TRACON Pharmaceuticals (TCON) 10-K 15 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 11, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
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			$ 99
Entity Common Stock, Shares Outstanding		19,616,571
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

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 24,072	$ 32,131
Short-term investments	0	3,999
Prepaid and other assets	864	784
Total current assets	24,936	36,914
Property and equipment, net	50	16
Other assets	1,571	508
Total assets	26,557	37,438
Current liabilities:
Accounts payable and accrued expenses	10,753	6,235
Accrued compensation and related expenses	1,532	1,590
Long-term debt, current portion	1,391	2,718
Total current liabilities	13,676	10,543
Other long-term liabilities	1,167	432
Long-term debt, less current portion		1,391
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.001 par value, authorized shares — 10,000,000 at December 31, 2021 and December 31, 2020; issued and outstanding shares — none
Common stock, $0.001 par value; authorized shares — 40,000,000 at December 31, 2021 and December 31, 2020; issued and outstanding shares — 19,445,903 and 15,478,787 at December 31, 2021 and December 31, 2020, respectively	19	15
Additional paid-in capital	219,471	204,166
Accumulated deficit	(207,776)	(179,109)
Total stockholders’ equity	11,714	25,072
Total liabilities and stockholders’ equity	$ 26,557	$ 37,438

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
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	19,445,903	15,478,787
Common stock, shares outstanding	19,445,903	15,478,787

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
License revenue	$ 346	$ 0	$ 0
Type of Revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 11,146	$ 8,198	$ 14,530
General and administrative	17,547	8,025	7,766
Total operating expenses	28,693	16,223	22,296
Loss from operations	(28,347)	(16,223)	(22,296)
Other income (expense):
Interest expense, net	(318)	(545)	(386)
Other (expense) income, net	(2)	(7)	8
Total other expense	(320)	(552)	(378)
Net loss	$ (28,667)	$ (16,775)	$ (22,674)
Net loss per share, basic and diluted	$ (1.66)	$ (1.87)	$ (7.47)
Weighted-average shares outstanding, basic and diluted	17,252,637	8,984,148	3,034,299

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2018	$ 21,442	$ 3	$ 161,099	$ (139,660)
Balance (in Shares) at Dec. 31, 2018		2,987,182
Increase (Decrease) in Shareholders' Equity
Issuance of common stock under equity plans	12		12
Issuance of common stock under equity plans (in shares)		9,270
Stock-based compensation expense	1,624		1,624
Issuances of common stock, net of offering costs	2,294	$ 1	2,293
Issuances of common stock, net of offering costs (in shares)		1,054,735
Net loss	(22,674)			(22,674)
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
Issuances 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	$ 40,414	149
Stock-based compensation expense	1,775		1,775
Issuances 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
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

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (28,667)	$ (16,775)	$ (22,674)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,775	1,034	1,624
Common stock issued for services		126
Depreciation and amortization	14	12	22
Noncash interest	61	123	234
Amortization of debt discount	21	43	81
Amortization of premium/discount on short-term investments	(1)	(1)	(52)
Lease asset amortization and liability accretion, net	(73)	(25)	(6)
Equity ownership license revenue	(246)
Changes in assets and liabilities:
Prepaid expenses and other assets	(80)	64	651
Accounts payable and accrued expenses	4,683	(1,878)	(3,421)
Accrued compensation and related expenses	(58)	235	(109)
Net cash used in operating activities	(22,571)	(17,042)	(23,650)
Cash flows from investing activities
Purchase of property and equipment	(48)	(5)
Purchases of available-for-sale short-term investments		(3,998)	(4,980)
Proceeds from the maturity of available-for-sale short-term investments	4,000		19,000
Net cash provided by (used in) investing activities	3,952	(4,003)	14,020
Cash flows from financing activities
Repayment of long-term debt	(2,800)	(1,400)	(1,400)
Proceeds from sale of common stock and warrants, net of offering costs	13,211	38,162	2,294
Proceeds from issuance of common stock under equity plans, net of tax withholdings	149	2	12
Net cash provided by financing activities	10,560	36,764	906
Change in cash and cash equivalents	(8,059)	15,719	(8,724)
Cash and cash equivalents at beginning of period	32,131	16,412	25,136
Cash and cash equivalents at end of period	24,072	32,131	16,412
Supplemental disclosure of cash flow information
Interest paid	$ 266	$ 443	612
Supplemental schedule of noncash investing and financing activities
Issuance of common stock in connection with common stock purchase agreement			$ 450

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
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 ex-U.S. 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, 2021, 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, 2021, the Company had an accumulated deficit of $207.8 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, 2021, the Company had cash and cash equivalents of $24.1 million. 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 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. In addition, the Company may fund its losses from operations through the common stock purchase agreement the Company entered into with Aspire Capital in October 2019, as amended in April 2020, for the purchase of up to $15.0 million over the 30 month period $5.4 million of which 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. The Company has experienced temporary closures of its offices in light of state and local orders and most of its employees continue to work remotely. In addition, the Company’s employees have not been able to conduct normal business travel, in particular as part of business development activities or in-person monitoring of clinical trial sites. Potential further impacts to the Company’s business include, but are not limited to, additional closures of its facilities or those of its vendors, continued disruptions or restrictions on its employees’ ability to travel, disruptions to or delays in ongoing clinical trials, third-party manufacturing supply and other operations, the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, interruptions or delays in the operations of the U.S. Food and Drug Administration or other regulatory authorities, and the Company’s ability to raise capital and conduct business development activities . 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 Cash and Cash 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 Update (ASU) No. 2014-09, Revenue from Contracts with Customers, the Company performs the following five steps in determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of these agreements: (i) identification of the contract(s) with a customer; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services transferred to the customer. Once a contract is determined to be within the scope of Accounting Standards Codification 606, Revenue from Contracts with Customers, at contract inception, the Company assesses the goods or services promised within the contract to determine those that are performance obligations and assesses whether each promised good is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when, or as, the performance obligation is satisfied . 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, 2021, 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, 2021 2020 2019 Warrants to purchase common stock 4,810,409 4,810,409 1,561,903 Common stock options and restricted stock units 1,308,360 601,481 370,391 ESPP shares 3,258 5,349 1,322 Total 6,122,027 5,417,239 1,933,616 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.

Investments, Cash Equivalents a

Investments, Cash Equivalents and Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Investments, Cash Equivalents and Fair Value Measurements	2. Investments, Cash Equivalents and Fair Value Measurements At December 31, 2021, the Company had no short-term investments, and at December 31, 2020, the Company’s short-term investments consisted of U.S. treasury securities. 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. Cash equivalents, which are classified as equity securities, short-term investments, which are classified as available-for-sale securities, and equity securities consisted of the following (in thousands): December 31, 2021 December 31, 2020 Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Money market funds included in cash equivalents $ 5,003 $ — $ — $ 5,003 $ 1,002 $ — $ — $ 1,002 U.S. treasury securities included in short-term investments — — — — 3,999 — — 3,999 Equity securities included in other assets (1) 246 — — 246 — — — — $ 5,249 $ — $ — $ 5,249 $ 5,001 $ — $ — $ 5,001 (1) The Company’s equity securities included in other assets consisted of its investment in a privately held company. 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. No such impairments or changes were noted for any period 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, 2021 Money market funds $ 5,003 $ — $ 5,003 $ — At December 31, 2020 Money market funds and U.S. treasury securities $ 5,001 $ — $ 5,001 $ —

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2021
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, 2021 2020 Computer and office equipment $ 186 $ 138 Furniture and fixtures 19 19 Leasehold improvements 21 21 226 178 Less accumulated depreciation and amortization (176 ) (162 ) $ 50 $ 16 Depreciation expense related to property and equipment totaled approximately $14,000, $12,000 and $22,000 for the years ended December 31, 2021, 2020 and 2019, respectively. Accounts payable and accrued expenses Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2021 2020 Accounts payable $ 4,943 $ 1,725 Accrued clinical related expenses 4,461 3,559 Accrued legal and accounting 842 37 Other accruals 360 496 Current portion of operating lease liability 147 418 $ 10,753 $ 6,235

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-Term Debt	4. Long-Term Debt Long-term debt and unamortized debt discount balances were as follows (in thousands): December 31, 2021 2020 Long-term debt $ 1,400 $ 4,200 Less debt discount, net of current portion — (9 ) Long-term debt, net of debt discount 1,400 4,191 Less current portion of long-term debt (1,400 ) (2,800 ) Long-term debt, net of current portion $ — $ 1,391 Current portion of long-term debt $ 1,400 $ 2,800 Current portion of debt discount (9 ) (82 ) Current portion of long-term debt, net $ 1,391 $ 2,718 In May 2018, the Company entered into a third amendment to its Amended and Restated Loan and Security Agreement with Silicon Valley The 2018 Amended SVB Loan provides for interest to be paid at a rate of 9.0 due monthly through June 30, 2019. Thereafter, in addition to interest accrued during such period, the monthly payments include an amount equal to the outstanding principal at June 30, 2019 divided by 30 months . In April 2020, the Company entered into a deferral agreement with SVB (the Deferral Agreement) for an interest-only payment period of six months, with a corresponding six month extension to the maturity date to June 2022 . All other key terms and conditions of the 2018 Amended SVB Loan remained unchanged and the transaction was accounted for as a debt modification. At maturity (or earlier prepayment), the Company is required to make a final payment equal to 4.0% of the original principal amount borrowed. The 2018 Amended SVB Loan is collateralized by substantially all of the Company’s assets, other than the Company’s intellectual property, and contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. Should an event of default occur, including the occurrence of a material adverse change, the Company could be liable for immediate repayment of all obligations under the 2018 Amended SVB Loan. As of December 31, 2021, the Company was in compliance with all covenants and conditions of the 2018 Amended SVB Loan. In connection with the 2018 Amended SVB Loan, the Company issued SVB a warrant to purchase 5,363 shares of its common stock at an exercise price of $26.10 per share. The warrant is fully exercisable and expires on May 3, 2025. The fair value of the warrant and the final payment related to the 2018 Amended SVB Loan were recorded as debt discounts and are being amortized to interest expense using the effective interest method over the term of the debt, in addition to the remaining unamortized discounts related to the 2017 Amended SVB Loan. At December 31, 2021, 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 May 13, 2022 1,841 $ 108.60 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 15,747 Future minimum principal and interest payments under the 2018 Amended SVB Loan, including the final payment, as of December 31, 2021 are as follows (in thousands): 2022 $ 1,717 1,717 Less interest and final payment (317 ) Long-term debt $ 1,400

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
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, 2021, potential future milestone payments under these agreements totaled an aggregate of $9.6 million.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Stockholders Equity Note [Abstract]
Stockholders' Equity	6. Stockholders’ Equity Sales of Common Stock 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. In December 2020, the Company issued and sold 1,612,844 shares of its common stock at an average purchase price of $8.84 per share for net proceeds of $13.6 million in two registered direct offerings with certain institutional investors. In August 2020, the Company issued and sold 2,633,838 shares of its common stock at an average purchase price of $1.66 per share and warrants to purchase 3,429,696 shares of its common stock at an average purchase price of $1.64 per warrant share with an exercise price of $0.01 per share (the 2020 Pre-Funded Warrants) for net proceeds of approximately $10.0 million in a private placement with multiple accredited institutional health care focused funds. In accordance with their terms, the 2020 Pre-Funded Warrants may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99% of the Company’s total shares outstanding following such exercise. The 2020 Pre-Funded Warrants were recorded as a component of stockholders’ equity within additional paid-in capital on the consolidated balance sheets. In October 2019, the Company entered into a Common Stock Purchase Agreement, which was amended in April 2020 (the 2019 Purchase Agreement), with Aspire Capital which provides that, upon the terms and subject to the conditions and limitations set forth in the 2019 Purchase Agreement, Aspire Capital is committed to purchase up to an aggregate of $15.0 million of shares of the Company’s common stock solely at the Company’s request from time to time during the 30 month period of the agreement and at prices based on the market price at the time of each sale. In consideration for entering into the 2019 Purchase Agreement and concurrently with the execution of the 2019 Purchase Agreement, the Company issued 142,658 shares of its common stock to Aspire Capital. As of December 31, 2021, the Company had sold an aggregate 4.8 million shares of common stock under the 2019 Purchase Agreement with Aspire Capital for net proceeds of $9.6 million. At-The-Market Issuance Sales Agreement In December 2020, the Company entered into a Capital on Demand TM In connection with entering into the JonesTrading Sales Agreement in December 2020, the Company terminated its prior Capital on Demand™ sales agreement, dated September 6, 2018, with JonesTrading and no further sales of common stock will occur under the prior sales agreement. As of December 31, 2021, the Company had sold an aggregate 3.0 million shares of common stock for net proceeds of $7.1 million under the prior sales agreement with JonesTrading. Common Stock Warrants As of December 31, 2021 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price May 13, 2022 1,841 $ 108.60 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 March 27, 2025 176,554 $ 0.10 May 3, 2025 5,363 $ 26.10 August 27, 2027 1,889,513 $ 0.01 August 31, 2027 1,358,993 $ 0.01 4,810,409 During the year ended December 31, 2021, no warrants were exercised. During the year ended December 31, 2020, 181,190 pre-funded warrants were exercised for net proceeds of $2,000. 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, 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). Restricted Stock Units In 2016, the Company issued RSUs to employees and members of the Company’s board of directors under the 2015 Plan. The total grant-date fair value of RSUs that vested during the years ended December 31, 2021 and 2020 was $0 and $0.3 million, respectively. As of December 31, 2021 and 2020, there were no outstanding RSUs. Stock Options Stock option activity under all Plans is summarized as follows: Weighted- Number of Average Options Exercise Price Balance at December 31, 2020 601,481 $ 21.50 Granted 781,570 8.12 Exercised (3,727 ) 5.64 Forfeited (70,964 ) 13.51 Balance at December 31, 2021 1,308,360 $ 13.99 Information about the Company’s outstanding stock options as of December 31, 2021 is as follows: Weighted- Average Weighted- Remaining Average Contractual Aggregate Number of Exercise Term Intrinsic Shares Price (in years) Value Options outstanding 1,308,360 $ 13.99 8.19 $ 47,403 Options vested and expected to vest 1,308,360 $ 13.99 8.19 $ 47,403 Options exercisable 401,148 $ 28.40 6.41 $ 30,870 The weighted-average grant date fair value per share of employee option grants during the years ended December 31, 2021, 2020 and 2019 was $6.05, $2.62 and $5.55, respectively. The aggregate intrinsic value used in the above table of options at December 31, 2021 is based on the Company’s closing market price per common share on December 31, 2021 of $2.77. 3,727 stock options were exercised during the year ended December 31, 2021 for proceeds of $21,000 and no stock options were exercised during the years ended December 31, 2020 and 2019. 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, 2021, 2020 and 2019 was $0.8 million, $1.0 million and $1.5 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, 2021, 2020 and 2019 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, 2021 2020 2019 Risk-free interest rate 0.8 % 1.2 % 2.6 % Expected volatility 90.3 % 85.8 % 81.1 % 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, 2021 2020 2019 Research and development $ 628 $ 386 $ 776 General and administrative 1,147 648 848 $ 1,775 $ 1,034 $ 1,624 As of December 31, 2021 and 2020, the unrecognized compensation cost related to outstanding time-based options was $4.0 million and $1.3 million, respectively, and is expected to be recognized as expense over approximately 2.7 years and 2.6 years, respectively. Common Stock Reserved for Future Issuance Common stock reserved for future issuance was as follows: December 31, 2021 2020 Common stock warrants 4,810,409 4,810,409 Common stock options and restricted stock units granted and outstanding 1,308,360 601,481 Awards available under the 2015 Plan 115,990 57,468 Shares available under the Employee Stock Purchase Plan 105,619 105,614 6,340,378 5,574,972

Collaboration

Collaboration	12 Months Ended
	Dec. 31, 2021
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 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 trials 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 I n November 2018, the Company and I-Mab Biopharma (I-Mab) entered into separate strategic collaboration and clinical trial agreements (the I-Mab Collaboration Agreements ) for the development of programs for multiple immuno-oncology product candidates , including I-Mab’s proprietary CD73 antibody TJ004309 (the TJ004309 Agreement) as well as up to five proprietary bispecific antibodies currently under development by I-Mab (the Bispecific Agreement). 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 out-licenses the 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 certain territories outside of Greater China. In the event that I-Mab commercializes The TJ004309 TJ004309 TJ004309 TJ004309 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 candidates within a five-year period for development and commercialization in North America. 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 (ABL Bio License 1 and ABL Bio License 2). Under ABL Bio License 1, I-Mab granted to ABL Bio exclusive, worldwide (excluding Greater China), royalty International Chamber of Commerce before the Tribunal. The Tribunal held a hearing on the merits in February 2022. As of the date of this Annual Report, the Bispecific Agreement dispute remains under consideration by the Tribunal, and the Company expects their decision in 2022. The claims under the arbitration under the Bispecific Agreement are substantial and complex and the result is inherently uncertain, and the C ompany cannot currently estimate the likely outcome of the dispute under the Bispecific Agreement . The dispute with I-Mab has caused and could continue to cause the Company to incur significant costs . Janssen In September 2016, the Company entered into a license and option agreement with Janssen (the License and Option Agreement) under which Janssen granted the Company a license to technology and intellectual property to develop, manufacture and commercialize two compounds: a small molecule inhibitor of androgen receptor and androgen receptor mutations (the AR Mutant Program or TRC253) which is intended for the treatment of men with prostate cancer, and an inhibitor of NF-kB inducing kinase (the NIK Program or TRC694). Following completion of the pre-clinical development of TRC694, the Company determined the compound did not warrant further development and, in February 2019, issued written notice to terminate the License and Option Agreement with respect to the NIK Program and returned TRC694 and all rights thereto to Janssen. Following completion of the TRC253 Phase 1/2 trial, the Company determined commercialization of TRC253 in prostate cancer in the United States was not viable and, in May 2021, issued written notice to terminate the License and Option Agreement with respect to the AR Mutant Program and returned TRC253 and all rights thereto to Janssen. No consideration was exchanged for these assets on the acquisition date. Given the early preclinical stage of development of these assets and the low likelihood of success of development through regulatory approval on the acquisition date, no value was previously assigned to these assets in the accompanying consolidated balance sheets. Enviro and Kairos In May 2021, the Company entered into a license and supply agreement with Enviro Therapeutics Inc. (Enviro) and Kairos Pharma, Ltd. (Kairos) under which the Company granted to Enviro access to inactive IND filings for TRC105 in the United States, ownership of existing supplies of TRC105 drug product, and assignment of the Company’s patent rights to CD105 technologies, which includes the TRC105 antibody. In consideration of the transfer and assignment, the Company received a one-time, non-refundable, non-creditable upfront payment in the amount of $0.1 million and equity ownership in Enviro, subject to certain specified reductions. In addition, the Company received anti-dilution protection of its equity ownership in Enviro, subject to certain specified reductions, and is eligible to receive up to a total of $1.0 million in milestone payments upon the achievement of specified financing events, and a single-digit royalty on worldwide net sales of TRC105. Under the terms of the agreement, Enviro has sole responsibility for funding, developing, seeking regulatory approval for and commercializing TRC105 product candidates. Enviro has the right to grant sublicenses to affiliates and third-party collaborators and in the event Enviro sublicenses any of its rights under the agreement, Enviro would be obligated to pay the Company a single-digit percentage of all consideration received under such sublicense. The Company assessed this agreement and identified multiple promised goods and services, which included at contract inception: (1) assignment of patent rights to CD105 technologies, (2) access to inactive IND filings for TRC105 in the United States, and (3) transfer of ownership of TRC105 drug product. All performance obligations were satisfied by December 31, 2021, which completed the Company’s obligations under the terms of the agreement. December 31, 2021

Leases

Leases	12 Months Ended
	Dec. 31, 2021
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 year s ended December 31, 20 2 1 , 20 20 and 201 9 . As of December 31, 2021 , 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, 2021 2020 2019 Cash paid within operating cash flows $ 461 $ 442 $ 423 ROU assets recognized in exchange for new lease obligations $ 1,117 $ — $ 1,143 Supplemental balance sheet information related to operating leases was as follows (in thousands, except lease term and discount rate): December 31, 2021 2020 Reported as: Other assets (ROU asset) $ 1,325 $ 508 Accounts payable and accrued expenses (lease liability) $ 147 $ 418 Other long-term liabilities (lease liability) 1,167 152 Total lease liabilities $ 1,314 $ 570 Weighted average remaining lease term 5.3 1.3 Weighted average discount rate 11.3% 11.3% As of December 31, 2021 2022 $ 285 2023 320 2024 334 2025 349 2026 365 2027 123 Total lease payments 1,776 Less imputed interest (462 ) Total operating lease liabilities $ 1,314 Under the terms of the lease agreement, the Company provided the lessor with an irrevocable letter of credit in the amount of $175,000. 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, 2021
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, 2021 2020 2019 Federal income taxes $ (6,020 ) $ (3,523 ) $ (4,761 ) State income taxes, net of federal benefit (1,889 ) (1,084 ) (1,381 ) Permanent items 93 104 149 Uncertain tax positions 494 1,224 1,828 Research and development credits (1,661 ) (555 ) (1,253 ) Other, net 28 — (75 ) Stock compensation 203 113 395 Change in valuation allowance 8,752 3,721 5,098 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, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 47,633 $ 40,103 Research and development credits and Orphan Drug Credit 10,472 9,321 Depreciation and amortization 247 258 Right-of-use liability 276 120 Other, net 1,573 1,476 Total deferred tax assets 60,201 51,278 Right-of-use asset (278 ) (107 ) Total deferred tax liabilities (278 ) (107 ) Total net deferred 59,923 51,171 Valuation allowance (59,923 ) (51,171 ) Net deferred tax assets $ — $ — The Company has net deferred tax assets relating primarily to net operating loss (NOL) carryforwards, research and development and Orphan Drug tax credit carryforwards. 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, 2021, 2020 and 2019 was $8.8 million, $3.7 million and $5.1 million, respectively. At December 31, 2021, the Company had federal and California NOL carryforwards of approximately $179.4 million and $144.4 million, respectively. The federal and California NOL carryforwards will begin to expire in 2030, unless previously utilized. The federal NOL generated after 2017 of $96.2 million will carryforward indefinitely. In response to the COVID-19 global pandemic, the CARES Act was enacted on March 27, 2020, to provide aid and economic stimulus to the economy. Among other provisions, the CARES Act eliminates the 80% NOL limitation for tax years 2018 to 2021, and allows NOLs generated in those years to be carried back for five years. The CARES Act does not have a significant impact on the Company's financial position, results of operations or cash flows. At December 31, 2021, the Company also had federal and California research and development and Orphan Drug credit carryforwards of approximately $11.8 million and $2.7 million, respectively. The federal research and development and Orphan Drug credit carryforwards will begin expiring in 2031 unless previously utilized. The California research credit will carry forward indefinitely under current law. Pursuant to Sections 382 and 383 of the Internal Revenue Code (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, 2018 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 changes in the Company’s unrecognized tax benefits are summarized as follows (in thousands): Balance at December 31, 2018 2,859 Change related to prior year positions — Increase related to current year positions 2,233 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 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, 2021 and 2020 and has not recognized interest or penalties in the accompanying consolidated statements of operations for the three years in the period ended December 31, 2021. 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, 2021
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, 2021, 2020 and 2019 totaled $0.1 million, $0.1 million and $0.2 million, respectively.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
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 ex-U.S. 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, 2021, 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, 2021, the Company had an accumulated deficit of $207.8 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, 2021, the Company had cash and cash equivalents of $24.1 million. 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 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. In addition, the Company may fund its losses from operations through the common stock purchase agreement the Company entered into with Aspire Capital in October 2019, as amended in April 2020, for the purchase of up to $15.0 million over the 30 month period $5.4 million of which 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. The Company has experienced temporary closures of its offices in light of state and local orders and most of its employees continue to work remotely. In addition, the Company’s employees have not been able to conduct normal business travel, in particular as part of business development activities or in-person monitoring of clinical trial sites. Potential further impacts to the Company’s business include, but are not limited to, additional closures of its facilities or those of its vendors, continued disruptions or restrictions on its employees’ ability to travel, disruptions to or delays in ongoing clinical trials, third-party manufacturing supply and other operations, the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, interruptions or delays in the operations of the U.S. Food and Drug Administration or other regulatory authorities, and the Company’s ability to raise capital and conduct business development activities .
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
Cash and Cash Equivalents	Cash and Cash 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 Update (ASU) No. 2014-09, Revenue from Contracts with Customers, the Company performs the following five steps in determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of these agreements: (i) identification of the contract(s) with a customer; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services transferred to the customer. Once a contract is determined to be within the scope of Accounting Standards Codification 606, Revenue from Contracts with Customers, at contract inception, the Company assesses the goods or services promised within the contract to determine those that are performance obligations and assesses whether each promised good is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when, or as, the performance obligation is satisfied . 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, 2021, 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, 2021 2020 2019 Warrants to purchase common stock 4,810,409 4,810,409 1,561,903 Common stock options and restricted stock units 1,308,360 601,481 370,391 ESPP shares 3,258 5,349 1,322 Total 6,122,027 5,417,239 1,933,616
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, 2021
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, 2021 2020 2019 Warrants to purchase common stock 4,810,409 4,810,409 1,561,903 Common stock options and restricted stock units 1,308,360 601,481 370,391 ESPP shares 3,258 5,349 1,322 Total 6,122,027 5,417,239 1,933,616

Investments, Cash Equivalents_2

Investments, Cash Equivalents and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Available-for-sale Securities and Equity Securities	Cash equivalents, which are classified as equity securities, short-term investments, which are classified as available-for-sale securities, and equity securities consisted of the following (in thousands): December 31, 2021 December 31, 2020 Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Cost Unrealized Gain Unrealized (Loss) Estimated Fair Value Money market funds included in cash equivalents $ 5,003 $ — $ — $ 5,003 $ 1,002 $ — $ — $ 1,002 U.S. treasury securities included in short-term investments — — — — 3,999 — — 3,999 Equity securities included in other assets (1) 246 — — 246 — — — — $ 5,249 $ — $ — $ 5,249 $ 5,001 $ — $ — $ 5,001
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, 2021 Money market funds $ 5,003 $ — $ 5,003 $ — At December 31, 2020 Money market funds and U.S. treasury securities $ 5,001 $ — $ 5,001 $ —

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule Of Property and Equipment	Property and equipment consisted of the following (in thousands): December 31, 2021 2020 Computer and office equipment $ 186 $ 138 Furniture and fixtures 19 19 Leasehold improvements 21 21 226 178 Less accumulated depreciation and amortization (176 ) (162 ) $ 50 $ 16
Schedule Of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2021 2020 Accounts payable $ 4,943 $ 1,725 Accrued clinical related expenses 4,461 3,559 Accrued legal and accounting 842 37 Other accruals 360 496 Current portion of operating lease liability 147 418 $ 10,753 $ 6,235

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-term debt and unamortized debt discount balances	Long-term debt and unamortized debt discount balances were as follows (in thousands): December 31, 2021 2020 Long-term debt $ 1,400 $ 4,200 Less debt discount, net of current portion — (9 ) Long-term debt, net of debt discount 1,400 4,191 Less current portion of long-term debt (1,400 ) (2,800 ) Long-term debt, net of current portion $ — $ 1,391 Current portion of long-term debt $ 1,400 $ 2,800 Current portion of debt discount (9 ) (82 ) Current portion of long-term debt, net $ 1,391 $ 2,718
Schedule of exercisable outstanding warrants for purchase of common stock issued	At December 31, 2021, 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 May 13, 2022 1,841 $ 108.60 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 15,747 As of December 31, 2021 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price May 13, 2022 1,841 $ 108.60 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 March 27, 2025 176,554 $ 0.10 May 3, 2025 5,363 $ 26.10 August 27, 2027 1,889,513 $ 0.01 August 31, 2027 1,358,993 $ 0.01 4,810,409
Schedule of future minimum principal and interest payments	Future minimum principal and interest payments under the 2018 Amended SVB Loan, including the final payment, as of December 31, 2021 are as follows (in thousands): 2022 $ 1,717 1,717 Less interest and final payment (317 ) Long-term debt $ 1,400

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Stockholders Equity Note [Abstract]
Schedule of exercisable outstanding warrants for purchase of common stock issued	At December 31, 2021, 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 May 13, 2022 1,841 $ 108.60 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 15,747 As of December 31, 2021 , the Company had the following outstanding warrants for the purchase of common stock: Expiration Number of shares Exercise price May 13, 2022 1,841 $ 108.60 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 March 27, 2025 176,554 $ 0.10 May 3, 2025 5,363 $ 26.10 August 27, 2027 1,889,513 $ 0.01 August 31, 2027 1,358,993 $ 0.01 4,810,409
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, 2020 601,481 $ 21.50 Granted 781,570 8.12 Exercised (3,727 ) 5.64 Forfeited (70,964 ) 13.51 Balance at December 31, 2021 1,308,360 $ 13.99
Schedule of outstanding stock options	Information about the Company’s outstanding stock options as of December 31, 2021 is as follows: Weighted- Average Weighted- Remaining Average Contractual Aggregate Number of Exercise Term Intrinsic Shares Price (in years) Value Options outstanding 1,308,360 $ 13.99 8.19 $ 47,403 Options vested and expected to vest 1,308,360 $ 13.99 8.19 $ 47,403 Options exercisable 401,148 $ 28.40 6.41 $ 30,870
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, 2021 2020 2019 Risk-free interest rate 0.8 % 1.2 % 2.6 % Expected volatility 90.3 % 85.8 % 81.1 % 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, 2021 2020 2019 Research and development $ 628 $ 386 $ 776 General and administrative 1,147 648 848 $ 1,775 $ 1,034 $ 1,624
Schedule of common stock reserved for future issuance	Common stock reserved for future issuance was as follows: December 31, 2021 2020 Common stock warrants 4,810,409 4,810,409 Common stock options and restricted stock units granted and outstanding 1,308,360 601,481 Awards available under the 2015 Plan 115,990 57,468 Shares available under the Employee Stock Purchase Plan 105,619 105,614 6,340,378 5,574,972

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 2020 2019 Cash paid within operating cash flows $ 461 $ 442 $ 423 ROU assets recognized in exchange for new lease obligations $ 1,117 $ — $ 1,143
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, 2021 2020 Reported as: Other assets (ROU asset) $ 1,325 $ 508 Accounts payable and accrued expenses (lease liability) $ 147 $ 418 Other long-term liabilities (lease liability) 1,167 152 Total lease liabilities $ 1,314 $ 570 Weighted average remaining lease term 5.3 1.3 Weighted average discount rate 11.3% 11.3%
Schedule of Maturities of Operating Lease Liabilities	As of December 31, 2021 2022 $ 285 2023 320 2024 334 2025 349 2026 365 2027 123 Total lease payments 1,776 Less imputed interest (462 ) Total operating lease liabilities $ 1,314

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 2020 2019 Federal income taxes $ (6,020 ) $ (3,523 ) $ (4,761 ) State income taxes, net of federal benefit (1,889 ) (1,084 ) (1,381 ) Permanent items 93 104 149 Uncertain tax positions 494 1,224 1,828 Research and development credits (1,661 ) (555 ) (1,253 ) Other, net 28 — (75 ) Stock compensation 203 113 395 Change in valuation allowance 8,752 3,721 5,098 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, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 47,633 $ 40,103 Research and development credits and Orphan Drug Credit 10,472 9,321 Depreciation and amortization 247 258 Right-of-use liability 276 120 Other, net 1,573 1,476 Total deferred tax assets 60,201 51,278 Right-of-use asset (278 ) (107 ) Total deferred tax liabilities (278 ) (107 ) Total net deferred 59,923 51,171 Valuation allowance (59,923 ) (51,171 ) Net deferred tax assets $ — $ —
Schedule of changes in unrecognized tax benefits	The changes in the Company’s unrecognized tax benefits are summarized as follows (in thousands): Balance at December 31, 2018 2,859 Change related to prior year positions — Increase related to current year positions 2,233 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

Organization and Summary of S_4

Organization and Summary of Significant Accounting Policies - Additional Information (Details)	1 Months Ended			12 Months Ended
	Jul. 31, 2021USD ($)$ / sharesshares	Aug. 30, 2020USD ($)	Oct. 31, 2019USD ($)shares	Dec. 31, 2021USD ($)segmentshares	Dec. 31, 2020USD ($)
Basis of Presentation
Accumulated deficit				$ (207,776,000)	$ (179,109,000)
Cash, cash equivalents				$ 24,100,000
Property and Equipment
Estimated useful life				5 years
Segment reporting
Number of reportable segments | segment				1
Jones Trading Institutional Services L L C | Common Stock
Basis of Presentation
Proceeds From Issuance Of Common Stock				$ 7,100,000
Common stock issued and sold | shares				3,000,000
Net proceeds from common stock issuance				$ 7,100,000
Aspire Capital Fund L L C | Common Stock
Basis of Presentation
Proceeds From Issuance Of Common Stock				9,600,000
Maximum aggregate value of common stock to be purchase			$ 15,000,000
Sale duration for common stock under purchase agreement			30 months
Remaining amount available under the Sales Agreement				$ 5,400,000
Common stock issued and sold | shares			142,658	4,800,000
Net proceeds from common stock issuance				$ 9,600,000
Private Placement | Common Stock
Basis of Presentation
Net Proceeds Received From Issuance Private Placement		$ 10,000,000
Capital on Demand Sales Agreement | Jones Trading Institutional Services L L C | Common Stock
Basis of Presentation
Maximum aggregate value of stock to be sold				$ 50,000,000	$ 50,000,000
IPO | Common Stock
Basis of Presentation
Proceeds From Issuance Of Common Stock	$ 13,400,000
Common stock issued and sold | shares	3,926,702
Common stock purchase price per share | $ / shares	$ 3.82
Net proceeds from common stock issuance	$ 13,400,000

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive securities
Antidilutive securities	6,122,027	5,417,239	1,933,616
Warrants to Purchase Common Stock
Antidilutive securities
Antidilutive securities	4,810,409	4,810,409	1,561,903
Common Stock Options and Restricted Stock Units
Antidilutive securities
Antidilutive securities	1,308,360	601,481	370,391
ESPP Shares
Antidilutive securities
Antidilutive securities	3,258	5,349	1,322

Investments, Cash Equivalents_3

Investments, Cash Equivalents and Fair Value Measurements - Additional Information (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Short-term investments	$ 0	$ 3,999,000
Amount of transfers between levels	$ 0	$ 0

Investments, Cash Equivalents_4

Investments, Cash Equivalents and Fair Value Measurements - Schedule of Available-for-sale Securities and Equity Securities (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost		$ 5,249	$ 5,001
Estimated Fair Value		5,249	5,001
Money market funds included in cash equivalents
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost		5,003	1,002
Estimated Fair Value		5,003	1,002
U.S. treasury securities included in short-term investments
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost			3,999
Estimated Fair Value			$ 3,999
Equity securities included in other assets
Short-Term Investments, Cash Equivalents and Fair Value Measurements
Cost	[1]	246
Estimated Fair Value	[1]	$ 246
[1]	The Company’s equity securities included in other assets consisted of its investment in a privately held company. 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. No such impairments or changes were noted for any period presented.

Investments, Cash Equivalents_5

Investments, Cash Equivalents and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Money market funds included in cash equivalents - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Fair value, assets	$ 5,003	$ 5,001
Level 2
Assets:
Fair value, assets	$ 5,003	$ 5,001

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule Of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Public Utilities Inventory [Line Items]
Property and equipment	$ 226	$ 178
Less accumulated depreciation and amortization	(176)	(162)
Property and equipment, net	50	16
Computer And Office Equipment [Member]
Public Utilities Inventory [Line Items]
Property and equipment	186	138
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Depreciation expense related to property and equipment	$ 14,000	$ 12,000	$ 22,000

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule Of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Public Utilities Inventory [Line Items]
Accounts payable	$ 4,943	$ 1,725
Accrued clinical related expenses	4,461	3,559
Accrued legal and accounting	842	37
Other accruals	360	496
Current portion of operating lease liability	1,314	570
Total	10,753	6,235
Other Current Liabilities
Public Utilities Inventory [Line Items]
Current portion of operating lease liability	$ 147	$ 418

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, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-term debt	$ 1,400	$ 4,200
Less debt discount, net of current portion		(9)
Long-term debt, net of debt discount	1,400	4,191
Less current portion of long-term debt	(1,400)	(2,800)
Long-term debt, net of current portion		1,391
Current portion of long-term debt	1,400	2,800
Current portion of debt discount	(9)	(82)
Current portion of long-term debt, net	$ 1,391	$ 2,718

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2021
Debt Instrument [Line Items]
Warrants issued		4,810,409
Silicon Valley Bank
Debt Instrument [Line Items]
Warrants issued		15,747
2018 SVB Loan | Silicon Valley Bank
Debt Instrument [Line Items]
Proceeds from long-term debt	$ 7,000,000
Interest rate	9.00%
Repayment period	30 months
Additional fee on final payment due (as a percent)	4.00%
Warrants issued	5,363
Exercise price (per share)	$ 26.10
2017 SVB Loan | Silicon Valley Bank
Debt Instrument [Line Items]
Final payment on payoff	$ 300,000
Deferral Agreement | Silicon Valley Bank
Debt Instrument [Line Items]
Extension of period for interest only payments		6 months
Maturity date		Jun. 30, 2022
Description of extension of period for interest only payments		In April 2020, the Company entered into a deferral agreement with SVB (the Deferral Agreement) for an interest-only payment period of six months, with a corresponding six month extension to the maturity date to June 2022.

Long-Term Debt - Schedule of Ex

Long-Term Debt - Schedule of Exercisable Outstanding Warrants for Purchase of Common Stock Issued (Details)	Dec. 31, 2021$ / sharesshares
Debt Instrument [Line Items]
Warrants issued	4,810,409
Silicon Valley Bank
Debt Instrument [Line Items]
Warrants issued	15,747
Silicon Valley Bank | May 13, 2022
Debt Instrument [Line Items]
Warrants issued	1,841
Exercise price (per share) | $ / shares	$ 108.60
Silicon Valley Bank | November 14, 2023 Through June 4, 2024
Debt Instrument [Line Items]
Warrants issued	3,874
Exercise price (per share) | $ / shares	$ 77.40
Silicon Valley Bank | January 25, 2024
Debt Instrument [Line Items]
Warrants issued	4,669
Exercise price (per share) | $ / shares	$ 51.40
Silicon Valley Bank | May 3, 2025
Debt Instrument [Line Items]
Warrants issued	5,363
Exercise price (per share) | $ / shares	$ 26.10

Long-Term Debt - Schedule of Fu

Long-Term Debt - Schedule of Future Minimum Principal and Interest Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 1,400	$ 4,200
2018 Amended SVB Loan
Debt Instrument [Line Items]
2022	1,717
Long Term Debt Including Final Payment	1,717
Less interest and final payment	(317)
Long-term debt	$ 1,400

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Dec. 31, 2021USD ($)
Research and development arrangement
Commitments and Contingencies
Potential milestone payable	$ 9.6

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended				12 Months Ended
	Jul. 31, 2021	Dec. 31, 2020	Aug. 30, 2020	Oct. 31, 2019	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Conversion of warrants to purchase shares					4,810,409
2020 Pre-Funded Warrants
Class Of Stock [Line Items]
Warrants exercised					0	181,190
Proceeds from warrant exercises						$ 2,000
2020 Pre-Funded Warrants and Common Warrants
Class Of Stock [Line Items]
Maximum percentage of holders ownership interest in common stock after exercise			19.99%
Common Stock | Jones Trading Institutional Services L L C
Class Of Stock [Line Items]
Common stock issued and sold					3,000,000
Net proceeds from common stock issuance					$ 7,100,000
Common Stock | Aspire Capital Fund L L C
Class Of Stock [Line Items]
Common stock issued and sold				142,658	4,800,000
Net proceeds from common stock issuance					$ 9,600,000
Maximum aggregate value of common stock to be purchase				$ 15,000,000
Sale duration for common stock under purchase agreement				30 months
Common Stock | IPO
Class Of Stock [Line Items]
Common stock issued and sold	3,926,702
Common stock purchase price per share	$ 3.82
Net proceeds from common stock issuance	$ 13,400,000
Common Stock | Direct Offerings
Class Of Stock [Line Items]
Common stock issued and sold		1,612,844
Common stock purchase price per share		$ 8.84				$ 8.84
Net proceeds from common stock issuance		$ 13,600,000
Common Stock | Private Placement
Class Of Stock [Line Items]
Net Proceeds Received From Issuance Private Placement			$ 10,000,000
Common Stock | Private Placement | 2020 Pre-Funded Warrants
Class Of Stock [Line Items]
Exercise price (per share)			$ 0.01
Common Stock | Private Placement | Purchase Price of $1.66 Per Share
Class Of Stock [Line Items]
Common stock issued and sold			2,633,838
Common stock purchase price per share			$ 1.66
Common Stock | Private Placement | Purchase Price of $1.64 Per Share | 2020 Pre-Funded Warrants
Class Of Stock [Line Items]
Common stock purchase price per share			$ 1.64
Conversion of warrants to purchase shares			3,429,696
Common Stock | Capital on Demand Sales Agreement | Jones Trading Institutional Services L L C
Class Of Stock [Line Items]
Maximum aggregate value of stock to be sold		$ 50,000,000			$ 50,000,000	$ 50,000,000
Percentage of gross proceeds, required to pay for common stock sold through sales agreement		2.50%

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Outstanding Warrants for Purchase of Common Stock Issued (Details)	Dec. 31, 2021$ / sharesshares
Class Of Stock [Line Items]
Warrants issued	4,810,409
May 13, 2022
Class Of Stock [Line Items]
Warrants issued	1,841
Exercise price (per share) | $ / shares	$ 108.60
November 14, 2023 Through June 4, 2024
Class Of Stock [Line Items]
Warrants issued	3,874
Exercise price (per share) | $ / shares	$ 77.40
January 25, 2024
Class Of Stock [Line Items]
Warrants issued	4,669
Exercise price (per share) | $ / shares	$ 51.40
March 27, 2024
Class Of Stock [Line Items]
Warrants issued	1,369,602
Exercise price (per share) | $ / shares	$ 27
March 27, 2025
Class Of Stock [Line Items]
Warrants issued	176,554
Exercise price (per share) | $ / shares	$ 0.10
May 3, 2025
Class Of Stock [Line Items]
Warrants issued	5,363
Exercise price (per share) | $ / shares	$ 26.10
August 27, 2027
Class Of Stock [Line Items]
Warrants issued	1,889,513
Exercise price (per share) | $ / shares	$ 0.01
August 31, 2027
Class Of Stock [Line Items]
Warrants issued	1,358,993
Exercise price (per share) | $ / shares	$ 0.01

Stockholders' Equity - (SBC) -

Stockholders' Equity - (SBC) - Additional Information (Details) - USD ($)	Jan. 02, 2015	Dec. 31, 2015	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock Plans
Shares of common stock reserved for future issuance			6,340,378	5,574,972
Stock Option
Share-based compensation
Unrecognized compensation cost			$ 4,000,000	$ 1,300,000
Unrecognized compensation cost, period of recognition				2 years 7 months 6 days
Stock options, additional disclosures
Weighted-average grant date fair value (in dollars per share)			$ 6.05	$ 2.62	$ 5.55
Share price (in dollar per share)			$ 2.77
Proceeds from exercise of stock options			$ 21,000,000,000
Shares Options, Exercises in Period			3,727	0	0
Total fair value of options vested during the year			$ 800,000	$ 1,000,000	$ 1,500,000
Stock Option | Year One
Stock Plans
Grants vesting period			1 year
Grants vesting (as a percent)			25.00%
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	1.00%
Share-based compensation
Percentage of eligible compensation	15.00%
Stock options, additional disclosures
Number of shares that could potentially be issued	250,000
2015 Equity Incentive Plan
Stock Plans
Maximum term of options granted			10 years
Shares of common stock reserved for future issuance	80,103		115,990	57,468
Percentage of total number of shares of common stock outstanding	5.00%
Additional shares to be used exclusively for grant for Inducement awards		200,000
2015 Equity Incentive Plan | Restricted Stock Units
Share-based compensation
Aggregate intrinsic value of outstanding units			$ 0	$ 0
2015 Equity Incentive Plan | Restricted Stock Units | Board of Directors
Share-based compensation
Total fair value of the units			$ 0	$ 300,000

Stockholders' Equity- Summary o

Stockholders' Equity- Summary of Stock Option Activity (Details) - Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Options
Balance (in shares)	601,481
Granted (in shares)	781,570
Exercised (in shares)	(3,727)	0	0
Forfeited (in shares)	(70,964)
Balance (in shares)	1,308,360	601,481
Weighted-Average Exercise Price
Balance (in dollars per share)	$ 21.50
Granted (in dollars per share)	8.12
Exercised (in dollars per share)	5.64
Forfeited (in dollars per share)	13.51
Balance (in dollars per share)	$ 13.99	$ 21.50

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Company's Outstanding Stock Option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Options
Number of shares, options vested and expected to vest	1,308,360	601,481
Stock Option
Number of Options
Number of shares, options vested and expected to vest	1,308,360
Number of shares, options exercisable	1,308,360
Aggregate intrinsic value, options vested and expected to vest	$ 47,403
Aggregate intrinsic value, options exercisable	$ 47,403
Weighted-Average Exercise Price
Weighted-average exercise price, options vested and expected to vest (in dollars per share)	$ 13.99
Weighted-average exercise price, options exercisable (in dollars per share)	$ 13.99
Weighted-average remaining contractual term, options vested and expected to vest (in years)	8 years 2 months 8 days
Weighted-average remaining contractual term, options exercisable (in years)	6 years 4 months 28 days

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Risk-free interest rate	0.80%	1.20%	2.60%
Expected volatility	90.30%	85.80%	81.10%
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	0.00%	0.00%	0.00%

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Stock based compensation expense	$ 1,775	$ 1,034	$ 1,624
Research and development
Class Of Stock [Line Items]
Stock based compensation expense	628	386	776
General and administrative
Class Of Stock [Line Items]
Stock based compensation expense	$ 1,147	$ 648	$ 848

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Common Stock Reserved For Future Issuance (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Jan. 02, 2015
Stock Plans
Shares of common stock reserved for future issuance	6,340,378	5,574,972
Number of shares, options vested and expected to vest	1,308,360	601,481
2015 Equity Incentive Plan
Stock Plans
Shares of common stock reserved for future issuance	115,990	57,468	80,103
Common Stock. | Warrants
Stock Plans
Shares of common stock reserved for future issuance	4,810,409	4,810,409
ESPP
Stock Plans
Shares of common stock reserved for future issuance			18,346
Shares of common stock reserved for future issuance	105,619	105,614

Collaborations - Additional Inf

Collaborations - Additional Information (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2018USD ($)antibody	Dec. 31, 2021USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Termination fee	$ 9,000,000
Janssen | License and Option Agreement | NIK Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Consideration exchanged for assets acquired		$ 0
Value given to assets acquired		0
Enviro and Kairos
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One time upfront payment fee		100,000
Future potential milestone payments upon achievement of financing events		$ 1,000,000
Bispecific Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty on net sales		50.00%
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	40.00%
TJ4309 Agreement | I-Mab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of cost bearing	60.00%
Potential payments receivable		340,000,000
Termination of agreement upon completion of clinical trial	90 days
Additional payment	$ 35,000,000
TJ4309 Agreement | I-Mab | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-royalty consideration	35,000,000
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
License and Option Agreement | Enviro and Kairos
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment for transaction		100,000
License and Option Agreement | Enviro and Kairos | Development Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Single digit equity ownership		200,000
License and Option Agreement | Enviro and Kairos | Development And Regulatory Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance of potential milestone that could be received		1,000,000
Collaboration revenue recognized		$ 0
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, 2020	Dec. 31, 2019	Dec. 31, 2021
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	$ 175,000			$ 175,000

Leases - Supplemental cash flow

Leases - Supplemental cash flow information related to operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Cash paid within operating cash flows	$ 461	$ 442	$ 423
ROU assets recognized in exchange for new lease obligations	$ 1,117		$ 1,143

Leases - Supplemental balance s

Leases - Supplemental balance sheet information related to operating leases (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Reported as:
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Current portion of operating lease liability	$ 1,314	$ 570
Weighted average remaining lease term	5 years 3 months 18 days	1 year 3 months 18 days
Weighted average discount rate	11.30%	11.30%
Other assets (ROU asset)
Reported as:
Other assets (ROU asset)	$ 1,325	$ 508
Accounts payable and accrued expenses (lease liability)
Reported as:
Current portion of operating lease liability	147	418
Other long-term liabilities (lease liability)
Reported as:
Current portion of operating lease liability	$ 1,167	$ 152

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 285
2023	320
2024	334
2025	349
2026	365
2027	123
Total lease payments	1,776
Less imputed interest	(462)
Current portion of operating lease liability	$ 1,314	$ 570

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of effective tax rate and federal statutory tax rate
Federal income taxes	$ (6,020)	$ (3,523)	$ (4,761)
State income taxes, net of federal benefit	(1,889)	(1,084)	(1,381)
Permanent items	93	104	149
Uncertain tax positions	494	1,224	1,828
Research and development credits	(1,661)	(555)	(1,253)
Other, net	28		(75)
Stock compensation	203	113	395
Change in valuation allowance	8,752	3,721	5,098
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, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 47,633	$ 40,103
Research and development credits and Orphan Drug Credit	10,472	9,321
Depreciation and amortization	247	258
Right-of-use liability	276	120
Other, net	1,573	1,476
Total deferred tax assets	60,201	51,278
Right-of-use asset	(278)	(107)
Total deferred tax liabilities	(278)	(107)
Total net deferred	59,923	51,171
Valuation allowance	(59,923)	(51,171)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Carryforwards
Net change in the total valuation allowance	$ 8,800,000	$ 3,700,000	$ 5,100,000
NOL carryforward	96,200,000
Accrual for interest or penalties for unrecognized tax benefits	0	$ 0
Income tax interest or penalties expense for unrecognized tax benefits	$ 0
Minimum
Carryforwards
Percent of ownership	50.00%			50.00%
CARES Act
Carryforwards
NOL carryforward available to offset future taxable income, percentage	80.00%	80.00%	80.00%	80.00%
Federal
Carryforwards
NOL carryforward	$ 179,400,000
NOL carryforward begin to expire	2030
Federal | Research and Development and Orphan Drug Credit Carryforwards
Carryforwards
Credit carryforward	$ 11,800,000
Credit carryforward begin to expire	2031
California
Carryforwards
NOL carryforward	$ 144,400,000
NOL carryforward begin to expire	2030
California | Research and Development and Orphan Drug Credit Carryforwards
Carryforwards
Credit carryforward	$ 2,700,000

Income Taxes - Schedule of Chan

Income Taxes - Schedule of Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unrecognized tax benefits
Balance, beginning of period	$ 6,610	$ 5,092	$ 2,859
Change related to prior year positions	(1)
Increase related to current year positions	506	1,518	2,233
Balance, end of period	7,117	$ 6,610	$ 5,092
Change related to prior year positions	$ 1

401(k) Plan - Additional Inform

401(k) Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Pension and Other Postretirement Plans Disclosure
Defined contribution, plan name	us-gaap:RetirementPlanNameOtherMember	us-gaap:RetirementPlanNameOtherMember	us-gaap:RetirementPlanNameOtherMember
Defined contribution amount	$ 0.1	$ 0.1	$ 0.2