Viracta Therapeutics (VIRX) S-4/A 12 Jan 21 Registration of securities issued in business combination transactions (amended) Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2020
Cover [Abstract]
Document Type	S-4/A
Entity Registrant Name	SUNESIS PHARMACEUTICALS INC
Entity Filer Category	Non-accelerated Filer
Entity Central Index Key	0001061027
Amendment Flag	false
Entity Small Business	true
Entity Emerging Growth Company	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents		$ 26,048	$ 12,761	$ 13,696
Restricted cash		0	5,500	0
Marketable securities		0	16,364	0
Prepaids and other current assets		1,576	1,697	1,504
Total current assets		27,624	36,322	15,200
Property and equipment, net		0	3	11
Operating lease right-of-use asset		409	817	0
Other assets		0	98	113
Total assets		28,033	37,240	15,324
Current liabilities:
Accounts payable		150	791	1,393
Accrued clinical expense		380	521	500
Accrued compensation		901	985	943
Other accrued liabilities		1,727	1,109	1,091
Notes payable		0	5,465	7,396
Operating lease liability—current		409	545	0
Total current liabilities		3,567	9,416	11,323
Other liabilities		0	9	8
Operating lease liability—long term		0	272	0
Total liabilities		3,567	9,697	11,331
Commitments and contingencies			15,324	15,324
Stockholders' equity:
Convertible preferred stock		5,545	11,769	20,998
Common stock		2	1	0
Additional paid-in capital		718,522	698,572	642,464
Accumulated other comprehensive income		0	1	0
Accumulated deficit		(699,603)	(682,800)	(659,469)
Total stockholders' equity	[1]	24,466	27,543	3,993
Total liabilities and stockholders' equity		$ 28,033	$ 37,240	$ 15,324
[1]	The condensed consolidated statement of stockholders’ equity has been adjusted to give retroactive effect to the Reverse Split for all periods presented.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	20	18
Preferred stock, shares outstanding	20	18
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000	400,000
Common stock, shares issued	11,139	3,747
Common stock, shares outstanding	11,139	3,747

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019	Dec. 31, 2019		Dec. 31, 2018
Revenue:
License and other revenue					$ 120			$ 2,073		$ 237
Type of Revenue [Extensible List]					snss:LicenseAndOtherRevenueMember		snss:LicenseAndOtherRevenueMember	snss:LicenseAndOtherRevenueMember		snss:LicenseAndOtherRevenueMember
Operating expenses:
Research and development		$ 2,157	$ 3,534	[1]	$ 10,128		$ 10,465	$ 15,412		$ 14,615
General and administrative		2,315	2,507	[1]	6,607		7,469	9,949		11,332
Total operating expenses		4,472	6,041	[1]	16,735		17,934	25,361		25,947
Loss from operations		(4,472)	(6,041)	[1]	(16,615)		(17,934)	(23,288)		(25,710)
Interest expense		(167)	(71)	[1]	(302)		(443)	(514)		(1,154)
Other income, net		1	170	[1]	114		334	472		249
Net loss	[1]	(4,638)	(5,942)		(16,803)		(18,043)	(23,330)		(26,615)
Unrealized loss on available-for-sale securities			0	[1]	(1)	[2]		1	[2]	7	[2]
Comprehensive loss		(4,638)	(5,942)	[1]	(16,804)		(18,043)	(23,329)		(26,608)
Basic and diluted loss per common share:
Net loss	[1]	$ (4,638)	$ (5,942)		$ (16,803)		$ (18,043)	$ (23,330)		$ (26,615)
Shares used in computing net loss per common share	[1]	15,929	10,507		12,748		7,897	8,712		3,558
Net loss per common share	[1]	$ (0.29)	$ (570)		$ (1.32)		$ (2.28)	$ (2,680)		$ (7,480)
[1]	Share and per-share data in the condensed consolidated statement of operations and comprehensive loss have been adjusted to give retroactive effect to the Reverse Split for all periods presented.
[2]	The condensed consolidated statement of stockholders’ equity has been adjusted to give retroactive effect to the Reverse Split for all periods presented.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total		Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2017	[1]	$ 21,544		$ 20,966	$ 0	$ 633,439	$ (7)	$ (632,854)
Beginning Balance, shares at Dec. 31, 2017	[1]			18,000	3,429,000
Issuance of common stock from vesting of restricted stock awards	[1]	83				83
Issuance of common stock from vesting of restricted stock awards, shares	[1]				2,000
Adjustment to issuance cost related to common stock, preferred stock, and warrants issued in prior year	[1]	126		$ 32		94
Issuance of common stock through controlled equity offering facilities, net of issuance cost	[1]	5,991				5,991
Issuance of common stock through controlled equity offering facilities, net of issuance cost, shares	[1]				301,000
Issuance of common stock under employee stock purchase plans	[1]	$ 139				139
Issuance of common stock under employee stock purchase plans, shares		10,410,000			10,000
Issuance of common stock pursuant to stock option exercises	[1]	$ 164				164
Issuance of common stock pursuant to stock option exercises, shares	[1]				5,000
Stock-based compensation expenses	[1]	2,554				2,554
Net loss		(26,615)	[2]					(26,615)
Unrealized gain on available-for-sale securities	[1]	7					7
Ending Balance at Dec. 31, 2018	[1]	3,993		$ 20,998	$ 0	642,464	0	(659,469)
Ending Balance, shares at Dec. 31, 2018	[1]			18,000	3,747,000
Issuance of common and preferred stock in underwritten offering, net of issuance costs	[1]	44,568		$ 12,527	$ 1	32,040
Issuance of common and preferred stock in underwritten offering, net of issuance costs, shares	[1]			25,000	6,133,000
Conversion of preferred stock to common stock	[1]			$ (21,762)		21,762
Conversion of preferred stock to common stock, shares	[1]			(23,000)	1,195,000
Issuance of common stock from vesting of restricted stock awards	[1]	54				54
Issuance of common stock from vesting of restricted stock awards, shares	[1]				11,000
Issuance of common stock through controlled equity offering facilities, net of issuance cost	[1]	464				464
Issuance of common stock through controlled equity offering facilities, net of issuance cost, shares	[1]				40,000
Issuance of common stock under employee stock purchase plans	[1]	36				36
Issuance of common stock under employee stock purchase plans, shares	[1]				6,000
Stock-based compensation expenses	[1]	1,222				1,222
Net loss		(18,043)	[2]					(18,043)
Ending Balance at Sep. 30, 2019	[1]	32,294		$ 11,763	$ 1	698,042		(677,512)
Ending Balance, shares at Sep. 30, 2019	[1]			20,000	11,132,000
Beginning Balance at Dec. 31, 2018	[1]	3,993		$ 20,998	$ 0	642,464	0	(659,469)
Beginning Balance, shares at Dec. 31, 2018	[1]			18,000	3,747,000
Issuance of common and preferred stock in underwritten offering, net of issuance costs	[1]	44,604		$ 12,533	$ 1	32,070
Issuance of common and preferred stock in underwritten offering, net of issuance costs, shares	[1]			25,000	6,133,000
Conversion of preferred stock to common stock	[1]			$ (21,762)		21,762
Conversion of preferred stock to common stock, shares	[1]			(23,000)	1,195,000
Issuance of common stock from vesting of restricted stock awards	[1]	54				54
Issuance of common stock from vesting of restricted stock awards, shares	[1]				11,000
Issuance of common stock through controlled equity offering facilities, net of issuance cost	[1]	464				464
Issuance of common stock through controlled equity offering facilities, net of issuance cost, shares	[1]				40,000
Issuance of common stock under employee stock purchase plans	[1]	$ 63				63
Issuance of common stock under employee stock purchase plans, shares		13,332,000			13,000
Stock-based compensation expenses	[1]	$ 1,695				1,695
Net loss	[2]	(23,330)
Net loss | Accounting Standards Update 2018-07 [Member]		(23,331)	[1],[2]					(23,331)
Unrealized gain on available-for-sale securities	[1]	1					1
Ending Balance at Dec. 31, 2019	[1]	27,543		$ 11,769	$ 1	698,572	1	(682,800)
Ending Balance, shares at Dec. 31, 2019	[1]			20,000	11,139,000
Beginning Balance at Jun. 30, 2019	[1]	11,739		$ 7,113	$ 1	676,195		(671,570)
Beginning Balance, shares at Jun. 30, 2019	[1]			12,000	7,299,000
Issuance of common and preferred stock in underwritten offering, net of issuance costs	[1]	26,032		$ 4,650		21,382
Issuance of common and preferred stock in underwritten offering, net of issuance costs, shares	[1]			8,000	3,833,000
Stock-based compensation expenses	[1]	465				465
Net loss		(5,942)	[2]					(5,942)
Unrealized gain on available-for-sale securities	[2]	0
Ending Balance at Sep. 30, 2019	[1]	32,294		$ 11,763	$ 1	698,042		(677,512)
Ending Balance, shares at Sep. 30, 2019	[1]			20,000	11,132,000
Beginning Balance at Dec. 31, 2019	[1]	27,543		$ 11,769	$ 1	698,572	1	(682,800)
Beginning Balance, shares at Dec. 31, 2019	[1]			20,000	11,139,000
Issuance of common and preferred stock in underwritten offering, net of issuance costs	[1]	12,598			$ 1	12,597
Issuance of common and preferred stock in underwritten offering, net of issuance costs, shares	[1]				6,000,000
Conversion of preferred stock to common stock	[1]			$ (6,224)		6,224
Conversion of preferred stock to common stock, shares	[1]			(10,000)	947,000
Issuance of common stock under employee stock purchase plans	[1]	23				23
Issuance of common stock under employee stock purchase plans, shares	[1]				7,000
Stock-based compensation expenses	[1]	1,106				1,106
Net loss		(16,803)	[2]					(16,803)
Unrealized gain on available-for-sale securities	[1]	(1)					$ (1)
Ending Balance at Sep. 30, 2020	[1]	24,466		$ 5,545	$ 2	718,522		(699,603)
Ending Balance, shares at Sep. 30, 2020	[1]			10,000	18,093,000
Beginning Balance at Jun. 30, 2020	[1]	16,106		$ 11,769	$ 1	699,301		(694,965)
Beginning Balance, shares at Jun. 30, 2020	[1]			20,000	11,146,000
Issuance of common and preferred stock in underwritten offering, net of issuance costs	[1]	12,598			$ 1	12,597
Issuance of common and preferred stock in underwritten offering, net of issuance costs, shares	[1]				6,000,000
Conversion of preferred stock to common stock	[1]			$ (6,224)		6,224
Conversion of preferred stock to common stock, shares	[1]			(10,000)	947,000
Stock-based compensation expenses	[1]	400				400
Net loss		(4,638)	[2]					(4,638)
Ending Balance at Sep. 30, 2020	[1]	$ 24,466		$ 5,545	$ 2	$ 718,522		$ (699,603)
Ending Balance, shares at Sep. 30, 2020	[1]			10,000	18,093,000
[1]	The condensed consolidated statement of stockholders’ equity has been adjusted to give retroactive effect to the Reverse Split for all periods presented.
[2]	Share and per-share data in the condensed consolidated statement of operations and comprehensive loss have been adjusted to give retroactive effect to the Reverse Split for all periods presented.

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement Of Stockholders' Equity [Abstract]
Issuance of common stock	$ 38,000
Issuance of preferred stock	10,000
Issuance of common stock, preferred stock, issuance cost	3,400
Issuance of common stock through controlled equity offering facilities	473	$ 6,068
Issuance of common stock through controlled equity offering facilities, issuance costs	$ 9	$ 77

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	[1]	$ (16,803)	$ (18,043)	$ (23,330)	$ (26,615)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense		1,106	1,276	1,749	2,637
Accretion of investment discounts and depreciation		(41)	6	(70)	9
Amortization of debt discount and debt issuance costs		35	112	116	192
Changes in operating assets and liabilities:
Prepaids and other assets		219	(721)	(294)	1,063
Accounts payable		(641)	(623)	(602)	(304)
Accrued clinical expense		(141)	44	21	(267)
Accrued compensation		(84)	234	42	(497)
Other accrued liabilities		574	(722)	183	(622)
Net cash used in operating activities		(15,776)	(18,437)	(22,185)	(24,404)
Cash flows from investing activities
Purchases of marketable securities		(747)	(13,080)	(20,035)
Proceeds from maturities of marketable securities		17,154	0	3,750	4,780
Net cash provided by (used in) investing activities		16,407	(13,080)	(16,285)	4,780
Cash flows from financing activities
Proceeds from notes payable, net of issuance cost		0	5,453	5,453
Principal payments on notes payable		(5,500)	(7,500)	(7,500)
Proceeds from issuance of convertible preferred stock offering, net		0	12,533	12,533
Proceeds from issuance of common stock, net		12,633	32,068	32,022
Proceeds from issuance of common stock through controlled equity offering facilities, net		0	464	464	6,040
Proceeds from exercise of stock options and stock purchase rights		23	36	63	303
Net cash provided by financing activities		7,156	43,054	43,035	6,343
Net increase in cash, cash equivalents and restricted cash		7,787	11,537	4,565	(13,281)
Cash, cash equivalents and restricted cash at beginning of period		18,261	13,696	13,696	26,977
Cash, cash equivalents and restricted cash at end of period		26,048	25,233	18,261	13,696
Supplemental disclosure of cash flow information
Interest paid				695	790
Supplemental disclosure of non-cash investing and financing activities
Conversion of preferred stock to common stock		6,224	21,762	21,762
Right-of-use assets obtained in exchange for new operating lease liabilities		0	1,362	$ 1,362
Commitment shares issued as cost of equity financing					448
Legal expenses accrued as cost of equity financing		$ 35	$ 33		$ 39
[1]	Share and per-share data in the condensed consolidated statement of operations and comprehensive loss have been adjusted to give retroactive effect to the Reverse Split for all periods presented.

Company Overview

Company Overview	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Overview	1. Company Overview Description of Business Sunesis Pharmaceuticals, Inc. (“Sunesis” or the “Company”) is a biopharmaceutical company focused on the development of novel targeted inhibitors for the treatment of hematologic and solid cancers. The Company’s primary activities since incorporation have been conducting research and development internally and through corporate collaborators, in-licensing out-licensing The Company is developing SNS-510, SNS-510 SNS-510 ™ SNS-510. SNS-510 SNS-510 BCL-2 SNS-510 The Company’s second program is vecabrutinib, a selective non-covalent non-covalent B-cell BTK-inhibitor In July 2020, the Company announced a reduction in workforce of approximately 30% of its headcount to focus on development of its PDK1 inhibitor SNS-510. Liquidity and Going Concern The Company has incurred significant losses and negative cash flows from operations since its inception, and as of September 30, 2020, the Company had cash and cash equivalents totaling $26.0 million and an accumulated deficit of $699.6 million. The Company expects to continue to incur significant losses for the foreseeable future as it continues development of its kinase inhibitor pipeline, including its PDK1 inhibitor, SNS-510. The Company’s cash and cash equivalents are not sufficient to support its operations for a period of twelve months from the date these condensed consolidated financial statements are available to be issued. These factors raise substantial doubt about its ability to continue as a going concern. The Company will require additional financing to fund working capital and pay its obligations as they come due. Additional financing might include one or more offerings and one or more of a combination of equity securities, debt arrangements or partnership or licensing collaborations. However, there can be no assurance that the Company will be successful in acquiring additional funding at levels sufficient to fund its operations or on terms favorable to the Company. Additionally, the continued spread of COVID-19 Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk generally consist of cash and cash equivalents. The Company is exposed to credit risk in the event of default by the institutions holding its cash and cash equivalents to the extent of the amounts recorded in the condensed consolidated balance sheets.	1. Company Overview Description of Business Sunesis Pharmaceuticals, Inc. (“Sunesis” or the “Company”) is a biopharmaceutical company focused on the development of novel targeted inhibitors for the treatment of hematologic and solid cancers. The Company’s primary activities since incorporation have been conducting research and development internally and through corporate collaborators, in-licensing out-licensing The Company’s lead program is vecabrutinib, a selective non-covalent B-cell Vecabrutinib is being studied in a Phase 1b/2 clinical trial to assess safety and activity in patients with CLL and other advanced B-cell The Company is developing SNS-510, in-licensed SNS-510 In December 2019, the Company consented to Takeda Oncology’s assignment of TAK-580 Therapeutics-1, (“DOT-1”), DOT-1 DOT-1 TAK-580. DOT-1 pre-commercialization, TAK-580. In December 2019, Sumitomo Dainippon Pharma Co., Ltd. (“Sumitomo”) assigned to Sunesis worldwide rights to vosaroxin. The Company entered into an agreement to license vosaroxin to Denovo Biopharma, LLC (“Denovo”), pursuant to which Sunesis received a $200,000 upfront payment and is eligible to receive up to $57.0 million in regulatory and commercial milestones, and double-digit royalties on future sales of vosaroxin. Liquidity and Going Concern The Company has incurred significant losses and negative cash flows from operations since its inception, and as of December 31, 2019, had cash and cash equivalents, restricted cash, and marketable securities totaling $34.6 million and an accumulated deficit of $682.8 million. The Company expects to continue to incur significant losses for the foreseeable future as it continues development of its kinase inhibitor pipeline, including its BTK inhibitor, vecabrutinib. The Company has prioritized development funding on its kinase inhibitor portfolio with a focus on vecabrutinib. The Company has product candidates that are still in the early stages of development and will require significant additional investment. The Company’s cash and cash equivalents, restricted cash, and marketable securities are not sufficient to support its operations for a period of twelve months from the date these consolidated financial statements are available to be issued. These factors raise substantial doubt about its ability to continue as a going concern. The Company will require additional financing to fund working capital, repay debt and pay its obligations as they come due. Additional financing might include one or more offerings and one or more of a combination of equity securities, debt arrangements or partnership or licensing collaborations. However, there can be no assurance that the Company will be successful in acquiring additional funding at levels sufficient to fund its operations or on terms favorable to the Company. If the Company is unsuccessful in its efforts to raise additional financing in the near term, the Company will be required to significantly reduce or cease operations. The principal payments due under the SVB Loan Agreement (as defined in Note 7) have been classified as a current liability as of December 31, 2019 due to the considerations discussed above and the assessment that the material adverse change clause under the SVB Loan Agreement is not within the Company’s control. The SVB Loan Agreement also contains customary events of default, including among other things, the Company’s failure to make principal or interest payments when due, the occurrence of certain bankruptcy or insolvency events or its breach of the covenants under the SVB Loan Agreement. Upon the occurrence of an event of default (as defined in Note 7), SVB may, among other things, accelerate the Company’s obligations under the SVB Loan Agreement. The Company has not been notified of an event of default by SVB as of the date of the filing of this Form 10-K. Concentrations of Credit Risk In accordance with its investment policy, the Company invests cash that is not currently being used for operational purposes. The policy allows for the purchase of low risk debt securities issued by: (a) the United States and certain European governments and government agencies, and (b) highly rated banks and corporations, denominated in U.S. dollars, Euros, or British pounds, subject to certain concentration limits. The policy limits maturities of securities purchased to no longer than 24 months and the weighted average maturity of the portfolio to 12 months. Management believes these guidelines ensure both the safety and liquidity of any investment portfolio the Company may hold. Financial instruments that potentially subject the Company to concentrations of credit risk generally consist of cash and cash equivalents, restricted cash and marketable securities. The Company is exposed to credit risk in the event of default by the institutions holding its cash and cash equivalents, restricted cash and any marketable securities to the extent of the amounts recorded in the balance sheets.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q Rule 10-01 S-X. Form 10-K Reverse Stock Split On September 2, 2020, the Company effected a one-for-ten non-voting per-share Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments available-for-sale 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments 2019-05, Financial Instruments—Credit Losses, Topic 326 2016-13. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. 2019-12 In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other options (Subtopic 470-20) 815-40). 2020-06 Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Malta) Ltd., a Malta corporation. All intercompany balances and transactions have been eliminated in consolidation. Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to valuation of marketable securities, equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting. Cash Equivalents The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds, repurchase agreements, and corporate debt securities. Fair Value Measurements The Company measures cash equivalents at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1—Observable input such as quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date; Level 2—inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly for the asset or liability. These include quoted prices for similar assets or liabilities in active markets; and Level 3—unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company’s Level 2 valuations of marketable securities, if any, are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3, if any. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of September 30, 2020 and December 31, 2019.	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). Adopted Accounting Pronouncements In August 2016, the FASB issued ASU No. 2016-15, zero-coupon In February 2016, the FASB issued ASU No. 2016-02, right-of-use 2018-10, 2018-11, 2019-01, The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease right-of-use right-of-use In June 2018, the FASB issued ASU No. 2018-07, Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments available-for-sale 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments 2019-05, Financial Instruments—Credit Losses, Topic 326 2016-13. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses. 2019-10 2019-11 2016-13. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. 2019-12 Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Malta) Ltd., a Malta corporation. All intercompany balances and transactions have been eliminated in consolidation. Segment Reporting Management has determined that the Company operates as a single reportable segment. Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of marketable securities, equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting. Cash Equivalents and Marketable Securities The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds, repurchase agreements, and corporate debt securities. Restricted cash consists of amounts pledged as collateral for term loan agreement as contractually required by the lender. Marketable securities consist of securities with original maturities of greater than three months, which may include U.S. and European government obligations and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company generally classifies its entire investment portfolio as available-for-sale. available-for-sale Available-for-sale The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in other income, net in the statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to significant exchange gains or losses as currencies fluctuate from quarter to quarter. As of December 31, 2019 and December 31, 2018, the Company held investments denominated in Euros with an aggregate fair value of zero, and $0.8 million, respectively. Any cash, cash equivalent and short-term investment balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are both recorded in other income, net in the statements of operations and comprehensive loss. Fair Value Measurements The Company measures cash equivalents and marketable securities at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - Observable input such as quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date; Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly for the asset or liability. These include quoted prices for similar assets or liabilities in active markets; and Level 3 - unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3, if any. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, deferred revenue, and notes payable approximated their fair value as of December 31, 2019 and December 31, 2018. Leases The Company determines if an arrangement is or contains a lease at inception. In determining whether an arrangement is a lease, the Company considers whether (1) explicitly or implicitly identified assets have been deployed in the arrangement and (2) the Company obtains substantially all of the economic benefits from the use of that underlying asset and directs how and for what purpose the asset is used during the term of the contract. ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. When an implicit rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at commencement date for new leases or effective date for existing leases, in determining the present value of lease payments. Leases may contain initial periods of free rent and/or periodic escalations. When such items are included in a lease agreement, the Company records rent expense on a straight-line basis over the initial term of a lease. The difference between the rent payment and the straight-line rent expense is recorded as a deferred rent liability. The Company expenses any additional payments under its operating leases for taxes, insurance or other operating expenses as incurred Accounting for Notes Payable The accounting for certain fees and expenses related to the SVB Loan Agreement (see Note 8) is as follows. The debt issuance cost is being accounted for as a debt discount and classified within notes payable on the Company’s balance sheet. The debt discount is being amortized as interest expense over the term of the loan using the effective interest method. The final payment is being accreted as interest expense over the term of the loans using the effective interest method. Revenue Recognition On January 1, 2018, the Company adopted Topic 606, Revenue from Contracts with Customers Revenue Recognition Adoption of the new standard did not result in any change to the Company’s opening retained earnings as of January 1, 2018 as no cumulative impact to the adoption of ASC 606 was noted as a result of the Company’s assessment of the comparative revenue recognized since inception of the contracts under the new revenue standard ASC 606 and historic standard ASC 605. The Company is applying the practical exemption allowed under ASC 606 and does not disclose the value of variable consideration that is a sale-based royalty promised in exchange for a license of intellectual property. The adoption of the new standard resulted in changes to the Company’s accounting policies for revenue recognition as detailed below: The Company’s contracts consist license, milestone and royalty payments primarily generated through agreements with strategic partners for the development and commercialization of the Company’s product candidates. The terms of the agreement typically include non-refundable Non-refundable In determining the appropriate amount of revenue to be recognized as it fulfills its performance obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Licenses of intellectual property: non-refundable, up-front non-refundable, up-front Event-based or milestone payments: Royalties: Research and Development Research and development expense consists primarily of: (a) clinical trial costs, which include payments for work performed by contract research organizations (“CROs”), clinical trial sites, labs and other clinical service providers, and for drug packaging, storage and distribution; (b) drug manufacturing costs, which include costs for producing drug substance and drug product, and for stability and other testing; (c) personnel costs for related permanent and temporary employees; (d) other outside services and consulting costs; and (e) payments under license agreements. All research and development costs are expensed as they are incurred. Clinical Trial Accounting The Company records accruals for estimated clinical trial costs, which include payments for work performed by CROs and participating clinical trial sites. These costs are generally a significant component of research and development expense. Costs incurred for setting up clinical trial sites for participation in trials are generally non-refundable, Warrants for Shares of Common Stock The Company accounts for warrants for shares of common stock as equity instruments in the accompanying balance sheets at their fair value on the date of issuance because such warrants are indexed to the Company’s common stock and no cash settlement is required except for (i) liquidation of the Company, or (ii) a change in control in which the common stockholders also receive cash. Stock-Based Compensation The Company grants options to purchase common stock to its employees, directors and consultants under its stock option plans. Under the Company’s Employee Stock Purchase Plan, eligible employees can also purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock at the beginning of a 12-month six-month The Company values these share-based awards using the Black-Scholes option valuation model (the “Black-Scholes model”). The determination of fair value of share-based payment awards on the date of grant using the Black-Scholes model is affected by the Company’s stock price as well as assumptions regarding a number of subjective variables. These variables include, but are not limited to, the expected stock price volatility over the term of the awards and actual and projected employee stock option exercise behaviors. The Company accounts for forfeitures of share-based payment awards as they occur. Foreign Currency Transactions that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date. Any foreign currency-denominated monetary assets and liabilities are subsequently remeasured at current exchange rates as of each balance sheet date, with gains or losses on foreign exchange recognized in other income, net in the statements of operations and comprehensive loss. Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the differences between the tax basis of assets and liabilities and their basis for financial reporting. Deferred tax assets or liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to recognize interest charges and penalties in other income, net in the statements of operations and comprehensive loss.

Loss per Common Share

Loss per Common Share	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Earnings Per Share [Abstract]
Loss per Common Share	3. Loss per Common Share Basic loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted loss per common share is computed by dividing (a) net loss, by (b) the weighted-average number of common shares outstanding for the period plus dilutive potential common shares as determined using the treasury stock method for options and warrants to purchase common stock. The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): Three and Nine September 30, 2020 2019 Warrants to purchase shares of common stock 21 22 Convertible preferred stock 1,025 1,971 Options to purchase shares of common stock 757 500 Outstanding securities not included in calculations 1,803 2,493	3. Loss per Common Share Basic loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per common share is computed by dividing (a) net loss, less any anti-dilutive amounts recorded during the period, by (b) the weighted-average number of common shares outstanding for the period plus dilutive potential common shares as determined using the treasury stock method for options and warrants to purchase common stock. The following table sets forth the computation of basic and diluted loss per common share for the periods presented (in thousands, except per share amounts): Year Ended December 31, 2019 2018 Numerator: Net loss—basic and diluted $ (23,330 ) $ (26,615 ) Denominator: Weighted-average common shares outstanding—basic and diluted 8,712 3,558 Net loss per common share: Basic and Diluted $ (2.68 ) $ (7.48 ) The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): As of December 31, 2019 2018 Warrants to purchase shares of common stock 22 22 Convertible preferred stock 1,971 633 Options to purchase shares of common stock 516 416 Outstanding securities not included in calculations 2,509 1,071

Financial Instruments

Financial Instruments	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Financial Instruments	4. Financial Instruments Financial Assets The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated (in thousands): September 30, 2020 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds—classified as cash equivalents Level 1 $ 24,503 $ — $ — $ 24,503 December 31, 2019 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds Level 1 $ 3,495 $ — $ — $ 3,495 U.S. Treasury securities Level 1 1,594 1 — 1,595 Repurchase agreements Level 2 5,000 — — 5,000 U.S. corporate debt obligations Level 2 5,155 — — 5,155 U.S. commercial paper Level 2 11,412 — — 11,412 Total available-for-sale 26,656 1 — 26,657 Less amounts classified as cash equivalents (10,293 ) — — (10,293 ) Amounts classified as marketable securities $ 16,363 $ 1 $ — $ 16,364 There were no available-for-sale available-for-sale Available-for-sale	4. Financial Instruments Financial Assets The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated, which were comprised solely of available-for-sale December 31, 2019 Valuation Amortized Gross Gross Estimated Fair Money market funds Level 1 $ 3,495 $ — $ — $ 3,495 U.S. Treasury securities Level 1 1,594 1 — 1,595 Repurchase agreements Level 2 5,000 — — 5,000 U.S. corporate debt obligations Level 2 5,155 — — 5,155 U.S. commercial paper Level 2 11,412 — — 11,412 Total available-for-sale 26,656 1 — 26,657 Less amounts classified as cash equivalents (10,293 ) — — (10,293 ) Amounts classified as marketable securities $ 16,363 $ 1 $ — $ 16,364 December 31, 2018 Valuation Amortized Gross Gross Estimated Fair Money market funds Level 1 $ 10,845 $ — $ — $ 10,845 Total available-for-sale 10,845 — — 10,845 Less amounts classified as cash equivalents (10,845 ) — — (10,845 ) Amounts classified as marketable securities $ — $ — $ — $ — There were no available-for-sale No significant facts or circumstances have arisen to indicate that there has been any deterioration in the creditworthiness of the issuers of these securities. There were no realized gains or losses on the available-for-sale available-for-sale

Other Accrued Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Other Accrued Liabilities	5. Other Accrued Liabilities Other accrued liabilities as of December 31 were as follows (in thousands): 2019 2018 Accrued outside services $ 690 $ 556 Accrued professional services 220 251 Accrued interest 57 284 Deferred revenue 120 — Other accruals 22 — Total other accrued liabilities $ 1,109 $ 1,091

License Agreements

License Agreements	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
License Agreements	5. License Agreements Biogen Idec In March 2011, the Company entered into the first amended and restated collaboration agreement with Biogen Idec MA, Inc. (the “Biogen 1st ARCA”), which amended and restated the collaboration agreement with Biogen (the “Biogen OCA”), to provide for the discovery, development and commercialization of small molecule BTK inhibitors. In December 2013, the Company entered into a second amended and restated collaboration agreement with Biogen, to provide the Company with an exclusive worldwide license to develop, manufacture and commercialize vecabrutinib, a BTK inhibitor synthesized under the Biogen 1st ARCA, solely for oncology indications. During the third quarter of 2017, the Company made a milestone payment of $2.5 million to Biogen upon the dosing of the first patient in a Phase 1b/2 study to assess the safety and activity of vecabrutinib in patients with advanced B-cell mid-single-digits. Takeda Oncology In March 2011, Takeda Oncology purchased and exclusively licensed Biogen’s rights to a PDK1 inhibitor program and a pan-Raf inhibitor program which were both originally developed through a collaboration agreement between Sunesis and Biogen. In January 2014, the Company entered into an amended and restated license agreement with Takeda Oncology (the “Amended Takeda Agreement”), to provide the Company with an exclusive worldwide license to develop and commercialize preclinical inhibitors of PDK1. In December 2019, the Company partitioned the Amended Takeda Agreement into two separate agreements: (i) an amended and restated license agreement for PDK (the “PDK Agreement”), and (ii) an amended and restated license agreement for RAF (the “Millennium RAF Agreement”). Pursuant to the PDK Agreement, the Company may in the future be required to make up to $9.1 million in pre-commercialization mid-single DOT-1 In December 2019, Takeda Oncology assigned the Millennium RAF Agreement to DOT-1, DOT-1. DOT-1 DOT-1 TAK-580. pre-commercialization, TAK-580. Denovo In December 2019, the Company entered into the Denovo License Agreement, pursuant to which Sunesis licensed vosaroxin intellectual property to Denovo, received an upfront payment of $0.2 million, and is eligible to receive up to $57.0 million in regulatory and commercial milestones payments and double-digit royalty payments on future sales of vosaroxin. The Company recognized as revenue the $0.1 million of the upfront payment in 2019 and the remaining $0.1 million during the first quarter of 2020 when the identified performance obligation was satisfied. All future event-based milestone and royalty payments are considered fully constrained and therefore, no revenue has been recognized on these fully constrained variable consideration during the three and nine months ended September 30, 2020.	6. License Agreements Biogen Idec The first amended and restated collaboration agreement with Biogen Idec MA, Inc. (the “Biogen 1st ARCA”) amended and restated the collaboration agreement with Biogen (the “Biogen OCA”), to provide for the discovery, development and commercialization of small molecule BTK inhibitors. Under this agreement, the Company no longer has research obligations, but licenses granted to Biogen with respect to the research collaboration under the Biogen OCA (other than the licenses transferred to Takeda Oncology under the Takeda Agreement) remain in effect. In December 2018, the Company entered into a settlement agreement with Biogen whereas Biogen will no longer be obligated to pay future event-based payments or royalty payments to the Company. In December 2013, the Company entered into a second amended and restated collaboration agreement with Biogen, to provide the Company with an exclusive worldwide license to develop, manufacture and commercialize vecabrutinib, a BTK inhibitor synthesized under the Biogen 1st ARCA, solely for oncology indications. During the third quarter of 2017, the Company made a milestone payment of $2.5 million to Biogen upon the dosing of the first patient in a Phase 1b/2 study to assess the safety and activity of vecabrutinib in patients with advanced B-cell mid-single-digits. Takeda Oncology In March 2011, Takeda Oncology purchased and exclusively licensed Biogen’s rights to a PDK1 inhibitor program and a pan-Raf inhibitor program which were both originally developed through a collaboration agreement between Sunesis and Biogen. In January 2014, the Company entered into an amended and restated license agreement with Takeda Oncology (the “Amended Takeda Agreement”), to provide the Company with an exclusive worldwide license to develop and commercialize preclinical inhibitors of PDK1. In December 2019, the Company partitioned the Amended Takeda Agreement into two separate agreements: (i) an amended and restated license agreement for PDK (the “PDK Agreement”), and (ii) an amended and restated license agreement for RAF (the “Millennium RAF Agreement”). Pursuant to the PDK Agreement, the Company may in the future be required to make up to $9.2 million in pre-commercialization mid-single-digits low-teens. DOT-1 In December 2019, Takeda Oncology assigned the Millennium RAF Agreement to DOT-1, DOT-1. DOT-1 DOT-1 TAK-580. pre-commercialization, TAK-580. Denovo In December 2019, the Company entered into the Denovo License Agreement, pursuant to which Sunesis licensed vosaroxin intellectual property to Denovo, received an upfront payment of $0.2 million, and is eligible to receive up to $57.0 million in regulatory and commercial milestones payments and double-digit royalty payments on future sales of vosaroxin. The Company recognized $0.1 million of the upfront payment as revenue in 2019 when the identified performance obligation has been satisfied and the remaining $0.1 million has been recorded as deferred revenue as part of other accrued liabilities on the Company’s consolidated balance sheet as of December 31, 2019. As of December 31, 2019, all future event-based payments and royalty payments are considered fully constrained variable considerations and therefore, no contract assets have been recorded and no revenue have been recognized on these variable considerations.

Notes Payable

Notes Payable	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Notes Payable	6. Notes Payable In April 2019, the Company entered into a term loan agreement with Silicon Valley Bank (the “SVB Loan Agreement”), pursuant to which the Company borrowed $5.5 million. In April 2020, the Company entered into a deferral agreement with Silicon Valley Bank (“SVB”), which extended the interest-only payment period through June 30, 2021 and deferred the maturity date of the borrowings to June 1, 2023. In July 2020, the Company repaid in full all outstanding indebtedness and terminated all commitments and obligations under the SVB Loan Agreement. The repayment to SVB was approximately $5.7 million, which satisfied all of the Company’s debt obligations, including a final interest payment equal to 4% of the original principal amount of the borrowing.	7 . Notes Payable In April 2019, the Company entered into a term loan agreement with Silicon Valley Bank (the “SVB Loan Agreement”), pursuant to which the Company borrowed $5.5 million. The Company used the proceeds of the SVB Loan Agreement plus cash on hand to repay its remaining obligations in the amount of $5.9 million under its existing loan agreement with Western Alliance Bank and Solar Capital Ltd (the “Loan Agreement and Amendments”). The maturity date of the SVB Loan Agreement is December 1, 2022. Under the terms of the SVB Loan Agreement, the Company is required to make interest-only payments through December 31, 2020 on the borrowings at a floating rate equal to the greater of 3.25% or the Prime Rate as defined in the SVB Loan Agreement minus 2.25%, followed by an amortization period of 24 months of equal monthly payments of principal plus interest amounts until paid in full. In addition to and not in substitution for the regular monthly payments of principal plus accrued interest, the Company is required to make a final payment equal to 4% of the original principal amount of the borrowings (the “Final Payment Fee”). Additionally, the Company may prepay all, but not less than all, of the borrowings at any time upon 30 days’ prior notice to Silicon Valley Bank (“SVB”). Any such prepayment would require, in addition to payment of principal and accrued interest as well as the Final Payment Fee, a prepayment fee, in the amount of (a) $165,000 if the prepayment occurs prior to the 1st anniversary of April 26, 2019, or the Effective Date; (b) $110,000 if the prepayment occurs on or after the 1st anniversary of the Effective Date but prior to the 2nd anniversary of the Effective Date; or (c) $55,000 if the prepayment occurs on or after the 2nd anniversary of the Effective Date. The Company’s obligations under the SVB Loan Agreement are secured by a first priority security interest in cash held at an account with SVB (the “Collateral Account”). The Company is obligated to maintain sufficient cash in the Collateral Account at all times in an amount equal to or greater than the outstanding balance of the borrowings. The Company has classified the Collateral Account as restricted cash on its consolidated balance sheets as of December 31, 2019. The SVB Loan Agreement contains customary affirmative and negative covenants which, among other things, limit the Company’s ability to (i) incur additional indebtedness, (ii) pay dividends or make certain distributions, (iii) dispose of its assets, grant liens or encumber its assets or (iv) fundamentally alter the nature of its business. These covenants are subject to a number of exceptions and qualifications. The SVB Loan Agreement also contains customary events of default, including among other things, the Company’s failure to make any principal or interest payments when due, the occurrence of certain bankruptcy or insolvency events or a material adverse change, or its breach of the covenants under the SVB Loan Agreement. Upon the occurrence of an event of default, SVB may, among other things, accelerate the Company’s obligations under the SVB Loan Agreement. The Company was in compliance with all applicable covenants set forth in the SVB Loan Agreement as of December 31, 2019. The principal payments due under the SVB Loan Agreement have been classified as a current liability at December 31, 2019 due to the considerations discussed in Note 1 and the assessment that the material adverse change clause under the SVB Loan Agreement is not within the Company’s control. The Company has not been notified of an event of default by the Lenders as of the date of the filing of this Annual Report Form 10-K. Aggregate future minimum payments due under the SVB Loan Agreement as of December 31, 2019 were as follows (in thousands): Year ending December 31, Total 2020 179 2021 2,888 2022 3,018 Total minimum payments 6,085 Less amount representing interest (585 ) Total notes payable as of December 31, 2019 5,500 Less unamortized debt discount and issuance costs (35 ) Less current portion of notes payable (5,465 ) Non-current $ —

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies From time to time, the Company may be involved in legal proceedings, as well as demands, claims and threatened litigation, which arise in the normal course of its business or otherwise. The ultimate outcome of any litigation is uncertain and unfavorable outcomes could have a negative impact on the Company’s results of operations and financial condition. Regardless of outcome, litigation can have an adverse impact on the Company because of the defense costs, diversion of management resources and other factors. The Company is not currently involved in any material legal proceedings.

Stockholders' Equity

Stockholders' Equity	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Underwritten Offering In July 2020, the Company completed an underwritten public offering of 5,999,999 shares of its common stock, including the full exercise of the underwriter’ option to purchase 782,608 shares of common stock to cover over-allotments, at a price to the public of $2.30 for each share of common stock. Gross proceeds from the sale were approximately $13.8 million, and net proceeds were approximately $12.6 million. Preferred Stock Conversion In July 2020, the Company issued an aggregate of 946,600 shares of its common stock upon conversion of 1,381 shares of its non-voting non-voting non-voting non-voting non-voting Controlled Equity Offerings Cantor Controlled Equity Offering During the three and nine months ended September 30, 2020, no shares of common stock, respectively, were sold under the Controlled Equity Offering SM Aspire Common Stock Purchase Agreement The Common Stock Purchase Agreement (the “CSPA”) with Aspire Capital Fund, LLC (“Aspire”) expired on June 25, 2020 and no shares were issued under the CSPA in 2020 prior to its expiration.	9. Stockholders’ Equity Underwritten Offerings In July 2019, the Company completed underwritten public offerings of (i) 3,833,372 shares of its common stock at a price to the public of $6.00 for each share of common stock, including the full exercise of the underwriters’ option to purchase 500,005 additional shares of common stock to cover over-allotments, and (ii) 8,333 shares of its non-voting non-voting In January 2019, the Company completed underwritten public offerings of (i) 2,300,000 shares of its common stock at a price to the public of $5.00 for each share of common stock, and (ii) 17,000 shares of its non-voting non-voting Preferred Stock The Company has 10,000,000 shares of authorized preferred stock available for issuance in one or more series. Upon issuance, the Company can determine the rights, preferences, privileges and restrictions thereof. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of such series, any or all of which may be greater than the rights of common stock. There were 19,714 and 17,697 shares of preferred stock outstanding as of December 31, 2019 and 2018, respectively. These shares are non-voting non-voting • senior to all of the Company’s Common Stock; • senior to any class or series of the Company’s capital stock hereafter created specifically ranking by its terms junior to the Series D, Series E, and Series F Stock; • on parity with any class or series of the Company’s capital stock hereafter created specifically ranking by its terms on parity with the Series D, Series E, and Series F Stock; • junior to any class or series of the Company’s capital stock hereafter created specifically ranking by its terms senior to the Series D, Series E, and Series F Stock; in each case, as to distributions of assets upon the Company’s liquidation, dissolution or winding up whether voluntarily or involuntarily. During the year ended December 31, 2019, the Company issued a total of 1,195,017 shares of its common stock upon conversion of 13,639 shares of its non-voting non-voting non-voting Common Stock Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders of the Company. Subject to the preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends, if any, as may be declared by the Board of Directors. Under the terms of the Loan Agreement with the Lenders, the Company is precluded from paying cash dividends without the prior written consent of the Lenders. Controlled Equity Offerings In August 2011, the Company entered into a Controlled Equity Offering SM During the years ended December 31, 2019 and 2018, the Company sold less than 0.1 million shares and 0.1 million shares, respectively, of common stock under the Sales Agreement, as amended, at an average price of approximately $11.9 per share and $23.8 per share, respectively, for gross and net proceeds of $0.5 million and $1.4 million, respectively, after deducting Cantor’s commission. As of December 31, 2019, $43.1 million of common stock remained available to be sold under this facility. Aspire Common Stock Purchase Agreement In June 2018, the Company entered into a Common Stock Purchase Agreement (the “CSPA”) with Aspire Capital Fund, LLC (“Aspire”), pursuant to which the Company could issue and sell shares of its common stock having an aggregate gross sales price of up to $15.5 million. Upon execution of the CSPA, the Company sold to Aspire 22,831 shares of common stock at a price of $21.9 per share, for total proceeds of $0.5 million. In addition, Aspire committed to purchasing up to an additional $15.0 million of common shares, at the Company’s request, from time to time during a 24-month a) the lowest sale price of common stock on the purchase date; or b) the arithmetic average of the three lowest closing sale prices during the 10 consecutive business days ending on the trading day immediately preceding the purchase date. The Company also has the right to require Aspire to purchase up to an additional 30% of the trading volume of the shares for the next business day at a purchase price (the “VWAP Purchase Price”), equal to the lesser of: (i) the closing sale price of the shares on the purchase date, or (ii) ninety-seven percent (97%) of the next business day’s volume weighted average price (each such purchase, a “VWAP Purchase”). The Company shall have the right, in its sole discretion, to determine a maximum number of shares and set a minimum market price threshold for each VWAP Purchase. The Company can only require a VWAP Purchase if the Company has also submitted a regular purchase on the notice date for the VWAP Purchase. There are no limits on the number of VWAP purchases that the Company may require. There are no trading volume requirements or restrictions under the CSPA, and the Company will control the timing and amount of sales. Aspire has no right to require any sales by the Company, but is obligated to make purchases from the Company as directed by the Company in accordance with the CSPA There are no limitations on use of proceeds, financial or business covenants, restrictions on future fundings, rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement. The CSPA may be terminated by the Company at any time, at its discretion, without any cost to the Company. Aspire has agreed that neither it nor any of its agents, representatives and affiliates shall engage in any direct or indirect short-selling or hedging of common stock during any time prior to the termination of the CSPA. Any proceeds from the Company receives under the CSPA are expected to be used for working capital and general corporate purposes. The Company cannot request Aspire to purchase more than 200,000 shares per business day. As consideration for Aspire’s obligation under the CSPA, the Company issued 21,233 shares of common stock to Aspire as a commitment fee. This $0.4 million commitment fee and $0.1 million in other transaction costs were recorded in June 2018 as costs of equity financing, within additional paid-in Equity Incentive Plans The Company grants options to purchase shares of its common stock primarily to: (i) new employees, of which 25% of the shares subject to such options become exercisable on the first anniversary of the vesting commencement date, and 1/48th of the shares subject to such options become exercisable each month over the remainder of the four-year vesting period, (ii) existing employees with various vesting schedules over three to four years, (iii) new non-employee two-year non-employee one-year On March 15, 2011, the Company’s Board of Directors adopted, and on June 3, 2011, the Company’s stockholders approved, the 2011 Equity Incentive Plan (the “2011 Plan”). The 2011 Plan is intended as the successor to and continuation of the Company’s 1998 Stock Plan, 2001 Stock Plan, 2005 Equity Incentive Award Plan and 2006 Employment Commencement Incentive Plan (collectively, the “Prior Plans”). No additional stock awards will be granted under the Prior Plans. The number of shares of common stock available for issuance under the 2011 Plan automatically increases on January 1st of each year for a period of 10 years commencing on January 1, 2012 by an amount equal to: (i) 4.0% of the Company’s outstanding shares of common stock on December 31st of the preceding calendar year, or (ii) a lesser amount determined by the Board of Directors. On January 1, 2019 and 2018, in accordance with the above, the number of shares of common stock available for issuance under the 2011 Plan was increased by 149,896 and 137,131 shares, respectively. During the year ended December 31, 2019, options to purchase 171,552 shares of the Company’s common stock were granted under the 2011 Plan. As of December 31, 2019, there were 115,482 shares available for future grants under the 2011 Plan. Employee Stock Purchase Plans On March 5, 2011, the Company’s Board of Directors adopted, and on June 3, 2011, the Company’s stockholders approved, the 2011 Employee Stock Purchase Plan (the “2011 ESPP”). The 2011 ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. Eligible employees can purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the common stock at (i) the beginning of a 12-month 6-month The number of shares of common stock available for issuance under the 2011 ESPP automatically increases on January 1st of each year for a period of 10 years commencing on January 1, 2012 by an amount equal to: (i) 1.0% of the Company’s outstanding shares of common stock on December 31st of the preceding calendar year, or (ii) a lesser amount determined by the Board of Directors. On January 1, 2019, in accordance with the above, the number of shares of common stock available for issuance under the 2011 ESPP was increased by 33,600 shares. A total of 13,332 and 10,410 shares were issued under the 2011 ESPP during the year ended December 31, 2019 and December 31, 2018, respectively. As of December 31, 2019, there were 26,698 shares available for future issuance under the ESPP. Warrants Warrants to purchase shares of the Company’s common stock outstanding as of December 31, 2019 were as follows (in thousands, except per share amounts): Date Issued Shares Exercise Price Per Share Expiration February 2015 1 $ 133.2 February 2020 March 2016 21 $ 32.5 March 2021 Total warrants outstanding and exercisable 22 Warrants to purchase 1,025 shares of the Company’s common stock expired unexercised as of February 27, 2020. Reserved Shares Shares of the Company’s common stock reserved for future issuance as of December 31, 2019 were as follows (in thousands): Shares Outstanding Total Reserved Warrants — 22 22 Convertible preferred stock — 1,971 1,971 Stock option plans 115 516 631 Employee stock purchase plan 27 — 27 Total reserved shares of common stock 142 2,509 2,651

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation Employee and non-employee The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 Research and development $ 119 $ 104 $ 367 $ 400 General and administrative 79 200 429 614 Employee stock-based compensation expense 198 304 796 1,014 Non-employee 202 161 310 262 Total stock-based compensation expense $ 400 $ 465 $ 1,106 $ 1,276	10. Stock-Based Compensation Overview Employee stock-based compensation expense is calculated based on the grant-date fair value of awards ultimately expected to vest and recognized under the straight-line attribution method, assuming that all stock-based awards will vest. The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Year ended December 31, 2019 2018 Research and development $ 513 $ 581 General and administrative 816 903 Employee stock-based compensation expense 1,329 1,484 Non-employee 420 1,153 Total stock-based compensation expense $ 1,749 $ 2,637 Fair Value of Awards The Company determines the fair value of stock-based awards on the grant date using the Black-Scholes model, which is impacted by the Company’s stock price, as well as assumptions regarding a number of subjective variables. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model, and resulting weighted-average and total estimated grant date fair values of employee stock options granted during the periods indicated: Year Ended December 31, 2019 2018 Employees Consultants Employees Consultants Assumptions: Expected term (years) 4.4 4.2 4.3 9.8 Expected volatility 108.9 % 114.2 % 126.0 % 117.6 % Risk-free interest rate 1.9 % 1.7 % 2.6 % 2.8 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Fair value: Weighted-average estimated grant date fair value per share $ 6.7 $ 5.6 $ 9.6 $ 11.9 Options granted (in thousands) 110 62 120 42 Total estimated grant date fair value (in thousands) $ 735 $ 292 $ 1,161 $ 497 The estimated fair value of stock options that vested in the years ended December 31, 2019 and 2018 was $1.6 million and $2.0 million, respectively. The Company based its assumptions for the expected term on historical cancellation and exercise data, and the contractual term and vesting terms of the awards. Expected volatility is based on historical volatility of the Company’s common stock. The Company does not anticipate paying any cash dividends in the foreseeable future, and therefore uses an expected dividend yield of zero. Option Plan Activity The following table summarizes stock option activity for the Company’s stock option plans in the periods presented (in thousands, except per share amounts): Number Weighted Weighted Aggregate Outstanding as of December 31, 2018 416 $ 36.6 Options granted 172 $ 10.0 Options exercised — $ — Options forfeited or expired (72 ) $ 32.7 Outstanding as of December 31, 2019 516 $ 27.3 8.19 $ — Vested and expected to vest as of December 31, 2019 516 $ 27.3 8.19 $ — Exercisable as of December 31, 2019 315 $ 35.6 7.73 $ — The aggregate intrinsic value in the table above represents the total pre-tax in-the-money The intrinsic value of options exercised during each of the years ended December 31, 2019 and 2018 was zero and less than $0.1 million, respectively. As the Company believes it is probable that no stock option related tax benefits will be realized, the Company does not record any net tax benefits related to exercised options. Total estimated unrecognized stock-based compensation cost related to unvested stock options was $2.0 million as of December 31, 2019, which is expected to be recognized over the respective vesting terms of each award. The weighted average term of the unrecognized stock-based compensation expense is 2.3 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes Loss before the provision for income taxes consisted of the following (in thousands): Year Ended December 31, 2019 2018 U.S. operations $ (23,330 ) $ (21,132 ) Foreign operations — (5,483 ) Loss before provision for income taxes $ (23,330 ) $ (26,615 ) No provision for income taxes was recorded in the periods presented due to tax losses incurred in each period. The income tax provision differs from the amount computed by applying the statutory income tax rate of 21% to pre-tax Year Ended December 31, 2019 2018 Tax (benefit) at statutory federal rate 21.0 % 21.0 % State tax (benefit), net of federal benefit 7.1 4.6 Foreign tax rate differential — (4.3 ) Permanent differences (0.6 ) (0.6 ) Research and development credits 1.3 1.0 Change in valuation allowance (20.9 ) (15.9 ) Provision-to-return — (0.7 ) Expired NOLs, research and development credits, and other carryfowards (6.9 ) (2.2 ) Non-qualified (1.0 ) (2.9 ) Effective tax rate — % — % Deferred income taxes reflect the net tax effects of loss and credit carry-forwards and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets for federal and state income taxes are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Federal and state net operating loss carry-forwards $ 119,015 $ 114,254 Federal and state research credit carry-forwards 15,140 14,885 Capitalized research costs 6,081 6,134 Stock-based compensation 3,996 4,002 Lease liabilities 152 — Property and equipment 77 79 Accrued liabilities 86 143 Gross deferred tax assets 144,547 139,497 Deferred tax liabilities: Right-of-use (152 ) — Gross deferred tax liabilities (152 ) — Net deferred tax assets 144,395 139,497 Valuation allowance (144,395 ) (139,497 ) Deferred tax assets, net of valuation allowance $ — $ — The Company’s unrecognized tax benefits relate to research and development tax credits claimed on the Company’s tax returns. The research and development tax credits have not been utilized, are fully offset by a valuation allowance, and currently have no tax expense impact and no related interest and penalties has been accrued. The Company does not anticipate the unrecognized tax benefits position will significantly change over the next twelve months. A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is follows (in thousands): December 31, 2019 2018 Unrecognized tax benefits at beginning of period $ 1,812 $ 1,769 Increases related to current year tax positions 58 43 Decreases related to prior year tax positions (23 ) — Unrecognized tax benefits at the end of period $ 1,847 $ 1,812 The Company has recorded a full valuation allowance against its net deferred tax assets due to the uncertainty as to whether such assets will be realized. The valuation allowance increased by approximately $4.9 million in the year ended December 31, 2019 primarily due to the generation of current year net operating losses and research and development credits claimed. As of December 31, 2019, the Company had federal net operating loss carry-forwards of $463.4 million and federal research and development tax credit carry-forwards of $9.8 million. If not utilized, the federal net operating loss and tax credit carry-forwards will begin to expire 2020. As of December 31, 2019, the Company had state net operating loss carry-forwards of $310.7 million, which expire beginning in 2028, and state research and development tax credit carry-forwards of $8.7 million, which do not expire. In addition, the use of net operating loss and tax credit carryforwards may be limited under Section 382 of the Internal Revenue Code in certain situations where changes occur in the stock ownership of a company. In the event that the Company has had a change in ownership, utilization of the carryforwards could be restricted. The Company recognizes the financial statement effect of tax positions when it is more likely than not that the tax positions will be sustained upon examination by the appropriate taxing authorities. As of December 31, 2019 and 2018, the Company had unrecognized tax benefits of $1.8 million. The Company files U.S. federal and California tax returns. The Company’s wholly owned subsidiaries, Sunesis Europe Limited and Sunesis Pharmaceuticals (Malta) Ltd., are currently not required to file tax returns. To date, neither the Company nor any of its subsidiaries have been audited by the Internal Revenue Service, any state income tax authority or tax authority in the related jurisdictions. Due to net operating loss carry-forwards, substantially all of the Company’s tax years remain open to federal tax examination.

Guarantees and Indemnification

Guarantees and Indemnification	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Guarantees and Indemnification	12. Guarantees and Indemnification As permitted under Delaware law and in accordance with the Company’s Bylaws, the Company indemnifies its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity. The indemnification agreements with the Company’s officers and directors terminate upon termination of their employment, but the termination does not affect claims for indemnification relating to events occurring prior to the effective date of termination. The maximum amount of potential future indemnification is unlimited; however, the Company’s officer and director insurance policy reduces the Company’s exposure and may enable the Company to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification agreements is minimal. In addition, in the ordinary course of business the Company enters into agreements, such as licensing agreements, clinical trial agreements and certain services agreements, containing standard indemnifications provisions. The Company believes that the likelihood of an adverse judgment related to such indemnification provisions is remote. Accordingly, the Company has not recorded any liabilities for any of these agreements as of December 31, 2019.

Leases

Leases	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Leases [Abstract]
Leases	9. Leases The Company’s operating lease obligations as of September 30, 2020 relate solely to the leasing of office space in a building at 395 Oyster Point Boulevard in South San Francisco, California, which is currently the Company’s headquarters. The lease was entered into in January 2014 and was amended several times since 2014. The lease was last amended in December 2017 to extend the expiration date to June 30, 2021, with an option to extend the lease for two additional years. The Company did not assume the option to extend the lease term for two additional years in its determination of the lease term as the exercise of the option was not reasonably certain when the lease was last amended in December 2017. The remaining lease term as of September 30, 2020 was nine months. The cash paid for operating lease liability was $0.2 million and $0.5 million for the three and nine months ended September 30, 2020, respectively. Maturity of lease liability is as follows (in thousands): Through December 31, 2020 $ 147 2021 294 Total rental payments 441 Less imputed interest (32 ) Present value of lease liability $ 409 The Company recognizes rent expense on a straight-line basis. The Company recorded rent expense of $0.1 million for each of the three months ended September 30, 2020 and 2019. The Company recorded rent expense of $0.4 million for each of the nine months ended September 30, 2020 and 2019.	13. Leases The Company’s operating lease obligations as of December 31, 2019 relate solely to the leasing of office space in a building at 395 Oyster Point Boulevard in South San Francisco, California, which is currently the Company’s headquarters. The lease was entered into in January 2014 and was amended several times since 2014. The lease was last amended in December 2017 to extend the expiration date to June 30, 2021, with an option to extend the lease for two additional years. The Company did not assume the option to extend the lease term for two additional years in its determination of the lease term as the exercise of the option was not reasonably certain when the lease was last amended in December 2017. The remaining lease term as of December 31, 2019 was 1.5 years. The cash paid for operating lease liability was $0.6 million and the ROU asset obtained in exchange for new operating lease liability was $1.4 million, for the year ended December 31, 2019. Maturity of lease liability is as follows (in thousands): Through December 31, Payments 2020 $ 579 2021 294 Total rental payments 873 Less imputed interest (56 ) Present value of lease liability $ 817 The Company recognizes rent expense on a straight-line basis. The Company recorded rent expense of $0.6 million and $0.4 million for the year ended December 31, 2019 and 2018, respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On September 2, 2020, the Company effected a one-for-ten reverse split of its outstanding common stock (the “Reverse Split”), as previously authorized and approved at the annual meeting of stockholders on June 16, 2020. As a result of the Reverse Split, every ten shares of common stock were combined into one share of common stock. The Reverse Split affected the shares of Company’s common stock: (a) outstanding immediately prior to the effective time of the Reverse Split, (b) available for issuance under the Company’s equity incentive plans, (c) issuable upon the exercise of outstanding stock options and warrants and (d) issuable upon conversion of the outstanding non-voting Series E and Series F Convertible Preferred Stock. All share and per-share data in the Company’s consolidated financial statements and notes thereto have been restated to give retroactive effect to the Reverse Split for all periods presented.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
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”) for interim financial information and with the instructions to Form 10-Q Rule 10-01 S-X. Form 10-K	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”).
Reverse Stock Split	Reverse Stock Split On September 2, 2020, the Company effected a one-for-ten non-voting per-share
Adopted Accounting Pronouncements	Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments available-for-sale 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments 2019-05, Financial Instruments—Credit Losses, Topic 326 2016-13. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. 2019-12 In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other options (Subtopic 470-20) 815-40). 2020-06	Adopted Accounting Pronouncements In August 2016, the FASB issued ASU No. 2016-15, zero-coupon In February 2016, the FASB issued ASU No. 2016-02, right-of-use 2018-10, 2018-11, 2019-01, The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease right-of-use right-of-use In June 2018, the FASB issued ASU No. 2018-07, Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments available-for-sale 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments 2019-05, Financial Instruments—Credit Losses, Topic 326 2016-13. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses. 2019-10 2019-11 2016-13. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. 2019-12
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Malta) Ltd., a Malta corporation. All intercompany balances and transactions have been eliminated in consolidation.	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Malta) Ltd., a Malta corporation. All intercompany balances and transactions have been eliminated in consolidation.
Segment Reporting		Segment Reporting Management has determined that the Company operates as a single reportable segment.
Significant Estimates and Judgments	Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to valuation of marketable securities, equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting.	Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of marketable securities, equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting.
Cash Equivalents and Marketable Securities	Cash Equivalents The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds, repurchase agreements, and corporate debt securities.	Cash Equivalents and Marketable Securities The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds, repurchase agreements, and corporate debt securities. Restricted cash consists of amounts pledged as collateral for term loan agreement as contractually required by the lender. Marketable securities consist of securities with original maturities of greater than three months, which may include U.S. and European government obligations and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company generally classifies its entire investment portfolio as available-for-sale. available-for-sale Available-for-sale The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in other income, net in the statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to significant exchange gains or losses as currencies fluctuate from quarter to quarter. As of December 31, 2019 and December 31, 2018, the Company held investments denominated in Euros with an aggregate fair value of zero, and $0.8 million, respectively. Any cash, cash equivalent and short-term investment balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are both recorded in other income, net in the statements of operations and comprehensive loss.
Fair Value Measurements	Fair Value Measurements The Company measures cash equivalents at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1—Observable input such as quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date; Level 2—inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly for the asset or liability. These include quoted prices for similar assets or liabilities in active markets; and Level 3—unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company’s Level 2 valuations of marketable securities, if any, are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3, if any. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of September 30, 2020 and December 31, 2019.	Fair Value Measurements The Company measures cash equivalents and marketable securities at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - Observable input such as quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date; Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly for the asset or liability. These include quoted prices for similar assets or liabilities in active markets; and Level 3 - unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3, if any. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, deferred revenue, and notes payable approximated their fair value as of December 31, 2019 and December 31, 2018.
Leases		Leases The Company determines if an arrangement is or contains a lease at inception. In determining whether an arrangement is a lease, the Company considers whether (1) explicitly or implicitly identified assets have been deployed in the arrangement and (2) the Company obtains substantially all of the economic benefits from the use of that underlying asset and directs how and for what purpose the asset is used during the term of the contract. ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. When an implicit rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at commencement date for new leases or effective date for existing leases, in determining the present value of lease payments. Leases may contain initial periods of free rent and/or periodic escalations. When such items are included in a lease agreement, the Company records rent expense on a straight-line basis over the initial term of a lease. The difference between the rent payment and the straight-line rent expense is recorded as a deferred rent liability. The Company expenses any additional payments under its operating leases for taxes, insurance or other operating expenses as incurred
Accounting for Notes Payable		Accounting for Notes Payable The accounting for certain fees and expenses related to the SVB Loan Agreement (see Note 8) is as follows. The debt issuance cost is being accounted for as a debt discount and classified within notes payable on the Company’s balance sheet. The debt discount is being amortized as interest expense over the term of the loan using the effective interest method. The final payment is being accreted as interest expense over the term of the loans using the effective interest method.
Revenue Recognition		Revenue Recognition On January 1, 2018, the Company adopted Topic 606, Revenue from Contracts with Customers Revenue Recognition Adoption of the new standard did not result in any change to the Company’s opening retained earnings as of January 1, 2018 as no cumulative impact to the adoption of ASC 606 was noted as a result of the Company’s assessment of the comparative revenue recognized since inception of the contracts under the new revenue standard ASC 606 and historic standard ASC 605. The Company is applying the practical exemption allowed under ASC 606 and does not disclose the value of variable consideration that is a sale-based royalty promised in exchange for a license of intellectual property. The adoption of the new standard resulted in changes to the Company’s accounting policies for revenue recognition as detailed below: The Company’s contracts consist license, milestone and royalty payments primarily generated through agreements with strategic partners for the development and commercialization of the Company’s product candidates. The terms of the agreement typically include non-refundable Non-refundable In determining the appropriate amount of revenue to be recognized as it fulfills its performance obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Licenses of intellectual property: non-refundable, up-front non-refundable, up-front Event-based or milestone payments: Royalties:
Research and Development		Research and Development Research and development expense consists primarily of: (a) clinical trial costs, which include payments for work performed by contract research organizations (“CROs”), clinical trial sites, labs and other clinical service providers, and for drug packaging, storage and distribution; (b) drug manufacturing costs, which include costs for producing drug substance and drug product, and for stability and other testing; (c) personnel costs for related permanent and temporary employees; (d) other outside services and consulting costs; and (e) payments under license agreements. All research and development costs are expensed as they are incurred.
Clinical Trial Accounting		Clinical Trial Accounting The Company records accruals for estimated clinical trial costs, which include payments for work performed by CROs and participating clinical trial sites. These costs are generally a significant component of research and development expense. Costs incurred for setting up clinical trial sites for participation in trials are generally non-refundable,
Stock-Based Compensation		Stock-Based Compensation The Company grants options to purchase common stock to its employees, directors and consultants under its stock option plans. Under the Company’s Employee Stock Purchase Plan, eligible employees can also purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock at the beginning of a 12-month six-month The Company values these share-based awards using the Black-Scholes option valuation model (the “Black-Scholes model”). The determination of fair value of share-based payment awards on the date of grant using the Black-Scholes model is affected by the Company’s stock price as well as assumptions regarding a number of subjective variables. These variables include, but are not limited to, the expected stock price volatility over the term of the awards and actual and projected employee stock option exercise behaviors. The Company accounts for forfeitures of share-based payment awards as they occur.
Foreign Currency		Foreign Currency Transactions that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date. Any foreign currency-denominated monetary assets and liabilities are subsequently remeasured at current exchange rates as of each balance sheet date, with gains or losses on foreign exchange recognized in other income, net in the statements of operations and comprehensive loss.
Warrants for Shares of Common Stock		Warrants for Shares of Common Stock The Company accounts for warrants for shares of common stock as equity instruments in the accompanying balance sheets at their fair value on the date of issuance because such warrants are indexed to the Company’s common stock and no cash settlement is required except for (i) liquidation of the Company, or (ii) a change in control in which the common stockholders also receive cash.
Income Taxes		Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the differences between the tax basis of assets and liabilities and their basis for financial reporting. Deferred tax assets or liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to recognize interest charges and penalties in other income, net in the statements of operations and comprehensive loss.

Loss per Common Share (Tables)

Loss per Common Share (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Loss per Common Share		The following table sets forth the computation of basic and diluted loss per common share for the periods presented (in thousands, except per share amounts): Year Ended December 31, 2019 2018 Numerator: Net loss—basic and diluted $ (23,330 ) $ (26,615 ) Denominator: Weighted-average common shares outstanding—basic and diluted 8,712 3,558 Net loss per common share: Basic and Diluted $ (2.68 ) $ (7.48 )
Schedule of Potential Common Shares Issuable Pursuant to Outstanding Securities Excluded from Computation of Diluted Loss per Common Share	The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): Three and Nine September 30, 2020 2019 Warrants to purchase shares of common stock 21 22 Convertible preferred stock 1,025 1,971 Options to purchase shares of common stock 757 500 Outstanding securities not included in calculations 1,803 2,493	The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): As of December 31, 2019 2018 Warrants to purchase shares of common stock 22 22 Convertible preferred stock 1,971 633 Options to purchase shares of common stock 516 416 Outstanding securities not included in calculations 2,509 1,071

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Company's Financial Assets Measured on Recurring Basis	The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated (in thousands): September 30, 2020 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds—classified as cash equivalents Level 1 $ 24,503 $ — $ — $ 24,503 December 31, 2019 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds Level 1 $ 3,495 $ — $ — $ 3,495 U.S. Treasury securities Level 1 1,594 1 — 1,595 Repurchase agreements Level 2 5,000 — — 5,000 U.S. corporate debt obligations Level 2 5,155 — — 5,155 U.S. commercial paper Level 2 11,412 — — 11,412 Total available-for-sale 26,656 1 — 26,657 Less amounts classified as cash equivalents (10,293 ) — — (10,293 ) Amounts classified as marketable securities $ 16,363 $ 1 $ — $ 16,364	The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated, which were comprised solely of available-for-sale December 31, 2019 Valuation Amortized Gross Gross Estimated Fair Money market funds Level 1 $ 3,495 $ — $ — $ 3,495 U.S. Treasury securities Level 1 1,594 1 — 1,595 Repurchase agreements Level 2 5,000 — — 5,000 U.S. corporate debt obligations Level 2 5,155 — — 5,155 U.S. commercial paper Level 2 11,412 — — 11,412 Total available-for-sale 26,656 1 — 26,657 Less amounts classified as cash equivalents (10,293 ) — — (10,293 ) Amounts classified as marketable securities $ 16,363 $ 1 $ — $ 16,364 December 31, 2018 Valuation Amortized Gross Gross Estimated Fair Money market funds Level 1 $ 10,845 $ — $ — $ 10,845 Total available-for-sale 10,845 — — 10,845 Less amounts classified as cash equivalents (10,845 ) — — (10,845 ) Amounts classified as marketable securities $ — $ — $ — $ —

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Summary of Other Accrued Liabilities	Other accrued liabilities as of December 31 were as follows (in thousands): 2019 2018 Accrued outside services $ 690 $ 556 Accrued professional services 220 251 Accrued interest 57 284 Deferred revenue 120 — Other accruals 22 — Total other accrued liabilities $ 1,109 $ 1,091

Notes Payable (Tables)

Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Summary of Future Minimum Payments Under Loan Facility	Aggregate future minimum payments due under the SVB Loan Agreement as of December 31, 2019 were as follows (in thousands): Year ending December 31, Total 2020 179 2021 2,888 2022 3,018 Total minimum payments 6,085 Less amount representing interest (585 ) Total notes payable as of December 31, 2019 5,500 Less unamortized debt discount and issuance costs (35 ) Less current portion of notes payable (5,465 ) Non-current $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Warrants to Purchase Shares of Company's Common Stock	Warrants to purchase shares of the Company’s common stock outstanding as of December 31, 2019 were as follows (in thousands, except per share amounts): Date Issued Shares Exercise Price Per Share Expiration February 2015 1 $ 133.2 February 2020 March 2016 21 $ 32.5 March 2021 Total warrants outstanding and exercisable 22
Shares of Common Stock Reserved for Future Issuance	Shares of the Company’s common stock reserved for future issuance as of December 31, 2019 were as follows (in thousands): Shares Outstanding Total Reserved Warrants — 22 22 Convertible preferred stock — 1,971 1,971 Stock option plans 115 516 631 Employee stock purchase plan 27 — 27 Total reserved shares of common stock 142 2,509 2,651

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense Related to Company's Stock-Based Awards	The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 Research and development $ 119 $ 104 $ 367 $ 400 General and administrative 79 200 429 614 Employee stock-based compensation expense 198 304 796 1,014 Non-employee 202 161 310 262 Total stock-based compensation expense $ 400 $ 465 $ 1,106 $ 1,276	The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Year ended December 31, 2019 2018 Research and development $ 513 $ 581 General and administrative 816 903 Employee stock-based compensation expense 1,329 1,484 Non-employee 420 1,153 Total stock-based compensation expense $ 1,749 $ 2,637
Summary of Weighted-Average and Total Estimated Grant Date Fair Values of Employee Stock Options Granted		The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model, and resulting weighted-average and total estimated grant date fair values of employee stock options granted during the periods indicated: Year Ended December 31, 2019 2018 Employees Consultants Employees Consultants Assumptions: Expected term (years) 4.4 4.2 4.3 9.8 Expected volatility 108.9 % 114.2 % 126.0 % 117.6 % Risk-free interest rate 1.9 % 1.7 % 2.6 % 2.8 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Fair value: Weighted-average estimated grant date fair value per share $ 6.7 $ 5.6 $ 9.6 $ 11.9 Options granted (in thousands) 110 62 120 42 Total estimated grant date fair value (in thousands) $ 735 $ 292 $ 1,161 $ 497
Summary of Stock Option Activity for Company's Stock Option Plans		The following table summarizes stock option activity for the Company’s stock option plans in the periods presented (in thousands, except per share amounts): Number Weighted Weighted Aggregate Outstanding as of December 31, 2018 416 $ 36.6 Options granted 172 $ 10.0 Options exercised — $ — Options forfeited or expired (72 ) $ 32.7 Outstanding as of December 31, 2019 516 $ 27.3 8.19 $ — Vested and expected to vest as of December 31, 2019 516 $ 27.3 8.19 $ — Exercisable as of December 31, 2019 315 $ 35.6 7.73 $ —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Loss before the Provision for Income Taxes	Loss before the provision for income taxes consisted of the following (in thousands): Year Ended December 31, 2019 2018 U.S. operations $ (23,330 ) $ (21,132 ) Foreign operations — (5,483 ) Loss before provision for income taxes $ (23,330 ) $ (26,615 )
Income Tax Provision Amount Computed by Applying the Statutory Income Tax Rate	The income tax provision differs from the amount computed by applying the statutory income tax rate of 21% to pre-tax Year Ended December 31, 2019 2018 Tax (benefit) at statutory federal rate 21.0 % 21.0 % State tax (benefit), net of federal benefit 7.1 4.6 Foreign tax rate differential — (4.3 ) Permanent differences (0.6 ) (0.6 ) Research and development credits 1.3 1.0 Change in valuation allowance (20.9 ) (15.9 ) Provision-to-return — (0.7 ) Expired NOLs, research and development credits, and other carryfowards (6.9 ) (2.2 ) Non-qualified (1.0 ) (2.9 ) Effective tax rate — % — %
Significant Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets for federal and state income taxes are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Federal and state net operating loss carry-forwards $ 119,015 $ 114,254 Federal and state research credit carry-forwards 15,140 14,885 Capitalized research costs 6,081 6,134 Stock-based compensation 3,996 4,002 Lease liabilities 152 — Property and equipment 77 79 Accrued liabilities 86 143 Gross deferred tax assets 144,547 139,497 Deferred tax liabilities: Right-of-use (152 ) — Gross deferred tax liabilities (152 ) — Net deferred tax assets 144,395 139,497 Valuation allowance (144,395 ) (139,497 ) Deferred tax assets, net of valuation allowance $ — $ —
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is follows (in thousands): December 31, 2019 2018 Unrecognized tax benefits at beginning of period $ 1,812 $ 1,769 Increases related to current year tax positions 58 43 Decreases related to prior year tax positions (23 ) — Unrecognized tax benefits at the end of period $ 1,847 $ 1,812

Leases (Tables)

Leases (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Leases [Abstract]
Maturity of Lease Liability	Maturity of lease liability is as follows (in thousands): Through December 31, 2020 $ 147 2021 294 Total rental payments 441 Less imputed interest (32 ) Present value of lease liability $ 409	Maturity of lease liability is as follows (in thousands): Through December 31, Payments 2020 $ 579 2021 294 Total rental payments 873 Less imputed interest (56 ) Present value of lease liability $ 817

Company Overview - Additional I

Company Overview - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Jul. 31, 2020	Dec. 31, 2019	Dec. 31, 2019	Sep. 30, 2020	Dec. 31, 2018
Cash and cash equivalents, restricted cash, and marketable securities		$ 34,600,000	$ 34,600,000
Maturity limits period			24 months
Dollars weighted average maturity limit period			12 months
Percentage of reduction in workforce	30.00%
Severance costs related to reduction in workforce	$ 200,000
Cash and cash equivalents		12,761,000	$ 12,761,000	$ 26,048,000	$ 13,696,000
Accumulated deficit		682,800,000	682,800,000	$ 699,603,000	$ 659,469,000
License Agreement Terms [Member] | Takeda License Agreements [Member]
Upfront payment received		2,000,000
License Agreement Terms [Member] | Takeda License Agreements [Member] | Maximum [Member]
Potential pre-commercialization payments receivable		57,000,000	57,000,000
License Vosaroxin [Member] | Denovo Biopharma, LLC [Member]
Upfront payment received		200,000
Potential regulatory and commercial payments receivable		$ 57,000,000	$ 57,000,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	Sep. 02, 2020	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)Segment	Dec. 31, 2019USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Significant Accounting Policies [Line Items]
Lease liability		$ 409,000	$ 817,000
Present value of remaining lease payments		441,000	$ 873,000
Right-of-use asset		$ 409,000		$ 817,000		$ 0
Number of reportable segment | Segment			1
Fair value of investments denominated in Euros				$ 0		$ 800,000
Common stock offering period			At the beginning of a 12-month offering period or at the end of one of the two related six-month purchase periods.
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date		Mar. 31, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]		true
ASC 842
Significant Accounting Policies [Line Items]
Lease liability					$ 1,362,000
Present value of remaining lease payments					1,434,000
Right-of-use asset					$ 1,362,000
Incremental borrowing rate					4.00%
ASU 2016-13 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]		true
ASU 2020-06 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]		true
Common Stock [Member]
Significant Accounting Policies [Line Items]
Reverse stock split	one-for-ten	one-for-ten
Conversion ratio	10
Employee Stock Purchase Plan [Member]
Significant Accounting Policies [Line Items]
Purchase price of a share as a percentage of fair market value			85.00%	85.00%

Loss per Common Share - Computa

Loss per Common Share - Computation of Basic and Diluted Loss per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	[1]	$ (4,638)	$ (5,942)	$ (16,803)	$ (18,043)	$ (23,330)	$ (26,615)
Denominator:
Weighted-average common shares outstanding—basic and diluted	[1]	15,929	10,507	12,748	7,897	8,712	3,558
Net loss per common share:
Basic and Diluted	[1]	$ (0.29)	$ (570)	$ (1.32)	$ (2.28)	$ (2,680)	$ (7,480)
[1]	Share and per-share data in the condensed consolidated statement of operations and comprehensive loss have been adjusted to give retroactive effect to the Reverse Split for all periods presented.

Loss per Common Share - Schedul

Loss per Common Share - Schedule of Potential Common Shares Issuable Pursuant to Outstanding Securities Excluded from Computation of Diluted Loss per Common Share (Detail) - shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	1,803	2,493	1,803	2,493	2,509,000	1,071,000
Warrants to purchase shares of common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	21	22	21	22	22,000	22,000
Options to purchase shares of common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	757	500	757	500	516,000	416,000
Convertible preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	1,025	1,971	1,025	1,971	1,971,000	633,000

Financial Instruments - Fair Va

Financial Instruments - Fair Value of Company's Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		$ 26,656	$ 10,845
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities, Estimated Fair Value		26,657	10,845
Less amounts classified as cash equivalents, Amortized Cost		(10,293)	(10,845)
Less amounts classified as cash equivalents, Estimated Fair Value		(10,293)	(10,845)
Amounts classified as marketable securities, Amortized Cost		16,363
Amounts classified as marketable securities, Gross Unrealized Gains		1
Amounts classified as marketable securities, Estimated Fair Value	$ 0	16,364	0
Level 1 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost	24,503	3,495	10,845
Available-for-sale securities, Estimated Fair Value	$ 24,503	3,495	$ 10,845
Level 1 [Member] | U.S. Treasury securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		1,594
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities, Estimated Fair Value		1,595
Level 2 [Member] | Repurchase agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		5,000
Available-for-sale securities, Estimated Fair Value		5,000
Level 2 [Member] | U.S. corporate debt obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		5,155
Available-for-sale securities, Estimated Fair Value		5,155
Level 2 [Member] | U.S. commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		11,412
Available-for-sale securities, Estimated Fair Value		$ 11,412

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Unrealized gain or loss on available-for-sale securities			$ 0		$ 0	$ 0
Sales of available-for-sale debt securities						0	$ 0
Realized gains or losses on available-for-sale securities	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0

Other Accrued Liabilities - Sum

Other Accrued Liabilities - Summary of Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued outside services		$ 690	$ 556
Accrued professional services		220	251
Accrued interest		57	284
Deferred revenue		120	0
Other accruals		22	0
Total other accrued liabilities	$ 1,727	$ 1,109	$ 1,091

License Agreements - Additional

License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended			9 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2017	Sep. 30, 2020
Biogen [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payment				$ 2,500,000
Takeda License Agreements [Member] | License Agreement Terms [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential pre-commercialization milestone payments payable	$ 9,100,000
Upfront payment received	2,000,000
DOT-1 License Agreement [Member] | License Agreement Terms [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential pre-commercialization payments receivable	57,000,000
Contract assets	0
Received recognized on variable considerations	0	$ 0			$ 0
Upfront payment received	2,000,000
Upfront payment recognized as revenue	2,000,000
Denovo License Agreement [Member] | License Agreement Terms [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Received recognized on variable considerations		$ 0			$ 0
Upfront payment received	200,000
Upfront payment recognized as revenue	100,000		$ 100,000
Regulatory, commercial milestones payments and double-digit royalty payments, receivable	57,000,000
Denovo License Agreement [Member] | License Vosaroxin [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contract assets	0
Received recognized on variable considerations	0
Upfront payment received	200,000
Upfront payment recognized as revenue	100,000
Regulatory, commercial milestones payments and double-digit royalty payments, receivable	57,000,000
Denovo License Agreement [Member] | License Vosaroxin [Member] | Other Accrued Liabilities [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	$ 100,000

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail) - USD ($)	1 Months Ended
	Apr. 30, 2020	Jul. 31, 2019	Apr. 30, 2019
Debt Instrument [Line Items]
Repayments of debt		$ 5,700,000
Final payment interest fee, percentage		4.00%
Amended Loan Agreement [Member]
Debt Instrument [Line Items]
Repayment of remaining obligations			$ 5,900,000
Term Loan Agreement [Member]
Debt Instrument [Line Items]
Borrowing amount			$ 5,500,000
SVB Deferral Agreement [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 1, 2023
Debt instrument, extended interest-only payments date	Jun. 30, 2021
Silicon Valley Bank [Member] | Term Loan Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, payment terms			Under the terms of the SVB Loan Agreement, the Company is required to make interest-only payments through December 31, 2020 on the borrowings at a floating rate equal to the greater of 3.25% or the Prime Rate as defined in the SVB Loan Agreement minus 2.25%, followed by an amortization period of 24 months of equal monthly payments of principal plus interest amounts until paid in full
Debt instrument, frequency of periodic payment			monthly
Debt instrument, amortization period			24 months
Final payment fee, percentage			4.00%
Borrowing amount			$ 5,500,000
Maturity date			Dec. 1, 2022
Debt instrument, extended interest-only payments date			Dec. 31, 2020
Silicon Valley Bank [Member] | Term Loan Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, floating interest rate			3.25%
Silicon Valley Bank [Member] | Term Loan Agreement [Member] | Prior to 1st Anniversary of April 26 2019 or Effective Date [Member]
Debt Instrument [Line Items]
Prepayment fee			$ 165,000
Silicon Valley Bank [Member] | Term Loan Agreement [Member] | After 1st Anniversary but Prior to 2nd Anniversary of Effective Date [Member]
Debt Instrument [Line Items]
Prepayment fee			110,000
Silicon Valley Bank [Member] | Term Loan Agreement [Member] | After 2nd Anniversary of Effective Date [Member]
Debt Instrument [Line Items]
Prepayment fee			$ 55,000
Silicon Valley Bank [Member] | Term Loan Agreement [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on floating rate			2.25%

Notes Payable - Summary of Futu

Notes Payable - Summary of Future Minimum Payments Under Loan Facility (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total notes payable as of December 31, 2019		$ 5,500
Less current portion of notes payable	$ 0	(5,465)	$ (7,396)
Notes payable [Member]
Debt Instrument [Line Items]
2020		179
2021		2,888
2022		3,018
Total minimum payments		6,085
Less amount representing interest		(585)
Less unamortized debt discount and issuance costs		$ (35)

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)

Jan. 01, 2019shares

Jan. 02, 2018shares

Jul. 31, 2020USD ($)$ / sharesshares

Jul. 31, 2019USD ($)$ / sharesshares

Jan. 31, 2019USD ($)$ / sharesshares

Jun. 30, 2018USD ($)ArithmeticaveragePurchasePeriod$ / sharesshares

Nov. 30, 2017USD ($)

Sep. 30, 2020USD ($)shares

Sep. 30, 2020USD ($)shares

Sep. 30, 2019USD ($)shares

Dec. 31, 2020

Dec. 31, 2019USD ($)Arithmeticaverage$ / sharesshares

Dec. 31, 2018USD ($)$ / sharesshares

Feb. 27, 2020shares

Dec. 31, 2017USD ($)

Stockholders Equity [Line Items]

Shares of common stock issued

11,139,000

3,747,000

Preferred stock, shares authorized

10,000,000

10,000,000

10,000,000

Preferred stock, shares outstanding

20,000

18,000

Number of shares issued under employee stock purchase plan

13,332,000

10,410,000

Common stock, voting rights

one vote per share

Options granted, Number of Shares

172,000

Shares Available for Future Grant

142,000

Fair Value Of Shares Issuable Under Employee Stock Purchase Plan | $

$ 25,000

Preferred stock, shares issued

20,000

18,000

Proceeds from issuance of common stock, net | $

$ 12,633,000

$ 32,068,000

$ 32,022,000

Shares outstanding

20,000

18,000

Subsequent Event [Member]

Stockholders Equity [Line Items]

Number of warrants, expired

1,025,000

2011 Plan [Member]

Stockholders Equity [Line Items]

Common stock available for issuance automatic increase maximum number of shares

4.00%

Common stock available for issuance automatic increase period

10 years

Shares of common stock available for issuance

149,896,000

137,131,000

Options granted, Number of Shares

171,552,000

Shares Available for Future Grant

115,482,000

Stock Option Plans [Member]

Stockholders Equity [Line Items]

Shares Available for Future Grant

115,000

Stock Option Plans [Member] | New Employees [Member]

Stockholders Equity [Line Items]

Vesting rights

New employees, of which 25% of the shares subject to such options become exercisable on the first anniversary of the vesting commencement date, and 1/48th of the shares subject to such options become exercisable each month over the remainder of the four-year vesting period

Option exercisable on first anniversary of vesting commencement date, percent

25.00%

Stock option plans, vesting period

4 years

Portion of option exercisable for each month over vesting percent

2.083%

Stock Option Plans [Member] | Existing employees [Member]

Stockholders Equity [Line Items]

Vesting rights

Existing employees with various vesting schedules over three to four years

Stock option plans, vesting period

4 years

Stock Option Plans [Member] | New Non-Employee Board Members [Member]

Stockholders Equity [Line Items]

Vesting rights

New non-employee members of the board of directors, of which 50% of the shares subject to such options become exercisable on each of the first and second anniversary of the vesting commencement date

Stock option plans, vesting period

2 years

Portion of option exercisable for each month over vesting percent

4.166%

Stock Option Plans [Member] | Continuing Non-Employee Board Members [Member]

Stockholders Equity [Line Items]

Vesting rights

Continuing non-employee members of the board of directors, of which 1/24th of the shares subject to such options become exercisable each month following the date of grant over a two-year vesting period

Stock option plans, vesting period

1 year

Portion of option exercisable for each month over vesting percent

8332.00%

Series B Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Preferred stock, shares outstanding

0

Convertible preferred stock, shares converted

13,639,000

Shares outstanding

0

Series C Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Preferred stock, shares outstanding

0

Convertible preferred stock, shares converted

1,558,000

Shares outstanding

0

Series D Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 2,000

Shares issued upon conversion

100,000

Preferred stock, shares outstanding

0

1,381

Convertible preferred stock, shares converted

1,381,000

1,119,000

Shares outstanding

0

1,381

Series E Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 500

Shares issued upon conversion

100,000

Preferred stock, shares outstanding

1,915,000

10,000

Convertible preferred stock, shares converted

8,085,000

7,000,000

Shares outstanding

1,915,000

10,000

Series F Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 600

Shares issued upon conversion

100,000

Preferred stock, shares outstanding

8,333,000

8,333

Shares outstanding

8,333,000

8,333

Series D, Series E and Series F Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Preferred stock, payment to stock holders in the event of liquidation, dissolution or winding up preference per share

0.0001%

Preferred stock, voting rights

Shares of Series D, Series E, and Series F Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D and Series E Stock will be required to amend the terms of the Series D, Series E, and Series F Stock.

Series D, Series E and Series F Convertible Preferred Stock [Member] | Minimum [Member]

Stockholders Equity [Line Items]

Percentage of outstanding common stock

9.98%

Common Stock [Member]

Stockholders Equity [Line Items]

Number of shares issued under employee stock purchase plan

7,000

[1]

6,000

[1]

13,000

10,000

Conversion of preferred stock to common stock, shares

946,600,000

947,000

[1]

947,000

[1]

1,195,000

[1]

1,195,000

[1]

Underwritten Public Offering [Member]

Stockholders Equity [Line Items]

Shares of common stock issued

5,999,999,000

3,833,372,000

2,300,000,000

Price per common share | $ / shares

$ 2.30

Proceeds from issuance of common stock, gross | $

$ 13,800,000

$ 28,000,000

$ 20,000,000

Proceeds from issuance of common stock, net | $

$ 12,600,000

$ 26,100,000

$ 18,500,000

Underwritten Public Offering [Member] | Series E Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Shares issued upon conversion

100,000

Preferred stock, shares issued

17,000,000

Underwritten Public Offering [Member] | Series F Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Shares issued upon conversion

100,000

Preferred stock, shares issued

8,333,000

Underwritten Public Offering [Member] | Series F Convertible Preferred Stock [Member] | Maximum [Member]

Stockholders Equity [Line Items]

Percentage of outstanding common stock

9.98%

Underwritten Public Offering [Member] | Preferred Stock [Member] | Series E Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 500

Underwritten Public Offering [Member] | Preferred Stock [Member] | Series E Convertible Preferred Stock [Member] | Maximum [Member]

Stockholders Equity [Line Items]

Percentage of outstanding common stock

9.98%

Underwritten Public Offering [Member] | Preferred Stock [Member] | Series F Convertible Preferred Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 600

Underwritten Public Offering [Member] | Common Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 6

$ 5

Additional Controlled Equity Offerings Facilities [Member]

Stockholders Equity [Line Items]

Increase in aggregate controlled equity offering agreement as per amendment | $

$ 45,000,000

Common stock sales agreement further amended, date

2017-11

Issuance of common stock through equity facilities commission percentage, maximum

3.00%

Employee Stock Purchase Plan [Member]

Stockholders Equity [Line Items]

Common stock available for issuance automatic increase maximum number of shares

1.00%

Common stock available for issuance automatic increase period

10 years

Shares of common stock available for issuance

33,600,000

Shares Available for Future Grant

27,000

Purchase price of a share as a percentage of fair market value

85.00%

85.00%

Duration of offering period

12 months

Number of purchase periods in each offering period | Arithmeticaverage

2

Duration of each purchase period

6 months

Over-Allotment Option [Member]

Stockholders Equity [Line Items]

Shares of common stock issued

500,005,000

Option To Purchase Shares Of Over-Allotments [Member]

Stockholders Equity [Line Items]

Shares of common stock issued

782,608,000

Controlled Equity Offering Facilities [Member]

Stockholders Equity [Line Items]

Proceeds from issuance of common stock, gross | $

$ 500,000

$ 1,400,000

Proceeds from issuance of common stock, net | $

500,000

$ 1,400,000

Issuance of common stock, remaining offering value | $

$ 43,100,000

$ 43,100,000

$ 43,100,000

Controlled Equity Offering Facilities [Member] | Common Stock [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 11.9

$ 23.8

Common stock, shares sold

0

100

100

CSPA [Member] | Aspire [Member]

Stockholders Equity [Line Items]

Common stock purchase agreement period

0 months

Arithmetic average lowest closing sales price | Arithmeticaverage

3

Number of consecutive business days | PurchasePeriod

10

Percentage of volume weighted average price of closing sale price

(97.00%)

Common stock issued as commitment fee

21,233,000

Commitment fee | $

$ 400,000

Other transactions cost | $

$ 100,000

Request to purchase shares per business day

200,000,000

Proceeds from issuance of common stock, net | $

$ 500,000

CSPA [Member] | Aspire [Member] | Registration Rights Agreement [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 22

Remaining Purchase Commitment | $

$ 10,900,000

Proceeds from issuance of common stock, net | $

$ 4,600,000

Common stock, shares sold

0

0

239,064,000

Date of termination

Jun. 25, 2020

CSPA [Member] | Minimum [Member] | Aspire [Member]

Stockholders Equity [Line Items]

Closing price of common stock

2.50%

CSPA [Member] | Maximum [Member] | Aspire [Member]

Stockholders Equity [Line Items]

Issuance of common stock, offering value | $

$ 15,500,000

Commitment to purchase additional common shares | $

$ 15,000,000

CSPA [Member] | Common Stock [Member] | Aspire [Member]

Stockholders Equity [Line Items]

Price per common share | $ / shares

$ 21.9

Common stock, shares sold

22,831,000

CSPA [Member] | Common Stock [Member] | Maximum [Member] | Aspire [Member]

Stockholders Equity [Line Items]

shares of common stock to purchase per business day

20,000,000

[1]

The condensed consolidated statement of stockholders’ equity has been adjusted to give retroactive effect to the Reverse Split for all periods presented.

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Warrants to Purchase Shares of Company's Common Stock (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Class of Warrant or Right [Line Items]
Total warrants outstanding and exercisable, shares	22
February 2015 [Member]
Class of Warrant or Right [Line Items]
Warrants, Exercise Price Per Share | $ / shares	$ 133.2
Total warrants outstanding and exercisable, shares	1
Warrants Expiration Date	2020-02
March 2016 [Member]
Class of Warrant or Right [Line Items]
Warrants, Exercise Price Per Share | $ / shares	$ 32.5
Total warrants outstanding and exercisable, shares	21
Warrants Expiration Date	2021-03

Stockholders' Equity - Shares o

Stockholders' Equity - Shares of Common Stock Reserved for Future Issuance (Detail)	Dec. 31, 2019shares
Class of Stock [Line Items]
Shares Available for Future Grant	142,000
Outstanding Securities	2,509,000
Total Shares Reserved	2,651,000
Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Shares Available for Future Grant	27,000
Total Shares Reserved	27,000
Stock Option Plans [Member]
Class of Stock [Line Items]
Shares Available for Future Grant	115,000
Outstanding Securities	516,000
Total Shares Reserved	631,000
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Outstanding Securities	1,971,000
Total Shares Reserved	1,971,000
Warrants [Member]
Class of Stock [Line Items]
Outstanding Securities	22,000
Total Shares Reserved	22,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Related to Company's Stock-Based Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 400	$ 465	$ 1,106	$ 1,276	$ 1,749	$ 2,637
Employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	198	304	796	1,014	1,329	1,484
Non-employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	202	161	310	262	420	1,153
Research and development [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	119	104	367	400	513	581
General and administrative [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 79	$ 200	$ 429	$ 614	$ 816	$ 903

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Weighted-Average and Total Estimated Grant Date Fair Values of Employee Stock Options Granted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Assumptions:
Expected dividend yield	0.00%
Fair value:
Options granted (in thousands)	172
Stock Option Plans [Member] | Employees [Member]
Assumptions:
Expected term (years)	4 years 4 months 24 days	4 years 3 months 18 days
Expected volatility	108.90%	126.00%
Risk-free interest rate	1.90%	2.60%
Expected dividend yield	0.00%	0.00%
Fair value:
Weighted-average estimated grant date fair value per share	$ 6.7	$ 9.6
Options granted (in thousands)	110	120
Total estimated grant date fair value (in thousands)	$ 735	$ 1,161
Stock Option Plans [Member] | Consultants [Member]
Assumptions:
Expected term (years)	4 years 2 months 12 days	9 years 9 months 18 days
Expected volatility	114.20%	117.60%
Risk-free interest rate	1.70%	2.80%
Expected dividend yield	0.00%	0.00%
Fair value:
Weighted-average estimated grant date fair value per share	$ 5.6	$ 11.9
Options granted (in thousands)	62	42
Total estimated grant date fair value (in thousands)	$ 292	$ 497

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of stock options, vested	$ 1,600,000	$ 2,000,000
Payment of cash dividends	$ 0
Dividend yield ratio	0.00%
Intrinsic value of options exercised	$ 0
Tax benefits related to stock option exercised	0
Unrecognized stock-based compensation cost related to unvested stock options	$ 2,000,000
Weighted average term of unrecognized stock-based compensation expense	2 days
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised		$ 100,000

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Option Activity for Company's Stock Option Plans (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Share-based Payment Arrangement [Abstract]
Outstanding, Beginning Balance, Number of Shares | shares	416
Options granted, Number of Shares | shares	172
Options forfeited or expired, Number of Shares | shares	(72)
Outstanding, Ending Balance, Number of Shares | shares	516
Vested and expected to vest as of December 31, 2019, Number of Shares | shares	516
Exercisable as of December 31, 2019, Number of Shares | shares	315
Outstanding, Beginning Balance, Weighted Average Exercise Price Per Share | $ / shares	$ 36.6
Options granted, Weighted Average Exercise Price Per Share | $ / shares	10
Options forfeited or expired, Weighted Average Exercise Price Per Share | $ / shares	32.7
Outstanding, Ending Balance, Weighted Average Exercise Price Per Share | $ / shares	27.3
Vested and expected to vest as of December 31, 2019, Weighted Average Exercise Price Per Share | $ / shares	27.3
Exercisable as of December 31, 2019, Weighted Average Exercise Price Per Share | $ / shares	$ 35.6
Outstanding, Weighted Average Remaining Contractual Term (Years)	8 years 2 months 8 days
Vested and expected to vest as of December 31, 2019, Weighted Average Remaining Contractual Term (Years)	8 years 2 months 8 days
Exercisable as of December 31, 2019, Weighted Average Remaining Contractual Term (Years)	7 years 8 months 23 days

Income Taxes - Loss before Prov

Income Taxes - Loss before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. operations	$ (23,330)	$ (21,132)
Foreign operations		(5,483)
Loss before provision for income taxes	$ (23,330)	$ (26,615)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Income tax provision	$ 0	$ 0
Statutory income tax rate	21.00%	21.00%
Unrecognized tax benefits that would have tax impact	$ 0
Unrecognized tax benefits, interest and penalties accrued	0
Unrecognized tax benefits position will significantly change over the next twelve months	0
Net valuation allowance, increased (decreased)	4,900,000
Unrecognized tax benefits	1,800,000	$ 1,812,000	$ 1,769,000
Domestic tax authority [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	463,400,000
Research and development tax credit carry-forwards	$ 9,800,000
Net operating loss carry-forwards expiration	2020
State and local jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	$ 310,700,000
Research and development tax credit carry-forwards	$ 8,700,000
Net operating loss carry-forwards expiration	2028

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision Amount Computed by Applying Statutory Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax (benefit) at statutory federal rate	21.00%	21.00%
State tax (benefit), net of federal benefit	7.10%	4.60%
Foreign tax rate differential		(4.30%)
Permanent differences	(0.60%)	(0.60%)
Research and development credits	1.30%	1.00%
Change in valuation allowance	(20.90%)	(15.90%)
Provision-to-return		(0.70%)
Expired NOLs, research and development credits, and other carryfowards	(6.90%)	(2.20%)
Non-qualified stock option cancellations	(1.00%)	(2.90%)

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Federal and state net operating loss carry-forwards	$ 119,015	$ 114,254
Federal and state research credit carry-forwards	15,140	14,885
Capitalized research costs	6,081	6,134
Stock-based compensation	3,996	4,002
Lease liabilities	152
Property and equipment	77	79
Accrued liabilities	86	143
Gross deferred tax assets	144,547	139,497
Deferred tax liabilities:
Right-of-use assets	(152)
Gross deferred tax liabilities	(152)
Net deferred tax assets	144,395	139,497
Valuation allowance	$ (144,395)	$ (139,497)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning of period	$ 1,812	$ 1,769
Increases related to current year tax positions	58	43
Decreases related to prior year tax positions	(23)
Unrecognized tax benefits at the end of period	$ 1,800	$ 1,812

Guarantees and Indemnification

Guarantees and Indemnification - Additional Information (Detail)	Dec. 31, 2019USD ($)
Guarantees [Abstract]
Liabilities incurred in indemnification agreements	$ 0

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Line Items]
Cash paid for operating lease liability	$ 0.2		$ 0.5			$ 0.6
ROU asset obtained in exchange for new operating lease liability						1.4
Rent expense	$ 0.1	$ 0.1	$ 0.4	$ 0.4		$ 0.6	$ 0.4
Original Operating Lease [Member]
Leases [Line Items]
Operating lease agreement, original date			2014-01		2014-01
Fifth Amended Operating Lease [Member]
Leases [Line Items]
Lease expiration date			Jun. 30, 2021		Jun. 30, 2021
Operating lease agreement, date of amendment			2017-12		2017-12
Operating lease, property description			The lease was last amended in December 2017 to extend the expiration date to June 30, 2021, with an option to extend the lease for two additional years. The Company did not assume the option to extend the lease term for two additional years in its determination of the lease term as the exercise of the option was not reasonably certain when the lease was last amended in December 2017.		The lease was last amended in December 2017 to extend the expiration date to June 30, 2021, with an option to extend the lease for two additional years. The Company did not assume the option to extend the lease term for two additional years in its determination of the lease term as the exercise of the option was not reasonably certain when the lease was last amended in December 2017.
Lessee, operating lease, existence of option to extend [true false]			true		true
Option to extend the lease			option to extend the lease for two additional years.		option to extend the lease for two additional years.
Operating lease, renewal term	2 years		2 years		2 years
Operating lease, remaining term			9 months			1 year 6 months

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Lease Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Leases [Abstract]
2020	$ 579	$ 147
2021	294	294
Total rental payments	873	441
Less imputed interest	(56)	(32)
Present value of lease liability	$ 817	$ 409

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Common Stock [Member]	Sep. 02, 2020	Sep. 30, 2020
Subsequent Event [Line Items]
Reverse stock split	one-for-ten	one-for-ten
Conversion ratio	10