Corvus Pharmaceuticals (CRVS) 10-K 28 Mar 23 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 28, 2023	Jun. 30, 2022
Document And Entity Information
Document Annual Report	true
Document Transition Report	false
Document Type	10-K
Document Period End Date	Dec. 31, 2022
Entity Registrant Name	Corvus Pharmaceuticals, Inc.
Entity Tax Identification Number	46-4670809
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity File Number	001-37719
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	863 Mitten Road, Suite 102
Entity Address, City or Town	Burlingame
Entity Address, Postal Zip Code	94010
Entity Address, State or Province	CA
City Area Code	650
Local Phone Number	900-4520
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 34.2
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Trading Symbol	CRVS
Entity Common Stock, Shares Outstanding		46,568,511
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	238
Auditor Location	San Jose, California
Entity Central Index Key	0001626971
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
ICFR Auditor Attestation Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 13,159	$ 63,458
Marketable securities	29,144	5,993
Accounts receivable - related party	588	507
Prepaid and other current assets	773	1,354
Total current assets	43,664	71,312
Property and equipment, net	353	451
Operating lease right-of-use asset	2,217	3,190
Investment in Angel Pharmaceuticals	21,877	34,266
Other assets	129	236
Total assets	68,240	109,455
Current liabilities:
Accounts payable	1,976	1,565
Operating lease liability	1,228	1,046
Accrued and other liabilities	7,548	7,081
Total current liabilities	10,752	9,692
Operating lease liability	1,373	2,601
Total liabilities	12,125	12,293
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred stock: $0.0001 par value; 10,000,000 shares authorized at December 31, 2022 and December 31, 2021; 0 shares issued and outstanding at December 31, 2022 and December 31, 2021
Common stock: $0.0001 par value; 290,000,000 shares authorized at December 31, 2022 and December 31, 2021; 46,553,511 shares issued and outstanding at December 31, 2022 and December 31, 2021	5	5
Additional paid-in capital	364,361	361,669
Accumulated other comprehensive (loss) income	(563)	1,869
Accumulated deficit	(307,688)	(266,381)
Total stockholders' equity	56,115	97,162
Total liabilities and stockholders' equity	$ 68,240	$ 109,455

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
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 (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	290,000,000	290,000,000
Common stock, shares issued	46,553,511
Common stock, shares outstanding	46,553,511

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating expenses:
Research and development	$ 24,468	$ 29,115	$ 31,830
General and administrative	8,097	9,515	11,930
Total operating expenses	32,565	38,630	43,760
Loss from operations	(32,565)	(38,630)	(43,760)
Interest income and other expense, net	654	(15)	540
Gain on sale of property and equipment	22
Gain on deconsolidation of Angel Pharmaceuticals			37,459
Sublease income - related party	587	235
Loss from equity method investment	(10,005)	(4,831)	(234)
Net loss	$ (41,307)	$ (43,241)	$ (5,995)
Net loss per share, basic	$ (0.89)	$ (1.03)	$ (0.20)
Net loss per share, diluted	$ (0.89)	$ (1.03)	$ (0.20)
Shares used to compute net loss per share, basic	46,553,511	41,854,110	29,478,878
Shares used to compute net loss per share, diluted	46,553,511	41,854,110	29,478,878
Other comprehensive loss:
Unrealized gain (loss) on marketable securities	$ (48)	$ (7)	$ (25)
Cumulative foreign currency translation adjustment	(2,384)	1,872
Comprehensive loss	$ (43,739)	$ (41,376)	$ (6,020)

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock.	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balance at Dec. 31, 2019	$ 3	$ 288,224	$ 29	$ (217,145)	$ 71,111
Balance (in shares) at Dec. 31, 2019	27,953,233
Issuance of common stock in connection with at-the-market offering, net		1,222			1,222
Issuance of common stock in connection with at-the-market offering, net (Shares)	(310,734)
Common stock issued on exercise of stock options		88			88
Common stock issued on exercise of stock options (in shares)	108,667
Stock-based compensation expense		5,747			5,747
Unrealized gain (loss) on marketable securities			(25)		(25)
Net loss				(5,995)	(5,995)
Balance at Dec. 31, 2020	$ 3	295,281	4	(223,140)	72,148
Balance (in shares) at Dec. 31, 2020	28,372,634
Issuance of common stock in connection with at-the-market offering, net	$ 1	28,953			28,954
Issuance of common stock in connection with at-the-market offering, net (Shares)	6,609,605
Common stock issued on exercise of stock options		1,215			1,215
Common stock issued on exercise of stock options (in shares)	329,665
Issuance of common stock upon exercise of Exchange Warrants (Shares)	1,457,947
Issuance of common stock upon follow-on public offering, net	$ 1	31,988			31,989
Issuance of common stock upon follow-on public offering, net (Shares)	9,783,660
Stock-based compensation expense		4,232			4,232
Unrealized gain (loss) on marketable securities			(7)		(7)
Foreign currency translation adjustment			1,872		1,872
Net loss				(43,241)	(43,241)
Balance at Dec. 31, 2021	$ 5	361,669	1,869	(266,381)	97,162
Balance (in shares) at Dec. 31, 2021	46,553,511
Stock-based compensation expense		2,692			2,692
Unrealized gain (loss) on marketable securities			(48)		(48)
Foreign currency translation adjustment			(2,384)		(2,384)
Net loss				(41,307)	(41,307)
Balance at Dec. 31, 2022	$ 5	$ 364,361	$ (563)	$ (307,688)	$ 56,115
Balance (in shares) at Dec. 31, 2022	46,553,511

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (41,307)	$ (43,241)	$ (5,995)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	367	460	632
Accretion related to marketable securities	(170)	239	154
Stock-based compensation	2,692	4,232	5,747
Gain from sale of property and equipment	(22)
Gain on deconsolidation of Angel Pharmaceuticals			(37,459)
Loss from equity method investment	10,005	4,831	234
Changes in operating assets and liabilities:
Accounts receivable - related party	(81)	(507)
Prepaid and other current assets	581	(277)	285
Operating lease right-of-use asset	973	(1,542)	679
Other assets	107	178	99
Accounts payable	411	(1,902)	1,019
Accrued and other liabilities	467	(523)	705
Operating lease liability	(1,046)	1,337	(878)
Net cash used in operating activities	(27,023)	(36,715)	(34,778)
Cash flows from investing activities
Purchases of marketable securities	(66,191)	(9,357)	(42,540)
Sales of marketable securities			1,009
Maturities of marketable securities	43,162	30,922	86,376
Purchases of property and equipment	(269)	(5)	(76)
Proceeds from sale of property and equipment	22
Net cash provided by (used in) investing activities	(23,276)	21,560	44,769
Cash flows from financing activities
Proceeds from issuance of common stock, net (includes $4,850 in aggregate gross proceeds from related parties for the year ended December 31, 2021)		31,989
Proceeds from issuance of common stock in connection with at-the-market offering, net		28,954	1,222
Proceeds from exercise of common stock options		1,215	88
Net cash provided by financing activities		62,158	1,310
Net increase (decrease) in cash and cash equivalents	(50,299)	47,003	11,301
Cash and cash equivalents at beginning of the period	63,458	16,455	5,154
Cash and cash equivalents at end of the period	$ 13,159	63,458	$ 16,455
Supplemental disclosures of cash flow information
Purchases of property and equipment incurred but not paid		$ 5

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
CONSOLIDATED STATEMENTS OF CASH FLOWS
Proceeds from issuance of common stock, net, from related parties	$ 4,850

Organization

Organization	12 Months Ended
	Dec. 31, 2022
Organization
Organization	1. Organization Corvus Pharmaceuticals, Inc. (“Corvus” or the “Company”) was incorporated in Delaware on January 27, 2014 and commenced operations in November 2014. Corvus is a clinical-stage biopharmaceutical company. The Company’s operations are located in Burlingame, California. Presentation Initial Public Offering On March 22, 2016, the Company’s registration statement on Form S-1 (File No. 333-208850) relating to its initial public offering (“IPO”) of its common stock was declared effective by the Securities and Exchange Commission (“SEC”) and the shares of its common stock began trading on the Nasdaq Global Market on March 23, 2016. The public offering price of the shares sold in the IPO was $15.00 per share. The IPO closed on March 29, 2016, pursuant to which the Company sold 4,700,000 shares of its common stock. On April 26, 2016, the Company sold an additional 502,618 shares of its common stock to the underwriters upon partial exercise of their over-allotment option, at the initial offering price of $15.00 per share. The Company received aggregate net proceeds of approximately $70.6 million, after underwriting discounts, commissions and offering expenses. Immediately prior to the consummation of the IPO, all outstanding shares of convertible preferred stock were converted into common stock. Follow-on Public Offering In March 2018, the Company completed a follow-on public offering in which the Company sold 8,117,647 shares of common stock at a price of $8.50 per share, which included 1,058,823 shares issued pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock. The aggregate net proceeds received by the Company from the offering were approximately $64.9 million, net of underwriting discounts and commissions and offering expenses payable by the Company. ​ In February 2021, the Company completed a follow-on public offering in which the Company sold 9,783,660 shares of common stock at a price of $3.50 per share, which included 1,212,231 shares issued pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock. The aggregate net proceeds received by the Company from the offering were approximately $32.0 million, net of underwriting discounts and commissions and offering expenses. ​ Liquidity supply, sales and marketing and general operations. In addition, other unanticipated costs may arise. Because the outcome of any clinical trial and/or regulatory approval process is highly uncertain, the Company may not be able to accurately estimate the actual amounts necessary to successfully complete the development, regulatory approval process and commercialization of CPI-818, ciforadenant and mupadolimab, or any other product candidates. The Company does not expect its existing capital resources to be sufficient to enable it to fund the completion of its clinical trials and remaining development program of CPI-818, ciforadenant and mupadolimab through commercialization. In addition, its operating plan may change as a result of many factors. Exchange Warrants ​ On November 8, 2019, the Company entered into an exchange agreement (the “Exchange Agreement”) with an investor and its affiliates (the “Exchanging Stockholders”), pursuant to which the Company exchanged an aggregate of 1,458,000 shares of the Company’s common stock, par value $0.0001 per share, owned by the Exchanging Stockholders for pre-funded warrants (the “Exchange Warrants”) to purchase an aggregate of 1,458,000 shares of common stock (subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Exchange Warrants), with an exercise price of $0.0001 per share. The Exchange Warrants were exercisable at any time prior to expiration except that the Exchange Warrants could not be exercised by the Exchanging Stockholders if, after giving effect thereto, the Exchanging Stockholders would have beneficially owned more than 9.99% of the Company’s common stock, subject to certain exceptions. In accordance with Accounting Standards Codification Topic 505, Equity, and Accounting Research Bulletin 43, the Company recorded the retirement of the common stock exchanged as a reduction of common shares outstanding and elected to record the excess over par value as a debit to additional paid-in-capital at the fair value of the Exchange Warrants on the issuance date. The Exchange Warrants were classified as equity in accordance with Accounting Standards Codification Topic 480, Distinguishing Liabilities from Equity, and Accounting Standards Codification Topic 815, Derivatives and Hedging, and the fair value of the Exchange Warrants was recorded as a credit to additional paid-in capital and is not subject to remeasurement. The Company determined that the fair value of the Exchange Warrants was substantially similar to the fair value of the retired shares on the issuance date due to the negligible exercise price for the Exchange Warrants. In September 2021, the Exchange Warrants were fully exercised, resulting in the issuance of 1,457,947 shares of common stock on a net exercise basis.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Company’s functional and reporting currency is the U.S. dollar, except for its investment in its equity method investee which is the Chinese renminbi (RMB). The accompanying consolidated financial statements have been prepared on a going-concern basis, which contemplates the realization of assets and discharge of liabilities in the normal course of business. Since its inception, the Company has incurred significant losses and negative cash flows from operations. As of December 31, 2022, the Company had an accumulated deficit of $307.7 million and cash, cash equivalents and marketable securities of $42.3 million. The Company has financed its operations primarily with the proceeds from the sale of stock. The Company will need to raise additional capital to meet its business objectives. The Company believes that its current cash, cash equivalents and marketable securities will be sufficient to fund its planned expenditures and meet its obligations through at least the next twelve months from the issuance of these financial statements. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from such estimates. Concentrations of Credit Risk and Other Risks and Uncertainties Substantially all of the Company’s cash and cash equivalents are deposited in accounts with two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company maintains its cash with an accredited financial institution and accordingly, such funds are subject to minimal credit risk. The Company’s marketable securities consist of investments in U.S. Treasury securities and U.S. government agency securities, which can be subject to certain credit risks. However, the Company mitigates the risks by investing in high-grade instruments, limiting its exposure to any one issuer, and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any losses on its deposits of cash, cash equivalents or marketable securities. The Company is subject to a number of risks similar to other early stage biopharmaceutical companies, including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, its reliance on third parties to conduct its clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s product candidates, its right to develop and commercialize its product candidates pursuant to the terms and conditions of the licenses granted to the Company, and protection of proprietary technology. If the Company does not successfully commercialize or partner any of its product candidates, it will be unable to generate product revenue or achieve profitability. Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment, that of the development of and commercialization of drugs and antibodies that target critical elements of the immune system. Cash, Cash Equivalents and Marketable Securities The Company considers all highly liquid investment securities with remaining maturities at the date of purchase of three months or less to be cash equivalents. Investments with remaining maturities, at the date of purchase, greater than three months are classified as “available-for-sale” and are carried at fair value with unrealized gains and losses, if any, included as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Interest and realized gains and losses are included in interest income. Realized gains and losses are recognized based on the specific identification model. Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, accounts payable and accrued liabilities, approximate fair value due to their short-term maturities. Investments in Equity Securities For equity method investees with a functional currency different than the Company’s reporting currency, the Company follows the guidance under ASC 830-10-15-5, pursuant to which, the foreign currency financial statements of a foreign investee accounted for by the equity method should be translated to the reporting entity's reporting currency. Property and Equipment, Net Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets: ​ ​ ​ ​ Laboratory equipment 5 years Computer equipment and purchased software ​ 3 years Leasehold improvements ​ Shorter of asset's useful life or remaining term of lease ​ Maintenance and repairs that do not extend the life or improve the asset are expensed when incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation or amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations. Impairment of Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the asset or asset group. Should impairment exist, the impairment loss to be recognized is measured by the amount by which the carrying amount of the asset exceeds the projected discounted future net cash flows arising from the asset. All long-lived assets are maintained in the United States of America. Clinical Trial Accruals Costs for preclinical studies and clinical trial activities are recognized based on an evaluation of the vendors’ progress towards completion of specific tasks. The Company applies significant judgment in developing estimates for clinical trial accruals based on assumptions related to vendors’ progress towards completion. In developing these estimates, management estimates vendors’ progress towards completion using data such as clinical site activations, patient enrollment or information provided to the Company by its vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. The Company determines accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion, or the services completed. The Company’s estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time. Stock-Based Compensation The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non-employee service providers. The Company accounts for stock-based employee compensation arrangements in accordance with the provisions of ASC 718, “Compensation—Stock Compensation.” For stock options granted to employees, the Company recognizes compensation expense for all stock-based awards based on the grant-date estimated fair values. The value of the award is recognized as an expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. Forfeitures are accounted for when they occur. Stock-based compensation expense related to stock options granted to non-employees is recognized based on the fair value of the stock options, determined using the Black-Scholes option pricing model. The awards generally vest over the time period the Company expects to receive service from the non-employee. Income Taxes The Company accounts for income taxes under the asset and liability method. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differences in accounting for reporting purposes and tax purposes for certain items, such as accruals and allowances not currently deductible for tax purposes. These temporary differences result in deferred tax assets and liabilities, which are included in the Company’s balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the Company’s statements of operations and comprehensive loss become deductible expenses, under applicable income tax laws or when net operating loss or credit carryforwards are utilized. Accordingly, realization of the Company’s deferred tax assets is dependent on future taxable income against which these deductions, losses and credits can be utilized. The Company must assess the likelihood that the Company’s deferred tax assets will be recovered from future taxable income and a valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Based on the available evidence, the Company is unable, at this time, to support the determination that it is more likely than not that its deferred tax assets will be utilized in the future. Accordingly, the Company recorded a full valuation allowance for all periods presented. The Company intends to maintain a valuation allowance until sufficient evidence exists to support its reversal. The Company recognizes benefits of uncertain tax positions if it is more likely than not such positions will be sustained upon examination based solely on their technical merits as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. The Company is required to file income tax returns in the U.S. federal jurisdiction. The Company currently is not under examination by the Internal Revenue Service or other jurisdictions for any tax years. Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s elements of other comprehensive loss in any period presented were unrealized gains and losses on available-for-sale marketable securities and cumulative foreign currency translation adjustments. Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of common shares outstanding and Exchange Warrants outstanding during the period, without consideration of potentially dilutive securities. In accordance with Accounting Standards Codification Topic 260, Earnings Per Share Recent Accounting Pronouncements

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2022
Net Loss per Share
Net Loss per Share	3. Net Loss per Share The following table shows the calculation of net loss per share (in thousands, except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Numerator: ​ ​ ​ ​ Net loss - basic and diluted ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) Denominator: ​ ​ ​ ​ Weighted average common shares outstanding used to compute basic and diluted net loss per share ​ 46,553,511 ​ 41,854,110 ​ 29,478,878 Net loss per share, basic and diluted ​ $ (0.89) ​ $ (1.03) ​ $ (0.20) ​ The amounts in the table below were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Outstanding options ​ 7,006,250 6,354,308 6,664,173 ​

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2022
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements Financial assets and liabilities are measured and recorded at fair value. The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: ● Level 1—Quoted prices in active markets for identical assets or liabilities ● Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly ● Level 3—Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability There have been no transfers of assets and liabilities between levels of hierarchy. The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs. The following tables present information as of December 31, 2022 and 2021 about the Company’s assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy the Company utilized to determine such fair values (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ Fair Value Measured Using ​ Total ​ (Level 1) (Level 2) (Level 3) Balance Assets ​ ​ ​ ​ Cash equivalents ​ $ 11,942 ​ $ — ​ $ — ​ $ 11,942 Marketable securities ​ 22,001 ​ 7,143 ​ — ​ 29,144 ​ ​ $ 33,943 ​ $ 7,143 ​ $ — ​ $ 41,086 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ Fair Value Measured Using ​ Total ​ (Level 1) (Level 2) (Level 3) Balance Assets ​ ​ ​ ​ Cash equivalents ​ $ 61,992 ​ $ — ​ $ — ​ $ 61,992 Marketable securities ​ ​ 1,011 ​ 4,982 ​ — ​ 5,993 ​ ​ $ 63,003 ​ $ 4,982 ​ $ — ​ $ 67,985 ​ As of December 31, 2022, marketable securities had a maximum remaining maturity of twelve months. As of December 31, 2022 and 2021, the fair value of available for sale marketable securities by type of security were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ Gross Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost ​ Gains ​ Losses ​ Value U.S. Treasury securities ​ $ 22,020 ​ $ 4 ​ $ (23) ​ $ 22,001 U.S. Government agency securities ​ ​ 7,175 ​ ​ — ​ ​ (32) ​ ​ 7,143 ​ ​ $ 29,195 ​ $ 4 ​ $ (55) ​ $ 29,144 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ ​ Gross Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost ​ Gains ​ Losses ​ Value U.S. Treasury securities ​ $ 1,012 ​ $ — ​ $ (2) ​ $ 1,010 U.S. Government agency securities ​ ​ 4,984 ​ ​ — ​ ​ (1) ​ ​ 4,983 ​ ​ $ 5,996 ​ $ — ​ $ (3) ​ $ 5,993 ​

Equity Method Investment

Equity Method Investment	12 Months Ended
	Dec. 31, 2022
Equity Method Investment
Equity Method Investment	5. Equity Method Investment In August 2020, the Company established Angel Pharmaceuticals Co. Ltd. (“Angel”), a wholly-owned corporate venture in the People’s Republic of China (“China”) designed to develop, manufacture, and commercialize CPI-818, ciforadenant and mupadolimab compounds for distribution within the countries of China, Taiwan, Macao, and Hong Kong (collectively, the “Territories”) based on intellectual property licenses to be contributed to Angel by the Company. In October 2020, Angel raised financing from third-party investors, the licenses were entered into and the Company’s ownership interest was reduced to 53.2%. Under the license agreements, the Company is required to provide manufacturing supply services for future supply of drug products for use in clinical trials, research and development, operational support, and participate in the joint steering committee which oversees the development and commercialization of the compounds. Angel is not required to make any payments to the Company regarding the licensed compounds or the additional services outlined in the agreement. Pursuant to the terms of the agreement, during the Exclusive Grant Back Period, Angel grants to Corvus an exclusive, fully paid-up and sublicensable license for sole and jointly owned IP. After the 7 year Exclusive Grant Back Period, the licenses for sole and jointly owned IP that Angel grants to the company will be non-exclusive, fully paid, and sublicensable. As a result of the financing, the Company reassessed its interest in Angel and determined that while Angel is a VIE, the Company is not considered the primary beneficiary of such VIE since Corvus does not have the power, through voting or similar rights and the license agreements, to direct the activities of Angel that most significantly impact Angel’s economic performance. Further, the Company determined that as it has a significant influence over Angel, and, therefore, it shall account for its investment in Angel using the equity method starting in October 2020, the date it lost control over Angel. At the date of loss of control, the Company derecognized all of Angel’s assets and liabilities from its balance sheet, recognized the retained equity interest at its fair value of $37.5 million, and recognized a gain of $37.5 million, which is included in gain on deconsolidation of Angel Pharmaceuticals on the consolidated statement of operations for the year ended December 31, 2020. As of December 31, 2022, the Company’s ownership interest in Angel was approximately 49.7%, excluding 7% of Angel’s equity reserved for issuance under the Angel ESOP. The Company recognized its share of losses in Angel for the total amount of $10.0 million, $4.8 million and $0.2 million as loss from equity method investment on the consolidated statement of operations for the years ended December 31, 2022, 2021 and 2020, respectively. Since inception through December 31, 2022, Angel has not recorded any revenue. Summary Financial Information Summary financial information for Angel Pharmaceuticals is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ As of Balance Sheet Data December 31, 2022 ​ December 31, 2021 ​ (in thousands) Current assets ​ $ 29,062 ​ $ 38,608 Non-current assets ​ 1,652 ​ 1,818 Current liabilities ​ 6,293 ​ 2,119 Non-current liabilities ​ 985 ​ 105 Stockholders' equity ​ ​ 23,436 ​ ​ 38,202 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Statement of Operations Data 2022 ​ 2021 ​ 2020 (1) ​ (in thousands) Net loss ​ $ (11,846) ​ $ (5,697) ​ $ (274) Share of loss from investments accounted for using the equity method ​ (10,005) ​ (4,831) ​ (234) ​ (1) The Company’s share of loss is based on net loss beginning October 2020 upon the deconsolidation of Angel Pharmaceuticals .

License and Collaboration Agree

License and Collaboration Agreements	12 Months Ended
	Dec. 31, 2022
License and Collaboration Agreements
License and Collaboration Agreements	6. License and Collaboration Agreements Scripps Licensing Agreement In December 2014, the Company entered into a license agreement with The Scripps Research Institute (“Scripps”), pursuant to which it was granted a non-exclusive, world-wide license for all fields of use under Scripps’ rights in certain know-how and technology related to a mouse hybridoma clone expressing an anti-human CD73 antibody, and to progeny, mutants or unmodified derivatives of such hybridoma and any antibodies expressed by such hybridoma, from which we developed CPI-006. Scripps also granted the Company the right to grant sublicenses in conjunction with other proprietary rights the Company holds, or to others collaborating with or performing services for the Company. Under this license agreement, Scripps has agreed not to grant any additional commercial licenses with respect to such materials, other than march-in rights granted to the U.S. government. Upon execution of the agreement, the Company made a one-time cash payment to Scripps of $10,000 in 2015 and is also obligated to pay a minimum annual fee to Scripps of $25,000. The one-time cash payment was recorded as research and development expense as technological feasibility of the asset had not been established and there was no alternative future use. A minimum annual fee payment is due on each anniversary of the effective date of the agreement for the term of the agreement. The Company is also required to make performance-based cash payments upon successful completion of clinical and sales milestones. The aggregate potential milestone payments are $2.5 million. The Company is also required to pay royalties on net sales of licensed products (including CPI-006) sold by it, its affiliates and its sublicensees at a rate in the low-single digits. In addition, should the Company sublicense the rights licensed under the agreement, it has agreed to pay a percentage of sublicense revenue received at specified rates that start at double digit percentages and decrease to single digit percentages based on the elapsed time from the effective date of the agreement and the time of entry into such sublicense. To date, no milestone payments have been made. The Company’s license agreement with Scripps will terminate upon expiration of its obligation to pay royalties to Scripps under the license agreement. The Company’s license agreement with Scripps is terminable by the consent of the parties, at will by the Company upon providing 90 days written notice to Scripps, or by Scripps for certain material breaches, or if the Company undergoes a bankruptcy event. In addition, Scripps may terminate the license on a product-by-product basis, or the entire agreement, if the Company fails to meet specified diligence obligations related to the development and commercialization of licensed products. Scripps may also terminate the agreement after the third anniversary of the effective date of the agreement if it reasonably believes, based on reports the Company provides to Scripps, that the Company has not used commercially reasonable efforts as required under the agreement, subject to a specified notice and cure period. Vernalis Licensing Agreement In February 2015, the Company entered into a license agreement with Vernalis (R&D) Limited (“Vernalis”), which was subsequently amended as of November 5, 2015, and, pursuant to which the Company was granted an exclusive, worldwide license under certain patent rights and know-how, including a limited right to grant sublicenses, for all fields of use to develop, manufacture and commercialize products containing certain adenosine receptor antagonists, including ciforadenant. Pursuant to this agreement, the Company made a one-time cash payment to Vernalis in the amount of $1.0 million, which was recorded as research and development expense as technological feasibility of the asset had not been established and there was no alternative future use. The Company is also required to make cash milestone payments to Vernalis upon the successful completion of clinical and regulatory milestones for licensed products depending on the indications for which such licensed products are developed and upon achievement of certain sales milestones. In February 2017, the Company made a milestone payment of $3.0 million to Vernalis following the expansion of a cohort of patients with renal cell cancer treated with single agent ciforadenant in the Company’s Phase 1/1b clinical trial. During the year ended December 31, 2022, no clinical or regulatory milestones were completed or paid to Vernalis and the aggregate potential milestone payments were approximately $220 million for all indications as of December 31, 2022. The Company has also agreed to pay Vernalis tiered incremental royalties based on the annual net sales of licensed products containing ciforadenant on a product-by-product and country-by-country basis, subject to certain offsets and reductions. The tiered royalty rates for products containing ciforadenant range from the mid-single digits up to the low-double digits on a country-by-country net sales basis. The royalties on other licensed products that do not include ciforadenant also increase with the amount of net sales on a product-by-product and country-by-country basis and range from the low-single digits up to the mid-single digits on a country-by-country net sales basis. The Company is also obligated to pay to Vernalis certain sales milestones as indicated above when worldwide net sales reach specified levels over an agreed upon time period. The agreement will expire on a product-by-product and country-by-country basis upon the expiration of the Company’s payment obligations to Vernalis in respect of a particular product and country. Both parties have the right to terminate the agreement for an uncured material breach by the other party. The Company may also terminate the agreement at its convenience by providing 90 days written notice, provided that the Company has not received notice of its own default under the agreement at the time the Company exercises such termination right. Vernalis may also terminate the agreement if the Company challenges a licensed patent or undergoes a bankruptcy event. Monash License Agreement In April 2017, the Company entered into a license agreement with Monash University (“Monash”), pursuant to which the Company was granted an exclusive, sublicensable worldwide license under certain know-how, patent rights and other intellectual property rights controlled by Monash to research, develop, and commercialize certain antibodies directed to CXCR2 for the treatment of human diseases. Upon execution of the agreement, the Company made a one-time cash payment to Monash of $275,000 and reimbursed Monash for certain patent prosecution costs incurred prior to execution of the agreement. The Company recorded these payments as research and development expenses for the year ended December 31, 2017. The Company is also obligated to pay an annual license maintenance fee to Monash of $25,000 until a certain development milestone is met with respect to the licensed product, after which no further maintenance fee will be due. The Company is also required to make development and sales milestone payments to Monash with respect to the licensed products. During the year ended December 31, 2022, no development or sales milestones were completed or paid to Monash and the aggregate potential milestones were $45.1 million as of December 31, 2022. The Company is also required to pay to Monash tiered royalties on net sales of licensed products sold by it, its affiliates and its sublicensees at a rate ranging in the low-single digits. In addition, should the Company sublicense its rights under the agreement, the Company has agreed to pay a percentage of sublicense revenue received at specified rates that are currently at low double digit percentages and decrease to single digit percentages based on the achievement of development milestones. The term of the Company’s agreement with Monash continues until the expiration of its obligation to pay royalties to Monash thereunder. The license agreement is terminable at will by the Company upon providing 30 days written notice to Monash, or by either party for material breaches by the other party. In addition, Monash may terminate the entire agreement or convert the license to a non-exclusive license if the Company has materially breached its obligation to use commercially reasonable efforts to develop and commercialize a licensed product, subject to a specified notice and cure mechanism.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2022
Balance Sheet Components
Balance Sheet Components	7. Balance Sheet Components (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Prepaid and Other Current Assets ​ ​ ​ ​ ​ ​ Interest receivable ​ $ 45 ​ $ 32 Prepaid research and development manufacturing expenses ​ ​ 192 ​ ​ 740 Prepaid facility expenses ​ ​ 182 ​ ​ 174 Prepaid insurance ​ ​ 252 ​ ​ 280 Other ​ 102 ​ 128 ​ ​ $ 773 ​ $ 1,354 Property and Equipment ​ ​ ​ ​ ​ ​ Laboratory equipment ​ $ 2,673 ​ $ 2,477 Computer equipment and purchased software ​ 142 ​ 142 Leasehold improvements ​ 2,084 ​ 2,084 ​ ​ 4,899 ​ 4,703 Less: accumulated depreciation and amortization ​ (4,546) ​ (4,252) ​ ​ $ 353 ​ $ 451 Accrued and Other Liabilities ​ ​ ​ ​ ​ ​ Accrued clinical trial expense ​ $ 2,934 ​ $ 4,010 Accrued manufacturing expense ​ 3,254 ​ 839 Personnel related ​ 1,113 ​ 1,846 Accrued legal and accounting ​ ​ 89 ​ ​ 265 Other ​ 158 ​ 121 ​ ​ $ 7,548 ​ $ 7,081 ​ ​ ​ ​ ​

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2022
Common Stock
Common Stock	8. Common Stock As of December 31, 2022, the amended and restated certificate of incorporation authorizes the Company to issue 290 million shares of common stock and 10 million shares of preferred stock. Each share of common stock is entitled to one vote. Common stockholders are entitled to dividends if and when declared by the board of directors. As of December 31, 2022, no dividends on common stock had been declared. In March 2020, the Company entered into an open market sale agreement (the “2020 Sales Agreement”) with Jefferies LLC (“Jefferies”) to sell shares of the Company’s common stock, from time-to-time, with aggregate gross sales proceeds of up to $50,000,000, through an at-the-market equity offering program under which Jefferies will act as its sales agent. In November 2021, the Company entered into another Sale Agreement (“2021 Sales Agreement”) with Jefferies to sell shares of our common stock from time-to-time, with aggregate gross sales proceeds of up to $40,000,000. The issuance and sale of shares of common stock by the Company pursuant to the Sales Agreements are deemed an “at-the-market” offering under the Securities Act of 1933, as amended. Jefferies is entitled to compensation for its services equal to up to 3.0% of the gross proceeds of any shares of common stock sold through Jefferies under the Sales Agreements. During the year ended December 31, 2022, the Company did not sell any shares of common stock under its at-the-market offering program. As of December 31, 2022, the Company had sold 6,920,339 shares of common stock for gross proceeds of $31.1 million under the 2020 Sales Agreement. As of December 31, 2022, $18.9 million remained for sale under the 2020 Sales Agreement and $40.0 million remained for sale under the 2021 Sales Agreement. The Company has reserved shares of common stock, for issuance as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Exchange warrants — ​ — ​ 1,458,000 Shares available for future option grants ​ 4,017,011 ​ 2,806,953 ​ 1,692,753 Outstanding options 7,006,250 ​ 6,354,308 ​ 6,664,173 Shares reserved for employee stock purchase plan 400,000 ​ 400,000 ​ 400,000 Total 11,423,261 ​ 9,561,261 ​ 10,214,926 ​

Stock Option Plans

Stock Option Plans	12 Months Ended
	Dec. 31, 2022
Stock Option Plans
Stock Option Plans	9. Stock Option Plans In February 2014, the Company adopted the 2014 Equity Incentive Plan (the “2014 Plan”), which was subsequently amended in November 2014, July 2015 and September 2015, under which it granted incentive stock options (“ISOs”) or non-qualified stock options (“NSOs”). Terms of stock agreements, including vesting requirements, are determined by the board of directors or a committee authorized by the board of directors, subject to the provisions of the 2014 Plan. In general, awards granted by the Company vest over four years and have maximum exercise term of 10 years. The 2014 Plan provides that grants must be at an exercise price of 100% of fair market value of the Company’s common stock as determined by the board of directors on the date of the grant. In connection with the consummation of the IPO in March 2016, the 2016 Equity Incentive Award Plan (the “2016 Plan”), became effective. Under the 2016 Plan, incentive stock options, non-statutory stock options, stock purchase rights and other stock-based awards may be granted. Terms of stock agreements, including vesting requirements, are determined by the board of directors or a committee authorized by the board of directors, subject to the provisions of the 2016 Plan. In general, awards granted by the Company vest over four years and have a maximum exercise term of 10 years. The 2016 Plan provides that grants must be at an exercise price of 100% of fair market value of the Company’s common stock as determined by the board of directors on the date of the grant. In conjunction with adopting the 2016 Plan, the 2014 Plan was terminated and no further awards will be granted under the 2014 Plan. Options outstanding under the 2014 Plan as of the effective date of the 2016 Plan that are forfeited or lapse unexercised may be re-issued under the 2016 Plan, up to a maximum of 1,136,229 shares. Activity under the Company’s stock option plans is set forth below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ ​ ​ Weighted ‑ ​ ​ Shares ​ ​ ​ Average ​ ​ Available ​ Number of ​ Exercise ​ for Grant Options Price Balance at December 31, 2021 2,806,953 6,354,308 ​ $ 6.80 Additional shares authorized 1,862,000 — ​ — Options granted (1,706,400) 1,706,400 ​ 1.02 Options forfeited 1,054,458 (1,054,458) ​ 7.75 Balance at December 31, 2022 4,017,011 7,006,250 ​ $ 5.25 ​ ​ ​ The weighted average grant date fair value of options granted for the years ended December 31, 2022, 2021 and 2020, was $0.69, $1.93 and $2.66, respectively. Options outstanding that had vested or were expected to vest at December 31, 2022 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Weighted ​ Remaining ​ Intrinsic ​ ​ Number ​ Average ​ Contractual ​ Value ​ ​ of shares ​ Exercise Price ​ Life (years) ​ (in thousands) Vested 4,121,317 ​ $ 7.51 5.95 ​ $ 19.95 Expected to vest 2,884,933 ​ $ 2.02 8.94 ​ $ — ​ In the table above, aggregate intrinsic value represents the difference between the exercise price of the options to purchase common stock and the fair value of the Company’s common stock of $0.85 per share as of December 31, 2022. The aggregate intrinsic value of stock options exercised in the years ended December 31, 2022, 2021 and 2020, was $0.0 million, $1.0 million and $0.3 million, respectively. The total fair value of options that vested in the year ended December 31, 2022, 2021 and 2020, was $2.8 million, $4.5 million, and $6.0 million, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2022
Stock-Based Compensation
Stock-Based Compensation	10. Stock-Based Compensation The Company’s results of operations include expenses relating to stock-based awards as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Research and development ​ $ 1,039 ​ $ 2,161 ​ $ 2,791 General and administrative ​ 1,653 ​ 2,071 ​ 2,956 Total ​ $ 2,692 ​ $ 4,232 ​ $ 5,747 ​ Valuation Assumptions The Company estimated the fair value of employee stock options using the Black-Scholes valuation model. The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period of the awards. The fair value of employee stock options were estimated using the following assumptions for the years ended December 31, 2022, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 2020 ​ Risk-free interest rate ​ 3.0 % 0.9 % 0.5 % Expected volatility ​ 83.8 % 86.7 % 82.7 % Expected term (in years) ​ 5.5 ​ 6.0 ​ 6.0 Expected dividend yield ​ 0 % 0 % 0 % ​ Risk-free Interest Rate: Volatility expected term. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Expected Term: Expected Dividends: At December 31, 2022, 2021 and 2020, the unrecognized compensation expense associated with respect to options granted to employees was $3.9 million, $5.9 million and $10.4 million, respectively, and is expected to be recognized on a straight-line basis over 2.44, 2.69, and 2.78 years, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Taxes
Income Taxes	11. Income Taxes The components of loss before income tax is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Domestic ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) Foreign ​ — ​ — ​ — ​ ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) ​ During the years ended December 31, 2022, 2021 and 2020, the Company recorded no income tax benefits for the net operating losses (NOLs) incurred due to the uncertainty of realizing a benefit from those items. A reconciliation of the Company’s effective tax rate to the U.S. Federal statutory rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Federal tax benefit at statutory rate ​ 21 % 21 % 21 % State tax, net of Federal benefit ​ 8 % 9 % 14 % Change in valuation allowance ​ (22) % (26) % (24) % Research and development tax credits ​ 2 % 3 % 19 % Share based Compensation ​ (1) % (1) % (10) % 162(m) covered employees compensation limitation ​ — % — % (6) ​ FIN48 Reserve ​ — % (1) % (161) % Investment in Angel ​ (7) % (3) % 174 ​ Gain on transfer of intellectual property ​ — ​ — % (20) ​ Prior year federal true-up ​ — % (1) % (7) % Other ​ (1) % (1) ​ — ​ Effective income tax rate ​ 0 % 0 % 0 % ​ The effective tax rate is different from the federal statutory tax rate primarily due to a foreign rate differential and a valuation allowance against deferred tax assets as a result of the Company’s history of losses. The principal components of the Company’s net deferred tax assets are as follows (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Deferred tax assets ​ ​ ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 56,030 ​ $ 52,539 ​ $ 42,344 Tax credit carryforwards ​ 9,888 ​ 9,181 ​ 7,894 Capitalized tax assets ​ 155 ​ 125 ​ 63 Accruals ​ 124 ​ 137 ​ 207 Stock compensation ​ ​ 5,487 ​ ​ 5,006 ​ ​ 4,942 Operating lease liability ​ ​ 728 ​ ​ 1,021 ​ ​ 646 IRC 174 capitalization ​ ​ 4,518 ​ ​ — ​ ​ — Other ​ 21 ​ 12 ​ 47 Total deferred tax assets ​ $ 76,951 ​ $ 68,021 ​ $ 56,143 Deferred tax liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease right-of-use asset ​ $ (620) ​ $ (893) ​ $ (461) Valuation allowance ​ (76,331) ​ (67,128) ​ (55,682) Net deferred tax assets ​ $ — ​ $ — ​ $ — ​ The Company recorded a valuation allowance against its deferred tax assets at December 31, 2022 and 2021 because Company management believed that it was more likely than not that these assets would not be fully realized in the future. The valuation allowance increased by approximately $9.2 million and $11.4 million for the years ended December 31, 2022 and 2021, respectively. Changes in the valuation allowance for deferred tax assets relate primarily to the increase in the Company’s net operating loss carryforward. As of December 31, 2022, the Company had federal NOL carryforwards of approximately $219.7 million and state NOL carryforwards of approximately $274.9 million which are available to reduce future taxable income. The NOLs will begin to expire in 2034, if not utilized. As of December 31, 2022, the amount of federal NOL carryforwards that does not expire, is $155.3 million. Utilization of the net operating loss carryforwards are subject to various limitations due to the ownership change limitations provided by Internal Revenue Code (IRC) Section 382 and similar state provisions. As of December 31, 2022, the Company also had $8.6 million of federal and $4.7 million of state research and development tax credit carryforwards available to reduce future income taxes. The federal research and development tax credits will begin to expire 2035, if not utilized. The state research and development tax credits have no expiration date. In December 2017, the Tax Cuts and Jobs Act (TCJA) was signed into law, significantly reforming the Internal Revenue Code of 1986, as amended (IRC). The TCJA contained certain provisions that went into effect on January 1, 2022, including a provision impacting Section 174 of the IRC whereby for tax years beginning on or after January 1, 2022, taxpayers are required to capitalize and amortize, rather than deduct, research and development (R&D) expenses. The R&D expenses under Section 174 must be amortized over five years for research performed in the U.S. and 15 years for research performed outside the U.S. The mandatory capitalization requirement did not impact the Company’s net deferred tax assets and 2022 cash tax liabilities. The Company will continue to monitor the effect of these provisions and is in the process of analyzing the potential impact to its income taxes and financial position in future years. U.S. income and foreign withholding taxes have not been recognized on the excess of the amount for financial reporting over the tax basis of investments in foreign subsidiaries that are essentially permanent in duration. This excess totaled approximately $21.9 million as of December 31, 2022, which will be indefinitely reinvested; deferred income taxes have not been provided on such foreign earnings. As of December 31, 2022, the Company had unrecognized tax benefits (“UTBs”) of approximately $12.7 million. All of the deferred tax assets associated with these UTBs are fully offset by a valuation allowance. The following table summarizes the activity related to UTBs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Unrecognized tax benefits beginning of the period ​ $ 12,504 ​ $ 12,157 ​ $ 1,885 Decrease related to the prior year ​ — ​ — ​ — Increased related to the current year ​ 216 ​ 347 ​ 10,272 Unrecognized tax benefits, end of the period ​ $ 12,720 ​ $ 12,504 ​ $ 12,157 ​ The Company follows the provisions of ASC 740, Accounting for Income Taxes, and the accounting guidance related to accounting for uncertainty in income taxes. The Company determines its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be sustained upon examination by the relevant income tax authorities. None of the Company’s unrecognized tax benefits that, if recognized, would affect its effective tax rate. The Company does not anticipate the total amounts of unrecognized tax benefits will significantly increase or decrease in the next 12 months. The Company will recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. Management determined that no accrual for interest or penalties was required as of December 31, 2022, 2021 and 2020. The Company currently has no federal or state tax examinations in progress nor has it had any federal or state examinations since inception. As a result of the Company’s net operating loss carryforwards, all of its tax years are subject to federal, state and foreign tax examinations.

Facility Lease

Facility Lease	12 Months Ended
	Dec. 31, 2022
Facility Lease
Facility lease	12. Facility Lease In January 2015, the Company signed an initial operating lease, effective February 1, 2015 for 8,138 square feet of office and laboratory space with a one year term. Between January 2015 and September 2021, the Company entered into a series of lease amendments to increase the amount of leased space to 27,280 square feet and extend the expiration of the lease to February 2025. The lease agreement includes annual rent escalations. Under the lease and subsequent amendments, the landlord provided approximately $1.9 million in free rent and lease incentives. The Company records rent expense on a straight-line basis over the effective term of the lease, including any free rent periods and incentives. As the interest rate implicit in lease arrangements is typically not readily available, in calculating the present value of the lease payments, the Company has utilized its incremental borrowing rate, which is determined based on the prevailing market rates for collateralized debt with maturity dates commensurate with the term of its lease In September 2021, the Company entered into a lease amendment to extend the expiration of its operating lease by two years, from February 2023 to February 2025. As a result of this lease extension, the Company recorded a $2.4 million increase in the operating lease right-of-use asset and a corresponding increase in the operating lease liability As of December 31, 2022 and 2021, the right-of-use asset under operating lease was $2.2 million and $3.2 million, respectively. The elements of lease expense were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ Statements of operations and ​ December 31, ​ ​ comprehensive loss location ​ 2022 2021 2020 ​ Costs of operating lease ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease costs ​ Research and development, ​ $ 1,051 ​ $ 1,046 ​ $ 957 ​ Costs of non-lease components (previously common area maintenance) ​ Research and development, ​ ​ 351 ​ ​ 396 ​ ​ 351 ​ Total operating lease cost ​ ​ ​ $ 1,402 ​ $ 1,442 ​ $ 1,308 ​ Other Information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating cash flows used for operating lease ​ ​ ​ $ 1,695 ​ $ 1,645 ​ $ 1,506 ​ Remaining lease term ​ ​ ​ 2.1 years ​ 3.1 years ​ 2.1 years ​ Discount rate ​ ​ ​ 8.0% ​ 8.0% ​ 10.0% ​ ​ As of December 31, 2022, minimum rental commitments under this lease were as follows (in thousands) ​ ​ ​ ​ Year Ended December 31 (in thousands) ​ ​ 2023 ​ $ 1,391 2024 ​ ​ 1,434 Total lease payments ​ 2,825 Less: imputed interest ​ ​ (224) Total $ 2,601 ​ As of December 31, 2021, minimum rental commitments under this lease were as follows (in thousands) ​ ​ ​ ​ Year Ended December 31 (in thousands) ​ ​ 2022 ​ $ 1,300 2023 ​ 1,391 2024 ​ ​ 1,434 Total lease payments ​ 4,125 Less: imputed interest ​ ​ (478) Total $ 3,647 ​

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies
Commitments and Contingencies	13. Commitments and Contingencies In August 2015, the Company entered into an agreement for a line of credit of $0.1 million for the purpose of issuing its landlord a letter of credit of $0.1 million as a security deposit under its facility lease. The Company pledged money market funds and marketable securities as collateral for the line of credit. For further discussion of the Company’s facility lease agreement, see Note 12. Indemnifications In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. There have been no claims to date and the Company has a directors and officers insurance policy that may enable it to recover a portion of any amounts paid for future claims. Legal Proceedings The Company is not a party to any material legal proceedings.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2022
Related Party Transactions
Related Party Transactions	14. Related Party Transactions ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ Aggregate ​ ​ ​ Shares of ​ Purchase ​ Common Stock Price Owners of More Than 10% of Our Common Stock ​ ​ ​ ​ ​ ​ OrbiMed Advisors LLC (1) ​ ​ 1,285,714 ​ $ 4,499,999 Board of Directors ​ ​ ​ ​ ​ ​ Richard A. Miller, M.D. ​ ​ 100,000 ​ ​ 350,000 ​ (1) Peter Thompson, M.D., a member of our Board of Directors since November 2014, is a Member of OrbiMed Advisors, LLC. ​ clinical drug supply passthrough costs incurred during the years ended December 31, 2022 and 2021, respectively, and did not have an impact on the Company’s consolidated statements of operations. ​ ​ ​

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2022
Subsequent Event
Subsequent Event	15. Subsequent Events ​ ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Company’s functional and reporting currency is the U.S. dollar, except for its investment in its equity method investee which is the Chinese renminbi (RMB). The accompanying consolidated financial statements have been prepared on a going-concern basis, which contemplates the realization of assets and discharge of liabilities in the normal course of business. Since its inception, the Company has incurred significant losses and negative cash flows from operations. As of December 31, 2022, the Company had an accumulated deficit of $307.7 million and cash, cash equivalents and marketable securities of $42.3 million. The Company has financed its operations primarily with the proceeds from the sale of stock. The Company will need to raise additional capital to meet its business objectives. The Company believes that its current cash, cash equivalents and marketable securities will be sufficient to fund its planned expenditures and meet its obligations through at least the next twelve months from the issuance of these financial statements.
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from such estimates.
Concentrations of Credit Risk and Other Risks and Uncertainties	Concentrations of Credit Risk and Other Risks and Uncertainties Substantially all of the Company’s cash and cash equivalents are deposited in accounts with two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company maintains its cash with an accredited financial institution and accordingly, such funds are subject to minimal credit risk. The Company’s marketable securities consist of investments in U.S. Treasury securities and U.S. government agency securities, which can be subject to certain credit risks. However, the Company mitigates the risks by investing in high-grade instruments, limiting its exposure to any one issuer, and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any losses on its deposits of cash, cash equivalents or marketable securities. The Company is subject to a number of risks similar to other early stage biopharmaceutical companies, including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, its reliance on third parties to conduct its clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s product candidates, its right to develop and commercialize its product candidates pursuant to the terms and conditions of the licenses granted to the Company, and protection of proprietary technology. If the Company does not successfully commercialize or partner any of its product candidates, it will be unable to generate product revenue or achieve profitability.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment, that of the development of and commercialization of drugs and antibodies that target critical elements of the immune system.
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The Company considers all highly liquid investment securities with remaining maturities at the date of purchase of three months or less to be cash equivalents. Investments with remaining maturities, at the date of purchase, greater than three months are classified as “available-for-sale” and are carried at fair value with unrealized gains and losses, if any, included as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Interest and realized gains and losses are included in interest income. Realized gains and losses are recognized based on the specific identification model.
Fair Value Measurements	Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, accounts payable and accrued liabilities, approximate fair value due to their short-term maturities.
Investments in Equity Securities	Investments in Equity Securities For equity method investees with a functional currency different than the Company’s reporting currency, the Company follows the guidance under ASC 830-10-15-5, pursuant to which, the foreign currency financial statements of a foreign investee accounted for by the equity method should be translated to the reporting entity's reporting currency.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets: ​ ​ ​ ​ Laboratory equipment 5 years Computer equipment and purchased software ​ 3 years Leasehold improvements ​ Shorter of asset's useful life or remaining term of lease ​ Maintenance and repairs that do not extend the life or improve the asset are expensed when incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation or amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the asset or asset group. Should impairment exist, the impairment loss to be recognized is measured by the amount by which the carrying amount of the asset exceeds the projected discounted future net cash flows arising from the asset. All long-lived assets are maintained in the United States of America.
Clinical Trial Accruals	Clinical Trial Accruals Costs for preclinical studies and clinical trial activities are recognized based on an evaluation of the vendors’ progress towards completion of specific tasks. The Company applies significant judgment in developing estimates for clinical trial accruals based on assumptions related to vendors’ progress towards completion. In developing these estimates, management estimates vendors’ progress towards completion using data such as clinical site activations, patient enrollment or information provided to the Company by its vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. The Company determines accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion, or the services completed. The Company’s estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time.
Stock-Based Compensation	Stock-Based Compensation The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non-employee service providers. The Company accounts for stock-based employee compensation arrangements in accordance with the provisions of ASC 718, “Compensation—Stock Compensation.” For stock options granted to employees, the Company recognizes compensation expense for all stock-based awards based on the grant-date estimated fair values. The value of the award is recognized as an expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. Forfeitures are accounted for when they occur. Stock-based compensation expense related to stock options granted to non-employees is recognized based on the fair value of the stock options, determined using the Black-Scholes option pricing model. The awards generally vest over the time period the Company expects to receive service from the non-employee.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differences in accounting for reporting purposes and tax purposes for certain items, such as accruals and allowances not currently deductible for tax purposes. These temporary differences result in deferred tax assets and liabilities, which are included in the Company’s balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the Company’s statements of operations and comprehensive loss become deductible expenses, under applicable income tax laws or when net operating loss or credit carryforwards are utilized. Accordingly, realization of the Company’s deferred tax assets is dependent on future taxable income against which these deductions, losses and credits can be utilized. The Company must assess the likelihood that the Company’s deferred tax assets will be recovered from future taxable income and a valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Based on the available evidence, the Company is unable, at this time, to support the determination that it is more likely than not that its deferred tax assets will be utilized in the future. Accordingly, the Company recorded a full valuation allowance for all periods presented. The Company intends to maintain a valuation allowance until sufficient evidence exists to support its reversal. The Company recognizes benefits of uncertain tax positions if it is more likely than not such positions will be sustained upon examination based solely on their technical merits as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. The Company is required to file income tax returns in the U.S. federal jurisdiction. The Company currently is not under examination by the Internal Revenue Service or other jurisdictions for any tax years.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s elements of other comprehensive loss in any period presented were unrealized gains and losses on available-for-sale marketable securities and cumulative foreign currency translation adjustments.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of common shares outstanding and Exchange Warrants outstanding during the period, without consideration of potentially dilutive securities. In accordance with Accounting Standards Codification Topic 260, Earnings Per Share
Recent Accounting Pronouncements	Recent Accounting Pronouncements

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Schedule of estimated useful lives of property and equipment, net	Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets: ​ ​ ​ ​ Laboratory equipment 5 years Computer equipment and purchased software ​ 3 years Leasehold improvements ​ Shorter of asset's useful life or remaining term of lease ​

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2022
Net Loss per Share
Schedule of net loss per share, basic and diluted	The following table shows the calculation of net loss per share (in thousands, except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Numerator: ​ ​ ​ ​ Net loss - basic and diluted ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) Denominator: ​ ​ ​ ​ Weighted average common shares outstanding used to compute basic and diluted net loss per share ​ 46,553,511 ​ 41,854,110 ​ 29,478,878 Net loss per share, basic and diluted ​ $ (0.89) ​ $ (1.03) ​ $ (0.20) ​
Schedule of antidilutive securities excluded from calculation of diluted net loss per share	The amounts in the table below were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Outstanding options ​ 7,006,250 6,354,308 6,664,173

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value Measurements
Schedule of fair value of assets measured at fair value on a recurring basis, by level of fair value hierarchy	The following tables present information as of December 31, 2022 and 2021 about the Company’s assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy the Company utilized to determine such fair values (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ Fair Value Measured Using ​ Total ​ (Level 1) (Level 2) (Level 3) Balance Assets ​ ​ ​ ​ Cash equivalents ​ $ 11,942 ​ $ — ​ $ — ​ $ 11,942 Marketable securities ​ 22,001 ​ 7,143 ​ — ​ 29,144 ​ ​ $ 33,943 ​ $ 7,143 ​ $ — ​ $ 41,086 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ Fair Value Measured Using ​ Total ​ (Level 1) (Level 2) (Level 3) Balance Assets ​ ​ ​ ​ Cash equivalents ​ $ 61,992 ​ $ — ​ $ — ​ $ 61,992 Marketable securities ​ ​ 1,011 ​ 4,982 ​ — ​ 5,993 ​ ​ $ 63,003 ​ $ 4,982 ​ $ — ​ $ 67,985 ​
Schedule of fair value of available for sale marketable securities	As of December 31, 2022 and 2021, the fair value of available for sale marketable securities by type of security were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ Gross Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost ​ Gains ​ Losses ​ Value U.S. Treasury securities ​ $ 22,020 ​ $ 4 ​ $ (23) ​ $ 22,001 U.S. Government agency securities ​ ​ 7,175 ​ ​ — ​ ​ (32) ​ ​ 7,143 ​ ​ $ 29,195 ​ $ 4 ​ $ (55) ​ $ 29,144 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ ​ Gross Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost ​ Gains ​ Losses ​ Value U.S. Treasury securities ​ $ 1,012 ​ $ — ​ $ (2) ​ $ 1,010 U.S. Government agency securities ​ ​ 4,984 ​ ​ — ​ ​ (1) ​ ​ 4,983 ​ ​ $ 5,996 ​ $ — ​ $ (3) ​ $ 5,993

Equity Method Investment (Table

Equity Method Investment (Tables)	12 Months Ended
	Dec. 31, 2022
Equity Method Investment
Schedule of financial information of Angel Pharmaceuticals Co.	Summary financial information for Angel Pharmaceuticals is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ As of Balance Sheet Data December 31, 2022 ​ December 31, 2021 ​ (in thousands) Current assets ​ $ 29,062 ​ $ 38,608 Non-current assets ​ 1,652 ​ 1,818 Current liabilities ​ 6,293 ​ 2,119 Non-current liabilities ​ 985 ​ 105 Stockholders' equity ​ ​ 23,436 ​ ​ 38,202 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Statement of Operations Data 2022 ​ 2021 ​ 2020 (1) ​ (in thousands) Net loss ​ $ (11,846) ​ $ (5,697) ​ $ (274) Share of loss from investments accounted for using the equity method ​ (10,005) ​ (4,831) ​ (234) ​ (1) The Company’s share of loss is based on net loss beginning October 2020 upon the deconsolidation of Angel Pharmaceuticals .

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2022
Balance Sheet Components
Schedule of balance sheet components	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Prepaid and Other Current Assets ​ ​ ​ ​ ​ ​ Interest receivable ​ $ 45 ​ $ 32 Prepaid research and development manufacturing expenses ​ ​ 192 ​ ​ 740 Prepaid facility expenses ​ ​ 182 ​ ​ 174 Prepaid insurance ​ ​ 252 ​ ​ 280 Other ​ 102 ​ 128 ​ ​ $ 773 ​ $ 1,354 Property and Equipment ​ ​ ​ ​ ​ ​ Laboratory equipment ​ $ 2,673 ​ $ 2,477 Computer equipment and purchased software ​ 142 ​ 142 Leasehold improvements ​ 2,084 ​ 2,084 ​ ​ 4,899 ​ 4,703 Less: accumulated depreciation and amortization ​ (4,546) ​ (4,252) ​ ​ $ 353 ​ $ 451 Accrued and Other Liabilities ​ ​ ​ ​ ​ ​ Accrued clinical trial expense ​ $ 2,934 ​ $ 4,010 Accrued manufacturing expense ​ 3,254 ​ 839 Personnel related ​ 1,113 ​ 1,846 Accrued legal and accounting ​ ​ 89 ​ ​ 265 Other ​ 158 ​ 121 ​ ​ $ 7,548 ​ $ 7,081

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2022
Common Stock
Schedule of shares of common stock reserved for issuance	The Company has reserved shares of common stock, for issuance as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Exchange warrants — ​ — ​ 1,458,000 Shares available for future option grants ​ 4,017,011 ​ 2,806,953 ​ 1,692,753 Outstanding options 7,006,250 ​ 6,354,308 ​ 6,664,173 Shares reserved for employee stock purchase plan 400,000 ​ 400,000 ​ 400,000 Total 11,423,261 ​ 9,561,261 ​ 10,214,926

Stock Option Plans (Tables)

Stock Option Plans (Tables)	12 Months Ended
	Dec. 31, 2022
Stock Option Plans
Schedule of stock option activity	Activity under the Company’s stock option plans is set forth below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ ​ ​ Weighted ‑ ​ ​ Shares ​ ​ ​ Average ​ ​ Available ​ Number of ​ Exercise ​ for Grant Options Price Balance at December 31, 2021 2,806,953 6,354,308 ​ $ 6.80 Additional shares authorized 1,862,000 — ​ — Options granted (1,706,400) 1,706,400 ​ 1.02 Options forfeited 1,054,458 (1,054,458) ​ 7.75 Balance at December 31, 2022 4,017,011 7,006,250 ​ $ 5.25 ​
Schedule of options outstanding and exercisable that had vested or were expected to vest	Options outstanding that had vested or were expected to vest at December 31, 2022 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Weighted ​ Remaining ​ Intrinsic ​ ​ Number ​ Average ​ Contractual ​ Value ​ ​ of shares ​ Exercise Price ​ Life (years) ​ (in thousands) Vested 4,121,317 ​ $ 7.51 5.95 ​ $ 19.95 Expected to vest 2,884,933 ​ $ 2.02 8.94 ​ $ — ​

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of expenses relating to employee and non-employee stock-based awards	The Company’s results of operations include expenses relating to stock-based awards as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Research and development ​ $ 1,039 ​ $ 2,161 ​ $ 2,791 General and administrative ​ 1,653 ​ 2,071 ​ 2,956 Total ​ $ 2,692 ​ $ 4,232 ​ $ 5,747 ​
Employee stock options
Schedule of fair value of share-based awards to employees was estimated using Black Scholes model	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 2020 ​ Risk-free interest rate ​ 3.0 % 0.9 % 0.5 % Expected volatility ​ 83.8 % 86.7 % 82.7 % Expected term (in years) ​ 5.5 ​ 6.0 ​ 6.0 Expected dividend yield ​ 0 % 0 % 0 % ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Taxes
Schedule of components of loss before income tax	The components of loss before income tax is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Domestic ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) Foreign ​ — ​ — ​ — ​ ​ $ (41,307) ​ $ (43,241) ​ $ (5,995) ​
Schedule of reconciliation of the effective tax rate to the U.S. Federal statutory rate	A reconciliation of the Company’s effective tax rate to the U.S. Federal statutory rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Federal tax benefit at statutory rate ​ 21 % 21 % 21 % State tax, net of Federal benefit ​ 8 % 9 % 14 % Change in valuation allowance ​ (22) % (26) % (24) % Research and development tax credits ​ 2 % 3 % 19 % Share based Compensation ​ (1) % (1) % (10) % 162(m) covered employees compensation limitation ​ — % — % (6) ​ FIN48 Reserve ​ — % (1) % (161) % Investment in Angel ​ (7) % (3) % 174 ​ Gain on transfer of intellectual property ​ — ​ — % (20) ​ Prior year federal true-up ​ — % (1) % (7) % Other ​ (1) % (1) ​ — ​ Effective income tax rate ​ 0 % 0 % 0 % ​
Schedule of principal components of the net deferred tax assets	The principal components of the Company’s net deferred tax assets are as follows (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Deferred tax assets ​ ​ ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 56,030 ​ $ 52,539 ​ $ 42,344 Tax credit carryforwards ​ 9,888 ​ 9,181 ​ 7,894 Capitalized tax assets ​ 155 ​ 125 ​ 63 Accruals ​ 124 ​ 137 ​ 207 Stock compensation ​ ​ 5,487 ​ ​ 5,006 ​ ​ 4,942 Operating lease liability ​ ​ 728 ​ ​ 1,021 ​ ​ 646 IRC 174 capitalization ​ ​ 4,518 ​ ​ — ​ ​ — Other ​ 21 ​ 12 ​ 47 Total deferred tax assets ​ $ 76,951 ​ $ 68,021 ​ $ 56,143 Deferred tax liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease right-of-use asset ​ $ (620) ​ $ (893) ​ $ (461) Valuation allowance ​ (76,331) ​ (67,128) ​ (55,682) Net deferred tax assets ​ $ — ​ $ — ​ $ — ​
Schedule of unrecognized tax benefits activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 2020 Unrecognized tax benefits beginning of the period ​ $ 12,504 ​ $ 12,157 ​ $ 1,885 Decrease related to the prior year ​ — ​ — ​ — Increased related to the current year ​ 216 ​ 347 ​ 10,272 Unrecognized tax benefits, end of the period ​ $ 12,720 ​ $ 12,504 ​ $ 12,157 ​

Facility Lease (Tables)

Facility Lease (Tables)	12 Months Ended
	Dec. 31, 2022
Facility Lease
Schedule of Operating Lease Costs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ Statements of operations and ​ December 31, ​ ​ comprehensive loss location ​ 2022 2021 2020 ​ Costs of operating lease ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease costs ​ Research and development, ​ $ 1,051 ​ $ 1,046 ​ $ 957 ​ Costs of non-lease components (previously common area maintenance) ​ Research and development, ​ ​ 351 ​ ​ 396 ​ ​ 351 ​ Total operating lease cost ​ ​ ​ $ 1,402 ​ $ 1,442 ​ $ 1,308 ​ Other Information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating cash flows used for operating lease ​ ​ ​ $ 1,695 ​ $ 1,645 ​ $ 1,506 ​ Remaining lease term ​ ​ ​ 2.1 years ​ 3.1 years ​ 2.1 years ​ Discount rate ​ ​ ​ 8.0% ​ 8.0% ​ 10.0% ​
Schedule of Minimum rental commitments	As of December 31, 2022, minimum rental commitments under this lease were as follows (in thousands) ​ ​ ​ ​ Year Ended December 31 (in thousands) ​ ​ 2023 ​ $ 1,391 2024 ​ ​ 1,434 Total lease payments ​ 2,825 Less: imputed interest ​ ​ (224) Total $ 2,601 ​ As of December 31, 2021, minimum rental commitments under this lease were as follows (in thousands) ​ ​ ​ ​ Year Ended December 31 (in thousands) ​ ​ 2022 ​ $ 1,300 2023 ​ 1,391 2024 ​ ​ 1,434 Total lease payments ​ 4,125 Less: imputed interest ​ ​ (478) Total $ 3,647 ​

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2022
Related Party Transactions
Schedule of common stock sold to related parties	​ ​ ​ ​ ​ ​ ​ ​ Number of ​ Aggregate ​ ​ ​ Shares of ​ Purchase ​ Common Stock Price Owners of More Than 10% of Our Common Stock ​ ​ ​ ​ ​ ​ OrbiMed Advisors LLC (1) ​ ​ 1,285,714 ​ $ 4,499,999 Board of Directors ​ ​ ​ ​ ​ ​ Richard A. Miller, M.D. ​ ​ 100,000 ​ ​ 350,000 ​ (1) Peter Thompson, M.D., a member of our Board of Directors since November 2014, is a Member of OrbiMed Advisors, LLC.

Organization - Public Offerings

Organization - Public Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended			12 Months Ended
	Nov. 08, 2019	Apr. 26, 2016	Mar. 29, 2016	Sep. 30, 2021	Feb. 28, 2021	Mar. 31, 2018	Dec. 31, 2021	Dec. 31, 2022
Public Offerings
Proceeds from sale of stock							$ 31,989
Accumulated deficit							$ 266,381	$ 307,688
Cash, cash equivalents and short-term marketable securities								$ 42,300
Issuance of common stock				1,457,947
Common stock, par value (in dollars per share)							$ 0.0001	$ 0.0001
Exchange Warrants
Public Offerings
Issuance of common stock	1,458,000
Common stock, par value (in dollars per share)	$ 0.0001
Exchange warrants issued	1,458,000
Warrant exercise price	$ 0.0001
Percentage of shares owned by exchanging shareholders	9.99%
Follow-on Public Offering
Public Offerings
Share offering price					$ 3.50	$ 8.50
Proceeds from sale of stock					$ 32,000	$ 64,900
Issuance of common stock					9,783,660	8,117,647
Over-Allotment Option
Public Offerings
Share offering price		$ 15
Issuance of common stock		502,618			1,212,231	1,058,823
IPO
Public Offerings
Share offering price			$ 15
Net proceeds from IPO		$ 70,600
Issuance of common stock			4,700,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) item segment	Dec. 31, 2021 USD ($)
Accumulated deficit	$ (307,688)	$ (266,381)
Cash, cash equivalents and marketable securities	42,300
Accumulated other comprehensive income	$ (563)	$ 1,869
Concentrations of Credit Risk and Other Risks and Uncertainties
Number of financial institutions used for cash and cash equivalent deposits | item	2
Segments
Number of operating segments | segment	1
Laboratory equipment
Property and Equipment, Net
Estimated Useful lives	5 years
Computer equipment and purchased software
Property and Equipment, Net
Estimated Useful lives	3 years
Leasehold improvements
Property and Equipment, Net
Leasehold improvements useful life	Shorter of asset's useful life or remaining term of lease

Net Loss per Share - Net Loss p

Net Loss per Share - Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss - basic and diluted	$ (41,307)	$ (43,241)	$ (5,995)
Denominator:
Weighted average common shares outstanding used to compute basic net loss per share	46,553,511	41,854,110	29,478,878
Weighted average common shares outstanding used to compute diluted net loss per share	46,553,511	41,854,110	29,478,878
Net loss per share, basic	$ (0.89)	$ (1.03)	$ (0.20)
Net loss per share, diluted	$ (0.89)	$ (1.03)	$ (0.20)

Net Loss per Share - Anti-Dilut

Net Loss per Share - Anti-Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Outstanding options
Excluded from the calculation of diluted net loss per share, due to anti-dilutive effect
Anti dilutive securities were excluded from the calculation of diluted net loss per share	7,006,250	6,354,308	6,664,173

Fair Value Measurements - Recur

Fair Value Measurements - Recurring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Assets
Maximum remaining maturity of marketable securities	12 months
Recurring
Assets
Cash equivalents	$ 11,942	$ 61,992
Marketable securities	29,144	5,993
Total Assets	41,086	67,985
Recurring | Level 1
Assets
Cash equivalents	11,942	61,992
Marketable securities	22,001	1,011
Total Assets	33,943	63,003
Recurring | Level 2
Assets
Marketable securities	7,143	4,982
Total Assets	$ 7,143	$ 4,982

Fair Value Measurements - Avail

Fair Value Measurements - Available For Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair value of available for sale marketable securities
Amortized Cost	$ 29,195	$ 5,996
Gross Unrealized Gains	4
Gross Unrealized Losses	(55)	(3)
Fair Value	29,144	5,993
U.S. Treasury securities
Fair value of available for sale marketable securities
Amortized Cost	22,020	1,012
Gross Unrealized Gains	4
Gross Unrealized Losses	(23)	(2)
Fair Value	22,001	1,010
U.S. Government agency securities
Fair value of available for sale marketable securities
Amortized Cost	7,175	4,984
Gross Unrealized Losses	(32)	(1)
Fair Value	$ 7,143	$ 4,983

Equity Method Investment (Detai

Equity Method Investment (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Gain on deconsolidation of Angel Pharmaceuticals				$ 37,459
Loss from equity method investment		$ 10,005	$ 4,831	234
Net loss		$ (41,307)	(43,241)	(5,995)
Angel Pharmaceuticals
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	53.20%	49.70%
Exclusive grant back period	7 years
Equity reserved (as percent)		7%
Investment in Angel, fair value	$ 37,500
Gain on deconsolidation of Angel Pharmaceuticals	$ 37,500
Loss from equity method investment		$ 10,000	4,800	200
Net loss		(11,846)	(5,697)	(274)
Share of loss from investments accounted for using the equity method		$ (10,005)	$ (4,831)	$ (234)

Equity Method Investment - Summ

Equity Method Investment - Summary Financial Information (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Current assets	$ 43,664	$ 71,312
Current liabilities	10,752	9,692
Stockholders' equity	56,115	97,162	$ 72,148	$ 71,111
Angel Pharmaceuticals
Schedule of Equity Method Investments [Line Items]
Current assets	29,062	38,608
Non-current assets	1,652	1,818
Current liabilities	6,293	2,119
Non-current liabilities	985	105
Stockholders' equity	$ 23,436	$ 38,202

License and Collaboration Agr_2

License and Collaboration Agreements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Feb. 28, 2017	Dec. 31, 2015	Feb. 28, 2015
Monash License
License and Collaboration Agreements
Minimum annual fee	$ 25,000
Period of written notice to terminate	30 days
Monash License | Maximum
License and Collaboration Agreements
Aggregate potential milestone payments	$ 45,100,000
Monash License | Research and development
License and Collaboration Agreements
One-time cash payment	275,000
Licensing Agreement | Scripps Research Institute
License and Collaboration Agreements
Minimum annual fee			$ 25,000
Aggregate potential milestone payments	2,500,000
Milestone payments made	$ 0
Period of written notice to terminate	90 days
Licensing Agreement | Scripps Research Institute | Research and development
License and Collaboration Agreements
One-time cash payment			$ 10,000
Licensing Agreement | Vernalis (R&D) Limited
License and Collaboration Agreements
Milestone payments made		$ 3,000,000
Period of written notice to terminate	90 days
Licensing Agreement | Vernalis (R&D) Limited | Minimum
License and Collaboration Agreements
Aggregate potential milestone payments	$ 220,000,000
Licensing Agreement | Vernalis (R&D) Limited | Research and development
License and Collaboration Agreements
One-time cash payment				$ 1,000,000

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Prepaid and Other Current Assets
Interest receivable	$ 45	$ 32
Prepaid research and development manufacturing expenses	192	740
Prepaid facility expenses	182	174
Prepaid insurance	252	280
Other	102	128
Total of prepaid and other current assets	$ 773	$ 1,354

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment
Property and equipment, gross	$ 4,899	$ 4,703
Less: accumulated depreciation and amortization	(4,546)	(4,252)
Property and equipment, net	353	451
Laboratory equipment
Property and Equipment
Property and equipment, gross	2,673	2,477
Computer equipment and purchased software
Property and Equipment
Property and equipment, gross	142	142
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 2,084	$ 2,084

Balance Sheet Components - Accr

Balance Sheet Components - Accrued and Other Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accrued and Other Liabilities
Accrued clinical trial expense	$ 2,934	$ 4,010
Accrued manufacturing expense	3,254	839
Personnel related	1,113	1,846
Accrued legal and accounting	89	265
Other	158	121
Total of accrued and other liabilities	7,548	7,081
Depreciation expense	$ 400	$ 500	$ 600

Common Stock (Details)

Common Stock (Details)	1 Months Ended		12 Months Ended
	Nov. 30, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2022 USD ($) Vote shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 shares
Common Stock
Common stock, shares authorized for issuance			290,000,000	290,000,000
Preferred stock, shares authorized for issuance			10,000,000	10,000,000
Number of votes per share of common stock | Vote			1
Dividends on common stock | $			$ 0
Proceeds from sale of stock | $				$ 31,989,000
Shares of common stock reserved for issuance, on an as-converted basis
Exchange Warrants					1,458,000
Shares available for future option grants			4,017,011	2,806,953	1,692,753
Outstanding options			7,006,250	6,354,308	6,664,173
Shares reserved for employee stock purchase plan			400,000	400,000	400,000
Total			11,423,261	9,561,261	10,214,926
2020 Sales Agreement
Common Stock
Common stock shares sold			6,920,339
Common stock gross proceeds | $			$ 31,100,000
Common stock remained available for sale | $			18,900,000
2021 sales agreement
Common Stock
Common stock remained available for sale | $			$ 40,000,000
At-the-market offering | Cowen | 2020 Sales Agreement | Maximum
Common Stock
Potential gross proceeds | $		$ 50,000,000
At-the-market offering | Cowen | 2021 sales agreement | Maximum
Common Stock
Potential gross proceeds | $	$ 40,000,000
Stock issuance costs, as a percent of gross proceeds	3%

Stock Option Plans - Stock Opti

Stock Option Plans - Stock Option Activity (Details) - $ / shares	1 Months Ended		12 Months Ended
	Mar. 31, 2016	Feb. 28, 2014	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock Option Plans
Shares available for future option grants			4,017,011	2,806,953	1,692,753
Weighted average grant date fair value of options granted (in dollars per share)			$ 0.69	$ 1.93	$ 2.66
Shares Available for Grant
Beginning balance			2,806,953	1,692,753
Ending balance			4,017,011	2,806,953	1,692,753
Number of Options
Beginning balance			6,354,308	6,664,173
Ending balance			7,006,250	6,354,308	6,664,173
2014 Plan
Stock Option Plans
Vesting period		4 years
Maximum exercise term		10 years
Exercise price of common stock of its fair value (as a percent)		100%
Shares available for future option grants	0
Maximum number of options that may be re-issued under the 2016 plan	1,136,229
Shares Available for Grant
Ending balance	0
2016 Plan
Stock Option Plans
Vesting period	4 years
Maximum exercise term	10 years
Exercise price of common stock of its fair value (as a percent)	100%
Shares available for future option grants			4,017,011	2,806,953
Shares Available for Grant
Beginning balance			2,806,953
Additional shares authorized			1,862,000
Granted			(1,706,400)
Forfeited			1,054,458
Ending balance			4,017,011	2,806,953
Number of Options
Beginning balance			6,354,308
Granted			1,706,400
Forfeited			(1,054,458)
Ending balance			7,006,250	6,354,308
Weighted-Average Exercise Price
Beginning balance (in dollars per share)			$ 6.80
Granted (in dollars per share)			1.02
Forfeited (in dollars per share)			7.75
Ending balance (in dollars per share)			$ 5.25	$ 6.80

Stock Option Plan - Vested or E

Stock Option Plan - Vested or Expected to Vest (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options outstanding and exercisable
Vested, Number of Shares (in shares)	4,121,317
Vested, Weighted Average Exercise Price (in dollars per share)	$ 7.51
Vested, Weighted Average Remaining Contractual Life	5 years 11 months 12 days
Vested, Aggregate Intrinsic Value	$ 1,995
Expected to vest, Number of Shares (in shares)	2,884,933
Expected to vest, Weighted Average Exercise Price (in dollars per share)	$ 2.02
Expected to vest, Weighted Average Remaining Contractual Life	8 years 11 months 8 days
Fair value of common stock (in dollars per share)	$ 0.85
Aggregate intrinsic value of stock options exercised	$ 0	$ 1,000	$ 300
Fair value of options vested	$ 2,800	$ 4,500	$ 6,000

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock-based compensation
Stock-based compensation expense	$ 2,692	$ 4,232	$ 5,747
Research and development
Stock-based compensation
Stock-based compensation expense	1,039	2,161	2,791
General and administrative
Stock-based compensation
Stock-based compensation expense	$ 1,653	$ 2,071	$ 2,956

Stock Based Compensation -Valua

Stock Based Compensation -Valuation Assumptions Employees (Details) - Employee stock options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Weighted-average assumptions used to estimate fair value of share-based awards
Risk-free interest rate	3%	0.90%	0.50%
Expected volatility	83.80%	86.70%	82.70%
Expected term (in years)	5 years 6 months	6 years	6 years
Expected dividend yield	0%	0%	0%
Unrecognized compensation expense	$ 3.9	$ 5.9	$ 10.4
Expected period for recognizing compensation expense	2 years 5 months 8 days	2 years 8 months 8 days	2 years 9 months 10 days

Income Taxes - Components of lo

Income Taxes - Components of loss before income tax and Income tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Income tax benefits	$ 0	$ 0	$ 0
Components of loss before income tax
Domestic	(41,307)	(43,241)	(5,995)
Total	$ (41,307)	$ (43,241)	$ (5,995)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of effective tax rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of the effective tax rate to the U.S. Federal statutory rate
Federal tax benefit at statutory rate	21%	21%	21%
State tax, net of Federal benefit	8%	9%	14%
Change in valuation allowance	(22.00%)	(26.00%)	(24.00%)
Research and development tax credits	2%	3%	19%
Share based Compensation	(1.00%)	(1.00%)	(10.00%)
162(m) covered employees compensation limitation			(6.00%)
FIN48 Reserve		(1.00%)	(161.00%)
Deconsolidation gain	(7.00%)	(3.00%)	174%
Gain on transfer of intellectual property			(20.00%)
Prior year federal true-up		(1.00%)	(7.00%)
Other	(1.00%)	(1.00%)
Effective income tax rate	0%	0%	0%

Income Taxes - Deferred tax ass

Income Taxes - Deferred tax assets net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 56,030	$ 52,539	$ 42,344
Tax credit carryforwards	9,888	9,181	7,894
Capitalized tax assets	155	125	63
Accruals	124	137	207
Stock compensation	5,487	5,006	4,942
Operating lease liability	728	1,021	646
IRC 174 capitalization	4,518
Other	21	12	47
Total deferred tax assets	76,951	68,021	56,143
Deferred tax liabilities
Operating lease right-of-use asset	(620)	(893)	(461)
Valuation allowance	(76,331)	(67,128)	(55,682)
Net deferred tax assets	0	0	$ 0
Increase in valuation allowance	$ 9,200	$ 11,400

Income Taxes - Operating loss c

Income Taxes - Operating loss carryforwards (Details) $ in Millions	Dec. 31, 2022 USD ($)
Federal
Net operating loss carryforwards
NOL carryforwards	$ 219.7
NOL carryforwards not subject to expiration	155.3
State
Net operating loss carryforwards
NOL carryforwards	$ 274.9

Income Taxes - Tax credit carry

Income Taxes - Tax credit carry forwards and of Investments in Foreign Subsidiaries (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Tax credit carryforwards
Unrecognized U.S. income and foreign withholding taxes		$ 21.9
Research and development credits | Federal
Tax credit carryforwards
Tax credit carryforwards	$ 8.6
Research and development credits | State
Tax credit carryforwards
Tax credit carryforwards	$ 4.7

Income Taxes - Unrecognized tax

Income Taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022
Summary of unrecognized tax benefits
Unrecognized tax benefits beginning of the period	$ 12,504	$ 12,157	$ 1,885	$ 1,885
Increased related to the current year	216	347	10,272
Unrecognized tax benefits, end of the period	12,720	12,504	12,157	12,720
Income tax - accrual for interest or penalties	0	$ 0	$ 0	0
Unrecognized tax benefits that would impact effective tax rate	$ 0			0
Income tax examination for federal or state				$ 0

Facility Lease - Lessee informa

Facility Lease - Lessee information (Details) $ in Thousands	1 Months Ended	12 Months Ended			80 Months Ended
	Sep. 30, 2021 USD ($) ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) ft²	Feb. 01, 2015 ft²
Lease
Area of leased facility | ft²	27,280				27,280	8,138
Lease term						1 year
Landlord Provided Free Rent And Lease Incentives					$ 1,900
Lease extension period	2 years				2 years
Increase in operating lease right-of-use asset	$ 2,400	$ 973	$ (1,542)	$ 679
Increase in the operating lease liability	$ 2,400	1,046	(1,337)	$ 878
Operating lease right-of-use asset		$ 2,217	$ 3,190

Facility Lease - Lease cost (De

Facility Lease - Lease cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating lease cost
Operating lease costs	$ 1,051	$ 1,046	$ 957
Costs of non-lease components (previously common area maintenance)	351	396	351
Total operating lease cost	1,402	1,442	1,308
Other Information
Operating cash flows used for operating lease	$ 1,695	$ 1,645	$ 1,506
Remaining lease term	2 years 1 month 6 days	3 years 1 month 6 days	2 years 1 month 6 days
Discount rate	8%	8%	10%

Facility Lease - Minimum rental

Facility Lease - Minimum rental commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Year Ended December 31, 2022
Minimum rental commitments 2022
2023	$ 1,391
2024	1,434
Total lease payments	2,825
Less: imputed interest	(224)
Total	2,601
Minimum rental commitments 2021
2022	1,391
2023	1,434
Total lease payments	2,825
Less: imputed interest	(224)
Total	$ 2,601
Year Ended December 31, 2021
Minimum rental commitments 2022
2023		$ 1,300
2024		1,391
Total lease payments		4,125
Less: imputed interest		(478)
Total		3,647
Minimum rental commitments 2021
2022		1,300
2023		1,391
2024		1,434
Total lease payments		4,125
Less: imputed interest		(478)
Total		$ 3,647

Facility Lease - Additional inf

Facility Lease - Additional information (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2021 ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Facility Lease
Area of property subleased | ft²	7,585
Sublease income - related party | $		$ 587	$ 235

Commitments and Contingencies -

Commitments and Contingencies - Line of Credit (Details) $ in Millions	Aug. 31, 2015 USD ($)
Line of credit
Security deposit	$ 0.1
Secured debt
Line of credit
Line of credit	$ 0.1

Related Party Transactions (Det

Related Party Transactions (Details)		1 Months Ended				12 Months Ended
	Apr. 26, 2016 $ / shares shares	Sep. 30, 2021 shares	Aug. 31, 2021 ft²	Feb. 28, 2021 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Oct. 31, 2020
Public Offerings
Issuance of common stock | shares		1,457,947
Proceeds from sale of stock							$ 31,989,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Area of property subleased | ft²			7,585
Sublease income - related party						$ 587,000	235,000
Angel Pharmaceuticals
Related Party Transactions
Clinical drug supplies						200,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Internal personnel costs						100,000	200,000
Third-party costs						1,300,000	1,600,000
Third-party costs expensed in prior years						500,000	600,000
Third-party costs expensed in current years						800,000	1,000,000
Sublease income - related party						600,000	200,000
ICON plc
Owners of More Than 5% of Our Common Stock or Board of Directors
Clinical trial expense						$ 429,000	$ 246,000
Follow-on Public Offering
Public Offerings
Issuance of common stock | shares				9,783,660	8,117,647
Share offering price | $ / shares				$ 3.50	$ 8.50
Proceeds from sale of stock				$ 32,000,000	$ 64,900,000
Follow-on Public Offering | Orbimed Advisors LLC
Public Offerings
Issuance of common stock | shares				1,285,714
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price				$ 4,499,999
Follow-on Public Offering | Richard A. Miller, M.D.
Public Offerings
Issuance of common stock | shares				100,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price				$ 350,000
Over-Allotment Option
Public Offerings
Issuance of common stock | shares	502,618			1,212,231	1,058,823
Share offering price | $ / shares	$ 15
Angel Pharmaceuticals
Related Party Transactions
Ownership interest (as percent)						49.70%		53.20%