Aclaris Therapeutics (ACRS) 10-K 27 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Jan. 31, 2024	Jun. 30, 2023
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-37581
Entity Registrant Name	Aclaris Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-0571712
Entity Address, Address Line One	701 Lee Road, Suite 103
Entity Address, City or Town	Wayne
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19087
City Area Code	484
Local Phone Number	324-7933
Title of 12(b) Security	Common Stock, $0.00001 par value
Trading Symbol	ACRS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 712.6
Entity Common Stock, Shares Outstanding		70,925,042
Entity Central Index Key	0001557746
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	238
Auditor Location	Philadelphia, Pennsylvania
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 39,878	$ 45,277
Short-term marketable securities	79,228	172,294
Accounts receivable, net	298	484
Prepaid expenses and other current assets	9,452	13,495
Total current assets	128,856	231,550
Marketable securities	62,771	12,242
Property and equipment, net	1,620	1,099
Intangible assets	269	6,973
Other assets	3,889	2,732
Total assets	197,405	254,596
Current liabilities:
Accounts payable	8,878	10,351
Accrued expenses	19,446	8,701
Current portion of lease liabilities	426	684
Discontinued operations	2,202	2,202
Total current liabilities	30,952	21,938
Other liabilities	3,074	1,570
Contingent consideration	6,200	33,100
Deferred tax liability		367
Total liabilities	40,226	56,975
Commitments and contingencies (Note 17)
Stockholders' Equity:
Preferred stock, $0.00001 par value; 10,000,000 shares authorized and no shares issued or outstanding at December 31, 2023 and December 31, 2022
Common stock, $0.00001 par value; 200,000,000 and 100,000,000 shares authorized at December 31, 2023 and December 31, 2022, respectively; 70,894,889 and 66,688,647 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	1	1
Additional paidin capital	928,080	880,832
Accumulated other comprehensive loss	(106)	(897)
Accumulated deficit	(770,796)	(682,315)
Total stockholders' equity	157,179	197,621
Total liabilities and stockholders' equity	$ 197,405	$ 254,596

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	200,000,000	100,000,000
Common stock, shares issued (in shares)	70,894,889	66,688,647
Common stock, shares outstanding (in shares)	70,894,889	66,688,647

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Total revenue	$ 31,249	$ 29,752	$ 6,761
Costs and expenses:
Cost of revenue	3,423	4,023	4,713
Research and development	98,384	77,813	43,813
General and administrative	32,412	25,133	23,619
Licensing	14,658	7,937
Revaluation of contingent consideration	(26,900)	4,700	24,339
Intangible asset impairment	6,629
Total costs and expenses	128,606	119,606	96,484
Loss from operations	(97,357)	(89,854)	(89,723)
Other income (expense), net	8,509	2,946	(1,142)
Loss before income taxes	(88,848)	(86,908)	(90,865)
Income tax benefit	(367)
Net loss	$ (88,481)	$ (86,908)	$ (90,865)
Net loss per share, basic	$ (1.27)	$ (1.33)	$ (1.60)
Net loss per share, diluted	$ (1.27)	$ (1.33)	$ (1.60)
Weighted average common shares outstanding, basic	69,808,855	65,213,944	56,730,583
Weighted average common shares outstanding, diluted	69,808,855	65,213,944	56,730,583
Other comprehensive loss:
Unrealized gain (loss) on marketable securities, net of tax of $0	$ 791	$ (673)	$ (229)
Foreign currency translation adjustment			99
Total other comprehensive gain (loss)	791	(673)	(130)
Comprehensive loss	(87,690)	(87,581)	(90,995)
Contract research
Revenues:
Total revenue	3,035	4,395	5,830
Licensing
Revenues:
Total revenue	$ 28,214	25,100	809
Other
Revenues:
Total revenue		$ 257	$ 122

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Unrealized loss on marketable securities, tax	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock Public Offering	Common Stock At The Market Offering	Common Stock	Additional Paid-in Capital Public Offering	Additional Paid-in Capital At The Market Offering	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Public Offering	At The Market Offering	Total
Balance at beginning of period at Dec. 31, 2020						$ 542,286	$ (94)	$ (504,542)			$ 37,650
Balance at beginning of period (in shares) at Dec. 31, 2020			45,109,314
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units						1,574					1,574
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units (in shares)			1,714,269
Issuance of common stock in connection with public offerings, net of offering costs	$ 1			$ 238,199					$ 238,200
Issuance of common stock in connection with public offerings, net of offering costs, shares	14,404,863
Unrealized gain (loss) on marketable securities							(229)				(229)
Foreign currency translation adjustment							99				99
Stock-based compensation expense						14,060					14,060
Net loss								(90,865)			(90,865)
Balance at end of period at Dec. 31, 2021			$ 1			792,971	(224)	(595,407)			197,341
Balance at end of period (in shares) at Dec. 31, 2021			61,228,446
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units						(163)					(163)
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units (in shares)			621,492
Issuance of common stock in connection with public offerings, net of offering costs					$ 72,659					$ 72,659
Issuance of common stock in connection with public offerings, net of offering costs, shares		4,838,709
Unrealized gain (loss) on marketable securities							(673)				(673)
Stock-based compensation expense						15,039					15,039
Net loss								(86,908)			(86,908)
Balance at end of period at Dec. 31, 2022			$ 1			880,832	(897)	(682,315)			$ 197,621
Balance at end of period (in shares) at Dec. 31, 2022			66,688,647								66,688,647
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units						8					$ 8
Issuance of common stock in connection with exercise of stock options and warrants and vesting of restricted stock units (in shares)			806,242
Issuance of common stock in connection with public offerings, net of offering costs					$ 26,714					$ 26,714
Issuance of common stock in connection with public offerings, net of offering costs, shares		3,400,000
Unrealized gain (loss) on marketable securities							791				791
Stock-based compensation expense						20,542					20,542
Net loss								(88,481)			(88,481)
Balance at end of period at Dec. 31, 2023			$ 1			$ 928,080	$ (106)	$ (770,796)			$ 157,179
Balance at end of period (in shares) at Dec. 31, 2023			70,894,889								70,894,889

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Public Offering
Offering costs netted against proceeds			$ 15,910
At The Market Offering
Offering costs netted against proceeds	$ 826	$ 2,341

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (88,481)	$ (86,908)	$ (90,865)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	863	797	923
Stock-based compensation expense	20,542	15,039	14,060
Revaluation of contingent consideration	(26,900)	4,700	24,339
Loss on extinguishment of debt			752
Intangible asset impairment charge	6,629
Deferred taxes	(367)
Changes in operating assets and liabilities:
Accounts receivable	186	139	149
Prepaid expenses and other assets	(1,315)	(2,294)	(5,617)
Accounts payable	(1,473)	368	3,655
Accrued expenses	11,991	592	470
Net cash used in operating activities	(78,325)	(67,567)	(52,134)
Cash flows from investing activities:
Purchases of property and equipment	(1,309)	(605)	(308)
Purchases of marketable securities	(135,675)	(164,753)	(235,153)
Proceeds from sales and maturities of marketable securities	183,204	177,986	67,829
Net cash provided by (used in) investing activities	46,220	12,628	(167,632)
Cash flows from financing activities:
Proceeds from issuance of common stock in connection with public offerings, net of issuance costs			238,200
Proceeds from issuance of common stock under the at-the-market sales agreement, net of issuance costs	26,714	72,744
Repayment of debt			(11,483)
Payments of employee withholding taxes related to restricted stock unit award vesting	(102)	(34)	(3,124)
Proceeds from exercise of employee stock options and the issuance of stock	94	157	1,459
Net cash provided by financing activities	26,706	72,867	225,052
Net (decrease) increase in cash and cash equivalents	(5,399)	17,928	5,286
Cash and cash equivalents at beginning of period	45,277	27,349	22,063
Cash and cash equivalents at end of period	$ 39,878	45,277	27,349
Supplemental disclosure of non-cash investing and financing activities:
Additions to property and equipment included in accounts payable		$ 24	$ 143

Organization and Nature of Busi

Organization and Nature of Business	12 Months Ended
	Dec. 31, 2023
Organization and Nature of Business
Organization and Nature of Business	1. Organization and Nature of Business ​ Overview ​ Aclaris Therapeutics, Inc. was incorporated under the laws of the State of Delaware in 2012. In August 2017, Confluence Life Sciences, Inc. (now known as Aclaris Life Sciences, Inc.) (“Confluence”) was acquired by Aclaris Therapeutics, Inc. and became a wholly owned subsidiary thereof. Aclaris Therapeutics, Inc. and its wholly owned subsidiaries are referred to collectively as the “Company.” ​ The Company is a clinical-stage biopharmaceutical company focused on developing novel drug candidates for immuno-inflammatory diseases. The Company’s proprietary KINect drug discovery platform allows the Company to identify and advance potential drug candidates that it may develop independently or in collaboration with third parties. In addition to identifying and developing its novel drug candidates, the Company is pursuing strategic alternatives, including identifying and consummating transactions with third-party partners, to further develop, obtain marketing approval for and/or commercialize its novel drug candidates. early-stage research and development ​ Liquidity ​ The Company’s consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. As of December 31, 2023, the Company had cash, cash equivalents and marketable securities of $181.9 million and an accumulated deficit of $770.8 million. Since inception, the Company has incurred net losses and negative cash flows from its operations. Prior to the acquisition of Confluence in August 2017, the Company had never generated revenue. There can be no assurance that profitable operations will ever be achieved, and, if achieved, will be sustained on a continuing basis. In addition, development activities, including clinical and preclinical testing of the Company’s drug candidates, will require significant additional financing. The future viability of the Company is dependent on its ability to successfully develop its drug candidates and to generate revenue from identifying and consummating transactions with third-party partners to further develop, obtain marketing approval for and/or commercialize its development assets or to raise additional capital to finance its operations. The Company will require additional capital to develop its drug candidates and to support its discovery efforts. ​ Additional funds may not be available on a timely basis, on commercially acceptable terms, or at all, and such funds, if raised, may not be sufficient to enable the Company to continue to implement its long-term business strategy. The Company's ability to raise additional capital may be adversely impacted by potentially worsening global economic conditions caused by a variety of factors including geopolitical tensions, rising interest rates and inflationary pressures. If the Company is unable to raise sufficient additional capital or generate revenue from transactions with potential third-party partners for the development and/or commercialization of its drug candidates, it may need to substantially curtail planned operations. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. ​ ​

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements of the Company include the accounts of the operating parent company, Aclaris Therapeutics, Inc., and its wholly owned subsidiaries. All intercompany transactions have been eliminated. Based upon the Company’s revenue, the Company believes that gross profit does not provide a meaningful measure of profitability and, therefore, has not included a line item for gross profit on the consolidated statement of operations. ​ Reclassifications ​ Certain prior year amounts have been reclassified to conform to the current year financial statement presentation. ​ Discontinued Operations ​ In September 2019, the Company announced the completion of a strategic review and its decision to refocus its resources on its immuno-inflammatory development programs and to actively seek partners for its commercial products. ​ As of December 31, 2023 and 2022, the Company had $2.2 million in accrued expenses reported as discontinued operations in the Company’s consolidated balance sheet. ​ Use of Estimates ​ The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, contingent consideration and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require an update to its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from the Company’s estimates. ​ Revenue Recognition ​ The Company accounts for revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers. Under ASC Topic 606, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. ​ ​ Contract Research ​ The Company earns contract research revenue from the provision of laboratory services. Contract research revenue is generally evidenced by contracts with clients which are on an agreed upon fixed-price, fee-for-service basis and are generally billed on a monthly basis in arrears for services rendered. Revenue related to these contracts is generally recognized as the laboratory services are performed, based upon the rates specified in the contracts. Under ASC Topic 606, the Company elected to apply the “right to invoice” practical expedient when recognizing contract research revenue and as such, recognizes revenue in the amount which it has the right to invoice. ASC Topic 606 also provides an optional exemption, which the Company has elected to apply, from disclosing remaining performance obligations when revenue is recognized from the satisfaction of the performance obligation in accordance with the “right to invoice” practical expedient. ​ Licensing Revenue ​ Licenses of Intellectual Property ​ Milestone and Royalty Payments ​ Cash Equivalents ​ The Company considers all short-term, highly liquid investments with original maturities of three months or less at acquisition date to be cash equivalents. Cash equivalents, which have consisted of money market funds and commercial paper, are stated at fair value. ​ Marketable Securities ​ Marketable securities with original maturities of greater than three months and remaining maturities of less than one year from the balance sheet date are classified as short-term. Marketable securities with remaining maturities of greater than one year from the balance sheet date are classified as long-term. ​ The Company classifies all marketable securities as available-for-sale securities. The Company’s marketable securities are measured and reported at fair value using either quoted prices in active markets for identical securities or quoted prices in markets that are not active for identical or similar securities. Unrealized gains and losses are reported as a separate component of stockholders’ equity. The cost of securities sold is determined on a specific identification basis, and realized gains and losses, if any, are included in other expense, net within the consolidated statement of operations and comprehensive loss. If any adjustment to fair value reflects a decline in the value of the investment, the Company considers available evidence to evaluate the extent to which the decline is “other than temporary” and reduces the investment to fair value through a charge to the statement of operations and comprehensive loss. ​ Property and Equipment ​ Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. Computer equipment is depreciated over three years. Laboratory equipment is depreciated over three ​ Impairment of Long-Lived Assets ​ Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. ​ Intangible Assets ​ Intangible assets include both definite-lived and indefinite-lived assets. Definite-lived intangible assets consist of a drug discovery platform the Company acquired through the acquisition of Confluence. Definite-lived intangible assets are amortized over their estimated useful life based on the pattern over which the intangible assets are consumed or otherwise used up. If that pattern cannot be reliably determined, the straight-line method of amortization is used. Indefinite-lived intangible assets consisted of an in-process research and development (“IPR&D”) drug candidate acquired through the acquisition of Confluence. IPR&D assets are considered indefinite-lived until the completion or abandonment of the associated research and development efforts. The cost of IPR&D is either amortized over its estimated useful life beginning when the underlying drug candidate is approved and launched commercially, or expensed immediately if development of the drug candidate is abandoned or otherwise impaired. ​ Definite-lived intangible assets are tested for impairment when events or changes in circumstances indicate that the carrying value of the asset may not be recoverable. Indefinite-lived intangible assets are tested for impairment at least annually, which the Company performs during the fourth quarter, or when indicators of an impairment are present. The Company recognizes impairment losses when and to the extent that the estimated fair value of an intangible asset is less than its carrying value. ​ During the quarter ended December 31, 2023, the Company performed an impairment analysis on the IPR&D intangible asset due to the Company’s decision to discontinue further development of the drug candidate in immuno-inflammatory diseases. The Company’s impairment analysis resulted in a fair value of the IPR&D intangible asset which was less than the carrying value. As a result, the Company recorded an impairment charge of $6.6 million, the full balance of the IPR&D intangible asset. ​ Leases ​ Leases represent a company’s right to use an underlying asset and a corresponding obligation to make payments to a lessor for the right to use those assets. The Company evaluates leases at their inception to determine if they are an operating lease or a finance lease. A lease is accounted for as a finance lease if it meets one of the following five criteria: the lease has a purchase option that is reasonably certain of being exercised, the present value of the future cash flows are substantially all of the fair market value of the underlying asset, the lease term is for a significant portion of the remaining economic life of the underlying asset, the title to the underlying asset transfers at the end of the lease term, or if the underlying asset is of such a specialized nature that it is expected to have no alternative uses to the lessor at the end of the term. Leases that do not meet the finance lease criteria are accounted for as an operating lease. ​ The Company recognizes assets and liabilities for leases at their inception based upon the present value of all payments due under the lease. The Company uses an incremental borrowing rate to determine the present value of operating leases. The Company determines incremental borrowing rates by referencing collateralized borrowing rates for debt instruments with terms similar to the respective lease. The Company recognizes expense for operating leases on a straight-line basis over the term of each lease. The Company includes estimates for any residual value guarantee obligations under its leases in lease liabilities recorded on its consolidated balance sheet. ​ Right-of-use assets are included in other assets on the Company’s consolidated balance sheet for operating leases. Obligations for lease payments are included in current portion of lease liabilities and other liabilities on the Company’s consolidated balance sheet for operating leases. ​ Contingent Consideration ​ The Company records a contingent consideration liability related to future potential payments resulting from the acquisition of Confluence based upon significant unobservable inputs including the achievement of regulatory and commercial milestones, as well as estimated future sales levels and the discount rates applied to calculate the present value of the potential payments. Significant judgement is involved in determining the appropriateness of these assumptions. These assumptions are considered Level 3 inputs. Revaluation of the contingent consideration liability can result from changes to one or more of these assumptions. The Company evaluates the fair value estimate of the contingent consideration liability on a quarterly basis with changes, if any, recorded as income or expense in the consolidated statement of operations. ​ The fair value of contingent consideration is estimated using a probability-weighted expected payment model for regulatory milestone payments and a Monte Carlo simulation model for commercial milestone and royalty payments and then applying a risk-adjusted discount rate to calculate the present value of the potential payments. Significant assumptions used in the Company’s estimates include the probability of achieving regulatory milestones and commencing commercialization, which are based on an asset’s current stage of development and a review of existing clinical data. The probability of success on the year of each potential payment. ​ Research and Development Costs ​ Research and development costs are expensed as incurred. Research and development expenses include salaries, stock-based compensation and benefits of employees, and other operational costs related to the Company’s research and development activities, including depreciation expenses and the cost of research and development contracts which the Company has entered into with outside vendors to conduct both preclinical studies and clinical trials. Significant judgment and estimates are made in determining the amount of research and development costs recognized in each reporting period. The Company analyzes the progress of its preclinical studies and clinical trials, completion of milestone events, invoices received and contracted costs when estimating research and development costs. Actual results could differ from the Company’s estimates. The Company’s historical estimates for research and development costs have not been materially different from the actual costs. ​ Stock-Based Compensation ​ The Company measures the compensation expense of stock-based awards granted to employees and directors using the grant date fair value of the award. The Company has issued stock options and restricted stock unit (“RSU”) awards with service-based vesting conditions, as well as with performance-based vesting conditions. The Company has not issued awards that include market-based conditions. For service-based awards the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period, which is typically four years. For performance-based awards the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period beginning in the period that it becomes probable the performance conditions will occur. At each balance sheet date, the Company evaluates whether any performance conditions related to a performance-based award have changed. The effect of any change in performance conditions would be recognized as a cumulative catch-up adjustment in the period such change occurs, and any remaining unrecognized compensation expense would be recognized on a straight-line basis over the remaining requisite service period. The impact of forfeitures is recognized in the period in which they occur. ​ The Company measures the compensation expense of stock-based awards granted to consultants using the grant date fair value of the award. The Company recognizes compensation expense over the period during which services are rendered by the consultant. ​ The Company classifies stock-based compensation expense in its statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipients’ service payments are classified. ​ The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Historically, the Company estimated expected volatility based on historical volatility of a set of peer companies, which are publicly traded. Starting in 2022, the Company estimated expected volatility based on its stock price's historical volatility, as the Company determined that it had adequate historical data regarding the volatility of its own publicly-traded stock price. The expected term of the Company’s stock options has been determined using the “simplified” method for awards that qualify as “plain vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The Company uses an expected dividend yield of zero based on the fact that the Company has never paid cash dividends and does not expect to pay cash dividends in the future. ​ The fair value of each RSU is measured using the closing price of the Company’s common stock on the date of grant. ​ Patent Costs ​ All patent related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. ​ Income Taxes ​ The Company accounts for income taxes using 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 recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. ​ The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more likely than not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves and unrecognized tax benefits that are considered appropriate, as well as the related net interest and penalties. ​ Comprehensive Loss ​ Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. Comprehensive loss is primarily comprised of net loss and unrealized gains (losses) on marketable securities. ​ Net Loss per Share ​ Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted average number of common shares outstanding during the period, plus the weighted average number of potential shares of common stock from the assumed exercise of stock options and warrants and the assumed vesting of RSUs, if dilutive. Since the Company was in a net loss position, basic and diluted net loss per share was the same for each of the periods presented. ​ Fair Value Measurements ​ Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ● Level 1 — Quoted prices in active markets for identical assets or liabilities. ​ ● Level 2 — Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ​ ● Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. ​ The Company’s cash equivalents, marketable securities and contingent consideration are carried at fair value, determined according to the fair value hierarchy described above. The carrying value of the Company’s accounts payable and accrued expenses approximate fair value due to the short-term nature of these liabilities. ​ Concentration of Credit Risk and of Significant Suppliers ​ Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds all cash, cash equivalents and marketable securities balances at three accredited financial institutions, the majority of which are in amounts that exceed or are not subject to federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. ​ The Company is dependent on third-party manufacturers to supply drug product, including all underlying components, for its research and development activities, including preclinical and clinical testing. These activities could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients or other components. ​ Segment Reporting ​ Operating segments are components of a company for which separate financial information is available and evaluated regularly by the chief operating decision maker in assessing performance and deciding how to allocate resources. The Company has two reportable segments, therapeutics and contract research. The therapeutics segment is focused on identifying and developing innovative therapies to address significant unmet needs for immuno-inflammatory diseases. The contract research segment earns revenue from the provision of laboratory services. The Company does not report balance sheet information by segment since it is not reviewed by the chief operating decision maker, and all of the Company’s tangible assets are held in the United States. ​ Recently Issued Accounting Pronouncements ​ ​ ​

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	12 Months Ended
	Dec. 31, 2023
Fair Value of Financial Assets and Liabilities
Fair Value of Financial Assets and Liabilities	3. Fair Value of Financial Assets and Liabilities ​ The following tables present information about the fair value measurements of the Company’s financial assets and liabilities which are measured at fair value on a recurring and non-recurring basis, and indicate the level of the fair value hierarchy utilized to determine such fair values: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 (In thousands) Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents ​ $ 32,177 ​ $ — ​ $ — ​ $ 32,177 Marketable securities ​ — ​ ​ 141,999 ​ ​ — ​ ​ 141,999 Total assets ​ $ 32,177 ​ $ 141,999 ​ $ — ​ $ 174,176 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration ​ $ — ​ $ — ​ $ 6,200 ​ $ 6,200 Total liabilities ​ $ — ​ $ — ​ $ 6,200 ​ $ 6,200 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 (In thousands) Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents ​ $ 38,516 ​ $ — ​ $ — ​ $ 38,516 Marketable securities ​ — ​ ​ 184,536 ​ ​ — ​ ​ 184,536 Total assets ​ $ 38,516 ​ $ 184,536 ​ $ — ​ $ 223,052 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration ​ $ — ​ $ — ​ $ 33,100 ​ $ 33,100 Total liabilities ​ $ — ​ $ — ​ $ 33,100 ​ $ 33,100 ​ As of December 31, 2023 and 2022, the Company’s cash equivalents consisted of a money market fund, which was valued based upon Level 1 inputs. The Company’s marketable securities as of December 31, 2023 consisted of commercial paper and corporate debt, asset-backed debt, foreign government agency debt and U.S. government agency debt securities, which were valued based upon Level 2 inputs. The Company’s marketable securities as of December 31, 2022 consisted of commercial paper and corporate debt, asset-backed debt and U.S. government and government agency debt securities, which were valued based upon Level 2 inputs. ​ In determining the fair value of its Level 2 investments, the Company relied on quoted prices for identical securities in markets that are not active. These quoted prices were obtained by the Company with the assistance of a third-party pricing service based on available trade, bid and other observable market data for identical securities. During the years ended December 31, 2023 and 2022, there were no transfers into or out of Level 3. ​ The decrease in contingent consideration of $26.9 million during the year ended December 31, 2023 primarily resulted from the removal of estimated sales of zunsemetinib for moderate to severe rheumatoid arthritis, moderate to severe hidradenitis suppurativa and moderate to severe psoriatic arthritis, following the Company’s decision to discontinue further development of its MK2 inhibitor programs in immuno-inflammatory diseases. This decrease was partially offset by lower discount rates resulting from lower risk-free rates and changes in credit spreads, as well as the passage of time. ​ As of December 31, 2023 and 2022, the fair value of the Company’s available-for-sale marketable securities by type of security was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Book ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Value ​ Gain ​ Loss ​ Value Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities (1) ​ $ 52,362 ​ $ 65 ​ $ (142) ​ $ 52,285 Commercial paper ​ ​ 12,345 ​ ​ 2 ​ ​ (1) ​ ​ 12,346 Asset-backed debt securities (2) ​ ​ 10,953 ​ ​ 42 ​ ​ (30) ​ ​ 10,965 Foreign government agency debt securities (3) ​ ​ 4,698 ​ ​ 43 ​ ​ — ​ ​ 4,741 U.S. government and government agency debt securities (4) ​ ​ 61,750 ​ ​ 8 ​ ​ (96) ​ ​ 61,662 Total marketable securities ​ $ 142,108 ​ $ 160 ​ $ (269) ​ $ 141,999 (1) Included in Corporate debt securities is $28.0 million with maturity dates between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (2) Included in Asset-backed debt securities is $6.2 million with maturity dates between one and three years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (3) Included in Foreign government agency debt securities is $4.7 million with a maturity date between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (4) Included in U.S. government and government agency debt securities is $23.9 million with maturity dates between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Book ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Value ​ Gain ​ Loss ​ Value Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities (1) ​ $ 40,626 ​ $ — ​ $ (251) ​ $ 40,375 Commercial paper ​ ​ 79,598 ​ ​ — ​ ​ — ​ ​ 79,598 Asset-backed debt securities (2) ​ ​ 14,641 ​ ​ 4 ​ ​ (123) ​ ​ 14,522 U.S. government and government agency debt securities (3) ​ ​ 50,571 ​ ​ — ​ ​ (530) ​ ​ 50,041 Total marketable securities ​ $ 185,436 ​ $ 4 ​ $ (904) ​ $ 184,536 (1) Included in Corporate debt securities is $4.8 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (2) Included in Asset-backed debt securities is $2.4 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (3) Included in U.S. government and government agency debt securities is $5.0 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2023
Property and Equipment, Net
Property and Equipment, Net	4. Property and Equipment, Net ​ Property and equipment, net consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Computer equipment $ 1,253 $ 1,381 Lab equipment ​ ​ 3,154 ​ ​ 2,010 Furniture and fixtures ​ ​ 558 ​ ​ 620 Leasehold improvements ​ ​ 817 ​ ​ 1,123 Property and equipment, gross ​ 5,782 ​ 5,134 Accumulated depreciation ​ (4,162) ​ (4,035) Property and equipment, net ​ $ 1,620 ​ $ 1,099 ​ Depreciation expense was $0.8 million, $0.7 million and $0.8 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Intangible Assets
Intangible Assets	5. Intangible Assets ​ Intangible assets consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Cost ​ Accumulated Amortization ​ ​ ​ Remaining ​ ​ December 31, ​ ​ December 31, ​ ​ December 31, ​ ​ December 31, (In thousands, except years) ​ Life (years) 2023 2022 2023 2022 Other intangible assets ​ ​ 3.6 ​ $ 751 ​ $ 751 ​ $ 482 ​ $ 407 In-process research and development ​ ​ n/a ​ ​ — ​ ​ 6,629 ​ ​ — ​ ​ — Total intangible assets ​ ​ ​ ​ $ 751 ​ $ 7,380 ​ $ 482 ​ $ 407 ​ Amortization expense was $75 thousand for each of the years ended December 31, 2023, 2022 and 2021. ​ As of December 31, 2023, estimated future amortization expense was as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ending (In thousands) ​ December 31, 2024 ​ 75 2025 ​ 75 2026 ​ ​ 75 2027 ​ ​ 44 Total ​ $ 269 ​

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2023
Accrued Expenses
Accrued Expenses	6. Accrued Expenses ​ Accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, (In thousands) 2023 2022 Employee compensation expenses ​ $ 3,910 ​ $ 5,295 Research and development expenses ​ ​ 6,661 ​ ​ 2,689 Licensing expenses ​ ​ 5,478 ​ ​ 500 Restructuring expenses (Note 15) ​ ​ 3,112 ​ ​ — Other ​ 285 ​ 217 Total accrued expenses ​ $ 19,446 ​ $ 8,701 ​

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt
Debt	7. Debt ​ Loan and Security Agreement – Silicon Valley Bank ​ In March 2020, the Company entered into a Loan and Security Agreement with Silicon Valley Bank (“SVB”). The Loan and Security Agreement provided for $11.0 million in term loans, of which the Company borrowed the entire amount on March 30, 2020. In connection with the Loan and Security Agreement, the Company issued to SVB a warrant to purchase up to 460,251 shares of common stock (the “Warrant”) (see Note 8). The proceeds of the Loan and Security Agreement were allocated to the term loan and Warrant using a relative fair value approach. ​ In July 2021, the Company repaid in full the $11.0 million that was outstanding under the Loan and Security Agreement, together with all accrued and unpaid interest and fees as of the payoff date, for a total payment of $11.7 million. Following this repayment, all of the Company’s obligations under the Loan and Security Agreement are deemed to be terminated, except as set forth in the agreement. ​

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Stockholders' Equity
Stockholders' Equity	8. Stockholders’ Equity ​ Preferred Stock ​ As of December 31, 2023 and 2022, the Company’s amended and restated certificate of incorporation (the “Charter”) authorized the Company to issue 10,000,000 shares of undesignated preferred stock. There were no shares of preferred stock outstanding as of December 31, 2023 and 2022. ​ Common Stock ​ On June 1, 2023, at the 2023 Annual Meeting of Stockholders, the Company’s stockholders approved an amendment to the Charter to increase the authorized number of shares of common stock from 100,000,000 shares to 200,000,000 shares. On June 1, 2023, the Company filed a Certificate of Amendment to the Charter with the Secretary of State of the State of Delaware, which became effective upon filing. ​ As of December 31, 2023 and 2022, the Company’s Charter authorized the Company to issue 200,000,000 and 100,000,000 shares, respectively, of $0.00001 par value common stock. There were 70,894,889 and 66,688,647 shares of common stock issued outstanding ​ Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to any preferential dividend rights of any series of preferred stock that may be outstanding. No dividends have been declared through December 31, 2023. ​ Warrants ​ The Warrant issued to SVB in March 2020 had an initial exercise price of $0.956 per share, subject to adjustment as provided in the Warrant. The Warrant became immediately exercisable in full upon the funding of the term loan facility. The Company assigned a fair value of $0.4 million to the Warrant using a Black-Scholes valuation methodology, and also concluded that the Warrant was indexed to its own stock and therefore classified the Warrant as an equity instrument. In January 2021, SVB net exercised the Warrant in full, and the Company issued to SVB 388,119 shares of common stock. ​ January 2021 Public Offering ​ In January 2021, the Company closed a public offering in which it sold 6,306,271 shares of common stock at a price to the public of $17.50 per share, for aggregate gross proceeds of $110.4 million. The Company paid underwriting discounts and commissions of $6.6 million, and also incurred expenses of $0.4 million in connection with the offering. As a result, the net offering proceeds received by the Company, after deducting underwriting discounts, commissions and offering expenses, were $103.3 million. ​ June 2021 Public Offering ​ In June 2021, the Company closed a public offering in which it sold 8,098,592 shares of common stock at a price to the public of $17.75 per share, for aggregate gross proceeds of $143.8 million. The Company paid underwriting discounts and commissions of $8.6 million, and also incurred expenses of $0.3 million in connection with the offering. As a result, the net offering proceeds received by the Company, after deducting underwriting discounts, commissions and offering expenses, were $134.9 million. ​ Sales of Common Stock Pursuant to At-The-Market Facility ​ In April 2022, the Company sold 4.8 million shares of its common stock for aggregate gross proceeds of $75.0 million, pursuant to a sales agreement with SVB Securities LLC and Cantor Fitzgerald & Co., as sales agents, dated May 20, 2021. The Company paid selling commissions and other fees of $2.3 million in connection with the sale. ​ In April 2023, the Company sold 3.4 million shares of its common stock for aggregate gross proceeds of $27.5 million, pursuant to a sales agreement with SVB Securities LLC and Cantor Fitzgerald & Co., as sales agents, dated February 23, 2023. The Company paid selling commissions of $0.8 million in connection with the sale. ​

Stock-Based Awards

Stock-Based Awards	12 Months Ended
	Dec. 31, 2023
Stock-Based Awards
Stock-Based Awards	9. Stock-Based Awards ​ 2015 Equity Incentive Plan ​ In September 2015, the Company’s board of directors adopted the 2015 Equity Incentive Plan (the “2015 Plan”), and the Company’s stockholders approved the 2015 Plan. The 2015 Plan became effective in connection with the Company’s initial public offering in October 2015. Beginning at the time the 2015 Plan became effective, no further grants may be made under the Company’s 2012 Equity Compensation Plan, as amended and restated (the “2012 Plan”). The 2015 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, RSU awards, performance stock awards, cash-based awards and other stock-based awards. The number of shares initially reserved for issuance under the 2015 Plan was 1,643,872 shares of common stock. The number of shares of common stock that may be issued under the 2015 Plan will automatically increase on January 1 of each year ending on January 1, 2025, in an amount equal to the lesser of (i) 4.0% of the shares of the Company’s common stock outstanding on December 31 of the preceding calendar year or (ii) an amount determined by the Company’s board of directors. The shares of common stock underlying any awards that expire, are otherwise terminated, settled in cash or repurchased by the Company under the 2015 Plan and the 2012 Plan will be added back to the shares of common stock available for issuance under the 2015 Plan. As of December 31, 2023, 3,703,234 shares remained available for grant under the 2015 Plan. As of January 1, 2024, the number of shares of common stock that may be issued under the 2015 Plan was automatically increased by 2,835,795 shares. The Company had 5,668,063 stock options and 1,521,940 RSUs outstanding as of December 31, 2023 under the 2015 Plan. ​ 2017 Inducement Plan ​ In July 2017, the Company’s board of directors adopted the 2017 Inducement Plan (the “2017 Inducement Plan”). The 2017 Inducement Plan is a non-stockholder approved stock plan adopted pursuant to the “inducement exception” provided under Nasdaq listing rules. The Company had 370,600 stock options outstanding as of December 31, 2023 under the 2017 Inducement Plan. All shares of common stock that were eligible for issuance under the 2017 Inducement Plan after October 1, 2018, including any shares underlying any awards that expire or are otherwise terminated, reacquired to satisfy tax withholding obligations, settled in cash or repurchased by the Company in the future that would have been eligible for re-issuance under the 2017 Inducement Plan, were retired. ​ 2012 Equity Compensation Plan ​ In August 2012, the Company’s board of directors adopted the 2012 Equity Incentive Plan (“2012 Plan”), and the Company’s stockholders approved the 2012 Plan. Upon the 2015 Plan becoming effective, no further grants can be made under the 2012 Plan. The Company had 380,792 stock options outstanding as of December 31, 2023 under the 2012 Plan. ​ Stock Option Valuation ​ The weighted average assumptions the Company used to estimate the fair value of stock options granted during the years ended December 31, 2023, 2022 and 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2023 ​ ​ 2022 ​ ​ 2021 Risk-free interest rate 3.55 % ​ 2.22 % ​ 0.92 % Expected term (in years) 6.2 ​ ​ 6.2 ​ ​ 6.2 ​ Expected volatility 77.73 % ​ 77.95 % ​ 76.60 % Expected dividend yield 0 % ​ 0 % ​ 0 % ​ The Company recognizes compensation expense for awards over their vesting period. Compensation expense for awards includes the impact of forfeitures in the period when they occur. ​ Stock Options ​ The following table summarizes stock option activity for the years ended December 31, 2023, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number ​ Exercise ​ Contractual ​ Intrinsic (In thousands, except share and per share data and years) ​ of Shares ​ Price ​ Term ​ Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ ​ ​ Outstanding as of December 31, 2020 ​ 2,871,498 ​ $ 15.16 6.8 ​ $ 4,890 Granted ​ 1,068,100 ​ 23.44 ​ ​ ​ ​ ​ Exercised ​ (115,548) ​ 12.63 ​ ​ ​ ​ 1,373 Forfeited and cancelled ​ (31,600) ​ 23.26 ​ ​ ​ ​ ​ Outstanding as of December 31, 2021 ​ 3,792,450 ​ $ 17.50 6.8 ​ $ 13,710 Granted ​ 2,548,750 ​ 14.40 ​ ​ ​ ​ ​ Exercised ​ (88,172) ​ 1.78 ​ ​ ​ ​ 1,120 Forfeited and cancelled ​ (1,085,864) ​ 18.44 ​ ​ ​ ​ ​ Outstanding as of December 31, 2022 5,167,164 ​ $ 16.04 7.2 ​ $ 15,288 Granted 2,241,550 ​ ​ 15.62 ​ ​ ​ ​ ​ Exercised ​ (71,092) ​ ​ 1.31 ​ ​ ​ ​ 473 Forfeited and cancelled (918,167) ​ ​ 16.85 ​ ​ ​ ​ ​ Outstanding as of December 31, 2023 6,419,455 ​ $ 15.94 ​ 7.1 ​ $ 14 Options vested and expected to vest as of December 31, 2023 6,419,455 ​ $ 15.94 7.1 ​ $ 14 Options exercisable as of December 31, 2023 2,879,529 ​ $ 16.55 5.1 ​ $ 14 ​ The weighted average grant date fair value of stock options granted during the years ended December 31, 2023, 2022 and 2021 was $10.98, $9.95, and $15.67 per share, respectively. ​ Restricted Stock Units ​ The following table summarizes RSU activity for the years ended December 31, 2023, 2022 and 2021. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ ​ Grant Date ​ Aggregate ​ ​ Number ​ Fair Value ​ Intrinsic (In thousands, except share and per share data) ​ of Shares ​ Per Share ​ Value Outstanding as of December 31, 2020 ​ 2,244,157 ​ $ 3.83 ​ ​ ​ Granted ​ 664,948 ​ ​ 23.33 ​ ​ ​ Vested ​ (1,340,042) ​ ​ 3.18 ​ $ 31,492 Forfeited and cancelled ​ (72,117) ​ ​ 10.36 ​ ​ ​ Outstanding as of December 31, 2021 ​ 1,496,946 ​ $ 12.75 ​ ​ ​ Granted ​ 936,563 ​ ​ 14.43 ​ ​ ​ Vested ​ (533,212) ​ ​ 11.61 ​ $ 7,943 Forfeited and cancelled ​ (379,567) ​ ​ 13.40 ​ ​ ​ Outstanding as of December 31, 2022 ​ 1,520,730 ​ $ 14.02 ​ ​ ​ Granted ​ 993,662 ​ ​ 15.17 ​ ​ ​ Vested ​ (745,279) ​ ​ 11.72 ​ $ 8,262 Forfeited and cancelled ​ (247,173) ​ ​ 15.15 ​ ​ ​ Outstanding as of December 31, 2023 ​ 1,521,940 ​ $ 15.72 ​ ​ ​ ​ Stock-Based Compensation ​ Stock-based compensation expense included in total costs and expenses on the consolidated statement of operations included the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, (In thousands) 2023 2022 2021 Cost of revenue $ 1,456 $ 1,151 ​ $ 981 Research and development ​ ​ ​ 6,801 ​ ​ 3,745 ​ ​ 3,866 General and administrative ​ ​ 12,285 ​ 10,143 ​ 9,213 Total stock-based compensation expense ​ ​ $ 20,542 ​ $ 15,039 ​ $ 14,060 ​ As of December 31, 2023, the Company had unrecognized stock-based compensation expense for stock options and RSUs of $30.0 million and $17.7 million, respectively, which is expected to be recognized over weighted average periods of 2.7 years and 2.6 years, respectively.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2023
Net Loss per Share
Net Loss per Share	10. Net Loss per Share ​ Basic and diluted net loss per share is summarized in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, (In thousands, except for share and per share data) ​ 2023 2022 2021 ​ Numerator: ​ ​ ​ ​ ​ Net loss ​ ​ $ (88,481) ​ $ (86,908) ​ $ (90,865) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares of common stock outstanding, basic and diluted ​ ​ 69,808,855 ​ 65,213,944 ​ 56,730,583 ​ Net loss per share, basic and diluted ​ ​ $ (1.27) ​ $ (1.33) ​ $ (1.60) ​ ​ The Company’s potentially dilutive securities, which included stock options and RSUs, have been excluded from the computation of diluted net loss per share since the effect would be to reduce the net loss per share. Therefore, the weighted average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share is the same. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 Options to purchase common stock ​ 6,419,455 ​ 5,167,164 3,792,450 ​ Restricted stock unit awards ​ 1,521,940 ​ 1,520,730 ​ 1,496,946 ​ Total potential shares of common stock ​ 7,941,395 ​ 6,687,894 5,289,396 ​ ​

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases
Leases	11. Leases ​ The Company has operating leases for office space and laboratory facilities. The components of lease expense were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, (In thousands) 2023 2022 2021 Operating lease expense $ 1,092 $ 1,013 $ 1,013 ​ Rent expense was $1.1 million for the year ended December 31, 2023, and $1.0 million for each of the years ended December 31, 2022 and 2021, which was recognized on a straight-line basis over the term of the lease. ​ Operating Leases ​ Agreements for Office and Laboratory Space ​ The Company had a sublease agreement pursuant to which it subleased 33,019 square feet of office space for its headquarters in Wayne, Pennsylvania, which expired on October 31, 2023. In December 2020, the Company entered into a sub-sublease agreement under which it sub-subleased 8,115 square feet to a third party. The sub-sublease was terminated in December 2022. ​ In May 2023, the Company entered into a new lease agreement pursuant to which it leases 11,564 square feet of office space for its headquarters in Wayne, Pennsylvania. The lease commenced on November 1, 2023 and has a term that runs through February 2029. ​ In February 2019, the Company entered into a sublease agreement for 20,433 square feet of office and laboratory space in St. Louis, Missouri. The lease commenced in June 2019 and has a term that runs through June 2029. In January 2023, the Company amended the sublease agreement to add an additional 6,261 square feet of office and laboratory space effective February 2023, which term runs concurrently with the existing term. ​ Supplemental balance sheet information related to operating leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Operating Leases: ​ ​ ​ ​ ​ ​ Gross cost ​ $ 5,094 ​ $ 5,240 Accumulated amortization ​ ​ (1,235) ​ ​ (2,560) Other assets ​ $ 3,859 ​ $ 2,680 ​ ​ ​ ​ ​ ​ ​ Current portion of lease liabilities ​ $ 426 ​ $ 684 Other liabilities ​ ​ 3,074 ​ ​ 1,570 Total operating lease liabilities ​ $ 3,500 ​ $ 2,254 ​ Amortization expense related to operating lease right-of-use assets and accretion of operating lease liabilities totaled $0.8 million for the year ended December 31, 2023, and $1.0 million for each of the years ended December 31, 2022 and 2021. ​ Supplemental information related to operating leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended (In thousands, except for years and percentages) ​ December 31, Supplemental Cash Flow Lease Information: ​ 2023 ​ 2022 2021 Operating cash flows from operating leases ​ $ 974 ​ $ 846 ​ $ 924 ​ Leased assets obtained in exchange for new operating lease liabilities ​ $ 2,010 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average Remaining Lease Term (in years): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating leases ​ ​ 5.3 ​ ​ 5.2 ​ ​ 5.4 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average Discount Rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating leases ​ ​ 10.2 % ​ 10.1 % ​ 10.1 % ​ Future minimum lease payments under operating lease agreements are as follows: ​ ​ ​ ​ ​ (In thousands) ​ ​ Operating Year Ending December 31, Leases 2024 ​ $ 766 2025 ​ ​ 847 2026 ​ ​ 868 2027 ​ ​ 890 2028 ​ ​ 912 Thereafter ​ ​ 316 Total undiscounted lease payments ​ ​ 4,598 Less: unrecognized interest ​ ​ (1,098) Total lease liability ​ $ 3,500 ​ ​

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Taxes
Income Taxes	12. Income Taxes ​ During the years ended December 31, 2023, 2022 and 2021, the Company did not record an income tax benefit for net operating losses incurred in each year due to the uncertainty of realizing a benefit from those items. ​ Loss before income taxes is allocated as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ (In thousands) ​ 2023 ​ 2022 ​ 2021 ​ U.S. operations ​ $ (88,848) ​ $ (86,908) ​ $ (90,865) ​ Foreign operations ​ ​ — ​ ​ — ​ ​ — ​ Loss before income taxes ​ $ (88,848) ​ $ (86,908) ​ $ (90,865) ​ ​ A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 ​ 2022 2021 Federal statutory income tax rate (21.0) % (21.0) % (21.0) % State taxes, net of federal benefit ​ (1.7) (2.3) (7.7) ​ Impact of state rate changes ​ 17.7 ​ — ​ — ​ Research and development tax credits ​ (5.9) (4.3) (3.0) ​ Excess equity compensation tax benefit, net of officer limitation ​ 0.6 ​ 0.2 ​ (3.9) ​ Revaluation of contingent consideration ​ (6.3) ​ 1.1 ​ 5.6 ​ Non-deductible royalty payments ​ 4.3 ​ — ​ — ​ Change in deferred tax asset valuation allowance ​ 11.7 ​ 26.3 ​ 30.0 ​ Other ​ 0.2 — — ​ Effective income tax rate ​ (0.4) % — % — % ​ Deferred tax liabilities, net consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Deferred tax assets: ​ ​ ​ Net operating loss carryforwards ​ $ 119,155 ​ $ 120,554 ​ Capitalized start-up costs ​ ​ 3,812 ​ ​ 5,506 ​ Research and development tax credit carryforwards ​ 20,505 ​ 15,233 ​ Section 174 research and development capitalization ​ ​ 30,984 ​ ​ 19,639 ​ Capitalized research and development expense ​ 2,359 ​ 5,448 ​ Stock‑based compensation expense ​ 18,055 ​ 19,432 ​ Accrued compensation ​ ​ 1,219 ​ ​ 1,146 ​ Lease liabilities ​ ​ 774 ​ ​ 558 ​ Other ​ 407 ​ 534 ​ Total deferred tax assets ​ 197,270 ​ 188,050 ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Property and equipment ​ ​ (187) ​ ​ (137) ​ Intangible asset ​ ​ — ​ ​ (1,576) ​ Right-to-use assets ​ ​ (853) ​ ​ (651) ​ Other ​ (1,106) ​ (1,365) ​ Total deferred tax liabilities ​ (2,146) ​ (3,729) ​ Valuation allowance ​ (195,124) ​ (184,688) ​ Deferred tax liabilities, net ​ $ — ​ $ (367) ​ ​ As of December 31, 2023, the Company had federal and state net operating loss (“NOL”) carryforwards of $464.8 million and $395.3 million, respectively, which will begin to expire in 2032. As of December 31, 2023, the Company also had federal research and development tax credit carryforwards of $20.4 million which will begin to expire in 2032, and state research and development tax credit carryforwards of $0.1 million which will begin to expire in 2022. ​ The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. The Company considered its history of cumulative net losses incurred since inception, its lack of substantial revenue generated to date, and its forecasted future operating losses and concluded that it is more likely than not that the Company will not realize the benefits of its deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2023 and 2022. The Company evaluates positive and negative evidence of its ability to realize deferred tax assets at each reporting period. ​ Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2023, 2022 and 2021, which related primarily to the increases in NOLs, capitalized research and development costs, and research and development tax credit carryforwards, were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, (In thousands) ​ ​ 2023 ​ ​ 2022 ​ ​ 2021 Valuation allowance at beginning of year ​ $ (184,688) $ (161,824) $ (134,559) ​ Decreases recorded as benefit to income tax provision ​ — ​ — ​ — ​ Increases recorded to income tax provision ​ (10,436) ​ (22,864) ​ (27,265) ​ Valuation allowance as of end of year ​ $ (195,124) ​ $ (184,688) ​ $ (161,824) ​ ​ The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are still open under statute from 2021 to the present. All open years may be examined to the extent that tax credit or NOLs are used in future periods. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2023 and 2022.

Agreements Related to Intellect

Agreements Related to Intellectual Property	12 Months Ended
	Dec. 31, 2023
Agreements Related to Intellectual Property
Agreements Related to Intellectual Property	13. Agreements Related to Intellectual Property ​ License Agreement – Sun Pharmaceutical Industries, Inc. ​ In December 2023, the Company entered into an exclusive patent license agreement with Sun Pharmaceutical Industries, Inc. (“Sun Pharma”). Under the license agreement, the Company granted Sun Pharma exclusive rights under certain patents that the Company exclusively licenses from a third party. The patents relate to the use of deuruxolitinib, Sun Pharma’s Janus kinase (“JAK”) inhibitor, or other isotopic forms of ruxolitinib, to treat alopecia areata or androgenetic alopecia. Under the license agreement, Sun Pharma has agreed to pay the Company an upfront payment, regulatory and commercial milestone payments, and a mid single-digit tiered royalty calculated as a percentage of Sun Pharma’s net sales. The Company has separate contractual obligations under which the Company has agreed to pay to third parties a portion of the consideration it may receive under the license agreement. ​ Upon execution of the agreement, the Company received an upfront payment of $15.0 million from Sun Pharma, a portion of which was payable to third parties. ​ License Agreement – Pediatrix Therapeutics, Inc. ​ In November 2022, the Company entered into a license agreement with Pediatrix Therapeutics, Inc. (“Pediatrix”), under which the Company granted Pediatrix the exclusive rights to develop, manufacture and commercialize ATI-1777 in Greater China. Pediatrix has agreed to pay the Company an upfront payment, development, regulatory and commercial milestone payments, and a tiered royalty ranging from a low-to-high single digit percentage of net sales of ATI-1777 by Pediatrix in Greater China. A portion of consideration received from Pediatrix is payable to the former Confluence equity holders as described below. ​ Upon execution of the agreement, the Company received an upfront payment of $5.0 million from Pediatrix, a portion of which was payable to the former Confluence equity holders as described below. ​ License Agreement – Eli Lilly and Company ​ In August 2022, the Company entered into a non-exclusive patent license agreement with Eli Lilly and Company (“Lilly”). Under the license agreement, the Company granted Lilly non-exclusive rights under certain patents and patent applications that the Company exclusively licenses from a third party. The patents and patent applications relate to the use of baricitinib, Lilly’s JAK inhibitor, to treat alopecia areata. Under the license agreement, Lilly has agreed to pay the Company an upfront payment, regulatory and commercial milestone payments, anniversary payments, and a low single-digit royalty calculated as a percentage of Lilly’s net sales of baricitinib for the treatment of alopecia areata. The Company has separate contractual obligations under which the Company has agreed to pay to third parties an amount equal to any regulatory and commercial milestone payments it receives under the Lilly license agreement, as well as a portion of the upfront consideration and a portion of the royalties it may receive under the license agreement. ​ During the years ended December 31, 2023 and 2022, the Company recorded licensing revenue under this agreement of $12.7 million and $17.8 million, respectively, from Lilly, a portion of which was payable to third parties. ​ Asset Purchase Agreement – EPI Health, LLC ​ In October 2019, the Company sold RHOFADE (oxymetazoline hydrochloride) cream, 1% (“RHOFADE”) to EPI Health, LLC (“EPI Health”) pursuant to an asset purchase agreement. In July 2023, EPI Health filed a voluntary petition for relief under Chapter 11 of the United States Bankruptcy Code. Through the bankruptcy process, EPI Health and its parent company, Novan, Inc., sold the RHOFADE assets to a third party, which excluded the Company’s asset purchase agreement with EPI Health and the outstanding amounts due. The sale was approved by the bankruptcy court in September 2023. As a result of the bankruptcy proceedings, the Company recorded an allowance for doubtful accounts resulting in $1.3 million of bad debt expense for the year ended December 31, 2023, representing all amounts that were due and outstanding by EPI Health. ​ Agreement and Plan of Merger – Confluence ​ In August 2017, the Company entered into an Agreement and Plan of Merger, pursuant to which it acquired Confluence (the “Confluence Agreement”). Under the Confluence Agreement, the Company agreed to pay the former Confluence equity holders aggregate remaining contingent consideration of up to $75.0 million based upon the achievement of specified regulatory and commercial milestones set forth in the Confluence Agreement. In addition, the Company agreed to pay the former Confluence equity holders future royalty payments calculated as a low single-digit percentage of annual net sales, subject to specified reductions, limitations and other adjustments, until the date that all of the patent rights for that product have expired, as determined on a country-by-country and product-by-product basis or, in specified circumstances, ten years from the first commercial sale of such product. In addition to the payments described above, if the Company sells, licenses or transfers any of the intellectual property acquired from Confluence pursuant to the Confluence Agreement to a third party, the Company will be obligated to pay the former Confluence equity holders a portion of any consideration received from such sale, license or transfer in specified circumstances. ​ As of December 31, 2023 and December 31, 2022, the balance of the Company’s contingent consideration liability was $6.2 million and $33.1 million, respectively (see Note 3). ​

Retirement Savings Plan

Retirement Savings Plan	12 Months Ended
	Dec. 31, 2023
Retirement Savings Plan
Retirement Savings Plan	14. Retirement Savings Plan ​ The Company has a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the plan may be made at the discretion of the Company’s board of directors. The Company has elected to match employee contributions to the 401(k) Plan up to 4% of the employee’s earnings, subject to certain limitations. Company contributions under the 401(k) Plan were $0.7 million, $0.5 million and $0.3 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2023
Restructuring Charges.
Restructuring Charges	15. Restructuring Charges ​ In December 2023, the Company’s board of directors approved a reduction of the Company’s workforce by approximately 46%, which the Company expects to be substantially completed by June 2024. This action was taken in order to streamline operations, reduce costs and preserve capital. As a result, the Company terminated certain employees (“terminated employees”) and gave notice to additional employees (“noticed employees”) who were asked to provide transition services through termination dates ranging between one ​ During the year ended December 31, 2023, the Company recorded a restructuring charge of $3.1 million which represents a one-time termination benefit for impacted employees with retention periods less than the sixty-day minimum retention period, which was triggered immediately upon either terminating or giving notice to the impacted employees. Of the $3.1 million of expenses incurred during the year ended December 31, 2023, $2.2 million, $0.9 million and $19 thousand were recorded in research and development expense, general and administrative expense and cost of revenue, respectively, in the consolidated statement of operations and comprehensive loss. The Company is expensing the cost of cash severance payments, other benefits and annual bonus payments for noticed employees with retention periods more than the minimum retention period over their respective service terms.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2023
Segment Information
Segment Information	16. Segment Information ​ The Company has two reportable segments, therapeutics and contract research. The therapeutics segment is focused on identifying and developing innovative therapies to address significant unmet needs for immuno-inflammatory diseases and earns revenue through licensing of the Company’s intellectual property. The contract research segment earns revenue from the provision of laboratory services. All intersegment revenue has been eliminated in the Company’s consolidated statement of operations. All customers and revenue pertaining to the Company’s segments are based in the United States. Corporate and other includes general and administrative expenses as well as eliminations of intercompany transactions. The Company does not report balance sheet information by segment since it is not reviewed by the chief operating decision maker, and all of the Company’s tangible assets are held in the United States. ​ The Company’s results of operations by segment for the years ended December 31, 2023, 2022 and 2021 are summarized in the tables below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2023 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 28,214 ​ $ 3,035 ​ $ — ​ $ 31,249 Intercompany revenue ​ ​ — ​ ​ 16,543 ​ ​ (16,543) ​ ​ — Cost of revenue ​ ​ — ​ ​ 18,941 ​ ​ (15,537) ​ ​ 3,404 Research and development ​ ​ 97,188 ​ ​ — ​ ​ (1,006) ​ ​ 96,182 General and administrative ​ ​ — ​ ​ 4,561 ​ ​ 26,940 ​ ​ 31,501 Licensing ​ ​ 14,658 ​ ​ — ​ ​ — ​ ​ 14,658 Revaluation of contingent consideration ​ ​ (26,900) ​ ​ — ​ ​ — ​ ​ (26,900) Intangible asset impairment ​ ​ 6,629 ​ ​ — ​ ​ — ​ ​ 6,629 Restructuring expense ​ ​ 2,202 ​ ​ 19 ​ ​ 911 ​ ​ 3,132 Loss from operations ​ $ (65,563) ​ $ (3,943) ​ $ (27,851) ​ $ (97,357) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2022 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 25,356 ​ $ 4,396 ​ $ — ​ $ 29,752 Intercompany revenue ​ ​ — ​ ​ 12,609 ​ ​ (12,609) ​ ​ — Cost of revenue ​ ​ — ​ ​ 15,847 ​ ​ (11,824) ​ ​ 4,023 Research and development ​ ​ 78,599 ​ ​ — ​ ​ (786) ​ ​ 77,813 General and administrative ​ ​ — ​ ​ 3,505 ​ ​ 21,628 ​ ​ 25,133 Licensing ​ ​ 7,937 ​ ​ — ​ ​ — ​ ​ 7,937 Revaluation of contingent consideration ​ ​ 4,700 ​ ​ — ​ ​ — ​ ​ 4,700 Loss from operations ​ $ (65,880) ​ $ (2,347) ​ $ (21,627) ​ $ (89,854) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2021 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 932 ​ $ 5,829 ​ $ — ​ $ 6,761 Intercompany revenue ​ ​ — ​ ​ 7,618 ​ ​ (7,618) ​ ​ — Cost of revenue ​ ​ — ​ ​ 11,885 ​ ​ (7,172) ​ ​ 4,713 Research and development ​ ​ 44,259 ​ ​ — ​ ​ (446) ​ ​ 43,813 General and administrative ​ ​ — ​ ​ 3,047 ​ ​ 20,572 ​ ​ 23,619 Revaluation of contingent consideration ​ ​ 24,339 ​ ​ — ​ ​ — ​ ​ 24,339 Loss from operations ​ $ (67,666) ​ $ (1,485) ​ $ (20,572) ​ $ (89,723) ​

Legal Proceedings

Legal Proceedings	12 Months Ended
	Dec. 31, 2023
Legal Proceedings
Legal Proceedings	17. Legal Proceedings ​ Securities Class Action ​ On July 30, 2019, plaintiff Linda Rosi (“Rosi”) filed a putative class action complaint captioned Rosi v. Aclaris Therapeutics, Inc., et al. Fulcher v. Aclaris Therapeutics, Inc., et al.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation ​ The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements of the Company include the accounts of the operating parent company, Aclaris Therapeutics, Inc., and its wholly owned subsidiaries. All intercompany transactions have been eliminated. Based upon the Company’s revenue, the Company believes that gross profit does not provide a meaningful measure of profitability and, therefore, has not included a line item for gross profit on the consolidated statement of operations.
Reclassifications	Reclassifications ​ Certain prior year amounts have been reclassified to conform to the current year financial statement presentation.
Discontinued Operations	Discontinued Operations ​ In September 2019, the Company announced the completion of a strategic review and its decision to refocus its resources on its immuno-inflammatory development programs and to actively seek partners for its commercial products. ​ As of December 31, 2023 and 2022, the Company had $2.2 million in accrued expenses reported as discontinued operations in the Company’s consolidated balance sheet.
Use of Estimates	Use of Estimates ​ The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, contingent consideration and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require an update to its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from the Company’s estimates.
Revenue Recognition	Revenue Recognition ​ The Company accounts for revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers. Under ASC Topic 606, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. ​ ​ Contract Research ​ The Company earns contract research revenue from the provision of laboratory services. Contract research revenue is generally evidenced by contracts with clients which are on an agreed upon fixed-price, fee-for-service basis and are generally billed on a monthly basis in arrears for services rendered. Revenue related to these contracts is generally recognized as the laboratory services are performed, based upon the rates specified in the contracts. Under ASC Topic 606, the Company elected to apply the “right to invoice” practical expedient when recognizing contract research revenue and as such, recognizes revenue in the amount which it has the right to invoice. ASC Topic 606 also provides an optional exemption, which the Company has elected to apply, from disclosing remaining performance obligations when revenue is recognized from the satisfaction of the performance obligation in accordance with the “right to invoice” practical expedient. ​ Licensing Revenue ​ Licenses of Intellectual Property ​ Milestone and Royalty Payments
Cash Equivalents	Cash Equivalents ​ The Company considers all short-term, highly liquid investments with original maturities of three months or less at acquisition date to be cash equivalents. Cash equivalents, which have consisted of money market funds and commercial paper, are stated at fair value.
Marketable Securities	Marketable Securities ​ Marketable securities with original maturities of greater than three months and remaining maturities of less than one year from the balance sheet date are classified as short-term. Marketable securities with remaining maturities of greater than one year from the balance sheet date are classified as long-term. ​ The Company classifies all marketable securities as available-for-sale securities. The Company’s marketable securities are measured and reported at fair value using either quoted prices in active markets for identical securities or quoted prices in markets that are not active for identical or similar securities. Unrealized gains and losses are reported as a separate component of stockholders’ equity. The cost of securities sold is determined on a specific identification basis, and realized gains and losses, if any, are included in other expense, net within the consolidated statement of operations and comprehensive loss. If any adjustment to fair value reflects a decline in the value of the investment, the Company considers available evidence to evaluate the extent to which the decline is “other than temporary” and reduces the investment to fair value through a charge to the statement of operations and comprehensive loss.
Property and Equipment	Property and Equipment ​ Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. Computer equipment is depreciated over three years. Laboratory equipment is depreciated over three
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets ​ Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows.
Intangible Assets	Intangible Assets ​ Intangible assets include both definite-lived and indefinite-lived assets. Definite-lived intangible assets consist of a drug discovery platform the Company acquired through the acquisition of Confluence. Definite-lived intangible assets are amortized over their estimated useful life based on the pattern over which the intangible assets are consumed or otherwise used up. If that pattern cannot be reliably determined, the straight-line method of amortization is used. Indefinite-lived intangible assets consisted of an in-process research and development (“IPR&D”) drug candidate acquired through the acquisition of Confluence. IPR&D assets are considered indefinite-lived until the completion or abandonment of the associated research and development efforts. The cost of IPR&D is either amortized over its estimated useful life beginning when the underlying drug candidate is approved and launched commercially, or expensed immediately if development of the drug candidate is abandoned or otherwise impaired. ​ Definite-lived intangible assets are tested for impairment when events or changes in circumstances indicate that the carrying value of the asset may not be recoverable. Indefinite-lived intangible assets are tested for impairment at least annually, which the Company performs during the fourth quarter, or when indicators of an impairment are present. The Company recognizes impairment losses when and to the extent that the estimated fair value of an intangible asset is less than its carrying value. ​ During the quarter ended December 31, 2023, the Company performed an impairment analysis on the IPR&D intangible asset due to the Company’s decision to discontinue further development of the drug candidate in immuno-inflammatory diseases. The Company’s impairment analysis resulted in a fair value of the IPR&D intangible asset which was less than the carrying value. As a result, the Company recorded an impairment charge of $6.6 million, the full balance of the IPR&D intangible asset.
Leases	Leases ​ Leases represent a company’s right to use an underlying asset and a corresponding obligation to make payments to a lessor for the right to use those assets. The Company evaluates leases at their inception to determine if they are an operating lease or a finance lease. A lease is accounted for as a finance lease if it meets one of the following five criteria: the lease has a purchase option that is reasonably certain of being exercised, the present value of the future cash flows are substantially all of the fair market value of the underlying asset, the lease term is for a significant portion of the remaining economic life of the underlying asset, the title to the underlying asset transfers at the end of the lease term, or if the underlying asset is of such a specialized nature that it is expected to have no alternative uses to the lessor at the end of the term. Leases that do not meet the finance lease criteria are accounted for as an operating lease. ​ The Company recognizes assets and liabilities for leases at their inception based upon the present value of all payments due under the lease. The Company uses an incremental borrowing rate to determine the present value of operating leases. The Company determines incremental borrowing rates by referencing collateralized borrowing rates for debt instruments with terms similar to the respective lease. The Company recognizes expense for operating leases on a straight-line basis over the term of each lease. The Company includes estimates for any residual value guarantee obligations under its leases in lease liabilities recorded on its consolidated balance sheet. ​ Right-of-use assets are included in other assets on the Company’s consolidated balance sheet for operating leases. Obligations for lease payments are included in current portion of lease liabilities and other liabilities on the Company’s consolidated balance sheet for operating leases.
Contingent Consideration	Contingent Consideration ​ The Company records a contingent consideration liability related to future potential payments resulting from the acquisition of Confluence based upon significant unobservable inputs including the achievement of regulatory and commercial milestones, as well as estimated future sales levels and the discount rates applied to calculate the present value of the potential payments. Significant judgement is involved in determining the appropriateness of these assumptions. These assumptions are considered Level 3 inputs. Revaluation of the contingent consideration liability can result from changes to one or more of these assumptions. The Company evaluates the fair value estimate of the contingent consideration liability on a quarterly basis with changes, if any, recorded as income or expense in the consolidated statement of operations. ​ The fair value of contingent consideration is estimated using a probability-weighted expected payment model for regulatory milestone payments and a Monte Carlo simulation model for commercial milestone and royalty payments and then applying a risk-adjusted discount rate to calculate the present value of the potential payments. Significant assumptions used in the Company’s estimates include the probability of achieving regulatory milestones and commencing commercialization, which are based on an asset’s current stage of development and a review of existing clinical data. The probability of success on the year of each potential payment.
Research and Development Costs	Research and Development Costs ​ Research and development costs are expensed as incurred. Research and development expenses include salaries, stock-based compensation and benefits of employees, and other operational costs related to the Company’s research and development activities, including depreciation expenses and the cost of research and development contracts which the Company has entered into with outside vendors to conduct both preclinical studies and clinical trials. Significant judgment and estimates are made in determining the amount of research and development costs recognized in each reporting period. The Company analyzes the progress of its preclinical studies and clinical trials, completion of milestone events, invoices received and contracted costs when estimating research and development costs. Actual results could differ from the Company’s estimates. The Company’s historical estimates for research and development costs have not been materially different from the actual costs.
Stock-Based Compensation	Stock-Based Compensation ​ The Company measures the compensation expense of stock-based awards granted to employees and directors using the grant date fair value of the award. The Company has issued stock options and restricted stock unit (“RSU”) awards with service-based vesting conditions, as well as with performance-based vesting conditions. The Company has not issued awards that include market-based conditions. For service-based awards the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period, which is typically four years. For performance-based awards the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period beginning in the period that it becomes probable the performance conditions will occur. At each balance sheet date, the Company evaluates whether any performance conditions related to a performance-based award have changed. The effect of any change in performance conditions would be recognized as a cumulative catch-up adjustment in the period such change occurs, and any remaining unrecognized compensation expense would be recognized on a straight-line basis over the remaining requisite service period. The impact of forfeitures is recognized in the period in which they occur. ​ The Company measures the compensation expense of stock-based awards granted to consultants using the grant date fair value of the award. The Company recognizes compensation expense over the period during which services are rendered by the consultant. ​ The Company classifies stock-based compensation expense in its statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipients’ service payments are classified. ​ The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Historically, the Company estimated expected volatility based on historical volatility of a set of peer companies, which are publicly traded. Starting in 2022, the Company estimated expected volatility based on its stock price's historical volatility, as the Company determined that it had adequate historical data regarding the volatility of its own publicly-traded stock price. The expected term of the Company’s stock options has been determined using the “simplified” method for awards that qualify as “plain vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The Company uses an expected dividend yield of zero based on the fact that the Company has never paid cash dividends and does not expect to pay cash dividends in the future. ​ The fair value of each RSU is measured using the closing price of the Company’s common stock on the date of grant.
Patent Costs	Patent Costs ​ All patent related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.
Income Taxes	Income Taxes ​ The Company accounts for income taxes using 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 recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. ​ The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more likely than not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves and unrecognized tax benefits that are considered appropriate, as well as the related net interest and penalties.
Comprehensive Loss	Comprehensive Loss ​ Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. Comprehensive loss is primarily comprised of net loss and unrealized gains (losses) on marketable securities. ​
Net Loss per Share	Net Loss per Share ​ Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted average number of common shares outstanding during the period, plus the weighted average number of potential shares of common stock from the assumed exercise of stock options and warrants and the assumed vesting of RSUs, if dilutive. Since the Company was in a net loss position, basic and diluted net loss per share was the same for each of the periods presented.
Fair Value Measurements	Fair Value Measurements ​ Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ● Level 1 — Quoted prices in active markets for identical assets or liabilities. ​ ● Level 2 — Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ​ ● Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. ​ The Company’s cash equivalents, marketable securities and contingent consideration are carried at fair value, determined according to the fair value hierarchy described above. The carrying value of the Company’s accounts payable and accrued expenses approximate fair value due to the short-term nature of these liabilities. ​
Concentration of Credit Risk and of Significant Suppliers	Concentration of Credit Risk and of Significant Suppliers ​ Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds all cash, cash equivalents and marketable securities balances at three accredited financial institutions, the majority of which are in amounts that exceed or are not subject to federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. ​ The Company is dependent on third-party manufacturers to supply drug product, including all underlying components, for its research and development activities, including preclinical and clinical testing. These activities could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients or other components.
Segment Reporting	Segment Reporting ​ Operating segments are components of a company for which separate financial information is available and evaluated regularly by the chief operating decision maker in assessing performance and deciding how to allocate resources. The Company has two reportable segments, therapeutics and contract research. The therapeutics segment is focused on identifying and developing innovative therapies to address significant unmet needs for immuno-inflammatory diseases. The contract research segment earns revenue from the provision of laboratory services. The Company does not report balance sheet information by segment since it is not reviewed by the chief operating decision maker, and all of the Company’s tangible assets are held in the United States.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements ​ ​ ​

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value of Financial Assets and Liabilities
Schedule of assets and liabilities measured at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 (In thousands) Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents ​ $ 32,177 ​ $ — ​ $ — ​ $ 32,177 Marketable securities ​ — ​ ​ 141,999 ​ ​ — ​ ​ 141,999 Total assets ​ $ 32,177 ​ $ 141,999 ​ $ — ​ $ 174,176 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration ​ $ — ​ $ — ​ $ 6,200 ​ $ 6,200 Total liabilities ​ $ — ​ $ — ​ $ 6,200 ​ $ 6,200 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 (In thousands) Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents ​ $ 38,516 ​ $ — ​ $ — ​ $ 38,516 Marketable securities ​ — ​ ​ 184,536 ​ ​ — ​ ​ 184,536 Total assets ​ $ 38,516 ​ $ 184,536 ​ $ — ​ $ 223,052 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration ​ $ — ​ $ — ​ $ 33,100 ​ $ 33,100 Total liabilities ​ $ — ​ $ — ​ $ 33,100 ​ $ 33,100
Schedule of the fair value of available for sale marketable securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Book ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Value ​ Gain ​ Loss ​ Value Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities (1) ​ $ 52,362 ​ $ 65 ​ $ (142) ​ $ 52,285 Commercial paper ​ ​ 12,345 ​ ​ 2 ​ ​ (1) ​ ​ 12,346 Asset-backed debt securities (2) ​ ​ 10,953 ​ ​ 42 ​ ​ (30) ​ ​ 10,965 Foreign government agency debt securities (3) ​ ​ 4,698 ​ ​ 43 ​ ​ — ​ ​ 4,741 U.S. government and government agency debt securities (4) ​ ​ 61,750 ​ ​ 8 ​ ​ (96) ​ ​ 61,662 Total marketable securities ​ $ 142,108 ​ $ 160 ​ $ (269) ​ $ 141,999 (1) Included in Corporate debt securities is $28.0 million with maturity dates between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (2) Included in Asset-backed debt securities is $6.2 million with maturity dates between one and three years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (3) Included in Foreign government agency debt securities is $4.7 million with a maturity date between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (4) Included in U.S. government and government agency debt securities is $23.9 million with maturity dates between one and two years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Book ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Value ​ Gain ​ Loss ​ Value Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities (1) ​ $ 40,626 ​ $ — ​ $ (251) ​ $ 40,375 Commercial paper ​ ​ 79,598 ​ ​ — ​ ​ — ​ ​ 79,598 Asset-backed debt securities (2) ​ ​ 14,641 ​ ​ 4 ​ ​ (123) ​ ​ 14,522 U.S. government and government agency debt securities (3) ​ ​ 50,571 ​ ​ — ​ ​ (530) ​ ​ 50,041 Total marketable securities ​ $ 185,436 ​ $ 4 ​ $ (904) ​ $ 184,536 (1) Included in Corporate debt securities is $4.8 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (2) Included in Asset-backed debt securities is $2.4 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (3) Included in U.S. government and government agency debt securities is $5.0 million with maturity dates between one and five years . ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2023
Property and Equipment, Net
Schedule of property and equipment, net	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Computer equipment $ 1,253 $ 1,381 Lab equipment ​ ​ 3,154 ​ ​ 2,010 Furniture and fixtures ​ ​ 558 ​ ​ 620 Leasehold improvements ​ ​ 817 ​ ​ 1,123 Property and equipment, gross ​ 5,782 ​ 5,134 Accumulated depreciation ​ (4,162) ​ (4,035) Property and equipment, net ​ $ 1,620 ​ $ 1,099

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Intangible Assets
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Cost ​ Accumulated Amortization ​ ​ ​ Remaining ​ ​ December 31, ​ ​ December 31, ​ ​ December 31, ​ ​ December 31, (In thousands, except years) ​ Life (years) 2023 2022 2023 2022 Other intangible assets ​ ​ 3.6 ​ $ 751 ​ $ 751 ​ $ 482 ​ $ 407 In-process research and development ​ ​ n/a ​ ​ — ​ ​ 6,629 ​ ​ — ​ ​ — Total intangible assets ​ ​ ​ ​ $ 751 ​ $ 7,380 ​ $ 482 ​ $ 407
Schedule of estimated future amortization expenses	​ ​ ​ ​ ​ ​ ​ ​ Year Ending (In thousands) ​ December 31, 2024 ​ 75 2025 ​ 75 2026 ​ ​ 75 2027 ​ ​ 44 Total ​ $ 269 ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, (In thousands) 2023 2022 Employee compensation expenses ​ $ 3,910 ​ $ 5,295 Research and development expenses ​ ​ 6,661 ​ ​ 2,689 Licensing expenses ​ ​ 5,478 ​ ​ 500 Restructuring expenses (Note 15) ​ ​ 3,112 ​ ​ — Other ​ 285 ​ 217 Total accrued expenses ​ $ 19,446 ​ $ 8,701 ​

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	12 Months Ended
	Dec. 31, 2023
Stock-Based Awards
Assumptions used to determine fair value of stock options granted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2023 ​ ​ 2022 ​ ​ 2021 Risk-free interest rate 3.55 % ​ 2.22 % ​ 0.92 % Expected term (in years) 6.2 ​ ​ 6.2 ​ ​ 6.2 ​ Expected volatility 77.73 % ​ 77.95 % ​ 76.60 % Expected dividend yield 0 % ​ 0 % ​ 0 %
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number ​ Exercise ​ Contractual ​ Intrinsic (In thousands, except share and per share data and years) ​ of Shares ​ Price ​ Term ​ Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ ​ ​ Outstanding as of December 31, 2020 ​ 2,871,498 ​ $ 15.16 6.8 ​ $ 4,890 Granted ​ 1,068,100 ​ 23.44 ​ ​ ​ ​ ​ Exercised ​ (115,548) ​ 12.63 ​ ​ ​ ​ 1,373 Forfeited and cancelled ​ (31,600) ​ 23.26 ​ ​ ​ ​ ​ Outstanding as of December 31, 2021 ​ 3,792,450 ​ $ 17.50 6.8 ​ $ 13,710 Granted ​ 2,548,750 ​ 14.40 ​ ​ ​ ​ ​ Exercised ​ (88,172) ​ 1.78 ​ ​ ​ ​ 1,120 Forfeited and cancelled ​ (1,085,864) ​ 18.44 ​ ​ ​ ​ ​ Outstanding as of December 31, 2022 5,167,164 ​ $ 16.04 7.2 ​ $ 15,288 Granted 2,241,550 ​ ​ 15.62 ​ ​ ​ ​ ​ Exercised ​ (71,092) ​ ​ 1.31 ​ ​ ​ ​ 473 Forfeited and cancelled (918,167) ​ ​ 16.85 ​ ​ ​ ​ ​ Outstanding as of December 31, 2023 6,419,455 ​ $ 15.94 ​ 7.1 ​ $ 14 Options vested and expected to vest as of December 31, 2023 6,419,455 ​ $ 15.94 7.1 ​ $ 14 Options exercisable as of December 31, 2023 2,879,529 ​ $ 16.55 5.1 ​ $ 14 ​
Summary of restricted stock units activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ ​ Grant Date ​ Aggregate ​ ​ Number ​ Fair Value ​ Intrinsic (In thousands, except share and per share data) ​ of Shares ​ Per Share ​ Value Outstanding as of December 31, 2020 ​ 2,244,157 ​ $ 3.83 ​ ​ ​ Granted ​ 664,948 ​ ​ 23.33 ​ ​ ​ Vested ​ (1,340,042) ​ ​ 3.18 ​ $ 31,492 Forfeited and cancelled ​ (72,117) ​ ​ 10.36 ​ ​ ​ Outstanding as of December 31, 2021 ​ 1,496,946 ​ $ 12.75 ​ ​ ​ Granted ​ 936,563 ​ ​ 14.43 ​ ​ ​ Vested ​ (533,212) ​ ​ 11.61 ​ $ 7,943 Forfeited and cancelled ​ (379,567) ​ ​ 13.40 ​ ​ ​ Outstanding as of December 31, 2022 ​ 1,520,730 ​ $ 14.02 ​ ​ ​ Granted ​ 993,662 ​ ​ 15.17 ​ ​ ​ Vested ​ (745,279) ​ ​ 11.72 ​ $ 8,262 Forfeited and cancelled ​ (247,173) ​ ​ 15.15 ​ ​ ​ Outstanding as of December 31, 2023 ​ 1,521,940 ​ $ 15.72 ​ ​ ​
Stock-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, (In thousands) 2023 2022 2021 Cost of revenue $ 1,456 $ 1,151 ​ $ 981 Research and development ​ ​ ​ 6,801 ​ ​ 3,745 ​ ​ 3,866 General and administrative ​ ​ 12,285 ​ 10,143 ​ 9,213 Total stock-based compensation expense ​ ​ $ 20,542 ​ $ 15,039 ​ $ 14,060

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Net Loss per Share
Basic and diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, (In thousands, except for share and per share data) ​ 2023 2022 2021 ​ Numerator: ​ ​ ​ ​ ​ Net loss ​ ​ $ (88,481) ​ $ (86,908) ​ $ (90,865) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares of common stock outstanding, basic and diluted ​ ​ 69,808,855 ​ 65,213,944 ​ 56,730,583 ​ Net loss per share, basic and diluted ​ ​ $ (1.27) ​ $ (1.33) ​ $ (1.60) ​
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 Options to purchase common stock ​ 6,419,455 ​ 5,167,164 3,792,450 ​ Restricted stock unit awards ​ 1,521,940 ​ 1,520,730 ​ 1,496,946 ​ Total potential shares of common stock ​ 7,941,395 ​ 6,687,894 5,289,396 ​ ​

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases
Schedule of lease expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, (In thousands) 2023 2022 2021 Operating lease expense $ 1,092 $ 1,013 $ 1,013
Schedule of supplemental balance sheet information related to operating leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Operating Leases: ​ ​ ​ ​ ​ ​ Gross cost ​ $ 5,094 ​ $ 5,240 Accumulated amortization ​ ​ (1,235) ​ ​ (2,560) Other assets ​ $ 3,859 ​ $ 2,680 ​ ​ ​ ​ ​ ​ ​ Current portion of lease liabilities ​ $ 426 ​ $ 684 Other liabilities ​ ​ 3,074 ​ ​ 1,570 Total operating lease liabilities ​ $ 3,500 ​ $ 2,254
Schedule of supplemental information related to operating and finance leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended (In thousands, except for years and percentages) ​ December 31, Supplemental Cash Flow Lease Information: ​ 2023 ​ 2022 2021 Operating cash flows from operating leases ​ $ 974 ​ $ 846 ​ $ 924 ​ Leased assets obtained in exchange for new operating lease liabilities ​ $ 2,010 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average Remaining Lease Term (in years): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating leases ​ ​ 5.3 ​ ​ 5.2 ​ ​ 5.4 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average Discount Rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating leases ​ ​ 10.2 % ​ 10.1 % ​ 10.1 %
Schedule of future maturities lease liabilities under operating leases	​ ​ ​ ​ ​ (In thousands) ​ ​ Operating Year Ending December 31, Leases 2024 ​ $ 766 2025 ​ ​ 847 2026 ​ ​ 868 2027 ​ ​ 890 2028 ​ ​ 912 Thereafter ​ ​ 316 Total undiscounted lease payments ​ ​ 4,598 Less: unrecognized interest ​ ​ (1,098) Total lease liability ​ $ 3,500

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Taxes
Schedule of loss before income taxes by jurisdiction	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ (In thousands) ​ 2023 ​ 2022 ​ 2021 ​ U.S. operations ​ $ (88,848) ​ $ (86,908) ​ $ (90,865) ​ Foreign operations ​ ​ — ​ ​ — ​ ​ — ​ Loss before income taxes ​ $ (88,848) ​ $ (86,908) ​ $ (90,865) ​
Reconciliation of statutory to effective rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 ​ 2022 2021 Federal statutory income tax rate (21.0) % (21.0) % (21.0) % State taxes, net of federal benefit ​ (1.7) (2.3) (7.7) ​ Impact of state rate changes ​ 17.7 ​ — ​ — ​ Research and development tax credits ​ (5.9) (4.3) (3.0) ​ Excess equity compensation tax benefit, net of officer limitation ​ 0.6 ​ 0.2 ​ (3.9) ​ Revaluation of contingent consideration ​ (6.3) ​ 1.1 ​ 5.6 ​ Non-deductible royalty payments ​ 4.3 ​ — ​ — ​ Change in deferred tax asset valuation allowance ​ 11.7 ​ 26.3 ​ 30.0 ​ Other ​ 0.2 — — ​ Effective income tax rate ​ (0.4) % — % — %
Schedule of deferred tax assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, (In thousands) ​ 2023 ​ 2022 Deferred tax assets: ​ ​ ​ Net operating loss carryforwards ​ $ 119,155 ​ $ 120,554 ​ Capitalized start-up costs ​ ​ 3,812 ​ ​ 5,506 ​ Research and development tax credit carryforwards ​ 20,505 ​ 15,233 ​ Section 174 research and development capitalization ​ ​ 30,984 ​ ​ 19,639 ​ Capitalized research and development expense ​ 2,359 ​ 5,448 ​ Stock‑based compensation expense ​ 18,055 ​ 19,432 ​ Accrued compensation ​ ​ 1,219 ​ ​ 1,146 ​ Lease liabilities ​ ​ 774 ​ ​ 558 ​ Other ​ 407 ​ 534 ​ Total deferred tax assets ​ 197,270 ​ 188,050 ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Property and equipment ​ ​ (187) ​ ​ (137) ​ Intangible asset ​ ​ — ​ ​ (1,576) ​ Right-to-use assets ​ ​ (853) ​ ​ (651) ​ Other ​ (1,106) ​ (1,365) ​ Total deferred tax liabilities ​ (2,146) ​ (3,729) ​ Valuation allowance ​ (195,124) ​ (184,688) ​ Deferred tax liabilities, net ​ $ — ​ $ (367) ​
Changes in deferred tax asset valuation allowance	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, (In thousands) ​ ​ 2023 ​ ​ 2022 ​ ​ 2021 Valuation allowance at beginning of year ​ $ (184,688) $ (161,824) $ (134,559) ​ Decreases recorded as benefit to income tax provision ​ — ​ — ​ — ​ Increases recorded to income tax provision ​ (10,436) ​ (22,864) ​ (27,265) ​ Valuation allowance as of end of year ​ $ (195,124) ​ $ (184,688) ​ $ (161,824) ​

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Information
Summary of results of operations by segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2023 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 28,214 ​ $ 3,035 ​ $ — ​ $ 31,249 Intercompany revenue ​ ​ — ​ ​ 16,543 ​ ​ (16,543) ​ ​ — Cost of revenue ​ ​ — ​ ​ 18,941 ​ ​ (15,537) ​ ​ 3,404 Research and development ​ ​ 97,188 ​ ​ — ​ ​ (1,006) ​ ​ 96,182 General and administrative ​ ​ — ​ ​ 4,561 ​ ​ 26,940 ​ ​ 31,501 Licensing ​ ​ 14,658 ​ ​ — ​ ​ — ​ ​ 14,658 Revaluation of contingent consideration ​ ​ (26,900) ​ ​ — ​ ​ — ​ ​ (26,900) Intangible asset impairment ​ ​ 6,629 ​ ​ — ​ ​ — ​ ​ 6,629 Restructuring expense ​ ​ 2,202 ​ ​ 19 ​ ​ 911 ​ ​ 3,132 Loss from operations ​ $ (65,563) ​ $ (3,943) ​ $ (27,851) ​ $ (97,357) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2022 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 25,356 ​ $ 4,396 ​ $ — ​ $ 29,752 Intercompany revenue ​ ​ — ​ ​ 12,609 ​ ​ (12,609) ​ ​ — Cost of revenue ​ ​ — ​ ​ 15,847 ​ ​ (11,824) ​ ​ 4,023 Research and development ​ ​ 78,599 ​ ​ — ​ ​ (786) ​ ​ 77,813 General and administrative ​ ​ — ​ ​ 3,505 ​ ​ 21,628 ​ ​ 25,133 Licensing ​ ​ 7,937 ​ ​ — ​ ​ — ​ ​ 7,937 Revaluation of contingent consideration ​ ​ 4,700 ​ ​ — ​ ​ — ​ ​ 4,700 Loss from operations ​ $ (65,880) ​ $ (2,347) ​ $ (21,627) ​ $ (89,854) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Contract ​ Corporate ​ Total Year Ended December 31, 2021 ​ Therapeutics ​ Research ​ and Other ​ Company Revenue from external customers ​ $ 932 ​ $ 5,829 ​ $ — ​ $ 6,761 Intercompany revenue ​ ​ — ​ ​ 7,618 ​ ​ (7,618) ​ ​ — Cost of revenue ​ ​ — ​ ​ 11,885 ​ ​ (7,172) ​ ​ 4,713 Research and development ​ ​ 44,259 ​ ​ — ​ ​ (446) ​ ​ 43,813 General and administrative ​ ​ — ​ ​ 3,047 ​ ​ 20,572 ​ ​ 23,619 Revaluation of contingent consideration ​ ​ 24,339 ​ ​ — ​ ​ — ​ ​ 24,339 Loss from operations ​ $ (67,666) ​ $ (1,485) ​ $ (20,572) ​ $ (89,723) ​

Organization and Nature of Bu_2

Organization and Nature of Business (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization and Nature of Business
Cash, cash equivalents and marketable securities	$ 181,900
Accumulated deficit	$ 770,796	$ 682,315

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Discontinued Operations.
Accrued expenses	$ 2.2	$ 2.2
Contingent Consideration
Probability of success assumptions	35%
Minimum
Contingent Consideration
Discount range	7.30%
Maximum
Contingent Consideration
Discount range	8.60%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Property and Equipment (Details)	Dec. 31, 2023
Computer equipment
Summary of Significant Accounting Policies
Depreciation period (in years)	3 years
Laboratory equipment | Minimum
Summary of Significant Accounting Policies
Depreciation period (in years)	3 years
Laboratory equipment | Maximum
Summary of Significant Accounting Policies
Depreciation period (in years)	5 years
Furniture and fixtures
Summary of Significant Accounting Policies
Depreciation period (in years)	5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Disaggregation of Revenue [Line Items]
Intangible asset impairment charge	$ 6,629
In-process research and development
Disaggregation of Revenue [Line Items]
Intangible asset impairment charge	$ 6,600

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Stock-Based Compensation and Concentration of Credit Risk and of Significant Suppliers (Details) - item	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Concentration Risk [Line Items]
Expected dividend yield (as a percent)	0%	0%	0%
Number of financial institutions holding entity funds	3
Service Based Award
Concentration Risk [Line Items]
Share-based Compensation, Service Period	4 years

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Segments (Details)	12 Months Ended
	Dec. 31, 2023 segment
Summary of Significant Accounting Policies
Number of operating segments	2

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets:
Marketable securities	$ 141,999	$ 184,536
Liabilities:
Transfers into or out of Level 3	0	0
Revaluation of contingent consideration	(26,900)	4,700	$ 24,339
Confluence
Liabilities:
Revaluation of contingent consideration	26,900
Recurring
Assets:
Cash equivalents	32,177	38,516
Marketable securities	141,999	184,536
Total assets measured at fair value	174,176	223,052
Liabilities:
Contingent consideration	6,200	33,100
Total liabilities measured at fair value	6,200	33,100
Recurring | Level 1
Assets:
Cash equivalents	32,177	38,516
Total assets measured at fair value	32,177	38,516
Recurring | Level 2
Assets:
Marketable securities	141,999	184,536
Total assets measured at fair value	141,999	184,536
Recurring | Level 3
Liabilities:
Contingent consideration	6,200	33,100
Total liabilities measured at fair value	$ 6,200	$ 33,100

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - By Type of Security (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Marketable securities:
Book Value	$ 142,108	$ 185,436
Gross Unrealized Gain	160	4
Gross Unrealized Loss	(269)	(904)
Fair Value	141,999	184,536
Corporate debt securities
Marketable securities:
Book Value	52,362	40,626
Gross Unrealized Gain	65
Gross Unrealized Loss	(142)	(251)
Fair Value	52,285	40,375
Debt securities, maturity dates between one and five years	$ 28,000	$ 4,800
Corporate debt securities | Minimum
Marketable securities:
Marketable securities maturity period	1 year	1 year
Corporate debt securities | Maximum
Marketable securities:
Marketable securities maturity period	2 years	5 years
Commercial paper
Marketable securities:
Book Value	$ 12,345	$ 79,598
Gross Unrealized Gain	2
Gross Unrealized Loss	(1)
Fair Value	12,346	79,598
Asset-backed securities
Marketable securities:
Book Value	10,953	14,641
Gross Unrealized Gain	42	4
Gross Unrealized Loss	(30)	(123)
Fair Value	10,965	14,522
Debt securities, maturity dates between one and five years	$ 6,200	$ 2,400
Asset-backed securities | Minimum
Marketable securities:
Marketable securities maturity period	1 year	1 year
Asset-backed securities | Maximum
Marketable securities:
Marketable securities maturity period	3 years	5 years
Foreign government agency debt securities
Marketable securities:
Book Value	$ 4,698
Gross Unrealized Gain	43
Fair Value	4,741
Debt securities, maturity dates between one and five years	$ 4,700
Foreign government agency debt securities | Minimum
Marketable securities:
Marketable securities maturity period	1 year
Foreign government agency debt securities | Maximum
Marketable securities:
Marketable securities maturity period	2 years
U.S. government and agency debt securities
Marketable securities:
Book Value	$ 61,750	$ 50,571
Gross Unrealized Gain	8
Gross Unrealized Loss	(96)	(530)
Fair Value	61,662	50,041
Debt securities, maturity dates between one and five years	$ 23,900	$ 5,000
U.S. government and agency debt securities | Minimum
Marketable securities:
Marketable securities maturity period	1 year	1 year
U.S. government and agency debt securities | Maximum
Marketable securities:
Marketable securities maturity period	2 years	5 years

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment, Net
Property and equipment, gross	$ 5,782	$ 5,134
Accumulated depreciation	(4,162)	(4,035)
Property and equipment, net	1,620	1,099
Depreciation expense	800	700	$ 800
Computer equipment
Property and Equipment, Net
Property and equipment, gross	1,253	1,381
Lab equipment
Property and Equipment, Net
Property and equipment, gross	3,154	2,010
Furniture and fixtures
Property and Equipment, Net
Property and equipment, gross	558	620
Leasehold improvements
Property and Equipment, Net
Property and equipment, gross	$ 817	$ 1,123

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Definite-lived intangible assets
Accumulated Amortization	$ 482	$ 407
Intangible assets, net
Gross cost	$ 751	7,380
In-process research and development
Indefinite-lived intangible assets
Gross Cost		6,629
Other intangible assets
Intangible Assets
Remaining Life (years)	3 years 7 months 6 days
Definite-lived intangible assets
Gross Cost	$ 751	751
Accumulated Amortization	$ 482	$ 407

Intangible Assets - Future Amor

Intangible Assets - Future Amortization Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 75	$ 75	$ 75
Future amortization expenses
2024	75
2025	75
2026	75
2027	44
Total	$ 269

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Expenses
Employee compensation expenses	$ 3,910	$ 5,295
Research and development expenses	6,661	2,689
Licensing expenses	5,478	500
Restructuring expenses (Note 15)	3,112
Other	285	217
Total accrued expenses	$ 19,446	$ 8,701

Debt (Details)

Debt (Details) - USD ($) $ in Millions	1 Months Ended
	Jul. 31, 2021	Jan. 31, 2021	Mar. 31, 2020
SVB
Debt
Purchase of common stock warrants		388,119	460,251
Term Loan Facility
Debt
Loan borrowed			$ 11
Term Loan Facility | SVB
Debt
Loan borrowed	$ 11
Loan repaid	$ 11.7

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Vote $ / shares shares	Jun. 01, 2023 shares	May 31, 2023 shares	Dec. 31, 2022 $ / shares shares	Jan. 31, 2021 shares	Mar. 31, 2020 USD ($) $ / shares shares
Class of Stock
Preferred stock, shares authorized (in shares)	10,000,000			10,000,000
Preferred stock, shares outstanding (in shares)	0			0
Common stock, shares authorized	200,000,000	200,000,000	100,000,000	100,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.00001			$ 0.00001
Common stock, shares issued (in shares)	70,894,889			66,688,647
Common stock, shares outstanding (in shares)	70,894,889			66,688,647
Number of votes per share | Vote	1
Dividend declared | $	$ 0
SVB
Class of Stock
Common stock warrants					388,119	460,251
Initial exercise price | $ / shares						$ 0.956
Fair value of warrants | $						$ 400

Stockholders' Equity - Other Of

Stockholders' Equity - Other Offerings and ATM Facility (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Jun. 30, 2021	Jan. 31, 2021
January 2021 Public Offering
Subsidiary, Sale of Stock [Line Items]
Common stock, sold				6,306,271
Common stock, price per share				$ 17.50
Aggregate gross proceeds				$ 110.4
Underwriting discounts and commissions				6.6
Payments of stock offering costs				0.4
Proceeds from common stock				$ 103.3
June 2021 Public Offering
Subsidiary, Sale of Stock [Line Items]
Common stock, sold			8,098,592
Common stock, price per share			$ 17.75
Aggregate gross proceeds			$ 143.8
Underwriting discounts and commissions			8.6
Payments of stock offering costs			0.3
Proceeds from common stock			$ 134.9
At The Market Offering | Silicon Valley Bank Securities LLC and Cantor Fitzgerald & Co.
Subsidiary, Sale of Stock [Line Items]
Common stock, sold	3,400,000	4,800,000
Aggregate gross proceeds	$ 27.5	$ 75
Payments of stock offering costs	$ 0.8	$ 2.3

Stock-Based Awards (Details)

Stock-Based Awards (Details) - shares		12 Months Ended
	Jan. 01, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2015
Stock-based awards
Number of Shares, Granted		2,241,550	2,548,750	1,068,100
Options outstanding		6,419,455	5,167,164	3,792,450	2,871,498
Stock Option Valuation
Risk-free interest rate (as a percent)		3.55%	2.22%	0.92%
Expected term (in years)		6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days
Expected volatility (as a percent)		77.73%	77.95%	76.60%
Expected dividend yield (as a percent)		0%	0%	0%
2017 Inducement Plan
Stock-based awards
Options outstanding		370,600
2015 Equity Incentive Plan
Stock-based awards
Number of shares authorized						1,643,872
Number of shares available for grant		3,703,234
Percentage increase to shares available for grant from common outstanding as of preceding December 31 (as a percent)		4%
Additional shares available	2,835,795
Options outstanding		5,668,063
2015 Equity Incentive Plan | Restricted stock unit awards
Stock-based awards
Number of shares outstanding		1,521,940
2012 Equity Compensation Plan
Stock-based awards
Number of shares available for grant		0
Options outstanding		380,792

Stock-Based Awards - Option Act

Stock-Based Awards - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options, Number of Shares
Number of Shares, beginning balance	5,167,164	3,792,450	2,871,498
Number of Shares, Granted	2,241,550	2,548,750	1,068,100
Number of Shares, Exercised	(71,092)	(88,172)	(115,548)
Number of Shares, Forfeited and cancelled	(918,167)	(1,085,864)	(31,600)
Number of Shares, ending balance	6,419,455	5,167,164	3,792,450	2,871,498
Number of Shares, Options vested and expected to vest	6,419,455
Number of Shares, Options exercisable	2,879,529
Options, Weighted Average Exercise Price
Weighted Average Exercise Price, beginning balance (in dollars per share)	$ 16.04	$ 17.50	$ 15.16
Weighted Average Exercise Price, Granted (in dollars per share)	15.62	14.40	23.44
Weighted Average Exercise Price, Exercised (in dollars per share)	1.31	1.78	12.63
Weighted Average Exercise Price, Forfeited and cancelled (in dollars per share)	16.85	18.44	23.26
Weighted Average Exercise Price, ending balance (in dollars per share)	15.94	$ 16.04	$ 17.50	$ 15.16
Weighted Average Exercise Price, Options vested and expected to vest (in dollars per share)	15.94
Weighted Average Exercise Price, Options exercisable (in dollars per share)	$ 16.55
Options, Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	7 years 1 month 6 days	7 years 2 months 12 days	6 years 9 months 18 days	6 years 9 months 18 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in years)	7 years 1 month 6 days
Weighted Average Remaining Contractual Term, Options exercisable (in years)	5 years 1 month 6 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 14	$ 15,288	$ 13,710	$ 4,890
Aggregate Intrinsic Value, Exercised	473	$ 1,120	$ 1,373
Aggregate Intrinsic Value, Options vested and expected to vest	14
Aggregate Intrinsic Value, Options exercisable	$ 14
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 10.98	$ 9.95	$ 15.67

Stock-Based Awards - RSUs (Deta

Stock-Based Awards - RSUs (Details) - Restricted stock unit awards - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
RSU, Number of Units
Units outstanding, beginning of the year	1,520,730	1,496,946	2,244,157
Granted	993,662	936,563	664,948
Vested	(745,279)	(533,212)	(1,340,042)
Forfeited and cancelled	(247,173)	(379,567)	(72,117)
Units outstanding, end of the year	1,521,940	1,520,730	1,496,946
RSU, Weighted Average Grant Date Fair Value Per Unit
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 14.02	$ 12.75	$ 3.83
Weighted average grant date fair value, granted (in dollars per share)	15.17	14.43	23.33
Weighted average grant date fair value, vested (in dollars per share)	11.72	11.61	3.18
Weighted average grant date fair value, forfeited and cancelled (in dollars per share)	15.15	13.40	10.36
Weighted average grant date fair value, ending balance (in dollars per share)	$ 15.72	$ 14.02	$ 12.75
Aggregate intrinsic value of awards that vested during the period	$ 8,262	$ 7,943	$ 31,492

Stock-Based Awards - Compensati

Stock-Based Awards - Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock-based compensation expense
Stock-based compensation expense	$ 20,542	$ 15,039	$ 14,060
Unrecognized stock-based compensation expense, options	30,000
Unrecognized stock-based compensation expense, RSUs	17,700
Cost of revenue
Stock-based compensation expense
Stock-based compensation expense	1,456	1,151	981
Research and development
Stock-based compensation expense
Stock-based compensation expense	6,801	3,745	3,866
General and administrative
Stock-based compensation expense
Stock-based compensation expense	$ 12,285	$ 10,143	$ 9,213
Options to purchase common stock
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)	2 years 8 months 12 days
Restricted stock unit awards
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)	2 years 7 months 6 days

Net Loss per Share (Details)

Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (88,481)	$ (86,908)	$ (90,865)
Denominator:
Weighted average shares of common stock outstanding, basic	69,808,855	65,213,944	56,730,583
Weighted average shares of common stock outstanding, diluted	69,808,855	65,213,944	56,730,583
Net loss per share, basic	$ (1.27)	$ (1.33)	$ (1.60)
Net loss per share, diluted	$ (1.27)	$ (1.33)	$ (1.60)

Net Loss per Share - Anti-dilut

Net Loss per Share - Anti-dilution (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	7,941,395	6,687,894	5,289,396
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	6,419,455	5,167,164	3,792,450
Restricted stock unit awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	1,521,940	1,520,730	1,496,946

Leases (Details)

Leases (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2020 ft²	Dec. 31, 2023 USD ($) ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	May 31, 2023 ft²	Jan. 31, 2023 ft²	Feb. 28, 2019 ft²
Leases
Area leased, sublease agreement | ft²		33,019			11,564		20,433
Sub-subleased | ft²	8,115
Additional sublease | ft²						6,261
Rent expense		$ 1,100	$ 1,000	$ 1,000
Amortization expense		800	1,000	$ 1,000
Operating Leases:
Accumulated amortization		(482)	(407)
Current portion of lease liabilities		426	684
Other liabilities		$ 3,074	$ 1,570
Financial position		Other liabilities	Other liabilities
Total operating lease liabilities		$ 3,500	$ 2,254
Operating Leases
Operating Leases:
Gross cost		5,094	5,240
Accumulated amortization		(1,235)	(2,560)
Other assets		$ 3,859	$ 2,680

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease Costs
Operating lease expense	$ 1,092	$ 1,013	$ 1,013

Leases - Supplemental Informati

Leases - Supplemental Information Related to Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases
Operating cash flows from operating leases	$ 974	$ 846	$ 924
Leased assets obtained in exchange for new operating lease liabilities	$ 2,010
Weighted-Average Remaining Lease Term (in years):
Operating leases	5 years 3 months 18 days	5 years 2 months 12 days	5 years 4 months 24 days
Weighted-Average Discount Rate:
Operating leases	10.20%	10.10%	10.10%

Leases - Future Maturities of L

Leases - Future Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 766
2025	847
2026	868
2027	890
2028	912
Thereafter	316
Total undiscounted lease payments	4,598
Less: unrecognized interest	(1,098)
Total lease liability	$ 3,500	$ 2,254

Income Taxes - Rate Reconciliat

Income Taxes - Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Federal income tax benefit	$ 0	$ 0	$ 0
State income tax benefit	0	0	0
Loss before income taxes
U.S. operations	(88,848)	(86,908)	(90,865)
Loss before income taxes	$ (88,848)	$ (86,908)	$ (90,865)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	(21.00%)	(21.00%)	(21.00%)
State taxes, net of federal benefit	(1.70%)	(2.30%)	(7.70%)
Impact of state rate changes	(17.70%)
Research and development tax credits	(5.90%)	(4.30%)	(3.00%)
Excess equity compensation tax benefit net of officer limitation	0.60%	0.20%	(3.90%)
Revaluation of contingent consideration	(6.30%)	1.10%	5.60%
Non deductible royalty payments	(4.30%)
Change in deferred tax asset valuation allowance	11.70%	26.30%	30%
Other	(0.20%)
Effective income tax rate	(0.40%)

Income Taxes - Deferred Assets

Income Taxes - Deferred Assets and Liabilities, CFDs (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 119,155	$ 120,554
Capitalized start-up costs	3,812	5,506
Research and development tax credit carryforwards	20,505	15,233
Section 174 research and development capitalization	30,984	19,639
Capitalized research and development expense	2,359	5,448
Stockbased compensation expense	18,055	19,432
Accrued compensation	1,219	1,146
Lease liabilities	774	558
Other	407	534
Total deferred tax assets	197,270	188,050
Deferred tax liabilities:
Property and equipment	(187)	(137)
Intangible asset		(1,576)
Right-to-use assets	(853)	(651)
Other	(1,106)	(1,365)
Total deferred tax liabilities	(2,146)	(3,729)
Valuation allowance	(195,124)	(184,688)	$ (161,824)	$ (134,559)
Deferred tax liabilities, net		$ (367)
Federal
Deferred tax liabilities:
Operating loss carryforwards	464,800
Federal | Research Tax Credit Carryforward [Member]
Deferred tax liabilities:
Tax credit carryforward	20,400
State
Deferred tax liabilities:
Operating loss carryforwards	395,300
State | Research Tax Credit Carryforward [Member]
Deferred tax liabilities:
Tax credit carryforward	$ 100

Income Taxes - Valuation Allowa

Income Taxes - Valuation Allowance and Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Changes in valuation allowance for deferred tax assets
Valuation allowance at beginning of year	$ (184,688)	$ (161,824)	$ (134,559)
Increases recorded to income tax provision	(10,436)	(22,864)	(27,265)
Valuation allowance as of end of year	(195,124)	(184,688)	$ (161,824)
Unrecognized tax benefits	$ 0	$ 0

Agreements Related to Intelle_2

Agreements Related to Intellectual Property (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Oct. 31, 2019	Aug. 31, 2017	Dec. 31, 2023	Dec. 31, 2022	Nov. 30, 2022
Agreements Related to Intellectual Property
Contingent consideration			$ 6,200	$ 33,100
Agreement and Plan of Merger
Agreements Related to Intellectual Property
Term of agreement		10 years
Additional contingent consideration based on milestones, maximum, per Agreement		$ 75,000
License Agreement | Sun Pharmaceutical Industries, Inc
Agreements Related to Intellectual Property
Upfront payment receivable			15,000
License Agreement | Pediatrix Therapeutics, Inc.
Agreements Related to Intellectual Property
Upfront payment receivable					$ 5,000
Patent License Agreement | Eli Lilly and Company
Agreements Related to Intellectual Property
Regulatory and commercial milestones			12,700	$ 17,800
APA
Agreements Related to Intellectual Property
Percentage of Sale of EPI Health Cream	1%
Bad debt expenses			$ 1,300

Retirement Savings Plan (Detail

Retirement Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Savings Plan
Employee earnings subject to employer match (as a percent)	4%
Company contributions	$ 0.7	$ 0.5	$ 0.3

Restructuring Charges (Details)

Restructuring Charges (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023
Restructuring Charges
Restructuring charges		$ 3,132
Research and development
Restructuring Charges
Restructuring charges		2,200
General and administrative
Restructuring Charges
Restructuring charges		900
Cost of revenue
Restructuring Charges
Restructuring charges		$ 19
Minimum
Restructuring Charges
Period for which transition services is provided by noticed employees	1 month
Maximum
Restructuring Charges
Retention periods		60 days
Period for which transition services is provided by noticed employees	13 months

Segment Information (Details)

Segment Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Information
Number of reportable segments | segment	2
Total revenue	$ 31,249	$ 29,752	$ 6,761
Cost of revenue	3,404	4,023	4,713
Research and development	96,182	77,813	43,813
General and administrative	31,501	25,133	23,619
Licensing	14,658	7,937
Revaluation of contingent consideration	(26,900)	4,700	24,339
Intangible asset impairment	6,629
Restructuring expense	3,132
Loss from operations	(97,357)	(89,854)	(89,723)
Dermatology Therapeutics Segment
Segment Information
Total revenue	28,214	25,356	932
Contract Research Segment
Segment Information
Total revenue	3,035	4,396	5,829
Operating Segments | Dermatology Therapeutics Segment
Segment Information
Research and development	97,188	78,599	44,259
Licensing	14,658	7,937
Revaluation of contingent consideration	(26,900)	4,700	24,339
Intangible asset impairment	6,629
Restructuring expense	2,202
Loss from operations	(65,563)	(65,880)	(67,666)
Operating Segments | Contract Research Segment
Segment Information
Total revenue	16,543	12,609	7,618
Cost of revenue	18,941	15,847	11,885
General and administrative	4,561	3,505	3,047
Restructuring expense	19
Loss from operations	(3,943)	(2,347)	(1,485)
Corporate and Other
Segment Information
Total revenue	(16,543)	(12,609)	(7,618)
Cost of revenue	(15,537)	(11,824)	(7,172)
Research and development	(1,006)	(786)	(446)
General and administrative	26,940	21,628	20,572
Restructuring expense	911
Loss from operations	$ (27,851)	$ (21,627)	$ (20,572)

Legal Proceedings (Details)

Legal Proceedings (Details) $ in Millions	Dec. 31, 2021 USD ($)
Consolidated Securities Action
Legal Proceedings
Accrual for estimated financial obligation	$ 2.7

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (88,481)	$ (86,908)	$ (90,865)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false