TRACON Pharmaceuticals (TCON) 10-K 8 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 03, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	TRACON Pharmaceuticals, Inc.
Entity Central Index Key	0001394319
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 42.2
Entity Common Stock, Shares Outstanding		23,822,542
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	TCON
Security Exchange Name	NASDAQ
Entity File Number	001-36818
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	34-2037594
Entity Address, Address Line One	4350 La Jolla Village Drive
Entity Address, Address Line Two	Suite 800
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92122
City Area Code	858
Local Phone Number	550-0780
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	San Diego, California
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant’s definitive proxy statement for its 2023 Annual Meeting of Stockholders, which the Registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the Registrant’s fiscal year ended December 31, 2022, are incorporated by reference into Part III of this Annual Report on Form 10-K .

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 17,433	$ 24,072
Prepaid and other assets	795	864
Total current assets	18,228	24,936
Property and equipment, net	51	50
Restricted cash	67
Other assets	1,123	1,571
Total assets	19,469	26,557
Current liabilities:
Accounts payable and accrued expenses	11,107	10,753
Accrued compensation and related expenses	1,457	1,532
Long-term debt, current portion	9,807	1,391
Total current liabilities	22,371	13,676
Other long-term liabilities	969	1,167
Arbitration financing payable	3,280
Commitments and contingencies (Note 5)
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value, authorized shares — 10,000,000 at December 31, 2022 and December 31, 2021; issued and outstanding shares — none
Common stock, $0.001 par value; authorized shares — 40,000,000 at December 31, 2022 and December 31, 2021; issued and outstanding shares — 23,125,250 and 19,445,903 at December 31, 2022 and December 31, 2021, respectively	23	19
Additional paid-in capital	229,737	219,471
Accumulated deficit	(236,911)	(207,776)
Total stockholders’ (deficit) equity	(7,151)	11,714
Total liabilities and stockholders’ equity (deficit)	$ 19,469	$ 26,557

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Statement Of Financial Position [Abstract]
Preferred Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	23,125,250	19,445,903
Common stock, shares outstanding	23,125,250	19,445,903

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
License revenue	$ 0	$ 346	$ 0
Type of Revenue [Extensible List]	License revenue	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 13,888	$ 11,146	$ 8,198
General and administrative	14,006	17,547	8,025
Total operating expenses	27,894	28,693	16,223
Loss from operations	(27,894)	(28,347)	(16,223)
Other expense:
Interest expense, net	(994)	(318)	(545)
Other expense	(247)	(2)	(7)
Total other expense	(1,241)	(320)	(552)
Net loss	$ (29,135)	$ (28,667)	$ (16,775)
Net loss per share, basic	$ (1.39)	$ (1.66)	$ (1.87)
Net loss per share, diluted	$ (1.39)	$ (1.66)	$ (1.87)
Weighted-average shares outstanding, basic	20,919,118	17,252,637	8,984,148
Weighted-average shares outstanding diluted	20,919,118	17,252,637	8,984,148

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2019	$ 2,698	$ 4	$ 165,028	$ (162,334)
Balance (in Shares) at Dec. 31, 2019		4,051,187
Increase (Decrease) in Shareholders' Equity
Issuance of common stock under equity plans	2		2
Issuance of common stock under equity plans (in shares)		6,628
Stock-based compensation expense	1,034		1,034
Issuance of common stock and warrants, net of offering costs	37,987	$ 11	37,976
Issuances of Common Stock and Warrants Net of Offering Costs (in shares)		11,320,972
Issuance of common stock in exchange for services	126		126
Issuance of common stock in exchange for services (in shares)		100,000
Net loss	(16,775)			(16,775)
Balance at Dec. 31, 2020	25,072	$ 15	204,166	(179,109)
Balance (in Shares) at Dec. 31, 2020		15,478,787
Increase (Decrease) in Shareholders' Equity
Issuance of common stock under equity plans	149		149
Issuance of common stock under equity plans (in shares)		40,414
Stock-based compensation expense	1,775		1,775
Net loss	(28,667)			(28,667)
Balance at Dec. 31, 2021	11,714	$ 19	219,471	(207,776)
Balance (in Shares) at Dec. 31, 2021		19,445,903
Increase (Decrease) in Shareholders' Equity
Issuance of common stock, net of offering costs	13,385	$ 4	13,381
Issuances of common stock, net of offering costs (in shares)		3,926,702
Issuance of common stock under equity plans	95		95
Issuance of common stock under equity plans (in shares)		56,261
Stock-based compensation expense	2,041		2,041
Issuance of common stock and warrants, net of offering costs	7,874	$ 3	7,871
Issuances of Common Stock and Warrants Net of Offering Costs (in shares)		3,232,418
Issuances Of Common Stock Upon Cashless Exercise Of Pre Funded Warrants Value	1	$ 1
Net loss	(29,135)			(29,135)
Balance at Dec. 31, 2022	(7,151)	$ 23	229,737	$ (236,911)
Balance (in Shares) at Dec. 31, 2022		23,125,250
Increase (Decrease) in Shareholders' Equity
Issuance of common stock upon cashless exercise of pre-funded warrants, shares		390,668
Issuance of common stock warrants in connection with debt financing	$ 259		$ 259

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	$ (29,135)	$ (28,667)	$ (16,775)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,041	1,775	1,034
Common stock issued for services			126
Depreciation and amortization	16	14	12
Noncash interest	343	61	123
Amortization of debt discount	435	21	43
Amortization of premium/discount on short-term investments		(1)	(1)
Lease asset amortization and liability accretion, net	54	(73)	(25)
Equity ownership license revenue		(246)
Impairment of private company equity ownership	246
Changes in assets and liabilities:
Prepaid expenses and other assets	69	(80)	64
Accounts payable and accrued expenses	(233)	4,683	(1,878)
Accrued compensation and related expenses	(75)	(58)	235
Net cash used in operating activities	(26,239)	(22,571)	(17,042)
Cash flows from investing activities
Purchase of property and equipment	(17)	(48)	(5)
Purchases of available-for-sale short-term investments			(3,998)
Proceeds from the maturity of available-for-sale short-term investments		4,000
Net cash (used in) provided by investing activities	(17)	3,952	(4,003)
Cash flows from financing activities
Proceeds from long-term debt	9,960
Proceeds from arbitration financing	3,430
Repayment of long-term debt	(1,680)	(2,800)	(1,400)
Proceeds from sale of common stock and warrants, net of offering costs	7,879	13,211	38,162
Proceeds from issuance of common stock under equity plans, net of tax withholdings	95	149	2
Net cash provided by financing activities	19,684	10,560	36,764
Change in cash, cash equivalents, and restricted cash	(6,572)	(8,059)	15,719
Cash, cash equivalents, and restricted cash at beginning of period	24,072	32,131	16,412
Cash, cash equivalents, and restricted cash at end of period	17,500	24,072	32,131
Supplemental disclosure of cash flow information
Interest paid	359	$ 266	$ 443
Supplemental schedule of noncash investing and financing activities
Issuance of common stock warrants in connection with long-term debt	$ 259

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Organization And Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies Organization and Business TRACON Pharmaceuticals, Inc. (TRACON or the Company) was incorporated in the state of Delaware on October 28, 2004. TRACON is a biopharmaceutical company focused on the development and commercialization of novel targeted therapeutics for cancer, and utilizes its cost efficient, contract research organization (CRO) independent product development platform to partner with other life science companies to develop and commercialize innovative products in the United States. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, TRACON Pharma Limited and TRACON Pharma International Limited, which were formed in September 2015 and January 2019, respectively, and are currently inactive. All significant intercompany accounts and transactions have been eliminated. Basis of Presentation As of December 31, 2022, the Company has devoted substantially all its efforts to product development, raising capital, and building infrastructure and has not realized revenues from its planned principal operations. The Company has incurred operating losses since inception. As of December 31, 2022, the Company had an accumulated deficit of $236.9 million. The Company anticipates that it will continue to incur net losses into the foreseeable future as it continues the development and commercialization of its product candidates and works to develop additional product candidates through research and development programs. At December 31, 2022, the Company had cash and cash equivalents of $17.5 million, of which $0.1 million is classified as restricted cash as it is pledged as collateral for the Company’s obligations under its corporate headquarters facility lease. Based on the Company’s current business plan, management believes that there is substantial doubt as to whether existing cash and cash equivalents will be sufficient to meet its obligations as they become due within twelve months from the date the consolidated consolidated The Company plans to continue to fund its losses from operations through its existing cash and cash equivalents, as well as through future equity offerings, debt financings, other third-party funding, and potential licensing or collaboration arrangements. In addition, the Company may fund its losses from operations through the Capital on Demand TM Risks and Uncertainties COVID-19, a novel strain of coronavirus (together with its variants, COVID-19), has become a global pandemic. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world. While vaccines have become widely available in certain countries, and businesses and economies have reopened, the status of global economic recovery remains uncertain and unpredictable, and will continue to be impacted by developments in the pandemic including any subsequent waves of outbreak or new variant strains of the COVID-19 virus which may require re-closures or other preventative measures. The COVID-19 pandemic may also have long-term effects on the nature of the office environment and remote working, which may present risks for the Company’s strategy, operational, talent recruiting and retention, and workplace culture. In addition to the ongoing COVID-19 pandemic, global economic and business activities continue to face widespread macroeconomic uncertainties, including labor shortages, inflation and monetary supply shifts, recession risks and potential disruptions from the Russia-Ukraine conflict. The Company continues to actively monitor the impact of these macroeconomic factors on its financial condition, liquidity, operations, and workforce. The extent of the impact of these factors on the Company’s operational and financial performance, including its ability to execute its business strategies and initiatives in the expected time frame, will depend on future developments, which are uncertain and cannot be predicted; however, any continued or renewed disruption resulting from these factors could negatively impact the Company’s business . Use of Estimates The Company’s consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States (GAAP). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenue, and expenses. The most significant estimates in the Company’s consolidated Restricted Cash Restricted cash consists of money market funds held by the Company’s financial institution as collateral for the Company’s obligations under its facility lease for the Company’s corporate headquarters in San Diego, California. Cash and Cash Equivalents Cash and cash equivalents consist of cash and highly liquid investments with original maturities of three months or less at the date of purchase. The carrying amounts approximate fair value due to the short maturities of these investments. Cash and cash equivalents include cash in readily available checking and money market funds. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Property and Equipment Property and equipment is stated at cost and depreciated using the straight-line method over the estimated useful life of the related assets, which is generally five years. Leasehold improvements are amortized over the shorter of the lease term or estimated useful life of the related assets. Repairs and maintenance costs are charged to expense as incurred. Leases The Company determines if an arrangement contains a lease at inception. For arrangements where the Company is the lessee, operating leases are recorded as other assets, accounts payable and accrued expenses, and other long-term liabilities within the consolidated balance sheet. The Company currently does not have any finance leases. Operating lease right-of-use (ROU) assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. ROU assets also include any initial direct costs incurred and any lease payments made at or before the lease commencement date, less lease incentives received. The Company uses its incremental borrowing rate based on the information available at the commencement date in determining the lease liabilities as the Company’s leases generally do not provide an implicit rate. Lease terms may include options to extend or terminate when the Company is reasonably certain that the option will be exercised. Lease expense is recognized on a straight-line basis over the lease term. Revenue Recognition To date, substantially all the Company’s revenue has been derived from license agreements. The terms of these arrangements included payments to the Company for the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. In accordance with Accounting Standards Codification 606, Revenue from Contracts with Customers . As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of each arrangement that includes development, commercialization, and regulatory milestone payments, the Company evaluates whether the achievement of the milestones is considered probable and estimates the amount to be included in the transaction price using the most likely amount method. Performance milestone payments represent a form of variable consideration. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Achievement of milestones that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable until the approvals are achieved. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis and the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achieving such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations at the outset of the arrangement. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its out-licensing arrangements. The Company receives payments from its collaborators based on billing schedules established in each contract. Up-front and other payments may require deferral of revenue recognition to a future period until the Company performs its obligations under its collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. Clinical Trial Expense Accruals As part of the process of preparing the Company’s financial statements, the Company is required to estimate expenses resulting from its obligations The Company’s objective is to reflect the appropriate trial expenses in its consolidated financial statements by recording those expenses in the period in which services are performed and efforts are expended. The Company accounts for these expenses according to the progress of the clinical trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through discussion with the clinical sites and applicable personnel and outside service providers as to the progress or state of consummation of trials. During a clinical trial, the Company adjusts the clinical expense recognition if actual results differ from its estimates. The Company makes estimates of accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. The Company’s clinical trial accruals are dependent upon accurate reporting by clinical sites and other third-party vendors. Although the Company does not expect its estimates to differ materially from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For each of the three years in the period ended December 31, 2022, there were no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. Research and Development Costs Research and development costs, including license fees, are expensed as incurred. Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain. Stock-Based Compensation Stock-based compensation expense represents the grant date fair value of employee stock option grants, employee restricted stock unit grants (RSUs), and employee stock purchase plan (ESPP) rights recognized as expense over the requisite service period of the awards (usually the vesting period) on a straight-line basis. The Company estimates the fair value of stock option grants and ESPP rights using the Black-Scholes option pricing model. The fair value of RSUs is based on the closing sales price for such stock on the date of grant. Equity award forfeitures are recorded as they occur. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the consolidated The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than‑not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability. Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Net loss and comprehensive loss were the same for all periods presented. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average shares of common stock outstanding for the period, without consideration for common stock equivalents and adjusted for the weighted average number of shares of common stock outstanding that are subject to repurchase. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): December 31, 2022 2021 2020 Warrants to purchase common stock 6,766,246 4,810,409 4,810,409 Common stock options 2,246,310 1,308,360 601,481 ESPP shares 3,387 3,258 5,349 9,015,943 6,122,027 5,417,239 Segment Reporting 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.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	2. Financial Instruments and Fair Value Measurements Cash equivalents, which are classified as equity securities, and restricted cash consisted of the following (in thousands): December 31, 2022 December 31, 2021 Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Money market funds $ 10,150 $ — $ — $ 10,150 $ 5,003 $ — $ — $ 5,003 Equity securities (1) — — — — 246 — — 246 $ 10,150 $ — $ — $ 10,150 $ 5,249 $ — $ — $ 5,249 Classified as: Cash equivalents $ 10,083 $ 5,003 Restricted cash 67 — Other assets — 246 Total cash equivalents, restricted cash, and other assets $ 10,150 $ 5,249 (1) The Company had no short-term investments at December 31, 2022 and 2021. The Company classifies all investments as available-for-sale securities, as the sale of such investments may be required prior to maturity to implement management strategies. These investments are carried at amortized cost which approximates fair value. A decline in the market value of any short-term investment below cost that is determined to be other-than-temporary will result in a revaluation of its carrying amount to fair value. The impairment is charged to earnings and a new cost basis for the security is established. No such impairment charges were recorded for any period presented. Realized gains and losses from the sale of short-term investments, if any, are determined on a specific identification basis. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense on the consolidated statements of operations. Realized and unrealized gains and losses during the periods presented were immaterial. Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the straight-line method and are included in interest income on the consolidated statements of operations. Interest and dividends on securities classified as available-for-sale are included in interest income on the consolidated statements of operations. The carrying amounts of cash and cash equivalents, prepaid and other assets, accounts payable and accrued liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on the borrowing rates currently available to the Company for loans with similar terms, which is considered a Level 2 input, the Company believes that the fair value of long-term debt approximates its carrying value. The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. None of the Company’s non-financial assets or liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented. The fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Significant Active Markets Other Significant for Identical Observable Unobservable Assets Inputs Inputs Total (Level 1) (Level 2) (Level 3) At December 31, 2022 Money market funds $ 10,150 $ — $ 10,150 $ — At December 31, 2021 Money market funds $ 5,003 $ — $ 5,003 $ —

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	3. Balance Sheet Details Property and Equipment Property and equipment consisted of the following (in thousands): December 31, 2022 2021 Computer and office equipment $ 203 $ 186 Furniture and fixtures 19 19 Leasehold improvements 21 21 243 226 Less accumulated depreciation and amortization (192 ) (176 ) $ 51 $ 50 Depreciation expense related to property and equipment totaled approximately $16,000, $14,000 and $12,000 for the years ended December 31, 2022, 2021 and 2020, respectively. Accounts payable and accrued expenses Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2022 2021 Accounts payable $ 3,923 $ 4,943 Accrued clinical related expenses 6,091 4,461 Accrued legal and accounting 299 842 Accrued long-term debt terminal interest 425 280 Current portion of operating lease liability 198 147 Other accruals 171 80 $ 11,107 $ 10,753

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2022
Debt Disclosure [Abstract]
Long-Term Debt	4. Long-Term Debt Arbitration Financing Investment Agreement In December 2022, the Company entered into a non-recourse financing agreement (the Investment Agreement) with certain investors (collectively the Investors) pursuant to which the Investors will pay the Company a maximum aggregate amount (Maximum Capital) equal to $30.0 million or a lesser amount based on the amount awarded (Award), if any, to the Company in connection with its ongoing arbitration proceeding (the Arbitration) with I-Mab Biopharma (I-Mab). Of the Maximum Capital, (i) $3.5 million (Initial Capital) was paid to the Company shortly after execution, (ii) 25% will be paid to the Company within 15 business days of issuance of an Award, subject to the Award size exceeding a prespecified threshold and satisfaction of other conditions set forth in the Investment Agreement, and (iii) the remainder will be paid to the Company in tranches over a multi-year period, subject to the issuance of an Award and the Award size exceeding a prespecified threshold and satisfaction of other conditions set forth in the Investment Agreement. In connection with the execution of the Investment Agreement and funding of the Initial Capital amount, the Company paid a closing fee in the amount of 2%. Subject to and contingent on the Company’s actual recovery of proceeds from an Award or any contemporaneously resolved settlements with I-Mab and following the payment of applicable attorney’s fees (the Proceeds), the Company shall pay the Investors an amount (Repayment Amount) equal to the sum of (i) all amounts paid by the Investors to or on behalf of the Company pursuant to the Investment Agreement, plus (ii) a low sub-single digit to low single digit multiple calculated on each tranche of Maximum Capital actually paid by the Investors to or on behalf of the Company with the applicable multiple being based on the timing of payment from the Company and whether certain events relating to the Arbitration occur, plus (iii) a mid-teen percentage annual rate of return on the amounts set forth in clauses (i) and (ii) that begins to accrue if the amounts are not paid by the Company to the Investors within a multi-month period specified in the Investment Agreement. If the amount of Proceeds are less than the Repayment Amount, then the Company shall only be required to pay to the Investors the Proceeds recovered (other than in circumstances in which the Company accepts a settlement offer that resolves the Arbitration for an amount less than the Repayment Amount without the prior written consent of the Investors), and in the circumstance in which there are no Proceeds then the Company shall not be required to pay the Investors any Repayment Amounts and the Investors shall have no right of recourse or right of action against the Company. The Investment Agreement contains customary representations, warranties and covenants and also includes customary events of default, including payment defaults, breaches of representations or covenants and a bankruptcy default. The Investment Agreement also contains customary covenants that require the Company to, among other things, (i) use commercially reasonable efforts to pursue its claims in connection with the Arbitration and recover amounts awarded to it in connection with an Award, (ii) pay costs and expenses in connection with enforcing an Award, (iii) keep the Investors informed regarding the Arbitration and its collection and enforcement efforts and (iv) not incur liens (other than permitted liens) on or transfer any portion of its assets related to its claims in connection with the Arbitration, any Award, the Proceeds and related assets. The Company may terminate the obligation of the Investors to pay all or certain tranches of the Maximum Capital by providing advance written notice to the Investors as set forth in the Investment Agreement. If the Company fails to pay amounts owed to the Investors when due, such overdue amounts bear interest at a default rate set forth in the Investment Agreement. Upon certain remedy events, including the Company’s breach of the Investment Agreement, the Investors may exercise all of their rights and remedies as set forth in the Investment Agreement and under applicable law, including, without limitation, termination of their obligations to pay additional amounts under the Investment Agreement. Pursuant to the Investment Agreement, the Company will also grant to the Investors a security interest in its interest in its claims in connection with the Arbitration, any Award, the Proceeds and related assets (Specific Collateral), as further described in the Investment Agreement, as security for the payment of the Company’s obligations under the Investment Agreement. In December 2022, the Investors funded the Initial Capital amount of $3.5 million which was recorded as arbitration financing payable on the consolidated balance sheet. The carrying amount of the arbitration financing payable recorded on the consolidated balance sheet is net of debt discount, including the Initial Capital closing fee, which is being amortized over the estimated term of the agreement using the effective interest method. Pursuant to the terms of the Investment Agreement, repayment of all capital amounts funded under the Investment Agreement, including the Initial Capital, and the obligation amount owed is contingent upon the Company’s actual recovery of proceeds from an Award, which is uncertain. Accordingly, as of December 31, 2022, the Company has estimated an effective interest rate and term of the agreement over which the related debt discount is being amortized. The Company will re-evaluate this estimate at the end of each subsequent reporting period, with any material changes recorded prospectively using a new effective interest rate based on the updated estimate of the amount of arbitration financing payable owed as of the end of the reporting period. In the event in which there is no recovery of proceeds from an Award, the Company is not required to repay the $3.5 million Initial Capital. As of December 31, 2022, the arbitration financing payable was classified as long-term liabilities as it is considered unlikely the obligation amount owed under the Investment Agreement will be settled prior to December 31, 2023. Runway Growth Finance Corp. Loan and Security Agreement In September 2022, the Company entered into a loan and security agreement (the RGC Loan Agreement). with Runway Growth Finance Corp. (RGC). The RGC Loan Agreement is a long-term debt facility that provides a term loan commitment in an aggregate principal amount of up to $35.0 million in three Borrowings under the term loan facility bear interest at a variable annual rate equal to the sum of (i) the greater of (a) the rate of interest noted in The Wall Street Journal, Money Rates section, as the “Prime Rate” or (b) 3.5%, plus (ii) 5.0%. The Company is obligated to make interest-only payments monthly in arrears through and including September 30, 2024 and thereafter monthly payments in arrears through the maturity date of September 1, 2026 equal to 1/24 th The Company is obligated to pay a closing fee in the amount of (i) $50,000, which was paid upon the funding of the Term A loan, and (ii) an amount equal to 0.50% of the Term B loan and the Term C loan advanced to the Company, if any, due and payable on the applicable funding date of such Term B loan and Term C loan. The Company is also obligated to pay a final payment fee equal to 4.25% of the aggregate principal amount of the funded term loans at the earlier to occur of (i) the maturity date, (ii) acceleration of the term loans and (iii) prepayment under the RGC Loan Agreement. The closing fee, other related debt issuance costs, and the final payment fee were recorded as a component of the total debt discount and will be recognized as interest expense over the term of the RGC Loan Agreement using the effective interest method. The Company has the option to prepay all, but not less than all, of the amounts of outstanding principal, accrued and unpaid interest and any other amounts due and payable under the RGC Loan Agreement, including a final payment fee. If the Company exercises its right to prepay the term loan(s) prior to the maturity date, it is obligated to pay a prepayment fee equal to (a) 3.0% of the outstanding principal amount of the applicable term loan(s) prepaid at the time of such prepayment if it occurs on or prior to the first anniversary date, (b) 2.0% of the outstanding principal amount of the applicable term loan(s) prepaid at the time of such prepayment if it occurs after the first anniversary date but on or prior to the second anniversary date and (c) 1.0% of the outstanding principal amount of the applicable term loan(s) prepaid at the time of such prepayment if it occurs after the second anniversary date but prior to the maturity date. The Company’s obligations under the RGC Loan Agreement are collateralized by a first priority security interest in substantially all of its assets other than the intellectual property of the Company and for S pecific C ollateral that is subordinated to the arbitration financing Investors’ security interest. The RGC Loan Agreement also contains customary representations, warranties and covenants that limit, among other things, the ability of the Company to (i) incur indebtedness, (ii) incur liens on its property, (iii) pay dividends or make other distributions, (iv) sell its assets, (v) make certain loans or investments, (vi) merge or consolidate, (vii) voluntarily repay or prepay certain indebtedness and (viii) enter into transactions with affiliates, in each case subject to certain exceptions. Upon the occurrence and during the continuance of an event of default, a default interest rate of an additional 5.0 % per annum may be applied to the outstanding loan balances, and the lender may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the RGC Loan Agreement and under applicable law, including, without limitation, termination of its obligations to extend credit to the Company. The RGC Loan Agreement contains customary representations, warranties and covenants, including financial covenants, and also includes customary events of default, including payment defaults, breaches of covenants, change in control and a material adverse effect default. As of December 31, 2022 , the Company was in compliance with all covenants and conditions of the RGC Loan Agreement. In connection with the funding of the Term A loan, the Company issued Runway Growth Finance Corp. warrants to purchase 150,753 shares of its common stock (the RGC Term A Warrants) at an exercise price of $1.99 per underlying share of the Company’s common stock. The RGC Term A Warrants are fully exercisable in whole or in part at the option of the holder, payable in cash or on a cashless basis according to the formula set forth in the RGC Term A Warrants, and expire September 2, 2032. The fair value of the warrant at the grant date was determined utilizing a Black-Scholes pricing model, recorded as a component of the total debt discount and stockholders’ equity (deficit) within additional paid-in capital on the consolidated balance sheets, and will be amortized to interest expense using the effective interest method over the term of the debt. Long-term debt and unamortized debt discount balances associated with the RGC Loan Agreement entered into in 2022 were as follows (in thousands): December 31, 2022 Long-term debt $ 10,000 Less debt discount, net of current portion — Long-term debt, net of debt discount 10,000 Less current portion of long-term debt (10,000 ) Long-term debt, net of current portion $ — Current portion of long-term debt $ 10,000 Current portion of debt discount (193 ) Current portion of long-term debt, net $ 9,807 As of December 31, 2022, future minimum principal and interest payments, including the final payment, under the RGC Loan Agreement are as follows (in thousands): 2023 $ 10,491 10,491 Less interest and final payment (491 ) Long-term debt $ 10,000 Silicon Valley Bank Loan and Security Agreement In May 2018, the Company entered into a third amendment to its Amended and Restated Loan and Security Agreement with Silicon Valley Bank (the 2018 Amended SVB Loan) under which the Company borrowed $7.0 million, all of which was immediately used to repay the Company’s then existing loan with SVB (the 2017 Amended SVB Loan). As of December 31, 2021, the total principal amount owed under the 2018 Amended SVB Loan was $1.4 million, net of a remaining unamortized debt discount balance of $9,000. The 2018 Amended SVB Loan matured in June 2022 and in accordance with its terms, the Company paid a final payment of $0.3 million associated with the payoff of the 2018 Amended SVB Loan. In August 2022, the Company terminated the Amended and Restated Loan and Security Agreement with SVB. At December 31, 2022, the Company had the following exercisable outstanding warrants for the purchase of common stock issued in connection with the Company’s loan agreements with SVB : Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 May 3, 2025 5,363 $ 26.10 13,906

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies License Agreements The Company has entered into various license agreements pursuant to which the Company acquired licenses to certain intellectual property. The agreements generally required an upfront license fee and, in some cases, reimbursement of patent costs. Additionally, under each agreement, the Company may be required to pay annual maintenance fees, royalties, milestone payments and sublicensing fees. Each license agreement is generally cancelable by the Company, given appropriate prior written notice. At December 31, 2022, potential future milestone payments under these agreements totaled an aggregate of $9.6 million.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2022
Stockholders Equity Note [Abstract]
Stockholders' Equity	6. Stockholders’ Equity Sale of Common Stock and Pre-Funded Warrants In June 2022, the Company issued and sold 841,989 shares of its common stock at a purchase price of $1.32 per share and pre-funded warrants to purchase 2,205,018 shares of its common stock at a purchase price of $1.31 per share of underlying common stock with an exercise price of $0.01 per share of underlying common stock (the 2022 Pre-Funded Warrants) for net proceeds of approximately $3.9 million in a registered direct offering (the Offering) with an accredited institutional healthcare-focused fund. In accordance with their terms, the 2022 Pre-Funded Warrants may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99% of the shares of the Company’s common stock outstanding immediately after giving effect to such exercise. The 2022 Pre-Funded Warrants were recorded as a component of stockholders’ equity (deficit) within additional paid-in capital on the consolidated balance sheets. In connection with the Offering, the Company amended two existing pre-funded warrants to purchase shares of the Company’s common stock held by the same institutional healthcare-focused fund to extend the exercise periods and to permit exercise in excess of a similar 19.99% limit following approval of the Company’s stockholders of such exercise. In July 2021, the Company completed an underwritten public offering of 3,926,702 shares of its common stock at an offering price of $3.82 per share. The Company received net proceeds of approximately $13.4 million, after deducting underwriting discounts, commissions and offering-related expenses. At-The-Market Issuance Sales Agreement In December 2020, as amended in March 2022, the Company entered into a Capital on Demand TM Common Stock Warrants As of December 31, 2022 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 March 27, 2024 1,369,602 $ 27.00 May 3, 2025 5,363 $ 26.10 August 27, 2030 1,889,513 $ 0.01 August 31, 2030 1,137,454 $ 0.01 June 21, 2032 2,205,018 $ 0.01 September 2, 2032 150,753 $ 1.99 6,766,246 During the year ended December 31, 2022, the Company issued 390,668 shares of its common stock upon the cashless exercise of 398,093 pre-funded warrants. During the year ended December 31, 2021, no warrants were exercised. Stock Compensation Plans Effective January 1, 2015, the Company’s board of directors adopted the 2015 Equity Incentive Plan (2015 Plan). Under the 2015 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company or its subsidiaries. Initially, a total of 80,103 shares of common stock were reserved for issuance under the 2015 Plan. In addition, pursuant to the June 10, 2021 amendment, the number of shares of common stock available for issuance under the 2015 Plan will be annually increased on the first day of each fiscal year during the term of the 2015 Plan, as amended, beginning with the 2022 fiscal year until (and including) January 1, 2031, by an amount equal to 5% of the total number of shares of common stock outstanding on December 31st of the preceding calendar year or such other amount as the Company’s board of directors may determine. The maximum term of the options granted under the 2015 Plan is no more than ten years. Grants generally vest at 25% one year from the vesting commencement date and ratably each month thereafter for a period of 36 months, subject to continuous service. In addition, pursuant to a June 2021 amendment, the 2015 Plan was amended to allow an additional aggregate 200,000 shares of common stock to be used exclusively for the grant of equity awards as a material inducement for individuals to commence employment at the Company in compliance with Nasdaq Listing Rule 5635(c)(4). Stock Options Stock option activity under all Plans is summarized as follows: Weighted- Number of Average Options Exercise Price Balance at December 31, 2021 1,308,360 $ 13.99 Granted 937,950 2.20 Exercised — — Forfeited — — Balance at December 31, 2022 2,246,310 $ 9.07 Information about the Company’s outstanding stock options as of December 31, 2022 is as follows: Weighted- Average Weighted- Remaining Average Contractual Aggregate Number of Exercise Term Intrinsic Shares Price (in years) Value Options outstanding 2,246,310 $ 9.07 8.00 $ 23,168 Options vested and expected to vest 2,246,310 $ 9.07 8.00 $ 23,168 Options exercisable 860,683 $ 17.36 6.75 $ 1,480 The weighted-average grant date fair value per share of employee option grants during the years ended December 31, 2022, 2021 and 2020 was $1.65, $6.05, and $2.62, respectively. The aggregate intrinsic value used in the above table of options at December 31, 2022 is based on the Company’s closing market price per common share on December 30, 2022, the last business day of the 2022 fiscal year, of $1.49. No stock options were exercised during the year ended December 31, 2022 and 3,727 stock options were exercised during the year ended December 31, 2021 for proceeds of $21,000. The total intrinsic value of options exercised was $4,000 during the year ended December 31, 2021. The total grant-date fair value of options that vested during the years ended December 31, 2022, 2021 and 2020 was $2.6 million, $0.8 million and $1.0 million, respectively. Employee Plan (ESPP) On January 1, 2015, the Company’s board of directors adopted the ESPP, which became effective upon the pricing of the Company’s initial public offering on January 29, 2015. The ESPP permits participants to purchase common stock through payroll deductions of up to 15% of their eligible compensation. Initially, a total of 18,346 shares of common stock was reserved for issuance under the ESPP. In addition, pursuant to the June 10, 2021 amendment, the number of shares of common stock available for issuance under the ESPP will be annually increased on the first day of each fiscal year during the term of the ESPP, beginning with the 2022 fiscal year, by an amount equal to the lessor of: (i) 250,000 shares; (ii) 1% of the total number of shares of common stock outstanding on December 31st of the preceding calendar year; or (iii) such other amount as the Company’s board of directors may determine. Stock compensation expense for the years ended December 31, 2022, 2021 and 2020 related to the ESPP was immaterial. Stock-Based Compensation Expense The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows: Years Ended December 31, 2022 2021 2020 Risk-free interest rate 1.9 % 0.8 % 1.2 % Expected volatility 89.8 % 90.3 % 85.8 % Expected term (in years) 6.2 6.2 6.2 Expected dividend yield — — — Risk-free interest rate. The Company bases the risk‑free interest rate assumption on the U.S. Treasury’s rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. Expected volatility. The Company considers its historical volatility when determining the expected volatility. Expected term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historical exercise behavior, it determines the expected life assumption using the simplified method, which is an average of the contractual term of the option and its vesting period. Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends. The allocation of stock-based compensation expense was as follows (in thousands): Years Ended December 31, 2022 2021 2020 Research and development $ 830 $ 628 $ 386 General and administrative 1,211 1,147 648 $ 2,041 $ 1,775 $ 1,034 As of December 31, 2022 and 2021, the unrecognized compensation cost related to outstanding time-based options was $3.6 million and $4.0 million, respectively, and is expected to be recognized as expense over approximately 2.5 years and 2.7 years, respectively. Common Stock Reserved for Future Issuance Common stock reserved for future issuance was as follows: December 31, 2022 2021 Common stock warrants 6,766,246 4,810,409 Common stock options granted and outstanding 2,246,310 1,308,360 Awards available under the 2015 Plan 150,335 115,990 Shares available under the Employee Stock Purchase Plan 243,817 105,619 9,406,708 6,340,378

Collaboration

Collaboration	12 Months Ended
	Dec. 31, 2022
Collaborations Disclosure [Abstract]
Collaboration	7. Collaborations Eucure and Biocytogen Collaborative Development and Commercialization Agreement In October 2021, the Company, Eucure (Beijing) Biopharma Co., Ltd. (Eucure) and Biocytogen Pharmaceuticals (Beijing) Co., Ltd. (Biocytogen), Eucure’s controlling affiliate, entered into a collaborative development and commercialization agreement (the YH001 Collaboration Agreement) for the development of YH001, a monospecific investigational CTLA-4 antibody. Pursuant to the YH001 Collaboration Agreement, the Company was granted an exclusive (including with respect to Eucure and its affiliates), nontransferable, license to develop and commercialize YH001 in North America for the treatment, through administration of YH001 by intravenous or subcutaneous means, of multiple human indications, including sarcoma, microsatellite stable colorectal cancer, renal cell carcinoma (RCC), and K-ras positive non-small cell lung cancer (collectively, the Initial Indications) or one or more of bladder cancer, endometrial cancer, and melanoma as substitute indications, which may be substituted for Initial Indications at the Company’s discretion (each upon such substitution, a Substitute Indication). The Company is responsible for, and will bear the costs of, preparing and filing all regulatory submissions and conducting any Phase 1, Phase 2, Phase 3, or post-approval clinical trials in North America for YH001 in the Initial Indications and potentially the Substitute Indications, while Eucure is responsible for conducting, and will bear the costs of, the preparation of chemistry, manufacturing and controls activities for YH001. Eucure has agreed to manufacture and supply, or to arrange for a third party manufacturer to manufacture and supply, YH001 to the Company for clinical trials pursuant to the terms of a clinical supply and quality agreement to be separately negotiated. During a specified period, the Company has the option, subject to Eucure’s prior written approval, to expand the license to include the development and commercialization of YH001 for the treatment, through administration by intravenous or subcutaneous means, of all human and veterinary therapeutic indications in North America for a payment to Eucure in the low single digit millions. The Company will be responsible for commercializing YH001 in North America, including booking of sales revenue in the Initial and Substitute Indications. The Company will owe Eucure escalating double digit royalties on net sales of YH001 in North America ranging from the mid-twenties to mid-double digits; provided that until the end of the first full calendar year following the first commercial sale of YH001, royalties will range from the lower double digits to the mid-double digits. If sales of YH001 exceed a pre-determined sales threshold in the first full year of sales following first commercial sale, the Company will owe a milestone to Eucure in the high single digit millions. Payment obligations under the YH001 Collaboration Agreement continue on a country-by-country basis until the latest of (i) expiration of the last to expire licensed patent covering YH001, (ii) expiration of marketing or regulatory exclusivity covering YH001 and (iii) 10 years from the first commercial sale of YH001 in such country in North America. Eucure has agreed to manufacture and supply, or to arrange for a third party manufacturer to manufacture and supply, YH001 to the Company at cost plus a low double digit markup for commercial sales pursuant to the terms of a commercial supply and quality agreement to be separately negotiated. 3D Medicines and Alphamab Collaboration and Clinical Trial Agreement In December 2019, the Company, 3D Medicines Co., Ltd. (3D Medicines), and Jiangsu Alphamab Biopharmaceuticals Co., Ltd. (Alphamab) entered into a collaboration and clinical trial agreement (the Envafolimab Collaboration Agreement) for the development of envafolimab, also known as KN035, an investigational PD-L1 single-domain antibody (sdAb), or nanobody, administered by subcutaneous injection, for the treatment of sarcoma in North America. No consideration was exchanged in the Envafolimab Collaboration Agreement. Given no consideration was exchanged, no value was assigned to the Envafolimab Collaboration Agreement in the accompanying consolidated balance sheets. Pursuant to the Envafolimab Collaboration Agreement, the Company was granted an exclusive license to develop and commercialize envafolimab for the treatment of sarcoma in North America. The Company is responsible for conducting, and will bear the costs of Phase 1, Phase 2, and Phase 3 or post-approval clinical trial s in North America for envafolimab in the indications of refractory and first line treatment of sarcoma. 3D Medicines and Alphamab are responsible for conducting, and will bear the costs of, investigational new drug ( IND ) -enabling studies (other than those specific to the sarcoma indication) and the preparation of chemistry, manufacturing and controls (CMC) activities sections of an IND application for envafolimab. 3D Medicines and Alphamab have agreed to manufacture and supply, or to arrange for a third party manufacturer to manufacture and supply, envafolimab to the Company at pre-negotiated prices that vary based on clinical or commercial use. 3D Medicines and Alphamab retained the right to develop envafolimab in all territories outside of North America as well as within North America for all indications other than sarcoma. The Company will be responsible for commercializing envafolimab for sarcoma in North America, including booking of sales revenue, unless (a) envafolimab is first approved in North America for an indication other than sarcoma and launched in North America, or (b) envafolimab is first approved in North America for sarcoma and subsequently approved in North America for an additional non-orphan indication and sold commercially by 3D Medicines and/or Alphamab, or a licensee, in which case 3D Medicines and Alphamab will be responsible for commercializing envafolimab for sarcoma in North America, including booking of sales revenue. If 3D Medicines and Alphamab become responsible for commercialization under the Envafolimab Collaboration Agreement, the Company has the option to co-market envafolimab for sarcoma in North America. In the event that envafolimab is first approved in North America for sarcoma and within three years of the commercial launch of envafolimab in North America for sarcoma 3D Medicines and Alphamab replace the Company as the party responsible for commercialization, and the Company elects and 3D Medicines and Alphamab agree for the Company to not co-market envafolimab for sarcoma in North America, then 3D Medicine and Alphamab will be required to compensate the Company for its costs associated with preparing for and conducting commercial activities. If the Company has the responsibility for commercialization under the Envafolimab Collaboration Agreement, the Company will owe 3D Medicines and Alphamab tiered double digit royalties on net sales of envafolimab for sarcoma in North America ranging from the teens to mid-double digits. If 3D Medicines and Alphamab have responsibility for commercialization under the Envafolimab Collaboration Agreement, the Company will be entitled to (a) escalating double digit royalties on net sales of envafolimab for sarcoma in North America ranging from the teens to mid-double digits if the Company has chosen to not co-market envafolimab in sarcoma or (b) a 50% royalty on net sales of envafolimab for sarcoma in North America if the Company has chosen to co-market envafolimab in sarcoma. Payment obligations under the Envafolimab Collaboration Agreement continue on a country-by-country basis until the last to expire licensed patent covering envafolimab expires. 3D Medicines and Alphamab retain the right to reacquire the rights to envafolimab for sarcoma in North America in connection with an arm’s length sale to a third party, provided that the sale may not occur prior to completion of a pivotal trial of envafolimab in sarcoma without the Company’s written consent and the parties must negotiate in good faith and agree to fair compensation to be paid to the Company for the value of and opportunity represented by the required rights. Each party agreed that during the term of the Envafolimab Collaboration Agreement, it would not develop or license from any third party a monospecific inhibitor to PD-L1 or PD-1 in sarcoma. The term of the Envafolimab Collaboration Agreement continues until the later of the date the parties cease further development and commercialization of envafolimab for sarcoma in North America or the expiration of all payment obligations. The Envafolimab Collaboration Agreement may be terminated earlier by a party in the event of an uncured material breach by the other party or bankruptcy of the other party, or for safety reasons related to envafolimab. In the event the Company elects, or a joint steering committee determines, to cease further development or commercialization of envafolimab, or if the Company fails to use commercially reasonable efforts to develop (including progress in clinical trials) and commercialize envafolimab and does not cure such failure within a specified time period, then the Company’s rights and obligations under the Envafolimab Collaboration Agreement will revert to 3D Medicines and Alphamab. I-Mab Collaboration Agreements In November 2018, the Company and I-Mab Biopharma (I-Mab) entered into separate strategic collaboration and clinical trial agreements (the I-Mab Collaboration Agreements No consideration was exchanged in the I- I-Mab TJ004309 Agreement Pursuant to the TJ004309 Agreement, the Company and I-Mab are collaborating on developing the TJ004309 antibody, with the Company bearing the costs of filing an IND and for Phase 1 clinical trials, with the parties sharing costs equally for Phase 2 clinical trials, and with the Company and I-Mab bearing 40% and 60%, respectively, of the costs for pivotal clinical trials. I-Mab will be responsible for the cost of certain non-clinical activities, the drug supply of TJ004309, and any reference drugs used in the clinical trials. Each of the parties also agreed for a specified period of time to not develop or license to or from a third party any monoclonal antibody targeting CD73 or any other biologic for certain indications that a joint steering committee (JSC), as set up under the TJ004309 Agreement, selects for TJ004309 development. In the event that I-Mab licenses rights to TJ004309 to a third party, the Company would be entitled to receive escalating portions of royalty and non-royalty consideration received by I-Mab with respect to territories outside of Greater China. In the event that I-Mab commercializes TJ004309, the Company would be entitled to receive a royalty on net sales by I-Mab in North America ranging from the mid-single digits to low double digits, and in the EU and Japan in the mid-single digits. The portions of certain third-party royalty and non-royalty consideration and the royalty from net sales by I-Mab to which the Company would be entitled escalate based on the phase of development and relevant clinical trial obligations the Company completed under the TJ004309 Agreement, ranging from a high-single digit to a mid-teen percentage of non-royalty consideration as well as a double digit percentage of royalty consideration. In March 2020, I-Mab issued a press release announcing a strategic partnership with KG Bio, whereby KG Bio received what the press release described as a right of first negotiation outside North America for TJ004309 for up to $340 million in potential payments to I-Mab. On April 8, 2020, the Company issued a notice of dispute regarding possible breach of the TJ004309 Agreement, which resulted in a binding arbitration proceeding under the Rules of Arbitration of the ICC before the Tribunal. The latest developments in the dispute with I-Mab are discussed in more detail below following the discussion of the Bispecific Agreement. The TJ004309 Agreement may be terminated by either party in the event of an uncured material breach by the other party or bankruptcy of the other party, or for safety reasons related to TJ004309. I-Mab may also terminate the TJ004309 Agreement if the Company causes certain delays in completing a Phase 1 clinical trial. In addition, I-Mab may terminate the TJ004309 Agreement for any reason within 90 days following the completion of the first Phase 1 clinical trial, in which case the Company would be entitled to a minimum termination fee of $9.0 million, or following the completion of the first Phase 2 clinical trial, in which case the Company would be entitled to a pre-specified termination fee of $15.0 million and either a percentage of non-royalty consideration I-Mab may receive as part of a license to a third party or an additional payment if TJ004309 is approved for marketing outside Greater China before a third-party license is executed, in addition to a double digit percentage of royalty consideration. In 2021, I-Mab sent the Company notices purporting to terminate the TJ004309 Agreement, which would result in I-Mab owing the Company a prespecified termination fee of $9.0 million. However, I-Mab does not have an option to terminate the TJ004309 Agreement without cause until the ongoing Phase 1 clinical trial of TJ004309 is “Complete,” as that term is defined in the TJ004309 Agreement, and the Company responded by disputing the basis for I-Mab’s termination. In March 2021, I-Mab filed a lawsuit in the Delaware Court of Chancery seeking an order of specific performance requiring the Company to comply with I-Mab’s effort to terminate the agreement. The Company disagreed with I-Mab’s position and in May 2021, the Delaware Court of Chancery stayed the lawsuit filed by I-Mab and subsequently this matter was remanded and included in the proceeding before the Tribunal . Bispecific Agreement Pursuant to the Bispecific Agreement, the Company and I-Mab may mutually select through a joint steering committee (JSC) up to five of I-Mab’s bispecific antibody (BsAb) product five-year For each product candidate selected by the JSC for development under the Bispecific Agreement, I-Mab will be responsible and bear the costs for IND-enabling studies and establishing manufacturing for the product candidate, while the Company will be responsible for and bear the costs of filing an IND and conducting Phase 1 and Phase 2 clinical trials, and the Company will be responsible for and will share equally with I-Mab in the costs of conducting Phase 3 or pivotal clinical trials, in each case within North America. Subject to I-Mab’s right to co-promote an approved product candidate, the Company will be responsible for commercializing any approved product candidates in North America and will share profits and losses equally with I-Mab in North America. The Company would also be entitled to tiered low single digit royalties on net sales of product candidates in the EU and Japan. At any time prior to completing the first pivotal clinical trial for a product candidate or if I-Mab ceases to support development costs or pay its portion of Phase 3 clinical trial costs for a product candidate or the JSC decides to cease development over the Company’s objections after initiating Phase 3 clinical trials, the Company will have an option to obtain an exclusive license to such product candidate in all territories except If the Company exercises the option, it would assume sole responsibility for developing and commercializing the product candidate in the licensed territory, and in lieu of profit or loss sharing with I-Mab with respect to such product candidate, the Company would owe I-Mab pre-specified upfront and milestone payments and royalties on net sales, with the payments and royalties escalating depending on the phase of development the product candidate reached at the time the Company obtained the exclusive license as follows: (i) if before IND-enabling studies Each party agreed that for a specified period of time, it would not develop or license to or from any third party any bispecific monoclonal antibody targeting If development of any selected product candidates is terminated by a decision of the JSC, all rights to the product candidate will revert to I-Mab, subject to the Company’s right to obtain an exclusive license in certain circumstances. If development is terminated after submission of an IND and prior to initiating Phase 3 clinical trials or after initiating Phase 3 clinical trials and with the Company’s concurrence, the Company would be entitled to tiered low single digit royalties on net sales of the product candidate in North America, the EU, and Japan. The Bispecific Agreement In March 2020, the Company learned that I-Mab had entered into two license and collaboration agreements with ABL Bio in July 2018. Under ABL Bio License 1, I-Mab granted to ABL Bio exclusive, worldwide (excluding Greater China), royalty-bearing rights to develop and commercialize a BsAb using certain monoclonal antibody sequences. Under ABL License 2, I-Mab and ABL agreed to collaborate to develop three PD-L1-based bispecific antibodies by using ABL Bio’s proprietary BsAb technology and commercialize them in their respective territories, which, collectively, include China, Hong Kong, Macau, Taiwan and South Korea, and other territories throughout the rest of the world if both parties agree to do so in such other territories during the performance of the agreement. In June 2020, I-Mab commenced an arbitration proceeding under the Rules of Arbitration of the International Chamber of Commerce (the ICC) before an arbitration tribunal seated in New York City (the Tribunal) after the Company invoked contractual dispute resolution provisions asserting that I-Mab had breached its contractual obligations concerning the TJ004309 Agreement and Bispecific Agreement. The Tribunal held a hearing on the merits in February 2022, and final post-hearing briefs were submitted by the Company and I-Mab in May 2022. On November 8, 2022, the Tribunal invited the parties to submit additional, limited briefing on two discrete issues by December 9, 2022. Following that submission, the parties submitted their respective cost submissions for attorney fees reimbursement in January 2023. The Tribunal did not indicate when it expects to render its final decision; however, it did note that it was far along in its deliberations and preparation of a final award. Under the applicable rules of the arbitration, the prevailing party may be awarded attorneys’ fees at the Tribunal’s discretion. As of the date of this Annual Report, the TJ004309 Agreement and Bispecific Agreement disputes remain under consideration by the Tribunal, and the Company expects the Tribunal to render its final decision in the first quarter of 2023. The claims under the arbitration are complex; accordingly, the Company cannot predict the outcome of the arbitration, and is unable to estimate the amount of recovery or damages, if any, that may be awarded by the Tribunal.

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Leases	8. Leases The Company’s operating lease obligations relate to its corporate headquarters as the Company leases its office space under a non-cancelable operating lease. The Company amended its lease in August 2021 extending the lease term to April 2027. The lease is subject to base lease payments and additional charges for common area maintenance and other costs and includes certain lease incentives and tenant improvement allowances. Operating lease expense was $0.4 million for each of the three years ended December 31, 2022, 2021 and 2020. As of December 31, 2022, the Company does not have any finance leases, nor any other operating leases. Supplemental cash flow information related to operating leases was as follows (in thousands): Years Ended December 31, 2022 2021 2020 Cash paid within operating cash flows $ 285 $ 461 $ 442 ROU assets recognized in exchange for new lease obligations $ — $ 1,117 $ — Supplemental balance sheet information related to operating leases was as follows (in thousands, except lease term and discount rate): December 31, 2022 2021 Reported as: Other assets (ROU asset) $ 1,123 $ 1,325 Accounts payable and accrued expenses (lease liability) $ 198 $ 147 Other long-term liabilities (lease liability) 969 1,167 Total lease liabilities $ 1,167 $ 1,314 Weighted average remaining lease term 4.3 5.3 Weighted average discount rate 11.3 % 11.3 % As of December 31, 2022 2023 $ 320 2024 334 2025 349 2026 365 2027 123 Total lease payments 1,491 Less imputed interest (324 ) Total operating lease liabilities $ 1,167 Under the terms of the lease agreement, the Company provided the lessor with an irrevocable letter of credit in the amount of $66,949. The lessor is entitled to draw on the letter of credit in the event of any default by the Company under the terms of the lease.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes A reconciliation of the Company’s effective tax rate and federal statutory tax rate is summarized as follows (in thousands): Years Ended December 31, 2022 2021 2020 Federal income taxes $ (6,118) $ (6,020 ) $ (3,523 ) State income taxes, net of federal benefit (1,962) (1,889 ) (1,084 ) Permanent items 81 93 104 Uncertain tax positions 2,477 494 1,224 Research and development credits (2,119) (1,661 ) (555 ) Other, net 125 28 — Stock compensation 78 203 113 Change in valuation allowance 7,438 8,752 3,721 Provision for income taxes $ — $ — $ — Significant components of the Company’s deferred tax assets and deferred tax liabilities are summarized as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 50,779 $ 47,633 Research and development and Orphan Drug credits 11,928 10,472 Depreciation and amortization 236 247 Right-of-use liability 245 276 Section 174 capitalized research expense 2,503 — Other, net 1,906 1,573 Total deferred tax assets 67,597 60,201 Right-of-use asset (236) (278 ) Total deferred tax liabilities (236) (278 ) Total net deferred 67,361 59,923 Valuation allowance (67,361) (59,923 ) Net deferred tax assets $ — $ — The Company has net deferred tax assets relating primarily to net operating loss (NOL) carryforwards and research and development and Orphan Drug credit carryforwards. Beginning in 2022, the Tax Cuts and Jobs Act of 2017 requires taxpayers to capitalize and amortize research and development expenditures over five years for domestic research and 15 years for foreign research pursuant to Section 174 of the Internal Revenue Code (Code). Subject to certain limitations, the Company may use these deferred tax assets to offset taxable income in future periods. Due to the Company’s history of losses and uncertainty regarding future earnings, a full valuation allowance has been recorded against the Company’s deferred tax assets, as it is more likely than not that such assets will not be realized. The net change in the total valuation allowance for the years ended December 31, 2022, 2021 and 2020 was $7.4 million, $8.8 million and $3.7 million, respectively. As of December 31, 2022, the Company had federal and California NOL carryforwards of $194.3 million and $144.5 million, respectively. The federal and California NOL carryforwards will begin to expire in 2030 and 2033, respectively, if not utilized. The federal NOL generated after 2017 of $111.1 million will carryforward indefinitely, but the deductibility of such federal NOLs is limited to 80% of taxable income. As of December 31, 2022, the Company also had federal research and development and Orphan Drug tax credit carryforwards of $13.7 million and California research and development tax credit carryforwards of $3.0 million. The federal research and development and Orphan Drug tax credit carryforwards will begin expiring in 2031 and 2036, respectively, if not utilized. The California research credit will carry forward indefinitely under current law. Pursuant to Sections 382 and 383 of the Code , the annual use of the Company’s NOL and research and development credit carryforwards may be limited in the event that a cumulative change in ownership of more than 50 % occurs within a three-year period. The Company previously completed a Section 382/383 analysis regarding the limitation of NOL and research and development credit carryforwards as of December 31, 201 8 and did not identify any change in ownership of more than 50 % within the preceding three-year period since an ownership change was determined to have occurred at the time of the Company’s initial public offering in January 2015 . The Company has not completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since December 31, 2018. If the Company has experienced an ownership change at any time since December 31, 2018, utilization of the NOL or R&D credit carryforwards would be subject to an annual limitation under Section 382 of the Code. Any limitation may result in expiration of a portion of the NOL or R&D credit carryforwards before utilization. Any carryforwards that will expire prior to utilization as a result of such limitations will be removed from deferred tax assets with a corresponding reduction of the valuation allowance with no net effect on income tax expense or the effective tax rate . The Inflation Reduction Act of 2022, which incorporates a Corporate Alternative Minimum Tax (CAMT), was signed on August 16, 2022. The changes will become effective for the tax years beginning after December 31, 2022. The new tax will require companies to compute two separate calculations for federal income tax purposes and pay the greater of the new minimum tax or their regular tax liability. The act is not expected to have a significant impact on the Company's financial position, results of operations or cash flows. The changes in the Company’s unrecognized tax benefits are summarized as follows (in thousands): Balance at December 31, 2019 $ 5,092 Change related to prior year positions — Increase related to current year positions 1,518 Balance at December 31, 2020 6,610 Change related to prior year positions 1 Increase related to current year positions 506 Balance at December 31, 2021 7,117 Change related to prior year positions (5) Increase related to current year positions 2,984 Balance at December 31, 2022 $ 10,096 The Company’s policy is to include interest and penalties related to unrecognized income tax benefits as a component of income tax expense. The Company has no accruals for interest or penalties in the accompanying consolidated balance sheets as of December 31, 2022 and 2021 and has not recognized interest or penalties in the accompanying consolidated statements of operations for the three years in the period ended December 31, 2022. Due to the valuation allowance recorded against the Company’s deferred tax assets, future changes in unrecognized tax benefits will not impact the Company’s effective tax rate. The Company does not expect its unrecognized tax benefits to change significantly in the next 12 months. The Company is subject to taxation in the United States and California. Due to the net operating loss carryforwards, the U.S. federal and California returns are open to examination for all years since inception. The Company has not been, nor is it currently, under examination by the federal or any state tax authority.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2022
Compensation And Retirement Disclosure [Abstract]
401(k) Plan	10. 401(k) Plan The Company maintains a defined contribution 401(k) plan available to eligible employees. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under federal tax regulations. The Company, at its discretion, may make certain matching contributions to the 401(k) plan. Matching contributions for the years ended December 31, 2022, 2021 and 2020 totaled $0.2 million, $0.1 million and $0.1 million, respectively.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Organization And Accounting Policies [Abstract]
Organization and Business	Organization and Business TRACON Pharmaceuticals, Inc. (TRACON or the Company) was incorporated in the state of Delaware on October 28, 2004. TRACON is a biopharmaceutical company focused on the development and commercialization of novel targeted therapeutics for cancer, and utilizes its cost efficient, contract research organization (CRO) independent product development platform to partner with other life science companies to develop and commercialize innovative products in the United States. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, TRACON Pharma Limited and TRACON Pharma International Limited, which were formed in September 2015 and January 2019, respectively, and are currently inactive. All significant intercompany accounts and transactions have been eliminated.
Basis of Presentation	Basis of Presentation As of December 31, 2022, the Company has devoted substantially all its efforts to product development, raising capital, and building infrastructure and has not realized revenues from its planned principal operations. The Company has incurred operating losses since inception. As of December 31, 2022, the Company had an accumulated deficit of $236.9 million. The Company anticipates that it will continue to incur net losses into the foreseeable future as it continues the development and commercialization of its product candidates and works to develop additional product candidates through research and development programs. At December 31, 2022, the Company had cash and cash equivalents of $17.5 million, of which $0.1 million is classified as restricted cash as it is pledged as collateral for the Company’s obligations under its corporate headquarters facility lease. Based on the Company’s current business plan, management believes that there is substantial doubt as to whether existing cash and cash equivalents will be sufficient to meet its obligations as they become due within twelve months from the date the consolidated consolidated The Company plans to continue to fund its losses from operations through its existing cash and cash equivalents, as well as through future equity offerings, debt financings, other third-party funding, and potential licensing or collaboration arrangements. In addition, the Company may fund its losses from operations through the Capital on Demand TM
Risks And Uncertainties	Risks and Uncertainties COVID-19, a novel strain of coronavirus (together with its variants, COVID-19), has become a global pandemic. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world. While vaccines have become widely available in certain countries, and businesses and economies have reopened, the status of global economic recovery remains uncertain and unpredictable, and will continue to be impacted by developments in the pandemic including any subsequent waves of outbreak or new variant strains of the COVID-19 virus which may require re-closures or other preventative measures. The COVID-19 pandemic may also have long-term effects on the nature of the office environment and remote working, which may present risks for the Company’s strategy, operational, talent recruiting and retention, and workplace culture. In addition to the ongoing COVID-19 pandemic, global economic and business activities continue to face widespread macroeconomic uncertainties, including labor shortages, inflation and monetary supply shifts, recession risks and potential disruptions from the Russia-Ukraine conflict. The Company continues to actively monitor the impact of these macroeconomic factors on its financial condition, liquidity, operations, and workforce. The extent of the impact of these factors on the Company’s operational and financial performance, including its ability to execute its business strategies and initiatives in the expected time frame, will depend on future developments, which are uncertain and cannot be predicted; however, any continued or renewed disruption resulting from these factors could negatively impact the Company’s business .
Use of Estimates	Use of Estimates The Company’s consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States (GAAP). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenue, and expenses. The most significant estimates in the Company’s consolidated
Restricted Cash	Restricted Cash Restricted cash consists of money market funds held by the Company’s financial institution as collateral for the Company’s obligations under its facility lease for the Company’s corporate headquarters in San Diego, California.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash and highly liquid investments with original maturities of three months or less at the date of purchase. The carrying amounts approximate fair value due to the short maturities of these investments. Cash and cash equivalents include cash in readily available checking and money market funds.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held.
Property and Equipment	Property and Equipment Property and equipment is stated at cost and depreciated using the straight-line method over the estimated useful life of the related assets, which is generally five years. Leasehold improvements are amortized over the shorter of the lease term or estimated useful life of the related assets. Repairs and maintenance costs are charged to expense as incurred.
Leases	Leases The Company determines if an arrangement contains a lease at inception. For arrangements where the Company is the lessee, operating leases are recorded as other assets, accounts payable and accrued expenses, and other long-term liabilities within the consolidated balance sheet. The Company currently does not have any finance leases. Operating lease right-of-use (ROU) assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. ROU assets also include any initial direct costs incurred and any lease payments made at or before the lease commencement date, less lease incentives received. The Company uses its incremental borrowing rate based on the information available at the commencement date in determining the lease liabilities as the Company’s leases generally do not provide an implicit rate. Lease terms may include options to extend or terminate when the Company is reasonably certain that the option will be exercised. Lease expense is recognized on a straight-line basis over the lease term.
Revenue Recognition	Revenue Recognition To date, substantially all the Company’s revenue has been derived from license agreements. The terms of these arrangements included payments to the Company for the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. In accordance with Accounting Standards Codification 606, Revenue from Contracts with Customers . As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of each arrangement that includes development, commercialization, and regulatory milestone payments, the Company evaluates whether the achievement of the milestones is considered probable and estimates the amount to be included in the transaction price using the most likely amount method. Performance milestone payments represent a form of variable consideration. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Achievement of milestones that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable until the approvals are achieved. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis and the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achieving such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations at the outset of the arrangement. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its out-licensing arrangements. The Company receives payments from its collaborators based on billing schedules established in each contract. Up-front and other payments may require deferral of revenue recognition to a future period until the Company performs its obligations under its collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.
Clinical Trial Expense Accruals	Clinical Trial Expense Accruals As part of the process of preparing the Company’s financial statements, the Company is required to estimate expenses resulting from its obligations The Company’s objective is to reflect the appropriate trial expenses in its consolidated financial statements by recording those expenses in the period in which services are performed and efforts are expended. The Company accounts for these expenses according to the progress of the clinical trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through discussion with the clinical sites and applicable personnel and outside service providers as to the progress or state of consummation of trials. During a clinical trial, the Company adjusts the clinical expense recognition if actual results differ from its estimates. The Company makes estimates of accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. The Company’s clinical trial accruals are dependent upon accurate reporting by clinical sites and other third-party vendors. Although the Company does not expect its estimates to differ materially from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For each of the three years in the period ended December 31, 2022, there were no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials.
Research and Development Costs	Research and Development Costs Research and development costs, including license fees, are expensed as incurred.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the grant date fair value of employee stock option grants, employee restricted stock unit grants (RSUs), and employee stock purchase plan (ESPP) rights recognized as expense over the requisite service period of the awards (usually the vesting period) on a straight-line basis. The Company estimates the fair value of stock option grants and ESPP rights using the Black-Scholes option pricing model. The fair value of RSUs is based on the closing sales price for such stock on the date of grant. Equity award forfeitures are recorded as they occur.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the consolidated The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than‑not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Net loss and comprehensive loss were the same for all periods presented.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average shares of common stock outstanding for the period, without consideration for common stock equivalents and adjusted for the weighted average number of shares of common stock outstanding that are subject to repurchase. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): December 31, 2022 2021 2020 Warrants to purchase common stock 6,766,246 4,810,409 4,810,409 Common stock options 2,246,310 1,308,360 601,481 ESPP shares 3,387 3,258 5,349 9,015,943 6,122,027 5,417,239
Segment Reporting	Segment Reporting 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.

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Organization And Accounting Policies [Abstract]
Schedule of potentially dilutive securities not included in the calculation of diluted net loss per share	Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): December 31, 2022 2021 2020 Warrants to purchase common stock 6,766,246 4,810,409 4,810,409 Common stock options 2,246,310 1,308,360 601,481 ESPP shares 3,387 3,258 5,349 9,015,943 6,122,027 5,417,239

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Available-for-sale Securities and Equity Securities	Cash equivalents, which are classified as equity securities, and restricted cash consisted of the following (in thousands): December 31, 2022 December 31, 2021 Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Money market funds $ 10,150 $ — $ — $ 10,150 $ 5,003 $ — $ — $ 5,003 Equity securities (1) — — — — 246 — — 246 $ 10,150 $ — $ — $ 10,150 $ 5,249 $ — $ — $ 5,249 Classified as: Cash equivalents $ 10,083 $ 5,003 Restricted cash 67 — Other assets — 246 Total cash equivalents, restricted cash, and other assets $ 10,150 $ 5,249
Schedule of assets and liabilities measured at fair value on a recurring basis	The fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Significant Active Markets Other Significant for Identical Observable Unobservable Assets Inputs Inputs Total (Level 1) (Level 2) (Level 3) At December 31, 2022 Money market funds $ 10,150 $ — $ 10,150 $ — At December 31, 2021 Money market funds $ 5,003 $ — $ 5,003 $ —

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Schedule Of Property and Equipment	Property and equipment consisted of the following (in thousands): December 31, 2022 2021 Computer and office equipment $ 203 $ 186 Furniture and fixtures 19 19 Leasehold improvements 21 21 243 226 Less accumulated depreciation and amortization (192 ) (176 ) $ 51 $ 50
Schedule Of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2022 2021 Accounts payable $ 3,923 $ 4,943 Accrued clinical related expenses 6,091 4,461 Accrued legal and accounting 299 842 Accrued long-term debt terminal interest 425 280 Current portion of operating lease liability 198 147 Other accruals 171 80 $ 11,107 $ 10,753

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2022
Debt Disclosure [Abstract]
Schedule of Long-term debt and unamortized debt discount balances	Long-term debt and unamortized debt discount balances associated with the RGC Loan Agreement entered into in 2022 were as follows (in thousands): December 31, 2022 Long-term debt $ 10,000 Less debt discount, net of current portion — Long-term debt, net of debt discount 10,000 Less current portion of long-term debt (10,000 ) Long-term debt, net of current portion $ — Current portion of long-term debt $ 10,000 Current portion of debt discount (193 ) Current portion of long-term debt, net $ 9,807
Schedule of future minimum principal and interest payments	As of December 31, 2022, future minimum principal and interest payments, including the final payment, under the RGC Loan Agreement are as follows (in thousands): 2023 $ 10,491 10,491 Less interest and final payment (491 ) Long-term debt $ 10,000
Schedule of exercisable outstanding warrants for purchase of common stock issued	At December 31, 2022, the Company had the following exercisable outstanding warrants for the purchase of common stock issued in connection with the Company’s loan agreements with SVB : Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 May 3, 2025 5,363 $ 26.10 13,906 As of December 31, 2022 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 March 27, 2024 1,369,602 $ 27.00 May 3, 2025 5,363 $ 26.10 August 27, 2030 1,889,513 $ 0.01 August 31, 2030 1,137,454 $ 0.01 June 21, 2032 2,205,018 $ 0.01 September 2, 2032 150,753 $ 1.99 6,766,246

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2022
Stockholders Equity Note [Abstract]
Schedule of exercisable outstanding warrants for purchase of common stock issued	At December 31, 2022, the Company had the following exercisable outstanding warrants for the purchase of common stock issued in connection with the Company’s loan agreements with SVB : Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 May 3, 2025 5,363 $ 26.10 13,906 As of December 31, 2022 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price November 14, 2023 through June 4, 2024 3,874 $ 77.40 January 25, 2024 4,669 $ 51.40 March 27, 2024 1,369,602 $ 27.00 May 3, 2025 5,363 $ 26.10 August 27, 2030 1,889,513 $ 0.01 August 31, 2030 1,137,454 $ 0.01 June 21, 2032 2,205,018 $ 0.01 September 2, 2032 150,753 $ 1.99 6,766,246
Schedule of stock option activity	Stock option activity under all Plans is summarized as follows: Weighted- Number of Average Options Exercise Price Balance at December 31, 2021 1,308,360 $ 13.99 Granted 937,950 2.20 Exercised — — Forfeited — — Balance at December 31, 2022 2,246,310 $ 9.07
Schedule of outstanding stock options	Information about the Company’s outstanding stock options as of December 31, 2022 is as follows: Weighted- Average Weighted- Remaining Average Contractual Aggregate Number of Exercise Term Intrinsic Shares Price (in years) Value Options outstanding 2,246,310 $ 9.07 8.00 $ 23,168 Options vested and expected to vest 2,246,310 $ 9.07 8.00 $ 23,168 Options exercisable 860,683 $ 17.36 6.75 $ 1,480
Summary of weighted-average assumptions used Black-Scholes option pricing model to determine the fair value	The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows: Years Ended December 31, 2022 2021 2020 Risk-free interest rate 1.9 % 0.8 % 1.2 % Expected volatility 89.8 % 90.3 % 85.8 % Expected term (in years) 6.2 6.2 6.2 Expected dividend yield — — —
Summary of allocation of stock-based compensation expense	The allocation of stock-based compensation expense was as follows (in thousands): Years Ended December 31, 2022 2021 2020 Research and development $ 830 $ 628 $ 386 General and administrative 1,211 1,147 648 $ 2,041 $ 1,775 $ 1,034
Schedule of common stock reserved for future issuance	Common stock reserved for future issuance was as follows: December 31, 2022 2021 Common stock warrants 6,766,246 4,810,409 Common stock options granted and outstanding 2,246,310 1,308,360 Awards available under the 2015 Plan 150,335 115,990 Shares available under the Employee Stock Purchase Plan 243,817 105,619 9,406,708 6,340,378

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Schedule of Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases was as follows (in thousands): Years Ended December 31, 2022 2021 2020 Cash paid within operating cash flows $ 285 $ 461 $ 442 ROU assets recognized in exchange for new lease obligations $ — $ 1,117 $ —
Schedule of Supplemental Balance Sheet Information Related to Operating Leases	Supplemental balance sheet information related to operating leases was as follows (in thousands, except lease term and discount rate): December 31, 2022 2021 Reported as: Other assets (ROU asset) $ 1,123 $ 1,325 Accounts payable and accrued expenses (lease liability) $ 198 $ 147 Other long-term liabilities (lease liability) 969 1,167 Total lease liabilities $ 1,167 $ 1,314 Weighted average remaining lease term 4.3 5.3 Weighted average discount rate 11.3 % 11.3 %
Schedule of Maturities of Operating Lease Liabilities	As of December 31, 2022 2023 $ 320 2024 334 2025 349 2026 365 2027 123 Total lease payments 1,491 Less imputed interest (324 ) Total operating lease liabilities $ 1,167

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Schedule of reconciliation of effective tax rate and federal statutory tax rate	A reconciliation of the Company’s effective tax rate and federal statutory tax rate is summarized as follows (in thousands): Years Ended December 31, 2022 2021 2020 Federal income taxes $ (6,118) $ (6,020 ) $ (3,523 ) State income taxes, net of federal benefit (1,962) (1,889 ) (1,084 ) Permanent items 81 93 104 Uncertain tax positions 2,477 494 1,224 Research and development credits (2,119) (1,661 ) (555 ) Other, net 125 28 — Stock compensation 78 203 113 Change in valuation allowance 7,438 8,752 3,721 Provision for income taxes $ — $ — $ —
Schedule of components of deferred tax assets and deferred tax Liabilities	Significant components of the Company’s deferred tax assets and deferred tax liabilities are summarized as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 50,779 $ 47,633 Research and development and Orphan Drug credits 11,928 10,472 Depreciation and amortization 236 247 Right-of-use liability 245 276 Section 174 capitalized research expense 2,503 — Other, net 1,906 1,573 Total deferred tax assets 67,597 60,201 Right-of-use asset (236) (278 ) Total deferred tax liabilities (236) (278 ) Total net deferred 67,361 59,923 Valuation allowance (67,361) (59,923 ) Net deferred tax assets $ — $ — The Company has net deferred tax assets relating primarily to net operating loss (NOL) carryforwards and research and development and Orphan Drug credit carryforwards. Beginning in 2022, the Tax Cuts and Jobs Act of 2017 requires taxpayers to capitalize and amortize research and development expenditures over five years for domestic research and 15 years for foreign research pursuant to Section 174 of the Internal Revenue Code (Code). Subject to certain limitations, the Company may use these deferred tax assets to offset taxable income in future periods. Due to the Company’s history of losses and uncertainty regarding future earnings, a full valuation allowance has been recorded against the Company’s deferred tax assets, as it is more likely than not that such assets will not be realized. The net change in the total valuation allowance for the years ended December 31, 2022, 2021 and 2020 was $7.4 million, $8.8 million and $3.7 million, respectively.
Schedule of changes in unrecognized tax benefits	The Inflation Reduction Act of 2022, which incorporates a Corporate Alternative Minimum Tax (CAMT), was signed on August 16, 2022. The changes will become effective for the tax years beginning after December 31, 2022. The new tax will require companies to compute two separate calculations for federal income tax purposes and pay the greater of the new minimum tax or their regular tax liability. The act is not expected to have a significant impact on the Company's financial position, results of operations or cash flows. The changes in the Company’s unrecognized tax benefits are summarized as follows (in thousands): Balance at December 31, 2019 $ 5,092 Change related to prior year positions — Increase related to current year positions 1,518 Balance at December 31, 2020 6,610 Change related to prior year positions 1 Increase related to current year positions 506 Balance at December 31, 2021 7,117 Change related to prior year positions (5) Increase related to current year positions 2,984 Balance at December 31, 2022 $ 10,096 The Company’s policy is to include interest and penalties related to unrecognized income tax benefits as a component of income tax expense. The Company has no accruals for interest or penalties in the accompanying consolidated balance sheets as of December 31, 2022 and 2021 and has not recognized interest or penalties in the accompanying consolidated statements of operations for the three years in the period ended December 31, 2022. Due to the valuation allowance recorded against the Company’s deferred tax assets, future changes in unrecognized tax benefits will not impact the Company’s effective tax rate. The Company does not expect its unrecognized tax benefits to change significantly in the next 12 months. The Company is subject to taxation in the United States and California. Due to the net operating loss carryforwards, the U.S. federal and California returns are open to examination for all years since inception. The Company has not been, nor is it currently, under examination by the federal or any state tax authority.

Organization and Summary of S_4

Organization and Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)
Basis of Presentation
Accumulated deficit	$ (236,911,000)	$ (207,776,000)
Cash, cash equivalents	17,500,000
Restricted cash	$ 67,000
Property and Equipment
Estimated useful life	5 years
Segment reporting
Number of reportable segments | segment	1
Jones Trading Institutional Services LLC | Capital on Demand Sales Agreement | Common Stock
Basis of Presentation
Maximum aggregate value of stock to be sold	$ 50,000,000
Remaining amount available under the Sales Agreement	$ 45,700,000

Organization and Summary of S_5

Organization and Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Included in the Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive securities
Antidilutive securities	9,015,943	6,122,027	5,417,239
Warrants to Purchase Common Stock
Antidilutive securities
Antidilutive securities	6,766,246	4,810,409	4,810,409
Common Stock Options
Antidilutive securities
Antidilutive securities	2,246,310	1,308,360	601,481
ESPP Shares
Antidilutive securities
Antidilutive securities	3,387	3,258	5,349

Financial Instruments and Fai_3

Financial Instruments and Fair Value Measurements - Schedule of Available-for-sale Securities and Equity Securities (Details) - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 31, 2021
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost		$ 10,150	$ 5,249
Estimated Fair Value		10,150	5,249
Cash equivalents		10,083	5,003
Restricted cash		67
Other assets			246
Total cash equivalents, restricted cash, and other assets		10,150	5,249
Money market funds
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost		10,150	5,003
Estimated Fair Value		10,150	5,003
Equity securities
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost	[1]		246
Estimated Fair Value		$ 200	$ 246	[1]
[1]The Company’s equity securities included in other assets as of December 31, 2021 consisted of its investment in a privately held company obtained as partial consideration under the 2021 Enviro license agreement. The Company recognizes its private company equity securities at cost minus impairments, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. The $0.2 million investment was fully impaired during the year ended December 31, 2022 and recorded within other expense on the consolidated statements of operations.

Financial Instruments and Fai_4

Financial Instruments and Fair Value Measurements - Schedule of Available-for-sale Securities and Equity Securities (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Estimated Fair Value	$ 10,150	$ 5,249
Equity securities
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Estimated Fair Value	$ 200	$ 246	[1]
[1]The Company’s equity securities included in other assets as of December 31, 2021 consisted of its investment in a privately held company obtained as partial consideration under the 2021 Enviro license agreement. The Company recognizes its private company equity securities at cost minus impairments, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. The $0.2 million investment was fully impaired during the year ended December 31, 2022 and recorded within other expense on the consolidated statements of operations.

Financial Instruments and Fai_5

Financial Instruments and Fair Value Measurements - Additional Information (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Short-term investments	$ 0	$ 0
Amount of transfers between levels	$ 0	$ 0

Financial Instruments and Fai_6

Financial Instruments and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Money market funds - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets:
Fair value, assets	$ 10,150	$ 5,003
Level 2
Assets:
Fair value, assets	$ 10,150	$ 5,003

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule Of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Public Utilities Inventory [Line Items]
Property and equipment	$ 243	$ 226
Less accumulated depreciation and amortization	(192)	(176)
Property and equipment, net	51	50
Computer And Office Equipment [Member]
Public Utilities Inventory [Line Items]
Property and equipment	203	186
Furniture and Fixtures [Member]
Public Utilities Inventory [Line Items]
Property and equipment	19	19
Leasehold Improvements [Member]
Public Utilities Inventory [Line Items]
Property and equipment	$ 21	$ 21

Balance Sheet Details - Additio

Balance Sheet Details - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Depreciation expense related to property and equipment	$ 16,000	$ 14,000	$ 12,000

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule Of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Public Utilities Inventory [Line Items]
Accounts payable	$ 3,923	$ 4,943
Accrued clinical related expenses	6,091	4,461
Accrued legal and accounting	299	842
Accrued long-term debt terminal interest	425	280
Current portion of operating lease liability	1,167	1,314
Other accruals	171	80
Total	11,107	10,753
Other Current Liabilities
Public Utilities Inventory [Line Items]
Current portion of operating lease liability	$ 198	$ 147

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details)	1 Months Ended			12 Months Ended
	Dec. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) Tranche $ / shares shares	May 31, 2018 USD ($)	Dec. 31, 2022 USD ($) shares
Debt Instrument [Line Items]
Maximum capital contribution	$ 30,000,000
Initial capital contribution from investors	$ 3,500,000
Percentage of closing fee amount	2%
Arbitration financing payable	$ 3,500,000			$ 3,280,000
Amount of initial capital contribution not required repay				$ 3,500,000
Conversion of warrants to purchase shares | shares				6,766,246
Proceeds from long-term debt				$ 9,960,000
Long-term debt				10,000,000
Current portion of debt discount				193,000
Runway Growth Finance Corp
Debt Instrument [Line Items]
Long-term debt				$ 10,000,000
Silicon Valley Bank
Debt Instrument [Line Items]
Conversion of warrants to purchase shares | shares				13,906
Loan And Security Agreement | Runway Growth Finance Corp
Debt Instrument [Line Items]
Long term debt, principal amount		$ 10,000
Proceeds from sale of debt and equity securities	$ 25,000,000
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan
Debt Instrument [Line Items]
Number of tranche | Tranche		3
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan A
Debt Instrument [Line Items]
Long term debt, principal amount		$ 10,000,000
Loan And Security Agreement | Runway Growth Finance Corp | Maximum | Term Loan
Debt Instrument [Line Items]
Long term debt, principal amount		35,000,000
Loan And Security Agreement | Runway Growth Finance Corp | Maximum | Term Loan B
Debt Instrument [Line Items]
Long term debt, principal amount		15,000,000
Loan And Security Agreement | Runway Growth Finance Corp | Maximum | Term Loan C
Debt Instrument [Line Items]
Long term debt, principal amount		$ 10,000,000
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan
Debt Instrument [Line Items]
Variable annual rate		5%
Prepayment fee (as a percent)		4.25%
Additional default interest rate payable to outstanding loan balances		5%
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan | On Or Prior To First Anniversary Date
Debt Instrument [Line Items]
Percentage of prepayment amount payable on outstanding amount		3%
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan | After First Anniversary Date But On Or Prior To Second Anniversary Date
Debt Instrument [Line Items]
Percentage of prepayment amount payable on outstanding amount		2%
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan | After Second Anniversary Date But Prior To Maturity Date
Debt Instrument [Line Items]
Percentage of prepayment amount payable on outstanding amount		1%
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan | Plus Rate
Debt Instrument [Line Items]
Variable annual rate		3.50%
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan A
Debt Instrument [Line Items]
Interest rate terms				The Company is obligated to make interest-only payments monthly in arrears through and including September 30, 2024 and thereafter monthly payments in arrears through the maturity date of September 1, 2026 equal to 1/24th of all outstanding principal plus accrued and unpaid interest.
Debt Instrument Closing Fee Amount		$ 50,000
Loan And Security Agreement | Runway Growth Finance Corp | Term Loan C
Debt Instrument [Line Items]
Closing fee amount percentage if any due and payable on applicable funding date		0.50%
Warrants | Runway Growth Finance Corp | Term Loan A
Debt Instrument [Line Items]
Conversion of warrants to purchase shares | shares		150,753
Exercise price (per share) | $ / shares		$ 1.99
Expiration date		Sep. 02, 2032
Two Thousand Eighteen Loan And Security Agreement | Silicon Valley Bank
Debt Instrument [Line Items]
Proceeds from long-term debt			$ 7,000,000
Final payment on payoff			300,000
Long-term debt			1,400,000
Current portion of debt discount			$ 9,000

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt and Unamortized Debt Discount Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-term debt	$ 10,000
Long-term debt, net of debt discount	10,000
Less current portion of long-term debt	(10,000)
Current portion of long-term debt	10,000
Current portion of debt discount	(193)
Current portion of long-term debt, net	$ 9,807	$ 1,391

Long-Term Debt - Schedule of Fu

Long-Term Debt - Schedule of Future Minimum Principal and Interest Payments (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 10,000
Runway Growth Finance Corp
Debt Instrument [Line Items]
2023	10,491
Long Term Debt Including Final Payment	10,491
Less interest and final payment	(491)
Long-term debt	$ 10,000

Long-Term Debt - Schedule of Ex

Long-Term Debt - Schedule of Exercisable Outstanding Warrants for Purchase of Common Stock Issued (Details)	Dec. 31, 2022 $ / shares shares
Debt Instrument [Line Items]
Conversion of warrants to purchase shares	6,766,246
Silicon Valley Bank
Debt Instrument [Line Items]
Conversion of warrants to purchase shares	13,906
Silicon Valley Bank | November 14, 2023 Through June 4, 2024
Debt Instrument [Line Items]
Conversion of warrants to purchase shares	3,874
Exercise price (per share) | $ / shares	$ 77.40
Silicon Valley Bank | January 25, 2024
Debt Instrument [Line Items]
Conversion of warrants to purchase shares	4,669
Exercise price (per share) | $ / shares	$ 51.40
Silicon Valley Bank | May 3, 2025
Debt Instrument [Line Items]
Conversion of warrants to purchase shares	5,363
Exercise price (per share) | $ / shares	$ 26.10

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Dec. 31, 2022 USD ($)
Research and development arrangement
Commitments and Contingencies
Potential milestone payable	$ 9.6

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	1 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($) Pre-fundedWarrant $ / shares shares	Jul. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 shares
Class Of Stock [Line Items]
Conversion of warrants to purchase shares			6,766,246
Warrants exercised				0
Cashless exercise of pre-funded warrants to purchase common stock			398,093
2022 Pre-Funded Warrants
Class Of Stock [Line Items]
Maximum percentage of holders ownership interest in common stock after exercise	19.99%
Number of amended pre-funded warrants | Pre-fundedWarrant	2
Common Stock
Class Of Stock [Line Items]
Issuance of common stock upon cashless exercise of pre-funded warrants			390,668
Common Stock | Direct Offerings
Class Of Stock [Line Items]
Net proceeds from common stock issuance | $	$ 3,900,000
Common Stock | IPO
Class Of Stock [Line Items]
Common stock issued and sold		3,926,702
Common stock purchase price per share | $ / shares		$ 3.82
Net proceeds from common stock issuance | $		$ 13,400,000
Common Stock | Capital on Demand Sales Agreement | Jones Trading Institutional Services LLC
Class Of Stock [Line Items]
Maximum aggregate value of stock to be sold | $			$ 50,000,000
Remaining amount available under the Sales Agreement | $			$ 45,700,000
Percentage of gross proceeds, required to pay for common stock sold through sales agreement			2.50%
Common Stock | 2022 Pre-Funded Warrants | Direct Offerings
Class Of Stock [Line Items]
Exercise price (per share) | $ / shares	$ 0.01
Common Stock | Purchase Price of $1.32 Per Share | Direct Offerings
Class Of Stock [Line Items]
Common stock issued and sold	841,989
Common stock purchase price per share | $ / shares	$ 1.32
Common Stock | Purchase Price of $1.31 Per Share | 2022 Pre-Funded Warrants | Direct Offerings
Class Of Stock [Line Items]
Common stock purchase price per share | $ / shares	$ 1.31
Conversion of warrants to purchase shares	2,205,018

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Outstanding Warrants for Purchase of Common Stock Issued (Details)	Dec. 31, 2022 $ / shares shares
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	6,766,246
January 25, 2024
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	4,669
Exercise price (per share) | $ / shares	$ 51.40
November 14, 2023 Through June 4, 2024
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	3,874
Exercise price (per share) | $ / shares	$ 77.40
March 27, 2024
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	1,369,602
Exercise price (per share) | $ / shares	$ 27
May 3, 2025
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	5,363
Exercise price (per share) | $ / shares	$ 26.10
August 27, 2030
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	1,889,513
Exercise price (per share) | $ / shares	$ 0.01
August 31, 2030
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	1,137,454
Exercise price (per share) | $ / shares	$ 0.01
June 21, 2032
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	2,205,018
Exercise price (per share) | $ / shares	$ 0.01
September 2, 2032
Class Of Stock [Line Items]
Conversion of warrants to purchase shares	150,753
Exercise price (per share) | $ / shares	$ 1.99

Stockholders' Equity - (SBC) -

Stockholders' Equity - (SBC) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
	Jan. 02, 2015	Dec. 31, 2015	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock Plans
Shares of common stock reserved for future issuance			9,406,708	6,340,378
Stock Option
Stock options, additional disclosures
Weighted-average grant date fair value (in dollars per share)			$ 1.65	$ 6.05	$ 2.62
Share price (in dollar per share)			$ 1.49
Proceeds from exercise of stock options				$ 21,000
Shares Options, Exercises in Period			0	3,727
Total intrinsic value of options exercised				$ 4,000
Total fair value of options vested during the year			$ 2.6	0.8	$ 1
Share-based compensation
Unrecognized compensation cost			$ 3.6	$ 4
Unrecognized compensation cost, period of recognition			2 years 6 months	2 years 8 months 12 days
Stock Option | Year One
Stock Plans
Grants vesting period			1 year
Grants vesting (as a percent)			25%
Stock Option | Thereafter
Stock Plans
Grants vesting period			36 months
ESPP
Stock Plans
Shares of common stock reserved for future issuance	18,346
Percentage of total number of shares of common stock outstanding	1%
Stock options, additional disclosures
Number of shares that could potentially be issued	250,000
Share-based compensation
Percentage of eligible compensation	15%
2015 Equity Incentive Plan
Stock Plans
Maximum term of options granted			10 years
Shares of common stock reserved for future issuance	80,103		150,335	115,990
Percentage of total number of shares of common stock outstanding	5%
Additional shares to be used exclusively for grant for Inducement awards		200,000

Stockholders' Equity- Summary o

Stockholders' Equity- Summary of Stock Option Activity (Details) - Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of Options
Balance (in shares)	1,308,360
Granted (in shares)	937,950
Exercised (in shares)	0	(3,727)
Balance (in shares)	2,246,310	1,308,360
Weighted-Average Exercise Price
Balance (in dollars per share)	$ 13.99
Granted (in dollars per share)	2.20
Balance (in dollars per share)	$ 9.07	$ 13.99

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Company's Outstanding Stock Option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of Options
Number of shares, options vested and expected to vest	2,246,310	1,308,360
Stock Option
Number of Options
Number of shares, options outstanding	2,246,310	1,308,360
Number of shares, options vested and expected to vest	2,246,310
Number of shares, options exercisable	860,683
Aggregate intrinsic value, options outstanding	$ 23,168
Aggregate intrinsic value, options vested and expected to vest	23,168
Aggregate intrinsic value, options exercisable	$ 1,480
Weighted-Average Exercise Price
Weighted-average exercise price, options outstanding (in dollars per share)	$ 9.07	$ 13.99
Weighted-average exercise price, options vested and expected to vest (in dollars per share)	9.07
Weighted-average exercise price, options exercisable (in dollars per share)	$ 17.36
Weighted-average remaining contractual term, options outstanding (in years)	8 years
Weighted-average remaining contractual term, options vested and expected to vest (in years)	8 years
Weighted-average remaining contractual term, options exercisable (in years)	6 years 9 months

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Weighted-Average Assumptions Fair Value of the Employee Stock Option Grants (Details) - Stock Option	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Risk-free interest rate	1.90%	0.80%	1.20%
Expected volatility	89.80%	90.30%	85.80%
Expected term (in years)	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days
Expected dividend yield	0%	0%	0%

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Stock based compensation expense	$ 2,041	$ 1,775	$ 1,034
Research and development
Class Of Stock [Line Items]
Stock based compensation expense	830	628	386
General and administrative
Class Of Stock [Line Items]
Stock based compensation expense	$ 1,211	$ 1,147	$ 648

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Common Stock Reserved For Future Issuance (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Jan. 02, 2015
Stock Plans
Shares of common stock reserved for future issuance	9,406,708	6,340,378
Number of shares, options vested and expected to vest	2,246,310	1,308,360
2015 Equity Incentive Plan
Stock Plans
Shares of common stock reserved for future issuance	150,335	115,990	80,103
Common Stock. | Warrants
Stock Plans
Shares of common stock reserved for future issuance	6,766,246	4,810,409
ESPP
Stock Plans
Shares of common stock reserved for future issuance			18,346
Shares of common stock reserved for future issuance	243,817	105,619

Collaborations - Additional Inf

Collaborations - Additional Information (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2018 USD ($) antibody	Dec. 31, 2022 USD ($)	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Termination fee	$ 9,000,000
Bispecific Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty on net sales		50%
Bispecific Agreement | I-Mab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum number of proprietary bispecific antibodies under development | antibody	5
Number of biological targets | antibody	2
Bispecific Agreement | I-Mab | Before IND
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One time upfront payment fee	$ 10,000,000
Development and regulatory based on milestone payments	90,000,000
Potential milestones payments received	250,000,000
Bispecific Agreement | I-Mab | After IND Before Phase 1a
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One time upfront payment fee	25,000,000
Development and regulatory based on milestone payments	125,000,000
Potential milestones payments received	250,000,000
Bispecific Agreement | I-Mab | After Phase 1a and Before Phase 2
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One time upfront payment fee	50,000,000
Development and regulatory based on milestone payments	250,000,000
Potential milestones payments received	250,000,000
Bispecific Agreement | I-Mab | After Phase 2
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One time upfront payment fee	80,000,000
Development and regulatory based on milestone payments	420,000,000
Potential milestones payments received	$ 250,000,000
Collaboration Agreements | I-Mab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Consideration exchanged for assets acquired		$ 0
Value given to assets acquired		0
TJ4309 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of cost bearing	40%
TJ4309 Agreement | I-Mab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of cost bearing	60%
Potential payments receivable		$ 340,000,000
Termination of agreement upon completion of clinical trial	90 days
TJ4309 Agreement | I-Mab | First Phase Clinical Trial
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Termination fee	$ 9,000,000
TJ4309 Agreement | I-Mab | First Phase Two Clinical Trial
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Termination fee	$ 15,000,000
North America | Bispecific Agreement | I-Mab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum period of selecting candidates for development and commercialization	5 years
North America | Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Commercial sale			10 years

Leases - Additional Information

Leases - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Non-cancelable operating lease expiration term		2021-08
Non Cancelable Operating Lease Term To Be Extended		2027-04
Operating lease expense	$ 400,000		$ 400,000	$ 400,000
Irrevocable letter of credit provided to lessor		$ 66,949

Leases - Supplemental cash flow

Leases - Supplemental cash flow information related to operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Cash paid within operating cash flows	$ 285	$ 461	$ 442
ROU assets recognized in exchange for new lease obligations		$ 1,117

Leases - Supplemental balance s

Leases - Supplemental balance sheet information related to operating leases (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Reported as:
Other assets (ROU asset)	$ 1,123	$ 1,325
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Current portion of operating lease liability	$ 1,167	$ 1,314
Weighted average remaining lease term	4 years 3 months 18 days	5 years 3 months 18 days
Weighted average discount rate	11.30%	11.30%
Accounts payable and accrued expenses (lease liability)
Reported as:
Current portion of operating lease liability	$ 198	$ 147
Other long-term liabilities (lease liability)
Reported as:
Current portion of operating lease liability	$ 969	$ 1,167

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2023	$ 320
2024	334
2025	349
2026	365
2027	123
Total lease payments	1,491
Less imputed interest	(324)
Current portion of operating lease liability	$ 1,167	$ 1,314

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Effective Tax Rate and Federal Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of effective tax rate and federal statutory tax rate
Federal income taxes	$ (6,118)	$ (6,020)	$ (3,523)
State income taxes, net of federal benefit	(1,962)	(1,889)	(1,084)
Permanent items	81	93	104
Uncertain tax positions	2,477	494	1,224
Research and development credits	(2,119)	(1,661)	(555)
Other, net	125	28
Stock compensation	78	203	113
Change in valuation allowance	7,438	8,752	3,721
Provision for income taxes	$ 0	$ 0	$ 0

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of deferred tax assets and deferred tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 50,779	$ 47,633
Research and development and Orphan Drug credits	11,928	10,472
Depreciation and amortization	236	247
Right-of-use liability	245	276
Section 174 capitalized research expense	2,503
Other, net	1,906	1,573
Total deferred tax assets	67,597	60,201
Right-of-use asset	(236)	(278)
Total deferred tax liabilities	(236)	(278)
Total net deferred	67,361	59,923
Valuation allowance	(67,361)	(59,923)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Carryforwards
Net change in the total valuation allowance	$ 7,400,000	$ 8,800,000	$ 3,700,000
NOL carryforward	$ 111,100,000
NOL carryforward available to offset future taxable income, percentage	80%
Accrual for interest or penalties for unrecognized tax benefits	$ 0	$ 0
Income tax interest or penalties expense for unrecognized tax benefits	$ 0
Orphan Drug tax credit
Carryforwards
Credit carryforward begin to expire	2036
Minimum
Carryforwards
Percent of ownership	50%		50%
Federal
Carryforwards
NOL carryforward	$ 194,300,000
NOL carryforward begin to expire	2030
Federal | Research and Development and Orphan Drug Tax Credit Carryforwards
Carryforwards
Credit carryforward	$ 13,700,000
Federal | Research and Development Tax Credit
Carryforwards
Credit carryforward begin to expire	2031
Federal | Minimum
Carryforwards
Research and development expenditure amortization period	5 years
Foreign
Carryforwards
Research and development expenditure amortization period	15 years
California
Carryforwards
NOL carryforward	$ 144,500,000
NOL carryforward begin to expire	2033
California | Research and Development Tax Credit
Carryforwards
Credit carryforward	$ 3,000,000

Income Taxes - Schedule of Chan

Income Taxes - Schedule of Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Unrecognized tax benefits
Balance, beginning of period	$ 7,117	$ 6,610	$ 5,092
Change related to prior year positions	(5)	1
Increase related to current year positions	2,984	506	1,518
Balance, end of period	$ 10,096	$ 7,117	$ 6,610

401(k) Plan - Additional Inform

401(k) Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Pension and Other Postretirement Plans Disclosure
Defined contribution, plan name	us-gaap:RetirementPlanNameOtherMember	us-gaap:RetirementPlanNameOtherMember	us-gaap:RetirementPlanNameOtherMember
Defined contribution amount	$ 0.2	$ 0.1	$ 0.1