Aptinyx (APTX) 10-K 30 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 15, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity File Number	001-38535
Entity Registrant Name	APTINYX INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4626057
Entity Address, Address Line One	909 Davis Street
Entity Address, Address Line Two	Suite 600
Entity Address, City or Town	Evanston
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60201
City Area Code	847
Local Phone Number	871-0377
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	APTX
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	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 38
Entity Common Stock, Shares Outstanding		67,715,718
Auditor Name	Deloitte & Touche LLP
Auditor Location	Chicago, Illinois
Auditor Firm ID	34
Entity Central Index Key	0001674365
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 56,205	$ 106,124
Restricted cash	179	197
Prepaid expenses and other current assets	7,646	8,422
Total current assets	64,030	114,743
Other assets	2,622
Property and equipment, net	32	185
Total assets	66,684	114,928
Current liabilities:
Accounts payable	724	622
Accrued expenses and other current liabilities	2,772	5,064
Term loan, current	2,795
Total current liabilities	6,291	5,686
Term loan, non-current	22,108	14,155
Other long-term liabilities		331
Total liabilities	28,399	20,172
Commitments and contingencies (see Note 12)
Stockholders' equity:
Preferred stock, $0.01 par value, 10,000 shares authorized and no shares issued and outstanding as of December 31, 2022 and December 31, 2021
Common stock, $0.01 par value, 150,000 shares authorized as of December 31, 2022 and December 31, 2021, 67,716 issued and outstanding as of December 31, 2022 and December 31, 2021	677	677
Additional paid-in capital	390,344	381,966
Accumulated deficit	(352,736)	(287,887)
Total stockholders' equity	38,285	94,756
Total liabilities and stockholders' equity	$ 66,684	$ 114,928

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2022	Dec. 31, 2021
Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	150,000	150,000
Common stock, shares issued	67,716	67,716
Common stock, shares outstanding	67,716	67,716

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Collaboration revenue		$ 1,000
Type of Revenue [Extensible List]	aptx:CollaborationRevenueMember	aptx:CollaborationRevenueMember
Operating expenses:
Research and development	$ 42,748	$ 55,444
General and administrative	19,819	20,090
Total operating expenses	62,567	75,534
Loss from operations	(62,567)	(74,534)
Other (income) expense, net	(737)	(160)
Interest expense	3,019	512
Net loss and comprehensive loss	$ (64,849)	$ (74,886)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.96)	$ (1.11)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.96)	$ (1.11)
Weighted-average number of common shares outstanding, basic (in shares)	67,716	67,220
Weighted-average number of common shares outstanding, diluted (in shares)	67,716	67,220

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Stockholders' (deficit) equity beginning balance at Dec. 31, 2020	$ 633	$ 358,277	$ (213,001)	$ 145,909
Stockholders' (deficit) equity shares beginning balance at Dec. 31, 2020	63,257
Stockholders' (Deficit) Equity Rollforward
Issuance of warrants in connection with term loan financing		255		255
Issuance of common stock upon vesting of restricted stock	$ 11	(11)
Issuance of common stock upon vesting of restricted stock (in shares)	1,089
Repurchase of shares for tax withholdings	$ (3)	(909)		(912)
Repurchase of shares for tax withholdings (in shares)	(347)
Stock-based compensation		9,719		9,719
Issuance of common stock	$ 36	14,502		14,538
Issuance of common stock (in shares)	3,630
Issuance of common stock upon exercise of stock options		133		133
Issuance of common stock upon exercise of stock options (in shares)	87
Net loss			(74,886)	(74,886)
Stockholders' (deficit) equity ending balance at Dec. 31, 2021	$ 677	381,966	(287,887)	$ 94,756
Stockholders' (deficit) equity shares ending balance at Dec. 31, 2021	67,716			67,716
Stockholders' (Deficit) Equity Rollforward
Issuance of warrants in connection with term loan financing		206		$ 206
Stock-based compensation		8,172		8,172
Net loss			(64,849)	(64,849)
Stockholders' (deficit) equity ending balance at Dec. 31, 2022	$ 677	$ 390,344	$ (352,736)	$ 38,285
Stockholders' (deficit) equity shares ending balance at Dec. 31, 2022	67,716			67,716

Statements of Stockholders' E_2

Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
ATM Offering
Sales commissions and other offering costs	$ 529

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (64,850)	$ (74,886)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	122	526
Change in fair value of derivative liability associated with contingently issuable warrants	(125)	44
Non-cash interest expense related to term loan	757	154
Stock-based compensation expense	8,172	9,719
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,311)	(296)
Accounts receivable		257
Accounts payable	89	(587)
Accrued expenses and other liabilities	(2,538)	1,644
Net cash used in operating activities	(59,684)	(63,425)
Cash flows from investing activities:
Proceeds from sale of property and equipment		121
Net cash provided by investing activities		121
Cash flows from financing activities:
Proceeds from stock options exercised		133
Repurchase of shares for tax withholdings		(912)
Proceeds from issuance of term loan, net of issuance costs paid to lender	10,000	14,638
Payment of debt issuance costs	(22)	(82)
Proceeds from at the market offering, net of sales commission		14,615
Payment of offering costs	(231)	(66)
Net cash provided by financing activities	9,747	28,326
Net decrease in cash, cash equivalents and restricted cash	(49,937)	(34,978)
Cash, cash equivalents and restricted cash, at beginning of period	106,321	141,299
Cash, cash equivalents and restricted cash, at end of period	56,384	106,321
Supplemental disclosure of cash flow information:
Cash paid for interest	2,111	255
Supplemental disclosure of non-cash investing and financing activities:
Debt issuance costs not yet paid		13
Recognition of derivative liability associated with contingently issuable warrants		287
Issuance of warrants in connection with term loan financing	$ 206	$ 255

Organization

Organization	12 Months Ended
	Dec. 31, 2022
Organization
Organization	1. Organization Description of business Aptinyx Inc. (the “Company” or “Aptinyx”) was incorporated in Delaware on June 24, 2015 and maintains its headquarters in Evanston, Illinois. Aptinyx is a clinical-stage biopharmaceutical company focused on the discovery, development, and commercialization of novel, proprietary, synthetic small molecules for the treatment of brain and nervous system disorders. Aptinyx has a platform for discovering proprietary compounds that work through a novel mechanism: modulation of N-methyl-D-aspartate receptors (“NMDAr”), which are vital to normal and effective brain and nervous system functions. This mechanism has applicability across a number of brain and nervous system disorders. Liquidity, capital resources, and going concern On July 1, 2019, the Company entered into a Sales Agreement (the “2019 Sales Agreement”) with Cowen and Company, LLC (“Cowen”) pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $24.0 million under an “at the market” offering program (the “2019 ATM Offering”). The Sales Agreement provides that Cowen will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the 2019 ATM Offering. Between July 1, 2019 and December 31, 2022, the Company sold an aggregate of 5,120,940 shares at a weighted-average price of $3.99 per share for net proceeds of $20.4 million after deducting sales commission and other offering expenses including 3,629,458 shares for net proceeds of $14.5 million during the year ended December 31, 2021. On September 15, 2021, the Company entered into a Loan and Security agreement (the “Loan Agreement”) with K2 HealthVentures LLC (“Lender”). The Loan Agreement provides up to $50.0 million principal in term loans, $15.0 million of which was funded at the time the Company entered into the agreement. See Note 10 for additional details regarding the Loan Agreement. On September 16, 2021, the Company entered into a Sales Agreement (the “2021 Sales Agreement”) with Cowen pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $50.0 million under an “at the market” offering program (the “2021 ATM Offering”) and which supersedes the 2019 Sales Agreement and 2019 ATM Offering. The 2021 Sales Agreement provides that Cowen will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the 2021 ATM Offering. Between September 16, 2021 and December 31, 2022, no shares of common stock have been issued and sold pursuant to the 2021 Sales Agreement. The financial statements are prepared in accordance with generally accepted accounting principles applicable to a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. The Company has incurred operating losses and negative cash flows from operations since inception. As of December 31, 2022, the Company had an accumulated deficit of $352.7 million, cash and cash equivalents of $56.2 million, and total liabilities of $28.4 million. In February 2023, the Company announced results from a Phase 2 clinical study evaluating the effects of NYX-458 in patients with cognitive impairment associated with Parkinson’s disease and dementia with Lewy bodies. Across the overall study population, NYX-458 did not demonstrate clinically meaningful improvements over placebo on the study’s efficacy endpoints. The results do not support further development of NYX-458 by the Company. As a result, the Company also began implementation of a strategic restructuring with the objective of preserving capital. As part of the restructuring, the Company eliminated approximately 60% of its workforce (see Note 18) and has taken other actions, including terminating its ongoing Phase 2b study of NYX-783 in PTSD to analyze the data to date to inform the next steps for the program. The Company is not able to advance its studies or perform meaningful research or development without obtaining additional sources of financing. These conditions and events raise substantial doubt about the Company’s ability to continue as a going concern. ​ In response to these conditions, the Company is currently evaluating strategic alternatives including a merger, reverse merger, other business combination, sales of assets, licensing or other strategic transactions involving the Company. There is no assurance that the Company will be successful in executing such transaction or obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. If the Company is unable to obtain additional funding or enter into strategic alternatives, the Company will be forced to further delay, reduce or eliminate its research and development programs or initiate steps to cease operations. As a result, the Company concluded that management’s plans do not alleviate substantial doubt about the Company’s ability to continue as a going concern. ​ The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty.

Basis of presentation

Basis of presentation	12 Months Ended
	Dec. 31, 2022
Basis of presentation
Basis of Presentation	2. Basis of presentation The accompanying financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (“the JOBS Act”), the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies. Recently adopted accounting pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options and Derivatives and Hedging—Contracts in Entity’s Own Equity : Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ASU 2016-02 Leases (Topic 842). In February 2016, the FASB issued ASU No. 2016-02, Leases ​ The Company adopted this standard on a modified retrospective basis on December 31, 2022 and reflected the adoption as of January 1, 2022 in its annual results for the period ended December 31, 2022. The Company elected the package of practical expedients permitted under the transition guidance, which allows it to carry forward its historical lease classification, its determination regarding whether a contract contains a lease and any initial indirect costs that had existed prior to the adoption of this new standard. The Company also elected not to recognize lease assets and lease liabilities for leases with an initial term of 12 months or less. The Company recognized $0.3 million of operating lease right-of-use assets, $0.3 million in short-term operating lease liabilities on the balance sheet upon adoption of the new standard. The operating lease liabilities were determined based on the present value of the remaining minimum rental payments and the operating lease right-of-use asset was determined based on the value of the lease liabilities, adjusted for deferred rent and tenant allowance balances of $0.1 million, which were previously included in accrued liabilities. The adoption of ASU 2016-02 did not have a material impact on the statements of operations and comprehensive loss or cash flows.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Summary of significant accounting policies	3. Summary of significant accounting policies Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Risk and uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of: future clinical study results, the scope, rate of progress and expense of the Company’s ongoing as well as any additional preclinical studies, clinical studies and other research and development activities, clinical study enrollment rate or design, the manufacturing of the Company’s product candidates, significant and changing government regulation, and the timing and receipt of any regulatory approvals. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. The Company is dependent upon third-party manufacturers to supply product for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and final drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and final drug product. A novel strain of coronavirus (COVID-19) was first identified in December 2019, and subsequently declared a global pandemic by the World Health Organization on March 11, 2020. As a result of the outbreak, many companies have experienced disruptions in their operations and in markets served. On March 27, 2020, the Company suspended patient enrollment for certain ongoing Phase 2 clinical studies, including its NYX-2925 studies in painful diabetic peripheral neuropathy and fibromyalgia and its NYX-458 study in Parkinson’s disease cognitive impairment and dementia with Lewy bodies. The Company re-initiated enrollment in its NYX-2925 study in fibromyalgia in September 2020, in its NYX-2925 study in painful diabetic peripheral neuropathy in January 2021, and in its NYX-458 study in Parkinson’s disease cognitive impairment and dementia with Lewy bodies in March 2021. The Company has initiated some and may take additional temporary precautionary measures intended to help ensure the well-being of its employees and minimize business disruption. The Company considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts on the Company’s results of operations and financial position at December 31, 2022. The full extent of the future impacts of COVID-19 on the Company’s operations is uncertain. Another prolonged outbreak could have a material adverse impact on financial results and business operations of the Company, including the availability of capital, timing and ability of the Company to complete certain clinical studies, and other efforts required to advance the development of its targets. Revenue recognition Revenue is recognized in accordance with revenue recognition accounting guidance, which utilizes five steps to determine whether revenue can be recognized and to what extent: (i) identify the contract with a customer; (ii) identify the performance obligation(s); (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) determine the recognition period. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, Revenue from Contracts with Customers, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Significant judgments exercised by management include the identification of performance obligations, and whether such promised goods or services are considered distinct. The Company evaluates promised goods or services on a contract by contract basis to determine whether each promise represents a good or service that is distinct or has the same pattern of transfer as other promises. A promised good or service is considered distinct if the customer can benefit from the good or service independently of other goods/services either in the contract or that can be obtained elsewhere, without regard to contract exclusivity, and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contact. If the good or service is not considered distinct, the Company combines such promises and accounts for them as a single combined performance obligation. Accounts receivable Accounts receivable that management has the intent and ability to collect are reported in the balance sheets at outstanding amounts, less an allowance for doubtful accounts. During the year ended December 31, 2021, one research collaborator, Allergan plc (“Allergan”) represented 100% of the Company’s revenues (see Note 4). The associated accounts receivable were approximately $0.0 million at December 31, 2021. The Company writes off uncollectible receivables based on specific identification when the likelihood of collection is remote. No allowance was deemed necessary at December 31, 2021. Cash, cash equivalents and restricted cash Cash and cash equivalents consist of cash and, if applicable, highly liquid investments with an original maturity of three months or less when purchased. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Cash and cash equivalents ​ $ 56,205 ​ $ 106,124 ​ Short-term restricted cash and long-term restricted cash ​ 179 ​ 197 ​ Total cash, cash equivalents, and restricted cash shown in the statements of cash flows ​ $ 56,384 ​ $ 106,321 ​ ​ Amounts included in restricted cash represent those amounts required to be held as a security deposit in the form of letters of credit for the Company’s leased office facility and cash collateral held by credit card. Concentrations of credit risk The Company, at times, maintains cash and cash equivalents in accounts with a financial institution in excess of the amount insured by the Federal Deposit Insurance Corporation. The Company monitors the financial stability of this institution regularly and management does not believe there is significant credit risk associated with deposits in excess of federally insured amounts. Fair value of financial instruments ASC 820, Fair Value Measurement ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: ● Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; ● Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and ● Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no Level 3 assets as of December 31, 2022 or 2021. Level 3 liabilities as of December 31, 2022 and 2021 was $0.0 million and $0.3 million. The carrying values reported in the Company’s balance sheets for cash and cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short-term nature of these items. Property and equipment Property and equipment are stated at cost. Maintenance and repairs are charged to expense as incurred. Additions, improvements and replacements are capitalized. Depreciation of property and equipment is provided for by the straight-line method over the estimated useful lives of the related assets. The estimated useful lives of property and equipment are as follows: ​ ​ ​ ​ Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease ​ Construction-in-progress reflects property and equipment yet to be placed in service. 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. If the sum of the estimated future undiscounted cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset group, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset group. The Company has not recorded any impairment losses on long-lived assets for the years ended December 31, 2022 and 2021. Research and development Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, overhead costs, depreciation, contract services and other related costs. Research and development costs are expensed to operations as the related obligation is incurred. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the balance sheet as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. Term loans When the Company issues debt with a conversion feature, it assesses whether the conversion feature meets the requirements to be treated as a derivative, as follows: (a) one or more underlyings, typically the price of the Company’s common stock; (b) one or more notional amounts or payment provisions or both, generally the number of shares upon conversion; (c) no initial net investment, which typically excludes the amount borrowed; and (d) net settlement provisions, which in the case of convertible debt generally means the stock received upon conversion can be readily sold for cash. An embedded equity-linked component that meets the definition of a derivative does not have to be separated from the host instrument if the component qualifies for the scope exception for certain contracts involving an issuer’s own equity. The scope exception applies if the contract is both (a) indexed to its own stock; and (b) classified in stockholders’ equity in its balance sheet. If the conversion feature meets the requirements to be treated as a derivative, the conversion features is bifurcated and separately accounted for under ASC Topic 815. Warrants In accordance with ASC Topic 470-20-25, when the Company issues debt with warrants, the Company treats the warrants as a debt discount, recorded as a contra-liability against the debt, and amortizes the balance over the life of the underlying debt as amortization of debt discount expense in the statements of operations. The offset to the contra-liability is recorded as additional paid-in capital in the Company’s balance sheets if the warrants are not treated as a derivative or as liability warrants. The Company determines the fair value of the warrants at issuance using the Black-Scholes option pricing model. ​ Stock-based compensation The Company has stock-based compensation plans that cover the Company’s directors and employees and are more fully described in Note 13. Stock-based compensation cost is estimated at the grant date based on the fair value of the award, and the cost is recognized as expense ratably over the vesting period. Income taxes The Company accounts for income taxes under the liability method in accordance with ASC 740, Income Taxes. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained upon an examination. Any recognized income tax positions would be measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement would be reflected in the period in which the change in judgment occurs. At December 31, 2022 and 2021, the Company had no liability for income tax associated with uncertain tax positions. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred in 2022 or 2021. Segment data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing therapies to treat disorders of the brain and nervous system. All tangible assets are held in the United States and all revenue is generated in the United States. Comprehensive loss Comprehensive loss is equal to net loss as presented in the accompanying statements of operations. Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company has reported net losses for each period presented.

Research collaboration agreemen

Research collaboration agreement with Allergan	12 Months Ended
	Dec. 31, 2022
Research collaboration agreement with Allergan
Research collaboration agreement with Allergan	4. Research collaboration agreement with Allergan On July 24, 2015, the Company entered into a Research Collaboration Agreement (“RCA”) with Naurex Inc., a subsidiary of Allergan plc (“Allergan”), which became a wholly owned subsidiary of AbbVie Inc. in May 2020. Under the terms of the agreement, the RCA terminated upon the earlier of (i) 180 days after a predetermined anniversary of the effective date of the RCA and (ii) the date on which Allergan exercises the last of

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2022
Fair value measurements
Fair value measurements	5. Fair value measurements Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ 2022 Level 1 Level 2 Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 55,686 ​ $ 55,686 ​ $ — ​ $ — Money market funds, included in restricted cash ​ ​ 179 ​ ​ 179 ​ — ​ — Total Assets ​ $ 55,865 ​ $ 55,865 ​ $ — ​ $ — ​ Assets measured at fair value on a recurring basis as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ 2021 Level 1 Level 2 Level 3 Assets ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 103,859 ​ $ 103,859 ​ $ — ​ $ — Money market funds, included in restricted cash ​ ​ 197 ​ ​ 197 ​ — ​ — Total Assets ​ $ 104,056 ​ $ 104,056 ​ $ — ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative liability, included in other long-term liabilities ​ $ 331 ​ $ — ​ $ — ​ $ 331 Total Liabilities ​ $ 331 ​ $ — ​ $ — ​ $ 331 ​

Prepaid expenses and other curr

Prepaid expenses and other current assets	12 Months Ended
	Dec. 31, 2022
Prepaid expenses and other current assets
Prepaid expenses and other current assets	6. Prepaid expenses and other current assets Prepaid expenses and other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Prepaid clinical $ 3,828 ​ $ 4,693 Prepaid insurance ​ ​ 1,109 ​ ​ 1,122 ​ Prepaid manufacturing costs ​ ​ 2,380 ​ ​ 2,241 ​ Other prepaid expenses and current assets 329 ​ 366 Total prepaid expenses and other current assets $ 7,646 ​ $ 8,422 ​

Property and equipment

Property and equipment	12 Months Ended
	Dec. 31, 2022
Property and equipment
Property and equipment	7. Property and equipment Property and equipment are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2022 2021 Office equipment and furniture ​ 152 ​ 152 ​ Laboratory equipment ​ 401 ​ 401 ​ Leasehold improvements ​ 979 ​ 979 ​ Less accumulated depreciation ​ (1,500) ​ (1,347) ​ Property and equipment, net ​ $ 32 ​ $ 185 ​ ​ Depreciation expense was $0.2 and $0.6 million for the years ended December 31, 2022 and 2021. The Company disposed of certain laboratory equipment during the year ended December 31, 2021 that were fully depreciated at the time of disposal.

Accrued expenses and other curr

Accrued expenses and other current liabilities	12 Months Ended
	Dec. 31, 2022
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	8. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Employee-related expenses ​ $ 1,724 ​ $ 2,567 ​ Development costs and sponsored research ​ 84 ​ 1,347 ​ Clinical trials ​ 184 ​ 810 ​ Other ​ 780 ​ 340 ​ Total accrued expenses and other current liabilities ​ $ 2,772 ​ $ 5,064 ​ ​

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases
Leases	9. Leases On October 13, 2016, the Company entered into a lease agreement with the landlord for office space totaling approximately 16,500 square feet. The term of this lease commenced on April 1, 2017 and continues through August 31, 2022. The Company has an option to renew the lease for one renewal term of 5 years. The lease provided the Company with a tenant improvement allowance of $0.4 million. The Company recorded the tenant improvement allowance incurred as a deferred lease incentive and is amortizing the deferred lease incentive through a reduction of rent expense ratably over the lease term. On July 18, 2018, the Company entered into a sublease agreement for additional office space adjacent to the Company’s existing headquarters in Evanston, Illinois, totaling approximately 6,172 square feet. The term of the lease commenced on July 18, 2018 and continues through September 30, 2022. On January 31, 2019, the sublease agreement was terminated, and the Company entered into an amended lease agreement with the landlord for the same additional office space. The terms commence on February 1, 2019 and continue through August 31, 2022. On April 6, 2022, the Company executed an amendment to extend the lease agreement with its landlord for office space totaling 22,672 square feet through September 30, 2023. The Company determines if an arrangement is a lease at inception. Operating leases are included in other assets and accured expenses and other current liabilities on the balance sheet. Right-of-use assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date. The operating lease right-of-use assets also include any lease payments made and are reduced by any lease incentives received. The Company’s lease terms may include options to extend or not terminate the lease when it is reasonably certain that it will exercise any such options. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Lease expense is recognized on a straight-line basis over the expected lease term. The Company’s only options to renew as of December 31, 2022. The Company has elected the practical expedient permitted under ASC 842 to combine lease and non-lease components. As a result, non-lease components, such as common area maintenance charges, are accounted for as a single lease element. The Company’s remaining operating leases are primarily comprised of leases of printers and other equipment. The Company does not have material finance leases. The Company’s real estate lease agreement includes variable payments that are passed through by the landlord, such as insurance, taxes, and common area maintenance, and payments based on the usage of the asset. Pass-through charges and payments due to changes in usage of the asset are included within variable rent expense. In 2021, the Company entered into an agreement with a contract manufacturing organization for manufacturing of materials for research and development purposes, including manufacturing of clinical trial materials. This agreement is valid for a period of five years , unless terminated earlier by the Company. The Company has determined that the agreement includes an embedded lease. There are no contractual minimum purchase obligations associated with this agreement. All payments associated with this agreement are variable. The Company’s lease agreement does not contain material residual value guarantees, restrictions, or covenants. The components of lease expense were as follows: ​ ​ ​ ​ ​ ​ ​ ​ As of ​ December 31, ​ 2022 Operating lease cost $ 392 Variable lease cost ​ 1,244 Total lease cost $ 1,636 ​ Supplemental cash flow information related to operating leases was as follows: ​ ​ ​ ​ ​ ​ December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities ​ ​ ​ Operating cash flows from operating leases ​ $ 458 Right of use assets obtained in exchange for operating lease obligations (1) ​ ​ ​ Operating leases ​ $ 657 ​ (1) Including the balance recognized on January 1, 2022, upon adoption of ASU No. 2016-02. Supplemental balance sheet information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease right-of-use assets ​ ​ ​ $ 305 ​ ​ ​ ​ ​ ​ Other current liabilities ​ ​ ​ $ 337 Noncurent Operating Lease Liabilities ​ ​ ​ ​ — Total operating lease liabilities ​ ​ ​ ​ 337 ​ ​ ​ ​ ​ ​ Weighted average lease term ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 0.75 years Weighted average discount rate ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 9.5% ​ ​ ​ ​ ​ ​ ​ As of December 31, 2022, the future payments under operating leases were as follows: ​ ​ ​ ​ ​ Year ending December 31, ​ ​ 2023 ​ $ 347 2024 ​ — 2025 ​ — 2026 ​ — 2027 ​ — Thereafter ​ — Total Lease Payments ​ $ 347 Less: Imputed Interest ​ ​ (10) Present Value of Lease Liabilities ​ $ 337 ​ ​ As of December 31, 2022, we have an additional lease, primarily for clinical supply manufacturing, that has not yet commenced with a minimum order commitment of $2.6 million and a minimum lease term of two years Comparative Period Disclosures under ASC 840: Rental expense for operating leases for the year ended December 31, 2021 was $0.8 million. Future minimum rental payments under non-cancellable operating leases (within initial or remaining lease terms in excess of one year) as of December 31, 2021 were: ​ ​ ​ ​ Year ending December 31, ​ ​ 2023 ​ $ 628 2023 ​ — 2024 ​ — 2025 ​ — 2026 ​ — Thereafter ​ — Total Minimum Lease Payments under ASC 840 ​ $ 628 ​

Debt

Debt	12 Months Ended
	Dec. 31, 2022
Debt
Debt	10. Debt On September 15, 2021, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with K2 HealthVentures LLC (the “Lender”). The Lender has agreed to make available to the Company term loans in an aggregate principal amount of up to $50.0 million under the Loan Agreement. The Company plans to use the proceeds of the term loans to support clinical development as well as for working capital and general corporate purposes. The Loan Agreement provides a term loan commitment of $50.0 million in four potential tranches: (i) a $15.0 million term loan facility funded on September 15, 2021 (the “First Tranche Term Loan”), (ii) a $10.0 million term loan facility (the “Second Tranche Term Loan”) available at the Company’s option between January 1, 2022 and June 30, 2022, (iii) a $10.0 million term loan facility (the “Third Tranche Term Loan”) available at the Company’s option between July 1, 2022 and December 1, 2022 subject to the draw of the Second Tranche Term Loan and positive phase 2 clinical data from NYX-2925 or NYX-458 and progression of another clinical asset, and (iv) a $15.0 million term loan facility (the “Fourth Tranche Term Loan”) available through July 1, 2023 at the Company’s option but subject to review of financial and clinical plan and Lender’s Investment Committee approval. All four of these term loans have a maturity date of September 1, 2025. Borrowings under all four term loan facilities bear interest at a floating per annum rate equal to the greater of (i) 7.95% and (ii) the Prime Rate plus 4.70% . The Company is permitted to make interest-only payments on the First Tranche Term Loan for the first 24 months following the funding date. The interest-only period can be extended by an additional 12 months , subject to the funding of the Second Tranche Term Loan and the funding of the Third Tranche Term Loan. The term of the combined facility will be 48 months , with repayment in monthly installments commencing at the end of the resulting interest-only period as outlined above through the end of the 48-month term. The Company is obligated to pay a final fee equal to 6.45% of the aggregate amount of the term loans funded (“Exit Fee”), to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans. The Company has the option to prepay all, but not less than all, of the outstanding principal balance of the term loans under the Loan Agreement. If the Company prepays all of the term loans prior to the maturity date, it will pay the Lender a prepayment penalty fee based on a percentage of the outstanding principal balance, equal to 3% if the payment occurs on or before 24 months after the initial funding date, 2% if the prepayment occurs more than 24 months after, but on or before 36 months after the initial funding date, or 1% if the prepayment occurs more than 36 months after the initial funding date. The Company also is obligated to pay the Lender an origination fee of 0.8% of all term loans funded at the time of funding. The Lender may, at its option, elect to convert any portion of no more than $4.0 million of the then outstanding term loan amount and all accrued and unpaid interest thereon into shares of the Company’s common stock at a conversion price of the lesser of $4.25 per share and the price per share of the common stock in the Company’s next equity offering in which the Company receives at least $20.0 million of gross proceeds . The Company determined that the embedded conversion option is not required to be separated from the term loan. The embedded conversion option meets the derivative accounting scope exception since the embedded conversion option is indexed to the Company’s own common stock and qualifies for classification within stockholders’ equity. The Company’s obligations under the Loan Agreement are secured by a first priority security interest in substantially all of its assets. The Loan Agreement contains customary representations and warranties, and also includes customary events of default, including payment default, breach of covenants, change of control, and material adverse effects. The Loan Agreement restricts certain activities, such as disposing of the Company’s business or certain assets, incurring additional debt or liens or making payments on other debt, making certain investments and declaring dividends, acquiring or merging with another entity, engaging in transactions with affiliates or encumbering intellectual property, among others. There are no financial covenants associated with the Loan Agreement. The Company was in compliance with all non-financial covenants under the Loan Agreement as of December 31, 2022. Upon the occurrence of an event of default, a default interest rate of an addition 5% per annum may be applied to the outstanding loan balances, and the Lender may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Loan Agreement and under applicable law. The Company recorded interest expense related to the Loan Agreement of $3.0 million and $0.5 million for the years ended December 31, 2022 and 2021. Future principal debt payments of the term loans funded as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ 2023 ​ $ 2,795 2024 ​ 12,066 2025 ​ 10,139 2026 ​ — Total principal payments ​ 25,000 Exit Fee ​ ​ 1,613 Total principal payments and Exit Fee ​ ​ 26,613 Less: Unamortized debt discount related to warrants ​ ​ (339) Less: Unamortized debt discount related to Exit Fee ​ ​ (1,078) Less: Unamortized debt issuance costs ​ (293) Term loan, net ​ ​ 24,903 Less: current portion of term loan ​ ​ (2,795) Term loan, non-current ​ $ 22,108

Warrants and derivative liabili

Warrants and derivative liability	12 Months Ended
	Dec. 31, 2022
Warrants and derivative liability
Warrants and derivative liability	11. Warrants and derivative liability ​ ​ ​ Warrants ​ On September 15, 2021, the Company entered into the Loan Agreement with the Lender pursuant to which the Lender may provide the Company with term loans in an aggregate principal amount of up to $50.0 million. On September 15, 2021, in connection with the funding of the First Tranche Term Loan, the Company issued a warrant exercisable for 147,600 shares of the Company’s common stock at an exercise price of $2.29 per share. The warrant is immediately exercisable for 147,600 shares and expires on September 15, 2031. ​ On March 14, 2022, in connection with the funding of the Second Tranche Term Loan, the Company issued a warrant exercisable for 98,399 shares of the Company’s common stock at an exercise price of $2.29 per share. The warrant is immediately exercisable for 98,399 shares and expires on September 15, 2031. ​ No warrants had been exercised as of December 31, 2022. Any shares of the Company’s common stock issued upon exercise of the warrant are permitted to be settled in unregistered shares. The warrant is classified as equity as it meets all the conditions under GAAP for equity classification. The Company has calculated the fair value of the warrant for initial measurement date of funding of the Second Tranche Term loan, and reassesses whether equity classification for the warrant is appropriate upon any changes to the warrants or capital structure, at each balance sheet date. ​ The Company determined that the fair value of the warrants issued in connection with the First Tranche Term Loan and Second Tranche Term Loan was $0.3 million and $0.2 million, respectively. The specific assumptions used to determine the fair value of the warrants at the issue date were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Tranche ​ Second Tranche ​ ​ Term Loan ​ Term Loan ​ ​ ​ ​ ​ ​ ​ Expected volatility 95 % ​ 93 % Expected dividends None ​ ​ None ​ Expected term 5.00 Years ​ ​ 5.00 Years ​ Risk-free rate 0.81 % ​ 2.10 % ​ Derivative Liability ​ The Additional Warrants’ (as defined below) derivative liability will be remeasured each reporting period until settled or extinguished with subsequent changes in fair value recorded through other income (expense), net in the condensed statements of operations. The fair value of the Additional Warrants derivative liability was determined using a Black-Scholes option pricing model based on the same input assumptions above, with an additional assessment required for the probability that the Additional Tranche Term Loans will be funded which would trigger the issuance of the Additional Warrants. ​ The Company is conditionally obligated to issue a fixed number of additional warrants (“Additional Warrants”) in the amount of 344,998 shares upon the funding of the Second, Third and Fourth Tranche Term Loans with the same exercise price and contractual term. ​ As a result of the funding of the Second Tranche Term Loan, the Company issued a warrant exercisable for 98,399 shares of the Company’s common stock at $2.29 per share. Upon issuing the warrants, the Company reclassified the related portion of its Additional Warrants derivative liability into equity. The remaining Additional Warrant Liability that remains outstanding was remeasured as of period end. The ​ ​ The following table provides a reconciliation of the beginning and ending balances for the Company’s Additional Warrants derivative liability recognized in connection with the term loan measured at fair value using significant unobservable inputs (Level 3): ​ ​ ​ ​ ​ ​ ​ Additional ​ ​ Warrants Balance at December 31, 2021 ​ $ 331 Fair value of Additional Warrant Derivative Liability issued during the period ​ — Change in fair value ​ ​ (125) Derecognition ​ (206) Balance at December 31, 2022 ​ $ — ​ The specific assumptions used to determine the fair value of the warrants as of December 31, 2022 and 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ Expected volatility 100 % ​ 95 % Expected dividends None ​ ​ None ​ Expected term 5.00 Years ​ ​ 5.00 Years ​ Risk-free rate 4.06 % ​ 1.26 %

Stockholders' equity

Stockholders' equity	12 Months Ended
	Dec. 31, 2022
Stockholders' equity
Stockholders' equity	12. Stockholders’ equity Preferred Stock The Company is also authorized to issue 10 million shares of undesignated preferred stock, par value $0.01, in one or more series. As of December 31, 2022 and 2021, no shares of preferred stock were issued or outstanding. Common stock As of December 31, 2022 and 2021, the Company had reserved common stock for issuance as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 Stock options issued and outstanding 11,836 10,713 Warrants ​ 246 ​ 148 ​ 12,082 10,861 ​

Stock incentive plan

Stock incentive plan	12 Months Ended
	Dec. 31, 2022
Stock incentive plan
Stock incentive plan	13. Stock incentive plan In October 2015, the Company established a stock option plan (“2015 Plan”) to provide for the issuance of shares of common stock pursuant to stock options, stock appreciation rights, stock purchase rights, restricted stock agreements and long-term performance awards granted to key employees, directors and consultants of the Company. In June 2018, the Company’s stockholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”), which became effective on June 20, 2018. The number of shares available for grant under the Company’s stock option plan were as follows (in thousands): ​ ​ ​ Available for grant as of January 1, 2021 ​ 2,244 Plan amendment 2,530 Grants (4,610) Forfeitures and cancellations 496 Available for grant as of December 31, 2021 660 Plan amendment 2,709 Grants (2,467) Forfeitures and cancellations 1,344 Available for grant as of December 31, 2022 2,246 ​ Stock-based compensation expense Non-cash stock-based compensation expense recognized in the accompanying statements of operations relating to all stock-based awards for the years ended December 31, 2022 and 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Research and development ​ $ 1,421 ​ $ 2,677 General and administrative ​ 6,751 ​ 7,042 Total stock‑based compensation expense ​ $ 8,172 ​ $ 9,719 ​ Restricted stock units In June 2020 and May 2019, the Company issued an aggregate of 205,200 and 1,183,400 restricted stock units, respectively, to employees. The restricted stock units issued in 2020 vest from the date of grant. The Company at any time may accelerate the vesting of the restricted stock units. Such shares are not accounted for as outstanding until they vest. No restricted stock units were issued in 2022. Non-cash restricted stock unit award expense recognized in the accompanying statements of operations was $0.0 million and $0.8 million for the years ended December 31, 2022 and 2021. There were no unvested restricted stock units as of December 31, 2022 and 2021. Stock options During the years ended December 31, 2022 and 2021, the Company granted 2.5 million and 4.6 million stock options, respectively. The options have a ten-year life and generally vest over a period of four years, subject to continuous employment. The weighted-average grant date fair value per share of each option granted during the years ended December 31, 2022 and 2021 was $2.13 and $2.42, respectively. As of December 31, 2022, there was $9.7 million of unrecognized compensation cost related to non-vested stock options which is expected to be recognized over a weighted-average period of 2.47 years. The fair value of each option award is estimated on the date of grant using a Black-Scholes option pricing valuation model that uses various assumptions regarding the: (1) expected volatility, (2) expected life of the option, (3) expected dividend yield, and (4) risk-free interest rate. T he expected volatility for the Company’s options is based on a weighted-average of the historical volatility of share values of publicly traded companies within the biotechnology industry which, beginning in 2021, now includes the historical volatility of the Company’s stock since the Company’s IPO 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 specific assumptions used to determine the fair value of the stock options granted during the years ended December 31, 2022 and 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 2021 ​ ​ ​ Expected volatility 93%-98% ​ 95%-100% Expected dividends None None Expected option life 5.00 - 6.08 Years 5.27 - 6.08 Years Risk-free rate 1.59 – 4.06% 0.48 – 1.29% ​ The table below summarizes activity related to stock options (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ average ​ ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise ​ contractual ​ intrinsic Options ​ Shares ​ price ​ term ​ value Outstanding, January 1, 2021 6,684 ​ $ 6.88 7.96 ​ $ 1,582 Granted 4,610 ​ 3.11 ​ ​ Exercised ​ (87) ​ ​ 1.53 ​ ​ ​ ​ Forfeited and canceled (494) ​ 5.51 ​ ​ Outstanding, December 31, 2021 10,713 ​ $ 5.36 8.07 ​ $ 718 Granted 2,467 ​ 2.79 ​ Exercised ​ — ​ ​ — ​ ​ ​ ​ ​ Forfeited and canceled (1,344) ​ 4.17 ​ Outstanding, December 31, 2022 ​ 11,836 ​ $ 4.96 ​ 7.31 ​ $ — Vested and expected to vest at December 31, 2022 ​ 11,836 ​ $ 4.96 ​ 7.31 ​ $ — Exercisable at December 31, 2022 7,149 ​ $ 6.21 6.45 ​ $ — ​ Employee stock purchase plan On June 5, 2018, the Company's stockholders approved the 2018 Employee Stock Purchase Plan (the "ESPP"), which became effective upon the completion of the Company's initial public offering. A total of 314,697 shares of common stock were initially reserved for issuance under this plan. In addition, the number of shares of common stock that may be issued under the ESPP automatically increase on January 1 of each year through January 1, 2028, by the lesser of (i) 1% of the number of shares of the Company's common stock outstanding on the immediately preceding December 31 and (ii) such lesser number of shares as determined by the administrator of the Company's ESPP.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2022
Net loss per share
Net loss per share	14. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2022 and 2021 (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Numerator: ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders ​ $ (64,849) ​ $ (74,886) Denominator: ​ ​ Weighted-average common shares outstanding—basic and diluted ​ 67,716 ​ 67,220 Net loss per share attributable to common stockholders—basic and diluted ​ $ (0.96) ​ $ (1.11) ​ The following common stock equivalents outstanding as of December 31, 2022 and 2021, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 Stock options issued and outstanding 11,836 10,713 Warrants ​ 246 ​ 148 ​ 12,082 10,861 ​

Employee benefit plan

Employee benefit plan	12 Months Ended
	Dec. 31, 2022
Employee benefit plan
Employee benefit plan	15. Employee benefit plan Effective December 31, 2015, the Company established a defined contribution 401(k) plan (the “401(k) Plan”) for the benefit of its employees. All of the employees of the Company are eligible to participate in the 401(k) Plan which permits employees to make voluntary contributions up to the dollar limit allowed under the Internal Revenue Code. The 401(k) Plan also provides for matching contributions as defined by the Company of up to a combined total of 4% of an employee’s eligible annual compensation. The Company has recorded matching contributions of $0.3 million for each of the years ended December 31, 2022 and 2021, respectively.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2022
Income taxes
Income taxes	16. Income taxes Provision for income taxes There is no provision for income taxes because the Company has historically incurred operating losses and maintains a full valuation allowance against its net deferred tax assets. The reported amount of income tax expense for the years differs from the amount that would result from applying domestic federal statutory tax rates and pretax losses primarily because of changes in valuation allowance. Deferred tax assets and valuation allowance Deferred tax assets reflect the tax effects of net operating losses (“NOLs”) and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The most significant item of deferred tax assets is derived from the Company’s federal NOLs. At December 31, 2022 the Company had a U.S. federal NOL carryforward available to offset future taxable income of $270.5 million. This includes $184.8 million of gross NOLs that are limited under Sec. 382 of the Internal Revenue Code, of which $48.9 million gross NOLs were generated prior to 2018 and will begin to expire in 2035, and the remainder were generated after 2018 and have an indefinite carryforward period. All the gross NOLs that are limited are subject to a substantial annual limitation and $33.3 million will expire based on such limitations. There could also be additional ownership changes in the future which may result in additional limitations on the utilization of NOL carryforwards. As of December 31, 2022, the Company had state NOL carryforwards of $25.7 million which have a 12-year carryforward period and will begin to expire starting in 2027. A reconciliation of the U.S statutory rate to the Company’s effective tax rate is as follows: ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2022 2021 Federal rate 21.0 % 21.0 % State rate 7.5 7.5 ​ Valuation allowance (27.9) (27.4) ​ Other (0.6) (1.1) ​ ​ — % — % ​ The significant components of the Company’s net deferred tax assets are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ December 31, 2022 2021 Deferred tax assets ​ ​ Net operating loss ​ $ 70,127 ​ $ 64,850 Interest expense carryforwards ​ ​ 774 ​ ​ 88 Section 174 R&D ​ ​ 10,972 ​ ​ — Stock‑based compensation ​ ​ 8,235 ​ ​ 6,305 Accrued clinical trials ​ 61 ​ 330 Accrued compensation ​ 491 ​ 724 Accrued expenses and other, net ​ 406 ​ 582 Total deferred tax assets ​ 91,066 ​ 72,879 Less valuation allowance ​ $ (90,979) ​ $ (72,879) Net deferred tax assets ​ 87 ​ — Other ​ ​ (87) ​ ​ — Total deferred tax liabilities ​ ​ (87) ​ ​ — Net deferred taxes ​ $ — ​ $ — ​ The Company files federal and state income tax returns and, in the normal course of business, the Company is subject to examination by these taxing authorities. As of December 31, 2022, the Company’s tax years through December 31, 2021 are subject to examination by the U.S. federal and state taxing authorities with the exception of the December 31, 2018 tax year.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and contingencies
Commitments and contingencies	17. Commitments and contingencies From time to time, the Company is subject to occasional lawsuits, investigations and claims arising out of the normal conduct of business. The Company has no significant pending or threatened litigation as of December 31, 2022. In the normal course of business, the Company enters into contracts that contain a variety of indemnifications with its employees, licensors, suppliers and service providers. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown at December 31, 2022. The Company does not anticipate recognizing any significant losses relating to these arrangements.

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2022
Subsequent events
Subsequent Event	18. Subsequent events Separation of Workforce On February 26, 2023, the Company announced that it was reducing its workforce by approximately 60% of its current headcount with the objective of preserving capital. This workforce reduction will take place primarily during the first quarter of 2023. As a result of these actions, the Company expects to incur personnel-related restructuring charges of approximately $1.4 million in connection with one-time employee termination costs, including severance and other benefits, which are expected to be incurred in the first quarter of 2023.

Basis of presentation (Policies

Basis of presentation (Policies)	12 Months Ended
	Dec. 31, 2022
Basis of presentation
Basis of presentation	The accompanying financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (“the JOBS Act”), the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies.
Recently adopted accounting pronouncement	Recently adopted accounting pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options and Derivatives and Hedging—Contracts in Entity’s Own Equity : Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ASU 2016-02 Leases (Topic 842). In February 2016, the FASB issued ASU No. 2016-02, Leases ​ The Company adopted this standard on a modified retrospective basis on December 31, 2022 and reflected the adoption as of January 1, 2022 in its annual results for the period ended December 31, 2022. The Company elected the package of practical expedients permitted under the transition guidance, which allows it to carry forward its historical lease classification, its determination regarding whether a contract contains a lease and any initial indirect costs that had existed prior to the adoption of this new standard. The Company also elected not to recognize lease assets and lease liabilities for leases with an initial term of 12 months or less. The Company recognized $0.3 million of operating lease right-of-use assets, $0.3 million in short-term operating lease liabilities on the balance sheet upon adoption of the new standard. The operating lease liabilities were determined based on the present value of the remaining minimum rental payments and the operating lease right-of-use asset was determined based on the value of the lease liabilities, adjusted for deferred rent and tenant allowance balances of $0.1 million, which were previously included in accrued liabilities. The adoption of ASU 2016-02 did not have a material impact on the statements of operations and comprehensive loss or cash flows.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Use of estimates	Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.
Risk and uncertainties	Risk and uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of: future clinical study results, the scope, rate of progress and expense of the Company’s ongoing as well as any additional preclinical studies, clinical studies and other research and development activities, clinical study enrollment rate or design, the manufacturing of the Company’s product candidates, significant and changing government regulation, and the timing and receipt of any regulatory approvals. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. The Company is dependent upon third-party manufacturers to supply product for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and final drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and final drug product. A novel strain of coronavirus (COVID-19) was first identified in December 2019, and subsequently declared a global pandemic by the World Health Organization on March 11, 2020. As a result of the outbreak, many companies have experienced disruptions in their operations and in markets served. On March 27, 2020, the Company suspended patient enrollment for certain ongoing Phase 2 clinical studies, including its NYX-2925 studies in painful diabetic peripheral neuropathy and fibromyalgia and its NYX-458 study in Parkinson’s disease cognitive impairment and dementia with Lewy bodies. The Company re-initiated enrollment in its NYX-2925 study in fibromyalgia in September 2020, in its NYX-2925 study in painful diabetic peripheral neuropathy in January 2021, and in its NYX-458 study in Parkinson’s disease cognitive impairment and dementia with Lewy bodies in March 2021. The Company has initiated some and may take additional temporary precautionary measures intended to help ensure the well-being of its employees and minimize business disruption. The Company considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts on the Company’s results of operations and financial position at December 31, 2022. The full extent of the future impacts of COVID-19 on the Company’s operations is uncertain. Another prolonged outbreak could have a material adverse impact on financial results and business operations of the Company, including the availability of capital, timing and ability of the Company to complete certain clinical studies, and other efforts required to advance the development of its targets.
Revenue recognition	Revenue recognition Revenue is recognized in accordance with revenue recognition accounting guidance, which utilizes five steps to determine whether revenue can be recognized and to what extent: (i) identify the contract with a customer; (ii) identify the performance obligation(s); (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) determine the recognition period. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, Revenue from Contracts with Customers, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Significant judgments exercised by management include the identification of performance obligations, and whether such promised goods or services are considered distinct. The Company evaluates promised goods or services on a contract by contract basis to determine whether each promise represents a good or service that is distinct or has the same pattern of transfer as other promises. A promised good or service is considered distinct if the customer can benefit from the good or service independently of other goods/services either in the contract or that can be obtained elsewhere, without regard to contract exclusivity, and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contact. If the good or service is not considered distinct, the Company combines such promises and accounts for them as a single combined performance obligation.
Accounts receivable	Accounts receivable Accounts receivable that management has the intent and ability to collect are reported in the balance sheets at outstanding amounts, less an allowance for doubtful accounts. During the year ended December 31, 2021, one research collaborator, Allergan plc (“Allergan”) represented 100% of the Company’s revenues (see Note 4). The associated accounts receivable were approximately $0.0 million at December 31, 2021. The Company writes off uncollectible receivables based on specific identification when the likelihood of collection is remote. No allowance was deemed necessary at December 31, 2021.
Cash, cash equivalents and restricted cash	Cash, cash equivalents and restricted cash Cash and cash equivalents consist of cash and, if applicable, highly liquid investments with an original maturity of three months or less when purchased. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Cash and cash equivalents ​ $ 56,205 ​ $ 106,124 ​ Short-term restricted cash and long-term restricted cash ​ 179 ​ 197 ​ Total cash, cash equivalents, and restricted cash shown in the statements of cash flows ​ $ 56,384 ​ $ 106,321 ​ ​ Amounts included in restricted cash represent those amounts required to be held as a security deposit in the form of letters of credit for the Company’s leased office facility and cash collateral held by credit card.
Concentrations of credit risk	Concentrations of credit risk The Company, at times, maintains cash and cash equivalents in accounts with a financial institution in excess of the amount insured by the Federal Deposit Insurance Corporation. The Company monitors the financial stability of this institution regularly and management does not believe there is significant credit risk associated with deposits in excess of federally insured amounts.
Fair value of financial instruments	Fair value of financial instruments ASC 820, Fair Value Measurement ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: ● Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; ● Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and ● Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no Level 3 assets as of December 31, 2022 or 2021. Level 3 liabilities as of December 31, 2022 and 2021 was $0.0 million and $0.3 million. The carrying values reported in the Company’s balance sheets for cash and cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short-term nature of these items.
Property and equipment	Property and equipment Property and equipment are stated at cost. Maintenance and repairs are charged to expense as incurred. Additions, improvements and replacements are capitalized. Depreciation of property and equipment is provided for by the straight-line method over the estimated useful lives of the related assets. The estimated useful lives of property and equipment are as follows: ​ ​ ​ ​ Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease ​ Construction-in-progress reflects property and equipment yet to be placed in service.
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. If the sum of the estimated future undiscounted cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset group, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset group. The Company has not recorded any impairment losses on long-lived assets for the years ended December 31, 2022 and 2021.
Research and development	Research and development Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, overhead costs, depreciation, contract services and other related costs. Research and development costs are expensed to operations as the related obligation is incurred. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the balance sheet as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.
Term loans	Term loans When the Company issues debt with a conversion feature, it assesses whether the conversion feature meets the requirements to be treated as a derivative, as follows: (a) one or more underlyings, typically the price of the Company’s common stock; (b) one or more notional amounts or payment provisions or both, generally the number of shares upon conversion; (c) no initial net investment, which typically excludes the amount borrowed; and (d) net settlement provisions, which in the case of convertible debt generally means the stock received upon conversion can be readily sold for cash. An embedded equity-linked component that meets the definition of a derivative does not have to be separated from the host instrument if the component qualifies for the scope exception for certain contracts involving an issuer’s own equity. The scope exception applies if the contract is both (a) indexed to its own stock; and (b) classified in stockholders’ equity in its balance sheet. If the conversion feature meets the requirements to be treated as a derivative, the conversion features is bifurcated and separately accounted for under ASC Topic 815.
Warrants	Warrants In accordance with ASC Topic 470-20-25, when the Company issues debt with warrants, the Company treats the warrants as a debt discount, recorded as a contra-liability against the debt, and amortizes the balance over the life of the underlying debt as amortization of debt discount expense in the statements of operations. The offset to the contra-liability is recorded as additional paid-in capital in the Company’s balance sheets if the warrants are not treated as a derivative or as liability warrants. The Company determines the fair value of the warrants at issuance using the Black-Scholes option pricing model.
Stock-based compensation	Stock-based compensation The Company has stock-based compensation plans that cover the Company’s directors and employees and are more fully described in Note 13. Stock-based compensation cost is estimated at the grant date based on the fair value of the award, and the cost is recognized as expense ratably over the vesting period.
Income taxes	Income taxes The Company accounts for income taxes under the liability method in accordance with ASC 740, Income Taxes. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained upon an examination. Any recognized income tax positions would be measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement would be reflected in the period in which the change in judgment occurs. At December 31, 2022 and 2021, the Company had no liability for income tax associated with uncertain tax positions. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred in 2022 or 2021.
Segment data	Segment data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing therapies to treat disorders of the brain and nervous system. All tangible assets are held in the United States and all revenue is generated in the United States.
Comprehensive loss	Comprehensive loss Comprehensive loss is equal to net loss as presented in the accompanying statements of operations.
Net loss per share	Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company has reported net losses for each period presented.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Schedule of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Cash and cash equivalents ​ $ 56,205 ​ $ 106,124 ​ Short-term restricted cash and long-term restricted cash ​ 179 ​ 197 ​ Total cash, cash equivalents, and restricted cash shown in the statements of cash flows ​ $ 56,384 ​ $ 106,321 ​ ​
Schedule of estimated useful lives of assets	​ ​ ​ ​ Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair value measurements
Schedule of assets measured at fair value	Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ 2022 Level 1 Level 2 Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 55,686 ​ $ 55,686 ​ $ — ​ $ — Money market funds, included in restricted cash ​ ​ 179 ​ ​ 179 ​ — ​ — Total Assets ​ $ 55,865 ​ $ 55,865 ​ $ — ​ $ — ​ Assets measured at fair value on a recurring basis as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ 2021 Level 1 Level 2 Level 3 Assets ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 103,859 ​ $ 103,859 ​ $ — ​ $ — Money market funds, included in restricted cash ​ ​ 197 ​ ​ 197 ​ — ​ — Total Assets ​ $ 104,056 ​ $ 104,056 ​ $ — ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative liability, included in other long-term liabilities ​ $ 331 ​ $ — ​ $ — ​ $ 331 Total Liabilities ​ $ 331 ​ $ — ​ $ — ​ $ 331

Prepaid expenses and other cu_2

Prepaid expenses and other current assets (Tables)	12 Months Ended
	Dec. 31, 2022
Prepaid expenses and other current assets
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Prepaid clinical $ 3,828 ​ $ 4,693 Prepaid insurance ​ ​ 1,109 ​ ​ 1,122 ​ Prepaid manufacturing costs ​ ​ 2,380 ​ ​ 2,241 ​ Other prepaid expenses and current assets 329 ​ 366 Total prepaid expenses and other current assets $ 7,646 ​ $ 8,422

Property and equipment (Tables)

Property and equipment (Tables)	12 Months Ended
	Dec. 31, 2022
Property and equipment
Schedule of property and equipment, net	Property and equipment are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2022 2021 Office equipment and furniture ​ 152 ​ 152 ​ Laboratory equipment ​ 401 ​ 401 ​ Leasehold improvements ​ 979 ​ 979 ​ Less accumulated depreciation ​ (1,500) ​ (1,347) ​ Property and equipment, net ​ $ 32 ​ $ 185 ​ ​

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
	Dec. 31, 2022
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Employee-related expenses ​ $ 1,724 ​ $ 2,567 ​ Development costs and sponsored research ​ 84 ​ 1,347 ​ Clinical trials ​ 184 ​ 810 ​ Other ​ 780 ​ 340 ​ Total accrued expenses and other current liabilities ​ $ 2,772 ​ $ 5,064 ​

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases
Summary of components of lease expense	​ ​ ​ ​ ​ ​ ​ ​ As of ​ December 31, ​ 2022 Operating lease cost $ 392 Variable lease cost ​ 1,244 Total lease cost $ 1,636 ​
Schedule of Supplemental cash flow information related to operating leases	​ ​ ​ ​ ​ ​ December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities ​ ​ ​ Operating cash flows from operating leases ​ $ 458 Right of use assets obtained in exchange for operating lease obligations (1) ​ ​ ​ Operating leases ​ $ 657 ​ (1) Including the balance recognized on January 1, 2022, upon adoption of ASU No. 2016-02.
Schedule of Supplemental balance sheet information related to leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease right-of-use assets ​ ​ ​ $ 305 ​ ​ ​ ​ ​ ​ Other current liabilities ​ ​ ​ $ 337 Noncurent Operating Lease Liabilities ​ ​ ​ ​ — Total operating lease liabilities ​ ​ ​ ​ 337 ​ ​ ​ ​ ​ ​ Weighted average lease term ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 0.75 years Weighted average discount rate ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 9.5% ​ ​ ​ ​ ​ ​ ​
Schedule of future payments under operating leases	​ ​ ​ ​ ​ Year ending December 31, ​ ​ 2023 ​ $ 347 2024 ​ — 2025 ​ — 2026 ​ — 2027 ​ — Thereafter ​ — Total Lease Payments ​ $ 347 Less: Imputed Interest ​ ​ (10) Present Value of Lease Liabilities ​ $ 337 ​
Schedule of aggregate future minimum annual rental commitments under non-cancelable lease agreements	Future minimum rental payments under non-cancellable operating leases (within initial or remaining lease terms in excess of one year) as of December 31, 2021 were: ​ ​ ​ ​ Year ending December 31, ​ ​ 2023 ​ $ 628 2023 ​ — 2024 ​ — 2025 ​ — 2026 ​ — Thereafter ​ — Total Minimum Lease Payments under ASC 840 ​ $ 628

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2022
Debt
Schedule of maturities of long-term debt	Future principal debt payments of the term loans funded as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ 2023 ​ $ 2,795 2024 ​ 12,066 2025 ​ 10,139 2026 ​ — Total principal payments ​ 25,000 Exit Fee ​ ​ 1,613 Total principal payments and Exit Fee ​ ​ 26,613 Less: Unamortized debt discount related to warrants ​ ​ (339) Less: Unamortized debt discount related to Exit Fee ​ ​ (1,078) Less: Unamortized debt issuance costs ​ (293) Term loan, net ​ ​ 24,903 Less: current portion of term loan ​ ​ (2,795) Term loan, non-current ​ $ 22,108

Warrants and derivative liabi_2

Warrants and derivative liability (Tables)	12 Months Ended
	Dec. 31, 2022
Class of Warrant or Right [Line Items]
Schedule of fair value of the warrants or rights	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ Expected volatility 100 % ​ 95 % Expected dividends None ​ ​ None ​ Expected term 5.00 Years ​ ​ 5.00 Years ​ Risk-free rate 4.06 % ​ 1.26 %
Schedule of reconciliation of liabilities with significant unobservable inputs	​ ​ ​ ​ ​ ​ ​ Additional ​ ​ Warrants Balance at December 31, 2021 ​ $ 331 Fair value of Additional Warrant Derivative Liability issued during the period ​ — Change in fair value ​ ​ (125) Derecognition ​ (206) Balance at December 31, 2022 ​ $ — ​
Loan agreement
Class of Warrant or Right [Line Items]
Schedule of fair value of the warrants or rights	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Tranche ​ Second Tranche ​ ​ Term Loan ​ Term Loan ​ ​ ​ ​ ​ ​ ​ Expected volatility 95 % ​ 93 % Expected dividends None ​ ​ None ​ Expected term 5.00 Years ​ ​ 5.00 Years ​ Risk-free rate 0.81 % ​ 2.10 % ​

Stockholders' equity (Tables)

Stockholders' equity (Tables)	12 Months Ended
	Dec. 31, 2022
Stockholders' equity
Schedule of the Company's common stock reserved for issuance, on an as if converted basis,	As of December 31, 2022 and 2021, the Company had reserved common stock for issuance as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 Stock options issued and outstanding 11,836 10,713 Warrants ​ 246 ​ 148 ​ 12,082 10,861

Stock incentive plan (Tables)

Stock incentive plan (Tables)	12 Months Ended
	Dec. 31, 2022
Stock incentive plan
Schedule of available shares for grant under the Company's stock option plan	The number of shares available for grant under the Company’s stock option plan were as follows (in thousands): ​ ​ ​ Available for grant as of January 1, 2021 ​ 2,244 Plan amendment 2,530 Grants (4,610) Forfeitures and cancellations 496 Available for grant as of December 31, 2021 660 Plan amendment 2,709 Grants (2,467) Forfeitures and cancellations 1,344 Available for grant as of December 31, 2022 2,246 ​
Allocation of stock-based compensation expenses	Non-cash stock-based compensation expense recognized in the accompanying statements of operations relating to all stock-based awards for the years ended December 31, 2022 and 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Research and development ​ $ 1,421 ​ $ 2,677 General and administrative ​ 6,751 ​ 7,042 Total stock‑based compensation expense ​ $ 8,172 ​ $ 9,719 ​
Schedule of assumptions used to determine the fair value of the stock options granted	​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 2021 ​ ​ ​ Expected volatility 93%-98% ​ 95%-100% Expected dividends None None Expected option life 5.00 - 6.08 Years 5.27 - 6.08 Years Risk-free rate 1.59 – 4.06% 0.48 – 1.29% ​
Summary of stock option activity	The table below summarizes activity related to stock options (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ average ​ ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise ​ contractual ​ intrinsic Options ​ Shares ​ price ​ term ​ value Outstanding, January 1, 2021 6,684 ​ $ 6.88 7.96 ​ $ 1,582 Granted 4,610 ​ 3.11 ​ ​ Exercised ​ (87) ​ ​ 1.53 ​ ​ ​ ​ Forfeited and canceled (494) ​ 5.51 ​ ​ Outstanding, December 31, 2021 10,713 ​ $ 5.36 8.07 ​ $ 718 Granted 2,467 ​ 2.79 ​ Exercised ​ — ​ ​ — ​ ​ ​ ​ ​ Forfeited and canceled (1,344) ​ 4.17 ​ Outstanding, December 31, 2022 ​ 11,836 ​ $ 4.96 ​ 7.31 ​ $ — Vested and expected to vest at December 31, 2022 ​ 11,836 ​ $ 4.96 ​ 7.31 ​ $ — Exercisable at December 31, 2022 7,149 ​ $ 6.21 6.45 ​ $ — ​

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2022
Net loss per share
Schedule of basic and diluted net loss per share attributable to common stockholders calculation	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2022 and 2021 (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Numerator: ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders ​ $ (64,849) ​ $ (74,886) Denominator: ​ ​ Weighted-average common shares outstanding—basic and diluted ​ 67,716 ​ 67,220 Net loss per share attributable to common stockholders—basic and diluted ​ $ (0.96) ​ $ (1.11) ​
Schedule of anti-dilutive securities excluded from computation of diluted net loss per share	The following common stock equivalents outstanding as of December 31, 2022 and 2021, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 Stock options issued and outstanding 11,836 10,713 Warrants ​ 246 ​ 148 ​ 12,082 10,861

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income taxes
Summary of reconciliation of U.S. statutory rate to the Company's effective tax rate	​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2022 2021 Federal rate 21.0 % 21.0 % State rate 7.5 7.5 ​ Valuation allowance (27.9) (27.4) ​ Other (0.6) (1.1) ​ ​ — % — % ​
Schedule of significant components of the Company's net deferred tax assets	The significant components of the Company’s net deferred tax assets are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ December 31, 2022 2021 Deferred tax assets ​ ​ Net operating loss ​ $ 70,127 ​ $ 64,850 Interest expense carryforwards ​ ​ 774 ​ ​ 88 Section 174 R&D ​ ​ 10,972 ​ ​ — Stock‑based compensation ​ ​ 8,235 ​ ​ 6,305 Accrued clinical trials ​ 61 ​ 330 Accrued compensation ​ 491 ​ 724 Accrued expenses and other, net ​ 406 ​ 582 Total deferred tax assets ​ 91,066 ​ 72,879 Less valuation allowance ​ $ (90,979) ​ $ (72,879) Net deferred tax assets ​ 87 ​ — Other ​ ​ (87) ​ ​ — Total deferred tax liabilities ​ ​ (87) ​ ​ — Net deferred taxes ​ $ — ​ $ — ​

Organization (Details)

Organization (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended	16 Months Ended	42 Months Ended
	Feb. 26, 2023	Sep. 16, 2021	Jul. 01, 2019	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2022	Sep. 15, 2021
Organization
Proceeds from public offering, net of underwriters' discounts				$ 14,615
Accumulated deficit				(287,887)	$ (352,736)	$ (352,736)
Cash and cash equivalents				106,124	56,205	56,205
Total liabilities				$ 20,172	$ 28,399	$ 28,399
Employee Severance | Separation of Workforce | Subsequent events.
Organization
Percentage of eliminating workforce	60%
ATM Offering
Organization
Number of common stock shares newly issued				3,629,458		5,120,940
Public offering price of the shares sold					$ 3.99	$ 3.99
Proceeds from public offering, net of underwriters' discounts				$ 14,500		$ 20,400
Threshold shares agreed to be sold			$ 24,000
Sales commission percentage			3%
2021 ATM Offering
Organization
Number of common stock shares newly issued					0
Threshold shares agreed to be sold		$ 50,000
Sales commission percentage		3%
Loan agreement
Organization
Maximum borrowing capacity							$ 50,000
First Tranche Term Loan
Organization
Maximum borrowing capacity							15,000
Principal amount							$ 15,000

Basis of presentation (Details)

Basis of presentation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Operating lease right-of-use assets	$ 305
Operating lease liabilities	$ 337
ASU 2016-02
Lease, Practical Expedients, Package [true false]	true
Period of Adoption, Adjustment | ASU 2016-02
Operating lease right-of-use assets	$ 300
Operating lease liabilities	300
Deferred rent and tenant allowance balances	$ 100

Summary of significant accoun_4

Summary of significant accounting policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) customer
Concentration Risk [Line Items]
Allowance for accounts receivable	$ 0
Customer Concentration Risk | Revenue | Allergan
Concentration Risk [Line Items]
Number of customers | customer	1
Concentration risk percentage	100%
Customer Concentration Risk | Accounts Receivable | Allergan
Concentration Risk [Line Items]
Accounts receivable	$ 0

Summary of significant accoun_5

Summary of significant accounting policies - Cash, cash equivalents, and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of significant accounting policies
Cash and cash equivalents	$ 56,205	$ 106,124
Restricted cash	179	197
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 56,384	$ 106,321	$ 141,299

Summary of significant accoun_6

Summary of significant accounting policies - Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Impairment of long lived assets	$ 0	$ 0
Computer software and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Level 3
Property, Plant and Equipment [Line Items]
Assets measured at fair value	$ 0	0
Liabilities measured at fair value	$ 0	$ 300

Summary of significant accoun_7

Summary of significant accounting policies - Income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Summary of significant accounting policies
Deferred income tax assets	$ 0
Increase in valuation allowance	18.1	$ 20.6
Uncertain tax positions	0	0
Interest or penalties recorded	$ 0	$ 0

Research collaboration agreem_2

Research collaboration agreement with Allergan (Details) $ in Thousands		12 Months Ended
	Jul. 24, 2015 USD ($) Option	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Research collaboration agreement with Allergan
Research and development		$ 42,748	$ 55,444
RCA
Research collaboration agreement with Allergan
Agreement term	180 days
Number of options to acquire molecules | Option	3
Payment of option exercise fee	$ 1,000
Milestone payment			$ 1,000

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair value measurements
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Noncurrent
Level 3
Fair value measurements
Total Assets	$ 0	$ 0
Recurring
Fair value measurements
Total Assets	55,865	104,056
Derivative liability, included in other long-term liabilities		331
Total Liabilities		331
Recurring | Money market funds, included in cash and cash equivalents
Fair value measurements
Money market funds	55,686	103,859
Recurring | Money market funds, included in restricted cash
Fair value measurements
Money market funds	179	197
Recurring | Level 1
Fair value measurements
Total Assets	55,865	104,056
Recurring | Level 1 | Money market funds, included in cash and cash equivalents
Fair value measurements
Money market funds	55,686	103,859
Recurring | Level 1 | Money market funds, included in restricted cash
Fair value measurements
Money market funds	$ 179	197
Recurring | Level 3
Fair value measurements
Derivative liability, included in other long-term liabilities		331
Total Liabilities		$ 331

Prepaid expenses and other cu_3

Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Prepaid expenses and other current assets
Prepaid clinical	$ 3,828	$ 4,693
Prepaid insurance	1,109	1,122
Prepaid Manufacturing Cost	2,380	2,241
Other prepaid expenses and current assets	329	366
Total prepaid expenses and other current assets	$ 7,646	$ 8,422

Property and equipment (Details

Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property and equipment
Less accumulated depreciation	$ (1,500)	$ (1,347)
Property and equipment, net	32	185
Depreciation	200	600
Office equipment and furniture
Property and equipment
Property and equipment, gross	152	152
Laboratory equipment
Property and equipment
Property and equipment, gross	401	401
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 979	$ 979

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued expenses and other current liabilities
Employee-related expenses	$ 1,724	$ 2,567
Development costs and sponsored research	84	1,347
Clinical trials	184	810
Other	780	340
Total accrued expenses and other current liabilities	$ 2,772	$ 5,064

Leases (Details)

Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Apr. 06, 2022 ft²	Jul. 18, 2018 ft²	Oct. 13, 2016 USD ($) ft² item
Leased space (in square feet) | ft²			22,672	6,172	16,500
Lease renewal options | item					1
Renewal term (in years)					5 years
Lease term		5 years
Deferred lease incentive					$ 0.4
Lessee, Operating Lease, Existence of Option to Extend [true false]	false
Rent expense inclusive of lease incentives		$ 0.8
Lease not yet commenced	$ 2.6
Minimum
Remaining term (in years)	1 year
Lease term	2 years

Leases - Components of lease ex

Leases - Components of lease expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Leases
Operating lease cost	$ 392
Variable lease cost	1,244
Total lease cost	$ 1,636

Leases - Supplemental cash flow

Leases - Supplemental cash flow information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Supplemental cash flow information
Cash paid for amounts included in the measurement of lease liabilities ,Operating cash flows from operating leases	$ 458
Right of use assets obtained in exchange for operating lease obligations , Operating leases	$ 657

Leases - Supplemental balance s

Leases - Supplemental balance sheet information (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Leases
Operating lease right-of-use assets	$ 305
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets, Noncurrent
Other current liabilities	$ 337
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued Liabilities and Other Liabilities, Current
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent
Total operating lease liabilities	$ 337
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent, Accrued Liabilities and Other Liabilities, Current
Weighted average lease term	9 months
Weighted average discount rate	9.50%

Leases - Future minimum payment

Leases - Future minimum payments under operating leases (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Leases
2023	$ 347
Total Lease Payments	347
Less: Imputed Interest	(10)
Total operating lease liabilities	$ 337

Leases - Future minimum rental

Leases - Future minimum rental payments (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Leases
2023	$ 628
Operating Leases, Future Minimum Payments Due	$ 628

Debt (Details)

Debt (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 15, 2021 USD ($) tranche $ / shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of term loan		$ 10,000	$ 14,638
Interest expense		3,019	512
Loan agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000
Number of tranches | tranche	4
Interest rate	7.95%
Term of debt	48 months
Final fee percentage	6.45%
Threshold amount for conversion	$ 4,000
Origination fee	0.80%
Conversion price | $ / shares	$ 4.25
Equity offering proceeds threshold to set debt conversion price	$ 20,000
Additional default interest rate	5%
Interest expense		$ 3,000	$ 500
Loan agreement | Prepayment occurs on or before 24 months after initial funding
Debt Instrument [Line Items]
Prepayment penalty percentage	3%
Threshold period in which prepayment occurs	24 months
Loan agreement | Prepayment occurs more than 24 months and on or before 36 months after initial funding
Debt Instrument [Line Items]
Prepayment penalty percentage	2%
Loan agreement | Prepayment occurs more than 24 months and on or before 36 months after initial funding | Minimum
Debt Instrument [Line Items]
Threshold period in which prepayment occurs	24 months
Loan agreement | Prepayment occurs more than 24 months and on or before 36 months after initial funding | Maximum
Debt Instrument [Line Items]
Threshold period in which prepayment occurs	36 months
Loan agreement | Prepayment occurs more than 36 months after initial funding
Debt Instrument [Line Items]
Prepayment penalty percentage	1%
Threshold period in which prepayment occurs	36 months
Loan agreement | Prime
Debt Instrument [Line Items]
Spread (as a percent)	4.70%
First Tranche Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000
Principal amount	$ 15,000
Period for which interest only payment is permitted	24 months
Additional period for which interest only payment can be extended	12 months
Second Tranche Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 10,000
Third Tranche Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	10,000
Third Tranche Term Loan For 15 Million [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000

Debt - Future Principal Debt Pa

Debt - Future Principal Debt Payments on The Loan Payable (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Future Principal Debt Payments
2023	$ 2,795
2024	12,066
2025	10,139
Total principal payments	25,000
Exit Fee	1,613
Total principal payments and Exit Fee	26,613
Less: Unamortized debt discount related to warrants	(339)
Less: Unamortized debt discount related to Exit Fee	(1,078)
Less: Unamortized debt issuance costs	(293)
Term loan, net	24,903
Less: current portion of term loan	(2,795)
Term loan, non-current	$ 22,108	$ 14,155

Warrants and derivative liabi_3

Warrants and derivative liability (Details)		12 Months Ended
	Sep. 15, 2021 USD ($) Y $ / shares shares	Dec. 31, 2022 USD ($) shares	Mar. 14, 2022 $ / shares shares	Dec. 31, 2021 Y
Class of Warrant or Right [Line Items]
Warrants exercised | shares		0
Expected volatility
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input		1		0.95
Expected dividends
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input		0		0
Expected term
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	5	5		5
Risk-free rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input		0.0406		0.0126
Loan agreement
Class of Warrant or Right [Line Items]
Maximum borrowing capacity	$ 50,000,000
First Tranche Term Loan
Class of Warrant or Right [Line Items]
Maximum borrowing capacity	$ 15,000,000
Issued warrant exercisable | shares	147,600
Exercise price | $ / shares	$ 2.29
Derivative liability, included in other long-term liabilities	$ 300,000
First Tranche Term Loan | Expected volatility
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0.95
First Tranche Term Loan | Expected dividends
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0
First Tranche Term Loan | Risk-free rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0.0081
Second Tranche Term Loan
Class of Warrant or Right [Line Items]
Maximum borrowing capacity	$ 10,000,000
Issued warrant exercisable | shares			98,399
Exercise price | $ / shares			$ 2.29
Derivative liability, included in other long-term liabilities	$ 200,000
Second Tranche Term Loan | Expected volatility
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0.93
Second Tranche Term Loan | Expected dividends
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0
Second Tranche Term Loan | Expected term
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input | Y	5
Second Tranche Term Loan | Risk-free rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input	0.0210
Additional Warrants
Class of Warrant or Right [Line Items]
Change in fair value of warrants		$ 100,000
Warrants obligated to be issued upon the funding of the second, third and fourth tranche term loans	344,998

Warrants and derivative liabi_4

Warrants and derivative liability - Reconciliation of company's additional warrants (Details) - Additional Warrants $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Reconciliation of company's additional warrants derivative liability
Balance at beginning of period	$ 331
Change in fair value	(125)
Derecognition	$ (206)

Stockholders' equity - Common s

Stockholders' equity - Common stock (Details) - $ / shares shares in Thousands	Dec. 31, 2022	Dec. 31, 2021
Preferred stock, shares authorized	10,000	10,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock reserved for issuance	12,082	10,861
Warrants
Common stock reserved for issuance	246	148
Stock options
Common stock reserved for issuance	11,836	10,713

Stock incentive plan - Shares a

Stock incentive plan - Shares available for grant (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock incentive plan
Available for grant Beginning of the period	660	2,244
Plan amendment	2,709	2,530
Grants	(2,467)	(4,610)
Forfeitures and cancellations	1,344	496
Available for grant End of the period	2,246	660

Stock incentive plan - Stock-ba

Stock incentive plan - Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,172	$ 9,719
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,421	2,677
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,751	$ 7,042

Stock incentive plan - Restrict

Stock incentive plan - Restricted stock units (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2020	May 31, 2019	Dec. 31, 2022	Dec. 31, 2021
Shares
Non-cash restricted stock unit award expense recognized			$ 8,172	$ 9,719
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	10 months	2 years
Shares
Unvested at beginning of period (in shares)			0
Issued (in shares)	205,200	1,183,400	0
Unvested at end of period (in shares)			0	0
Non-cash restricted stock unit award expense recognized			$ 0	$ 800

Stock incentive plan - Fair val

Stock incentive plan - Fair value assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	93%	95%
Expected volatility, maximum	98%	100%
Expected dividends	0%	0%
Riskfree rate, minimum	1.59%	0.48%
Riskfree rate, maximum	4.06%	1.29%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life	5 years	5 years 3 months 7 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life	6 years 29 days	6 years 29 days

Stock incentive plan - Activity

Stock incentive plan - Activity related to stock options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Shares
Granted	2,467	4,610
Forfeited and canceled	(1,344)	(496)
Stock options
Shares
Outstanding, at the beginning of the period	10,713	6,684
Granted	2,467	4,610
Exercised		(87)
Forfeited and canceled	(1,344)	(494)
Outstanding, at the end of the period	11,836	10,713	6,684
Vested and expected to vest	11,836
Exercisable	7,149
Weighted-average exercise price
Outstanding, at the beginning of the period	$ 5.36	$ 6.88
Granted	2.79	3.11
Exercised		1.53
Forfeited and canceled	4.17	5.51
Outstanding, at the end of the period	4.96	$ 5.36	$ 6.88
Vested and expected to vest	4.96
Exercisable at the end of the period	$ 6.21
Weighted-average remaining contractual term
Weighted-average remaining contractual term	7 years 3 months 21 days	8 years 25 days	7 years 11 months 15 days
Vested and expected to vest	7 years 3 months 21 days
Exercisable	6 years 5 months 12 days
Aggregate intrinsic value
Outstanding, at the beginning of the period	$ 718	$ 1,582
Outstanding, at the end of the period		$ 718	$ 1,582
Weighted-average grant date fair value per share	$ 2.13	$ 2.42
Unrecognized stock-based compensation related to non-vested stock options	$ 9,700
Expenses recognized over a weighted-average period (in years)	2 years 5 months 19 days
Term of award	10 years
Vesting period	4 years

Stock incentive plan - Employee

Stock incentive plan - Employee Stock Purchase Plan (Details) - shares	Jun. 05, 2018	Dec. 31, 2022	Dec. 31, 2021
Subsidiary, Sale of Stock [Line Items]
Common stock reserved for issuance		12,082,000	10,861,000
Employee Stock Purchase Plan
Subsidiary, Sale of Stock [Line Items]
Common stock reserved for issuance	314,697
Maximum percentage increase in shares available for issuance under the ESPP	1%

Net loss per share (Details)

Net loss per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss attributable to common stockholders	$ (64,849)	$ (74,886)
Denominator:
Weighted-average number of common shares outstanding, basic (in shares)	67,716	67,220
Weighted-average number of common shares outstanding, diluted (in shares)	67,716	67,220
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.96)	$ (1.11)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.96)	$ (1.11)

Net loss per share - Anti-dilut

Net loss per share - Anti-dilutive securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	12,082	10,861
Stock options
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	11,836	10,713
Warrants
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	246	148

Employee benefit plan (Details)

Employee benefit plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Employee benefit plan
Matching contribution as a percentage	4%
Matching contributions	$ 0.3	$ 0.3

Income taxes (Details)

Income taxes (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Income taxes
Income taxes	$ 0

Income taxes - Deferred tax ass

Income taxes - Deferred tax assets and valuation allowance (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards that expire	$ 33.3
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	270.5
NOL Gross	184.8
Federal | Tax Years Prior to 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	48.9
State
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 25.7
NOL carryforward period	12 years

Income taxes - Reconciliation (

Income taxes - Reconciliation (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income taxes
Federal rate	21%	21%
State rate	7.50%	7.50%
Valuation allowance	(27.90%)	(27.40%)
Other	(0.60%)	(1.10%)

Income taxes - Components of ne

Income taxes - Components of net deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets
Net operating loss	$ 70,127	$ 64,850
Interest expense carryforwards	774	88
Section 174 R&D	10,972
Stock-based compensation	8,235	6,305
Accrued clinical trials	61	330
Accrued compensation	491	724
Accrued expenses and other, net	406	582
Total deferred tax assets	91,066	72,879
Less valuation allowance	(90,979)	$ (72,879)
Net deferred tax assets	87
Other	(87)
Total deferred tax liabilities	(87)
Net deferred taxes	$ 0

Subsequent events (Details)

Subsequent events (Details) - Subsequent events. - Separation of Workforce - USD ($) $ in Millions		3 Months Ended
	Feb. 26, 2023	Mar. 31, 2023
Subsequent Event [Line Items]
Restructuring Charges		$ 1.4
Employee Severance
Subsequent Event [Line Items]
Percentage of reduction in workforce	60%