a price of $1.32 per share upon the achievement of specified development milestones in connection with the second tranche of the Series B stock purchase agreement. Each of the tranches under the Series B stock purchase agreement maintain the same rights and features. Gross proceeds from this issuance totaled $30.0 million. Total issuance costs associated with the second tranche of the Series B preferred stock was less than $0.1 million. Waiver of Preferred Stock Redemption Rights In April 2021, the holders of the Series A, Series B and Series B-1 redeemable preferred stock irrevocably waived their right to redeem any shares of Preferred Stock until March 31, 2023. Gilead Collaboration In April 2021, Gilead licensed its second target under the Amended Gilead Agreement and is required to pay the Company a $11.0 million license fee. In connection with the preparation of the consolidated financial statements, the Company evaluated the events subsequent to the balance sheet date of December 31, 2020 through April 12, 2021, the date the consolidated financial statements were available for issuance, and determined that all material transactions have been recorded and disclosed. Events Subsequent to Original Issuance of Consolidated Financial Statements (unaudited) The Company evaluated subsequent events through April 19, 2021, the date of the initial filing of this proxy statement/prospectus. Merger with BCTG Acquisition Corporation On April 13, 2021, the Company and BCTG Acquisition Corp. (“BCTG”) signed a definitive merger agreement, which will result in BCTG acquiring 100% of the Company’s issued and outstanding equity securities. The proposed merger will be accounted for as a “reverse recapitalization” in accordance with U.S. GAAP. Under the reverse recapitalization model, the Business Combination will be treated as Tango issuing equity for the net assets of BCTG, with no goodwill or intangible assets recorded. Under this method of accounting, BCTG will be treated as the “acquired” company for financial reporting purposes. This determination is primarily based on the fact that subsequent to the merger, the Company’s stockholders are expected to have a majority of the voting power of the combined company, the Company will comprise all of the ongoing operations of the combined entity, the Company will comprise a majority of the governing body of the combined company, and the Company’s senior management will comprise all of the senior management of the combined company. As a result of the proposed merger, BCTG will be renamed Tango Therapeutics, Inc. The boards of directors of both BCTG and Tango have approved the proposed merger transaction. BCTG is expected to receive net proceeds of approximately $156.9 million upon the closing of the proposed merger transaction, assuming no redemptions are affected by stockholders of BCTG, and will operate under the current Tango management team upon the closing of the proposed merger. In connection with the proposed merger, BCTG has entered into agreements with existing and new investors to subscribe for and purchase an aggregate of 18.6 million shares of its common stock (the “PIPE Financing”) that will result in net proceeds of an additional $ 179.7 million upon the closing of the PIPE Financing. The closing of the proposed merger is a precondition to the PIPE Financing. Subject to the terms of the merger agreement, at the effective time of the merger (the “Effective Time”), each share of the Company’s redeemable convertible preferred stock “Preferred Stock” issued and outstanding immediately prior to the Effective Time shall be converted into a share of the Company’s common stock. At the Effective Time, each option to purchase the Company’s common stock shall become an option, respectively, to purchase shares of common stock of the surviving entity, subject to adjustment in accordance with the exchange ratio. Completion of the PIPE Financing and proposed merger transactions is subject to approval of BCTG stockholders and the satisfaction or waiver of certain other customary closing conditions. The approval from BCTG stockholders is expected in mid-2021.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Use of Estimates

Segment Information

Cash Equivalents

Investments in Marketable Securities

available-for-sale.

non-credit

Prior to the early adoption of ASU

2016-13

, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,

Fair Value Measurements

•

Level 1 — Fair values are determined utilizing prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access.

•

Level 3 — Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Concentration of Credit Risk and Significant Suppliers

Restricted Cash

The reconciliation of cash and cash equivalents and restricted cash to amounts presented in the consolidated statements of cash flows are as follows:


	December 31,
	2020		2019
	(in thousands)
Cash and cash equivalents	$	28,381	$	22,889
Restricted cash		2,279		2,279

Cash, cash equivalents and restricted cash	$	30,660	$	25,168

Property and Equipment

Estimated useful lives are periodically assessed to determine if changes are appropriate. The estimated useful lives of the Company’s property and equipment are as follows


Asset		Estimated useful life
Computer equipment		3 years
Computer software		5 years
Office equipment		5 years
Furniture and fixtures		7 years
Laboratory equipment		7 years
Leasehold improvements		Shorter of remaining lease term or 10 years

Costs for assets not yet placed into service are capitalized as

construction-in-progress

Operating Leases

The Company accounts for leases in accordance with ASC Topic 842,

Leases

, which it early adopted on January 1, 2018.

right-of-use

asset may be required for items such as initial direct costs paid or incentives received.

The Company elected to account for lease and

non-lease

components as a single lease component, however

non-lease

components that are variable, such as common area maintenance and utilities, are generally paid separately from rent based on actual costs incurred and therefore are not included in the

right-of-use

asset and

operating lease liability and are reflected as an expense in the period incurred. The Company’s lease terms often include renewal options. The amounts determined for the Company’s

right-of-use

Revenue Recognition

The Company’s revenues are generated through its license and collaboration agreements with Gilead. Refer to Note 3, “Collaboration Agreements.”

Effective January 1, 2017, the Company early adopted ASC Topic 606,

Revenue from Contracts with Customers

Exclusive License Rights

non-refundable,

Research and Development Services

co-development

activities, are recorded as a reduction to research and development expense. No collaborative arrangements existed that would result in such reimbursements for the periods presented.

Customer Options

catch-up

Milestone Payments

catch-up

Royalties

which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from licensing agreements.

Research and Development Expenses

Patent Costs

Stock-Based Compensation

Practice Aid,

Valuation of Privately-Held Company Equity Securities Issued as Compensation

Expected Term

Expected Volatility

Risk-free Interest Rate

: The risk-free rate is based on the U.S. Treasury yield curve commensurate with the expected life of the option.

Dividend Rate

: The expected dividend was assumed to be zero as the Company has never paid dividends and has no current plans to do so.The assumptions used in estimating the fair value of stock-based awards represent management’s estimate and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards.Stock-based compensation is classified in the accompanying consolidated statements of operations and comprehensive loss based on the function to which the related services are provided. Forfeitures are accounted for as they occur. Any consideration paid by employees on exercising stock options and the corresponding portion previously credited to additional

paid-in

capital are credited to share capital.

Classification of Convertible Preferred Shares

Classification of Convertible Preferred shares

Share Issuance Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with

in-process

shares or in shareholders’ equity (deficit) as a reduction of additional

paid-in

capital generated as a result of the offering. Should an

in-process

Income Taxes

Penalties and interest expense related to income taxes are included as components of income tax expense and interest expense, respectively, as necessary.

Comprehensive Loss

Net Loss Per Share

two-class

method to calculate earnings per share. The

two-class

method is not applicable during periods with a net loss, as the holders of the convertible preferred stock and unvested restricted stock have no obligation to fund losses.The

two-class

method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The

two-class

Commitments and Contingencies

Subsequent Events

Emerging Growth Company Status (Unaudited)

Recently Adopted Accounting Pronouncements

In December 2019, the FASB issued ASU

2019-12,

Simplifying the Accounting for Income Taxes,

(“ASC 740”). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis

step-up

year-to-date

In August 2020, the FASB issued ASU

2020-06,

Debt

— Debt with Conversion and Other Options (Subtopic

470-20)

and Derivatives and Hedging

— Contracts in Entity’s Own Equity (Subtopic 815

— 40)

2020-06.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU

2016-13

, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments

available-for-sale

2018-13,

Changes to the Disclosure Requirements for Fair Value Measurement

2018-15,

Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract

Recently Issued Accounting Pronouncements

In December 2019, the FASB issued ASU

2019-12,

Simplifying the Accounting for Income Taxes,

(“ASC 740”). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis

step-up

in goodwill obtained in a transaction

year-to-date

loss limitation in interim-period tax accounting. This guidance is effective for the Company for annual and interim periods beginning after December 31, 2020; however, early adoption is permitted. The adoption is not expected to have a material impact on the Company’s consolidated financial statements.

In August 2020, the FASB issued ASU

2020-06,

Debt

— Debt with Conversion and Other Options (Subtopic

470-20)

and Derivatives and Hedging

— Contracts in Entity’s Own Equity (Subtopic 815

— 40)

2020-06

guidance as of January 1, 2021 has no impact on its consolidated financial statements for the year ended December 31, 2020.

2020-06.

As such, the adoption of this guidance is expected to have a material impact on the Company’s financial statements for the year ending December 31, 2021.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of reconciliation of cash and cash equivalents and restricted cash

The reconciliation of cash and cash equivalents and restricted cash to amounts presented in the consolidated statements of cash flows are as follows:


	December 31,
	2020		2019
	(in thousands)
Cash and cash equivalents	$	28,381	$	22,889
Restricted cash		2,279		2,279

Cash, cash equivalents and restricted cash	$	30,660	$	25,168

Summary of estimated useful lives of the Company's property and equipment

Estimated useful lives are periodically assessed to determine if changes are appropriate. The estimated useful lives of the Company’s property and equipment are as follows


Asset		Estimated useful life
Computer equipment		3 years
Computer software		5 years
Office equipment		5 years
Furniture and fixtures		7 years
Laboratory equipment		7 years
Leasehold improvements		Shorter of remaining lease term or 10 years

Fair Value Measurements (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary financial assets measured at fair value on a recurring basis

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	Fair Market Value Measurements as of June 30, 2021
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	30,440	$	—	$	—	$	30,440
U.S. Treasury bills		—		—		—		—
Marketable debt securities:
U.S. Treasury bills		—		126,953		—		132,953
U.S. government agency bonds		—		20,499		—		20,499

Total assets	$	30,440	$	147,452	$	—		177,892


	Fair Market Value Measurements as of December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents
Money market funds	$	12,698	$	—	$	—	$	12,698
U.S. Treasury bills		—		7,175		—		7,175
Marketable debt securities
U.S. Treasury bills		—		131,939		—		131,939
U.S. government agency bonds		—		30,000		—		30,000

Total assets	$	12,698	$	169,114	$	—	$	181,812

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	Fair Market Value Measurements as of December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents
Money market funds	$	12,698	$	—	$	—	$	12,698
U.S. Treasury bills		—		7,175		—		7,175
Marketable debt securities
U.S. Treasury bills		—		131,939		—		131,939
U.S. government agency bonds		—		30,000		—		30,000

Total assets	$	12,698	$	169,114	$	—	$	181,812


	Fair Market Value Measurements as of December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	18,508	$	—	$	—	$	18,508
Marketable debt securities:
U.S. Treasury bills		—		17,536		—		17,536

Total assets	$	18,508	$	17,536	$	—	$	36,044

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Marketable Securities (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of debt securities, available-for-sale

The following table summarizes the Company’s marketable debt securities, classified as

available-for-sale:


	Fair Value Measurements as of June 30, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss			Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	126,954	$	5	$	(6	)	$	126,953
U.S. government agency bonds		20,496		9		(6	)		20,499

	$	147,450	$	14	$	(12	)	$	147,452


	Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	131,927	$	12	$	—	$	131,939
U.S. government agency bonds		29,995		5		—		30,000

	$	161,922	$	17	$	—	$	161,939


	Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	131,927	$	12	$	—	$	131,939
U.S. government agency bonds		29,995		5		—		30,000

	$	161,922	$	17	$	—	$	161,939


	Fair Value Measurements as of December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss		Fair Value
	(in thousands)
Marketable debt securities:
U.S. Treasury bills	$	17,526	$	10	$	—	$	17,536

	$	17,526	$	10	$	—	$	17,536

Supplemental Balance Sheet Information- (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of property, plant and equipment

Property and equipment, net as of June 30, 2021 and December 31, 2020 consists of the following:


	June 30, 2021			December 31, 2020
	(in thousands)
Laboratory equipment	$	5,337		$	4,580
Computer equipment		172			172
Computer software		125			125
Furniture and fixtures		459			384
Leasehold improvements		246			246
Construction in process		158			—

		6,497			5,507
Less: Accumulated depreciation		(2,100	)		(1,684	)

Property and equipment, net	$	4,397		$	3,823

Property and equipment, net as of December 31, 2020 and 2019 consists of the following:


	December 31,
	2020			2019
	(in thousands)
Laboratory equipment	$	4,580		$	3,823
Computer equipment		172			172
Computer software		125			9
Furniture and fixtures		384			246
Leasehold improvements		246			230

		5,507			4,480

Less: Accumulated depreciation		(1,684	)		(1,038	)

Property and equipment, net	$	3,823		$	3,442

Schedule of accrued expenses and other current liabilities current

Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 include the following:


	June 30, 2021		December 31, 2020
	(in thousands)
Payroll and employee-related costs	$	2,046	$	2,652
Research and development costs		3,691		2,695
Other		697		793

Total accrued expenses and other current liabilities	$	6,434	$	6,140

Accrued expenses and other current liabilities as of December 31, 2020 and 2019 include the following:


	December 31,
	2020		2019
	(in thousands)
Payroll and employee-related costs	$	2,652	$	1,830
Research and development costs		2,695		2,764
Other		793		338

Total accrued expenses and other current liabilities	$	6,140	$	4,932

Schedule of cash, cash equivalents restricted cash and restricted cash equivalents

The reconciliation of cash and cash equivalents and restricted cash to amounts presented in the condensed consolidated statements of cash flows are as follows:


	June 30, 2021		June 30, 2020
	(in thousands)
Cash and cash equivalents	$	50,902	$	13,118
Restricted cash		2,279		2,279

Cash, cash equivalents and restricted cash	$	53,181	$	15,397

Leases (Tables)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Summary of lease cost

As of December 31, 2020 and 2019, assets under the operating lease totaled $7.5 million and $8.4 million, respectively. The elements of lease cost were as follows:


	Year Ended December 31,
Operating leases	2020			2019
Operating lease cost	$	1,889		$	1,889
Short-term lease cost		93			36
Variable lease cost		643			541

Total operating lease costs	$	2,625		$	2,466


Other information	December 31, 2020			December 31, 2019
Operating cash flows used for operating leases	$	1,782		$	1,735
Weighted average remaining lease term in years		5.5			6.5
Weighted average discount rate		12	%		12	%

Summary of lessee, operating lease, liability, maturity

Future minimum lease payments under

non-cancelable

leases that have commenced as of December 31, 2020 are as follows:


Year Ended December 31,	Maturity of Lease Liabilities
2021	$	1,836
2022		1,891
2023		1,948
2024		2,007
2025		2,067
Thereafter		1,046

Total lease payments		10,795
Less: imputed interest		(2,911	)

Total operating lease liabilities	$	7,884

Redeemable Convertible Preferred Stock (Table)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Temporary Equity Disclosure [Abstract]

Summary of redeemable convertible preferred stock

As of June 30, 2021 and December 31, 2020, redeemable convertible preferred stock consisted of the following (in thousands, except share amounts):


	June 30, 2021
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		45,372,050		59,751		60,000		45,372,050
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		128,224,305	$	166,534	$	136,882		128,224,305


	December 31, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		22,686,025		29,761		30,000		22,686,025
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		105,538,280	$	136,544	$	136,882		105,538,280


	December 31, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000
Series B		45,372,050		22,686,025		29,761		30,000		22,686,025
Series B-1		27,152,255		27,152,255		51,083		51,182		27,152,255

		128,224,305		105,538,280	$	136,544	$	136,882		105,538,280


	December 31, 2019
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Value		Common Stock Issuable Upon Conversion
Series A		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000

		55,700,000		55,700,000	$	55,700	$	55,700		55,700,000

Summary of the Company recorded stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories in its accompanying condensed consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(in thousands)
Research and development	$	552	$	230	$	1,012	$	449
General and administrative		644		177		1,134		366

Total	$	1,196	$	407	$	2,146	$	815


	Year Ended December 31,
	2020		2019
	(in thousands)
Research and development	$	1,003	$	817
General and administrative		761		877

Total	$	1,764	$	1,694

Summary of the stock option activity of the Company's Plan

The following table summarizes the stock option activity of the Company’s 2017 Plan for the six months ended June 30, 2021:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511
Granted		8,625,312		$	1.56
Exercised		(1,515,454	)	$	0.50
Cancelled		(158,924	)	$	1.22

Options outstanding as of June 30, 2021		18,903,296		$	1.06		8.90	$	44,555,609
Options exercisable as of June 30, 2021		3,864,800		$	0.58		7.87	$	10,973,189

The following table summarizes the stock option activity of the Company’s 2017 Plan as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2019		6,902,873		$	0.50		8.97	$	420,140
Granted		5,716,368		$	0.79
Exercised		(81,870	)	$	0.48
Cancelled		(586,009	)	$	0.51

Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511

Options exercisable as of December 31, 2020		3,611,387		$	0.51		7.65	$	2,466,634

Equity Incentive Plans (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of the stock option activity of the Company's Plan

The following table summarizes the stock option activity of the Company’s 2017 Plan for the six months ended June 30, 2021:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511
Granted		8,625,312		$	1.56
Exercised		(1,515,454	)	$	0.50
Cancelled		(158,924	)	$	1.22

Options outstanding as of June 30, 2021		18,903,296		$	1.06		8.90	$	44,555,609
Options exercisable as of June 30, 2021		3,864,800		$	0.58		7.87	$	10,973,189

The following table summarizes the stock option activity of the Company’s 2017 Plan as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2019		6,902,873		$	0.50		8.97	$	420,140
Granted		5,716,368		$	0.79
Exercised		(81,870	)	$	0.48
Cancelled		(586,009	)	$	0.51

Options outstanding as of December 31, 2020		11,952,362		$	0.64		8.58	$	6,625,511

Options exercisable as of December 31, 2020		3,611,387		$	0.51		7.65	$	2,466,634

Summary of the weighted average assumptions used to estimate the grant date fair value of the stock options using the Black-Scholes option pricing model

The weighted average assumptions used to estimate the grant date fair value of the stock options using the Black-Scholes option pricing model were as follows:


	2020	2019

Expected option life (in years)	5.0 – 6.1	5.0 – 6.1
Expected volatility	67% – 72%	70% – 75%
Risk-free interest rate	0.4% – 1.4%	1.6% – 2.6%
Expected dividend yield	— %	— %

Summary of the Company recorded stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories in its accompanying condensed consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(in thousands)
Research and development	$	552	$	230	$	1,012	$	449
General and administrative		644		177		1,134		366

Total	$	1,196	$	407	$	2,146	$	815


	Year Ended December 31,
	2020		2019
	(in thousands)
Research and development	$	1,003	$	817
General and administrative		761		877

Total	$	1,764	$	1,694

Founder and Advisors Restricted Stock Award [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure of Share Based Compensation Arrangements by Share Based Payment Award

The following table summarizes the Company’s Founders and Advisors restricted common stock activity as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Grant-Date Fair Value
Unvested restricted common stock outstanding as of December 31, 2018		2,221,875		$	0.001

Vested		(987,496	)	$	0.001
Forfeited		(109,379	)	$	0.001
Unvested restricted common stock outstanding as of December 31, 2019		1,125,000		$	0.001
Vested		(950,000	)	$	0.001
Forfeited		—			—

Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure of Share Based Compensation Arrangements by Share Based Payment Award

The following table summarizes the RSA activity of the Company’s Plan as of and for the years ended December 31, 2020 and 2019:


	Number of shares			Weighted Average Grant-Date Fair Value
Unvested restricted common stock outstanding as of December 31, 2018		4,888,460		$	0.35


Vested		(1,744,301	)	$	0.32
Forfeited		(1,078,125	)	$	0.42

Unvested restricted common stock outstanding as of December 31, 2019		2,066,034		$	0.33

Vested		(1,370,089	)	$	0.33
Forfeited		(115,077	)	$	0.08

Unvested restricted common stock outstanding as of December 31, 2020		580,868		$	0.38

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Summary of reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2020			2019
Income tax benefit at U.S. federal statutory rate		21.0	%		21.0	%
State income taxes, net of federal benefit		5.9			5.4
Federal and state research and development tax credits		4.4			14.0
Nondeductible/nontaxable permanent items		(0.7	)		(2.7	)
Other		(1.7	)		0.2
Change in valuation allowance		(28.9	)		(37.9	)

Effective tax rate		—	%		—	%

Summary of deferred tax assets and liabilities


	Year Ended December 31,
	2020			2019
	(in thousands)
Deferred tax assets
Net operating loss carryforwards	$	11,085		$	3,958
Research and development credit carryforwards		5,213			3,076
Operating lease liability		2,154			2,373
Deferred revenue		11,891			8,948
Accruals and reserves		648			479
Capitalized research costs		2,506			—
Other		88			52
Total gross deferred tax assets		33,585			18,886
Valuation allowance		(30,945	)		(15,906	)
Net deferred tax assets		2,640			2,980
Deferred tax liabilities
Depreciation		(597	)		(689	)
Right-of-use asset		(2,043	)		(2,291	)

Total gross deferred tax liabilities		(2,640	)		(2,980	)

Net deferred taxes	$	—		$	—

Summary of net increase in the valuation allowance

The Company had a net increase in the valuation allowance of $15.0 million during 2020 related primarily to the increase in net operating loss carryforwards and research and development tax credit carryforwards, as follows:


	Year Ended December 31,
	2020		2019
	(in thousands)

Valuation allowance as of beginning of year	$	15,906	$	10,559
Increases recorded to income tax provision		15,039		5,347

Valuation allowance as of end of year	$	30,945	$	15,906

Net Loss Per Share (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2021

Dec. 31, 2020

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

10. Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	(in thousands, except per share data)
	2021			2020			2021			2020
Numerator:
Net loss	$	(4,493	)	$	(8,392	)	$	(16,599	)	$	(16,306	)

Net loss attributable to common stockholders – basic and diluted		(4,493	)		(8,392	)		(16,599	)		(16,306	)

Denominator:
Weighted-average common stock outstanding – basic and diluted		14,485,746			11,193,065			14,214,543			10,913,053

Net loss per share attributable to common stockholders – basic and diluted	$	(0.31	)	$	(0.75	)	$	(1.17	)	$	(1.49	)

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Year Ended December 31,
	(in thousands, except per share data)
	2020			2019
Numerator:
Net loss	$	(51,972	)	$	(14,095	)

Net loss attributable to common stockholders – basic and diluted	$	(51,972	)	$	(14,095	)

Denominator:
Weighted-average common stock outstanding – basic and diluted		11,461,011			8,985,710

Net loss per share attributable to common stockholders – basic and diluted	$	(4.53	)	$	(1.57	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

The Company excluded the following potential common shares, presented based on amounts outstanding

at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	June 30,
	2021		2020
Convertible preferred stock (as converted to common stock)		128,224,305		78,386,025
Stock options to purchase common stock		18,903,296		11,475,430
Unvested restricted common stock		16,250		1,764,036

Total		147,143,851		91,625,491

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2020		2019
Convertible preferred stock (as converted to common stock)		105,538,281		55,700,000
Stock options to purchase common stock		11,951,362		6,902,873
Unvested restricted common stock		755,868		3,028,540

Total		118,245,511		65,631,413

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) shares in Millions		3 Months Ended				6 Months Ended		12 Months Ended
	Apr. 13, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Aug. 10, 2021
Net loss		$ (4,493,000)	$ (12,106,000)	$ (8,392,000)	$ (7,914,000)	$ (16,599,000)	$ (16,306,000)	$ (51,972,000)	$ (14,095,000)
Accumulated deficit		(119,700,000)				(119,700,000)		(103,101,000)	$ (51,129,000)
Gross proceeds from the sale of preferred shares						166,900,000		166,900,000
BCTG Acquisition Corp [Member]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%									100.00%
Consideration Received on Transaction						$ 166,800,000		$ 156,900,000
Stock Issued During Period, Shares						18.6		18.6
Stock Issued During Period, Value						$ 186,100,000		$ 179,700,000
Payments to Acquire Businesses, Gross						352,900,000
Business Combination, Consideration Transferred, Equity Interests	$ 550,000,000.0
Business Acquisition, Transaction Costs	$ 27,300,000	$ 27,300,000				27,300,000
Business Combination, Consideration Transferred						325,600,000
Gilead [Member]
Payments to Acquire Businesses, Gross						$ 202,100,000
Series B Preferred Stock [Member] \| Share-based Payment Arrangement, Tranche Two [Member]
Gross proceeds from the sale of preferred shares								$ 30.0

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash And Cash Equivalents And Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 50,902	$ 28,381	$ 22,889
Restricted cash	$ 2,279	2,279	2,279
Cash, cash equivalents and restricted cash		$ 30,660	$ 25,168

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of The Company's Property And Equipment (Detail)	12 Months Ended
	Dec. 31, 2020
Computer equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	3 years
Computer software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	5 years
Office equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	5 years
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	7 years
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	7 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	Shorter of remaining lease term or 10 years

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Restricted cash		$ 2,279,000		$ 2,279,000	$ 2,279,000
Deferred offering costs				0	0
Gross proceeds from the sale of preferred shares		$ 29,990,000	$ 29,850,000	$ 80,844,000	$ 11,000,000
Share-based Payment Arrangement, Tranche Two [Member] \| Series B Preferred Stock [Member]
Sale of Stock, Price Per Share	$ 1.32
Gross proceeds from the sale of preferred shares	$ 28,400,000

Collaboration Agreements - Additional Information (Detail) $ in Thousands	1 Months Ended					3 Months Ended			6 Months Ended		12 Months Ended
	Apr. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Aug. 31, 2020 USD ($) Number	May 31, 2019 USD ($)	Oct. 31, 2018 Number	Jun. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) Number	Jul. 31, 2019 USD ($)
Collaboration Agreements [Line Items]
Deferred revenue, Current		$ 31,977				$ 24,500			$ 24,500		$ 31,977	$ 19,594
Deferred revenue, Non current		120,805				118,742			118,742		120,805	14,106
Proceeds from fees received									4,000		2,000
Accounts receivable current, Research extension fee		12,000				2,000			2,000		12,000
Contract asset, Research extension fee		10,000				6,000			$ 6,000		10,000
Revenue remaining performance obligations expected remaining contractual term									6 years 1 month 6 days
Receivable research extension fee						12,000			$ 12,000
Two Thousand And Eighteen Gilead Agreement [Member]
Collaboration Agreements [Line Items]
Research Term					3 years
Number of Licensed Product \| Number					5								2
Non-refundable upfront payment received		50,000				50,000			50,000		50,000		$ 50,000
Milestone payments receivable													1,700,000
Transaction price allocated to performance obligation													$ 50,000
Performance obligation, Satisfaction description													The Company determined that the single combined performance obligation is satisfied over time as the customer is simultaneously receiving and consuming the benefit of the Company’s performance.
Proceeds from license fee received				$ 7,500
Deferred revenue, Current												18,600
Gilead Letter Agreement [Member]
Collaboration Agreements [Line Items]
Contract with customer liability														$ 2,600
Contract with customer liability, Revenue recognized								$ 300		$ 700	700	9,400
Deferred revenue, Current												1,000
Gilead Agreement [Member]
Collaboration Agreements [Line Items]
Transaction price allocated to performance obligation		187,000				187,000			187,000		187,000
Contract with customer liability		125,000				125,000			125,000		125,000
Research Extension Fee		12,000									12,000
Contract with customer liability, Revenue recognized						7,200		$ 4,700	13,500	$ 9,100	7,000	15,200
Deferred revenue, Current		32,000				24,500			24,500		32,000	19,600
Deferred revenue, Non current		$ 120,800				118,700			118,700		$ 120,800	$ 14,100
Amended Gilead Agreement [Member]
Collaboration Agreements [Line Items]
Research Term			7 years
Number of Licensed Product \| Number			15
Milestone payments receivable			$ 410,000
Temporary equity, Par value			$ 125,000
Equity method investment, Ownership percentage		10.00%									10.00%
Number of years determining royalties receivable			10 years
Revenue recognized, Cumulative catch-up adjustment							$ 11,300
Assessment of variable consideration constraint, Description		the Company determined that the variable consideration of $12.0 million should not be constrained as the potential for a significant reversal of cumulative revenue recognized at the contract level is remote, and therefore the research extension consideration was added to the transaction price under the Gilead Agreement.
Research Extension Fee		$ 12,000									$ 12,000
Licensed a program,Fee amount	$ 11,000
License fee amount received,recognised as revenue	$ 11,000
Amended Gilead Agreement [Member] \| Series B One Preferred Stock [Member]
Collaboration Agreements [Line Items]
Temporary equity, Par value			$ 20,000
Gilead Agreement Based Performance [Member]
Collaboration Agreements [Line Items]
Contract with customer liability, Revenue recognized						$ 11,000			$ 11,000

Fair Value Measurements - Summary Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash equivalents
Money market funds	$ 30,440	$ 12,698	$ 18,508
U.S. Treasury bills		7,175
Marketable debt securities
Total assets	177,892	181,812	36,044
Marketable Debt Securities [Member] \| US Treasury Securities [Member]
Marketable debt securities
Investments, Fair Value Disclosure	132,953	131,939	17,536
Marketable Debt Securities [Member] \| US Government Agencies Debt Securities [Member]
Marketable debt securities
Investments, Fair Value Disclosure	20,499	30,000
Fair Value, Inputs, Level 1 [Member]
Cash equivalents
Money market funds	30,440	12,698	18,508
Marketable debt securities
Total assets	30,440	12,698	18,508
Fair Value, Inputs, Level 2 [Member]
Cash equivalents
U.S. Treasury bills		7,175
Marketable debt securities
Total assets	147,452	169,114	17,536
Fair Value, Inputs, Level 2 [Member] \| Marketable Debt Securities [Member] \| US Treasury Securities [Member]
Marketable debt securities
Investments, Fair Value Disclosure	126,953	131,939	$ 17,536
Fair Value, Inputs, Level 2 [Member] \| Marketable Debt Securities [Member] \| US Government Agencies Debt Securities [Member]
Marketable debt securities
Investments, Fair Value Disclosure	$ 20,499	$ 30,000

Marketable Securities - Summary of Debt Securities, Available For Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 147,450	$ 161,922	$ 17,526
Gross Unrealized Gains	14	17	10
Gross Unrealized Loss	(12)
Fair Value	147,452	161,939	17,536
U.S. Treasury bills [Member] \| Marketable Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	126,954	131,927	17,526
Gross Unrealized Gains	5	12	10
Gross Unrealized Loss	(6)
Fair Value	126,953	131,939	$ 17,536
U.S. government agency bonds [Member] \| Marketable Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,496	29,995
Gross Unrealized Gains	9	5
Gross Unrealized Loss	(6)
Fair Value	$ 20,499	$ 30,000

Marketable Securities - Additional Information (Detail) - Marketable Debt Securities [Member] $ in Millions	Jun. 30, 2021 USD ($) Number	Dec. 31, 2020 USD ($) Number	Dec. 31, 2019 USD ($) Number
Debt Securities, Available-for-sale [Line Items]
Number of debt securities considered to be in an unrealized loss position \| Number	0	0	0
Marketable securities, Accrued interest \| $	$ 0.1	$ 0.1	$ 0.1

Supplemental Balance Sheet Information - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Depreciation	$ 200	$ 200	$ 416	$ 341	$ 718	$ 643
Security Deposits [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Restricted Cash	$ 2,300	$ 2,300	$ 2,300	$ 2,300

Supplemental Balance Sheet Information -Schedule of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,497	$ 5,507	$ 4,480
Less: Accumulated depreciation	(2,100)	(1,684)	(1,038)
Property and equipment, net	4,397	3,823	3,442
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,337	4,580	3,823
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	172	172	172
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	125	125	9
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	459	384	246
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	246	246	$ 230
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 158	$ 0

Supplemental Balance Sheet Information - Schedule of Accrued Expenses and Other Current Liabilities Current (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Payroll and employee-related costs	$ 2,046	$ 2,652	$ 1,830
Research and development costs	3,691	2,695	2,764
Other	697	793	338
Total accrued expenses and other current liabilities	$ 6,434	$ 6,140	$ 4,932

Supplemental Balance Sheet Information - Schedule of Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Line Items]
Cash, cash equivalents and restricted cash	$ 53,181	$ 30,660	$ 15,397	$ 25,168	$ 38,123
Construction in Progress [Member]
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Line Items]
Cash and cash equivalents	50,902		13,118
Restricted cash	2,279		2,279
Cash, cash equivalents and restricted cash	$ 53,181		$ 15,397

Leases - Summary of Lease Cost (Detail) - USD ($)	12 Months Ended
Leases - Summary of Lease Cost (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operating leases
Operating lease cost	$ 1,889	$ 1,889
Short-term lease, cost	93	36
Variable lease, cost	643	541
Total operating lease costs	2,625	2,466
Other information
Operating cash flows used for operating leases	$ 1,782	$ 1,735
Weighted average remaining lease term in years	5 years 6 months	6 years 6 months
Weighted average discount rate	12.00%	12.00%

Leases - Summary of Lessee, Operating Lease, Liability, Maturity (Detail) - USD ($)	Dec. 31, 2020	Jul. 31, 2017
Lessee Disclosure [Abstract]
2021	$ 1,836
2022	1,891
2023	1,948
2024	2,007
2025	2,067
Thereafter	1,046
Total lease payments	10,795
Less: imputed interest	(2,911)
Total operating lease liabilities	$ 7,884	$ 9,500,000

Leases - Additional Information (Detail) - USD ($)	1 Months Ended
Leases - Additional Information (Detail) - USD ($)	Sep. 30, 2019	Jul. 31, 2017	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating lease, Term of contract		8 years
Operating lease, Option to extend		one additional three-year period
Operating lease liability		$ 9,500,000		$ 7,884
Operating lease right-of-use asset		9,800,000	$ 6,988,000	7,480,000	$ 8,387,000
Tenant improvements		300,000
Operating lease obligation due				$ 0	$ 0
Accrued rent		$ 1,700,000
Percentage of annual increase of fixed annual rent payable		3.00%
Operating lease, Future minimum rent payments due		$ 15,600,000
Proceeds from line of credit		$ 600,000
The Two Hundred And One Brookline Avenue Lease [Member]
Operating lease, Term of contract	10 years
Operating lease, Option to extend	two five-year periods
Accrued rent	$ 5,100,000
Percentage of annual increase of fixed annual rent payable	3.00%
Proceeds from line of credit	$ 1,700,000
Payment for tenant improvements	$ 12,700,000
The Two Hundred And One Brookline Avenue Lease [Member] \| Subsequent Event [Member] \| Letter of Credit [Member]
Additional letter of credit			$ 1,700,000

Commitments and Contingencies - Additional Information (Detail)	Jun. 30, 2021 USD ($) Number	Dec. 31, 2020 USD ($) Number
Number of pending claims \| Number	0	0
HitGen Agreement [Member]
Contractual obligation	$ 0	$ 0
Medivir Agreement [Member]
Upfront payment		400,000
Milestone payments		1,400,000
Specified Regulatory Approval And Sales Milestones [Member] \| Medivir Agreement [Member]
Contractual obligation		25,000,000.0
Specified Clinical Milestones [Member] \| Medivir Agreement [Member]
Milestone payments		700,000
Specified Regulatory And Sales Milestones For Genetic Context [Member] \| Medivir Agreement [Member]
Contractual obligation		$ 5,000,000.0

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended						6 Months Ended	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2021	Jan. 31, 2021	Dec. 31, 2020	Aug. 31, 2020	Apr. 30, 2020	Jan. 31, 2019	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Share based payment arrangement, Unrecognized compensation cost				$ 3.3					$ 3.3
Share based payment arrangement, Unrecognized compensation cost, Recognition period									2 years 10 months 2 days
Share-based Payment Arrangement, Option [Member] \| Two Thousand And Seventeen Plan [Member]
Class of Stock [Line Items]
Share based payment arrangement, Unrecognized compensation cost								$ 13.7
Share based payment arrangement, Unrecognized compensation cost, Recognition period								3 years 1 month 6 days
Share based payment arrangement, Shares reserved for future issuance								739,618
Share based payment arrangement,Options, Fair value of options vested during period								$ 0.3	$ 0.9	$ 0.3
Subsequent Event [Member] \| Share-based Payment Arrangement, Option [Member] \| Two Thousand And Seventeen Plan [Member]
Class of Stock [Line Items]
Share based payment arrangement, Unrecognized compensation cost, Recognition period		3 years 9 months 18 days	3 years 9 months 18 days
Series A Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Redeemable convertible preferred stock allocated to investors	55,000,000
Redeemable convertible preferred stock shares authorized				55,700,000				55,700,000	55,700,000	55,700,000
Redeemable convertible preferred stock issued during period shares new issues	18,700,000						11,000,000				26,000,000
Redeemable convertible preferred stock issue price per share	$ 1.00						$ 1.00				$ 1.00
Proceeds from Issuance of Redeemable Convertible Preferred Stock	$ 14.0						$ 11.0				$ 26.0
Repayments of convertible notes and accrued interest	$ 4.7
Redeemable convertible preferred stock issue price per share											$ 1.00
Aggregate redeemable convertible preferred stock Issuance Costs							$ 0.1
Redeemable convertible preferred stock conversion price				$ 1.00				$ 1.00	$ 1.00
Series B Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Redeemable convertible preferred stock shares authorized				45,372,050		45,372,051		45,372,050	45,372,050
Redeemable convertible preferred stock issued during period shares new issues		22,686,026				22,686,025
Redeemable convertible preferred stock issue price per share		$ 1.32				$ 1,320,000
Proceeds from Issuance of Redeemable Convertible Preferred Stock						$ 29.8
Redeemable convertible preferred stock issue price per share						$ 1.32
Redeemable convertible preferred stock Issuance Costs		$ 0.1				$ 0.2
Redeemable convertible preferred stock conversion price				$ 1.32				$ 1.32	$ 1.32
Series B Redeemable Convertible Preferred Stock [Member] \| Subsequent Event [Member]
Class of Stock [Line Items]
Proceeds from Issuance of Redeemable Convertible Preferred Stock		30.0						$ 30.0
Redeemable convertible preferred stock Issuance Costs		$ 0.1
Series B One Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Redeemable convertible preferred stock shares authorized				27,152,255				27,152,255	27,152,255
Redeemable convertible preferred stock issued during period shares new issues					27,152,255
Redeemable convertible preferred stock issue price per share					$ 1.89
Proceeds from Issuance of Redeemable Convertible Preferred Stock					$ 51.1
Redeemable convertible preferred stock issue price per share					$ 1.89
Redeemable convertible preferred stock Issuance Costs					$ 0.1
Redeemable convertible preferred stock conversion price				$ 1.89				$ 1.89	$ 1.89
Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Redeemable convertible preferred stock shares authorized				128,224,305				128,224,305	128,224,305	55,700,000
Redeemable convertible preferred stock conversion trigger aggregate proceeds from public offering				$ 60.0				$ 60.0	$ 60.0
Period In which Redeemable convertible preferred stock to be redeemed				60 days				60 days
Redeemable convertible preferred stock Par or Stated Value Per Share				$ 0.001				$ 0.001	$ 0.001

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred stock (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 2020
Series A Redeemable Convertible Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred Stock Authorized	55,700,000	55,700,000	55,700,000
Preferred Stock Issued and Outstanding	55,700,000	55,700,000	55,700,000
Carrying Value	$ 55,700	$ 55,700	$ 55,700
Liquidation Value	$ 55,700	$ 55,700	$ 55,700
Common Stock Issuable Upon Conversion	55,700,000	55,700,000	55,700,000
Series B Redeemable Convertible Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred Stock Authorized	45,372,050	45,372,050		45,372,051
Preferred Stock Issued and Outstanding	45,372,050	22,686,025
Carrying Value	$ 59,751	$ 29,761
Liquidation Value	$ 60,000	$ 30,000
Common Stock Issuable Upon Conversion	45,372,050	22,686,025
Series B One Redeemable Convertible Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred Stock Authorized	27,152,255	27,152,255
Preferred Stock Issued and Outstanding	27,152,255	27,152,255
Carrying Value	$ 51,083	$ 51,083
Liquidation Value	$ 51,182	$ 51,182
Common Stock Issuable Upon Conversion	27,152,255	27,152,255
Redeemable Convertible Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred Stock Authorized	128,224,305	128,224,305	55,700,000
Preferred Stock Issued and Outstanding	128,224,305	105,538,280	55,700,000
Carrying Value	$ 166,534	$ 136,544	$ 55,700
Liquidation Value	$ 136,882	$ 136,882	$ 55,700
Common Stock Issuable Upon Conversion	128,224,305	105,538,280	55,700,000

Common Stock - Additional Informational (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Dec. 31, 2019
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Common Stock, Voting Rights	one vote
Dividends, Common Stock	$ 0
Common Stock, Shares Authorized	166,000,000	166,000,000	80,800,000
Common Stock, Shares, Issued	13,301,649	14,817,103	13,334,856
Common Stock, Shares, Outstanding	13,301,649	14,817,103	13,334,856
Previously Reported [Member]
Common Stock, Shares Authorized	85,200,000		2,800,000

Net Loss Per Share - Schedule Of Earnings Per Share Basic And Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (4,493)	$ (12,106)	$ (8,392)	$ (7,914)	$ (16,599)	$ (16,306)	$ (51,972)	$ (14,095)
Net loss attributable to common stockholders – basic and diluted	$ (4,493)		$ (8,392)		$ (16,599)	$ (16,306)	$ (51,972)	$ (14,095)
Denominator:
Weighted-average common stock outstanding – basic and diluted	14,485,746		11,193,065	11,193,065	14,214,543	10,913,053	11,461,011	8,985,710
Net loss per share attributable to common stockholders – basic and diluted	$ (0.31)		$ (0.75)	$ (0.75)	$ (1.17)	$ (1.49)	$ (4.53)	$ (1.57)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Net Loss Per Share - Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share (Details) - shares	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	147,143,851	91,625,491	118,245,511	65,631,413
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	128,224,305	78,386,025	105,538,281	55,700,000
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	18,903,296	11,475,430	11,951,362	6,902,873
Unvested restricted common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	16,250	1,764,036	755,868	3,028,540

Income Taxes - Summary Of Reconciliation Of The U.S. Federal Statutory Income Tax Rate To The Company's Effective Income Tax Rate (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax benefit at U.S. federal statutory rate					21.00%	21.00%
State income taxes, net of federal benefit					5.90%	5.40%
Federal and state research and development tax credits					4.40%	14.00%
Nondeductible/nontaxable permanent items					(0.70%)	(2.70%)
Other					(1.70%)	0.20%
Change in valuation allowance					(28.90%)	(37.90%)
Effective tax rate	(0.30%)	0.00%	(0.30%)	0.00%	0.00%	0.00%

Income Taxes - Summary Of Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforwards	$ 11,085	$ 3,958
Research and development credit carryforwards	5,213	3,076
Operating lease liability	2,154	2,373
Deferred revenue	11,891	8,948
Accruals and reserves	648	479
Capitalized research costs	2,506	0
Other	88	52
Total gross deferred tax assets	33,585	18,886
Valuation allowance	(30,945)	(15,906)	$ (10,559)
Net deferred tax assets	2,640	2,980
Deferred tax liabilities
Depreciation	(597)	(689)
Right-of-use asset	(2,043)	(2,291)
Total gross deferred tax liabilities	(2,640)	(2,980)
Net deferred taxes	$ 0	$ 0

Income Taxes - Summary Of Net Increase In The Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Valuation Allowance [Abstract]
Valuation allowance as of beginning of year	$ 15,906	$ 10,559
Increases recorded to income tax provision	15,039	5,347
Valuation allowance as of end of year	$ 30,945	$ 15,906

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Tax provision or benefit	$ (21)	$ 0	$ 53	$ 0	$ 0	$ 0
Percentage of increase in ownership percentage over a three year period					50.00%
Increase in valuation allowance					$ 15,039	5,347
Unrecognized Tax Benefits					0	0
Unrecognized tax benefits, Accrued interest or penalties					0	0
Unrecognized tax benefits, Income tax penalties and interest expenses					$ 0	$ 0
Effective income tax rate	(0.30%)	0.00%	(0.30%)	0.00%	0.00%	0.00%
Income tax expense benefit	$ (21)	$ 0	$ 53	$ 0	$ 0	$ 0
Deferred Tax Assets Operating Loss Carryforwards And Research And Development Tax Credit Carryforwards [Member]
Increase in valuation allowance					15,000
Domestic Tax Authority [Member]
Operating loss carryforwards					$ 41,000
Operating loss carryforwards expiration date					Dec. 31, 2035
Domestic Tax Authority [Member] \| Research Tax Credit Carryforward [Member]
Tax credit carryforwards					$ 3,400
Tax Credit Carryforward, Expiration Date					Dec. 31, 2034
Domestic Tax Authority [Member] \| Expires In Beginning In Two Thousand And Thirty Five [Member]
Operating loss carryforwards					$ 3,300
Domestic Tax Authority [Member] \| CarryForward Indefinitely [Member]
Operating loss carryforwards					40,500
State and Local Jurisdiction [Member]
Operating loss carryforwards					$ 39,100
Operating loss carryforwards expiration date					Dec. 31, 2035
State and Local Jurisdiction [Member] \| Research Tax Credit Carryforward [Member]
Tax credit carryforwards					$ 2,200
Tax Credit Carryforward, Expiration Date					Dec. 31, 2030

Equity Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Thousands, $ in Millions	3 Months Ended			6 Months Ended	12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Mar. 31, 2017
Share based payment arrangement, Unrecognized compensation cost					$ 3.3
Share based payment arrangement, Unrecognized compensation cost, Recognition period					2 years 10 months 2 days
Two Thousand And Seventeen Stock Option And Grant Plan [Member]
Share based payment arrangement, Shares reserved for future issuance					30,600,000			10,000,000
Share based payment arrangement, Number of shares available for grant					6,700,000	2,800,000
Two Thousand And Seventeen Plan [Member]
Share based payment arrangement, Number of shares available for grant					11,783,597
Share based payment arrangement, Award vesting percentage					25.00%
Percentage of shareholder to whom award is granted					10.00%
Percentage of estimated fair value of shares					100.00%
Adjustment percentage of estimated fair value of shares					110.00%
Two Thousand And Seventeen Plan [Member] \| Minimum [Member]
Share based payment arrangement, Award vesting period					3 years
Two Thousand And Seventeen Plan [Member] \| Maximum [Member]
Share based payment arrangement, Award vesting period					4 years
Common Stock [Member]
Share based payment arrangement,Options exercised	620,361	895,093	19,687		81,870
Share-based Payment Arrangement, Option [Member] \| Two Thousand And Seventeen Plan [Member]
Share based payment arrangement, Unrecognized compensation cost	$ 13.7			$ 13.7
Share based payment arrangement, Unrecognized compensation cost, Recognition period				3 years 1 month 6 days
Share based payment arrangement, Shares reserved for future issuance	739,618			739,618
Share based payment arrangement, Term of award					10
Share based payment arrangement,Options, Fair value of options vested during period				$ 0.3	$ 0.9	$ 0.3
Share based payment arrangement,Options, Intrinsic value of option exercised					$ 0.1
Share based payment arrangement,Options exercised				1,515,454	81,870	0
Share based payment arrangement,Options, Weighted-average grant date fair value options granted					$ 490	$ 340
Share based payment arrangement,Options expected to vest
Restricted Stock [Member] \| Two Thousand And Seventeen Plan [Member]
Share based payment arrangement, Unrecognized compensation cost					$ 0.2
Share based payment arrangement, Unrecognized compensation cost, Recognition period					5 months 4 days
Share based payment arrangement, Equity instruments other than option, Fair value of award vested during period					$ 0.5	$ 0.6
Share based payment arrangement, Term of award					10
Founder and Advisors Restricted Stock Award [Member]
Share based payment arrangement, Unrecognized compensation cost					$ 0.1
Share based payment arrangement, Unrecognized compensation cost, Recognition period					2 months 19 days
Share based payment arrangement, Equity instruments other than option, Fair value of award vested during period					$ 0.5	$ 0.5
Founder and Advisors Restricted Stock Award [Member] \| Common Stock [Member]
Share based payment arrangement, Shares issued during period							4,690,000

Equity Incentive Plans - Summary of the Company Recorded Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	$ 1,196	$ 407	$ 2,146	$ 815	$ 1,764	$ 1,694
Research and Development Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	552	230	1,012	449	1,003	817
General and Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	$ 644	$ 177	$ 1,134	$ 366	$ 761	$ 877

Equity Incentive Plans - Summary of the Stock Option Activity of the Company's Plan (Detail) - Employee Stock Option [Member] - Two Thousand And Seventeen Plan [Member] - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Beginning balance	11,952,362	6,902,873
Number of Shares Granted	8,625,312	5,716,368
Number of Shares Exercised	(1,515,454)	(81,870)	0
Number of Shares Cancelled	(158,924)	(586,009)
Number of Shares Ending balance	18,903,296	11,952,362	6,902,873
Number of Shares Options exercisable	3,864,800	3,611,387
Weighted Average Exercise Price Beginning balance	$ 0.64	$ 0.50
Weighted Average Exercise Price Granted	1.56	0.79
Weighted Average Exercise Price Exercised	0.50	0.48
Weighted Average Exercise Price Cancelled	1.22	0.51
Weighted Average Exercise Price Ending balance	1.06	0.64	$ 0.50
Weighted Average Exercise Price Options exercisable	$ 0.58	$ 0.51
Weighted Average Contractual Term	8 years 10 months 24 days	8 years 6 months 29 days	8 years 11 months 19 days
Weighted Average Contractual Term Options exercisable	7 years 10 months 13 days	7 years 7 months 24 days
Aggregate Intrinsic Value	$ 44,555,609	$ 6,625,511	$ 420,140
Aggregate Intrinsic Value Options exercisable	$ 10,973,189	$ 2,466,634

Equity Incentive Plans - Disclosure of Share Based Compensation Arrangements by Share Based Payment Award (Detail) - Common Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Founder and Advisors Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance Unvested restricted common stock outstanding, Number of shares	1,125,000	2,221,875
Beginning balance Unvested restricted common stock outstanding, Weighted Average Grant-Date Fair Value	$ 0.001	$ 0.001
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(950,000)	(987,496)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period		(109,379)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 0.001	$ 0.001
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value		$ 0.001
Ending balance Unvested restricted common stock outstanding, Number of shares		1,125,000
Ending balance Unvested restricted common stock outstanding, Weighted Average Grant-Date Fair Value		$ 0.001
Restricted Stock [Member] \| 2017 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance Unvested restricted common stock outstanding, Number of shares	2,066,034	4,888,460
Beginning balance Unvested restricted common stock outstanding, Weighted Average Grant-Date Fair Value	$ 0.33	$ 0.35
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(1,370,089)	(1,744,301)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(115,077)	(1,078,125)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 0.33	$ 0.32
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 0.08	$ 0.42
Ending balance Unvested restricted common stock outstanding, Number of shares	580,868	2,066,034
Ending balance Unvested restricted common stock outstanding, Weighted Average Grant-Date Fair Value	$ 0.38	$ 0.33

Equity Incentive Plans - Summary of the Weighted Average Assumptions Used to Estimate the Grant Date Fair Value of the Stock Options Using the Black-Scholes Option Pricing Model (Detail) - Share-based Payment Arrangement, Option [Member] - 2017 Plan [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected option life (in years)	5 years	5 years
Expected volatility	67.00%	70.00%
Risk-free interest rate	0.40%	1.60%
Maximum [Member]
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected option life (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	72.00%	75.00%
Risk-free interest rate	1.40%	2.60%

Subsequent Events - Additional Information (Detail) - USD ($)		1 Months Ended				6 Months Ended	12 Months Ended
	Apr. 13, 2021	Apr. 30, 2021	Mar. 31, 2021	Jan. 31, 2021	Apr. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Aug. 10, 2021
Share-based compensation expense, Period for recognition							2 years 10 months 2 days
Payment of stock issuance cost							$ 300,000	$ 0
Waiving rights		In April 2021, the holders of the Series A, Series B and Series B-1 redeemable preferred stock irrevocably waived their right to redeem any shares of Preferred Stock until March 31, 2023.
BCTG Acquisition Corp [Member]
Business combination, Percentage of equity interest acquired	100.00%								100.00%
Business combination consideration transferred						$ 325,600,000
Business combination,amount of consideration in the form common stock	$ 550,000,000.0
Gross proceeds received upon closing of the business combination	166,800,000
Stock issued during period shares new issues						18,600,000	18,600,000
Transaction costs and redemptions approximated amount	27,300,000					$ 27,300,000
Proceeds from financing activities,Net	325,600,000
BCTG Acquisition Corp [Member] \| PIPE Financing [Member]
Additional gross proceeds received upon closing of the financing	$ 186,100,000
Amended Gilead Agreement [Member]
Business combination,percentage of equity method investment ownership acquired							10.00%
Definitive Merger Agreement [Member] \| BCTG Acquisition Corp [Member]
Business combination, Percentage of equity interest acquired	100.00%
Business combination,percentage of equity method investment ownership acquired	100.00%
Subsequent Event [Member]
Common stock, Conversion basis	at the effective time of the merger (the “Effective Time”), each share of the Company’s redeemable convertible preferred stock “Preferred Stock” issued and outstanding immediately prior to the Effective Time shall be converted into a share of the Company’s common stock.
Common stock, Stock split	At the Effective Time, each option to purchase the Company’s common stock shall become an option, respectively, to purchase shares of common stock of the surviving entity, subject to adjustment in accordance with the exchange ratio.
Subsequent Event [Member] \| BCTG Acquisition Corp [Member]
Business combination, Percentage of equity interest acquired	100.00%
Business combination, Recognized goodwill	$ 0
Business combination, Recognized intangible assets	0
Business combination consideration transferred	156,900,000
Proceeds from private investment in public entity financing	$ 179,700,000
Subsequent Event [Member] \| Amended Gilead Agreement [Member]
License fee receivable		$ 11,000,000.0
Common Stock [Member] \| BCTG Acquisition Corp [Member] \| PIPE Financing [Member]
Stock issued during period shares new issues	18,600,000
Common Stock [Member] \| Subsequent Event [Member] \| BCTG Acquisition Corp [Member]
Stock issued during period shares, Acquisition	18,600,000
Two Thousand And Seventeen Plan [Member] \| Employee Stock Option [Member]
Share-based compensation expense, Period for recognition						3 years 1 month 6 days
Two Thousand And Seventeen Plan [Member] \| Employee Stock Option [Member] \| Subsequent Event [Member]
Share based payment arrangement, Purchase price of share			$ 2.57	$ 1.19
Share based payment arrangement, Aggregate grant date fair value of options granted			$ 1,700,000	$ 8,800,000
Share-based compensation expense, Period for recognition			3 years 9 months 18 days	3 years 9 months 18 days
Two Thousand And Seventeen Plan [Member] \| Employee Stock Option [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Share based payment arrangement, Number of shares purchased for the award			1,010,000	6,805,312
Series B Redeemable Convertible Preferred Stock [Member]
Proceeds from issuance of redeemable convertible preferred stock					$ 29,800,000
Series B Redeemable Convertible Preferred Stock [Member] \| Subsequent Event [Member]
Temporary equity, Shares issued			22,686,026
Temporary equity, Redemption price per share			$ 1.32
Proceeds from issuance of redeemable convertible preferred stock			$ 30,000,000.0			$ 30,000,000.0
Payment of stock issuance cost			$ 100,000
BTCG Common Stock [Member] \| Definitive Merger Agreement [Member] \| BCTG Acquisition Corp [Member]
Business combination,amount of consideration in the form common stock	$ 550,000,000.0