Viking Therapeutics (VKTX) 10-Q 28 Jul 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 15, 2021
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	VIKING THERAPEUTICS, INC.
Entity Central Index Key	0001607678
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		78,189,814
Entity File Number	001-37355
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-1073877
Entity Address, Address Line One	12340 El Camino Real
Entity Address, Address Line Two	Suite 250
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92130
City Area Code	858
Local Phone Number	704-4660
Document Quarterly Report	true
Document Transition Report	false
Common stock [Member]
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Security Exchange Name	NASDAQ
Trading Symbol	VKTX

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 8,829	$ 29,117
Short-term investments – available for sale	219,429	219,269
Prepaid clinical trial and preclinical study costs	8,254	7,276
Prepaid expenses and other current assets	1,150	442
Total current assets	237,662	256,104
Right-of-use assets	176	321
Deferred financing costs	7	48
Deposits		29
Total assets	237,845	256,502
Current liabilities:
Accounts payable	4,210	3,988
Other accrued liabilities	8,463	7,811
Lease liability, current	198	330
Total current liabilities	12,871	12,129
Lease liability, net of current portion		29
Total long-term liabilities		29
Total liabilities	12,871	12,158
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.00001 par value: 10,000,000 shares authorized at June 30, 2021 and December 31, 2020; no shares issued and outstanding at June 30, 2021 and December 31, 2020
Common stock, $0.00001 par value: 300,000,000 shares authorized at June 30, 2021 and December 31, 2020; 78,189,814 and 73,215,940 shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	1	1
Additional paid-in capital	422,745	412,589
Accumulated deficit	(197,583)	(168,192)
Accumulated other comprehensive loss	(189)	(54)
Total stockholders’ equity	224,974	244,344
Total liabilities and stockholders’ equity	$ 237,845	$ 256,502

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	78,189,814	73,215,940
Common stock, shares outstanding	78,189,814	73,215,940

Statements of Operations and Co

Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenues	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	12,804	7,780	24,340	15,766
General and administrative	2,737	2,826	5,430	5,787
Total operating expenses	15,541	10,606	29,770	21,553
Loss from operations	(15,541)	(10,606)	(29,770)	(21,553)
Other income (expense):
Amortization of financing costs	(21)	(20)	(41)	(65)
Interest income, net	181	1,040	420	2,344
Realized gain on investments, net	0	14	0	15
Total other income, net	160	1,034	379	2,294
Net loss	(15,381)	(9,572)	(29,391)	(19,259)
Other comprehensive loss, net of tax:
Unrealized gain (loss) on securities	(85)	1,145	(135)	321
Comprehensive loss	$ (15,466)	$ (8,427)	$ (29,526)	$ (18,938)
Basic and diluted net loss per common share	$ (0.20)	$ (0.13)	$ (0.38)	$ (0.27)
Weighted-average shares used to compute basic and diluted net loss per share	77,896,594	72,487,490	76,348,113	72,421,959

Statements of Stockholders' Equ

Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2019	$ 277,119	$ 1	$ 405,803	$ (128,697)	$ 12
Balance (in shares) at Dec. 31, 2019		72,413,602
Employee stock-based compensation	3,301		3,301
Shares withheld related to employee tax withholding	(127)		(127)
Shares withheld related to employee tax withholding (in shares)		(17,124)
Issuance of common stock under employee stock plans	239		239
Issuance of common stock under employee stock plans (in shares)		112,961
Issuance of common stock from warrant exercises	353		353
Issuance of common stock from warrant exercises (in shares)		248,903
Unrealized gain (loss) on investments	321				321
Net loss	(19,259)			(19,259)
Balance at Jun. 30, 2020	261,947	$ 1	409,569	(147,956)	333
Balance (in shares) at Jun. 30, 2020		72,758,342
Balance at Mar. 31, 2020	268,283	$ 1	407,478	(138,384)	(812)
Balance (in shares) at Mar. 31, 2020		72,562,863
Employee stock-based compensation	1,648		1,648
Issuance of common stock under employee stock plans	227		227
Issuance of common stock under employee stock plans (in shares)		51,934
Issuance of common stock from warrant exercises	216		216
Issuance of common stock from warrant exercises (in shares)		143,545
Unrealized gain (loss) on investments	1,145				1,145
Net loss	(9,572)			(9,572)
Balance at Jun. 30, 2020	261,947	$ 1	409,569	(147,956)	333
Balance (in shares) at Jun. 30, 2020		72,758,342
Balance at Dec. 31, 2020	244,344	$ 1	412,589	(168,192)	(54)
Balance (in shares) at Dec. 31, 2020		73,215,940
Employee stock-based compensation	3,068		3,068
Shares withheld related to employee tax withholding	(473)		(473)
Shares withheld related to employee tax withholding (in shares)		(81,016)
Issuance of common stock under employee stock plans	498		498
Issuance of common stock under employee stock plans (in shares)		326,578
Issuance of common stock from warrant exercises	7,063		7,063
Issuance of common stock from warrant exercises (in shares)		4,728,312
Unrealized gain (loss) on investments	(135)				(135)
Net loss	(29,391)			(29,391)
Balance at Jun. 30, 2021	224,974	$ 1	422,745	(197,583)	(189)
Balance (in shares) at Jun. 30, 2021		78,189,814
Balance at Mar. 31, 2021	237,223	$ 1	419,528	(182,202)	(104)
Balance (in shares) at Mar. 31, 2021		77,178,081
Employee stock-based compensation	1,491		1,491
Issuance of common stock under employee stock plans	343		343
Issuance of common stock under employee stock plans (in shares)		89,646
Issuance of common stock from warrant exercises	1,383		1,383
Issuance of common stock from warrant exercises (in shares)		922,087
Unrealized gain (loss) on investments	(85)				(85)
Net loss	(15,381)			(15,381)
Balance at Jun. 30, 2021	$ 224,974	$ 1	$ 422,745	$ (197,583)	$ (189)
Balance (in shares) at Jun. 30, 2021		78,189,814

Statements of Cash Flows (Unaud

Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities
Net loss			$ (29,391)	$ (19,259)
Adjustments to reconcile net loss to net cash used in operating activities
Amortization of investment premiums, net			2,179	1,489
Amortization of financing costs	$ 21	$ 20	41	65
Stock-based compensation	1,491	1,648	3,068	3,301
Amortization of right-of-use assets			145	136
Interest expense related to operating lease liability			9	18
Realized gain on investments				(15)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(1,658)	238
Accrued interest, net of interest received on maturity of investments			593	963
Accounts payable			223	777
Other accrued liabilities			652	1,484
Lease liability			(171)	(165)
Net cash used in operating activities			(24,310)	(10,968)
Cash flows from investing activities
Purchases of investments			(108,278)	(138,991)
Proceeds from maturities of investments			105,211	159,923
Net cash provided by (used in) investing activities			(3,067)	20,932
Cash flows from financing activities
Public offering and financing costs				(26)
Value of shares withheld related to employee tax withholding			(473)	(127)
Proceeds from warrant and option exercises and stock issuances under employee stock purchase plan			7,562	602
Net cash provided by financing activities			7,089	449
Net increase (decrease) in cash and cash equivalents			(20,288)	10,413
Cash and cash equivalents beginning of period			29,117	8,377	$ 8,377
Cash and cash equivalents end of period	$ 8,829	$ 18,790	8,829	18,790	$ 29,117
Supplemental disclosure of non-cash investing and financing transactions
Unpaid deferred public offering and other financing costs			$ 50	$ 50

Organization, Liquidity and Man

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies	1. Organization, Liquidity and Management’s Plan, and Summary of Significant Accounting Policies The Company Viking Therapeutics, Inc., a Delaware corporation (the “Company”), is a clinical-stage biopharmaceutical company focused on the development of novel therapies for metabolic and endocrine disorders. The Company was incorporated under the laws of the State of Delaware on September 24, 2012 and its principal executive offices are located in San Diego, California. Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying balance sheet as of June 30, 2021, statements of operations for the three and six months ended June 30, 2021 and 2020, statements of stockholders’ equity for the three and six months ended June 30, 2021 and 2020 and statements of cash flows for the six months ended June 30, 2021 and 2020 are unaudited. These unaudited financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. These financial statements should be read in conjunction with the audited financial statements and the accompanying notes for the year ended December 31, 2020 contained in the Annual Report on Form 10-K filed by the Company with the SEC on February 17, 2021. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of June 30, 2021, the results of operations for the three and six months ended June 30, 2021 and 2020, the statements of stockholders’ equity for the three and six months ended June 30, 2021 and 2020 and the statements of cash flows for the six months ended June 30, 2021 and 2020. The December 31, 2020 balance sheet included herein was derived from the audited financial statements, but it does not include all disclosures or notes required by GAAP for complete financial statements. The financial data and other information disclosed in these notes to the financial statements related to the three and six months ended June 30, 2021 and 2020 are unaudited. Interim results are not necessarily indicative of results for an entire year. Risks and Uncertainties The Company is subject to risks and uncertainties as a result of the COVID-19 pandemic. The extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the responses that the Company, other businesses and governments are taking continue to evolve. Furthermore, capital markets and economies worldwide have also been negatively impacted by the COVID-19 pandemic, and it is possible that it could cause a local and/or global economic slowdown or recession. Policymakers around the globe have responded with fiscal policy actions to support the healthcare industry and economy as a whole. The magnitude and overall effectiveness of these actions remain uncertain. In addition, the Company’s clinical trials have been affected by and may continue to be affected by the COVID-19 pandemic. Clinical site initiation and patient enrollment have been and may continue to be delayed due to prioritization of hospital resources toward the COVID-19 pandemic. Some patients have not been and others may not be able to comply with clinical trial protocols if quarantines impede patient movement or interrupt healthcare services. Similarly, any inability to recruit and retain patients and principal investigators and site staff who, as healthcare providers, may have heightened exposure to COVID-19, may adversely impact the Company’s clinical trial operations. The severity of the impact of the COVID-19 pandemic on the Company’s business will depend on a number of factors, including, but not limited to, the duration and severity of the pandemic and the extent and severity of the impact on the Company’s service providers, suppliers, contract research organizations (“CROs”) and the Company’s clinical trials, all of which are uncertain and cannot be predicted. As of the date of the issuance of the Company’s financial statements, the extent to which the COVID-19 pandemic may materially impact the Company’s financial condition, liquidity or results of operations is uncertain. Reclassification Certain amounts reported in prior years in the financial statements have been reclassified to conform to the current year’s presentation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying financial statements. Significant estimates made in preparing these financial statements relate to accounting for an operating lease and certain commitments. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. Investments Available-for-Sale Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income (loss). The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. The amortization of premiums and accretion of discounts is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income (expense). The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured depository institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity. Prepaid Clinical Trial and Preclinical Study Costs Prepaid clinical trial and preclinical study costs represent advance payments by the Company for future clinical trial and preclinical study services to be performed by the clinical research organization and other research organizations. Such amounts are recognized as research and development expense as the related clinical trial and preclinical study services are performed. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) assets, and lease liability obligations are included in the Company’s balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liability obligations represent its obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company uses the implicit rate when readily determinable. The ROU asset also includes any lease payments made and excludes lease incentives and lease direct costs. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Please refer to Note 4 for additional information. Deferred Financing Costs Deferred financing costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. Costs related to the public sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. Costs related to the private sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are amortized over the term of the applicable purchase agreement. Revenue Recognition The Company has not recorded any revenues since its inception. However, in the future, the Company may enter into collaborative research and licensing agreements, under which the Company could be eligible for payments made in the form of upfront license fees, research funding, cost reimbursement, contingent event-based payments and/or royalties. On January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers and all related amendments (“ASC 606” or “the revenue standard”). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-s Research and Development Expenses All costs of research and development are expensed in the period incurred. Research and development costs primarily consist of fees paid to CROs and clinical trial sites, employee and consultant related expenses, which include salaries, benefits and stock-based compensation for research and development personnel, external research and development expenses incurred pursuant to agreements with third-party manufacturing organizations, facilities costs, travel costs, dues and subscriptions, depreciation and materials used in preclinical studies, clinical trials and research and development. The Company estimates its preclinical study and clinical trial expenses based on the services it received pursuant to contracts with research institutions and CROs that conduct and manage preclinical studies and clinical trials on the Company’s behalf. Clinical trial-related contracts vary significantly in length, and may be for a fixed amount based on milestones or deliverables, a variable amount based on actual costs incurred, capped at a certain limit, or a combination of these elements. The Company accrues service fees based on work performed, which relies on estimates of total costs incurred based on milestones achieved, patient enrollment and other events. The majority of the Company’s service providers invoice the Company in arrears, and to the extent that amounts invoiced differ from its estimates of expenses incurred, the Company accrues for additional costs. The financial terms of these agreements vary from contract to contract and may result in uneven expenses and payment flows. Preclinical study and clinical trial expenses include: • fees paid to CROs, consultants and laboratories in connection with preclinical studies; • fees paid to CROs, clinical trial sites, investigators and consultants in connection with clinical trials; and • fees paid to contract manufacturers and service providers in connection with the production, testing and packaging of active pharmaceutical ingredients and drug materials for preclinical studies and clinical trials. Payments under some of these agreements depend on factors such as the milestones accomplished, including enrollment of certain numbers of patients, site initiation and the completion of clinical trial milestones. To date, the Company has not experienced any events requiring it to make material adjustments to its accruals for service fees. If the Company does not identify costs that it has begun to incur or if it underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates, which could materially affect its results of operations. Adjustments to the Company’s accruals are recorded as changes in estimates become evident. Furthermore, based on amounts invoiced to the Company by its service providers, the Company may also record payments made to those providers as prepaid expenses that will be recognized as expense in future periods as services are rendered. Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred to general and administrative expense, as recoverability of such expenditures is uncertain. Stock-Based Compensation The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model (the “Black-Scholes model”). The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of the Company’s common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the Company’s 2014 Employee Stock Purchase Plan (the “ESPP”), the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, as an employee elects to increase his or her contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods. Income Taxes The Company accounts for its income taxes using the liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the basis used for financial reporting and income tax reporting purposes. Deferred income taxes are provided based on the enacted tax rates in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more likely than not that the Company will not realize those tax assets through future operations. FASB Accounting Standards Codification Topic 740-10, Income Taxes The Company’s policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense. Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, the Company currently does not have any deemed common share equivalents; therefore, its basic and diluted net loss per share calculations are the same. The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ (15,381 ) $ (9,572 ) $ (29,391 ) $ (19,259 ) Denominator: Weighted-average common shares outstanding 78,079,689 72,670,585 76,531,208 72,605,054 Less: Weighted-average shares subject to repurchase (183,095 ) (183,095 ) (183,095 ) (183,095 ) Denominator for basic and diluted net loss per share 77,896,594 72,487,490 76,348,113 72,421,959 Net loss per share: Basic and diluted $ (0.20 ) $ (0.13 ) $ (0.38 ) $ (0.27 ) Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of June 30, 2021 2020 Common stock warrants 487,087 5,592,398 Restricted stock units 1,047,155 795,695 Common stock subject to repurchase 183,095 183,095 Common stock options 3,917,509 3,429,123 5,634,846 10,000,311 Segments The Company operates in only one segment. Management uses cash flows as the primary measure to manage its business and does not segment its business for internal reporting or decision-making purposes.

Investments in Marketable Secur

Investments in Marketable Securities	6 Months Ended
	Jun. 30, 2021
Investments Debt And Equity Securities [Abstract]
Investments in Marketable Securities	2. Investments in Marketable Securities The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. This policy also limits the amount of credit exposure to any one issue or type of instrument. As of June 30, 2021 and December 31, 2020, the Company’s investments were in government money market funds, certificates of deposit, commercial paper, corporate debt securities and government debt securities. There were no sales of available-for-sale securities during the three and six months ended June 30, 2021 or during the year ended December 31, 2020. Investments classified as available-for-sale as of June 30, 2021 consisted of the following (in thousands): As of June 30, 2021 Amortized Cost Gross Unrealized Gains (1) Gross Unrealized Losses (1) Aggregate Estimated Fair Value Certificates of deposit (2) $ 510 $ — $ — $ 510 Commercial paper (2) $ 48,705 $ — $ — $ 48,705 Corporate debt securities (2) $ 161,325 $ 25 $ (205 ) $ 161,145 Government debt securities (2) $ 9,077 — (8 ) 9,069 $ 219,617 $ 25 $ (213 ) $ 219,429 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At June 30, 2021, there were 28 securities in an unrealized gain position and there were 66 securities in an unrealized loss position. The unrealized gains were less than $6,000 individually and $25,000 in the aggregate. (2) At June 30, 2021, none of these securities were classified as cash and cash equivalents on the Company’s balance sheet, and $44.2 Investments classified as available-for-sale as of December 31, 2020 consisted of the following (in thousands): As of December 31, 2020 Amortized Cost Gross Unrealized Gains (1) Gross Unrealized Losses (1) Aggregate Estimated Fair Value Commercial paper (2) $ 27,973 $ — $ — $ 27,973 Corporate debt securities (2) $ 185,711 $ 94 $ (136 ) $ 185,669 Government debt securities (2) $ 5,639 $ — $ (12 ) $ 5,627 $ 219,323 $ 94 $ (148 ) $ 219,269 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At December 31, 2020, there were 38 securities in an unrealized gain position and 80 securities in an unrealized loss position The unrealized losses were less than $21,000 individually and $148,000 in the aggregate. (2) At December 31, 2020, none of these securities were classified as cash and cash equivalents on the Company’s balance sheet and $53.4 million of the corporate debt securities were scheduled to mature outside of one year.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, investments and accounts payable. The carrying amounts reported in the accompanying balance sheets for cash and cash equivalents and accounts payable approximate fair value because of the short-term maturity of those instruments. Fair value measurements are classified and disclosed in one of the following three categories: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. 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. As of June 30, 2021 and December 31, 2020, all of the Company’s financial assets that were subject to fair value measurements were valued using observable inputs. The Company’s financial assets valued based on Level 1 inputs consist of money market funds. The Company’s financial assets valued based on Level 2 inputs consist of certificates of deposit, commercial paper, corporate debt securities and government debt securities, which consist of investments in highly rated investment-grade corporations. The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. This policy also limits the amount of credit exposure to any one issue or type of instrument. As of June 30, 2021, the Company’s investments were in government money market funds, certificates of deposit, commercial paper, corporate debt securities and government debt securities. The fair values of the Company’s financial instruments are presented below (in thousands): Fair Value Measurements at June 30, 2021 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: Government money market funds $ 5,492 $ 5,492 $ — $ — Short-term investments Certificates of deposit 510 — 510 — Commercial paper, available-for-sale 48,705 — 48,705 — Corporate debt securities, available-for-sale 161,145 — 161,145 — Government debt securities, available-for-sale 9,069 — 9,069 — Total financial assets $ 224,921 $ 5,492 $ 219,429 $ — Fair Value Measurements at December 31, 2020 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: Government money market funds $ 26,868 $ 26,868 $ — $ — Short-term investments Commercial paper, available for sale 27,973 — 27,973 — Corporate debt securities, available-for-sale 185,669 — 185,669 — Government debt securities, available-for-sale 5,627 — 5,627 — Total financial assets $ 246,137 $ 26,868 $ 219,269 $ —

Operating Leases - ROU Assets a

Operating Leases - ROU Assets and Lease Liability Obligations	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Operating Leases - ROU Assets and Lease Liability Obligations	4. Operating Leases – ROU Assets and Lease Liability Obligations The Company has only one operating lease, which is for office space that expires in January 2022. Below is a summary of the Company’s ROU assets and lease liabilities as of June 30, 2021 and December 31, 2020 (in thousands, except for years and %): June 30, December 31, 2021 2020 Right-of-use assets $ 176 $ 321 Lease liability obligations, current $ 198 $ 330 Lease liability obligations, less current portion $ — 29 Total lease liability obligations $ 198 $ 359 Weighted-average remaining lease term 0.58 years 1.08 years Weighted-average discount rate 6.00 % 6.00 % During the three and six months ended June 30, 2021, the Company recognized $77,000 and $154,000 in operating lease expenses, respectively, which are included in operating expenses in the Company’s statement of operations. During the three and six months ended June 30, 2020, the Company recognized $77,000 and $154,000 in operating lease expenses, respectively, which are included in operating expenses in the Company’s statement of operations. Approximate future minimum lease payments for the Company’s ROU assets over the remaining lease period as of June 30 , 2021 are as follows (in thousands): Remainder of 2021 $ 173 2022 29 Total minimum lease payments $ 202 Less: amount representing interest $ (4 ) Total lease liability obligations $ 198 The operating lease provides the Company with an option to extend the term of the lease for a period of three years beyond the expiration date of January 2022. If the option is exercised, the renewal term will be upon the same terms and conditions as the original agreement, except that the base rent will be equal to the prevailing market rate as determined pursuant to the terms of the lease. The option to extend the operating lease was not recognized as part of the Company’s lease liability and right-of-use assets.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Stockholders' Equity	5. Stockholders’ Equity Preferred Stock The Company is authorized to issue up to 10,000,000 shares of preferred stock, $0.00001 par value per share, with no shares of preferred stock outstanding as of June 30, 2021 and December 31, 2020. The Company’s Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company may issue without further action by the stockholders of the Company. Common Stock The Company is authorized to issue up to 300,000,000 shares of common stock, $0.00001 par value per share. In February 2014, the Company entered into a stock purchase agreement with one of its founders. The agreement provided for the purchase of 1,000,000 shares of the Company’s common stock at a price per share of $0.01 in exchange for future services to be rendered to the Company as measured by certain performance criteria. The shares were subject to a repurchase option and were to vest in two tranches of 500,000 shares each, upon achievement of the performance target or upon a triggering event as defined. The Company determined that the fair value of the unrecognized expense was $168,000 at February 20, 2014, the grant date. In May 2015, the Company repurchased 633,810 of these shares at a purchase price of $0.00001 per share. In connection with the repurchase, the Company entered into an amendment to the stock purchase agreement to provide that the remaining 366,190 shares will continue to vest in two tranches of 183,095 shares each, upon achievement of the performance target or upon a triggering event as defined. The pro rata grant date fair value of the unrecognized expense is $62,000. In October 2015, a triggering event became probable of occurrence and was deemed achieved in October 2016; therefore, the Company recorded $31,000 of stock-based compensation expense through December 31, 2016. No similar expense was recognized during the three and six months ended June 30, 2021 and 2020. The Company will continue to reassess at each reporting period whether it is probable that the performance target will be achieved, and if and when it is deemed probable, the Company will begin to record compensation expense using the fair value to determine stock-based compensation expense in its financial statements over the period the Company estimates the performance target will actually be achieved. On September 28, 2017, the Company entered into a purchase agreement with Lincoln Park Capital Fund, LLC (“LPC”) pursuant to which, on September 29, 2017, the Company sold to LPC 701,282 shares of common stock (the “LPC Initial Shares”) at a price of approximately $1.78 per share for an aggregate purchase price of $1.3 million, pursuant to the Company’s effective shelf registration statement on Form S-3 (File No. 333-212134), filed with the SEC on June 20, 2016, as amended by Amendment No. 1 thereto filed with the SEC on July 26, 2016, and declared effective on July 26, 2016, and the prospectus supplement thereto dated September 28, 2017. On September 28, 2017, the Company also entered into a purchase agreement (the “Commitment Purchase Agreement”) and a registration rights agreement with LPC, pursuant to which the Company had the right to sell to LPC up to $15.0 million in shares of common stock, subject to certain limitations and conditions set forth in the Commitment Purchase Agreement. Upon the satisfaction of the conditions in the Commitment Purchase Agreement (the “Commencement”), which occurred on October 26, 2017, the Company has the right, from time to time at its sole discretion over the 30-month period from and after the first day of the month following the Commencement, to direct LPC to purchase up to 75,000 shares of common stock on any business day (subject to certain limitations contained in the Commitment Purchase Agreement), with such amounts increasing based on certain threshold prices set forth in the Commitment Purchase Agreement; however, not to exceed $1.0 million in total purchase proceeds per purchase date. The purchase price of shares of common stock that the Company elects to sell to LPC pursuant to the Commitment Purchase Agreement will be based on the market prices of the common stock at the time of such purchases as set forth in the Commitment Purchase Agreement. In addition to regular purchases, as described above, the Company may also direct LPC to purchase additional amounts as accelerated purchases or as additional purchases if the closing sale price of the common stock is not below certain threshold prices, as set forth in the Commitment Purchase Agreement. In all instances, the Company may not sell shares of its common stock to LPC under the Commitment Purchase Agreement if it would result in LPC beneficially owning more than 4.99 % of the common stock. As consideration for LPC’s commitment to purchase shares of common stock pursuant to the Commitment Purchase Agreement, the Company issued to LPC 100,000 shares of common stock (the “LPC Commitment Shares”) . From inception of the Commitment Purchase Agreement through December 31, 2017, 343,051 shares were issued pursuant to the Commitment Purchase Agreement resulting in aggregate gross proceeds of $ 802,000 in addition to the LPC Initial Shares and the LPC Commitment Shares. In May 2020, the Company extended the termination date of the Commitment Purchase Agreement to May 1, 2023. No additional shares were issued during the year s ended December 31, 2018 through 20 20 or during the three and six months ended June 30 , 2021 . On August 1, 2019, the Company entered into an At-The-Market Equity Offering Sales Agreement (the “ATM Agreement”) with Stifel, Nicolaus & Company, Incorporated and Oppenheimer & Co. Inc. On March 17, 2020, the Company’s Board of Directors authorized a stock repurchase program, whereby the Company may purchase up to $50.0 million in shares of its common stock and outstanding warrants to purchase its common stock, over a period of up to two years (the “Repurchase Program”). The Repurchase Program may be carried out at the discretion of a committee of the Company’s Board of Directors through open market purchases, one or more Rule 10b5-1 trading plans, block trades and in privately negotiated transactions. Through June 30, 2021, no shares of the Company’s common stock or warrants to purchase its common stock were repurchased by the Company under the Repurchase Program. Shares repurchased by the Company under the Repurchase Program, if any, are expected to be held in treasury until such time as they are reissued or retired by the Company. During the three months ended June 30, 2021 and 2020, the Company issued an aggregate of 29,896 and 20,809 shares of its common stock, respectively, to certain employees pursuant to the ESPP.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	6. Stock-Based Compensation 2014 Plan . The Company’s 2014 Equity Incentive Plan (the “2014 Plan”) provides that the compensation committee of the Company’s Board of Directors (the “Compensation Committee”) may grant or issue stock options, stock appreciation rights, restricted shares, restricted stock units and unrestricted shares, deferred share units, performance and cash-settled awards and dividend equivalent rights to participants under the 2014 Plan. Initially, a total of 1,527,770 shares of the Company’s common stock were reserved for issuance pursuant to the 2014 Plan. The number of shares available for issuance under the 2014 Plan will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 3.5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year. The shares of common stock deliverable pursuant to awards under the 2014 Plan are authorized but unissued shares of the Company’s common stock, or shares of the Company’s common stock that the Company otherwise holds in treasury or in trust. Any shares of the Company’s common stock underlying awards that are settled in cash or otherwise expire, or are forfeited, terminated or cancelled (including pursuant to an exchange program established by the Compensation Committee) prior to the issuance of stock will again be available for issuance under the 2014 Plan. In addition, shares of the Company’s common stock that are withheld (or not issued) in payment of the exercise price or taxes relating to an award, and shares of the Company’s common stock equal to the number surrendered in payment of any exercise price or withholding taxes relating to an award, will again be available for issuance under the 2014 Plan. As of December 31, 2020, there were 4,081,253 shares of the Company’s common stock available for grant and, effective January 1, 2021, an additional 2,562,557 shares of the Company’s common stock were added to the number of shares reserved for grant under the 2014 Plan in accordance with the terms of the 2014 Plan. As of June 30, 2021, there were 5,514,166 shares of the Company’s common stock available for grant under the 2014 Plan. ESPP . Initially, a total of 458,331 shares of the Company’s common stock were reserved for issuance pursuant to the ESPP. The number of shares available for issuance under the ESPP will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year. The shares of common stock available for purchase pursuant to the ESPP are authorized but unissued shares of the Company’s common stock, shares of the Company’s common stock that the Company otherwise holds in treasury or shares of the Company’s common stock that were purchased on the open market in arms’ length transactions in accordance with applicable securities laws. Shares of the Company’s common stock will be offered for purchase under the ESPP as determined by the Compensation Committee through a series of successive offerings that each have a term of 24 months and consist of four consecutive purchase periods of six months each. Prior to the commencement of any future offering under the ESPP, the Compensation Committee may determine that the current offering shall end, may commence a new offering on the first day after the end of such terminal purchase period (or any desired later date), and may decide that future offerings will consist of one or more consecutive purchase periods, each to be of such duration as determined by the Compensation Committee; however, no offering will exceed 27 months and no purchase period will exceed one year. Each employee of the Company who (1) is an employee on the first date of any offering under the ESPP, (2) is customarily scheduled to work for more than 20 hours per week and more than five months per calendar year, and (3) meets such other criteria as may be determined by the Compensation Committee (consistent with Section 423 of the Internal Revenue Code of 1986, as amended), is eligible to participate in the ESPP for each purchase period within such offering. The purchase price per share of the Company’s common stock under the ESPP may not be less than, and will initially be equal to, the lesser of: (1) 85% of the fair market value per share of the Company’s common stock on the first day of the offering, or (2) 85% of the fair market value per share of the Company’s common stock on the date the purchase right is exercised, which will be the last day of the applicable purchase period. As of December 31, 2020, there were 2,289,561 shares of the Company’s common stock available for issuance and, effective January 1, 2021, an additional 732,159 shares of the Company’s common stock were added to the number of shares reserved for issuance under the ESPP in accordance with the terms of the ESPP. As of June 30, 2021, there were 2,991,824 shares of the Company’s common stock available for issuance under the ESPP. The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model. The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of its common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the ESPP, the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, then as an employee elects to increase their contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods. During the three and six months ended June 30, 2021 and 2020, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Stock-based compensation expense by type of award: Stock options $ 774 $ 859 $ 1,600 $ 1,683 Restricted stock and restricted stock units 655 733 1,342 1,497 Employee stock purchase plan 62 56 126 121 Total stock-based compensation expense included in expenses $ 1,491 $ 1,648 $ 3,068 $ 3,301 Stock-based compensation expense by line item: Research and development expenses $ 347 $ 404 $ 782 $ 724 General and administrative expenses 1,144 1,244 2,286 2,577 Total stock-based compensation expense included in expenses $ 1,491 $ 1,648 $ 3,068 $ 3,301 The following table sets forth the Company’s unrecognized stock-based compensation expense, net of estimated forfeitures, by type of award and the weighted-average period over which that expense is expected to be recognized (in thousands, except for years): As of June 30, 2021 Unrecognized Expense, Net of Estimated Forfeitures Weighted- average Recognition Period (in years) Type of award: Stock options $ 6,091 2.46 Restricted stock and restricted stock units $ 4,844 1.67 The following table is a summary of restricted stock activity during the six months ended June 30, 2021: Shares of Restricted Stock Weighted- Average Grant Date Fair Value Unvested at December 31, 2020 183,095 $ 0.17 Granted — $ — Vested — $ — Forfeited — $ — Unvested at June 30, 2021 183,095 $ 0.17 The following table summarizes restricted stock unit activity during the six months ended June 30, 2021: Shares Subject to Restricted Stock Units Weighted- Average Grant Date Value Unvested at December 31, 2020 679,363 $ 7.65 Granted 588,820 $ 5.80 Vested (192,229 ) $ 7.34 Forfeited (28,799 ) $ 6.07 Unvested at June 30, 2021 1,047,155 $ 6.71 In January 2019, the Company issued 221,600 performance-based restricted stock units (“PRSU awards”) to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100% of the PRSU awards vesting upon the achievement of three of the milestones over a four-year In January 2020, the Company issued 244,000 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100% of the PRSU awards vesting upon the achievement of three of the milestones over a four-year In January 2021, the Company issued 205,500 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100% of the PRSU awards vesting upon the achievement of three of the milestones over a four-year 133.3 % of the PRSU vesting upon the achievement of all four milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of June 30 , 2021, 7,500 PRSU awards were forfeited, none of the four milestones has been met and three of the four milestones were deemed probable of achievement, resulting in the Company recording stock-based compensation expense of $ and $ 282,000 during the three and six months ended June 30 , 2021 , respectively . The following table summarizes stock option activity during the six months ended June 30, 2021: Shares Subject to Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Options outstanding at December 31, 2020 3,371,323 $ 5.57 Granted 827,020 $ 5.80 Exercised (104,453 ) $ 3.30 375,000 Cancelled (176,381 ) $ 6.96 Options outstanding at June 30, 2021 3,917,509 $ 5.62 7.61 4,966,000 Options exercisable at June 30, 2021 2,226,229 $ 4.92 6.50 4,626,000 The Company received $345,000 and $108,000 in cash proceeds from exercises of stock options during the six months ended June 30, 2021 and 2020, respectively. Compensation cost for stock options granted to employees is based on the estimated grant date fair value and is recognized ratably over the vesting period of the applicable option. The estimated per share weighted average fair value of stock options granted to employees during the six months ended June 30, 2021 was $4.09. As stock-based compensation expense recognized is based on options ultimately expected to vest, the fair value of each employee option grant during the six months ended June 30, 2021 was estimated on the date of grant using the Black-Scholes model with the following weighted average assumptions: Six Months Ended June 30, 2021 Expected volatility 83.92 % Expected term (in years) 6.09 Risk-free interest rate 0.52 % Expected dividend yield 0 % Expected Volatility. The expected volatility rate used to value stock option grants is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the pharmaceutical and biotechnology industry in a similar stage of development to the Company. Expected Term . The Company elected to utilize the “simplified” method for “plain vanilla” options to value stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. Risk-free Interest Rate . The risk-free interest rate assumption was based on zero-coupon U.S. Treasury instruments that had terms consistent with the expected term of the Company’s stock option grants. Expected Dividend Yield . The Company has never declared or paid any cash dividends and does not presently plan to pay cash dividends in the foreseeable future. Forfeitures are accounted for as actual forfeitures occur. Since the Company had a net operating loss carryforward as of June 30, 2021, no excess tax benefits for the tax deductions related to stock-based awards were recognized in the Statements of Operations.

Warrants

Warrants	6 Months Ended
	Jun. 30, 2021
Warrants And Rights Note Disclosure [Abstract]
Warrants	7. Warrants On April 13, 2016, pursuant to an underwritten public offering (the “April 2016 Offering”), the Company sold 7,500,000 shares of its common stock and warrants to purchase up to 7,500,000 shares of its common stock at a public offering price of $1.25 per share of common stock and related warrant. The warrants had an exercise price of $1.50 per share of common stock, were immediately exercisable upon issuance and expired on April 13, 2021. Additionally, on April 13, 2016, the underwriters for the April 2016 Offering partially exercised the over-allotment option for warrants to purchase an additional 1,125,000 shares of the Company’s common stock at a public offering price of $0.01 per warrant to purchase a share of common stock. Warrants to purchase an aggregate of 922,087 and 3,618,312 shares were exercised during the three and six months ended June 30, respectively, and warrants to purchase an aggregate of 29,101 shares expired unexercised on April 13, 2021. On April 13, 2016, pursuant to the terms of the loan and security agreement with Ligand Pharmaceuticals Incorporated (“Ligand”), the Company issued to Ligand a warrant to purchase up to 960,000 shares of the Company’s common stock (the “Ligand Warrant”). beneficial ownership of the Company’s common stock to greater than 49.9%) The Ligand Warrant was issued to Ligand as a part of the repayment of $1.2 million of the Company’s obligation under the secured convertible promissory note issued to Ligand pursuant to the loan and security agreement with Ligand On June 14, 2017, the Company entered into a securities purchase agreement, with certain accredited investors (the “Purchasers”), pursuant to which the Company sold an aggregate of 3,749,783 shares (the “Shares”) of its common stock, and the warrants to purchase up to an aggregate 2,812,337 shares of its common stock to the Purchasers (the “Warrants”). The combined purchase price for one Share and one Warrant to purchase 0.75 shares of common stock was $1.15. The closing of the issuance of the Shares and the Warrants occurred on June 19, 2017. The Warrants have an exercise price of $1.30 per share, subject to adjustment as provided therein, and became exercisable beginning on December 19, 2017 through December 19, 2022. Each holder of a Warrant does not have the right to exercise any portion of its Warrant if the holder, together with its affiliates, would beneficially own in excess of 4.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise (the “Beneficial Ownership Limitation”); provided, however, that upon 61 days’ prior notice to the Company, the holder may increase the Beneficial Ownership Limitation; however, in no event shall the Beneficial Ownership Limitation exceed 9.99%. The exercise price and number of shares of common stock issuable upon the exercise of the Warrants will be subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Warrants. On January 16, 2018, the resale Registration Statement on Form S-1 (File No. 333-222202) that the Company filed related to the 1,987,337 shares subject to unexercised Warrants was declared effective by the SEC.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies On May 25, 2018, the Company entered into an office lease (the “Lease”) with Kilroy Realty, L.P. The Lease is for approximately 7,149 rentable square feet of space located at 12340 El Camino Real, Suite 250, San Diego, California 92130 (the “Premises”). The Premises will continue t The Lease commenced on November 1, 2018 and will expire on January 31, 2022, unless terminated earlier in accordance with the terms of the Lease (the “Term”). Monthly base rent payments due under the Lease for the Premises will be $27,000, subject to annual increases of 3.0% during the Term. Under the Lease, the Company is responsible for certain charges for common area maintenance and other costs, including electricity and utility expenses, and the Lease provides for abatement of rent during certain periods and escalating rent payments throughout the Term. Rent expense is being recorded on a straight-line basis over the life of the Lease and the difference between the rent expense and rent paid is being recorded as deferred rent. The Lease provides the Company with an option to extend the lease for a period of three years beyond the Term. If the option is exercised, the renewal term will be upon the same terms and conditions as the original Term, except that the base rent will be equal to the prevailing market rate as determined pursuant to the terms of the Lease. Rent expense was $81,000 for each of the three months ended June 30, 2021 and 2020. Rent expense was $162,000 and $163,000 for the six months ended June 30, 2021 and 2020, respectively. Future minimum payments pursuant to the Lease are as follows (in thousands) As of June 30, 2021: 2021 $ 173 2022 29 Total minimum lease payments $ 202

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	9. Subsequent Events The Company has evaluated all subsequent events through the date of filing of this Quarterly Report on Form 10-Q with the SEC, to ensure that this filing includes appropriate disclosure of events both recognized in the financial statements as of June 30, 2021, and events which occurred subsequent to June 30, 2021, but which were not recognized in the financial statements. The Company has determined that there were no subsequent events which required recognition, adjustment to or disclosure in the financial statements.

Organization, Liquidity and M_2

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
The Company	The Company Viking Therapeutics, Inc., a Delaware corporation (the “Company”), is a clinical-stage biopharmaceutical company focused on the development of novel therapies for metabolic and endocrine disorders. The Company was incorporated under the laws of the State of Delaware on September 24, 2012 and its principal executive offices are located in San Diego, California.
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying balance sheet as of June 30, 2021, statements of operations for the three and six months ended June 30, 2021 and 2020, statements of stockholders’ equity for the three and six months ended June 30, 2021 and 2020 and statements of cash flows for the six months ended June 30, 2021 and 2020 are unaudited. These unaudited financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. These financial statements should be read in conjunction with the audited financial statements and the accompanying notes for the year ended December 31, 2020 contained in the Annual Report on Form 10-K filed by the Company with the SEC on February 17, 2021. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of June 30, 2021, the results of operations for the three and six months ended June 30, 2021 and 2020, the statements of stockholders’ equity for the three and six months ended June 30, 2021 and 2020 and the statements of cash flows for the six months ended June 30, 2021 and 2020. The December 31, 2020 balance sheet included herein was derived from the audited financial statements, but it does not include all disclosures or notes required by GAAP for complete financial statements. The financial data and other information disclosed in these notes to the financial statements related to the three and six months ended June 30, 2021 and 2020 are unaudited. Interim results are not necessarily indicative of results for an entire year.
Risks And Uncertainties	Risks and Uncertainties The Company is subject to risks and uncertainties as a result of the COVID-19 pandemic. The extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the responses that the Company, other businesses and governments are taking continue to evolve. Furthermore, capital markets and economies worldwide have also been negatively impacted by the COVID-19 pandemic, and it is possible that it could cause a local and/or global economic slowdown or recession. Policymakers around the globe have responded with fiscal policy actions to support the healthcare industry and economy as a whole. The magnitude and overall effectiveness of these actions remain uncertain. In addition, the Company’s clinical trials have been affected by and may continue to be affected by the COVID-19 pandemic. Clinical site initiation and patient enrollment have been and may continue to be delayed due to prioritization of hospital resources toward the COVID-19 pandemic. Some patients have not been and others may not be able to comply with clinical trial protocols if quarantines impede patient movement or interrupt healthcare services. Similarly, any inability to recruit and retain patients and principal investigators and site staff who, as healthcare providers, may have heightened exposure to COVID-19, may adversely impact the Company’s clinical trial operations. The severity of the impact of the COVID-19 pandemic on the Company’s business will depend on a number of factors, including, but not limited to, the duration and severity of the pandemic and the extent and severity of the impact on the Company’s service providers, suppliers, contract research organizations (“CROs”) and the Company’s clinical trials, all of which are uncertain and cannot be predicted. As of the date of the issuance of the Company’s financial statements, the extent to which the COVID-19 pandemic may materially impact the Company’s financial condition, liquidity or results of operations is uncertain.
Reclassifications	Reclassification Certain amounts reported in prior years in the financial statements have been reclassified to conform to the current year’s presentation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying financial statements. Significant estimates made in preparing these financial statements relate to accounting for an operating lease and certain commitments. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents.
Investments Available-for-Sale	Investments Available-for-Sale Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income (loss). The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. The amortization of premiums and accretion of discounts is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income (expense). The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured depository institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Prepaid Clinical Trial and Preclinical Study Costs	Prepaid Clinical Trial and Preclinical Study Costs Prepaid clinical trial and preclinical study costs represent advance payments by the Company for future clinical trial and preclinical study services to be performed by the clinical research organization and other research organizations. Such amounts are recognized as research and development expense as the related clinical trial and preclinical study services are performed.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) assets, and lease liability obligations are included in the Company’s balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liability obligations represent its obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company uses the implicit rate when readily determinable. The ROU asset also includes any lease payments made and excludes lease incentives and lease direct costs. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Please refer to Note 4 for additional information.
Deferred Financing Costs	Deferred Financing Costs Deferred financing costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. Costs related to the public sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. Costs related to the private sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are amortized over the term of the applicable purchase agreement.
Revenue Recognition	Revenue Recognition The Company has not recorded any revenues since its inception. However, in the future, the Company may enter into collaborative research and licensing agreements, under which the Company could be eligible for payments made in the form of upfront license fees, research funding, cost reimbursement, contingent event-based payments and/or royalties. On January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers and all related amendments (“ASC 606” or “the revenue standard”). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-s
Research and Development Expenses	Research and Development Expenses All costs of research and development are expensed in the period incurred. Research and development costs primarily consist of fees paid to CROs and clinical trial sites, employee and consultant related expenses, which include salaries, benefits and stock-based compensation for research and development personnel, external research and development expenses incurred pursuant to agreements with third-party manufacturing organizations, facilities costs, travel costs, dues and subscriptions, depreciation and materials used in preclinical studies, clinical trials and research and development. The Company estimates its preclinical study and clinical trial expenses based on the services it received pursuant to contracts with research institutions and CROs that conduct and manage preclinical studies and clinical trials on the Company’s behalf. Clinical trial-related contracts vary significantly in length, and may be for a fixed amount based on milestones or deliverables, a variable amount based on actual costs incurred, capped at a certain limit, or a combination of these elements. The Company accrues service fees based on work performed, which relies on estimates of total costs incurred based on milestones achieved, patient enrollment and other events. The majority of the Company’s service providers invoice the Company in arrears, and to the extent that amounts invoiced differ from its estimates of expenses incurred, the Company accrues for additional costs. The financial terms of these agreements vary from contract to contract and may result in uneven expenses and payment flows. Preclinical study and clinical trial expenses include: • fees paid to CROs, consultants and laboratories in connection with preclinical studies; • fees paid to CROs, clinical trial sites, investigators and consultants in connection with clinical trials; and • fees paid to contract manufacturers and service providers in connection with the production, testing and packaging of active pharmaceutical ingredients and drug materials for preclinical studies and clinical trials. Payments under some of these agreements depend on factors such as the milestones accomplished, including enrollment of certain numbers of patients, site initiation and the completion of clinical trial milestones. To date, the Company has not experienced any events requiring it to make material adjustments to its accruals for service fees. If the Company does not identify costs that it has begun to incur or if it underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates, which could materially affect its results of operations. Adjustments to the Company’s accruals are recorded as changes in estimates become evident. Furthermore, based on amounts invoiced to the Company by its service providers, the Company may also record payments made to those providers as prepaid expenses that will be recognized as expense in future periods as services are rendered.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred to general and administrative expense, as recoverability of such expenditures is uncertain.
Stock-Based Compensation	Stock-Based Compensation The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model (the “Black-Scholes model”). The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of the Company’s common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the Company’s 2014 Employee Stock Purchase Plan (the “ESPP”), the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, as an employee elects to increase his or her contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods.
Income Taxes	Income Taxes The Company accounts for its income taxes using the liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the basis used for financial reporting and income tax reporting purposes. Deferred income taxes are provided based on the enacted tax rates in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more likely than not that the Company will not realize those tax assets through future operations. FASB Accounting Standards Codification Topic 740-10, Income Taxes The Company’s policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, the Company currently does not have any deemed common share equivalents; therefore, its basic and diluted net loss per share calculations are the same. The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ (15,381 ) $ (9,572 ) $ (29,391 ) $ (19,259 ) Denominator: Weighted-average common shares outstanding 78,079,689 72,670,585 76,531,208 72,605,054 Less: Weighted-average shares subject to repurchase (183,095 ) (183,095 ) (183,095 ) (183,095 ) Denominator for basic and diluted net loss per share 77,896,594 72,487,490 76,348,113 72,421,959 Net loss per share: Basic and diluted $ (0.20 ) $ (0.13 ) $ (0.38 ) $ (0.27 ) Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of June 30, 2021 2020 Common stock warrants 487,087 5,592,398 Restricted stock units 1,047,155 795,695 Common stock subject to repurchase 183,095 183,095 Common stock options 3,917,509 3,429,123 5,634,846 10,000,311
Segments	Segments The Company operates in only one segment. Management uses cash flows as the primary measure to manage its business and does not segment its business for internal reporting or decision-making purposes.

Organization, Liquidity and M_3

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Common Share	The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ (15,381 ) $ (9,572 ) $ (29,391 ) $ (19,259 ) Denominator: Weighted-average common shares outstanding 78,079,689 72,670,585 76,531,208 72,605,054 Less: Weighted-average shares subject to repurchase (183,095 ) (183,095 ) (183,095 ) (183,095 ) Denominator for basic and diluted net loss per share 77,896,594 72,487,490 76,348,113 72,421,959 Net loss per share: Basic and diluted $ (0.20 ) $ (0.13 ) $ (0.38 ) $ (0.27 )
Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share	Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of June 30, 2021 2020 Common stock warrants 487,087 5,592,398 Restricted stock units 1,047,155 795,695 Common stock subject to repurchase 183,095 183,095 Common stock options 3,917,509 3,429,123 5,634,846 10,000,311

Investments in Marketable Sec_2

Investments in Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2021
Investments Debt And Equity Securities [Abstract]
Summary of Investments Classified As Available-For-Sale Securities	Investments classified as available-for-sale as of June 30, 2021 consisted of the following (in thousands): As of June 30, 2021 Amortized Cost Gross Unrealized Gains (1) Gross Unrealized Losses (1) Aggregate Estimated Fair Value Certificates of deposit (2) $ 510 $ — $ — $ 510 Commercial paper (2) $ 48,705 $ — $ — $ 48,705 Corporate debt securities (2) $ 161,325 $ 25 $ (205 ) $ 161,145 Government debt securities (2) $ 9,077 — (8 ) 9,069 $ 219,617 $ 25 $ (213 ) $ 219,429 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At June 30, 2021, there were 28 securities in an unrealized gain position and there were 66 securities in an unrealized loss position. The unrealized gains were less than $6,000 individually and $25,000 in the aggregate. (2) At June 30, 2021, none of these securities were classified as cash and cash equivalents on the Company’s balance sheet, and $44.2 Investments classified as available-for-sale as of December 31, 2020 consisted of the following (in thousands): As of December 31, 2020 Amortized Cost Gross Unrealized Gains (1) Gross Unrealized Losses (1) Aggregate Estimated Fair Value Commercial paper (2) $ 27,973 $ — $ — $ 27,973 Corporate debt securities (2) $ 185,711 $ 94 $ (136 ) $ 185,669 Government debt securities (2) $ 5,639 $ — $ (12 ) $ 5,627 $ 219,323 $ 94 $ (148 ) $ 219,269 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At December 31, 2020, there were 38 securities in an unrealized gain position and 80 securities in an unrealized loss position The unrealized losses were less than $21,000 individually and $148,000 in the aggregate. (2) At December 31, 2020, none of these securities were classified as cash and cash equivalents on the Company’s balance sheet and $53.4 million of the corporate debt securities were scheduled to mature outside of one year.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Values of Financial Instruments	The fair values of the Company’s financial instruments are presented below (in thousands): Fair Value Measurements at June 30, 2021 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: Government money market funds $ 5,492 $ 5,492 $ — $ — Short-term investments Certificates of deposit 510 — 510 — Commercial paper, available-for-sale 48,705 — 48,705 — Corporate debt securities, available-for-sale 161,145 — 161,145 — Government debt securities, available-for-sale 9,069 — 9,069 — Total financial assets $ 224,921 $ 5,492 $ 219,429 $ — Fair Value Measurements at December 31, 2020 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: Government money market funds $ 26,868 $ 26,868 $ — $ — Short-term investments Commercial paper, available for sale 27,973 — 27,973 — Corporate debt securities, available-for-sale 185,669 — 185,669 — Government debt securities, available-for-sale 5,627 — 5,627 — Total financial assets $ 246,137 $ 26,868 $ 219,269 $ —

Operating Leases - ROU Assets_2

Operating Leases - ROU Assets and Lease Liability Obligations (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of ROU Assets and Lease Liabilities	The Company has only one operating lease, which is for office space that expires in January 2022. Below is a summary of the Company’s ROU assets and lease liabilities as of June 30, 2021 and December 31, 2020 (in thousands, except for years and %): June 30, December 31, 2021 2020 Right-of-use assets $ 176 $ 321 Lease liability obligations, current $ 198 $ 330 Lease liability obligations, less current portion $ — 29 Total lease liability obligations $ 198 $ 359 Weighted-average remaining lease term 0.58 years 1.08 years Weighted-average discount rate 6.00 % 6.00 %
Schedule of Future Minimum Lease Payments	Approximate future minimum lease payments for the Company’s ROU assets over the remaining lease period as of June 30 , 2021 are as follows (in thousands): Remainder of 2021 $ 173 2022 29 Total minimum lease payments $ 202 Less: amount representing interest $ (4 ) Total lease liability obligations $ 198

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Summary of Stock-based Compensation Expense Recognized	During the three and six months ended June 30, 2021 and 2020, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Stock-based compensation expense by type of award: Stock options $ 774 $ 859 $ 1,600 $ 1,683 Restricted stock and restricted stock units 655 733 1,342 1,497 Employee stock purchase plan 62 56 126 121 Total stock-based compensation expense included in expenses $ 1,491 $ 1,648 $ 3,068 $ 3,301 Stock-based compensation expense by line item: Research and development expenses $ 347 $ 404 $ 782 $ 724 General and administrative expenses 1,144 1,244 2,286 2,577 Total stock-based compensation expense included in expenses $ 1,491 $ 1,648 $ 3,068 $ 3,301
Schedule of Unrecognized Stock-based Compensation Expense, Net of Estimated Forfeitures, by Type of Award and Weighted-average Recognition Period	The following table sets forth the Company’s unrecognized stock-based compensation expense, net of estimated forfeitures, by type of award and the weighted-average period over which that expense is expected to be recognized (in thousands, except for years): As of June 30, 2021 Unrecognized Expense, Net of Estimated Forfeitures Weighted- average Recognition Period (in years) Type of award: Stock options $ 6,091 2.46 Restricted stock and restricted stock units $ 4,844 1.67
Summary of Stock Option Activity	The following table summarizes stock option activity during the six months ended June 30, 2021: Shares Subject to Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Options outstanding at December 31, 2020 3,371,323 $ 5.57 Granted 827,020 $ 5.80 Exercised (104,453 ) $ 3.30 375,000 Cancelled (176,381 ) $ 6.96 Options outstanding at June 30, 2021 3,917,509 $ 5.62 7.61 4,966,000 Options exercisable at June 30, 2021 2,226,229 $ 4.92 6.50 4,626,000
Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model	the fair value of each employee option grant during the six months ended June 30, 2021 was estimated on the date of grant using the Black-Scholes model with the following weighted average assumptions: Six Months Ended June 30, 2021 Expected volatility 83.92 % Expected term (in years) 6.09 Risk-free interest rate 0.52 % Expected dividend yield 0 %
Restricted stock [Member]
Summary of Shares Granted and Stock Activity	The following table is a summary of restricted stock activity during the six months ended June 30, 2021: Shares of Restricted Stock Weighted- Average Grant Date Fair Value Unvested at December 31, 2020 183,095 $ 0.17 Granted — $ — Vested — $ — Forfeited — $ — Unvested at June 30, 2021 183,095 $ 0.17
Restricted stock units [Member]
Summary of Shares Granted and Stock Activity	The following table summarizes restricted stock unit activity during the six months ended June 30, 2021: Shares Subject to Restricted Stock Units Weighted- Average Grant Date Value Unvested at December 31, 2020 679,363 $ 7.65 Granted 588,820 $ 5.80 Vested (192,229 ) $ 7.34 Forfeited (28,799 ) $ 6.07 Unvested at June 30, 2021 1,047,155 $ 6.71

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Minimum Payments for Lease	Future minimum payments pursuant to the Lease are as follows (in thousands) As of June 30, 2021: 2021 $ 173 2022 29 Total minimum lease payments $ 202

Organization, Liquidity and M_4

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2021Segment
Accounting Policies [Abstract]
Date of incorporation	Sep. 24, 2012
State code of incorporation	DE
Highly liquid investments maturities	Three months or less
Number of operating segment	1

Organization, Liquidity and M_5

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies - Schedule of Computation of Basic and Diluted Net Loss per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss attributable to common stockholders	$ (15,381)	$ (9,572)	$ (29,391)	$ (19,259)
Denominator:
Weighted-average common shares outstanding	78,079,689	72,670,585	76,531,208	72,605,054
Less: Weighted-average shares subject to repurchase	(183,095)	(183,095)	(183,095)	(183,095)
Denominator for basic and diluted net loss per share	77,896,594	72,487,490	76,348,113	72,421,959
Net loss per share:
Basic and diluted	$ (0.20)	$ (0.13)	$ (0.38)	$ (0.27)

Organization, Liquidity and M_6

Organization, Liquidity and Management's Plan, and Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	5,634,846	10,000,311
Common stock warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	487,087	5,592,398
Restricted stock units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	1,047,155	795,695
Common stock subject to repurchase [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	183,095	183,095
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	3,917,509	3,429,123

Investments in Marketable Sec_3

Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Available For Sale Securities [Abstract]
Proceeds from sales of available-for-sale securities	$ 0	$ 0	$ 0

Investments in Marketable Sec_4

Investments in Marketable Securities - Summary of Investments Classified As Available-For-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 219,617	$ 219,323
Gross Unrealized Gains	25	94
Gross Unrealized Losses	(213)	(148)
Aggregate Estimated Fair Value	219,429	219,269
Certificate of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	510
Aggregate Estimated Fair Value	510
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,705	27,973
Aggregate Estimated Fair Value	48,705	27,973
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	161,325	185,711
Gross Unrealized Gains	25	94
Gross Unrealized Losses	(205)	(136)
Aggregate Estimated Fair Value	161,145	185,669
Government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,077	5,639
Gross Unrealized Losses	(8)	(12)
Aggregate Estimated Fair Value	$ 9,069	$ 5,627

Investments in Marketable Sec_5

Investments in Marketable Securities - Summary of Investments Classified As Available-For-Sale Securities (Parenthetical) (Detail)	Jun. 30, 2021USD ($)Security	Dec. 31, 2020USD ($)Security
Schedule of Available-for-sale Securities [Line Items]
Number of securities in unrealized gain position | Security	28	38
Unrealized gains, aggregate	$ 25,000	$ 94,000
Number of securities in unrealized loss position | Security	66	80
Unrealized losses, aggregate	$ 213,000	$ 148,000
Short-term investments - available for sale	219,429,000	219,269,000
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	48,705,000	27,973,000
Short-term investments classified as available-for-sale, noncurrent	44,200,000	53,400,000
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains, aggregate	25,000	94,000
Unrealized losses, aggregate	205,000	136,000
Short-term investments - available for sale	161,145,000	185,669,000
Short-term investments classified as available-for-sale, noncurrent	44,200,000	53,400,000
Government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses, aggregate	8,000	12,000
Short-term investments - available for sale	9,069,000	5,627,000
Short-term investments classified as available-for-sale, noncurrent	44,200,000	53,400,000
Certificate of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	510,000
Short-term investments classified as available-for-sale, noncurrent	44,200,000
Cash equivalents [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	0	0
Cash equivalents [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	0	0
Cash equivalents [Member] | Government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	0	0
Cash equivalents [Member] | Certificate of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments - available for sale	0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains, individually	6,000	21,000
Unrealized gains, aggregate	25,000	148,000
Unrealized losses, individually	45,000	35,000
Unrealized losses, aggregate	$ 213,000	$ 94,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financial assets carried at fair value:
Total financial assets	$ 224,921	$ 246,137
Level 1 [Member]
Financial assets carried at fair value:
Total financial assets	5,492	26,868
Level 2 [Member]
Financial assets carried at fair value:
Total financial assets	219,429	219,269
Government money market funds [Member]
Financial assets carried at fair value:
Cash equivalents, fair value disclosure	5,492	26,868
Government money market funds [Member] | Level 1 [Member]
Financial assets carried at fair value:
Cash equivalents, fair value disclosure	5,492	26,868
Certificate of deposit [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	510
Certificate of deposit [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	510
Commercial paper [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	48,705	27,973
Commercial paper [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	48,705	27,973
Corporate debt securities, available-for-sale [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	161,145	185,669
Corporate debt securities, available-for-sale [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	161,145	185,669
Government debt securities, available-for-sale [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	9,069	5,627
Government debt securities, available-for-sale [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	$ 9,069	$ 5,627

Operating Leases - ROU Assets_3

Operating Leases - ROU Assets and Lease Liability Obligations - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)Lease	Jun. 30, 2020USD ($)
Leases [Abstract]
Operating lease number of leases | Lease			1
Lease expiration date			2022-01
Operating lease expense | $	$ 77,000	$ 77,000	$ 154,000	$ 154,000
Operating lease, option to extend, description			The operating lease provides the Company with an option to extend the term of the lease for a period of three years beyond the expiration date of January 2022.

Operating Leases - ROU Assets_4

Operating Leases - ROU Assets and Lease Liability Obligations - Schedule of Right-of-use Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Lessee Disclosure [Abstract]
Right-of-use assets	$ 176	$ 321
Lease liability, current	198	330
Lease liability, net of current portion		29
Total lease liability obligations	$ 198	$ 359
Weighted-average remaining lease term	6 months 29 days	1 year 29 days
Weighted-average discount rate	6.00%	6.00%

Operating Leases - ROU Assets_5

Operating Leases - ROU Assets and Lease Liability Obligations - Schedule of Future Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Remainder of 2021	$ 173
2022	29
Total minimum lease payments	202
Less: amount representing interest	(4)
Total lease liability obligations	$ 198	$ 359

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)	Mar. 17, 2020USD ($)	Aug. 01, 2019USD ($)	Sep. 29, 2017USD ($)$ / sharesshares	Sep. 28, 2017USD ($)shares	Apr. 13, 2016$ / sharesshares	May 31, 2015USD ($)$ / sharesshares	Feb. 28, 2014Tranche$ / sharesshares	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2020USD ($)shares	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020$ / sharesshares	Dec. 31, 2019shares	Dec. 31, 2018shares	Dec. 31, 2016USD ($)	Feb. 20, 2014USD ($)
Equity [Line Items]
Preferred stock, shares authorized								10,000,000		10,000,000		10,000,000
Preferred stock, par value | $ / shares								$ 0.00001		$ 0.00001		$ 0.00001
Preferred stock, shares outstanding								0		0		0
Common stock, shares authorized								300,000,000		300,000,000		300,000,000
Common stock, par value | $ / shares								$ 0.00001		$ 0.00001		$ 0.00001
Number of common stock for issuance in exchange for future services from founders							1,000,000
Common stock price per share | $ / shares							$ 0.01
Number of tranches | Tranche							2
Unrecognized compensation expense | $						$ 62,000										$ 168,000
Common stock shares repurchased						633,810
Repurchase of common stock from stockholders, per share | $ / shares						$ 0.00001
Remaining number of repurchased shares						366,190
Common stock sold					7,500,000			0		0		0	0	0
Common stock, price per share | $ / shares					$ 1.25
Shelf registration statement expiry date		Jul. 19, 2021
Repurchase Program [Member]
Equity [Line Items]
Purchase of common stock and warrants | $	$ 50,000,000								$ 0
Shares issued under ESPP								29,896	20,809
Common stock [Member] | ATM Offering [Member]
Equity [Line Items]
Common stock sold										0
Common stock [Member] | Maximum [Member] | ATM Offering [Member]
Equity [Line Items]
Aggregate offering price, common stock | $		$ 75,000,000
LPC [Member] | Common stock [Member]
Equity [Line Items]
Common stock sold			701,282
Common stock sold aggregate purchase price | $			$ 1,300,000
Common stock, price per share | $ / shares			$ 1.78
Registration statement commencement date			Jun. 20, 2016
LPC [Member] | Common stock [Member] | Commitment Purchase Agreement [Member] | Registration Rights Agreement [Member]
Equity [Line Items]
Common stock sold				343,051
Common stock purchase agreement term				30 months
Common stock issued as consideration for commitment				100,000
Gross proceeds from common stock issuance | $				$ 802,000
LPC [Member] | Common stock [Member] | Maximum [Member] | Commitment Purchase Agreement [Member] | Registration Rights Agreement [Member]
Equity [Line Items]
Total of purchase agreement and potential aggregate future purchases | $				$ 15,000,000
Common stock to be sold, subject to certain limitations				75,000
Total purchase proceeds per purchase date, subject to certain limitations | $				$ 1,000,000
LPC [Member] | Common stock [Member] | Minimum [Member] | Commitment Purchase Agreement [Member] | Registration Rights Agreement [Member]
Equity [Line Items]
Percentage of shares may not sell if it is beneficial owning				4.99%
Tranche One [Member]
Equity [Line Items]
Number of common stock for issuance in exchange for future services from founders							500,000
Remaining number of repurchased shares						183,095
Stock compensation expense | $								$ 0	$ 0	$ 0	$ 0				$ 31,000
Tranche Two [Member]
Equity [Line Items]
Number of common stock for issuance in exchange for future services from founders							500,000
Remaining number of repurchased shares						183,095

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2021Milestoneshares	Jan. 31, 2020Milestoneshares	Jan. 31, 2019Milestoneshares	Jun. 30, 2021USD ($)Milestoneshares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)PeriodMilestone$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)shares	Jan. 01, 2021shares	Apr. 28, 2015shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeited awards						176,381
Stock-based compensation | $				$ 1,491,000	$ 1,648,000	$ 3,068,000	$ 3,301,000
Cash proceeds from exercises of stock options | $						$ 345,000	$ 108,000
Weighted average fair value of stock options granted to employees | $ / shares						$ 4.09
Excess tax benefit from stock-based awards | $						$ 0
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of performance based award	205,500	244,000	221,600
Percentage of shares vested upon achievement of certain milestone		100.00%	100.00%
Number of milestones to be achieve | Milestone		3	3
Number of milestones achieved | Milestone				1		1
Milestone achievement period	4 years	4 years	4 years
Forfeited awards				40,000		40,000
Forfeiture of performance based award				10,500		10,500
Performance Based Restricted Stock Units [Member] | PRSU Awards Vesting Upon the Achievement of Three of the Milestones Over a Four Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vested upon achievement of certain milestone	100.00%
Number of milestones to be achieve | Milestone	3
Performance Based Restricted Stock Units [Member] | PRSU Awards Vesting Upon the Achievement of Four of the Milestones Over a Four Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vested upon achievement of certain milestone	133.30%
Number of milestones to be achieve | Milestone	4
Performance Based Restricted Stock Units [Member] | January 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones deemed as achievable | Milestone				2		2
Stock-based compensation | $				$ 1,000		$ 11,000		$ 1,100,000
Performance Based Restricted Stock Units [Member] | January 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones deemed as achievable | Milestone				2		2
Stock-based compensation | $				$ 151,000		$ 301,000		$ 1,200,000
Performance Based Restricted Stock Units [Member] | January 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones deemed as achievable | Milestone				3		3
Stock-based compensation | $				$ 139,000		$ 282,000
Forfeiture of performance based award				7,500		7,500
Number of milestones met | Milestone				0		0
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance, description						Initially, a total of 1,527,770 shares of the Company’s common stock were reserved for issuance pursuant to the 2014 Plan. The number of shares available for issuance under the 2014 Plan will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 3.5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year.
Percentage of common stock outstanding to increase shares reserved for issuance						3.50%
Common stock reserved for future issuance								4,081,253		1,527,770
Additional number of shares of common stock reserved for issuance									2,562,557
Number of common shares available for grant				5,514,166		5,514,166
2014 ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance, description						The number of shares available for issuance under the ESPP will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year.
Percentage of common stock outstanding to increase shares reserved for issuance						1.00%
Common stock reserved for future issuance								2,289,561		458,331
Additional number of shares of common stock reserved for issuance									732,159
Number of common shares available for grant				2,991,824		2,991,824
Duration of employee stock purchase plan as determined by the compensation committee						24 months
Duration for offering period, employee stock purchase plan						6 months
Employee stock purchase plan, number of purchase periods | Period						4
Maximum duration for purchase under employee stock purchase plan						1 year
Maximum duration of employee stock purchase plan						27 months
Percentage of purchase of common stock						85.00%
Percentage of common stock on the date of purchase						85.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	$ 1,491	$ 1,648	$ 3,068	$ 3,301
Research and development expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	347	404	782	724
General and administrative expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	1,144	1,244	2,286	2,577
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	774	859	1,600	1,683
Restricted stock and restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	655	733	1,342	1,497
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	$ 62	$ 56	$ 126	$ 121

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Unrecognized Stock-based Compensation Expense, Net of Estimated Forfeitures, by Type of Award and Weighted-average Recognition Period (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2021	May 31, 2015	Feb. 20, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures		$ 62,000	$ 168,000
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures	$ 6,091,000
Weighted-average Recognition Period	2 years 5 months 15 days
Restricted stock and restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures	$ 4,844,000
Weighted-average Recognition Period	1 year 8 months 1 day

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted stock [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Unvested, Beginning balance | shares	183,095
Shares, Granted | shares	0
Shares, Vested | shares	0
Shares, Forfeited | shares	0
Shares, Unvested, Ending balance | shares	183,095
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 0.17
Weighted-Average Grant Date Fair Value, Granted | $ / shares	0
Weighted-Average Grant Date Fair Value, Vested | $ / shares	0
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	0
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 0.17

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted stock units [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Unvested, Beginning balance | shares	679,363
Shares, Granted | shares	588,820
Shares, Vested | shares	(192,229)
Shares, Forfeited | shares	(28,799)
Shares, Unvested, Ending balance | shares	1,047,155
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 7.65
Weighted-Average Grant Date Fair Value, Granted | $ / shares	5.80
Weighted-Average Grant Date Fair Value, Vested | $ / shares	7.34
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	6.07
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 6.71

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding beginning balance, Shares Subject to Stock Options	3,371,323
Granted, Shares Subject to Stock Options	827,020
Exercised, Shares Subject to Stock Options	(104,453)
Cancelled, Shares Subject to Stock Options	(176,381)
Options outstanding ending balance, Shares Subject to Stock Options	3,917,509
Options exercisable, Shares Subject to Stock Options	2,226,229
Options outstanding beginning balance, Weighted-Average Exercise Price	$ 5.57
Granted, Weighted-Average Exercise Price	5.80
Exercised, Weighted-Average Exercise Price	3.30
Cancelled, Weighted-Average Exercise Price	6.96
Options outstanding ending balance, Weighted-Average Exercise Price	5.62
Options exercisable, Weighted-Average Exercise Price	$ 4.92
Options outstanding, Weighted-Average Remaining Contractual Term	7 years 7 months 9 days
Options exercisable, Weighted-Average Remaining Contractual Term	6 years 6 months
Exercised, Aggregate Intrinsic Value	$ 375,000
Options outstanding, Aggregate Intrinsic Value	4,966,000
Options exercisable, Aggregate Intrinsic Value	$ 4,626,000

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model (Detail)	6 Months Ended
	Jun. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Expected volatility	83.92%
Expected term (in years)	6 years 1 month 2 days
Risk-free interest rate	0.52%
Expected dividend yield	0.00%

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jun. 14, 2017	Apr. 13, 2016	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 13, 2021	Jan. 16, 2018
Class of Warrant or Right [Line Items]
Issuance of shares of common stock		7,500,000	0	0	0	0	0
Warrants sold		7,500,000
Common stock, price per share		$ 1.25
Exercise price of warrant		1.50
Warrants expiry date				Apr. 13, 2021
Public offering price per warrant		$ 0.01
Warrants exercised			922,087	3,618,312
Class of warrants or rights expired								29,101
Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Warrants sold			487,087	487,087
Warrants exercised			0	150,000
Public offering price per share and per warrant	$ 1.15
Unexercised warrants									1,987,337
Loan and Security Agreement [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Beneficial ownership of company's common stock		49.90%
Ligand [Member] | Loan and Security Agreement [Member]
Class of Warrant or Right [Line Items]
Warrants sold		960,000
Exercise price of warrant		$ 1.50
Warrants expiry date				Apr. 13, 2021
Repayments of notes payable in stock		$ 1.2
Over-Allotment Option [Member]
Class of Warrant or Right [Line Items]
Warrants sold		1,125,000
Private Placement and Registered Direct Offering [Member] | Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Exercise price of warrant	$ 1.30
Warrants expiry date				Dec. 19, 2022
Number of warrants issued for common stock	0.75
Warrants exercisable date				Dec. 19, 2017
Percentage of warrant exercise beneficial ownership limitation of common stock outstanding minimum	4.99%
Prior notice period of increase beneficial ownership limitation	61 days
Percentage of minimum beneficial ownership limitation	9.99%
Description of beneficial ownership limitation				Each holder of a Warrant does not have the right to exercise any portion of its Warrant if the holder, together with its affiliates, would beneficially own in excess of 4.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise (the “Beneficial Ownership Limitation”); provided, however, that upon 61 days’ prior notice to the Company, the holder may increase the Beneficial Ownership Limitation; however, in no event shall the Beneficial Ownership Limitation exceed 9.99%.
Private Placement and Registered Direct Offering [Member] | Common stock [Member] | Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Issuance of shares of common stock	3,749,783
Private Placement and Registered Direct Offering [Member] | Maximum [Member] | Common stock [Member] | Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Warrants sold	2,812,337

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	May 25, 2018USD ($)ft²	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)
Commitments And Contingencies [Line Items]
Operating lease option to extend term				3 years
Rent expense		$ 81,000	$ 81,000	$ 162,000	$ 163,000
California [Member] | Office Lease [Member]
Commitments And Contingencies [Line Items]
Area of lease premises | ft²	7,149
Lease commencement date	Nov. 1, 2018
Lease expiration date	Jan. 31, 2022
Monthly base rent payments	$ 27,000
Percentage of rent increase under lease	3.00%

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Future Minimum Payments for Lease (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2021	$ 173
2022	29
Total minimum lease payments	$ 202