Marinus Pharmaceuticals (MRNS) 10-K 24 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Mar. 18, 2022	Jun. 30, 2021
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Entity File Number	001-36576
Entity Registrant Name	Marinus Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0198082
Entity Address, Address Line One	5 Radnor Corporate Center, Suite 500
Entity Address, Address Line Two	100 Matsonford Road
Entity Address, City or Town	Radnor
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19087
City Area Code	484
Local Phone Number	801-4670
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	MRNS
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	false
Entity Shell Company	false
Entity Public Float			$ 451,604,966
Entity Common Stock, Shares Outstanding		37,003,419
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Philadelphia, Pennsylvania
Entity Central Index Key	0001267813
Current Fiscal Year End Date	--12-31
ICFR Auditor Attestation Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 122,927	$ 138,509
Short-term investments		1,474
Accounts receivable	2,629	1,646
Contract asset	557
Prepaid expenses and other current assets	5,565	4,638
Total current assets	131,678	146,267
Property and equipment, net	2,499	1,945
Other assets	2,663	2,250
Total assets	136,840	150,462
Current liabilities:
Accounts payable	3,126	2,211
Refund liability	21,233
Accrued expenses	16,207	8,518
Total current liabilities	40,566	10,729
Notes payable, net of deferred financing costs	40,809
Other long-term liabilities	1,979	2,534
Total liabilities	83,354	13,263
Stockholders' equity:
Series A convertible preferred stock, $0.001 par value; 25,000,000 shares authorized, 4,575 shares issued and outstanding at December 31, 2021 and 4,753 issued and outstanding at December 31, 2020	4,302	4,469
Common stock, $0.001 par value; 150,000,000 shares authorized, 36,797,561 issued and 36,790,254 outstanding at December 31, 2021 and 36,585,767 issued and 36,578,460 outstanding at December 31, 2020	37	37
Additional paid-in capital	459,852	444,622
Treasury stock at cost, 7,307 shares at December 31, 2021 and December 31, 2020
Accumulated deficit	(410,705)	(311,929)
Total stockholders' equity	53,486	137,199
Total liabilities and stockholders' equity	$ 136,840	$ 150,462

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	36,797,561	36,585,767
Common stock, shares outstanding	36,790,254	36,578,460
Treasury stock, shares	7,307	7,307
Series A Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred Stock, Shares Issued	4,575	4,753
Preferred stock, shares outstanding	4,575	4,753

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Federal contract revenue	$ 6,358	$ 1,718
Collaboration revenue	8,987
Total revenue	15,345	1,718
Expenses:
Research and development	73,520	51,106
General and administrative	37,278	18,549
Cost of collaboration revenue	1,478
Total expenses	112,276	69,655
Loss from operations	(96,931)	(67,937)
Interest income	80	499
Interest expense	(2,582)
Other income (expense), net	657	(37)
Net loss and comprehensive loss	(98,776)	(67,475)
Deemed Dividends		(8,880)
Net loss applicable to common shareholders	$ (98,776)	$ (76,355)
Per share information:
Net loss per share of common stock-basic	$ (2.69)	$ (2.80)
Net loss per share of common stock-diluted	$ (2.69)	$ (2.80)
Basic weighted average shares outstanding	36,697,171	27,270,055
Diluted weighted average shares outstanding	36,663,340	27,270,055

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Follow-on Public Offering, OneCommon Stock	Follow-on Public Offering, OneAdditional Paid-in Capital	Follow-on Public Offering, One	Follow-on Public Offering, TwoCommon Stock	Follow-on Public Offering, TwoAdditional Paid-in Capital	Follow-on Public Offering, Two	Series A Preferred StockPreferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit	Total
Balance at Dec. 31, 2019								$ 22	$ 295,121		$ (235,574)	$ 59,569
Balance (in shares) at Dec. 31, 2019								21,617,781		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense									7,642			7,642
Exercise of stock options									1,020			1,020
Exercise of stock options (in shares)								198,475
Issuance of restricted stock (in shares)								33,997
Deemed dividend on beneficial conversion feature - Series A convertible preferred stock									8,880		(8,880)
Issuance of common stock	$ 5	$ 42,956	$ 42,961	$ 5	$ 64,787	$ 64,792
Issuance of common stock (in shares)	4,600,000			5,000,000
Issuance of common stock under equity distribution agreement									489			489
Issuance of common stock under equity distribution agreement (in shares)								78,807
Transfer of convertible preferred stock into permanent equity							$ 8,745					8,745
Transfer of convertible preferred stock into permanent equity (in shares)							9,303
Conversion of convertible preferred stock to common stock							$ (4,276)	$ 5	23,727			19,456
Conversion of convertible preferred stock to common stock (in shares)							(4,550)	5,049,400
Net loss											(67,475)	(67,475)
Balance at Dec. 31, 2020							$ 4,469	$ 37	444,622		(311,929)	137,199
Balance (in shares) at Dec. 31, 2020							4,753	36,578,460		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense									13,867			13,867
Exercise of stock options									1,199			1,199
Exercise of stock options (in shares)								176,194
Financing costs									(3)			(3)
Conversion of convertible preferred stock to common stock							$ (167)		167
Conversion of convertible preferred stock to common stock (in shares)							(178)	35,600
Net loss											(98,776)	(98,776)
Balance at Dec. 31, 2021							$ 4,302	$ 37	$ 459,852		$ (410,705)	$ 53,486
Balance (in shares) at Dec. 31, 2021							4,575	36,790,254		7,307

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / shares
Follow-on Public Offering, One
Share Price (in dollars per share) | $ / shares	$ 10
Stock issuance costs	$ 3,025
Follow-on Public Offering, Two
Share Price (in dollars per share) | $ / shares	$ 14
Stock issuance costs	$ 5,208
2017 Equity Distribution Agreement
Stock issuance costs	$ 161

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (98,776)	$ (67,475)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	355	334
Amortization of debt issuance costs	549
Stock-based compensation expense	13,867	7,642
Noncash contract asset	(105)
Noncash lease expense	312	264
Noncash lease liability	309	362
Loss on fixed assets held for sale	243
Unrealized gain on foreign currency transactions	(930)
Amortization of discount on investments		3
Changes in operating assets and liabilities:
Refund Liability	22,163
Contract asset	(452)
Prepaid expenses and other current assets, non-current assets, and accounts receivable	(853)	(3,919)
Accounts payable, accrued expenses and other long term-liabilities	7,841	1,877
Net cash used in operating activities	(55,477)	(60,912)
Cash flows from investing activities
Maturities of short-term investments	1,474	8,193
Purchases of short-term investments		(8,931)
Deposit on property and equipment	(1,793)
Purchases of property and equipment	(1,096)
Net cash used in investing activities	(1,415)	(738)
Cash flows from financing activities
Proceeds from exercise of stock options	1,199	1,020
Proceeds from notes payable, net of issuance costs	40,259
Financing costs, paid	(148)
Proceeds from equity offerings, net of offering costs		108,196
Net cash provided by financing activities	41,310	109,216
Net (decrease) increase in cash and cash equivalents	(15,582)	47,566
Cash and cash equivalents-beginning of period	138,509	90,943
Cash and cash equivalents-end of period	122,927	138,509
Supplemental disclosure of cash flow information
Contractual exit fee included in notes payable	900
Property and equipment in accrued expenses	$ 43
Financing in accounts payable and accrued expenses		$ 148

Organization and Description of

Organization and Description of the Business	12 Months Ended
	Dec. 31, 2021
Organization and Description of the Business
Organization and Description of the Business	1. Organization and Description of the Business We are a pharmaceutical company focused on the development and commercialization of products for patients suffering from rare genetic epilepsies and other seizure disorders. On March 18, 2022, the U.S Food and Drug Administration (FDA) approved our new drug application (NDA) for the use of ZTALMY® (ganaxolone) oral suspension for the treatment of seizures associated with cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) in patients 2 years of age and older. ​ The continued global spread of COVID-19, including the Omicron variant, has impacted our clinical operations and timelines. For example, our Phase 3 Randomized Therapy In Status Epilepticus (SE) Trial (RAISE trial) in refractory status epilepticus (RSE) is conducted in hospitals, including intensive care units and academic medical centers, which have experienced high rates of COVID-19 admissions. Several academic medical centers and intensive care units participating in the RAISE trial have experienced COVID-related difficulties, including staff turnover and the need to devote significant resources to patients with COVID-19, which has resulted in site initiation and enrollment delays for the RAISE trial. Given these COVID-19-related challenges and a temporary pause beginning in February 2022 of the RAISE trial after routine monitoring of stability batches of clinical supply material indicated that it became necessary to reduce the shelf life to less than the anticipated 24-months to meet product stability testing specifications, we now expect our top-line data readout for the RAISE trial to be available in the second half of 2023. In addition, our ganaxolone clinical trials in the outpatient setting may be negatively impacted if patients and their caregivers do not want to participate while the COVID-19 pandemic persists. The duration and severity of the pandemic and its long-term impact on our business are uncertain at this time. Liquidity We have not generated any product revenues and have incurred operating losses since inception, including losses of $98.8 million for the year ended December 31, 2021. There is no assurance that profitable operations will ever be achieved, and if achieved, could be sustained on a continuing basis. In addition, development activities, clinical and preclinical testing, and commercialization of ganaxolone will require significant additional financing. Our accumulated deficit as of December 31, 2021 was $410.7 million and we expect to incur substantial losses in future periods. We plan to finance our future operations with a combination of proceeds from the issuance of equity securities, the issuance of debt, government funding, collaborations, licensing transactions and other commercial transactions or other sources, such as our Priority Review Voucher, and revenues from future product sales, if any. We have not generated positive cash flows from operations, and there are no assurances that we will be successful in obtaining an adequate level of financing for the development and commercialization of ganaxolone. On July 30, 2021, we entered into a collaboration agreement (Orion Collaboration Agreement) with Orion Corporation (Orion), whereby Orion received exclusive rights to commercialize the oral and IV dose formulations of ganaxolone in the European Economic Area, United Kingdom and Switzerland in multiple seizure disorders, including CDD, tuberous sclerosis complex (TSC) and RSE. Under the agreement, we received a ninety or effect. In February 2022, the verified draft study report showed that no genotoxicity was found, as measured by formation of micronuclei in the bone marrow or comet morphology in the liver. As such, but subject to confirmation of such results in the final study report expected by the end of the second quarter of 2022, and subsequent to the date of these financial statements, we will not be required to refund Orion any of the upfront fee and Orion will not have a right to terminate the Orion Collaboration Agreement as a result of the study’s findings. On May 11, 2021 (Closing Date), we entered into a Credit Agreement and Guaranty (as amended by that certain letter agreement on May 17, 2021, the Credit Agreement) with Oaktree Fund Administration, LLC, as administrative agent and the lenders party thereto that provides for a five-year senior secured term loan facility in an aggregate original principal amount of up to $125.0 million available to us in five tranches (collectively, the Term Loans). Refer to Note 9. Notes Payable for additional information. In September 2020, we entered into a contract (BARDA Contract) with the Biomedical Advanced Research and Development Authority (BARDA), a division of the U.S. Department of Health and Human Services’ Office of the Assistant Secretary for Preparedness and Response. Under the BARDA Contract, we receive d an award of up to an estimated $51 million for development of IV-administered ganaxolone for the treatment of RSE. The BARDA Contract provides for f unding to support , on a cost-sharing basis , the completion of a Phase 3 clinical trial of IV-administered ganaxolone in patients with RSE , which covers the RAISE trial , funding of pre-clinical studies to evaluate IV-administered ganaxolone a s an effective treatment for RSE due to chemical nerve gas agent exposure, and funding of certain ganaxolone manufacturing scale-up and regulatory activities. The BARDA Contract consists of an approximately two-year base period during which BARDA will provide up to approximately $21 million of funding for the RAISE trial on a cost share basis and funding of additional preclinical studies of ganaxolone in nerve agent exposure models. Following successful completion of the RAISE trial and preclinical studies in the base period, the BARDA Contract provides for approximately $30 million of additional BARDA funding for three options in support of ganaxolone manufacturing, supply chain, clinical, regulatory and toxicology activities. Under the BARDA Contract, we will be responsible for cost sharing in the amount of approximately $33 million and BARDA will be responsible for approximately $51 million , if all development options are completed. The contract period-of-performance (base period plus option exercises) is up to approximately five years . In connection with the closing of an equity financing in December 2020, we issued a total of 5,000,000 shares of common stock in an underwritten public offering resulting in aggregate net proceeds, after underwriting discounts and commissions in the public offering and other estimated offering expenses, of $64.8 million. In connection with the closing of an equity financing in June 2020, we issued a total of 4,600,000 shares of common stock in an underwritten public offering resulting in aggregate net proceeds, after underwriting discounts and commissions in the public offering and other estimated offering expenses, of $43.0 million. Management’s operating plan which underlies the analysis of our ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Actual results could vary from the operating plan. We follow the provisions of Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 205-40, Presentation of Financial Statements—Going Concern, which requires management to assess our ability to continue as a going concern within one year after the date the financial statements are issued. Our balance of cash and cash equivalents on hand as of December 31, 2021, excluding the $20.0 million liquidity requirement associated with our Note Payable (Note 10), is not sufficient to fund operations for the one-year period after the date the financial statements are issued. As a result, there is substantial doubt about our ability to continue as a going concern through the one-year period from the date these financial statements are issued. Management’s plans that are intended to mitigate this risk include the monetization of our Priority Review Voucher and additional financing or strategic transactions. Management’s plans may also include drawing down Tranche B ( and will continue to evaluate available alternatives to extend our operations beyond the one-year period after the date the financial statements are issued. Reverse stock split On September 23, 2020, we effected a 1 -for-4 reverse split of shares of our common stock (Reverse Split), as approved by our board of directors and stockholders. The par value per share of our common stock was not adjusted as a result of the Reverse Split, and our authorized shares of common stock was reduced to 150,000,000 . All of the share and per share amounts included in the accompanying financial statements and these notes have been adjusted to reflect the Reverse Split

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The financial statements include the accounts of Marinus Pharmaceuticals, Inc. (the Company) and its wholly-owned subsidiary as of December 31, 2021. During the year ended December 31, 2020, a wholly-owned subsidiary was liquidated. In February 2021, a new wholly-owned subsidiary was established in Ireland. All intercompany accounts and transactions have been eliminated. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from such estimates. Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. We view our operations and manage our business in one segment, which is the identification and development of innovative therapeutics to treat rare seizure disorders. Fair Value of Financial Instruments and Credit Risk At December 31, 2021, our financial instruments included cash equivalents, accounts payable, accrued expenses, and notes payable. At December 31, 2020, our financial instruments included cash equivalents, short-term investments, accounts payable and accrued expenses. The carrying amount of cash equivalents, accounts payable and accrued expenses approximated fair value, given their short-term nature. The carrying amounts of short-term investments are recorded at amortized cost, which for U.S. Treasury securities is based on the current market price of each security at the measurement date. The carrying value of the notes payable approximates fair value as the interest rate is reflective of current market rates on debt with similar terms and conditions. Cash equivalents and certificates of deposit subject us to concentrations of credit risk. However, we invest our cash in accordance with a policy objective that seeks to ensure both liquidity and safety of principal. The policy limits investments to instruments issued by the U.S. government, certain Securities and Exchange Commission (SEC)-registered money market funds that invest only in U.S. government obligations and various other low-risk liquid investment options, and places restrictions on portfolio maturity terms. Cash and Cash Equivalents We consider all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. As of December 31, 2021 and 2020, we invested a portion of our cash balances in money market investments, which we have included as cash equivalents on our balance sheets. Investments We did not have any investments as of December 31, 2021. As of December 31, 2020, our investments consisted of certificates of deposit with various financial institutions, with original maturities ranging from six to nine months. All investments were classified as held-to-maturity and were recorded at amortized cost. Interest income includes interest and dividends, realized gains and losses on sales of securities, if any. Accounts Receivable Accounts receivable represents amounts due to us under the BARDA contract for valid expenditures expected to be reimbursed to us under the terms of the BARDA contract and current amounts due to us from Orion Corporation under our collaboration agreement (Note 11). Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets generally represent payments made for goods or services to be received within one year, and are expensed as the related benefit is received. Property and Equipment Property and equipment consist of laboratory and office equipment and are recorded at cost. Property and equipment are depreciated on a straight-line basis over their estimated useful lives. We estimate a life of three years for computer equipment, including software, five years for office equipment and furniture, five to fifteen years for laboratory equipment, and six years for leasehold improvements. When property and equipment are sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss is included in operating expenses. Impairment of Long-Lived Assets We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. If the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount an impairment loss would be recognized if the carrying value of the asset exceeded its fair value. Fair value is generally determined using discounted cash flows. Income Taxes a full valuation allowance is necessary for our net deferred tax assets. We had no material amounts recorded for uncertain tax positions, interest or penalties in the accompanying financial statements. Debt Issuance Costs Contract Liability Federal Contract Revenue We recognize federal contract revenue from the BARDA Contract in the period in which the allowable research and development expenses are incurred, and receivables associated with this revenue are included within accounts receivable on our balance sheets. This revenue is not within the scope of Accounting Standards Codification (ASC) 606 – Revenue from contracts with customers. Collaboration and Licensing Revenue We must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price may include such estimates as forecasted revenues and costs, development timelines, discount rates and probabilities of regulatory and commercial success. We also apply significant judgment when evaluating whether contractual obligations represent distinct performance obligations, allocating transaction price to performance obligations within a contract, determining when performance obligations have been met, assessing the recognition and future reversal of variable consideration and determining and applying appropriate methods of measuring progress for performance obligations satisfied over time. Research and Development Research and development costs are expensed as incurred. Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as subject enrollment, monitoring visits, clinical site activations, or information provided to us by our vendors with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development expense, as the case may be. Clinical Trial Expenses As part of the process of preparing our financial statements, we are required to estimate our expenses resulting from our obligations under contracts with vendors, clinical research organizations and consultants and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. Our objective is to reflect the appropriate trial expenses in our financial statements by matching those expenses with the period in which services are performed and efforts are expended. We account for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. We determine accrual estimates based on estimates of services received and efforts expended that take into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials. During the course of a clinical trial, we adjust our clinical expense recognition if actual results differ from its estimates. We make estimates of our accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. Our clinical trial accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2021 and 2020 there were no material adjustments to our prior period estimates of accrued expenses for clinical trials. Stock-Based Compensation We account for stock-based compensation in accordance with the provisions of Accounting Standards Codification (ASC) Topic 718, Compensation—Stock Compensation Loss Per Share of Common Stock Basic loss per share is computed by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, and unvested restricted stock, which would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share applicable to common stockholders, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation. These potentially dilutive securities are more fully described in Note 8. The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31, 2021 and 2020 (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 ​ Basic and diluted net loss per share of common stock: ​ ​ ​ Net loss ​ $ (98,776) ​ $ (67,475) ​ Deemed Dividends ​ ​ — ​ ​ (8,880) ​ Net loss applicable to common stockholders ​ $ (98,776) ​ $ (76,355) ​ Weighted average shares of common stock outstanding ​ 36,697,171 ​ 27,270,055 ​ Net loss per share of common stock—basic and diluted ​ $ (2.69) ​ $ (2.80) ​ ​ The following potentially dilutive securities (common stock equivalents) have been excluded from the computation of diluted weighted average shares outstanding, as they would be antidilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 ​ Convertible preferred stock 915,000 950,600 Restricted stock 26,025 24,625 Stock options 4,738,855 3,507,638 Total 5,679,880 4,482,863 ​ The convertible preferred stock meets the definition of a participating security; however, the holders are not obligated to share in our losses. As of December 31, 2021 and 2020, we had no other potentially dilutive securities.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements FASB accounting guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability (exit price) in an orderly transaction between market participants at the measurement date. The accounting guidance outlines a valuation framework and creates a fair value hierarchy in order to increase the consistency and comparability of fair value measurements and the related disclosures. In determining fair value, we use quoted prices and observable inputs. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from independent sources. The fair value hierarchy is broken down into three levels based on the source of inputs as follows: ● Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities. ● Level 2—Valuations based on observable inputs and quoted prices in active markets for similar assets and liabilities. ● Level 3—Valuations based on inputs that are unobservable and models that are significant to the overall fair value measurement. If the inputs used to measure fair value fall within different levels of the hierarchy, the category level is based on the lowest priority level input that is significant to the fair value measurement of the instrument. As of December 31, 2021 and 2020, all of our financial assets and liabilities were classified as Level 1 valuations. The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total December 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 2,360 ​ $ — ​ $ — ​ $ 2,360 ​ Money market funds (cash equivalents) ​ ​ 120,567 ​ ​ — ​ ​ — ​ ​ 120,567 ​ Total assets ​ $ 122,927 ​ $ — ​ $ — ​ $ 122,927 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 138,509 ​ $ — ​ $ — ​ $ 138,509 ​ Certificates of deposit ​ ​ 1,474 ​ ​ — ​ ​ — ​ ​ 1,474 ​ Total assets ​ $ 139,983 ​ $ — ​ $ — ​ $ 139,983 ​ ​

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2021
Property and Equipment
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2021 ​ 2020 Laboratory equipment $ 2,565 $ 1,777 ​ Leasehold improvements ​ ​ 899 ​ ​ 899 ​ Office furniture and equipment ​ 429 ​ 401 ​ Total property and equipment ​ 3,893 ​ 3,077 ​ Less: accumulated depreciation ​ (1,394) ​ (1,132) ​ Total property and equipment, net ​ $ 2,499 ​ $ 1,945 ​ ​ Depreciation expense was $0.3 million and $0.3 million for the years ended December 31, 2021 and 2020, respectively. In 2021, we determined certain of our laboratory equipment was not required and now held for sale. The resulting write-down of $0.2 million of net equipment was recorded as a loss and included in Other income (expense), net on the Statement of operations.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2021
Accrued Expenses
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Payroll and related costs ​ $ 5,830 ​ $ 4,097 Clinical trials and drug development ​ ​ 8,217 ​ ​ 2,452 ​ Professional fees ​ ​ 1,311 ​ ​ 927 ​ Short-term lease liabilities ​ ​ 556 ​ ​ 510 ​ Other ​ ​ 293 ​ ​ 532 ​ Total accrued expenses ​ $ 16,207 ​ $ 8,518 ​ ​

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases
Leases	6. Leases We have entered into one operating lease for real estate. This lease has a term of 78 months , and includes renewal terms which can extend the lease term by 60 months , which is included in the lease term when it is reasonably certain that we will exercise the option. As of December 31, 2021, our operating lease had a weighted average remaining lease term of 45 months . The right-of-use (ROU) asset is included in " Other assets " on our balance sheets as of December 31, 2021 and 2020, and represents our right to use the underlying asset for the lease term. Our obligations to make lease payments are included in "Accrued expenses" and " Other long-term liabilities " on our balance sheets as of December 31, 2021 and 2020. The ROU asset was initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date, plus any initial direct costs incurred, less any lease incentives received. The ROU asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, plus initial direct costs, plus (minus) any prepaid (accrued) lease payments, less the unamortized balance of lease incentives received. As of December 31, 2021 and 2020, ROU assets were $1.7 million and $2.0 million, respectively, and operating lease liabilities were $2.5 million and $3.0 million, respectively. We have entered into various short-term operating leases, primarily for clinical trial equipment, with an initial term of twelve months or less. These leases are not recorded on our balance sheets. All operating lease expense is recognized on a straight-line basis over the lease term. During the years ended December 31, 2021 and 2020, we recognized $0.6 million and $0.6 million, respectively, in total lease costs, which included less than $0.1 million in short-term lease costs related to short-term operating leases in each year. Because the rate implicit in the lease is not readily determinable, we use our incremental borrowing rate to determine the present value of the lease payments. The weighted average incremental borrowing rate used to determine the initial value of the ROU asset and lease liability was 11.0%, derived from a corporate yield curve based on a synthetic credit rating model using a market signal analysis. We have certain contracts for real estate which may contain lease and non-lease components which we have elected to treat as a single lease component. ROU assets for operating leases are periodically reduced by impairment losses. We use the long-lived assets impairment guidance in ASC Subtopic 360-10, Property, Plant, and Equipment – Overall, to determine whether an ROU asset is impaired, and if so, the amount of the impairment loss to recognize. As of December 31, 2021 and 2020, we have not recognized any impairment losses for our ROU assets. We monitor for events or changes in circumstances that require a reassessment of one of our leases. When a reassessment results in the remeasurement of a lease liability, a corresponding adjustment is made to the carrying amount of the corresponding ROU asset unless doing so would reduce the carrying amount of the ROU asset to an amount less than zero. In that case, the amount of the adjustment that would result in a negative ROU asset balance is recorded in our statements of operations and comprehensive loss. Maturities of operating lease liabilities as of December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ $ 807 ​ 2023 ​ 823 ​ 2024 ​ 840 ​ Thereafter ​ 643 ​ ​ ​ ​ 3,113 ​ Less: imputed interest ​ ​ (578) ​ Total lease liabilities ​ $ 2,535 ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 556 ​ Non-current operating lease liabilities ​ ​ 1,979 ​ Total lease liabilities ​ $ 2,535 ​ ​

Investments

Investments	12 Months Ended
	Dec. 31, 2021
Investments
Investments	7. Investments We did not have any investments as of December 31, 2021. We have never experienced a credit loss on the principal or interest receivable of our cash equivalents or short-term investments. Our certificates of deposit are each individually and fully insured by the FDIC. Accordingly, we did not record any allowance for potential credit losses as of December 31, 2020.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity
Stockholders' Equity	8. Stockholders’ Equity In 2005, we adopted the 2005 Stock Option and Incentive Plan (2005 Plan) that authorizes us to grant options, restricted stock and other equity-based awards. As of December 31, 2021, 577 options to purchase shares of common stock were outstanding pursuant to grants in connection with the 2005 Plan. additional shares are available for issuance under the 2005 Plan. The amount, terms of grants, and exercisability provisions are determined and set by our board of directors. Effective August 2014, we adopted our 2014 Equity Incentive Plan, as amended (2014 Plan) that authorizes us to grant options, restricted stock, and other equity-based awards, subject to adjustment in accordance with the 2014 Plan. As of December 31, 2021, . In accordance with the 2014 Plan, on January 1, 2022, the shares of common stock available for future grants under the 2014 Plan was increased to 2,521,079. In addition, during the years ended December 31, 2021 and 2020, we granted 772,117 and 852,024 options, respectively, to purchase shares of common stock outside of our 2014 Plan as inducement grants material to new employees entering into employment agreements with us pursuant to Nasdaq Listing Rule 5635(c)(4). The amount, terms of grants, and exercisability provisions of these grants are determined and set by our board of directors, and are largely consistent with the terms and exercisability provisions of grants under our 2014 Plan. Stock Options Total compensation cost recognized for all stock option awards in the statements of operations is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2021 ​ 2020 ​ Research and development $ 4,482 $ 2,938 General and administrative ​ 9,106 ​ 4,521 ​ Total ​ $ 13,588 ​ $ 7,459 ​ ​ Options issued under both the 2005 Plan and 2014 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Exercise Price ​ Intrinsic ​ ​ Shares ​ Per Share ​ Value Outstanding—December 31, 2019 2,135,070 ​ $ 15.80 ​ ​ ​ ​ Granted 1,905,850 ​ 9.17 ​ ​ ​ ​ Exercised ​ (198,475) ​ 5.16 ​ ​ ​ ​ Forfeited ​ (180,107) ​ ​ 11.04 ​ ​ ​ ​ Expired ​ (154,700) ​ ​ 25.16 ​ ​ ​ ​ Outstanding—December 31, 2020 3,507,638 ​ $ 12.64 ​ ​ ​ ​ Granted 1,868,066 ​ 13.49 ​ ​ ​ ​ Exercised (176,194) ​ 6.80 ​ ​ ​ ​ Forfeited ​ (225,726) ​ ​ 11.85 ​ ​ ​ ​ Expired ​ (234,929) ​ ​ 32.81 ​ ​ ​ ​ Outstanding—December 31, 2021 4,738,855 ​ $ 12.23 ​ $ 9,531 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable—December 31, 2021 2,450,061 ​ $ 12.56 ​ $ 6,521 ​ ​ The weighted average remaining contractual term of options outstanding and exercisable as of December 31, 2021 is 8.2 years and 7.6 years, respectively. Intrinsic value in the table above was determined by calculating the difference between the market value of our common stock on the last trading day of 2021 of $11.88 per share and the exercise price, for any in-the-money options. The weighted-average grant date fair value of options granted was $11.54 and $7.81 per share in 2021 and 2020, respectively, and was estimated at the date of grant using the Black-Scholes option-pricing model with the following ranges of weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 ​ Expected stock price volatility 115 - 124 % 116 - 122 % ​ Expected term of options 5.0 - 6.1 years 5.3 - 6.1 years ​ Risk‑free interest rate 0.44 - 1.33 % 0.31 - 1.73 % ​ Expected annual dividend yield ​ ​ 0 % ​ ​ 0 % ​ ​ The weighted-average valuation assumptions were determined as follows: ● Expected stock price volatility: The expected volatility is based on historical volatility of our stock price. ● Expected term of options: We estimated the expected term of our stock options with service-based vesting using the “simplified” method, as prescribed in SAB No. 107, whereby the expected life equals the average of the vesting tranches and the original contractual term of the option due to our lack of sufficient historical data. ● Risk-free interest rate: We base the risk-free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term. ● Expected annual dividend yield: The estimated annual dividend yield is 0% because we have not historically paid, and do not expect for the foreseeable future to pay, a dividend on our common stock. As of December 31, 2021, there was $21.0 million of total unrecognized compensation expense related to unvested stock options. That expense is expected to be recognized over the next four years as follows, in thousands: ​ ​ ​ ​ ​ 2022 $ 9,716 2023 ​ 7,315 2024 ​ 3,186 2025 ​ 768 ​ ​ $ 20,985 ​ Restricted Stock All issued and outstanding restricted shares of common stock are time-based and become vested within two years after the grant date, pursuant to the 2014 Plan. Compensation expense is recorded ratably over the requisite service period. Compensation expense related to restricted stock is measured based on the fair value using the closing market price of our common stock on the date of the grant. A summary of activity for the years ended December 31, 2021 and 2020 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ average ​ ​ ​ ​ Grant Date ​ ​ Shares ​ Fair Value per Share Outstanding—December 31, 2019 8,100 ​ $ 4.84 Granted 34,000 ​ ​ 12.93 Vested (17,475) ​ ​ 10.04 Outstanding—December 31, 2020 ​ 24,625 ​ ​ 11.41 Granted ​ 18,400 ​ ​ 13.48 Vested ​ (17,000) ​ ​ 12.93 Outstanding—December 31, 2021 26,025 ​ $ 12.75 ​ ​ ​ ​ ​ ​ Expected to vest—December 31, 2021 26,025 ​ $ 12.75 ​ As of December 31, 2021, there was $0.3 million in unrecognized compensation cost related to unvested restricted stock. Total compensation cost recognized for all restricted stock awards in the statements of operations for the years ended December 31, 2021 and 2020 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Research and development $ 3 $ — General and administrative ​ 276 ​ 183 Total ​ $ 279 ​ $ 183 ​ Equity Distribution Agreement In October 2017, we entered into an Equity Distribution Agreement (Prior EDA) with JMP Securities LLC (JMP), under which JMP, as our exclusive agent, at our discretion and at such times that we may determine from time to time, may sell over a three-year period from the execution of the agreement up to a maximum of $50 million of shares of our common stock. During the year ended December 31, 2020, we issued 78,807 shares of its common stock pursuant to the Prior EDA for aggregate net proceeds of $0.5 million. On July 9, 2020, we entered into a new Equity Distribution Agreement (New EDA) with JMP to create an at the market equity program under which we from time to time may offer and sell shares of our common stock having an aggregate offering price of up to $60.0 million through or to JMP. Subject to the terms and conditions of the New EDA, JMP will use its commercially reasonable efforts to sell shares of our common stock from time to time, based upon our instructions. JMP will be entitled to a commission of up to 3.0% of the gross proceeds from each sale of shares of our common stock. The New EDA superseded and terminated the Prior EDA effective immediately upon effectiveness of our shelf registration statement on Form S-3 (File No. 333-239780) filed with the Securities and Exchange Commission on July 9, 2020 and declared effective by the Securities and Exchange Commission on July 27, 2020 . We did not sell any shares of our common stock during the year ended December 31, 2021 under the New EDA. ​ Public Offerings In connection with the closing of an equity financing in December 2020, we issued a total of 5,000,000 shares of common stock in an underwritten public offering resulting in aggregate net proceeds, after underwriting discounts and commissions in the public offering and other estimated offering expenses, of $64.8 million . In connection with the closing of an equity financing in June 2020, we issued a total of 4,600,000 shares of common stock in an underwritten public offering resulting in aggregate net proceeds, after underwriting discounts and commissions in the public offering and other estimated offering expenses, of $43.0 million.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2021
Convertible Preferred Stock.
Convertible Preferred Stock	9. Convertible Preferred Stock Concurrent with the 2019 Public Offering, we entered into a Securities Purchase Agreement (Purchase Agreement), by and among us and the investors listed therein. Pursuant to the terms of the Purchase Agreement, we sold to the investors an aggregate of 30,000 shares of Series A Participating Convertible Preferred Stock, par value $0.001 per share (Series A Preferred Stock), at a per share price of $1,000 in a private placement (Private Placement), and received net proceeds of $28.2 million, after deducting underwriting discounts and commissions of $1.8 million. Each share of Series A Preferred Stock will be convertible into 200 shares of common stock, reflecting a conversion price equal to $5.00 per share, subject to customary anti-dilution adjustments. The shares of Series A Preferred Stock will be mandatorily convertible into shares of common stock, subject to a beneficial ownership limitation (described below), in partial or in full, thereof from and after filing the certificate of amendment to our charter with the Secretary of State of the State of Delaware to increase our authorized shares of common stock (Exercise Contingency). The holders of the Series A Preferred Stock had a feature that allowed the holders to have a liquidation preference to our common stockholders. Because such a potential redemption-triggering event was not solely within our control, the Series A Preferred Stock was presented as "Convertible Preferred Stock" on our December 31, 2019 balance sheet in a manner consistent with temporary equity under applicable accounting standards. During the year ended December 31, 2021, 178 shares of our Series A Preferred Stock converted into 35,600 shares of our common stock, pursuant to the terms of the P urchase A greement. As of December 31, 2021, 4,575 shares of our Series A Preferred Stock remain ed outstanding, convertible into 915,000 shares of our common stock. In May 2020, a registration statement covering the resale of shares of our common stock underlying our Series A Preferred Stock was declared effective by the Securities and Exchange Commission (SEC). In accordance with the securities purchase agreements underlying the Series A Preferred Stock, the liquidation preference was terminated at that time, and we reclassified the Series A Preferred Stock into permanent equity The holders of the Series A Preferred Stock also have the right to receive discretionary dividends paid to common shareholders. Except as required by law, the Series A Preferred Stock is non-voting stock. The holders The difference between the conversion price and the fair value of our common stock on the commitment date (transaction date) resulted in a beneficial conversion feature the amount of $8.9 million.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2021
Notes Payable
Notes Payable	10. Notes Payable On May 11, 2021 (Closing Date) and as amended on May 17, 2021, we entered into the Credit Agreement with Oaktree Fund Administration, LLC as administrative agent (Oaktree) and the lenders party thereto (collectively, the Lenders) that provides for a five-year senior secured term loan facility in an aggregate original principal amount of up to $125.0 million, available to us in five tranches (collectively, the Term Loans). Upon entering into the Credit Agreement in May 2021, we borrowed $15.0 million in term loans from the Lenders (Tranche A-1 Term Loan) and upon receipt of written acceptance by the FDA of our NDA filing relating to the use of ganaxolone in CDD in September 2021, we borrowed $30.0 million of tranche A-2 term loans from the Lenders (Tranche A-2 Term Loan). Under the terms of the Credit Agreement, we may, at our sole discretion, borrow from the Lenders up to an additional $80.0 million in term loans subject to certain milestone events, as follows: ● Through December 31, 2022, $30.0 million of tranche B term loans became available for draw upon FDA approval of ZTALMY for CDD in March 2022. ● Through June 30, 2023, $25.0 million of tranche C term loans will be available for draw if we complete one or more financings (including through the issuance of common stock, convertible debt, subordinated debt, a synthetic royalty, or a sublicense) resulting in gross proceeds to us of at least $40.0 million and net proceeds to us of at least $36.0 million. In addition, the availability of this tranche is subject to certain clinical outcomes. ● Through December 31, 2023, $25.0 million of tranche D term loans will be available for draw if we earn an aggregate of at least $50 million in net product revenue in the U.S. for a trailing six consecutive months. In addition, the Credit Agreement contains a minimum liquidity covenant that requires us to maintain cash and cash equivalents of at least $20.0 million from the funding of the tranche A- 2 term loans until the funding of the tranche B term loans, and at least $15.0 million from the funding date of the tranche B term loans until the maturity of the Term Loans. The Term Loans will be guaranteed by certain of our future subsidiaries (Guarantors). Our obligations under the Credit Agreement are secured by a pledge of substantially all of our assets and will be secured by a pledge of substantially all of the assets of the Guarantors. The Term Loans mature on May 11, 2026 (Maturity Date). The Term Loans bear interest at a fixed per annum rate (subject to increase during an event of default) of 11.50% , and we are required to make quarterly interest payments until the Maturity Date. We are also required to make quarterly principal payments beginning on June 30, 2024 in an amount equal to 5.0% of the aggregate amount of the Term Loans outstanding on June 30, 2024, and continuing until the Maturity Date. On the Maturity Date, we are required to pay in full all outstanding Term Loans and other amounts owed under the Credit Agreement. At the time of borrowing any tranche of the Term Loans, we are required to pay an upfront fee of 2.0% of the aggregate principal amount borrowed at that time. In addition, a commitment fee of 75 basis points per annum will accrue on each of the tranche B, C, and D commitments for the period beginning 120 days after the funding date of the tranche A-2 term loans until the applicable tranche is either funded or terminated. We may prepay all or any portion of the Term Loans, and are required to make mandatory prepayments of the Term Loans from the proceeds of asset sales, casualty and condemnation events, and prohibited debt issuances, subject to certain exceptions. All mandatory and voluntary prepayments of the Term Loans are subject to prepayment premiums equal to (i) of the principal prepaid if prepayment occurs after May 11, 2024 but on or before May 11, 2025. If prepayment occurs after May 11, 2025, prepayment premium is due. We are also required to make mandatory prepayments of the Term Loans upon an event of default under the Credit Agreement resulting from the occurrence of a change of control. These mandatory prepayments are subject to a prepayment premium equal to (i) In addition, we are required to pay an exit fee in an amount equal to 2.0% of all principal repaid, whether as a mandatory prepayment, voluntary prepayment, or a scheduled repayment. In addition to the minimum liquidity covenant, we are subject to a number of affirmative and restrictive covenants under the Credit Agreement, including limitations on its ability and its subsidiaries’ abilities, among other things, to incur additional debt, grant or permit additional liens, make investments and acquisitions, merge or consolidate with others, dispose of assets, pay dividends and distributions, and enter into affiliate transactions, subject to certain exceptions. As of December 31, 2021, we were in compliance with all covenants. Upon the occurrence of certain events, including but not limited to our failure to satisfy our payment obligations under the Credit Agreement, the breach of certain of our other covenants under the Credit Agreement, the occurrence of cross defaults to other indebtedness, or defaults related to enforcement action by the FDA or other Regulatory Authority or recall of ganaxolone, Oaktree and the Lenders will have the right, among other remedies, to accelerate all amounts outstanding under the Term Loans and declare all principal, interest, and outstanding fees immediately due and payable. In September 2021, we borrowed $30.0 million upon receipt of written acceptance by the FDA of our NDA filing relating to the use of ganaxolone in the treatment of CDD and incurred debt issuance costs of $1.2 million, including the exit fee of $0.6 million, that are classified as contra-liability on our consolidated balance sheets and are being recognized as interest expense over the term of the loan using the effective-interest method. In May 2021, we borrowed $15.0 million upon entering into the Credit Agreement and incurred debt issuance costs of $4.4 million, including the exit fee of $0.3 million, that are classified as a contra-liability on the consolidated balance sheet and are being recognized as interest expense over the term of the loan using the effective-interest method. For the year ended December 31, 2021, we recognized interest expense of $2.6 million, of which $2.0 million was interest on the Term Loans and $0.6 million was non-cash interest expense related to the amortization of debt issuance costs. The following table summarizes the composition of Notes payable as reflected on the consolidated balance sheet as of December 31, 2021 (in thousands): ​ ​ ​ ​ Gross proceeds ​ $ 45,000 Contractual exit fee ​ 900 Unamortized debt discount and issuance costs ​ (5,091) Total ​ $ 40,809 ​ The aggregate maturities of Notes payable as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ 2022 ​ $ — 2023 ​ ​ — 2024 ​ ​ 6,825 2025 and thereafter ​ ​ 38,175 Total ​ $ 45,000 ​

License and Collaboration Reven

License and Collaboration Revenue	12 Months Ended
	Dec. 31, 2021
License and Collaboration Revenue
License and Collaboration Revenue	11. License and Collaboration Revenue In July 2021, we entered into a collaboration agreement (Orion Collaboration Agreement) with Orion Corporation (Orion). The Orion Collaboration Agreement falls under the scope of ASC Topic 808, Collaborative Arrangements (ASC 808) as both parties are active participants in the arrangement that are exposed to significant risks and rewards. While this arrangement is in the scope of ASC 808, we analogize to ASC 606 for some aspects of this arrangement, including for the delivery of a good or service (i.e., a unit of account). Revenue recognized by analogizing to ASC 606 is recorded as collaboration revenue on the statements of operations. Under the terms of the Orion Collaboration Agreement, we granted Orion an exclusive, royalty-bearing, sublicensable license to certain of our intellectual property rights with respect to commercializing biopharmaceutical products incorporating our product candidate ganaxolone (Licensed Products) in the European Economic Area, the United Kingdom and Switzerland (collectively, the Territory) for the diagnosis, prevention and treatment of certain human diseases, disorders or conditions (Field), initially in the indications of CDD, tuberous sclerosis complex (TSC) and refractory status epilepticus (RSE). We will be responsible for the continued development of Licensed Products and regulatory interactions related thereto, including conducting and sponsoring all clinical trials, provided that Orion may conduct certain post-approval studies in the Territory. Orion will be responsible, at Orion’s sole cost and expense, for the commercialization of any Licensed Product in the Field in the Territory. Under the terms of the Orion Collaboration Agreement, we received a €25.0 million ( $29.6 million) upfront payment from Orion in July 2021. In connection with the upfront fee, we agreed to provide Orion with the results of a planned genotoxicity study on the M2 metabolite of ganaxolone, a “Combined Micronucleus & Comet study in vivo.” In the event that the results of such study were positive, based on the criteria set forth in the study’s protocol, Orion would have had the right to terminate the Collaboration Agreement within ninety ( 90 ) days after its receipt of the final report of such study, in which case we would have been required to refund Orion seventy-five percent ( 75% ) of the upfront fee. In the event of such termination and refund, Orion would have had no further rights pursuant to the oral and IV dose formulations of ganaxolone and the Orion Collaboration Agreement would have terminated and been of no further force or effect. In February 2022, the verified draft study report showed that no genotoxicity was found, as measured by formation of micronuclei in the bone marrow or comet morphology in the liver. As such, but subject to confirmation of such results in the final study report expected by the end of the second quarter of 2022, we will not be required to refund Orion any of the upfront fee and Orion will not have a right to terminate the Orion Collaboration Agreement as a result of the study’s findings. We are eligible to receive up to an additional €97 million in R&D reimbursement and cash milestone payments based on specific clinical and commercial achievements, as well as tiered royalty payments based on net sales ranging from the low double-digits to high teens for the oral programs and the low double-digits to low 20s for the IV program. Also, as part of the overall arrangement, we have agreed to supply the Licensed Products to Orion at an agreed upon price. The Orion Collaboration Agreement shall remain effective until the date of expiration of the last to expire Royalty Term, which is defined as the period beginning on the date of the first commercial sale Licensed Product in such country and ending on the latest to occur of (a) the tenth (10th) anniversary of the first commercial sale of Licensed Product in such country, (b) the expiration of the last-to-expire licensed patent covering the manufacture, use or sale of such Licensed Product in such country, and (c) the expiration of regulatory exclusivity period, if any, for such Licensed Product in such country. The Orion Collaboration Agreement has a term of at least ten ( 10 ) years since a commercial sale has yet to occur. The Orion Collaboration Agreement allows for termination in certain specific events, such as material breach, in the event Orion challenges the validity, enforceability or scope of the licensed patent rights, termination for forecast failure, insolvency and force majeure, none of which are probable at contract inception. In accordance with the guidance, we identified the following commitments under the arrangement: (i) exclusive rights to develop, use, sell, have sold, offer for sale and import any product comprised of Licensed Product (License) (ii) development and regulatory activities (Development and Regulatory Activities), and (iii) requirement to supply Orion with the Licensed Product at an agreed upon price (Supply of Licensed Product). We determined that these three commitments represent distinct performance obligations for purposes of recognizing revenue or reducing expense, which it will recognize such revenue or expense, as applicable, as it fulfills these performance obligations. We determined that the non-refundable portion of the upfront payment plus the research and development reimbursement constitutes the transaction price as of the outset of the Orion Collaboration Agreement. The refundable portion of the upfront payment and the future potential regulatory and development milestone payments were fully constrained at contract inception as the risk of significant revenue reversal related to these amounts has not yet been resolved. The achievement of the future potential milestones is not within our control and is subject to certain research and development success and therefore carry significant uncertainty. We will reevaluate the likelihood of achieving these milestones at the end of each reporting period and adjust the transaction price in the period the risk is resolved. In addition, we will recognize any consideration related to sales-based milestones and royalties when the subsequent sales occur since those payments relate primarily to the License, which was delivered by us to Orion upon entering into the Orion Collaboration Agreement. The The transaction price was allocated to the three performance obligations based on the estimated stand-alone selling prices at contract inception. The stand-alone selling price of the License was based on a discounted cash flow approach and considered several factors including, but not limited to, discount rate, development timeline, regulatory risks, estimated market demand and future revenue potential using an adjusted market approach. The stand-alone selling price of the Development and Regulatory Activities and the Supply of Licensed Product was estimated using the expected cost-plus margin approach. ​ ​ As of the agreement date in July 2021, we allocated the transaction price to the performance obligations as described below and recorded the $9.0 million transaction price associated with the License as Revenue. During 2021, we amortized $0.1 million of the transaction price associated with the Development and Regulatory Services as a reduction of research and development costs. These reductions to transaction price resulted in a total contract liability of $6.6 million. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative ​ ​ ​ Transaction ​ Collaboration ​ Contract ​ Price Recognized Liability License $ 8,987 ​ $ 8,987 ​ $ - Development and Regulatory Services ​ 2,787 ​ ​ 106 ​ ​ 2,681 Supply of License Product ​ 3,943 ​ ​ - ​ ​ 3,943 Total contract liability $ 15,717 ​ $ 9,093 ​ ​ 6,624 Less current portion of contract liability ​ ​ ​ ​ ​ ​ ​ (869) Total long-term contract liability ​ ​ ​ ​ ​ ​ $ 5,755 ​ In accordance with ASC 210-20, the above contract liability of $6.6 million is offset by a contract asset of $7.2 million related to the reimbursement of research and development costs, resulting in a net Contract asset of $0.6 million. We incurred $2.0 million of incremental costs in obtaining the Orion Collaboration Agreement. These contract acquisition costs were allocated consistent with the transaction price, resulting in $1.1 million of expense recorded to General and administrative expense commensurate with the recognition of the License performance obligation and $0.9 million recorded as capitalized contract costs, included in Other current assets and Other assets, which will be amortized as Development and Regulatory Services and Supply of License Product obligations are met. Cost of collaboration revenue of $1.5 million represents a one-time fee paid to Purdue Neuroscience Company related to our license agreement and was paid in conjunction with the €25.0 million upfront fees received from Orion. We reevaluate the transaction price and the total estimated costs expected to be incurred to satisfy the performance obligations and adjusts the deferred revenue at the end of each reporting period. Such changes will result in a change to the amount of collaboration revenue recognized and deferred revenue.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies
Commitments and Contingencies	12. Commitments and Contingencies Employee Benefit Plan We maintain a Section 401(k) retirement plan for all employees. The plan allows employees to make contributions up to a specified percentage of their compensation, subject to maximum amounts allowed under law. Beginning January 1, 2021, we contribute 3% of compensation to each employee’s 401(k) retirement account. We contributed $0.7 million for the year ending December 31, 2021. We also can make discretionary profit sharing contributions, which would vest over a period of four years from each employee’s commencement of employment with us. We have not made any discretionary contributions. License Agreements We are obligated to pay royalties pursuant to a license agreement with Purdue Neuroscience Company (Purdue) as a percentage of net product sales for direct licensed products, such as ganaxolone. The obligation to pay royalties expires, on a country-by-country basis, 10 years from the first commercial sale of a licensed product in each country. The agreement also requires that we pay Purdue a percentage of the non-royalty consideration that we receive from a sublicensee and a percentage of milestone payments for indications other than seizure disorders and vascular migraine headaches not associated with mood disorders. Under the license agreement, we are committed to use commercially reasonable efforts to develop and commercialize at least one licensed product. In March 2017, we and CyDex Pharmaceuticals, Inc. (CyDex) entered into a License Agreement and a Supply Agreement. Under the terms of the License Agreement, CyDex has granted us an exclusive license to use sulfobutylether beta-cyclodextrin, CyDex’s Captisol® drug formulation system, and related intellectual property in connection with the development and commercialization of ganaxolone in any and all therapeutic uses in humans, with some exceptions. As consideration for this license, we paid an upfront fee which was recorded as research and development expense in 2017, and are required to make additional payments in the future upon achievement of various specified clinical and regulatory milestones. We will also be required to pay royalties to CyDex on sales of ganaxolone, if successfully developed, in the low-to-mid single digits based on levels of annual net sales. To date, we have achieved one milestone under the License Agreement, which occurred and was paid in the first quarter of 2021 . Under the terms of the Supply Agreement, we are required to purchase all of our requirements for Captisol with respect to ganaxolone from CyDex, and CyDex is required to supply us with Captisol for such purposes, subject to certain limitations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Taxes
Income Taxes	13. Income Taxes Loss before income taxes is allocated as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2021 ​ 2020 ​ ​ U.S. operations ​ $ 98,776 ​ $ 67,475 ​ ​ Foreign operations ​ — ​ — ​ ​ Loss before income taxes ​ $ 98,776 ​ $ 67,475 ​ ​ ​ As of December 31, 2021 and 2020, we had approximately $303.3 million and $212.0 million, respectively, of net operating loss (NOL) carry forwards available to offset future federal taxable income, $128.1 million of which will expire beginning in 2023, and the remaining amount can be carried forward indefinitely. As of December 31, 2021 and 2020, we had approximately $253.0 million and $209.5 million, respectively, of NOL carry forwards available to offset future state taxable income that will expire beginning in 2023. As of December 31, 2021, we also have federal research and development credit carryovers of approximately $15.8 million and state credit carryovers of approximately $0.4 million, which expire beginning in 2023. The NOL carry forwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carry forwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, as well as similar state tax provisions. This could limit the amount of NOLs that we can utilize annually to offset future taxable income or tax liabilities. The amount of the annual limitation, if any, will be determined based on the value of our company immediately prior to an ownership change. Subsequent ownership changes may further affect the limitation in future years. In addition, U.S. tax laws limit the time during which these carry forwards may be applied against future taxes, therefore, we may not be able to take full advantage of these carry forwards for federal income tax purposes. We have not evaluated the ownership history of our company to determine if there were any ownership changes as defined under Section 382(g) of the Code and the effects any ownership change may have had. The components of the net deferred tax asset are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Gross deferred tax assets: ​ ​ Net operating loss carryforwards ​ $ 81,719 ​ $ 59,819 Accrued expenses ​ 272 ​ 219 Amortization of intangible ​ ​ 251 ​ ​ — Stock‑based compensation ​ 5,944 ​ 4,270 Research and development and other credits and other carryforwards ​ 16,216 ​ 11,906 Lease liability ​ ​ 610 ​ ​ 879 Capitalized research and development expenses ​ ​ 11,437 ​ ​ 15,891 Unrealized income ​ ​ — ​ ​ 12 Other ​ ​ 9 ​ ​ 4 Total gross deferred tax assets ​ $ 116,458 ​ $ 93,000 Gross deferred tax liabilities: ​ ​ ​ ​ ​ ​ ROU Asset ​ ​ (399) ​ ​ (569) Depreciation ​ ​ (99) ​ ​ (252) Unrealized income ​ (212) ​ — Total gross deferred tax liabilities ​ ​ (710) ​ ​ (821) Net deferred tax assets ​ 115,748 ​ 92,179 Less: valuation allowance ​ (115,748) ​ (92,179) Net deferred tax assets after valuation allowance ​ $ — ​ $ — ​ In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred income tax assets will not be realized. The ultimate realization of deferred income tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred income tax liabilities, projected future taxable income, and tax planning strategies in making this assessment. Based on consideration of these items, management has determined that enough uncertainty exists relative to the realization of the deferred income tax asset balances to warrant the application of a full valuation allowance as of December 31, 2021 and 2020. The valuation allowance increased by $23.6 million and $39.7 million during the years ended December 31, 2021 and 2020, respectively. The increase for the year ended December 31, 2021 was due primarily to our increase in net operating loss carryovers and an increase in tax attributes. The increase for the year ended December 31, 2020 was due primarily to our increase in net operating loss carryovers and an increase in tax attributes. We did not have unrecognized tax benefits as of December 31, 2021 and 2020, and do not expect this to change significantly over the next twelve months. We recognize tax positions in the financial statements only when it is more likely than not that the position will be sustained on examination by the relevant taxing authority based on the technical merits of the position. A position that meets this standard is measured at the largest amount of benefit that will more likely than not be realized on settlement. A liability is established for differences between positions taken in a tax return and amounts recognized in the financial statements. Accrued interest and penalties, where appropriate, are recorded in income tax expense. We did not have uncertain tax positions as of December 31, 2021 and 2020. As of December 31, 2021 and 2020, we had not accrued interest or penalties related to any uncertain tax positions. A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 ​ Federal income tax expense at statutory rate 21.0 % 21.0 % Permanent items (0.7) ​ (0.7) ​ State income tax, net of federal benefit 2.2 ​ 7.6 ​ R&D tax credits 4.3 ​ 4.7 ​ Change in state tax rate ​ (2.8) ​ — ​ Foreign income tax effect ​ — ​ — ​ Capitalized research and development expenses ​ — ​ 26.2 ​ Other ​ — ​ — ​ Change in valuation allowance (24.0) ​ (58.8) ​ Effective income tax rate 0.0 % 0.0 % ​ For all years through December 31, 2021, we generated research and development credits but have not conducted a study to document the qualified activities. This study may result in an adjustment to our research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position for these years. A full valuation allowance has been provided against our research and development credits and, if an adjustment is required, this adjustment to the deferred tax asset established for the research and development credit carryforwards would be offset by an adjustment to the valuation allowance. We file income tax returns in the United States, the State of Connecticut, and the Commonwealth of Pennsylvania. The federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2018 through December 31, 2020. To the extent we have tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation The financial statements include the accounts of Marinus Pharmaceuticals, Inc. (the Company) and its wholly-owned subsidiary as of December 31, 2021. During the year ended December 31, 2020, a wholly-owned subsidiary was liquidated. In February 2021, a new wholly-owned subsidiary was established in Ireland. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from such estimates.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. We view our operations and manage our business in one segment, which is the identification and development of innovative therapeutics to treat rare seizure disorders.
Fair Value of Financial Instruments and Credit Risk	Fair Value of Financial Instruments and Credit Risk At December 31, 2021, our financial instruments included cash equivalents, accounts payable, accrued expenses, and notes payable. At December 31, 2020, our financial instruments included cash equivalents, short-term investments, accounts payable and accrued expenses. The carrying amount of cash equivalents, accounts payable and accrued expenses approximated fair value, given their short-term nature. The carrying amounts of short-term investments are recorded at amortized cost, which for U.S. Treasury securities is based on the current market price of each security at the measurement date. The carrying value of the notes payable approximates fair value as the interest rate is reflective of current market rates on debt with similar terms and conditions. Cash equivalents and certificates of deposit subject us to concentrations of credit risk. However, we invest our cash in accordance with a policy objective that seeks to ensure both liquidity and safety of principal. The policy limits investments to instruments issued by the U.S. government, certain Securities and Exchange Commission (SEC)-registered money market funds that invest only in U.S. government obligations and various other low-risk liquid investment options, and places restrictions on portfolio maturity terms.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. As of December 31, 2021 and 2020, we invested a portion of our cash balances in money market investments, which we have included as cash equivalents on our balance sheets.
Investments	Investments We did not have any investments as of December 31, 2021. As of December 31, 2020, our investments consisted of certificates of deposit with various financial institutions, with original maturities ranging from six to nine months. All investments were classified as held-to-maturity and were recorded at amortized cost. Interest income includes interest and dividends, realized gains and losses on sales of securities, if any.
Accounts Receivable	Accounts Receivable Accounts receivable represents amounts due to us under the BARDA contract for valid expenditures expected to be reimbursed to us under the terms of the BARDA contract and current amounts due to us from Orion Corporation under our collaboration agreement (Note 11).
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets generally represent payments made for goods or services to be received within one year, and are expensed as the related benefit is received.
Property and Equipment	Property and Equipment Property and equipment consist of laboratory and office equipment and are recorded at cost. Property and equipment are depreciated on a straight-line basis over their estimated useful lives. We estimate a life of three years for computer equipment, including software, five years for office equipment and furniture, five to fifteen years for laboratory equipment, and six years for leasehold improvements. When property and equipment are sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss is included in operating expenses.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. If the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount an impairment loss would be recognized if the carrying value of the asset exceeded its fair value. Fair value is generally determined using discounted cash flows.
Income Taxes	Income Taxes a full valuation allowance is necessary for our net deferred tax assets. We had no material amounts recorded for uncertain tax positions, interest or penalties in the accompanying financial statements.
Debt Issuance Costs	Debt Issuance Costs
Contract Liability	Contract Liability
Federal Contract Revenue	Federal Contract Revenue We recognize federal contract revenue from the BARDA Contract in the period in which the allowable research and development expenses are incurred, and receivables associated with this revenue are included within accounts receivable on our balance sheets. This revenue is not within the scope of Accounting Standards Codification (ASC) 606 – Revenue from contracts with customers.
Collaboration and Licensing Revenue	Collaboration and Licensing Revenue We must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price may include such estimates as forecasted revenues and costs, development timelines, discount rates and probabilities of regulatory and commercial success. We also apply significant judgment when evaluating whether contractual obligations represent distinct performance obligations, allocating transaction price to performance obligations within a contract, determining when performance obligations have been met, assessing the recognition and future reversal of variable consideration and determining and applying appropriate methods of measuring progress for performance obligations satisfied over time.
Research and Development	Research and Development Research and development costs are expensed as incurred. Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as subject enrollment, monitoring visits, clinical site activations, or information provided to us by our vendors with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development expense, as the case may be.
Clinical Trial Expenses	Clinical Trial Expenses As part of the process of preparing our financial statements, we are required to estimate our expenses resulting from our obligations under contracts with vendors, clinical research organizations and consultants and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. Our objective is to reflect the appropriate trial expenses in our financial statements by matching those expenses with the period in which services are performed and efforts are expended. We account for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. We determine accrual estimates based on estimates of services received and efforts expended that take into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials. During the course of a clinical trial, we adjust our clinical expense recognition if actual results differ from its estimates. We make estimates of our accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. Our clinical trial accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2021 and 2020 there were no material adjustments to our prior period estimates of accrued expenses for clinical trials.
Stock-Based Compensation	Stock-Based Compensation We account for stock-based compensation in accordance with the provisions of Accounting Standards Codification (ASC) Topic 718, Compensation—Stock Compensation
Loss Per Share of Common Stock	Loss Per Share of Common Stock Basic loss per share is computed by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, and unvested restricted stock, which would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share applicable to common stockholders, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation. These potentially dilutive securities are more fully described in Note 8. The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31, 2021 and 2020 (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 ​ Basic and diluted net loss per share of common stock: ​ ​ ​ Net loss ​ $ (98,776) ​ $ (67,475) ​ Deemed Dividends ​ ​ — ​ ​ (8,880) ​ Net loss applicable to common stockholders ​ $ (98,776) ​ $ (76,355) ​ Weighted average shares of common stock outstanding ​ 36,697,171 ​ 27,270,055 ​ Net loss per share of common stock—basic and diluted ​ $ (2.69) ​ $ (2.80) ​ ​ The following potentially dilutive securities (common stock equivalents) have been excluded from the computation of diluted weighted average shares outstanding, as they would be antidilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 ​ Convertible preferred stock 915,000 950,600 Restricted stock 26,025 24,625 Stock options 4,738,855 3,507,638 Total 5,679,880 4,482,863 ​ The convertible preferred stock meets the definition of a participating security; however, the holders are not obligated to share in our losses. As of December 31, 2021 and 2020, we had no other potentially dilutive securities.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Schedule of computation of basic and diluted earnings per share	The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31, 2021 and 2020 (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 ​ Basic and diluted net loss per share of common stock: ​ ​ ​ Net loss ​ $ (98,776) ​ $ (67,475) ​ Deemed Dividends ​ ​ — ​ ​ (8,880) ​ Net loss applicable to common stockholders ​ $ (98,776) ​ $ (76,355) ​ Weighted average shares of common stock outstanding ​ 36,697,171 ​ 27,270,055 ​ Net loss per share of common stock—basic and diluted ​ $ (2.69) ​ $ (2.80) ​
Schedule of antidilutive securities excluded from the computation of diluted weighted average shares outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 ​ Convertible preferred stock 915,000 950,600 Restricted stock 26,025 24,625 Stock options 4,738,855 3,507,638 Total 5,679,880 4,482,863

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Measurements
Summary of major categories of financial assets and liabilities measured at fair value on a recurring basis	The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total December 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 2,360 ​ $ — ​ $ — ​ $ 2,360 ​ Money market funds (cash equivalents) ​ ​ 120,567 ​ ​ — ​ ​ — ​ ​ 120,567 ​ Total assets ​ $ 122,927 ​ $ — ​ $ — ​ $ 122,927 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 138,509 ​ $ — ​ $ — ​ $ 138,509 ​ Certificates of deposit ​ ​ 1,474 ​ ​ — ​ ​ — ​ ​ 1,474 ​ Total assets ​ $ 139,983 ​ $ — ​ $ — ​ $ 139,983 ​

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property and Equipment
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2021 ​ 2020 Laboratory equipment $ 2,565 $ 1,777 ​ Leasehold improvements ​ ​ 899 ​ ​ 899 ​ Office furniture and equipment ​ 429 ​ 401 ​ Total property and equipment ​ 3,893 ​ 3,077 ​ Less: accumulated depreciation ​ (1,394) ​ (1,132) ​ Total property and equipment, net ​ $ 2,499 ​ $ 1,945 ​ ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Accrued Expenses
Schedule of accrued expenses	Accrued expenses consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Payroll and related costs ​ $ 5,830 ​ $ 4,097 Clinical trials and drug development ​ ​ 8,217 ​ ​ 2,452 ​ Professional fees ​ ​ 1,311 ​ ​ 927 ​ Short-term lease liabilities ​ ​ 556 ​ ​ 510 ​ Other ​ ​ 293 ​ ​ 532 ​ Total accrued expenses ​ $ 16,207 ​ $ 8,518 ​

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases
Schedule of maturities of operating lease liabilities	Maturities of operating lease liabilities as of December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ $ 807 ​ 2023 ​ 823 ​ 2024 ​ 840 ​ Thereafter ​ 643 ​ ​ ​ ​ 3,113 ​ Less: imputed interest ​ ​ (578) ​ Total lease liabilities ​ $ 2,535 ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 556 ​ Non-current operating lease liabilities ​ ​ 1,979 ​ Total lease liabilities ​ $ 2,535 ​

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Schedule of weighted-average assumptions estimated at the date of grant using the Black-Scholes option pricing model	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 ​ Expected stock price volatility 115 - 124 % 116 - 122 % ​ Expected term of options 5.0 - 6.1 years 5.3 - 6.1 years ​ Risk‑free interest rate 0.44 - 1.33 % 0.31 - 1.73 % ​ Expected annual dividend yield ​ ​ 0 % ​ ​ 0 % ​
Schedule of unrecognized compensation expense expected to be recognized in future years	​ ​ ​ ​ ​ 2022 $ 9,716 2023 ​ 7,315 2024 ​ 3,186 2025 ​ 768 ​ ​ $ 20,985
Stock option
Schedule of total compensation cost recognized in the statement of operations	Total compensation cost recognized for all stock option awards in the statements of operations is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2021 ​ 2020 ​ Research and development $ 4,482 $ 2,938 General and administrative ​ 9,106 ​ 4,521 ​ Total ​ $ 13,588 ​ $ 7,459 ​
Summary of activity for all options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Exercise Price ​ Intrinsic ​ ​ Shares ​ Per Share ​ Value Outstanding—December 31, 2019 2,135,070 ​ $ 15.80 ​ ​ ​ ​ Granted 1,905,850 ​ 9.17 ​ ​ ​ ​ Exercised ​ (198,475) ​ 5.16 ​ ​ ​ ​ Forfeited ​ (180,107) ​ ​ 11.04 ​ ​ ​ ​ Expired ​ (154,700) ​ ​ 25.16 ​ ​ ​ ​ Outstanding—December 31, 2020 3,507,638 ​ $ 12.64 ​ ​ ​ ​ Granted 1,868,066 ​ 13.49 ​ ​ ​ ​ Exercised (176,194) ​ 6.80 ​ ​ ​ ​ Forfeited ​ (225,726) ​ ​ 11.85 ​ ​ ​ ​ Expired ​ (234,929) ​ ​ 32.81 ​ ​ ​ ​ Outstanding—December 31, 2021 4,738,855 ​ $ 12.23 ​ $ 9,531 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable—December 31, 2021 2,450,061 ​ $ 12.56 ​ $ 6,521 ​
Restricted stock
Schedule of total compensation cost recognized in the statement of operations	Total compensation cost recognized for all restricted stock awards in the statements of operations for the years ended December 31, 2021 and 2020 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Research and development $ 3 $ — General and administrative ​ 276 ​ 183 Total ​ $ 279 ​ $ 183
Summary of activity for all restricted stock	A summary of activity for the years ended December 31, 2021 and 2020 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ‑ average ​ ​ ​ ​ Grant Date ​ ​ Shares ​ Fair Value per Share Outstanding—December 31, 2019 8,100 ​ $ 4.84 Granted 34,000 ​ ​ 12.93 Vested (17,475) ​ ​ 10.04 Outstanding—December 31, 2020 ​ 24,625 ​ ​ 11.41 Granted ​ 18,400 ​ ​ 13.48 Vested ​ (17,000) ​ ​ 12.93 Outstanding—December 31, 2021 26,025 ​ $ 12.75 ​ ​ ​ ​ ​ ​ Expected to vest—December 31, 2021 26,025 ​ $ 12.75

Notes Payable (Tables)

Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2021
Notes Payable
Summary of composition of Notes payable	The following table summarizes the composition of Notes payable as reflected on the consolidated balance sheet as of December 31, 2021 (in thousands): ​ ​ ​ ​ Gross proceeds ​ $ 45,000 Contractual exit fee ​ 900 Unamortized debt discount and issuance costs ​ (5,091) Total ​ $ 40,809
Schedule of maturities of Notes payable over the next five years	The aggregate maturities of Notes payable as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ 2022 ​ $ — 2023 ​ ​ — 2024 ​ ​ 6,825 2025 and thereafter ​ ​ 38,175 Total ​ $ 45,000

License and Collaboration Rev_2

License and Collaboration Revenue (Tables)	12 Months Ended
	Dec. 31, 2021
License and Collaboration Revenue
Schedule of allocation of the transaction price to the performance obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative ​ ​ ​ Transaction ​ Collaboration ​ Contract ​ Price Recognized Liability License $ 8,987 ​ $ 8,987 ​ $ - Development and Regulatory Services ​ 2,787 ​ ​ 106 ​ ​ 2,681 Supply of License Product ​ 3,943 ​ ​ - ​ ​ 3,943 Total contract liability $ 15,717 ​ $ 9,093 ​ ​ 6,624 Less current portion of contract liability ​ ​ ​ ​ ​ ​ ​ (869) Total long-term contract liability ​ ​ ​ ​ ​ ​ $ 5,755

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Taxes
Summary of loss before income taxes	Loss before income taxes is allocated as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2021 ​ 2020 ​ ​ U.S. operations ​ $ 98,776 ​ $ 67,475 ​ ​ Foreign operations ​ — ​ — ​ ​ Loss before income taxes ​ $ 98,776 ​ $ 67,475 ​ ​
Schedule of components of the net deferred tax asset	The components of the net deferred tax asset are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Gross deferred tax assets: ​ ​ Net operating loss carryforwards ​ $ 81,719 ​ $ 59,819 Accrued expenses ​ 272 ​ 219 Amortization of intangible ​ ​ 251 ​ ​ — Stock‑based compensation ​ 5,944 ​ 4,270 Research and development and other credits and other carryforwards ​ 16,216 ​ 11,906 Lease liability ​ ​ 610 ​ ​ 879 Capitalized research and development expenses ​ ​ 11,437 ​ ​ 15,891 Unrealized income ​ ​ — ​ ​ 12 Other ​ ​ 9 ​ ​ 4 Total gross deferred tax assets ​ $ 116,458 ​ $ 93,000 Gross deferred tax liabilities: ​ ​ ​ ​ ​ ​ ROU Asset ​ ​ (399) ​ ​ (569) Depreciation ​ ​ (99) ​ ​ (252) Unrealized income ​ (212) ​ — Total gross deferred tax liabilities ​ ​ (710) ​ ​ (821) Net deferred tax assets ​ 115,748 ​ 92,179 Less: valuation allowance ​ (115,748) ​ (92,179) Net deferred tax assets after valuation allowance ​ $ — ​ $ — ​
Schedule of reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 ​ Federal income tax expense at statutory rate 21.0 % 21.0 % Permanent items (0.7) ​ (0.7) ​ State income tax, net of federal benefit 2.2 ​ 7.6 ​ R&D tax credits 4.3 ​ 4.7 ​ Change in state tax rate ​ (2.8) ​ — ​ Foreign income tax effect ​ — ​ — ​ Capitalized research and development expenses ​ — ​ 26.2 ​ Other ​ — ​ — ​ Change in valuation allowance (24.0) ​ (58.8) ​ Effective income tax rate 0.0 % 0.0 %

Organization and Description _2

Organization and Description of the Business (Details) $ in Thousands, € in Millions	Jul. 30, 2021USD ($)	Jul. 30, 2021EUR (€)	May 11, 2021USD ($)tranche	Sep. 23, 2020shares	Dec. 31, 2020USD ($)shares	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)shares	Dec. 31, 2021USD ($)shares	Dec. 31, 2021EUR (€)	Dec. 31, 2020USD ($)shares	Dec. 31, 2021EUR (€)shares
Liquidity
Net loss								$ 98,776		$ 67,475
Accumulated deficit					$ 311,929			410,705		$ 311,929
Refundable portion of upfront payment								$ 21,233
Reverse stock split ratio				0.25
Common stock, shares authorized | shares				150,000,000	150,000,000			150,000,000		150,000,000	150,000,000
Oaktree Capital Management LP Credit Agreement
Liquidity
Term of loan facility			5 years
Maximum borrowing capacity available under the credit agreement			$ 125,000
Number of tranches | tranche			5
Additional borrowing capacity available, subject to certain milestone events			$ 80,000
Oaktree Capital Management LP Credit Agreement | Funding of the tranche A- 2 term loans until the funding of the tranche B term loans
Liquidity
Minimum liquidity to be maintained			20,000					$ 20,000
BARDA Contract
Liquidity
Maximum amount to be awarded under the contract						$ 51,000
Contract base period						2 years
Amount of funding to be provided during contract base period						$ 21,000
Amount of additional funding to be provided following successful completion of clinical trial and preclinical studies in base period						30,000
Cost sharing, amount						33,000
Cost sharing, BARDA amount						$ 51,000
Contract period-of-performance						5 years
Collaboration Agreement with Orion
Liquidity
Upfront fee received	$ 29,600	€ 25							€ 25
R&D reimbursement and cash milestone payments to be received | €		€ 97
Number of days from receipt of the final report, in which the collaboration agreement may be terminated	90 days	90 days
Percentage of upfront fee which must be refunded in the event of termination		75.00%
Refundable portion of upfront payment								21,200			€ 18.8
Term Loan Tranche B | Oaktree Capital Management LP Credit Agreement
Liquidity
Additional borrowing capacity available, subject to certain milestone events			$ 30,000					$ 30,000
Common Stock | Public Offering.
Liquidity
Issuance of common stock (in shares) | shares					5,000,000		4,600,000
Proceeds from equity offerings, net of offering costs					$ 64,800		$ 43,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Segment Information (Details)	12 Months Ended
	Dec. 31, 2021segment
Segment Information
Number of operating segments	1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2021
Computer equipment, including software
Property and Equipment
Useful life	3 years
Office equipment and furniture
Property and Equipment
Useful life	5 years
Leasehold improvements
Property and Equipment
Useful life	6 years
Minimum | Laboratory equipment
Property and Equipment
Useful life	5 years
Maximum | Laboratory equipment
Property and Equipment
Useful life	15 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Loss Per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Basic and diluted net loss per share of common stock:
Net loss	$ (98,776)	$ (67,475)
Deemed Dividends		(8,880)
Net loss applicable to common shareholders	$ (98,776)	$ (76,355)
Weighted average shares of common stock outstanding - Basic (in shares)	36,697,171	27,270,055
Weighted average shares of common stock outstanding - Diluted (in shares)	36,663,340	27,270,055
Net loss per share of common stock-basic	$ (2.69)	$ (2.80)
Net loss per share of common stock-diluted	$ (2.69)	$ (2.80)
Antidilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	5,679,880	4,482,863
Convertible preferred stock
Basic and diluted net loss per share of common stock:
Antidilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	915,000	950,600
Restricted stock
Basic and diluted net loss per share of common stock:
Antidilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	26,025	24,625
Stock option
Basic and diluted net loss per share of common stock:
Antidilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	4,738,855	3,507,638

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets
Total assets	$ 122,927	$ 139,983
Cash
Assets
Cash and cash equivalents, fair value	2,360
Money market funds
Assets
Cash and cash equivalents, fair value	120,567	138,509
Certificates of deposit
Assets
Investments		1,474
Level 1
Assets
Total assets	122,927	139,983
Level 1 | Cash
Assets
Cash and cash equivalents, fair value	2,360
Level 1 | Money market funds
Assets
Cash and cash equivalents, fair value	$ 120,567	138,509
Level 1 | Certificates of deposit
Assets
Investments		$ 1,474

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property and equipment
Property and equipment, gross	$ 3,893	$ 3,077
Less: accumulated depreciation	(1,394)	(1,132)
Total property and equipment, net	2,499	1,945
Depreciation expense	300	300
Other income (expense)
Property and equipment
Equipment held for sale	200
Laboratory equipment
Property and equipment
Property and equipment, gross	2,565	1,777
Leasehold improvements
Property and equipment
Property and equipment, gross	899	899
Office equipment
Property and equipment
Property and equipment, gross	$ 429	$ 401

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Expenses
Payroll and related costs	$ 5,830	$ 4,097
Clinical trials and drug development	8,217	2,452
Professional fees	1,311	927
Short-term lease liabilities	556	510
Other	293	532
Total accrued expenses	$ 16,207	$ 8,518

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases
Operating lease agreement term	78 months
Operating lease renewal term	60 months
Weighted average remaining lease term	45 months
Right-of-use assets	$ 1,700	$ 2,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent	Other Assets, Noncurrent
Operating lease liabilities	$ 2,535	$ 3,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Accrued Liabilities, Current, Other Accrued Liabilities, Noncurrent	Accrued Liabilities, Current, Other Accrued Liabilities, Noncurrent
Total lease costs	$ 600	$ 600
Short-term operating lease costs	$ 100
Weighted-average incremental borrowing rate used to determine right-of-use assets and lease liabilities	11.00%
Impairment losses of ROU assets	$ 0	0
Maturities of operating lease liabilities
2022	807
2023	823
2024	840
Thereafter	643
Total lease payments	3,113
Less: imputed interest	(578)
Total lease liabilities	2,535	$ 3,000
Current operating lease liabilities	556
Non-current operating lease liabilities	$ 1,979

Stockholders' Equity - Incentiv

Stockholders' Equity - Incentive Plans (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2022	Dec. 31, 2019
Stock option
Stock option and incentive plans
Granted (in shares)	1,868,066	1,905,850
Outstanding (in shares)	4,738,855	3,507,638		2,135,070
Restricted stock
Stock option and incentive plans
Outstanding (in shares)	26,025	24,625		8,100
2005 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)	0
2005 Plan | Stock option
Stock option and incentive plans
Outstanding (in shares)	577
2014 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)	1,012,869		2,521,079
2014 Plan | Stock option
Stock option and incentive plans
Outstanding (in shares)	3,268,048
2014 Plan | Restricted stock
Stock option and incentive plans
Outstanding (in shares)		26,025
Outside of 2014 Plan | Stock option
Stock option and incentive plans
Granted (in shares)	772,117	852,024

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options and Restricted Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stock option and incentive plans
Total compensation cost	$ 13,588	$ 7,459
Stock option
Stock Options
Outstanding at the beginning of the period (in shares)	3,507,638	2,135,070
Granted (in shares)	1,868,066	1,905,850
Exercised (in shares)	(176,194)	(198,475)
Forfeited (in shares)	(225,726)	(180,107)
Expired (in shares)	(234,929)	(154,700)
Outstanding at the end of the period (in shares)	4,738,855	3,507,638
Exercisable at the end of the period (in shares)	2,450,061
Weighted-Average Exercise Price Per Share
Outstanding at the beginning of the period (in dollars per share)	$ 12.64	$ 15.80
Granted (in dollars per share)	13.49	9.17
Exercised (in dollars per share)	6.80	5.16
Forfeited (in dollars per share)	11.85	11.04
Expired (in dollars per share)	32.81	25.16
Outstanding at the end of the period (in dollars per share)	12.23	12.64
Exercisable at the end of the period (in dollars per share)	$ 12.56
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 9,531
Exercisable at the end of the period	$ 6,521
Additional Disclosures
Weighted average remaining contractual term	8 years 2 months 12 days
Weighted average remaining contractual term exercisable	7 years 7 months 6 days
Market value per share	$ 11.88
Weighted average grant date fair value (in dollars per share)	$ 11.54	$ 7.81
Weighted-average assumptions
Expected annual dividend yield (as a percent)	0.00%	0.00%
Unrecognized compensation expense
Unrecognized compensation expense	$ 20,985
Stock option | Recognition in 2022
Unrecognized compensation expense
Unrecognized compensation expense	9,716
Stock option | Recognition in 2023
Unrecognized compensation expense
Unrecognized compensation expense	7,315
Stock option | Recognition in 2024
Unrecognized compensation expense
Unrecognized compensation expense	3,186
Stock option | Recognition in 2025
Unrecognized compensation expense
Unrecognized compensation expense	$ 768
Stock option | Minimum
Weighted-average assumptions
Expected stock price volatility (as a percent)	115.00%	116.00%
Expected term of options	5 years	5 years 3 months 18 days
Risk-free interest rate (as a percent)	0.44%	0.31%
Stock option | Maximum
Stock option and incentive plans
Vesting period	4 years
Weighted-average assumptions
Expected stock price volatility (as a percent)	124.00%	122.00%
Expected term of options	6 years 1 month 6 days	6 years 1 month 6 days
Risk-free interest rate (as a percent)	1.33%	1.73%
Restricted stock
Stock option and incentive plans
Total compensation cost	$ 279	$ 183
Unrecognized compensation expense
Unrecognized compensation cost	$ 300
Shares
Restricted stock units outstanding at the beginning of the period (in shares)	24,625	8,100
Granted (in shares)	18,400	34,000
Vested (in shares)	(17,000)	(17,475)
Restricted stock units outstanding at the end of the period (in shares	26,025	24,625
Weighted Average Grant Date Fair Value
Restricted stock units outstanding at the beginning of the period (in dollars per shares)	$ 11.41	$ 4.84
Granted (in dollars per share)	13.48	12.93
Vested (in dollars per share)	12.93	10.04
Restricted stock units outstanding at the end of the period (in dollars per shares)	$ 12.75	$ 11.41
Restricted stock | Maximum
Stock option and incentive plans
Vesting period	2 years
2005 Plan | Stock option
Stock Options
Outstanding at the end of the period (in shares)	577
2005 Plan | Stock option | Maximum
Stock option and incentive plans
Contractual life	10 years
2014 Plan | Stock option
Stock Options
Outstanding at the end of the period (in shares)	3,268,048
2014 Plan | Stock option | Maximum
Stock option and incentive plans
Contractual life	10 years
2014 Plan | Restricted stock
Shares
Restricted stock units outstanding at the beginning of the period (in shares)	26,025
Restricted stock units outstanding at the end of the period (in shares		26,025
Research and development. | Restricted stock
Stock option and incentive plans
Total compensation cost	$ 3
Research and development. | 2014 Plan
Stock option and incentive plans
Total compensation cost	4,482	$ 2,938
General and administrative | Restricted stock
Stock option and incentive plans
Total compensation cost	276	183
General and administrative | 2014 Plan
Stock option and incentive plans
Total compensation cost	$ 9,106	$ 4,521

Stockholders' Equity - Equity D

Stockholders' Equity - Equity Distribution Agreement (Details) - USD ($) $ in Millions	Jul. 09, 2020	Oct. 31, 2017	Dec. 31, 2020
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of shares under equity distribution agreement (in shares)			78,807
2017 Equity Distribution Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of Equity Distribution Agreement		3 years
Value of common stock authorized under EDA		$ 50
2017 Equity Distribution Agreement | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of shares under equity distribution agreement (in shares)			78,807
Net proceeds from issuance of common stock			$ 0.5
2020 Equity Distribution Agreement | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock an aggregate offering price	$ 60
Sale of common stock, commission percentage	3.00%

Stockholders' Equity - Public O

Stockholders' Equity - Public Offering (Details) - Public Offering. - Common Stock - USD ($) $ in Millions	1 Months Ended
	Dec. 31, 2020	Jun. 30, 2020
Public Offering
Shares issued	5,000,000	4,600,000
Proceeds from equity offerings, net of offering costs	$ 64.8	$ 43

Convertible Preferred Stock (De

Convertible Preferred Stock (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2020$ / shares
Common Stock
Convertible Preferred Stock
Conversion of Stock, Shares Issued	35,600
Series A Preferred Stock
Convertible Preferred Stock
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001		$ 0.001
Number of common shares issued for each convertible Series A preferred stock	915,000
Conversion of Stock, Shares Issued	178
Temporary Equity, Shares Outstanding	4,575
Series A Preferred Stock | Common Stock
Convertible Preferred Stock
Number of common shares issued for each convertible Series A preferred stock		200
Conversion price (in dollars per share) | $ / shares		$ 5
Series A Preferred Stock | Minimum
Convertible Preferred Stock
Beneficial interest limitation	9.99
Series A Preferred Stock | Maximum
Convertible Preferred Stock
Beneficial interest limitation	19.99
Private placement | Series A Preferred Stock
Convertible Preferred Stock
Issuance of Series A preferred stock (in shares)		30,000
Series A convertible preferred stock, par value (in dollars per share) | $ / shares		$ 0.001
Share Price (in dollars per share) | $ / shares		$ 1,000
Net proceeds from issuance of Series A convertible preferred stock | $		$ 28.2
Underwriting discounts and commissions | $		$ 1.8
Beneficial conversion feature of the convertible preferred stock | $	$ 8.9

Notes Payable - Narratives (Det

Notes Payable - Narratives (Details) $ in Thousands	May 11, 2021USD ($)tranche	Sep. 30, 2021USD ($)	Dec. 31, 2021USD ($)
Debt Instrument [Line Items]
Contractual exit fee			$ 900
Interest Expense			2,582
Amortization of debt issuance costs			549
Oaktree Capital Management LP Credit Agreement
Debt Instrument [Line Items]
Term of loan facility	5 years
Maximum borrowing capacity available under the credit agreement	$ 125,000
Number of tranches | tranche	5
Additional borrowing capacity available, subject to certain milestone events	$ 80,000
Proceeds from line of credit	$ 15,000	$ 30,000
Accrued interest rate (as a percent)	11.50%
Percentage of periodic principal payment	5.00%
Upfront fee (as a percent)	2.00%
Commitment fees	0.75%
Commitment fee accrual period	120 days
Percentage of term loan exit fees	2.00%
Debt issuance costs	$ 4,400	1,200
Contractual exit fee	300	$ 600
Interest Expense			2,600
Interest on term loan			2,000
Amortization of debt issuance costs			600
Oaktree Capital Management LP Credit Agreement | Funding of the tranche A- 2 term loans until the funding of the tranche B term loans
Debt Instrument [Line Items]
Minimum liquidity to be maintained	20,000		20,000
Oaktree Capital Management LP Credit Agreement | Funding date of the tranche B term loans until the maturity of the Term Loans
Debt Instrument [Line Items]
Minimum liquidity to be maintained	$ 15,000
Oaktree Capital Management LP Credit Agreement | Scenario Of Prepayment On Or Before May 11, 2023
Debt Instrument [Line Items]
Prepayment premium (as a percent)	4.00%
Oaktree Capital Management LP Credit Agreement | Scenario Of Prepayment Occurs Between May 11, 2023 To May 11, 2024
Debt Instrument [Line Items]
Prepayment premium (as a percent)	4.00%
Oaktree Capital Management LP Credit Agreement | Scenario Of Prepayment Between May 11, 2024 To May 11, 2025
Debt Instrument [Line Items]
Prepayment premium (as a percent)	2.00%
Oaktree Capital Management LP Credit Agreement | Scenario Of Prepayment After May 11, 2025
Debt Instrument [Line Items]
Prepayment premium (as a percent)	0.00%
Oaktree Capital Management LP Credit Agreement | Prepayment occurs on or before May 11, 2022
Debt Instrument [Line Items]
Prepayment premium (as a percent)	12.50%
Oaktree Capital Management LP Credit Agreement | Prepayment occurs after May 11, 2022 but on or before May 11, 2023
Debt Instrument [Line Items]
Prepayment premium (as a percent)	10.00%
Oaktree Capital Management LP Credit Agreement | Term Loans Tranche A-1
Debt Instrument [Line Items]
Proceeds from line of credit	$ 15,000
Oaktree Capital Management LP Credit Agreement | Term Loans Tranche A-2
Debt Instrument [Line Items]
Proceeds from line of credit	30,000
Oaktree Capital Management LP Credit Agreement | Term Loan Tranche B
Debt Instrument [Line Items]
Additional borrowing capacity available, subject to certain milestone events	30,000		$ 30,000
Oaktree Capital Management LP Credit Agreement | Term Loan Tranche C
Debt Instrument [Line Items]
Additional borrowing capacity available, subject to certain milestone events	25,000
Gross proceeds from sublicense, minimum	40,000
Net proceeds from sublicense, minimum	36,000
Oaktree Capital Management LP Credit Agreement | Term Loan Tranche D
Debt Instrument [Line Items]
Additional borrowing capacity available, subject to certain milestone events	25,000
Net product revenue, minimum	$ 50,000
Net product revenue, consecutive earning period	6 months

Notes Payable - Composition of

Notes Payable - Composition of debt (Details) $ in Thousands	Dec. 31, 2021USD ($)
Notes Payable
Gross proceeds	$ 45,000
Contractual exit fee	900
Unamortized debt discount and issuance costs	(5,091)
Total	$ 40,809

Notes Payable - Debt maturities

Notes Payable - Debt maturities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Notes Payable
2024	$ 6,825
2025 and thereafter	38,175
Total	$ 45,000

License and Collaboration Rev_3

License and Collaboration Revenue - Narrative (Details) $ in Thousands, € in Millions	Jul. 30, 2021USD ($)	Jul. 30, 2021EUR (€)	Dec. 31, 2021EUR (€)	Dec. 31, 2021USD ($)	Dec. 31, 2021EUR (€)
License and Collaboration Revenue
Refundable portion of upfront payment | $				$ 21,233
Collaboration Agreement with Orion
License and Collaboration Revenue
Upfront fee received	$ 29,600	€ 25	€ 25
Number of days from receipt of the final report, in which the collaboration agreement may be terminated	90 days	90 days
Percentage of upfront fee which must be refunded in the event of termination		75.00%
Amount of payment receivable upon achievement of specific clinical and commercial achievements | €		€ 97
Term of collaboration agreement	10 years	10 years
Refundable portion of upfront payment				$ 21,200	€ 18.8

License and Collaboration Rev_4

License and Collaboration Revenue - Allocation of the transaction price to the performance obligations (Details) $ in Thousands, € in Millions	Jul. 30, 2021USD ($)item	Jul. 30, 2021EUR (€)item	Dec. 31, 2021USD ($)	Dec. 31, 2021EUR (€)
License and Collaboration Revenue
Net contract asset			$ 557
Cost of collaboration revenue			1,478
Collaboration Agreement with Orion
License and Collaboration Revenue
Number of performance obligations | item	3	3
Transaction Price			15,717
Cumulative Collaboration Recognized			9,093
Contract Liability			6,624
Less current portion of contract liability			(869)
Total long-term contract liability			5,755
Contract asset			7,200
Net contract asset			600
Incremental costs incurred in obtaining the agreement			2,000
Contract acquisition costs included in general and administrative expense			1,100
Capitalized contract costs			900
Cost of collaboration revenue			1,500
Upfront fee received	$ 29,600	€ 25		€ 25
Collaboration Agreement with Orion | License Revenue
License and Collaboration Revenue
Transaction Price			8,987
Cumulative Collaboration Recognized			8,987
Collaboration Agreement with Orion | Development and Regulatory Services
License and Collaboration Revenue
Transaction Price			2,787
Cumulative Collaboration Recognized			106
Contract Liability			2,681
Collaboration Agreement with Orion | Supply of License Product
License and Collaboration Revenue
Transaction Price			3,943
Contract Liability			$ 3,943

Commitments and Contingencies -

Commitments and Contingencies - Employee Benefit Plan and License Agreements (Details) - USD ($) $ in Millions	Jan. 01, 2021	Dec. 31, 2021
Employee Benefit Plan
Percentage of contribution	3.00%
Amount of contribution		$ 0.7
Vesting period		4 years
License Agreement | Purdue
License agreement
Expiration period of obligation to pay royalties		10 years

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Loss before income taxes
U.S. operations	$ 98,776	$ 67,475
Loss before income taxes	98,776	67,475
Gross deferred tax assets:
Net operating loss carryforwards	81,719	59,819
Accrued expenses	272	219
Amortization of intangibles	251
Stock-based compensation	5,944	4,270
Research and development and other credits and other carryforwards	16,216	11,906
Lease Liability	610	879
Capitalized research and development expenses	11,437	15,891
Unrealized income		12
Other	9	4
Total gross deferred tax assets	116,458	93,000
Gross deferred tax liabilities:
ROU Asset	(399)	(569)
Depreciation	(99)	(252)
Unrealized income	(212)
Total gross deferred tax liabilities	(710)	(821)
Net deferred tax assets	115,748	92,179
Less: valuation allowance	(115,748)	(92,179)
Increase (decrease) in valuation allowance	23,600	39,700
Unrecognized tax benefit	0	0
Liability for uncertain tax positions	0	0
Interest and penalties accrued related to unrecognized tax benefits	$ 0	$ 0
Reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes
Federal income tax expense at statutory rate (as a percent)	21.00%	21.00%
Permanent items (as a percent)	(0.70%)	(0.70%)
State income tax, net of federal benefit (as a percent)	2.20%	7.60%
R&D tax credits (as a percent)	4.30%	4.70%
Change in state tax rate (as a percent)	(2.80%)
Capitalized research and development expenses (as a percent)		26.20%
Change in valuation allowance (as a percent)	(24.00%)	(58.80%)
Effective income tax rate (as a percent)	0.00%	0.00%
Federal
Loss before income taxes
Net operating loss carry forwards available to offset future federal and state taxable income	$ 303,300	$ 212,000
Net operating loss carry forwards subject to expiration	128,100
State
Loss before income taxes
Net operating loss carry forwards available to offset future federal and state taxable income	253,000	$ 209,500
Research and development | Federal
Loss before income taxes
Tax credit carryovers	15,800
Research and development | State
Loss before income taxes
Tax credit carryovers	$ 400