Sierra Oncology (SRRA) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 05, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	Sierra Oncology, Inc.
Entity Central Index Key	0001290149
Trading Symbol	SRRA
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Small Business	true
Entity Common Stock, Shares Outstanding		10,395,732
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock
Entity Address, State or Province	BC
Entity Address, Country	CA

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 133,534	$ 147,528
Prepaid expenses and other current assets	1,936	2,369
Total current assets	135,470	149,897
Property and equipment, net	112	113
Operating lease right-of-use asset	547	589
Other assets	662	729
TOTAL ASSETS	136,791	151,328
CURRENT LIABILITIES:
Accrued and other liabilities	5,640	7,170
Accounts payable	1,357	1,019
Warrant liabilities		45,935
Securities issuance obligation		10,485
Total current liabilities	6,997	64,609
Operating lease liability	298	374
TOTAL LIABILITIES	7,295	64,983
Commitments and Contingencies (Note 8)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of March 31, 2020 and December 31, 2019; nil shares issued and outstanding as of March 31, 2020 and 103,000 shares Series A convertible voting preferred stock issued and outstanding as of December 31, 2019		1
Common stock, $0.001 par value; 500,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 10,395,732 and 1,867,176 shares issued and outstanding as of March 31, 2020 and December 31, 2019	10	74
Additional paid-in capital	927,085	851,957
Accumulated deficit	(797,599)	(765,687)
TOTAL STOCKHOLDERS' EQUITY	129,496	86,345
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 136,791	$ 151,328

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	10,395,732	10,395,732
Common stock, shares outstanding	1,867,176	1,867,176
Series A Convertible Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	103,000
Preferred stock, shares outstanding	0	103,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
Research and development	$ 11,591	$ 10,137
General and administrative	4,544	3,365
Total operating expenses	16,135	13,502
Loss from operations	(16,135)	(13,502)
Other income (expense), net:
Changes in fair value of warrant liabilities	(16,240)
Other income, net	541	325
Total other income (expense), net	(15,699)
Loss before provision for (benefit from) income taxes, net	(31,834)	(13,177)
Provision for (benefit from) income taxes, net	78	(145)
Net loss and comprehensive loss	$ (31,912)	$ (13,032)
Net loss per common share, basic and diluted	$ (3.14)	$ (7)
Weighted-average shares used in computing net loss per common share, basic and diluted	10,156,628	1,862,132

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Series A Convertible Voting Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Stockholders Equity, Ending Balance at Dec. 31, 2018	$ 94,479		$ 74	$ 771,817	$ (677,412)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2018			1,859,120
Issuance of common stock for exercise of stock options	445			445
Issuance of common stock for exercise of stock options, Shares			8,056
Stock-based compensation	1,699			1,699
Net loss	(13,032)				(13,032)
Stockholders Equity, Ending Balance at Mar. 31, 2019	83,591		$ 74	773,961	(690,444)
Stockholders Equity, Ending Balance, Shares at Mar. 31, 2019			1,867,176
Stockholders Equity, Ending Balance at Dec. 31, 2019	86,345	$ 1	$ 74	851,957	(765,687)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2019		103,000	1,867,176
Conversion of Series A convertible voting preferred stock to common stock		$ (1)	$ 8	(7)
Conversion of Series A convertible voting preferred stock to common stock, Shares		(103,000)	7,803,273
Reclassification of warrant liabilities to equity	62,175			62,175
Issuance of common stock in connection with an amendment to the asset purchase agreement, Shares			725,283
Issuance of common stock in connection with an amendment to the asset purchase agreement	8,782		$ 1	8,781
Issuance of warrant in connection with an amendment to the asset purchase agreement	3,188			3,188
Stock-based compensation	918			918
Reverse stock split adjustment			(73)	73
Net loss	(31,912)				(31,912)
Stockholders Equity, Ending Balance at Mar. 31, 2020	$ 129,496		$ 10	$ 927,085	$ (797,599)
Stockholders Equity, Ending Balance, Shares at Mar. 31, 2020			10,395,732

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (31,912)	$ (13,032)
Adjustments to reconcile net loss to net cash used in operating activities:
Changes in fair value of warrant liabilities	16,240
Securities issuance obligation	1,485
Stock-based compensation	918	1,699
Depreciation and amortization	55	62
Other	2	(26)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	429	(1,003)
Accrued, other and operating lease liabilities	(1,522)	(2,599)
Accounts payable	357	(667)
Net cash used in operating activities	(13,948)	(15,566)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment		(14)
Net cash used in investing activities		(14)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of common stock options		445
Net cash provided by financing activities		445
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(46)	(3)
NET (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(13,994)	(15,138)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period	147,828	106,346
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period	133,834	91,208
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for (refund of) income taxes, net	14	(29)
Cash paid for interest		81
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Issuance of common stock and common stock warrant in connection with an amendment to the asset purchase agreement	11,970
Reclassification of warrant liabilities to equity	62,175
Right-of-use asset obtained in exchange for operating lease obligation		$ 771
Unpaid property and equipment in accrued and other liabilities	12
Unpaid deferred financing costs in accrued and other liabilities	$ 45

The Company and Basis of Presen

The Company and Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Basis of Presentation	1. The Company and Basis of Presentation Organization and Description of Business Sierra Oncology, Inc. (together with its subsidiaries, collectively referred to as the “Company”), a Delaware corporation, is a late stage drug development company focused on advancing its product candidate, momelotinib, a potent, selective and orally-bioavailable JAK1 (Janus kinase 1), JAK2 (Janus kinase 2) and ACVR1 (Activin A receptor type 1) inhibitor with a potentially differentiated therapeutic profile for the treatment of myelofibrosis. Momelotinib has been investigated in two completed Phase 3 clinical trials for the treatment of myelofibrosis and has demonstrated a potentially differentiated therapeutic profile encompassing anemia-related clinical benefits, as well as achieving constitutional symptom control benefits and substantive splenic volume reductions. The Company’s portfolio also includes two DNA Damage Response (DDR) assets, consisting of SRA737 and SRA141. SRA737 is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1). SRA141 is a potent, selective and orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7). The Company has decided to suspend the continued development of its product candidates SRA737 and SRA141 to focus its resources on the development of momelotinib. The Company is exploring non-dilutive The Company’s primary activities since inception have been conducting research and development activities, conducting preclinical and clinical testing, recruiting personnel, performing business and financial planning, identifying and evaluating additional drug candidates for potential in-licensing The Company has not generated any product revenue related to its primary business purpose to date, nor has it generated any income, and is subject to a number of risks and uncertainties, which include dependence on key individuals, the need to identify and successfully develop commercially viable products, the need to obtain regulatory approval for its products and commercialize them, and the need to obtain adequate additional financing to fund the development of momelotinib. As of March 31, 2020, the Company had $133.5 million of cash and cash equivalents. The Company believes that its balance of cash and cash equivalents as of the date of the issuance of these condensed consolidated financial statements is sufficient to fund its current operational plan for at least the next twelve months though it may pursue raising additional capital through equity financings or other arrangements. Reverse Stock Split On January 21, 2020, the Company’s shareholders approved an amendment to the Company’s certificate of incorporation to effect a reverse split of the Company’s common stock (Reverse Stock Split). On January 21, 2020, the Company’s board of directors approved the specific ratio for the Reverse Stock Split, which became effective on January 22, 2020, at 1-for-40. The

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 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) and applicable rules and regulations of the Securities and Exchange Commission regarding interim financial reporting. Accordingly, they do not include all the information and notes required for complete financial statements and should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s Annual Report on Form 10-K 10-K These unaudited condensed consolidated financial statements and related disclosure have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020, or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2019 included herein was derived from the audited consolidated financial statements as of that date. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of stock options and the warrant issued, fair value of the securities issuance obligation, accruals such as research and development costs, and recoverability of the Company’s net deferred tax assets and related valuation allowance. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	3. Net Loss Per Share Basic net loss per share is calculated by dividing net loss by the weighted-average number of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, stock options and the warrant for common stock are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following shares of common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have been antidilutive: March 31, 2020 March 31, 2019 (in thousands) Series A warrants for common stock 7,802,241 — Series B warrants for common stock 2,574,727 — Options to purchase common stock 1,738,827 329,880 Warrant s 727,122 1,839 Total potential dilutive shares 12,842,917 331,719

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company measures and reports its cash equivalents, restricted cash, warrant liabilities and securities issuance obligation at fair value. The following table sets forth the fair value of the Company’s financial assets measured on a recurring basis by level within the fair value hierarchy: March 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 132,963 $ — $ — $ 132,963 Restricted money market funds 300 — — 300 Total financial assets $ 133,263 $ — $ — $ 133,263 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 146,240 $ — $ — $ 146,240 Restricted money market funds 300 — — 300 Total financial assets $ 146,540 $ — $ — $ 146,540 Financial Liabilities Warrant liabilities $ — $ — $ 45,935 $ 45,935 Securities issuance obligation — — 10,485 10,485 Total financial liabilities $ — $ — $ 56,420 $ 56,420 Money market funds and restricted money market funds are measured at fair value on a recurring basis using quoted prices and are classified as a Level 1 input. The Company’s warrant liabilities and securities issuance obligation contained unobservable inputs that reflected the Company’s own assumptions in which there was little, if any, market activity at the measurement date. Accordingly, the Company’s warrant liabilities were measured at fair value on a recurring basis using unobservable inputs until such time the warrants were no longer considered derivative instruments. The change in the fair value of warrant liabilities is recognized as a component of other income (expense), net in the accompanying condensed consolidated statement of operations for the three months ended March 31, 2020. The securities issuance obligation was measured at fair value on a recurring basis using unobservable inputs until the common stock and the common stock warrant were issued. The change in fair values of the securities issuance obligation is recognized as research and development expense in the accompanying condensed consolidated statement of operations for the three months ended March 31, 2020. The warrant liabilities and the securities issuance obligation were classified as Level 3 inputs. The assumptions used in calculating the estimated fair values represented the Company’s best estimate. However, inherent uncertainties are involved. If factors or assumptions change, the estimated fair values could be materially different. At January 22, 2020, Warrant A and Warrant B were no longer considered to be derivative instruments. The Company remeasured the fair value of the warrant liabilities at the time of reclassification to equity using the following assumptions: Series A Series B Expected term (in years) 5.0 2.1 Expected volatility 43 % 88 % Risk-free interest rate 1.57 % 1.53 % Expected dividend yield — % — % At January 31, 2020, the securities issuance obligation was settled by the issuance of common stock and a common stock warrant. The Company remeasured the fair value of its common stock issuance obligation based on the value of the common stock at the time of issuance. The warrant issuance obligation was remeasured using the following assumptions: Warrant Expected term (in years) 5.0 Expected volatility 43 % Risk-free interest rate 1.57 % Expected dividend yield — % The following table provides a summary of changes in the estimated fair values of the Company’s Level 3 financial liabilities: Series A Series B Warrant Common Total (in thousands) Balance, December 31, 2019 $ 32,616 $ 13,319 $ 3,036 $ 7,449 $ 56,420 Changes in fair value 11,597 4,643 152 1,333 17,725 Settlement of financial liabilities by securities issuance — — (3,188 ) (8,782 ) (11,970 ) Reclassification to equity (44,213 ) (17,962 ) — — (62,175 ) Balance, March 31, 2020 $ — $ — $ — $ — $ — There were no transfers between Levels 1, 2 or 3 during the three months ended March 31, 2020.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Cash and Cash Equivalents Cash and cash equivalents consist of the following: March 31, 2020 December 31, (in thousands) Cash $ 571 $ 1,288 Cash equivalents: Money market accounts 132,963 146,240 Total cash and cash equivalents $ 133,534 $ 147,528 The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the condensed consolidated balance sheets to the amounts shown in the condensed consolidated statements of cash flows. March 31, 2020 March 31, (in thousands) Cash and cash equivalents $ 133,534 $ 90,908 Restricted cash included in other assets 300 300 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 133,834 $ 91,208 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following: March 31, December 31, (in thousands) Prepaid insurance $ 582 $ 918 Prepaid research and development project costs 581 853 Other receivables 156 190 Other 617 408 Total prepaid expenses and other current assets $ 1,936 $ 2,369 Property and Equipment, net Property and equipment, net consists of the following: March 31, December 31, (in thousands) Software $ 364 $ 352 Leasehold improvements 112 112 Computer equipment 89 89 Furniture and fixtures 3 3 Property and equipment, gross 568 556 Less: accumulated depreciation (456 ) (443 ) Total property and equipment, net $ 112 $ 113 Depreciation related to the Company’s property and equipment was $13,000 for the three ended March 31, 2020 and $21,000 for the three months ended March 31, 2019. Accrued and Other Liabilities Accrued and other liabilities consist of the following: March 31, December 31, (in thousands) Accrued research and development costs $ 2,777 $ 2,668 Accrued employee related costs 1,411 3,420 Accrued professional fees 1,162 817 Operating lease liability 175 187 Other 115 78 Total accrued and other liabilities $ 5,640 $ 7,170

Leases

Leases	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases	6. Leases In June 2017, the Company entered into an operating lease agreement to lease the office space in Vancouver, Canada commencing March 1, 2018. The lease expires on February 28, 2023 and can be extended for an additional term of 5 years. The components of lease expense and related cash flows for the three months ended March 31, 2020 and 2019 were as follows: Three Months Ended Three Months Ended (in thousands) Operating lease cost $ 51 $ 51 Short-term lease cost 22 29 73 80 Operating cash flows used for operating leases $ 52 $ 40 As of March 31, 2020, the weighted average remaining lease term and discount rate for the operating lease are 2.9 years and 6.5%, respectively. As of March 31, 2020, maturities of lease liability due under the lease agreement are as follows: Years Ending December 31: Operating Leases (in thousands) Remainder of 2020 $ 150 2021 203 2022 162 Total lease payments 515 Less imputed interest (42 ) Total $ 473 In addition to base rent, these leases require payment of non-lease non-component

Term Loan

Term Loan	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Term Loan	7. Term Loan In August 2018, the Company entered into a Loan and Security Agreement (Loan Agreement) with Silicon Valley Bank (SVB). Contemporaneously with executing the Loan Agreement, the Company drew down $5.0 million. On December 18, 2019, the Company repaid the $5.0 million term loan and paid the associated prepayment and final payment fees. In connection with the Loan Agreement, the Company issued a warrant to SVB to purchase 1,839 of the Company’s common stock at a price per share of $74.80. The warrant was immediately exercisable, will expire on August 21, 2028, contains a cashless exercise provision and is classified as equity. During the three months ended March 31, 2019, the Company recognized interest expense of $ million. No interest expense was recognized for the three months ended March 31, 2020.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Asset Purchase Agreement In August 2018, the Company entered into an Asset Purchase Agreement with Gilead whereby the Company acquired worldwide rights to the pharmaceutical product momelotinib, an investigational orally-bioavailable JAK1, JAK2 and ACVT1 inhibitor together with all related intellectual property rights and certain other related assets. Pursuant to the agreement, the Company made a one-time In connection with obligations under the amendment, the Company recognized a $10.5 million non-cash shares of million of non-cash License Agreements In September 2016, the Company entered into an exclusive license agreement with CRT Pioneer Fund LP (CPF) for worldwide rights, know-how one-time product-by-product country-by-country In May 2016, the Company entered into an exclusive license agreement (Carna License Agreement) with Carna Biosciences, Inc. (Carna) for worldwide rights to develop and commercialize SRA141, a small molecule kinase inhibitor targeting Cdc7. In exchange for this exclusive right, the Company paid Carna an upfront payment of $0.9 million in June 2016. The Company will be required to pay Carna milestone payments of up to an aggregate of $270.0 million upon achievement of certain developmental, regulatory and commercial milestone events, including a milestone payment of $4.0 million upon dosing of the first patient in the first Phase 1 clinical trial for SRA141. These milestones will be accrued once they are considered probable of occurring. As of March 31, 2020, the Company had not recorded any milestone payments to Carna. In addition, the Company is required to pay Carna tiered single-digit royalties on net sales of product candidates (as defined under the Carna License Agreement). The Company is exploring non-dilutive Legal From time to time, the Company may become subject to other legal proceedings, claims and litigation arising in the ordinary course of business. In addition, the Company may receive letters alleging infringement of patent or other intellectual property rights. The Company is not currently a party to any other material legal proceedings, nor is it aware of any pending or threatened litigation that, in the Company’s opinion, would have a material adverse effect on the business, operating results, cash flows or financial condition should such litigation be resolved unfavorably.

Common Stock Reserved for Issua

Common Stock Reserved for Issuance	3 Months Ended
	Mar. 31, 2020
Common Stock Reserved for Issuance [Member]
Stockholders' Equity Note Disclosure	9. Common Stock Reserved for Issuance The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to effect the conversion of all outstanding options granted and available for grant under the incentive plans, shares reserved for issuance under the employee stock purchase plan and issued warrant. March 31, December 31, Shares reserved under Series A warrant 7,802,241 7,802,241 Shares reserved under Series B warrant 2,574,727 2,574,727 Shares reserved for future option grants under equity plans 3,025,897 51,514 Outstanding stock options under equity incentive plans 1,738,827 326,023 Outstanding warrant 727,122 1,839 Shares reserved under the 2015 employee stock purchase plan 17,500 17,500 Shares reserved for conversion of Series A Preferred Stock — 7,803,273 Total common stock reserved for issuance 15,886,314 18,577,117

Preferred Stock

Preferred Stock	3 Months Ended
	Mar. 31, 2020
Preferred Stock [Member]
Stockholders' Equity Note Disclosure	10. Preferred Stock As of March 31, 2020 and December 31, 2019, the Company had 10,000,000 shares of preferred stock authorized with a par value of $0.001. There were no preferred stock outstanding as of March 31, 2020 and 103,000 shares of Series A convertible voting preferred stock (Series A Preferred Stock) outstanding as of December 31, 2019. Series A Convertible Voting Preferred Stock On November 13, 2019, the Company completed an underwritten public offering whereby it issued 103,000 shares of Series A Preferred Stock together with Series A warrants and Series B warrants for a combined purchase price of $1,000. The aggregate proceeds received by the Company was $97.7 million, net of underwriting discounts and commissions and offering expenses. Each share of Series A Preferred Stock was On January , , all shares of Series A Preferred Stock converted into shares of the Company’s common stock.

Warrant Liabilities

Warrant Liabilities	3 Months Ended
	Mar. 31, 2020
Warrants and Rights Note Disclosure [Abstract]
Warrant Liabilities	11. Warrant Liabilities In connection with the Company’s November 2019 public offering of the Series A Preferred Stock, the Company issued Series A warrants to purchase up to 7,802,241 shares of common stock at an exercise price equal to $13.20, and Series B warrants to purchase up to 2,574,727 shares of common stock at an exercise price equal to $13.20. Both Series A and Series B warrants became exercisable on January 22, 2020 following stockholder approval of the Reverse Stock Split which resulted in a sufficient number of authorized common stock to allow for the exercise of the warrants, subject to certain beneficial ownership limitations. The Series A warrants will expire five years from the date they first became exercisable or on January 22, 2025 and contain a cash and/or cashless exercise provision. The Series B warrants will expire on the 75th day anniversary following the announcement of top-line The fair values of the Series A and Series B warrants were classified as warrant liabilities until they ceased to be derivative instruments following stockholder approval of an increase in authorized common stock sufficient to allow for the exercise of the warrants, at which time they were reclassified to equity. The Company revalued the warrant liabilities until they ceased to be derivative instruments using the Black-Scholes option pricing model. The Company recorded a million non-cash

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	12. Stock-Based Compensation In the accompanying condensed consolidated statements of operations, the Company recognized stock-based compensation expense for its employees and non-employees Three Months Ended March 31, 2020 2019 Research and development $ 546 $ 1,184 General and administrative 372 515 Total stock-based compensation $ 918 $ 1,699 Determination of Fair Value The estimated grant-date fair values of all of the Company’s stock-based awards were calculated using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended March 31, 2020 2019 Expected term (in years) 5.7 – 6.7 5.3 – 6.9 Expected volatility 88 – 90 % 91 – 94 % Risk-free interest rate 0.6 – 1.2 % 2.5 – 2.6 % Expected dividend rate — % — % Equity Incentive Plans 2018 Equity Inducement Plan In September 2018, the Company’s Compensation Committee approved the 2018 Equity Inducement Plan (2018 Plan). The number of shares available for awards under the 2018 Plan was set to 37,500. The exercise price of each stock-based award issued under the 2018 Plan is required to be no less than the fair value of the Company’s capital stock. The vesting and exercise provisions of options or restricted awards granted are determined individually with each grant. Stock options have a 10-year 2015 Plan The 2015 Equity Incentive Plan (2015 Plan) became effective on July 14, 2015. On January 21, 2020 the Company’s stockholders approved the following amendments to the 2015 Plan: (i) increase to the authorized number of shares available for issuance by 4,312,500 shares and proportionately increase the share limit related to incentive stock options, (ii) provide limits on the total value of compensation that may be granted to any non-employee As of March 31, 2020, 4,678,379 shares were reserved for issuance under the 2015 Plan. The number of shares reserved for issuance under the 2015 Plan will increase automatically on January 1 of each calendar year 2016 through 2025 by the number of shares equal to 4% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31. The Company’s Board of Directors or Compensation Committee may reduce the amount of the increase in any particular year. The exercise price of each stock-based award issued under the 2015 Plan is required to be no less than the fair value of the Company’s capital stock. The vesting and exercise provisions of options or restricted awards granted are determined individually with each grant. Stock options have a 10-year 2008 Plan The Company granted options under the 2008 Stock Plan (2008 Plan) until July 2015 when it was terminated as to future awards, although it continues to govern the terms of options that remain outstanding under the 2008 Plan. The 2008 Plan provided for the granting of Incentive Stock Options (ISO), nonqualified stock options and stock purchase rights. In connection with the Board of Director’s approval of the 2015 Plan, all remaining shares available for future award under the 2008 Plan were transferred to the 2015 Plan, and the 2008 Plan was terminated. A summary of activity under the 2008 Plan, 2015 Plan and 2018 Plan and related information is as follows: Options Outstanding Shares Number Weighted- Weighted- Aggregate Outstanding - 51,514 326,023 $ 102.56 7.45 $ 11 Awards authorized 4,387,187 Options granted (1,435,857 ) 1,435,857 13.31 Options forfeited/cancelled 23,053 (23,053 ) 52.35 Outstanding - 3,025,897 1,738,827 $ 29.52 9.37 $ — Exercisable - 220,647 $ 114.63 6.23 $ — Vested and expected to vest - 1,738,827 $ 29.52 9.37 $ — The weighted-average grant date fair values of options granted during the three months ended March 31, 2020 was $9.81 per share, and $58.80 per share during the three months ended March 31, 2019. The aggregate intrinsic values of options exercised were $0.1 million for the three months ended March 31, 2019. No options were exercised for the three months ended March 31, 2020. The total grant date fair value of options vested for the three months ended March 31, 2020 was $1.6 million and $2.7 million during the three months ended March 31, 2019. As of March 31, 2020, total unrecognized stock-based compensation related to unvested stock options was $18.9 million. These costs are expected to be recognized over a remaining weighted-average period of 3.4 years as of March 31, 2020.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes The Company did not record a provision for U.S. federal income taxes for the three months ended March 31, 2020 because it expects to generate a loss for the year ended December 31, 2020. The income tax expense for the three months ended March 31, 2020 represented foreign taxes, and the income tax benefit for the three months ended March 31, 2019 related to foreign research and development tax credits. The Company’s net U.S. deferred tax assets continue to be offset by a full valuation allowance.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 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) and applicable rules and regulations of the Securities and Exchange Commission regarding interim financial reporting. Accordingly, they do not include all the information and notes required for complete financial statements and should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s Annual Report on Form 10-K 10-K These unaudited condensed consolidated financial statements and related disclosure have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020, or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2019 included herein was derived from the audited consolidated financial statements as of that date.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of stock options and the warrant issued, fair value of the securities issuance obligation, accruals such as research and development costs, and recoverability of the Company’s net deferred tax assets and related valuation allowance. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following shares of common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have been antidilutive: March 31, 2020 March 31, 2019 (in thousands) Series A warrants for common stock 7,802,241 — Series B warrants for common stock 2,574,727 — Options to purchase common stock 1,738,827 329,880 Warrant s 727,122 1,839 Total potential dilutive shares 12,842,917 331,719

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis	The following table sets forth the fair value of the Company’s financial assets measured on a recurring basis by level within the fair value hierarchy: March 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 132,963 $ — $ — $ 132,963 Restricted money market funds 300 — — 300 Total financial assets $ 133,263 $ — $ — $ 133,263 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 146,240 $ — $ — $ 146,240 Restricted money market funds 300 — — 300 Total financial assets $ 146,540 $ — $ — $ 146,540 Financial Liabilities Warrant liabilities $ — $ — $ 45,935 $ 45,935 Securities issuance obligation — — 10,485 10,485 Total financial liabilities $ — $ — $ 56,420 $ 56,420
Schedule of Fair Value Measurement Inputs and Valuation Techniques	The Company remeasured the fair value of the warrant liabilities at the time of reclassification to equity using the following assumptions: Series A Series B Expected term (in years) 5.0 2.1 Expected volatility 43 % 88 % Risk-free interest rate 1.57 % 1.53 % Expected dividend yield — % — % The warrant issuance obligation was remeasured using the following assumptions: Warrant Expected term (in years) 5.0 Expected volatility 43 % Risk-free interest rate 1.57 % Expected dividend yield — %
Schedule of Financial Liabilitites Fair Value of Recurring Basis Using Unobservable Inputs	The following table provides a summary of changes in the estimated fair values of the Company’s Level 3 financial liabilities: Series A Series B Warrant Common Total (in thousands) Balance, December 31, 2019 $ 32,616 $ 13,319 $ 3,036 $ 7,449 $ 56,420 Changes in fair value 11,597 4,643 152 1,333 17,725 Settlement of financial liabilities by equity issuance — — (3,188 ) (8,782 ) (11,970 ) Reclassification to equity (44,213 ) (17,962 ) — — (62,175 ) Balance, March 31, 2020 $ — $ — $ — $ — $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Cash and Cash Equivalents	Cash and cash equivalents consist of the following: March 31, 2020 December 31, (in thousands) Cash $ 571 $ 1,288 Cash equivalents: Money market accounts 132,963 146,240 Total cash and cash equivalents $ 133,534 $ 147,528
Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the condensed consolidated balance sheets to the amounts shown in the condensed consolidated statements of cash flows. March 31, 2020 March 31, (in thousands) Cash and cash equivalents $ 133,534 $ 90,908 Restricted cash included in other assets 300 300 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 133,834 $ 91,208
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following: March 31, December 31, (in thousands) Prepaid insurance $ 582 $ 918 Prepaid research and development project costs 581 853 Other receivables 156 190 Other 617 408 Total prepaid expenses and other current assets $ 1,936 $ 2,369
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: March 31, December 31, (in thousands) Software $ 364 $ 352 Leasehold improvements 112 112 Computer equipment 89 89 Furniture and fixtures 3 3 Property and equipment, gross 568 556 Less: accumulated depreciation (456 ) (443 ) Total property and equipment, net $ 112 $ 113
Summary of Accrued and Other Liabilities	Accrued and other liabilities consist of the following: March 31, December 31, (in thousands) Accrued research and development costs $ 2,777 $ 2,668 Accrued employee related costs 1,411 3,420 Accrued professional fees 1,162 817 Operating lease liability 175 187 Other 115 78 Total accrued and other liabilities $ 5,640 $ 7,170

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Schedule of Components of Lease Expense and Related Cash Flows	The components of lease expense and related cash flows for the three months ended March 31, 2020 and 2019 were as follows: Three Months Ended Three Months Ended (in thousands) Operating lease cost $ 51 $ 51 Short-term lease cost 22 29 73 80 Operating cash flows used for operating leases $ 52 $ 40
Schedule of Maturities Lease Liabilities under Leases Agreement	As of March 31, 2020, maturities of lease liability due under the lease agreement are as follows: Years Ending December 31: Operating Leases (in thousands) Remainder of 2020 $ 150 2021 203 2022 162 Total lease payments 515 Less imputed interest (42 ) Total $ 473

Common Stock Reserved for Iss_2

Common Stock Reserved for Issuance (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	March 31, December 31, Shares reserved under Series A warrant 7,802,241 7,802,241 Shares reserved under Series B warrant 2,574,727 2,574,727 Shares reserved for future option grants under equity plans 3,025,897 51,514 Outstanding stock options under equity incentive plans 1,738,827 326,023 Outstanding warrant 727,122 1,839 Shares reserved under the 2015 employee stock purchase plan 17,500 17,500 Shares reserved for conversion of Series A Preferred Stock — 7,803,273 Total common stock reserved for issuance 15,886,314 18,577,117

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Stock-based Compensation Expense for Employees and Non-employees	In the accompanying condensed consolidated statements of operations, the Company recognized stock-based compensation expense for its employees and non-employees Three Months Ended March 31, 2020 2019 Research and development $ 546 $ 1,184 General and administrative 372 515 Total stock-based compensation $ 918 $ 1,699
Schedule of Estimated Grant-date Fair Value of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions	The estimated grant-date fair values of all of the Company’s stock-based awards were calculated using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended March 31, 2020 2019 Expected term (in years) 5.7 – 6.7 5.3 – 6.9 Expected volatility 88 – 90 % 91 – 94 % Risk-free interest rate 0.6 – 1.2 % 2.5 – 2.6 % Expected dividend rate — % — %
Summary of Stock-Based Compensation Activity	A summary of activity under the 2008 Plan, 2015 Plan and 2018 Plan and related information is as follows: Options Outstanding Shares Number Weighted- Weighted- Aggregate Outstanding - 51,514 326,023 $ 102.56 7.45 $ 11 Awards authorized 4,387,187 Options granted (1,435,857 ) 1,435,857 13.31 Options forfeited/cancelled 23,053 (23,053 ) 52.35 Outstanding - 3,025,897 1,738,827 $ 29.52 9.37 $ — Exercisable - 220,647 $ 114.63 6.23 $ — Vested and expected to vest - 1,738,827 $ 29.52 9.37 $ —

The Company and Basis of Pres_2

The Company and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Cash and cash equivalents	$ 133,534	$ 147,528	$ 90,908

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	12,842,917	331,719
Series A Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	7,802,241
Series B Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	2,574,727
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	1,738,827	329,880
Warrants for Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	727,122	1,839

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets Measured on Recurring Basis (Detail) - Fair Value Measurements Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial Assets
Total financial assets	$ 133,263	$ 146,540
Financial Liabilities
Total financial liabilities		56,420
Warrant liabilities [Member]
Financial Liabilities
Total financial liabilities		45,935
Securities issuance obligation [Member]
Financial Liabilities
Total financial liabilities		10,485
Money Market Funds [Member]
Financial Assets
Total financial assets	132,963	146,240
Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	300	300
Level 1 [Member]
Financial Assets
Total financial assets	133,263	146,540
Level 1 [Member] | Money Market Funds [Member]
Financial Assets
Total financial assets	132,963	146,240
Level 1 [Member] | Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	$ 300	300
Level 3 [Member]
Financial Liabilities
Total financial liabilities		56,420
Level 3 [Member] | Warrant liabilities [Member]
Financial Liabilities
Total financial liabilities		45,935
Level 3 [Member] | Securities issuance obligation [Member]
Financial Liabilities
Total financial liabilities		$ 10,485

Fair Value Measurements - Summa

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

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Changes in Fair Values Level Financial Liabilities Recurring Basis Using Unobservable Inputs (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in fair value	$ 16,240
Reclassification to equity	62,175
Fair Value Measurements Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	56,420
Changes in fair value	17,725
Settlement of financial liabilities by securities issuance	(11,970)
Reclassification to equity	(62,175)
Ending Balance	0
Fair Value Measurements Recurring [Member] | Series A Warrant [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	32,616
Changes in fair value	11,597
Reclassification to equity	(44,213)
Ending Balance	0
Fair Value Measurements Recurring [Member] | Series B Warrant [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	13,319
Changes in fair value	4,643
Reclassification to equity	(17,962)
Ending Balance	0
Fair Value Measurements Recurring [Member] | warrant Issuance Obligation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	3,036
Changes in fair value	152
Settlement of financial liabilities by securities issuance	(3,188)
Ending Balance	0
Fair Value Measurements Recurring [Member] | Common stock Issuance Obligation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	7,449
Changes in fair value	1,333
Settlement of financial liabilities by securities issuance	(8,782)
Ending Balance	$ 0

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash	$ 571	$ 1,288
Cash equivalents:
Money market accounts	132,963	146,240
Total cash and cash equivalents	$ 133,534	$ 147,528	$ 90,908

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 133,534	$ 147,528	$ 90,908
Restricted cash included in other assets	300		300
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows	$ 133,834	$ 147,828	$ 91,208	$ 106,346

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid insurance	$ 582	$ 918
Prepaid research and development project costs	581	853
Other receivables	156	190
Other	617	408
Total prepaid expenses and other current assets	$ 1,936	$ 2,369

Balance Sheet Components - Su_4

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 568	$ 556
Less: accumulated depreciation	(456)	(443)
Total property and equipment, net	112	113
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	364	352
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	112	112
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	89	89
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3	$ 3

Balance Sheet Components - Su_5

Balance Sheet Components - Summary of Accrued and Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued research and development costs	$ 2,777	$ 2,668
Accrued employee related costs	1,411	3,420
Accrued professional fees	1,162	817
Operating lease liability	175	187
Other	115	78
Total accrued and other liabilities	$ 5,640	$ 7,170

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation	$ 13,000	$ 21,000

Leases - Additional Information

Leases - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020
Loss Contingencies [Line Items]
Weighted-average remaining lease term, operating lease (Year)	2 years 10 months 24 days
Weighted-average discount rate, Operating lease	6.50%
Vancouver Lease [Member] | Vancouver [Member]
Loss Contingencies [Line Items]
Operating lease agreement expiration date	Feb. 28, 2023
Additional lease term to be extended	5 years

Leases - Schedule of Components

Leases - Schedule of Components of Lease Expense and Related Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Operating lease cost	$ 51	$ 51
Short-term lease cost	22	29
Total Lease Cost	73	80
Operating cash flows used for operating leases	$ 52	$ 40

Leases - Schedule of Maturities

Leases - Schedule of Maturities Lease Liabilities under Leases Agreement (Detail) $ in Thousands	Mar. 31, 2020USD ($)
Leases [Abstract]
Remainder of 2020	$ 150
2021	203
2022	162
Total lease payments	515
Less imputed interest	(42)
Total	$ 473

Term Loan - Additional Informat

Term Loan - Additional Information (Detail) - Silicon Valley Bank [Member] - Term Loans [Member] $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Aug. 31, 2018Tranches	Mar. 31, 2020USD ($)$ / sharesshares	Mar. 31, 2019USD ($)	Dec. 18, 2019USD ($)
Debt Instrument [Line Items]
Number of tranches | Tranches	3
Loan agreement, description		Contemporaneously with executing the Loan Agreement, the Company drew down the first $5.0 million tranche.
Loan agreement, frequency of payments		monthly
Interest expense			$ 0.1
Tranche One [Member]
Debt Instrument [Line Items]
Aggregate principal amount of loans				$ 5
Amount borrowed		$ 5
Warrants to Purchase Common Stock [Member]
Debt Instrument [Line Items]
Warrants issued in connection with loan | shares		1,839
Excercise price of warrants or rights | $ / shares		$ 74.80
Warrant expiration date	Aug. 21, 2028

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Jan. 31, 2020$ / sharesshares	Aug. 31, 2018USD ($)	Oct. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2020USD ($)Paymentsshares	Dec. 31, 2019USD ($)	Jan. 31, 2017USD ($)
Carna License Agreement [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment					$ 270
Milestone payment					$ 4
Upfront payment paid				$ 0.9
Number of milestone payments recorded | Payments					0
CPF License Agreements [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment					$ 19.5
Milestone payment							$ 2
Upfront payment paid			$ 7
Additional milestone payment payable					319.5
CPF License Agreements [Member] | Phase One Clinical Trial [Member]
Loss Contingencies [Line Items]
Milestone payment					7.5
CPF License Agreements [Member] | Phase Two Clinical Trial [Member]
Loss Contingencies [Line Items]
Milestone payment					12
Asset Purchase Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid		$ 3
Aggregate milestone payment					190
Expense included research and development cost						$ 10.5
Additional Exepense included Research and development cost					$ 1.5
Asset Purchase Agreement [Member] | Gilead [Member]
Loss Contingencies [Line Items]
Stock issued, shares | shares	725,283
Number of securitites called by warrants and rights | shares	725,283
Asset Purchase Agreement Amendment [Member] | Gilead [Member]
Loss Contingencies [Line Items]
Stock issued, shares | shares	725,283
Number of securitites called by warrants and rights | shares					725,283
Excercise price of warrants or rights | $ / shares	$ 13.20

Common Stock Reserved for Iss_3

Common Stock Reserved for Issuance - Schedule of Common Stock Reserved for Issuance (Detail) - shares	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Total common stock reserved for future issuance	15,886,314	18,577,117
Series A Warrant [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	7,802,241	7,802,241
Series B Warrant [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	2,574,727	2,574,727
Equity Incentive Plans [Member]
Class of Stock [Line Items]
Awards outstanding	1,738,827	326,023
Total common stock reserved for future issuance	3,025,897	51,514
2015 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	17,500	17,500
Warrants to Purchase Common Stock [Member]
Class of Stock [Line Items]
Outstanding warrant	727,122	1,839
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance		7,803,273

Preferred Stock - Additional in

Preferred Stock - Additional information (Detail) - USD ($) $ / shares in Units, $ in Millions	Nov. 13, 2019	Mar. 31, 2020	Jan. 29, 2020	Dec. 31, 2019
Series A Convertible Voting Preferred Stock [Member]
Preferred stock, shares authorized		10,000,000		10,000,000
Preferred stock, par value		$ 0.001		$ 0.001
Preferred stock, shares outstanding		0		103,000
Stock issued, shares	103,000
Preferred stock voting rights		The Series A Preferred Stock will initially vote together with the Company's common stock on an as-converted basis. Holders of each Series A Preferred Stock will be entitled to one vote for each share of common stock into which their Series A Preferred Stock is then-convertible. Following the date the Series A Preferred Stock automatically converts into shares of the Company's common stock, except otherwise required by law, the Series A Preferred Stock will have no voting rights.
Preferred Stock converted into of the Company's common stock			7,803,273
Convertible Preferred Stock And Warrants And Underwritten Follow On Offering [Member]
Share issued price per share	$ 1,000
Proceeds from issuance of convertible preferred stock and warrants net of issuance cost	$ 97.7
Series A Preferred Stock [Member]
Share issued price per share		$ 1,000
Preferred stock conversion price per share		$ 13.20

Warrant Liabilities - Additiona

Warrant Liabilities - Additional information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Class of Warrant or Right [Line Items]
Non-cash expense on warrant liability | $	$ 16,240
Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants and rights outstanding term	5 years
Series B Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants and rights outstanding term	75 days
Exercise of Future Warrants Value | $	$ 34,000
Underwritten Follow On Offerings [Member] | Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Number of securitites called by warrants and rights | shares	7,802,241
Excercise price of warrants or rights | $ / shares	$ 13.20
Underwritten Follow On Offerings [Member] | Series B Warrants [Member]
Class of Warrant or Right [Line Items]
Number of securitites called by warrants and rights | shares	2,574,727
Excercise price of warrants or rights | $ / shares	$ 13.20

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock-based Compensation Expense for Employees and Non-employees (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 918	$ 1,699
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	546	1,184
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 372	$ 515

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Estimated Grant-date Fair Values of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, Minimum	88.00%	91.00%
Expected volatility, Maximum	90.00%	94.00%
Risk-free interest rate, Minimum	0.60%	2.50%
Risk-free interest rate, Maximum	1.20%	2.60%
Expected dividend rate	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 8 months 12 days	5 years 3 months 18 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 8 months 12 days	6 years 10 months 24 days

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jan. 21, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance		15,886,314		18,577,117
Common shares authorized to be issued during the period	4,312,500
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance		4,678,379
Stock option life in years		10 years
Stock option grants description		The number of shares reserved for issuance under the 2015 Plan will increase automatically on January 1 of each calendar year 2016 through 2025 by the number of shares equal to 4% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31.
Percentage threshold of outstanding shares increased annually under the plan		4.00%
2008 Plan, 2015 Plan and 2018 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair values of options granted		$ 9.81	$ 58.80
Aggregate intrinsic value of options exercised			$ 0.1
Total grant date fair value of options vested		$ 1.6	$ 2.7
Total unrecognized stock-based compensation related to unvested stock options		$ 18.9
Weighted-average period		3 years 4 months 24 days
Common shares authorized to be issued during the period		4,387,187
2018 Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance		37,500

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 21, 2020	Mar. 31, 2020	Dec. 31, 2019
Options Outstanding, Shares Available for Grant
Shares Available for Grant, Awards authorized	4,312,500
2008 Plan, 2015 Plan and 2018 Plan [Member]
Options Outstanding, Shares Available for Grant
Shares Available for Grant, Beginning balance		51,514
Shares Available for Grant, Awards authorized		4,387,187
Shares Available for Grant, Granted		(1,435,857)
Shares Available for Grant, forfeited/cancelled		23,053
Shares Available for Grant, Ending balance		3,025,897	51,514
Options Outstanding, Number of Shares Outstanding
Number of Shares Outstanding, Beginning balance		326,023
Number of Shares Outstanding, Options granted		1,435,857
Number of Shares Outstanding, Options forfeited/cancelled		(23,053)
Number of Shares Outstanding, Ending balance		1,738,827	326,023
Number of Shares Outstanding, Exercisable		220,647
Number of Shares Outstanding, Vested and expected to vest		1,738,827
Options Outstanding, Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance		$ 102.56
Weighted-Average Exercise Price Per Share, Options granted		13.31
Weighted-Average Exercise Price Per Share, Options forfeited/cancelled		52.35
Weighted-Average Exercise Price Per Share, Ending balance		29.52	$ 102.56
Weighted-Average Exercise Price Per Share, Exercisable		114.63
Weighted-Average Exercise Price Per Share, Vested and expected to vest		$ 29.52
Options Outstanding, Weighted-Average Remaining Contractual Term (Years)
Weighted-Average Remaining Contractual Term (Years)		9 years 4 months 13 days	7 years 5 months 12 days
Weighted-Average Remaining Contractual Term (Year), Exercisable		6 years 2 months 23 days
Weighted-Average Remaining Contractual Term (Year), Vested and expected to vest		9 years 4 months 13 days
Options Outstanding, Aggregate Intrinsic Value of Outstanding Options
Aggregate Intrinsic Value of Outstanding Options			$ 11

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020USD ($)
Income Tax Contingency [Line Items]
Federal Income Tax Expense (Benefit), Continuing Operations	$ 0