Sierra Oncology (SRRA) 10-Q 5 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 02, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Sierra Oncology, Inc.
Entity Central Index Key	0001290149
Trading Symbol	SRRA
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding		12,560,642
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, $0.001 par value
Entity File Number	001-37490
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0138994
Entity Address, Address Line One	1820 Gateway Drive, Suite 110
Entity Address, City or Town	San Mateo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94404
City Area Code	650
Local Phone Number	376-8679
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 90,690	$ 104,055
Prepaid expenses and other current assets	1,983	2,415
Total current assets	92,673	106,470
Property and equipment, net	71	52
Operating lease right-of-use assets	946	318
Other assets	687	647
TOTAL ASSETS	94,377	107,487
CURRENT LIABILITIES:
Accrued and other liabilities	7,913	7,148
Accounts payable	1,548	2,205
Total current liabilities	9,461	9,353
Operating lease liabilities	650	175
TOTAL LIABILITIES	10,111	9,528
Commitments and Contingencies (Note 7)
STOCKHOLDERS’ EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of June 30, 2021 and December 31, 2020; nil shares issued and outstanding as of June 30, 2021 and December 31, 2020
Common stock, $0.001 par value; 500,000,000 shares authorized as of June 30, 2021 and December 31, 2020; 12,358,517 and 11,128,484 shares issued and outstanding as of June 30, 2021 and December 31, 2020	12	11
Additional paid-in capital	971,388	944,537
Accumulated deficit	(887,134)	(846,589)
TOTAL STOCKHOLDERS’ EQUITY	84,266	97,959
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 94,377	$ 107,487

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	12,358,517	11,128,484
Common stock, shares outstanding	12,358,517	11,128,484

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 14,149	$ 10,189	$ 28,102	$ 21,780
General and administrative	6,424	6,260	12,289	10,804
Total operating expenses	20,573	16,449	40,391	32,584
Loss from operations	(20,573)	(16,449)	(40,391)	(32,584)
Other expense (income), net:
Changes in fair value of warrant liabilities				16,240
Other expense (income), net	48	24	77	(517)
Total other expense (income), net	48	24	77	15,723
Loss before provision for (benefit from) income taxes, net	(20,621)	(16,473)	(40,468)	(48,307)
Provision for (benefit from) income taxes, net	9	(11)	77	67
Net loss and comprehensive loss	$ (20,630)	$ (16,462)	$ (40,545)	$ (48,374)
Net loss per common share, basic and diluted	$ (1.67)	$ (1.58)	$ (3.38)	$ (4.71)
Weighted-average shares used in computing net loss per common share, basic and diluted	12,350,660	10,395,732	12,011,199	10,276,180

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Series A Convertible Voting Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2019	$ 86,345	$ 1	$ 74	$ 851,957	$ (765,687)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2019		103,000	1,867,176
Conversion of Series A convertible voting preferred stock to common stock		$ (1)	$ 8	(7)
Conversion of Series A convertible voting preferred stock to common stock, Shares		(103,000)	7,803,273
Reclassification of warrant liabilities to equity	62,175			62,175
Issuance of common stock in connection with an amendment to the asset purchase agreement	8,782		$ 1	8,781
Number of shares issued in connection with an amendment to asset purchase agreement			725,283
Issuance of warrant in connection with anamendment to the asset purchase agreement	3,188			3,188
Stock-based compensation	918			918
Reverse stock split adjustment			$ (73)	73
Net loss	(31,912)				(31,912)
Stockholders Equity, Ending Balance at Mar. 31, 2020	129,496		$ 10	927,085	(797,599)
Stockholders Equity, Ending Balance, Shares at Mar. 31, 2020			10,395,732
Stockholders Equity, Beginning Balance at Dec. 31, 2019	86,345	$ 1	$ 74	851,957	(765,687)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2019		103,000	1,867,176
Reclassification of warrant liabilities to equity	62,175
Net loss	(48,374)
Stockholders Equity, Ending Balance at Jun. 30, 2020	116,651		$ 10	930,702	(814,061)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2020			10,395,732
Stockholders Equity, Beginning Balance at Mar. 31, 2020	129,496		$ 10	927,085	(797,599)
Stockholders Equity, Beginning Balance, Shares at Mar. 31, 2020			10,395,732
Stock-based compensation	3,617			3,617
Net loss	(16,462)				(16,462)
Stockholders Equity, Ending Balance at Jun. 30, 2020	116,651		$ 10	930,702	(814,061)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2020			10,395,732
Stockholders Equity, Beginning Balance at Dec. 31, 2020	97,959		$ 11	944,537	(846,589)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2020			11,128,484
Issuance of common stock	19,632		$ 1	19,631
Issuance of common stock, Shares			1,149,820
Issuance of common stock for exercise of common stock warrants	660			660
Issuance of common stock for exercise of common stock warrant, Shares			49,995
Issuance of common stock for exercise of common stock options	288			288
Issuance of common stock for exercise of stock options, Shares			21,662
Stock-based compensation	2,931			2,931
Net loss	(19,915)				(19,915)
Stockholders Equity, Ending Balance at Mar. 31, 2021	101,555		$ 12	968,047	(866,504)
Stockholders Equity, Ending Balance, Shares at Mar. 31, 2021			12,349,961
Stockholders Equity, Beginning Balance at Dec. 31, 2020	97,959		$ 11	944,537	(846,589)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2020			11,128,484
Net loss	(40,545)
Stockholders Equity, Ending Balance at Jun. 30, 2021	84,266		$ 12	971,388	(887,134)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2021			12,358,517
Stockholders Equity, Beginning Balance at Mar. 31, 2021	101,555		$ 12	968,047	(866,504)
Stockholders Equity, Beginning Balance, Shares at Mar. 31, 2021			12,349,961
Issuance of common stock for exercise of common stock options	113			113
Issuance of common stock for exercise of stock options, Shares			8,556
Stock-based compensation	3,228			3,228
Net loss	(20,630)				(20,630)
Stockholders Equity, Ending Balance at Jun. 30, 2021	$ 84,266		$ 12	$ 971,388	$ (887,134)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2021			12,358,517

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (40,545)	$ (48,374)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	6,159	4,535
Depreciation and amortization	123	113
Changes in fair value of warrant liabilities		16,240
Securities issuance obligation		1,485
Other	21	74
Changes in operating assets and liabilities:
Prepaid expenses and other assets	310	972
Accrued, other and operating lease liabilities	623	(546)
Accounts payable	(657)	976
Deferred revenue		300
Net cash used in operating activities	(33,966)	(24,225)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(40)	(12)
Net cash used in investing activities	(40)	(12)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock from At-The-Market equity offering, net of offering costs	19,632
Proceeds from exercise of common stock warrants	660
Proceeds from exercise of common stock options	401
Net cash provided by financing activities	20,693
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	(52)	(58)
NET DECREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(13,365)	(24,295)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period	104,355	147,828
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period	90,990	123,533
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes, net	33	14
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Right-of-use asset obtained in exchange for operating lease obligation	730
Unpaid deferred financing costs in accrued and other liabilities	$ 100	15
Issuance of common stock and common stock warrant in connection with an amendment to the asset purchase agreement		11,970
Reclassification of warrant liabilities to equity		$ 62,175

Organization

Organization	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Description of Business Sierra Oncology, Inc. (together with its subsidiaries, collectively referred to as the “Company”), a Delaware corporation, is a late stage biopharmaceutical company focused on the Phase 3 execution, registration and potential commercialization of momelotinib, a novel drug that may address serious unmet needs in myelofibrosis. Momelotinib is a selective and orally bioavailable JAK1 (Janus kinase 1), JAK2 (Janus kinase 2) and ACVR1 (Activin A receptor type 1) / activin receptor-like kinase-2 (ALK2) inhibitor with a differentiated mechanism of action that enables it to potentially address all three key drivers of myelofibrosis: anemia of inflammation, constitutional symptoms and enlarged spleen. More than 1,200 subjects have received momelotinib since clinical studies began in 2009, including more than 800 patients treated for myelofibrosis. Several of these patients remain on treatment for more than 11 years. In August 2021, the Company acquired an exclusive global license from AstraZeneca AB (AstraZeneca) for AZD5153, a potent and selective bromodomain-containing protein 4 ( The Company’s portfolio also includes SRA737, a selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), an emerging target for the treatment of cancer which has a key role in the DNA Damage Response (DDR). The Company is currently focusing its resources on the development of momelotinib and exploring options to support potential future continued development of SRA737. The Company’s primary activities since inception have been conducting research and development activities, conducting preclinical and clinical testing, recruiting personnel, performing business and financial planning, identifying and evaluating additional drug candidates for potential in-licensing or acquisition, and raising capital to support development activities. Going Concern The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles applicable to a going concern, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The Company has not generated any product revenue related to its primary business purpose to date, nor has it generated any net income, and is subject to a number of risks and uncertainties, which include dependence on key individuals, the need to identify and successfully develop commercially viable products, the need to obtain regulatory approval for its products and commercialize them, and the need to obtain adequate additional financing to fund the development of its product candidates. As of June 30, 2021, the Company had $90.7 million of cash and cash equivalents. Given the Company’s projected operating requirements and its existing cash and cash equivalents, the Company is projecting insufficient liquidity to fund its operations through the next twelve months beyond the date of the issuance of these condensed consolidated financial statements. This condition raises substantial doubt about the Company’s ability to continue as a going concern. In response to this condition, management intends to seek additional funds through equity or debt financings, collaborations, licensing transactions or other sources. However, there can be no assurance that the Company will be able to complete any such transaction on acceptable terms or otherwise. Because management’s plans have not yet been finalized and are not within the Company’s control, the implementation of such plans cannot be considered probable. As a result, the Company has concluded that management’s plans do not alleviate substantial doubt about the Company’s ability to continue as a going concern. The condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission regarding interim financial reporting. Accordingly, they do not include all the information and notes required for complete financial statements and should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021. There were no significant changes to the accounting policies during the six months ended June 30, 2021 from the significant accounting policies described in Note 2 to the consolidated financial statements in the 2020 Form 10-K. The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. These unaudited condensed consolidated financial statements and related disclosure have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated results of operations for the six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 , or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited consolidated financial statements as of that date. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of stock options and the warrant issued, the fair value of the securities issuance obligation, the probability of achieving performance-based milestones of stock options, accruals such as research and development costs, and recoverability of the Company’s net deferred tax assets and related valuation allowance. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	3. Basic net loss per share is calculated by dividing net loss by the weighted-average number of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, stock options and warrants for common stock are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following shares of common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have been antidilutive: June 30, 2021 June 30, 2020 Series A warrants for common stock 7,802,241 7,802,241 Series B warrants for common stock 2,524,732 2,574,727 Options to purchase common stock 4,786,469 2,351,055 Warrants for common stock 727,122 727,122 Total potential dilutive shares 15,840,564 13,455,145 Also excluded from the calculation of diluted net loss per share are 200,000 shares of common stock issued by the Company in July 2021 under its At-The Market (ATM) program (see Note 8).

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. The Company measures and reports its cash equivalents and restricted cash at fair value. The following table sets forth the fair value of the Company’s financial assets measured on a recurring basis by level within the fair value hierarchy: June 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 88,682 $ — $ — $ 88,682 Restricted money market funds 300 — — 300 Total financial assets $ 88,982 $ — $ — $ 88,982 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 101,919 $ — $ — $ 101,919 Restricted money market funds 300 — — 300 Total financial assets $ 102,219 $ — $ — $ 102,219 Money market funds and restricted money market funds are measured at fair value on a recurring basis using quoted prices and are classified as a Level 1 input. The Company’s cash and cash equivalents, restricted cash, other current assets, accounts payable and accrued and other liabilities approximate their fair values due to their short duration. There were no transfers between Levels 1, 2 or 3 during the six months ended June 30, 2021. Prior to reclassification to equity in January 2020, the Company’s warrant liabilities and securities issuance obligation contained unobservable inputs that reflected the Company’s own assumptions in which there was little, if any, market activity at the measurement dates. Accordingly, t were measured at fair value on a recurring basis using unobservable inputs a At January 22, 2020, Warrant A and Warrant B were no longer considered to be derivative instruments. The Company remeasured the fair value of the warrant liabilities at the time of reclassification to equity using the following assumptions: Series A Warrant Series B Warrant Expected term (in years) 5.0 2.1 Expected volatility 43 % 88 % Risk-free interest rate 1.57 % 1.53 % Expected dividend yield — % — % The Company recorded a $16.2 million non-cash expense relating to the changes in fair value of warrant liabilities in other income (expense), net in the accompanying condensed consolidated statement of operations for the six months ended June 30, 2020. At January 31, 2020, the securities issuance obligation was settled by the issuance of common stock and a common stock warrant. The fair value of the common stock issuance obligation was remeasured based on the value of the common stock at the time of issuance. The fair value of the warrant issuance obligation was remeasured using the following assumptions: Warrant Issuance Obligation Expected term (in years) 5.0 Expected volatility 43 % Risk-free interest rate 1.57 % Expected dividend yield — % The Company recognized a $1.5 million non-cash research and development expense during the six months ended June 30, 2020, representing changes in fair value of the securities issuance obligation since December 31, 2019, in the condensed consolidated statement of operations.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	5. Cash and Cash Equivalents Cash and cash equivalents consist of the following: June 30, 2021 December 31, 2020 (in thousands) Cash $ 2,008 $ 2,136 Cash equivalents: Money market accounts 88,682 101,919 Total cash and cash equivalents $ 90,690 $ 104,055 The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the condensed consolidated balance sheets to the amounts shown in the condensed consolidated statements of cash flows. June 30, 2021 June 30, 2020 (in thousands) Cash and cash equivalents $ 90,690 $ 123,233 Restricted cash included in other assets 300 300 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 90,990 $ 123,533 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following: June 30, 2021 December 31, 2020 (in thousands) Prepaid software and subscription fees $ 423 $ 376 Prepaid research and development project costs 396 321 Other receivables 297 311 Prepaid insurance 241 991 Other 626 416 Total prepaid expenses and other current assets $ 1,983 $ 2,415 Property and Equipment, net Property and equipment, net consists of the following: June 30, 2021 December 31, 2020 (in thousands) Software $ 361 $ 361 Leasehold improvements 35 — Computer equipment 5 — Property and equipment, gross 401 361 Less: accumulated depreciation (330 ) (309 ) Total property and equipment, net $ 71 $ 52 Depreciation related to the Company’s property and equipment was $11,000 and $21,000 for the three and six months ended June 30, 2021, respectively and $15,000 and $28,000 for the three and six months ended June 30, 2020, respectively. Accrued and Other Liabilities Accrued and other liabilities consist of the following: June 30, 2021 December 31, 2020 (in thousands) Accrued research and development costs $ 3,016 $ 1,715 Accrued employee related costs 2,882 4,359 Accrued professional fees 1,576 774 Operating lease liabilities 356 207 Other 83 93 Total accrued and other liabilities $ 7,913 $ 7,148

Leases

Leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Leases	6. In December 2020, the Company entered into a 48-month operating lease agreement to lease office space in San Mateo, California. The lease commenced on April 30, 2021 and expires on April 30, 2025. The Company also has an operating lease agreement to lease the office space in Vancouver, Canada that expires on February 28, 2023. In December 2020, the Company entered into an agreement to sublet the entire office premises to a third party until February 27, 2023. Pursuant to the sublease agreement, the subtenant will pay base rent of $0.2 million per annum to the Company and all operating costs related to the office space. The components of lease expense, which are recorded in general and administrative expense, and related cash flows for the three and six months ended June 30, 2021 and 2020 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) Operating lease cost $ 75 $ 50 $ 118 $ 101 Short-term lease cost 6 7 13 29 81 57 131 130 Operating cash flows used for operating leases $ 58 $ 52 $ 115 $ 104 As of June 30, 2021, the weighted average remaining lease term and discount rate for the operating leases are 3.2 years and 4.9%, respectively. As of June 30, 2021, maturities of lease liability due under the lease agreements are as follows: Years Ending December 31: Operating Leases (in thousands) Remainder of 2021 $ 172 2022 402 2023 223 2024 229 2025 58 Total lease payments 1,084 Less imputed interest (78 ) Total $ 1,006 In addition to base rent, the Vancouver lease requires payment of operating costs. These costs are not included in the table above or the sublease amount.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7 . Asset Purchase Agreement In August 2018, the Company entered into an Asset Purchase Agreement with Gilead whereby the Company acquired worldwide rights to the pharmaceutical product, momelotinib, an investigational orally bioavailable JAK1, JAK2 and ACVR1/ALK2 inhibitor together with all related intellectual property rights and certain other related assets. Pursuant to the agreement, the Company made a one-time upfront payment of $3.0 million in August 2018. In October 2019, the Company entered into an amendment to the Asset Purchase Agreement in which the Company agreed to issue, subject to certain conditions, shares of common stock and a warrant to purchase common stock to Gilead in consideration for meaningfully reduced royalty rates and elimination of a near term milestone payment in the Asset Purchase Agreement. Pursuant to the amended agreement, milestone payments of up to an aggregate of $190.0 million may become payable to Gilead upon the achievement of certain regulatory and commercial milestone events and the Company is now required to pay Gilead low double-digit to high-teens percent tiered combined royalties based upon net sales. License Agreements In August 2021, the Company entered into a license agreement with AstraZeneca for an exclusive global license for AZD5153 and related compounds, which selectively inhibit BRD4. Under the agreement, the Company will have an exclusive license to develop, manufacture and commercialize AZD5153 for all therapeutic, prophylactic, palliative and diagnostic uses in humans and animals. The license agreement provides that the Company will make a one-time, non-refundable upfront cash payment of $8.0 million to AstraZeneca, that will be paid and expensed as research and development costs during the third quarter of 2021. Aggregate milestone payments of up to $208.0 million may become payable by the Company upon the achievement of certain development, regulatory and commercial milestones. In addition, the Company is required to pay AstraZeneca a tiered royalty on worldwide net sales ranging from high single-digits to low double-digits. In September 2016, the Company entered into an exclusive license agreement with CRT Pioneer Fund LP (CPF) for worldwide rights, know-how and materials to develop SRA737, a small molecule inhibitor targeting Chk1, a promising therapeutic target to treat cancer. Pursuant to the agreement, the Company made a one-time upfront payment of $7.0 million to CPF in October 2016 and paid $2.0 million to CPF in January 2017 for the successful transfer of two ongoing Phase 1 clinical trials. Pursuant to the original license agreement, additional milestone payments of up to an aggregate of $319.5 million may have become payable to CPF upon the achievement of certain milestones. In November 2020, the Company entered into an amendment to the license agreement with CPF, which amended the terms and reduced the amounts of certain future milestone payments. Pursuant to the amended agreement, future milestone payments of up to an aggregate of $290.0 million may become payable to CPF upon the achievement of certain developmental, regulatory and commercial milestones, including a milestone payment of $2.0 million upon the dosing of the first patient of the first trial of SRA737 following the effective date of the amendment. These milestones will be accrued once they are considered probable of occurring. In addition, the Company is required to pay CPF, on a product-by-product and country-by-country basis, tiered high single-digit to low double-digit royalties on the net sales of any product successfully developed. In May 2016, the Company entered into an exclusive license agreement (Carna License Agreement) with Carna Biosciences, Inc. (Carna) for worldwide rights to develop and commercialize SRA141, a small molecule kinase inhibitor targeting Cdc7. In exchange for this exclusive right, the Company paid Carna an upfront payment of $0.9 million in June 2016. In June 2020, the Company entered into a collaboration agreement (Carna Collaboration Agreement) with Carna effectively terminating the Carna License Agreement. Pursuant to the Carna Collaboration Agreement, Carna paid an upfront fee of $0.3 million, which was recognized as collaboration revenue during the year ended December 31, 2020, for the exclusive worldwide rights for SRA141 and other transition services. In addition, the Company will be entitled to single-digit royalties on product sales, on a product-by-product basis, and low to mid-teen profit share on royalty and non-royalty income. Legal From time to time, the Company may become subject to other legal proceedings, claims and litigation arising in the ordinary course of business. In addition, the Company may receive letters alleging infringement of patent or other intellectual property rights. The Company is not currently a party to any other material legal proceedings, nor is it aware of any pending or threatened litigation that, in the Company’s opinion, would have a material adverse effect on the business, operating results, cash flows or financial condition should such litigation be resolved unfavorably. COVID-19 The full extent of the impact of the COVID-19 pandemic on financial markets, economies worldwide and our business is highly uncertain. Research and development expenses and general and administrative expenses may vary significantly if there is an increased impact from COVID-19 on the costs and timing associated with the conduct of clinical trials and other related business activities. The Company is carefully monitoring the pandemic and the potential length and depth of the resulting economic impact on its financial condition and results of operations. As of June 3 0 , 202 1 , the Company was not aware of any contingencies and no related estimates were recorded on its financial statements as a result of COVID-19.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Stockholders' Equity	8 . At-The-Market Common Stock Offering In August 2020, the Company filed a prospectus supplement, pursuant to which it sold $20.0 million of its common stock in ATM offerings. In February and May 2021, the Company filed prospectus supplements pursuant to which it can issue and sell an aggregate of up to an additional $30.0 million and $50.0 million of its common stock, respectively, from time to time in ATM offerings. During the six months ended June 30, 2021, the Company sold 1,149,820 shares under the ATM program for net proceeds of $19.6 million, net of commissions and offering expenses. There were no ATM sales during the six months ended June 30, 2020. As of June 30, 2021, there was $70.2 million remaining available under the ATM program. In July 2021, the Company sold 200,000 shares of its common stock under the ATM program for proceeds of $3.9 million, net of commissions. Common Stock Reserved for Issuance The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to effect the conversion of all outstanding options granted and available for grant under the incentive plans, shares reserved for issuance under the employee stock purchase plan and issued warrants. June 30, 2021 December 31, 2020 Shares reserved under Series A warrant 7,802,241 7,802,241 Shares reserved under Series B warrant 2,524,732 2,574,727 Shares reserved for future option grants under equity plans 1,393,176 1,117,796 Outstanding stock options under equity incentive plans 4,786,469 4,146,928 Outstanding warrants 727,122 727,122 Shares reserved under the 2015 employee stock purchase plan 17,500 17,500 Total common stock reserved for issuance 17,251,240 16,386,314 Preferred Stock On November 13, 2019, the Company completed an underwritten public offering whereby it issued 103,000 shares of Series A Convertible Voting Preferred Stock together with Series A warrants and Series B warrants for a combined purchase price of $1,000. The aggregate proceeds received by the Company was $97.7 million, net of underwriting discounts and commissions and offering expenses. Each share of Series A Preferred Stock was convertible into shares of the Company’s common stock equal to the stated value of the Series A Preferred Stock of $1,000 divided by the voting conversion price of $13.20. On January 29, 2020, all shares of Series A Preferred Stock converted into 7,803,273 shares of the Company’s common stock. Common Stock Warrants In connection with the Company’s November 2019 public offering of the Series A Preferred Stock, the Company issued Series A warrants to purchase up to 7,802,241 shares of common stock at an exercise price equal to $13.20, and Series B warrants to purchase up to 2,574,727 shares of common stock at an exercise price equal to $13.20. Both Series A and Series B warrants are exercisable following stockholder approval in January 2020 of an increase in authorized common stock sufficient to allow for the exercise of the warrants, subject to certain beneficial ownership limitations. The Series A warrants will expire five years from the date they first became exercisable or on January 22, 2025 and contain a cash and/or cashless exercise provision. The Series B warrants will expire on the 75 th In connection with obligations under the amendment to the Asset Purchase Agreement (See Note 7), the Company issued to Gilead 725,283 shares of the Company’s common stock and a warrant to purchase 725,283 shares of common stock at a price per share of $13.20 on January 31, 2020. The warrant is immediately exercisable, will expire on January 31, 2025 and contains a cash and/or cashless exercise provision. In August 2018, in connection with a Loan and Security Agreement (Loan Agreement) with Silicon Valley Bank (SVB), the Company issued a warrant to SVB to purchase 1,839 of the Company’s common stock at a price per share of $ 74.80 . The warrant i s immediately exercisable, will expire on August 21, 2028 and contains a cashless exercise provision .

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9 . In the accompanying condensed consolidated statements of operations, the Company recognized stock-based compensation expense for its employees and non-employees as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) Research and development $ 1,776 $ 933 $ 3,439 $ 1,479 General and administrative 1,452 2,684 2,720 3,056 Total stock-based compensation $ 3,228 $ 3,617 $ 6,159 $ 4,535 Determination of Fair Value The fair values of the Company’s stock-based awards granted during the three and six months ended June 30, 2021 and 2020 were estimated as of the grant date using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Expected term (in years) 5.3 – 6.1 5.3 – 7.0 5.3 – 7.0 5.3 – 7.0 Expected volatility 83 – 85 % 88 – 90 % 83 – 85 % 88 – 90 % Risk-free interest rate 0.8 – 1.1 % 0.4 – 0.5 % 0.5 – 1.1 % 0.4 – 1.2 % Expected dividend rate — % — % — % — % The fair value of each stock option grant was determined by the Company on the date of grant using the methods and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment and estimation by management. Expected Term— The expected term represents the period that stock-based awards are expected to be outstanding. As the Company’s historical share option exercise is limited due to a lack of sufficient data points, and does not provide a reasonable basis upon which to estimate an expected term, the expected term is derived by using the midpoint between the weighted-average vesting term and the contractual expiration period of the stock-based award. Expected Volatility— For the three and six months ended June 30, 2021, the expected volatility is derived from using the Company’s trading history for its common stock over a period equivalent to the expected term of the stock-based awards. For the three and six months ended June 30, 2020, the expected volatility was derived from a weighted volatility using both the Company’s trading history for its common stock and the historical stock volatilities of peer public companies within its industry that are considered to be comparable to the Company’s business over a period equivalent to the expected term of the stock-based awards. Risk-Free Interest Rate— The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the stock-based awards’ expected term. Expected Dividend Rate— The expected dividend is zero as the Company has not paid nor anticipate paying any dividends on its common stock in the foreseeable future. Forfeiture Rate— The Company accounts for forfeitures when they occur. Equity Incentive Plans 2018 Equity Inducement Plan In September 2018, the Company’s Compensation Committee approved the 2018 Equity Inducement Plan (2018 Plan). The number of shares available for awards under the 2018 Plan was set to 37,500. On June 30, 2020, the Company’s Board of Directors approved an amendment to the 2018 Plan to increase the authorized number of shares available for issuance by 500,000 shares. On February 3, 2021, the Company’s Compensation Committee approved an amendment to the 2018 Plan to increase the authorized number of shares available for issuance by 500,000. 2015 Plan The 2015 Equity Incentive Plan (2015 Plan) became effective on July 14, 2015. On January 21, 2020 the Company’s stockholders approved the following amendments to the 2015 Plan: (i) increase to the authorized number of shares available for issuance by 4,312,500 shares and proportionately increase the share limit related to incentive stock options, (ii) provide limits on the total value of compensation that may be granted to any non-employee director in each calendar year, and (iii) eliminate the annual individual grant limit to reflect changes to the tax law in 2017 tax legislation. As of June 30, 2021, 5,123,736 shares were reserved for issuance under the 2015 Plan. The number of shares reserved for issuance under the 2015 Plan will increase automatically on January 1 of each calendar year 2016 through 2025 by the number of shares equal to 4% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31. The Company’s Board of Directors or Compensation Committee may reduce the amount of the increase in any particular year. The exercise price of each stock-based award issued under the 2015 Plan is required to be no less than the fair value of the Company’s common stock. The vesting and exercise provisions of options or restricted awards granted are determined individually with each grant. Stock options have a 10-year life and expire if not exercised within that period or if not exercised within three months of cessation of employment with the Company or such longer period of time as specified in the option agreement, unless modified. 2008 Plan The Company granted options under the 2008 Stock Plan (2008 Plan) until July 2015 when it was terminated as to future awards, although it continues to govern the terms of options that remain outstanding under the 2008 Plan. The 2008 Plan provided for the granting of Incentive Stock Options (ISO), nonqualified stock options and stock purchase rights. In connection with the Board of Director’s approval of the 2015 Plan, all remaining shares available for future award under the 2008 Plan were transferred to the 2015 Plan, and the 2008 Plan was terminated. A summary of activity under the 2008 Plan, 2015 Plan and 2018 Plan and related information is as follows: Options Outstanding Shares Available for Grant Number of Shares Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value of Outstanding Options (in thousands) Outstanding — December 31, 2020 1,117,796 4,146,928 $ 19.45 8.84 $ 12,227 Awards authorized 945,139 Options granted (869,460 ) 869,460 16.87 Options exercised — (30,218 ) 13.29 Options forfeited/cancelled 199,701 (199,701 ) 17.43 Outstanding — June 30, 2021 1,393,176 4,786,469 $ 19.11 8.56 $ 26,418 Exercisable — June 30, 2021 955,199 $ 39.28 6.10 $ 4,149 Vested and expected to vest — June 30, 2021 4,261,231 $ 19.96 8.48 $ 22,573 The weighted-average grant date fair values of options granted during the three and six months ended June 30, 2021 was $12.51 and $11.93 per share, and $10.14 and $8.69 per share for the three and six months ended June 30, 2020. The aggregate intrinsic value of options exercised was $47,000 and $0.2 million for the three and six months ended June 30, 2021. No options were exercised for the three and six months ended June 30, 2020. The total grant date fair values of options vested for the three and six months ended June 30, 2021 was $2.5 million and $5.9 million, and $2.2 million and $3.8 million for the three and six months ended June 30, 2020. In August 2020, the Company granted executives and employees 1,107,250 stock options with performance-based conditions. Vesting is achieved based upon the completion of pre-determined milestones. As of June 30, 2021, all of the outstanding performance-based options remain unvested. For the three and six months ended June 30, 2021, the Company has recognized approximately $0.7 million and $1.5 million in stock-based compensation expense related to the options with performance-based criteria. In May 2020, the Company entered into a separation agreement with Dr. Glover, the Company’s former President and Chief Executive Officer, in connection with his resignation. Pursuant to the separation agreement, Dr. Glover’s unvested options that would have vested during the one-year period from the date of separation accelerated and vested immediately. The vesting date of all remaining unvested options accelerated by one year, and continued to vest through December 31, 2020, per the terms of the separation agreement. Furthermore, Dr. Glover received an extension of the expiration date of his vested stock options to 75 days following the Company’s announcement of the top-line data results from its MOMENTUM clinical trial. Compensation costs relating to the vesting acceleration and the modifications to option terms was $2.2 million for the three and six months ended June 30, 2020. As of June 30, 2021, total unrecognized stock-based compensation related to unvested stock options with only service-vesting conditions was $27.3 million and are expected to be recognized over a remaining weighted-average period of 3.0 years. As of June 30, 2021, total unrecognized stock-based compensation related to unvested stock options with performance-based conditions was $6.9 million.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	1 0 . The Company did not record a provision for U.S. federal income taxes for the three and six months ended June 30, 2021 because it expects to generate a loss for the year ended December 31, 2021. The income tax provision for the three and six months ended June 30, 2021 and 2020 represented foreign taxes. The Company’s net U.S. deferred tax assets continue to be offset by a full valuation allowance.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission regarding interim financial reporting. Accordingly, they do not include all the information and notes required for complete financial statements and should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021. There were no significant changes to the accounting policies during the six months ended June 30, 2021 from the significant accounting policies described in Note 2 to the consolidated financial statements in the 2020 Form 10-K. The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. These unaudited condensed consolidated financial statements and related disclosure have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated results of operations for the six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 , or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited consolidated financial statements as of that date.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of stock options and the warrant issued, the fair value of the securities issuance obligation, the probability of achieving performance-based milestones of stock options, accruals such as research and development costs, and recoverability of the Company’s net deferred tax assets and related valuation allowance. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following shares of common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have been antidilutive: June 30, 2021 June 30, 2020 Series A warrants for common stock 7,802,241 7,802,241 Series B warrants for common stock 2,524,732 2,574,727 Options to purchase common stock 4,786,469 2,351,055 Warrants for common stock 727,122 727,122 Total potential dilutive shares 15,840,564 13,455,145

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis	The following table sets forth the fair value of the Company’s financial assets measured on a recurring basis by level within the fair value hierarchy: June 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 88,682 $ — $ — $ 88,682 Restricted money market funds 300 — — 300 Total financial assets $ 88,982 $ — $ — $ 88,982 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 101,919 $ — $ — $ 101,919 Restricted money market funds 300 — — 300 Total financial assets $ 102,219 $ — $ — $ 102,219
Schedule of Fair Value Measurement Inputs and Valuation Techniques	At January 22, 2020, Warrant A and Warrant B were no longer considered to be derivative instruments. The Company remeasured the fair value of the warrant liabilities at the time of reclassification to equity using the following assumptions: Series A Warrant Series B Warrant Expected term (in years) 5.0 2.1 Expected volatility 43 % 88 % Risk-free interest rate 1.57 % 1.53 % Expected dividend yield — % — % At January 31, 2020, the securities issuance obligation was settled by the issuance of common stock and a common stock warrant. The fair value of the common stock issuance obligation was remeasured based on the value of the common stock at the time of issuance. The fair value of the warrant issuance obligation was remeasured using the following assumptions: Warrant Issuance Obligation Expected term (in years) 5.0 Expected volatility 43 % Risk-free interest rate 1.57 % Expected dividend yield — %

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Cash and Cash Equivalents	Cash and cash equivalents consist of the following: June 30, 2021 December 31, 2020 (in thousands) Cash $ 2,008 $ 2,136 Cash equivalents: Money market accounts 88,682 101,919 Total cash and cash equivalents $ 90,690 $ 104,055
Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the condensed consolidated balance sheets to the amounts shown in the condensed consolidated statements of cash flows. June 30, 2021 June 30, 2020 (in thousands) Cash and cash equivalents $ 90,690 $ 123,233 Restricted cash included in other assets 300 300 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 90,990 $ 123,533
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following: June 30, 2021 December 31, 2020 (in thousands) Prepaid software and subscription fees $ 423 $ 376 Prepaid research and development project costs 396 321 Other receivables 297 311 Prepaid insurance 241 991 Other 626 416 Total prepaid expenses and other current assets $ 1,983 $ 2,415
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: June 30, 2021 December 31, 2020 (in thousands) Software $ 361 $ 361 Leasehold improvements 35 — Computer equipment 5 — Property and equipment, gross 401 361 Less: accumulated depreciation (330 ) (309 ) Total property and equipment, net $ 71 $ 52
Schedule of Accrued and Other Liabilities	Accrued and other liabilities consist of the following: June 30, 2021 December 31, 2020 (in thousands) Accrued research and development costs $ 3,016 $ 1,715 Accrued employee related costs 2,882 4,359 Accrued professional fees 1,576 774 Operating lease liabilities 356 207 Other 83 93 Total accrued and other liabilities $ 7,913 $ 7,148

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of Components of Lease Expense and Related Cash Flows	The components of lease expense, which are recorded in general and administrative expense, and related cash flows for the three and six months ended June 30, 2021 and 2020 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) Operating lease cost $ 75 $ 50 $ 118 $ 101 Short-term lease cost 6 7 13 29 81 57 131 130 Operating cash flows used for operating leases $ 58 $ 52 $ 115 $ 104
Schedule of Maturities Lease Liabilities under Leases Agreements	As of June 30, 2021, maturities of lease liability due under the lease agreements are as follows: Years Ending December 31: Operating Leases (in thousands) Remainder of 2021 $ 172 2022 402 2023 223 2024 229 2025 58 Total lease payments 1,084 Less imputed interest (78 ) Total $ 1,006

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to effect the conversion of all outstanding options granted and available for grant under the incentive plans, shares reserved for issuance under the employee stock purchase plan and issued warrants. June 30, 2021 December 31, 2020 Shares reserved under Series A warrant 7,802,241 7,802,241 Shares reserved under Series B warrant 2,524,732 2,574,727 Shares reserved for future option grants under equity plans 1,393,176 1,117,796 Outstanding stock options under equity incentive plans 4,786,469 4,146,928 Outstanding warrants 727,122 727,122 Shares reserved under the 2015 employee stock purchase plan 17,500 17,500 Total common stock reserved for issuance 17,251,240 16,386,314

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-based Compensation Expense for Employees and Non-employees	In the accompanying condensed consolidated statements of operations, the Company recognized stock-based compensation expense for its employees and non-employees as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) Research and development $ 1,776 $ 933 $ 3,439 $ 1,479 General and administrative 1,452 2,684 2,720 3,056 Total stock-based compensation $ 3,228 $ 3,617 $ 6,159 $ 4,535
Schedule of Estimated Grant-date Fair Value of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions	The fair values of the Company’s stock-based awards granted during the three and six months ended June 30, 2021 and 2020 were estimated as of the grant date using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Expected term (in years) 5.3 – 6.1 5.3 – 7.0 5.3 – 7.0 5.3 – 7.0 Expected volatility 83 – 85 % 88 – 90 % 83 – 85 % 88 – 90 % Risk-free interest rate 0.8 – 1.1 % 0.4 – 0.5 % 0.5 – 1.1 % 0.4 – 1.2 % Expected dividend rate — % — % — % — %
Summary of Stock-Based Compensation Activity	A summary of activity under the 2008 Plan, 2015 Plan and 2018 Plan and related information is as follows: Options Outstanding Shares Available for Grant Number of Shares Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value of Outstanding Options (in thousands) Outstanding — December 31, 2020 1,117,796 4,146,928 $ 19.45 8.84 $ 12,227 Awards authorized 945,139 Options granted (869,460 ) 869,460 16.87 Options exercised — (30,218 ) 13.29 Options forfeited/cancelled 199,701 (199,701 ) 17.43 Outstanding — June 30, 2021 1,393,176 4,786,469 $ 19.11 8.56 $ 26,418 Exercisable — June 30, 2021 955,199 $ 39.28 6.10 $ 4,149 Vested and expected to vest — June 30, 2021 4,261,231 $ 19.96 8.48 $ 22,573

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents	$ 90,690	$ 104,055	$ 123,233

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	15,840,564	13,455,145
Series A Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	7,802,241	7,802,241
Series B Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	2,524,732	2,574,727
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	4,786,469	2,351,055
Warrants for Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	727,122	727,122

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail)	1 Months Ended
	Jul. 31, 2021shares
Subsequent Event [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of common stock, Shares	200,000

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets Measured on Recurring Basis (Detail) - Fair Value Measurements Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financial Assets
Total financial assets	$ 88,982	$ 102,219
Level 1 [Member]
Financial Assets
Total financial assets	88,982	102,219
Money Market Funds [Member]
Financial Assets
Total financial assets	88,682	101,919
Money Market Funds [Member] | Level 1 [Member]
Financial Assets
Total financial assets	88,682	101,919
Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	300	300
Restricted Money Market Funds [Member] | Level 1 [Member]
Financial Assets
Total financial assets	$ 300	$ 300

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value of Financial Liabilities Assumptions (Detail)	Jan. 31, 2020yr	Jan. 22, 2020yr
Expected term [Member] | Series A Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		5
Expected term [Member] | Series B Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		2.1
Expected term [Member] | Warrant Issuance Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	5
Expected volatility [Member] | Series A Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.43
Expected volatility [Member] | Series B Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.88
Expected volatility [Member] | Warrant Issuance Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.43
Risk-free interest rate [Member] | Series A Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.0157
Risk-free interest rate [Member] | Series B Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.0153
Risk-free interest rate [Member] | Warrant Issuance Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.0157

Fair Value Measurements - Addit

Fair Value Measurements - Additonal Information (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Fair Value Disclosures [Abstract]
Changes in fair value of warrant liabilities	$ 16,240
Securities issuance obligation	$ 1,485

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Cash And Cash Equivalents [Abstract]
Cash	$ 2,008	$ 2,136
Cash equivalents:
Money market accounts	88,682	101,919
Total cash and cash equivalents	$ 90,690	$ 104,055	$ 123,233

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 90,690	$ 104,055	$ 123,233
Restricted cash included in other assets	300		300
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows	$ 90,990	$ 104,355	$ 123,533	$ 147,828

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid software and subscription fees	$ 423	$ 376
Prepaid research and development project costs	396	321
Other receivables	297	311
Prepaid insurance	241	991
Other	626	416
Total prepaid expenses and other current assets	$ 1,983	$ 2,415

Balance Sheet Components - Su_4

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 401	$ 361
Less: accumulated depreciation	(330)	(309)
Total property and equipment, net	71	52
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	361	$ 361
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation	$ 11,000	$ 15,000	$ 21,000	$ 28,000

Balance Sheet Components - Su_5

Balance Sheet Components - Summary of Accrued and Other Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development costs	$ 3,016	$ 1,715
Accrued employee related costs	2,882	4,359
Accrued professional fees	1,576	774
Operating lease liabilities	$ 356	$ 207
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherCurrentLiabilitiesMember	us-gaap:OtherCurrentLiabilitiesMember
Other	$ 83	$ 93
Total accrued and other liabilities	$ 7,913	$ 7,148

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
California [Member]
Loss Contingencies [Line Items]
Operating lease agreement term	48 months
Operating lease agreement expiration date	Apr. 30, 2025
Vancouver [Member]
Loss Contingencies [Line Items]
Operating lease agreement expiration date	Feb. 28, 2023
Sublease base rent	$ 0.2
Weighted-average remaining lease term, operating leases (Year)	3 years 2 months 12 days
Weighted-average discount rate, Operating leases	4.90%
Sublease	$ 0.3

Leases - Schedule of Components

Leases - Schedule of Components of Lease Expense and Related Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease cost	$ 75	$ 50	$ 118	$ 101
Short-term lease cost	6	7	13	29
Total Lease Cost	81	57	131	130
Operating cash flows used for operating leases	$ 58	$ 52	$ 115	$ 104

Leases - Schedule of Maturities

Leases - Schedule of Maturities Lease Liabilities under Leases Agreements (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
Remainder of 2021	$ 172
2022	402
2023	223
2024	229
2025	58
Total lease payments	1,084
Less imputed interest	(78)
Total	$ 1,006

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended		6 Months Ended
	Aug. 31, 2021	Aug. 31, 2018	Oct. 31, 2016	Jun. 30, 2016	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Nov. 30, 2020	Jan. 31, 2017
Loss Contingencies [Line Items]
Research and development					$ 14,149	$ 10,189	$ 28,102	$ 21,780
Carna Collaboration Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid				$ 900
Upfront License Fee							300
Asset Purchase Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid		$ 3,000
Aggregate milestone payment							190,000
AstraZeneca License Agreement [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment	$ 208,000
Research and development	$ 8,000
CPF License Agreements [Member]
Loss Contingencies [Line Items]
Upfront payment paid			$ 7,000
Additional milestone payment payable							319,500
CPF License Agreements [Member] | Transfer of Phase 1 Clinical Trials [Member]
Loss Contingencies [Line Items]
Milestone payment										$ 2,000
CPF License Agreements [Member] | First patient first trial post amendment [Member]
Loss Contingencies [Line Items]
Milestone payment									$ 2,000
CPF License Agreement Amendment [Member]
Loss Contingencies [Line Items]
Additional milestone payment payable							$ 290,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Nov. 13, 2019	Jul. 31, 2021	Jan. 31, 2020	Aug. 31, 2018	Jun. 30, 2021	Jun. 30, 2020	May 31, 2021	Feb. 28, 2021	Aug. 31, 2020	Jan. 29, 2020	Nov. 30, 2019
Class Of Stock [Line Items]
Issuance of common stock					$ 19,632,000
Proceeds from exercise of common stock warrants					$ 660,000
Silicon Valley Bank [Member] | Term Loans [Member] | Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Exercise price of warrants or rights				$ 74.80
Warrant expiration date				Aug. 21, 2028
Warrants issued in connection with loan				1,839
Asset Purchase Agreement Amendment [Member] | Gilead [Member]
Class Of Stock [Line Items]
Issuance of common stock, Shares			725,283
Number of securities called by warrants and rights			725,283
Exercise price of warrants or rights			$ 13.20
Warrant expiration date			Jan. 31, 2025
Series A Warrants [Member]
Class Of Stock [Line Items]
Number of securities called by warrants and rights											7,802,241
Exercise price of warrants or rights											$ 13.20
Warrant expiration date					Jan. 22, 2025
Series B Warrants [Member]
Class Of Stock [Line Items]
Number of securities called by warrants and rights											2,574,727
Issuance of common stock for exercise of common stock warrant, Shares					49,995
Exercise price of warrants or rights											$ 13.20
Warrant expiration period after specified event					75 days
Number of Warrants exercised					151,500	0
Proceeds from exercise of common stock warrants					$ 700,000
Convertible Preferred Stock And Warrants And Underwritten Follow On Offering [Member]
Class Of Stock [Line Items]
Share issued price per share	$ 1,000				$ 1,000
Proceeds from issuance of convertible preferred stock and warrants net of issuance cost	$ 97,700,000
Series A Convertible Voting Preferred Stock [Member]
Class Of Stock [Line Items]
Stock issued, shares	103,000
Share issued price per share					1,000
Preferred stock conversion price per share					$ 13.20
Preferred Stock converted into of the Company's common stock										7,803,273
Subsequent Event [Member]
Class Of Stock [Line Items]
Issuance of common stock, Shares		200,000
At-The-Market Offering [Member]
Class Of Stock [Line Items]
Issuance of common stock, Shares					1,149,820	0
Issuance of common stock					$ 19,600,000
Authorized stock issuance value remaining capacity					$ 70,200,000
At-The-Market Offering [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Issuance of common stock, Shares		200,000
Issuance of common stock		$ 3,900,000
At-The-Market Offering [Member] | Maximum [Member]
Class Of Stock [Line Items]
Common stock reserved for issuance									$ 20,000,000
Common stock reserved for issuance							$ 50,000,000	$ 30,000,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Reserved for Issuance (Detail) - shares	Jun. 30, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Total common stock reserved for future issuance	17,251,240	16,386,314
Series A Warrants [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	7,802,241	7,802,241
Series B Warrants [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	2,524,732	2,574,727
Equity Incentive Plans [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	1,393,176	1,117,796
Awards outstanding	4,786,469	4,146,928
2015 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	17,500	17,500
Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Outstanding warrants	727,122	727,122

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock-based Compensation Expense for Employees and Non-employees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 3,228	$ 3,617	$ 6,159	$ 4,535
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,776	933	3,439	1,479
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 1,452	$ 2,684	$ 2,720	$ 3,056

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Estimated Grant-date Fair Values of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, Minimum	83.00%	88.00%	83.00%	88.00%
Expected volatility, Maximum	85.00%	90.00%	85.00%	90.00%
Risk-free interest rate, Minimum	0.80%	0.40%	0.50%	0.40%
Risk-free interest rate, Maximum	1.10%	0.50%	1.10%	1.20%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 19 days	5 years 3 months 19 days	5 years 3 months 19 days	5 years 3 months 19 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	7 years	7 years	7 years

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	Feb. 03, 2021	Jan. 21, 2020	Aug. 31, 2020	May 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance					17,251,240		17,251,240		16,386,314
Total stock-based compensation					$ 3,228,000	$ 3,617,000	$ 6,159,000	$ 4,535,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Executives and employees stock options granted			1,107,250
Total stock-based compensation					700,000	$ 0	1,500,000	$ 0
Total unrecognized stock-based compensation related to unvested stock options					6,900,000		6,900,000
Service Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation related to unvested stock options					$ 27,300,000		$ 27,300,000
Weighted-average period							3 years
2018 Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance					1,037,500		1,037,500			37,500
Common shares authorized to be issued during the period	500,000							500,000
Stock option life in years							10 years
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance					5,123,736		5,123,736
Common shares authorized to be issued during the period		4,312,500
Stock option life in years							10 years
Percentage threshold of outstanding shares increased annually under the plan							4.00%
Stock option grants description							the number of shares equal to 4% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31.
2008 Plan, 2015 Plan and 2018 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares authorized to be issued during the period							945,139
Weighted-average grant date fair values of options granted					$ 12.51	$ 10.14	$ 11.93	$ 8.69
Issuance of common stock for exercise of stock options, Shares						0	30,218	0
Aggregate intrinsic value of options exercised					$ 47,000		$ 200,000
Total grant date fair value of options vested					$ 2,500,000	$ 2,200,000	$ 5,900,000	$ 3,800,000
2008 Plan, 2015 Plan and 2018 Plan [Member] | Share Based Compensation Arrangement Modification [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration period after specified event				75 days
Compensation costs relating to vesting acceleration and modification						$ 2,200,000		$ 2,200,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Activity (Detail) - 2008 Plan, 2015 Plan and 2018 Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Options Outstanding, Shares Available for Grant
Shares Available for Grant, Beginning balance		1,117,796
Shares Available for Grant, Awards authorized		945,139
Shares Available for Grant, Granted		(869,460)
Shares Available for Grant, forfeited/cancelled		199,701
Shares Available for Grant, Ending balance		1,393,176		1,117,796
Options Outstanding, Number of Shares Outstanding
Number of Shares Outstanding, Beginning balance		4,146,928
Number of Shares Outstanding, Options granted		869,460
Number of Shares Outstanding, Options exercised	0	(30,218)	0
Number of Shares Outstanding, Options forfeited/cancelled		(199,701)
Number of Shares Outstanding, Ending balance		4,786,469		4,146,928
Number of Shares Outstanding, Exercisable		955,199
Number of Shares Outstanding, Vested and expected to vest		4,261,231
Options Outstanding, Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance		$ 19.45
Weighted-Average Exercise Price Per Share, Options granted		16.87
Weighted-Average Exercise Price Per Share, Options exercised		13.29
Weighted-Average Exercise Price Per Share, Options forfeited/cancelled		17.43
Weighted-Average Exercise Price Per Share, Ending balance		19.11		$ 19.45
Weighted-Average Exercise Price Per Share, Exercisable		39.28
Weighted-Average Exercise Price Per Share, Vested and expected to vest		$ 19.96
Options Outstanding, Weighted-Average Remaining Contractual Term (Years)
Weighted-Average Remaining Contractual Term (Years)		8 years 6 months 21 days		8 years 10 months 2 days
Weighted-Average Remaining Contractual Term (Year), Exercisable		6 years 1 month 6 days
Weighted-Average Remaining Contractual Term (Year), Vested and expected to vest		8 years 5 months 23 days
Options Outstanding, Aggregate Intrinsic Value of Outstanding Options
Aggregate Intrinsic Value of Outstanding Options		$ 26,418		$ 12,227
Aggregate Intrinsic Value of Outstanding Options, Exercisable		4,149
Aggregate Intrinsic Value of Outstanding Options, Vested and expected to vest		$ 22,573

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Federal income tax provision, continuing operations	$ 0	$ 0