Ocular Therapeutix (OCUL) 10-K 11 Mar 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Mar. 06, 2024	Jun. 30, 2023
Document And Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-36554
Entity Registrant Name	Ocular Therapeutix, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-5560161
Entity Address, Address Line One	15 Crosby Drive
Entity Address, City or Town	Bedford
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01730
City Area Code	781
Local Phone Number	357-4000
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	OCUL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Public Float			$ 405.7
Entity Common Stock, Shares Outstanding		148,627,439
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	238
Auditor Location	Boston, Massachusetts
Entity Central Index Key	0001393434
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 195,807	$ 102,300
Accounts receivable, net	26,179	21,325
Inventory	2,305	1,974
Restricted cash	150
Prepaid expenses and other current assets	7,794	4,028
Total current assets	232,235	129,627
Property and equipment, net	11,739	9,856
Restricted cash	1,614	1,764
Operating lease assets	6,472	8,042
Total assets	252,060	149,289
Current liabilities:
Accounts payable	4,389	5,123
Accrued expenses and other current liabilities	28,666	24,097
Deferred revenue	255	576
Operating lease liabilities	1,586	1,599
Total current liabilities	34,896	31,395
Other liabilities:
Operating lease liabilities, net of current portion	6,878	8,678
Derivative liabilities	29,987	6,351
Deferred revenue, net of current portion	14,135	13,387
Notes payable, net	65,787	25,257
Other non-current liabilities	108	93
Convertible Notes, net	9,138	28,749
Total liabilities	160,929	113,910
Commitments and contingencies (Note 17)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized and no shares issued or outstanding at December 31, 2023 and December 31, 2022, respectively
Common stock, $0.0001 par value; 200,000,000 shares authorized and 114,963,193 and 77,201,819 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	12	8
Additional paid-in capital	788,697	652,213
Accumulated deficit	(697,578)	(616,842)
Total stockholders' equity	91,131	35,379
Total liabilities and stockholders' equity	$ 252,060	$ 149,289

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	114,963,193	77,201,819
Common stock, shares outstanding	114,963,193	77,201,819

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue:
Total revenue, net	$ 58,443	$ 51,494	$ 43,522
Costs and operating expenses:
Cost, Product and Service [Extensible List]	Product revenue, net	Product revenue, net	Product revenue, net
Cost of product revenue	$ 5,281	$ 4,540	$ 4,406
Research and development	61,055	53,462	50,083
Selling and marketing	40,549	39,922	35,190
General and administrative	33,940	32,224	31,880
Total costs and operating expenses	140,825	130,148	121,559
Loss from operations	(82,382)	(78,654)	(78,037)
Other income (expense):
Interest income	3,983	798	33
Interest expense	(11,338)	(7,022)	(6,671)
Change in fair value of derivative liabilities	(5,188)	13,841	78,121
Gains and losses on extinguishment of debt, net	14,190
Other income (expense), net	(1)	(1)	1
Total other income, net	1,646	7,616	71,484
Net loss	$ (80,736)	$ (71,038)	$ (6,553)
Net loss per share, basic (in dollars per share)	$ (1.01)	$ (0.92)	$ (0.09)
Weighted average common shares outstanding, basic (in shares)	79,827,362	76,875,035	76,392,870
Net loss per share, diluted (in dollars per share)	$ (1.02)	$ (0.97)	$ (0.98)
Weighted average common shares outstanding, diluted (in shares)	85,596,594	82,644,267	82,162,102
Product revenue, net
Revenue:
Total revenue, net	$ 57,870	$ 50,457	$ 43,522
Collaboration revenue
Revenue:
Total revenue, net	$ 573	$ 1,037

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2020	$ 8	$ 615,338	$ (539,251)	$ 76,095
Balance, shares at Dec. 31, 2020	75,996,732
Stockholders' Equity (Deficit)
Issuance of common stock upon exercise of stock options		2,586		2,586
Issuance of common stock upon exercise of stock options, shares	598,923
Issuance of common stock in connection with employee stock purchase plan		985		985
Issuance of common stock in connection with employee stock purchase plan, shares	124,548
Issuance of common stock upon cashless exercise of warrant, shares	11,737
Common stock issuance costs		(91)		(91)
Stock-based compensation expense		14,977		14,977
Net loss attributable to common stockholders			(6,553)	(6,553)
Balance at Dec. 31, 2021	$ 8	633,795	(545,804)	87,999
Balance, shares at Dec. 31, 2021	76,731,940
Stockholders' Equity (Deficit)
Issuance of common stock upon exercise of stock options		514		514
Issuance of common stock upon exercise of stock options, shares	137,502
Issuance of common stock in connection with employee stock purchase plan		940		940
Issuance of common stock in connection with employee stock purchase plan, shares	332,377
Stock-based compensation expense		16,964		16,964
Net loss attributable to common stockholders			(71,038)	(71,038)
Balance at Dec. 31, 2022	$ 8	652,213	(616,842)	35,379
Balance, shares at Dec. 31, 2022	77,201,819
Stockholders' Equity (Deficit)
Issuance of common stock upon exercise of stock options		551		$ 551
Issuance of common stock upon exercise of stock options, shares	141,952			141,952
Issuance of common stock in connection with employee stock purchase plan		851		$ 851
Issuance of common stock in connection with employee stock purchase plan, shares	290,691
Issuance of common stock upon vesting of restricted stock units (in shares)	393,805
Issuance of common stock upon public offering, net of issuance costs	$ 4	117,257		117,261
Issuance of common stock upon public offering, net of issuance costs, shares	36,934,926
Stock-based compensation expense		17,825		17,825
Net loss attributable to common stockholders			(80,736)	(80,736)
Balance at Dec. 31, 2023	$ 12	$ 788,697	$ (697,578)	$ 91,131
Balance, shares at Dec. 31, 2023	114,963,193

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (80,736)	$ (71,038)	$ (6,553)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	17,825	16,964	14,977
Non-cash interest expense	6,106	4,853	4,628
Change in fair value of derivative liabilities	5,188	(13,841)	(78,121)
Depreciation and amortization expense	2,983	2,109	2,421
Gains and losses on extinguishment of debt, net	(14,190)
Gain (loss) on disposal of property and equipment	1	1	(1)
Changes in operating assets and liabilities:
Accounts receivable	(4,854)	(190)	(8,883)
Prepaid expenses and other current assets	(3,766)	723	(101)
Inventory	(331)	(724)	(49)
Accounts payable	583	(621)	1,796
Operating lease assets	1,570	(3,175)	977
Accrued expenses	773	1,644	3,717
Deferred revenue	427	963	1,000
Operating lease liabilities	(1,813)	2,729	(1,358)
Net cash used in operating activities	(70,234)	(59,603)	(65,550)
Cash flows from investing activities:
Purchases of property and equipment	(6,087)	(3,715)	(1,194)
Net cash used in investing activities	(6,087)	(3,715)	(1,194)
Cash flows from financing activities:
Proceeds from issuance of short-term bridge loan	2,000
Proceeds from issuance of Barings notes payable	82,474
Proceeds from issuance of notes payable, net			3,722
Proceeds from exercise of stock options	551	514	2,586
Proceeds from issuance of common stock pursuant to employee stock purchase plan	851	940	985
Payments of debt financing costs	(5,184)
Proceeds from issuance of common stock upon public offering, net of issuance costs	117,261
Issuance costs from the issuance of common stock upon public offering in prior period			(275)
Repayment of MidCap notes payable	(26,125)
Repayment of notes payable			(4,167)
Repayment of short-term bridge loan	(2,000)
Net cash provided by financing activities	169,828	1,454	2,851
Net increase (decrease) in cash, cash equivalents and restricted cash	93,507	(61,864)	(63,893)
Cash, cash equivalents and restricted cash at beginning of period	104,064	165,928	229,821
Cash, cash equivalents and restricted cash at end of period	197,571	104,064	165,928
Supplemental disclosure of cash flow information:
Cash paid for interest	5,464	2,147	1,932
Supplemental disclosure of non-cash investing and financing activities:
Additions to property and equipment included in accounts payable and accrued expenses	$ 16	$ 1,384	$ 181

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2023
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation ​ Ocular Therapeutix, Inc. (the “Company”) was incorporated on September 12, 2006 under the laws of the State of Delaware. The Company is a biopharmaceutical company committed to enhancing people’s vision and quality of life through the development and commercialization of innovative therapies for diseases and conditions of the eye, with a specific focus on retinal disease. The Company’s program for retinal disease is led by AXPAXLI (axitinib intravitreal implant, also known as OTX-TKI), which is based on its ELUTYX proprietary bioresorbable hydrogel-based formulation technology. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations, regulatory approval and compliance, reimbursement, uncertainty of market acceptance of products and the need to obtain additional financing. Recently approved products will require significant sales, marketing and distribution support up to and including upon their launch. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. The Company is currently commercializing DEXTENZA (dexamethasone insert) 0.4mg, an intracanalicular insert for the treatment of post-surgical ocular inflammation and pain and for the treatment of ocular itching associated with allergic conjunctivitis, in the United States. The Company’s most advanced product candidate, AXPAXLI, formerly referred to as OTX-TKI, is in Phase 3 clinical development; the Company’s other advanced product candidates are in either Phase 1 or Phase 2 clinical development. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval and adequate reimbursement or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapidly changing technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. The Company may not be able to generate significant revenue from sales of any product for several years, if at all. Accordingly, the Company will need to obtain additional capital to finance its operations. The Company has incurred losses and negative cash flows from operations since its inception, and the Company expects to continue to generate operating losses and negative cash flows from operations in the foreseeable future. As of December 31, 2023, the Company had an accumulated deficit of $697,578. Based on its current operating plan which includes estimates of anticipated cash inflows from product sales and cash outflows from operating expenses and capital expenditures, the Company believes that its existing cash and cash equivalents of $195,807 as of December 31, 2023, plus the cash received from a private placement of the Company’s common stock in February 2024 of $325,000 before deducting placement agent fees and other offering expenses, will enable it to fund its planned operating expenses, debt service obligations and capital expenditures at least through the next 12 months from the issuance date of these consolidated financial statements while the Company observes a minimum liquidity covenant of $20,000 in its credit facility (Note 9). The future viability of the Company beyond that point is dependent on the Company’s ability to generate cash flows from the sale of DEXTENZA and raise additional capital to finance its operations. The Company will need to finance its operations through public or private securities offerings, debt financings, collaborations, strategic alliances, licensing agreements, royalty agreements, or marketing and distribution agreements. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing on terms acceptable to the Company, if at all. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs for product candidates, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies ​ Basis of Presentation and Principles of Consolidation ​ The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). ​ Use of Estimates ​ The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the measurement and recognition of reserves for variable consideration related to product sales, revenue recognition related to a collaboration agreement that contains multiple promises, the fair value of derivatives, stock-based compensation, and realizability of net deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates. ​ Cash Equivalents ​ The Company considers all short-term, highly liquid investments with original maturities of ninety days or less at date of purchase to be cash equivalents. Cash equivalents, which primarily consist of investments in money market funds, are stated at fair value. ​ Revenue Recognition ​ The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606 – Revenue from Contracts with Customers To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies a performance obligation. At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. ​ Product Revenue ​ The Company sells DEXTENZA in the United States primarily to a limited number of specialty distributors (“SDs”) under individually negotiated distribution agreements. These customers then subsequently resell DEXTENZA to physicians, clinics and certain medical centers or hospitals. The Company also sells DEXTENZA directly to a small population of ambulatory surgery centers (“ASCs”) based on individually negotiated direct distribution agreements (the “Direct Customers”). In addition, the Company enters into arrangements with health care providers and payors that provide for government mandated or privately negotiated rebates and chargebacks with respect to the purchase of DEXTENZA. ​ The Company recognizes revenue on product sales when the customer obtains control of the Company's product, which occurs at a point in time (upon delivery to the customer). Product revenues are recorded net of applicable reserves for variable consideration, including discounts and allowances. ​ Transaction Price, including Variable Consideration ​ The amount of variable consideration which is included in the transaction price may be constrained, and is included in the net sales price, only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s original estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. ​ Trade Discounts and Allowances ​ Product Returns The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well as within accrued expenses and other current liabilities, in the accompanying consolidated balance sheets. The Company currently estimates product return reserves using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. ​ Government Chargebacks U.S. U.S. federal government Drug Discount Program Government Rebates ​ Purchaser/Provider Discounts and Rebates — The Company offers rebate payments for which ASCs, hospital out-patient departments and other prescribers qualify by meeting quarterly purchase volumes of DEXTENZA under the Company’s volume-based rebate program. The Company calculates rebate payment amounts due under this program quarterly, based on actual qualifying purchases and applies a contractual discount rate. In the third quarter of 2022, the Company implemented a separate off-invoice discount (“OID”) rebate program whereby end- users receive the discounted price immediately upon purchase, rather than having to wait until the end of the quarter for a rebate payment. The OID amounts are generally determined at the time of resale by SDs or direct sales to ASCs by the Company. The Company generally issues credits for such amounts within a few weeks of the SD’s notification to the Company of the resale. The Company includes the OID on the invoice when it sells to an ASC directly. The calculation of the accrual for all rebates is based on an estimate of claims that the Company expects to receive associated with product that has been recognized as revenue but also remains in the distribution channel inventories at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included as an accrued expenses and other current liabilities for volume-based rebates and as a reduction of accounts receivable for OID rebates. ​ Other Incentives ​ Collaboration Revenue ​ The Company evaluates contracts that contain multiple promises to determine which promises are distinct. Promises are considered to be distinct and therefore, accounted for as separate performance obligations, provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer and (ii) the promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. In assessing whether a promise is distinct, the Company considers factors such as whether: (i) the Company provides a significant service of integrating goods and/or services with other goods and/or services promised in the contract; (ii) one or more of the goods and/or services significantly modifies or customizes, or are significantly modified or customized by one or more of the other goods and/or services promised in the contract; and (iii) the goods and/or services are highly interdependent or highly interrelated. Individual goods or services (or bundles of goods and/or services) that meet both criteria for being distinct are accounted for as separate performance obligations. Promises that are not distinct at contract inception are combined and accounted for as a single performance obligation. Options to acquire additional goods and/or services are evaluated to determine if such option provides a material right to the customer that it would not have received without entering into the contract. If so, the option is accounted for as a separate performance obligation. If not, the option is considered a marketing offer which would be accounted for as a separate contract upon the customer’s election. ​ The Company considers the existence of any significant financing component within its arrangements based on whether a substantive business purpose exists to support the payment structure other than to provide a significant benefit of financing. The Company measures the transaction price based on the amount of consideration to which the Company expects to be entitled in exchange for transferring the promised goods and/or services to the customer. The Company utilizes either the expected value method or the most likely amount method to estimate the amount of variable consideration, depending on which method is expected to better predict the amount of consideration to which the Company will be entitled. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. With respect to arrangements that include payments for a development or regulatory milestone payment, the Company evaluates whether the associated event is considered likely of achievement and estimates the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within the Company’s control or the control of the licensee, such as those dependent upon receipt of regulatory approval, are not considered to be likely of achievement until the triggering event occurs. At the end of each reporting period, the Company re-evaluates the probability of achievement of each milestone and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and net loss in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based upon the achievement of a certain level of product sales, wherein the license is deemed to be the sole or predominant item to which the payments relate, the Company recognizes revenue upon the later of: (i) when the related sales occur or (ii) when the performance obligation to which some or all of the payment has been allocated has been satisfied (or partially satisfied). Consideration that would be received for optional goods and/or services is excluded from the transaction price at contract inception. ​ Accounts Receivable ​ Accounts receivable arise from product sales and are recognized at the amounts invoiced to customers, net of applicable reserves for variable consideration. The Company analyzes the actual payment history of its customers, the aging of receivables, current customer-specific developments and economic trends to estimate the reserve for current expected credit losses. ​ Inventory ​ The Company values its inventories at the lower of cost or estimated net realizable value. Costs, which include amounts related to direct labor, materials and manufacturing overhead, are determined using standard costs, which approximate average cost. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and it writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded within cost of product revenue. The Company capitalizes inventory costs associated with the Company’s products after regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Inventory acquired prior to receipt of marketing approval of a product candidate is expensed as research and development expense as incurred. Inventory that can be used in either the production of clinical or commercial product is expensed as research and development expense when selected for use in a clinical manufacturing campaign. Inventory produced that will be used in promotional marketing campaigns is expensed to selling and marketing expense when it is selected for use in a marketing program. ​ Fair Value Measurements ​ Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ● Level 1—Quoted prices in active markets for identical assets or liabilities. ​ ● Level 2—Observable inputs (other than Level 1 quoted prices) such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ​ ● Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. ​ Derivative Instruments ​ The Company recognizes all derivative instruments as either assets or liabilities at fair value through profit or loss on the Company's consolidated balance sheet. Changes in the estimated fair value of derivative instruments are recognized in other income (expense), net in the consolidated statements of operations and comprehensive loss. If the Company determines that a financial or non-financial contract, a ‘host contract’, includes implicit or explicit terms that affect the cash flows of the contract in a manner similar to a stand-alone derivative instrument, an ‘embedded derivative’, the Company analyzes whether to account for the embedded derivative separately. The Company accounts for an embedded derivative not separately from the host contract if it is clearly and closely related to the host contract or if the entire contract is measured at fair value through profit or loss. In other cases, the Company accounts for an embedded derivative separately. ​ The Company measures the value of embedded derivatives that are accounted for separately at their respective fair values and recognizes changes in the respective estimated fair values in other income (expense), net in the consolidated statements of operations and comprehensive loss during the period of change. Embedded derivatives that are accounted for separately are recognized as derivative liabilities in the Company’s consolidated balance sheet. ​ The Convertible Notes, as discussed in Note 9, allow the holders to convert all or part of the outstanding principal of their Convertible Notes into shares of the Company’s common stock provided that no conversion results in a holder beneficially owning more than 19.99% of the issued and outstanding common stock of the Company. The entire embedded conversion option is required to be separated from the Convertible Notes and accounted for as a freestanding derivative instrument subject to derivative accounting. The main input when determining the fair value of the Convertible Notes is the bond yield that pertains to the host instrument without the conversion option. The significant assumption used in determining the bond yield is the market yield movements of a comparable instrument issued as of the valuation date, which is assessed and updated each period. Therefore, the entire conversion option is bifurcated from the underlying debt instrument and accounted for and valued separately from the host instrument. ​ The Barings Credit Agreement, as discussed in Note 9, contains an embedded obligation to pay a royalty fee that meets the criteria to be bifurcated and accounted for separately from the Barings Credit Facility, as discussed in Note 9, subject to derivative accounting. The main inputs when determining the fair value of the derivative liability are the amount and timing of our expected future revenue, the estimated volatility of these revenues, and the discount rate corresponding to the risk of revenue. ​ Property and Equipment ​ Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over a three ​ Leases ​ The Company determines whether an arrangement is or contains a lease at inception. Operating leases are recognized on the consolidated balance sheets as operating lease assets, current portion of lease liabilities and long-term lease liabilities. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease liabilities and their corresponding operating lease assets are recorded based on the present value of lease payments over the expected remaining lease term. The operating lease assets also include any lease payments made and adjustments for prepayments and lease incentives. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilized its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company reassesses the lease term and remeasures the lease liability if triggering events occur. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Impairment of Long-Lived Assets ​ Long-lived assets consist of property and equipment and right-of-use assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. The Company has had no impairment triggers of long-lived assets. ​ Research and Development Costs ​ Research and development costs are expensed as incurred. Included in research and development expenses are salaries, stock-based compensation and benefits of employees and other operational costs related to the Company’s research and development activities, including external costs of outside vendors engaged to conduct preclinical studies and clinical trials, manufacturing costs of the Company’s products prior to regulatory approval, costs related to collaboration agreements and facility-related expenses. ​ The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received, estimates provided by vendors, and contracted costs. Judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. ​ Advertising Costs ​ Advertising costs are expensed as incurred. ​ ​ Accounting for Stock-Based Compensation ​ The Company measures all stock options and other stock-based awards granted to employees, directors, and nonemployees at the fair value on the date of the grant. The fair value of the awards is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions. ​ The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre-vesting forfeitures for service-based awards. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual forfeiture rate is materially different from the Company’s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods. ​ Compensation cost related to shares purchased through the Company’s employee stock purchase plan, which is considered compensatory, is based on the estimated fair value of the shares on the offering date, including consideration of the discount and the look-back period. The Company estimates the fair value of the shares using a Black-Scholes option pricing model. Compensation expense is recognized over the six ​ The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. ​ Income Taxes ​ The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. ​ The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate. ​ Interest and penalties related to income taxes are recorded as part of the income tax provision. ​ ​ Segment Data ​ The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing its bioresorbable hydrogel product candidates for the programed-release delivery of therapeutic agents, specifically for ophthalmology. All property and equipment, net and all operating lease assets are held in the United States. All product revenue, net is attributable to the United States. Collaboration revenue is attributable to a customer in China (Note 3). ​ Comprehensive Loss ​ Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2023, 2022 and 2021, there were no items that gave rise to other comprehensive loss and therefore, there was no difference between net loss and comprehensive loss. ​ Net Loss Per Share ​ Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities, outstanding stock options and common stock warrants, except where the result would be anti-dilutive. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of the conversion of convertible debt securities, the exercise of outstanding stock options and common stock warrants. In the diluted net loss per share calculation, net loss would also be adjusted for the elimination of interest expense on convertible debt securities and the mark-to-market gain or loss on bifurcated conversion options, if the impact was not anti-dilutive. ​ Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) and adopted by the Company as of the specified effective date. The Company believes that recently issued accounting pronouncements that are not yet effective will not have a material impact on our consolidated financial statements and disclosures.

Licensing Agreements and Deferr

Licensing Agreements and Deferred Revenue	12 Months Ended
	Dec. 31, 2023
Licensing Agreements and Deferred Revenue
Licensing Agreements and Deferred Revenue	3. Licensing Agreements and Deferred Revenue ​ Incept License Agreement (in-licensing) ​ On September 13, 2018, the Company entered into a second amended and restated license agreement with Incept, LLC (“Incept”) to use and develop certain intellectual property (the “Incept License”). Under the Incept License, as amended and restated, the Company was granted a worldwide, perpetual, exclusive license to use specific Incept technology to develop and commercialize products that are delivered to or around the human eye for diagnostic, therapeutic or prophylactic purposes relating to ophthalmic diseases or conditions. The Company is obligated to pay low single-digit royalties on net sales of commercial products developed using the licensed technology, commencing with the date of the first commercial sale of such products and until the expiration of the last to expire of the patents covered by the license. Any of the Company’s sublicensees also will be obligated to pay Incept a royalty equal to a low single-digit percentage of net sales made by it and will be bound by the terms of the agreement to the same extent as the Company. The Company is obligated to reimburse Incept for its share of the reasonable fees and costs incurred by Incept in connection with the prosecution of the patent applications licensed to the Company under the Incept License. ​ Royalties paid under this agreement related to product sales were $1,713, $1,466 and $1,333 for the years ended December 31, 2023, 2022 and 2021, respectively. Royalties have been charged to cost of product revenue. ​ AffaMed License Agreement (out-licensing) ​ On October 29, 2020, the Company entered into a license agreement (“License Agreement”) with AffaMed Therapeutic Limited (“AffaMed”) for the development and commercialization of the Company’s DEXTENZA product regarding ocular inflammation and pain following cataract surgery and allergic conjunctivitis (collectively, the “DEXTENZA Field”) and for the Company’s PAXTRAVA, formerly known as OTX-TIC, product candidate (collectively with DEXTENZA, the “AffaMed Licensed Products”) regarding open-angle glaucoma or ocular hypertension (collectively, the “TIC Field” and, with the DEXTENZA Field, each a “Field”), in each case in mainland China, Taiwan, Hong Kong, Macau, South Korea, and the countries of the Association of Southeast Asian Nations (collectively, the “Territories”). The Company retains development and commercialization rights for the AffaMed Licensed Products in the rest of the world. ​ Under the License Agreement, the Company received a non-refundable upfront payment of $12,000 in December 2020, a $1,000 milestone in the fourth quarter of 2021, a $2,000 clinical support payment in the second quarter of 2022, and a $1,000 milestone payment in the second quarter of 2023. The Company is also eligible to receive up to an additional $87,000 in aggregate upon the achievement of certain regulatory, development and commercial milestones. The Company is also entitled to receive tiered, escalating royalties on the net sales of the AffaMed Licensed Products ranging from a low-teen to low-twenties percentage. Royalties under the License Agreement are payable on an AffaMed Licensed Product-by-AffaMed Licensed Product and jurisdiction-by-jurisdiction basis and are subject to potential reductions in specified circumstances, subject to a specified floor. ​ Under the License Agreement, the Company is generally responsible for expenses related to the development of the AffaMed Licensed Products in the applicable Fields in the Territories, provided that AffaMed (i) reimburse the Company a low-teen percentage of expenses incurred in connection with certain clinical trials conducted by the Company and designed to support marketing approval of the AffaMed Licensed Product by the FDA or the European Medicines Agency (“Global Studies”); (ii) is solely responsible for expenses incurred in connection with territory-specific clinical trials that it conducts in furtherance of the development plan agreed between the parties in the applicable Fields in the Territories (“Local Studies”); and (iii) reimburse the Company in full for expenses incurred in connection with obtaining and maintaining regulatory approvals of the AffaMed Licensed Products in the applicable Fields in the Territories. In the event AffaMed declines to participate in a Global Study or to conduct a Local Study in any jurisdiction in which the Company determines to conduct such a study, the Company is relieved of its obligation to provide AffaMed clinical data from such study, other than safety data, unless AffaMed subsequently reimburses the Company in the amounts described above plus a prespecified premium. ​ The License Agreement expires upon the expiration of the last royalty term for the last AffaMed Licensed Product in any applicable Field in the Territories. Either party may, subject to specified cure periods, terminate the License Agreement in the event of the other party’s uncured breach. Either party may also terminate the License Agreement under specified circumstances relating to the other party’s insolvency. AffaMed has the right to terminate the License Agreement at any time after completion of a Phase 3 clinical trial for PAXTRAVA for any or no reason upon providing the Company three months’ notice. During an established period following its change of control or its entry into a global licensing agreement that includes the Territories with a third party, the Company has the option to terminate the License Agreement, subject to a specified notice period and the repayment of any costs and expenses incurred by AffaMed in connection with the License Agreement, including upfront and milestone payments AffaMed has previously paid to the Company, at a prespecified premium. ​ The Company concluded that AffaMed is a customer in this arrangement, and as such, the arrangement falls within the scope of the revenue recognition guidance in ASC 606. ​ At the inception of the License Agreement, the Company identified the following performance obligations in the agreement: ​ ● the license, regulatory filings and manufacturing of DEXTENZA (the “DEXTENZA Field performance obligation”); ​ ● the license, regulatory filings and manufacturing for the Company’s PAXTRAVA product candidate regarding open-angle glaucoma or ocular hypertension in the Territories (the “PAXTRAVA Field performance obligation”); ​ ● the conduct of a Phase 2 clinical trial of PAXTRAVA (the “Phase 2 Clinical Trial of PAXTRAVA performance obligation”); and ​ ● obligations to participate on various joint research, development and project committees, which the Company has concluded is not a material performance obligation. ​ The transaction price was allocated to the performance obligations based on the relative estimated standalone selling prices of each performance obligation. ​ The Company developed the estimated standalone selling price for the services and/or manufacturing and supply included in each of the performance obligations, as applicable, primarily based on the nature of the services to be performed and/or goods to be manufactured and estimates of the associated costs, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. ​ The Company has determined that any sales-based royalties and milestones will be recognized as the Company delivers the clinical and commercial manufactured product to AffaMed. Any changes in estimates may result in a cumulative catch-up based on the number of units of manufactured product delivered. ​ As of December 31, 2023, the transaction price was determined to be $16,000. All potential regulatory, development and commercial milestone payments in the amount of $87,000 did not meet the recognition criteria under the most likely method, because their achievement was highly dependent on factors outside the control of the Company and therefore, were excluded from the transaction price as of December 31, 2023. Furthermore, under the expected value method the Company excluded the potential royalties from the transaction price. ​ We recognize revenue related to the amounts allocated to the DEXTENZA Field performance obligation and the PAXTRAVA Field performance obligation based on the point in time upon which control of supply is transferred to AffaMed for each delivery of the associated supply. The Company currently expects to recognize the revenue over a period of approximately seven commencing on the date the Company begins delivering product to AffaMed. This estimate of this period considers the timing of development and commercial activities under the License Agreement and may be reduced or increased based on the various activities as directed by the joint committees, decisions made by AffaMed, regulatory feedback or other factors not currently known. ​ The Company recognized $573, $1,037 and $0 of collaboration revenue related to the Phase 2 Clinical Trial of PAXTRAVA performance obligation for the years ended December 31, 2023, 2022 and 2021, respectively. ​ As of December 31, 2023, the aggregate amount of the transaction price allocated to the partially unsatisfied Phase 2 Clinical Trial of PAXTRAVA performance obligation was $390. This amount is expected to be recognized as this performance obligation is satisfied through June 2025. ​ Deferred revenue activity for the year ended December 31, 2023 was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred Revenue Deferred revenue at December 31, 2022 ​ $ 13,963 Additions ​ ​ 1,000 Amounts recognized into revenue ​ ​ (573) Deferred revenue at December 31, 2023 ​ $ 14,390 ​ Regeneron Collaboration Agreement ​ On October 10, 2016, the Company entered into a Collaboration, Option and License Agreement (the “Regeneron Collaboration Agreement”) with Regeneron Pharmaceuticals, Inc. (“Regeneron”) for the development and potential commercialization of products using the Company’s hydrogel in combination with Regeneron’s large molecule VEGF-targeting compounds for the treatment of retinal diseases. ​ Under the terms of the Collaboration Agreement, the Company and Regeneron had agreed to conduct a joint research program with the aim of developing a sustained-release formulation of aflibercept, currently marketed under the tradename Eylea, that is suitable for advancement into clinical development. The Company had granted Regeneron an option (the “Option”) to enter into an exclusive, worldwide license to develop and commercialize products using the Company’s hydrogel in combination with Regeneron’s large molecule VEGF-targeting compounds (“Licensed Products”). Under the term of the Collaboration Agreement, Regeneron was responsible for funding an initial preclinical tolerability study. The Regeneron Collaboration Agreement was subsequently amended on May 8, 2020 (the “Regeneron Amendment”). Pursuant to the Regeneron Amendment, the Company and Regeneron had adopted a new work plan to transition joint efforts under the Regeneron Collaboration Agreement to the research and development of an extended-delivery formulation of aflibercept to be delivered to the suprachoroidal space. Regeneron had agreed to pay personnel and material costs of the Company for specified preclinical development activities in connection with the revised work plan, as well as certain other costs. In addition, the Regeneron Amendment provided for the modification of the terms of the Option previously granted to Regeneron under the Regeneron Collaboration Agreement. As amended, the Option was exclusive for twenty-four months following May 8, 2020. On August 5, 2021, Regeneron notified the Company of its termination of the Regeneron Collaboration Agreement, as amended. The termination became effective immediately. In connection with the termination of the Regeneron Collaboration Agreement, all licenses, options and other rights granted to either party under the Regeneron Collaboration Agreement automatically terminated, other than the surviving joint intellectual property rights described below. The Company and Regeneron also became obligated to undertake certain transition activities upon the termination, including the return of specified property of the other party. Each party retains an equal, undivided ownership interest, which may be transferred, licensed and otherwise exploited without a duty to account to the other party, in certain intellectual property rights jointly developed under the collaboration. As a result of the termination, the Company is no longer eligible to receive (i) reimbursement from Regeneron for ongoing research and development activities, (ii) a fee upon exercise of the Option, (iii) payments upon the achievement of specified development and regulatory milestones of the Regeneron Licensed Products, or (iv) tiered, escalating royalties in a range from a high-single digit to a low-to-mid teen percentage of net sales of Regeneron Licensed Products, in each case pursuant to the Regeneron Collaboration Agreement. The Company is also no longer obligated to reimburse Regeneron for certain development costs, up to an aggregate amount of in certain circumstances, were Regeneron to have exercised the Option. For the years ended December 31, 2023, 2022 and 2021, the Company had recorded $0, $0 and $768 related to work performed for preclinical development activities in connection with the revised work plan which the Company has recorded as a reduction of research and development expense as this research is not an output of the Company’s ordinary business activities. As of December 31, 2023 and 2022, the Company had not recorded any assets or liabilities with regard to the Regeneron Collaboration Agreement.

Cash Equivalents and Restricted

Cash Equivalents and Restricted Cash	12 Months Ended
	Dec. 31, 2023
Cash Equivalents and Restricted Cash
Cash Equivalents and Restricted Cash	4. Cash Equivalents and Restricted Cash ​ The Company’s statements of cash flows include restricted cash with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on such statements. A reconciliation of the cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same amounts shown in the statement of cash flows is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ 2023 2022 2021 Cash and cash equivalents ​ $ 195,807 ​ $ 102,300 ​ $ 164,164 Restricted cash (current) ​ ​ 150 ​ ​ — ​ ​ — Restricted cash (non-current) ​ ​ 1,614 ​ ​ 1,764 ​ ​ 1,764 Total cash, cash equivalents and restricted cash as shown on the statements of cash flows ​ $ 197,571 ​ $ 104,064 ​ $ 165,928 ​ The Company held restricted cash as security deposits for its real estate leases.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2023
Inventory
Inventory	5. Inventory ​ Inventory consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Raw materials ​ $ 302 ​ $ 309 Work-in-process ​ ​ 1,012 ​ ​ 899 Finished goods ​ 991 ​ 766 ​ ​ $ 2,305 ​ $ 1,974 ​

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2023
Property and Equipment, net
Property and Equipment, net	6. Property and Equipment, net ​ Property and equipment, net consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Equipment ​ $ 15,515 ​ $ 12,485 Leasehold improvements ​ 14,699 ​ 9,074 Furniture and fixtures ​ 1,268 ​ 1,268 Software ​ 236 ​ 236 Construction in progress ​ 281 ​ 4,071 ​ ​ 31,999 ​ 27,134 Less: Accumulated depreciation and amortization ​ (20,260) ​ (17,278) ​ ​ $ 11,739 ​ $ 9,856 ​ Depreciation and amortization expense was $2,983, $2,109 and $2,421 for the years ended December 31, 2023, 2022 and 2021, respectively. ​

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases
Leases	7. Leases ​ The Company leases real estate, including laboratory, manufacturing and office space. The Company’s leases have remaining lease terms ranging from less than 1 year to approximately 4.5 years. All of the Company’s leases qualify as operating leases. ​ The lease for the Company’s 20,445 square feet of manufacturing space located at 36 Crosby Drive in Bedford, Massachusetts commenced on June 30, 2018. On October 18, 2022, the Company exercised its option to extend the lease agreement by an additional five five five five five ​ The lease is for approximately 70,712 square feet of general office, research and development and manufacturing space located at 15 Crosby Drive in Bedford, Massachusetts. The lease term commenced on February 1, 2017 and will expire on July 31, 2027. The Company has the option to extend the lease for ​ The lease for 30,036 square feet of office space located at 24 Crosby Drive in Bedford, Massachusetts commenced on April 18, 2019 and terminates on March 31, 2024 and does not include any lease renewal options. ​ Recognized lease costs were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ 2023 ​ 2022 ​ 2021 Operating lease costs ​ $ 2,663 ​ $ 2,369 ​ $ 2,482 Variable lease costs ​ ​ 987 ​ ​ 756 ​ ​ 629 Total lease costs ​ $ 3,650 ​ $ 3,125 ​ $ 3,111 ​ The minimum lease payments for the next five years and thereafter are expected to be as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Year Ending December 31, ​ ​ 2023 2024 ​ ​ ​ ​ 2,504 2025 ​ ​ ​ ​ 2,673 2026 ​ ​ ​ ​ 2,709 2027 ​ ​ ​ ​ 2,111 2028 ​ ​ ​ ​ 716 Thereafter ​ ​ ​ ​ — Total lease payments ​ ​ ​ $ 10,713 Less: interest ​ ​ ​ ​ 2,249 Present value of operating lease liabilities ​ ​ ​ $ 8,464 ​ The following table summarizes the weighted average remaining lease term and the weighted average incremental borrowing rate used to determine the operating lease liability: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, ​ 2023 ​ ​ 2022 Weighted average remaining lease term in years ​ ​ 4.1 ​ ​ 4.9 ​ Weighted average discount rate ​ ​ 12.00 % ​ 13.41 % ​ Supplemental disclosure of cash flow information related to the Company’s operating leases included in cash flows provided by operating activities in its consolidated statements of cash flows is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ ​ For the ​ For the ​ ​ Year Ended ​ ​ Year Ended ​ Year Ended ​ ​ December 31, ​ ​ December 31, ​ December 31, ​ 2023 ​ ​ 2022 ​ 2021 Cash paid for amounts included in the measurement of lease liabilities ​ $ 2,663 ​ $ 2,549 ​ $ 2,482 ​

Expenses

Expenses	12 Months Ended
	Dec. 31, 2023
Expenses
Expenses	8. Expenses ​ The Company recognized $880, $1,166, and $1,925 of advertising expenses for the years ended December 31, 2023, 2022 and 2021, respectively. ​ Accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Accrued interest payable on Convertible Notes (Note 9) ​ 10,886 ​ 8,756 Accrued payroll and related expenses ​ $ 8,156 ​ $ 7,509 Accrued rebates and programs ​ 5,117 ​ 3,560 Accrued research and development expenses ​ 1,488 ​ 1,816 Accrued interest payable on Barings Credit Facility (Note 9) ​ 803 ​ — Accrued professional fees ​ ​ 691 ​ ​ 1,228 Accrued other ​ 1,525 ​ 1,228 ​ ​ $ 28,666 ​ $ 24,097 ​

Financial Liabilities

Financial Liabilities	12 Months Ended
	Dec. 31, 2023
Financial Liabilities
Financial Liabilities	​ 9. Financial Liabilities ​ Barings Credit Agreement On August 2, 2023 (the “Closing Date”), the Company entered into a credit and security agreement (the “Barings Credit Agreement”) with Barings Finance LLC (“Barings”), as administrative agent, and the lenders party thereto, providing for a secured term loan facility for the Company (the “Barings Credit Facility”) in the aggregate principal amount of $82,474 (the “Total Credit Facility Amount”). The Company borrowed the full amount of $82,474 at closing and received proceeds of $77,290, after the application of an original issue discount and fees. Indebtedness under the Barings Credit Facility matures on the earlier to occur of (i) the six-year anniversary of the Closing Date and (ii) the date that is 91 days prior to the maturity date for the Company’s Convertible Notes (as defined below). Indebtedness under the Barings Credit Facility incurs interest based on the Secured Overnight Financing Rate (“SOFR”), subject to a minimum 1.50% floor, plus 6.75%. The Company is obligated to make interest payments on its indebtedness under the Barings Credit Facility on a monthly basis, commencing on the Closing Date; to pay annual administration fees; and to pay, on the maturity date, any principal and accrued interest that remains outstanding as of such date. In addition, the Company is obligated to pay a fee in an amount equal to the Total Credit Facility Amount, which amount shall be reduced by the total amount of interest and principal prepayment fees paid under the Barings Credit Agreement (such fee, the “Barings Royalty Fee”). The Company is required to pay the Barings Royalty Fee in installments to Barings, for the benefit of the lenders, on a quarterly basis in an amount equal to three and one-half percent (3.5 %) of the net sales of DEXTENZA occurring during such quarter, subject to the terms, conditions and limitations specified in the Barings Credit Agreement, until the Barings Royalty Fee is paid in full. The Barings Royalty Fee is due and payable upon a change of control of the Company. In the event the Company completes a change of control transaction or a sale of all or substantially all of its assets on or prior to the twelve-month anniversary of the Closing Date, the Barings Royalty Fee is subject to a reduction to an amount that is equal to (i) % of the Total Credit Facility Amount, in the event that a signed letter of intent evidencing such transaction was entered into by the Company after the date that is six months, but before the date that is twelve months, after the Closing Date. The Company may, at its option, prepay any or all of the Barings Royalty Fee at any time without penalty. In connection with the Barings Credit Agreement, the Company granted the lenders thereto a first-priority security interest in all assets of the Company, including its intellectual property, subject to certain agreed-upon exceptions. The Barings Credit Agreement includes negative covenants restricting the Company from making payments to the holders of the Convertible Notes, except in connection with a proposed conversion to equity and with respect to certain permitted expenses and requiring the Company to maintain a minimum liquidity amount of The Company determined that the embedded obligation to pay the Barings Royalty Fee (the “Barings Royalty Fee Obligation”) is required to be separated from the Barings Credit Facility and accounted for as a freestanding derivative instrument subject to derivative accounting. The allocation of proceeds to the Barings Royalty Fee Obligation resulted in a discount on the Barings Credit Facility. The Company is amortizing the discount to interest expense over the term of the Barings Credit Facility using the effective interest method. Accrued or paid Barings Royalty Fees are included in the change in fair value of derivative liabilities on the consolidated statements of operations and comprehensive loss. For the year ended December 31, 2023, Barings Royalty Fees were $901. A summary of the Barings Credit Facility at December 31, 2023 is as follows: ​ ​ ​ ​ ​ ​ December 31, ​ 2023 Barings Credit Facility ​ $ 82,474 Less: unamortized discount ​ ​ (16,687) Total ​ $ 65,787 ​ As of December 31, 2023, the full principal for the Barings Credit Facility of $82,474 was due for repayment in 2029. Convertible Notes ​ On March 1, 2019, the Company issued $37,500 of convertible notes which accrue interest at an annual rate of 6% of their outstanding principal amount, which is payable, along with the principal amount at maturity, unless earlier converted, repurchased or redeemed (as amended the “Convertible Notes”). ​ Concurrently with entering into the Barings Credit Agreement, on August 2, 2023, the Company and the holders of the Convertible Notes extended the maturity of the Convertible Notes, which would otherwise have matured on March 1, 2026, to a date 91 days following the maturity of the indebtedness under the Barings Credit Facility, unless earlier converted, repurchased or redeemed (the “Amendment”). The Company accounted for the Amendment as an extinguishment of debt in accordance with the guidance in Accounting Standards Codification Topic 470-50 Debt ​ The holders of the Convertible Notes may convert all or part of the outstanding principal amount of their Convertible Notes into shares of the Company’s common stock, par value $0.0001 per share, prior to maturity and provided that no conversion results in a holder beneficially owning more than 19.99% of the issued and outstanding common stock of the Company. The conversion rate is initially 153.8462 shares of the Company’s common stock per $1,000 principal amount of the Convertible Notes, which is equivalent to an initial conversion price of $6.50 per share. The conversion rate is subject to adjustment in customary circumstances such as stock splits or similar changes to the Company’s capitalization. ​ Upon conversion by the holder, other than a conversion based on a Corporate Transactions as defined below, the Company has the right to select the settlement of the conversion in either shares of common stock, cash, or in a combination thereof. Upon any conversion of any Convertible Note, the Company is obligated to make a cash payment to the holder of such Convertible Note for any interest accrued but unpaid on the principal amount converted. ​ ​ ● If the Company elects to satisfy such conversion by shares of common stock, the Company shall deliver to the converting holder in respect of each $1,000 principal amount of Convertible Notes being converted a number of common shares equal to the conversion rate in effect on the conversion date; ​ ● If the Company elects to satisfy such conversion by cash settlement, the Company shall pay to the converting holder in respect of each $1,000 principal amount of Convertible Notes being converted cash in an amount equal to the sum of the Daily Conversion Values (as defined below) for each of the twenty (20) consecutive trading days during a specified period. The “Daily Conversion Values” is defined as each of the 20 consecutive trading days during the specified period, 5.0% of the product of (a) the conversion rate on such trading day and (b) the “Daily VWAP” on such trading day. The Daily VWAP is defined as each of the 20 consecutive trading days during the applicable Observation Period, the per share volume-weighted average price as displayed under the heading “Bloomberg VWAP” on the Bloomberg page for the Company. ​ ● If the Company elects to satisfy such conversion by combination, the Company shall pay or deliver, as the case may be, in respect of each $1,000 principal amount of Convertible Notes being converted, a settlement amount equal to the sum of the “Daily Settlement Amounts” (as defined below) for each of the twenty (20) consecutive trading days during the specified period. The “Daily Settlement Amount” is defined as, for each of the 20 consecutive trading days during the specified period: (a) cash in an amount equal to the lesser of (i) the Daily Measurement Value (as defined below) and (ii) the Daily Conversion Value on such Trading Day; and (b) if the Daily Conversion Value on such trading day exceeds the Daily Measurement Value, a number of Shares equal to (i) the difference between the Daily Conversion Value and the Daily Measurement Value, divided by (ii) the Daily VWAP for such Trading Day. The “Daily Measurement Value” is defined as the Specified Dollar Amount (as defined below), if any, divided by 20. The “Specified Dollar Amount” is defined as the maximum cash amount per $1,000 principal amount of Notes to be received upon conversion as specified in the notice specifying the Company’s chosen settlement method. ​ In the event of a Corporate Transaction, the noteholder shall have the right to either (a) convert all of the unpaid principal at the conversion rate and receive a cash payment equal to (i) the outstanding accrued but unpaid interest under the Convertible Note to, but excluding, the corporate transaction conversion date (to the extent such date occurs prior to a date 91 days following the maturity of the indebtedness under the Barings Credit Facility, the maturity date of the Convertible Notes) plus (ii) and an additional amount of consideration based on a sliding scale depending on the date of such as Corporate transaction or (b) require the Company to repurchase all or part of the outstanding principal amount of such Convertible Note at a repurchase price equal to 100% of the outstanding principal amount of the Convertible Note to be repurchased, plus accrued and unpaid interest to, but excluding, the repurchase date. ​ A corporate transaction includes (i) a merger or consolidation executed through a tender offer or change of control (other than one in which stockholders of the Company own a majority by voting power of the outstanding shares of the surviving or acquiring corporation); (ii) a sale, lease, transfer, of all or substantially all of the assets of the Company; or (iii) if the Company’s common stock ceases to be listed or quoted on any of the New York Stock Exchange, the Nasdaq Global Select Market, the Nasdaq Global Market or the Nasdaq Capital Market (the “Corporate Transaction”). ​ If the last reported sale price of the common stock has been at least 130% of the conversion rate then in effect for 20 of the preceding 30 trading days (including the last trading day of such period), the Company is entitled, at its option, to redeem all or part of the outstanding principal amount of the Convertible Notes, on a pro rata basis, at an optional redemption price equal to 100% of the outstanding principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the optional redemption date. ​ The Convertible Notes are subject to acceleration upon the occurrence of specified events of default, including a default or breach of certain contracts material to the Company and the delisting and deregistration of the Company’s common stock. ​ The Company determined that the embedded conversion option is required to be separated from the Convertible Notes and accounted for as a freestanding derivative instrument subject to derivative accounting. The allocation of proceeds to the conversion option results in a discount on the Convertible Notes. The Company is amortizing the discount to interest expense over the term of the Convertible Notes using the effective interest method. ​ The Company presents accrued interest in accrued current liabilities because the notes are currently convertible and the interest is payable in cash. The effective annual interest rate for the Convertible Notes was 19.4%, 14.8%, and 14.8% for the years ended December 31, 2023, 2022, and 2021, respectively. ​ A summary of the Convertible Notes at December 31, 2023 and 2022 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Convertible Notes ​ $ 37,500 ​ $ 37,500 Less: unamortized discount and current portion ​ ​ (28,362) ​ ​ (8,751) Total ​ $ 9,138 ​ $ 28,749 ​ Interest recognized with regard to the Convertible Notes was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 Coupon Interest ​ $ 2,130 ​ ​ 2,281 ​ ​ 2,281 Amortization of discount ​ ​ 2,042 ​ ​ 2,314 ​ ​ 2,128 Total ​ $ 4,172 ​ ​ 4,595 ​ ​ 4,409 ​ Notes Payable ​ The Company entered into a credit and security agreement in 2014 (as amended, the “MidCap Credit Agreement”) establishing a credit facility (as amended, the “MidCap Credit Facility”). The Company satisfied its obligations under the MidCap Credit Agreement in August 2023, as discussed below. In connection with its satisfaction of its obligations, the Company extinguished the MidCap Credit Facility, and all liens and security interests securing the indebtedness under the MidCap Credit Agreement were released. ​ In June 2021, the Company entered into a Fourth Amended and Restated Credit and Security Agreement (the “Fourth Amendment”) to amend the terms of its debt with existing lenders for total indebtedness of $20,833 and borrowed an incremental $4,167, for a total of $25,000. Under the Fourth Amendment, the Company was required to make interest-only payments through April 2024. Commencing in May 2024, the Company was required to make 19 equal monthly installments of principal in the amount of $1,042, plus interest, then on the maturity date, November 30, 2025 the remaining balance of $5,208 plus the exit fee, as defined below. Amounts borrowed under the MidCap Credit Facility based on the Fourth Amendment were initially at LIBOR base rate, subject to 1.00% floor, plus 6.75%. In addition, a final payment (exit fee) equal to 3.5% of amounts drawn under the MidCap Credit Facility, or $875 based on borrowings of $25,000, was due upon the maturity date of November 30, 2025. The Company had accrued the exit fee through November 30, 2025. The Company accounted for the Fourth Amendment as a modification in accordance with the guidance in ASC 470-50 Debt . Amounts paid to the lenders were recorded as debt discount and a new effective interest rate was established. ​ On March 12, 2023, the Company requested, and received, a protective advance of $2,000 under the MidCap Credit Agreement as a short-term bridge loan in response to the closure of Silicon Valley Bank by the California Department of Financial Protection and Innovation. This protective advance was deemed a credit extension. The Company repaid the full principal amount of $2,000 in March 2023. ​ On March 31, 2023, the Company entered into Amendment No. 1 to the MidCap Credit Agreement (“Amendment No. 1”) to replace the LIBOR-based interest rate provisions of the MidCap Credit Agreement with interest rate provisions based on SOFR, establish a benchmark replacement mechanism and make additional administrative updates. The Company accounted for Amendment No. 1 as a modification in accordance with the guidance in ASC 470-50 Debt On May 4, 2023, the Company entered into Amendment No. 2 to the MidCap Credit Agreement (“Amendment No. 2”). Amendment No. 2 provided that the Company may maintain up to 50% of its consolidated cash and cash equivalents with banks or financial institutions other than Silicon Valley Bank and made additional administrative updates. As of December 31, 2022, the Company had a total borrowing capacity of $ ​ Borrowings outstanding were as follows: ​ ​ ​ ​ ​ ​ December 31, ​ 2022 Borrowings outstanding ​ $ 25,000 Accrued exit fee ​ ​ 335 Unamortized discount ​ ​ (78) Long-term notes payable ​ $ 25,257 ​

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2023
Derivatives
Derivatives	​ 10. Derivatives ​ Barings Credit Agreement ​ The Barings Credit Agreement (Note 9) contains an embedded Royalty Fee Obligation that meets the criteria to be bifurcated and accounted for separately from the Barings Credit Facility (the "Royalty Fee Derivative Liability"). The Royalty Fee Derivative Liability was recorded at fair value upon the entering into the Barings Credit Facility and is subsequently remeasured to fair value at each reporting period. The Royalty Fee Derivative Liability was initially valued and is remeasured using a “with-and-without” method. The “with-and-without” methodology involves valuing the whole instrument on an as-is basis with the embedded Royalty Fee Obligation and then valuing the instrument without the embedded Royalty Fee Obligation. Royalty payments are estimated using a Monte Carlo simulation. Refer to Note 11 for details regarding the determination of fair value. A roll-forward of the Royalty Fee Derivative Liability is as follows: ​ ​ ​ ​ ​ ​ ​ As of Balance at August 2, 2023 ​ $ 12,604 Change in fair value ​ ​ (215) Balance at December 31, 2023 ​ $ 12,389 ​ Convertible Notes ​ The Convertible Notes (Note 9) contain the Conversion Option Derivative Liability, an embedded conversion option that meets the criteria to be bifurcated and accounted for separately from the Convertible Notes. The Conversion Option Derivative Liability was recorded at fair value upon the issuance of the Convertible Notes and is subsequently remeasured to fair value at each reporting period. The Conversion Option Derivative Liability was initially valued and are remeasured using a “with-and-without” method. The “with-and-without” methodology involves valuing the whole instrument on an as-is basis with the embedded conversion option and then valuing the instrument without the embedded conversion option. The difference between the entire instrument with the embedded conversion option compared to the instrument without the embedded conversion option is the fair value of the derivative, recorded as the Conversion Option Derivative Liability. Refer to Note 11 for details regarding the determination of fair value. ​ A roll-forward of the Conversion Option Derivative Liability, including the impact from accounting for the Convertible Notes Amendment, is as follows: ​ ​ ​ ​ ​ ​ ​ As of Balance at December 31, 2021 ​ $ 20,192 Change in fair value ​ ​ (13,841) Balance at December 31, 2022 ​ ​ 6,351 Change in fair value ​ ​ 4,502 Change in fair value from Convertible Notes Amendment ​ ​ 6,745 Balance at December 31, 2023 ​ $ 17,598 ​ Warrants ​ In April 2014, the Company entered into a credit facility with Silicon Valley Bank and MidCap Financial SBIC, LP, and it issued the lenders warrants to purchase 100,000 shares of its Series D-1 redeemable convertible preferred stock with an exercise price of $3.00 per share. Upon the closing of the Company’s IPO in July 2014, the preferred stock warrants became warrants to purchase an aggregate of 37,878 shares of its common stock with an exercise price of $7.92 per share, with Silicon Valley Bank and MidCap Financial SBIC, LP., each holding warrants The Company had warrants for the purchase of 18,939 shares of common stock outstanding with MidCap Financial SBIC, LP at December 31, 2020 at a weighted average exercise price of $7.92 per share and an expiration date of April 17, 2021. On January 29, 2021, holders of warrants to purchase 18,939 shares of common stock at an exercise price of $7.92 exercised their right to purchase their warrants. The exercise price of the warrants was paid through a net share settlement mechanism and as a result the Company issued shares of common stock to satisfy the exercise of all the warrants. There are no warrants outstanding as of December 31, 2023 and 2022, respectively.

Risks and Fair Value

Risks and Fair Value	12 Months Ended
	Dec. 31, 2023
Risks and Fair Value
Risks and Fair Value	11. Risks and Fair Value ​ Concentration of Credit Risk and of Significant Suppliers and Customers ​ Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. The Company has its cash and cash equivalents balances at two accredited financial institutions, in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. ​ ​ The Company is dependent on a small number of third-party manufacturers to supply products for research and development activities in its preclinical and clinical programs and for sales of its products. The Company’s development programs as well as revenue from future product sales could be adversely affected by a significant interruption in the supply of any of the components of these products. ​ Three specialty distributor customers accounted for the following percentages of the Company’s total revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ Customer 1 ​ ​ 49 % ​ 44 % ​ 42 % Customer 2 ​ ​ 25 ​ ​ 25 ​ ​ 26 ​ Customer 3 ​ ​ 11 ​ ​ 17 ​ ​ 17 ​ ​ Three specialty distributor customers accounted for the following percentages of the Company’s accounts receivables: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ ​ December 31, ​ 2023 ​ 2022 Customer 1 ​ ​ 50 % ​ 52 % Customer 2 ​ ​ 28 ​ ​ 24 ​ Customer 3 ​ ​ 11 ​ ​ 15 ​ ​ Change in Fair Value of Derivative Liabilities Other income (expenses) from the change in the fair values of derivative liabilities as presented on the Company’s consolidated statements of operations and comprehensive loss includes the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 Change in the fair value of the Conversion Option Derivative Liability ​ $ (4,502) ​ $ 13,841 ​ $ 78,121 Change in the fair value of Royalty Fee Derivative Liability ​ ​ 215 ​ ​ — ​ ​ — Barings Royalty Fee ​ ​ (901) ​ ​ — ​ ​ — ​ ​ $ (5,188) ​ $ 13,841 ​ $ 78,121 ​ Fair Value of Financial Assets and Liabilities The following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2023 and 2022 and indicate the level of the fair value hierarchy utilized to determine such fair value: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of ​ ​ December 31, 2023 Using: ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 187,951 ​ $ — ​ $ — ​ $ 187,951 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liability: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative liabilities ​ $ — ​ $ — ​ $ 29,987 ​ $ 29,987 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of ​ ​ December 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 30,188 ​ $ — ​ $ — ​ $ 30,188 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liability: ​ ​ ​ ​ Derivative liability ​ $ — ​ $ — ​ $ 6,351 ​ $ 6,351 ​ During the year ended December 31, 2023 and 2022, there were no transfers between Level 1 and 2. ​ The carrying value of accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair value due to the short-term nature of these assets and liabilities. The carrying value of the Company’s variable interest rate MidCap Credit Facility was recorded at amortized cost, which approximates fair value due to the variable interest rate. ​ Barings Credit Agreement and Royalty Fee Derivative Liability ​ At December 31, 2023, the Barings Credit Facility, net of the Royalty Fee Derivative Liability, was carried at amortized cost totaling $66,590 comprised of the $65,787 non-current liability (Note 9) and $803 accrued interest (Note 8). The estimated fair value of the Barings Credit Facility, without the Royalty Fee Derivative Liability, was $72,295 at December 31, 2023. The fair value of the Royalty Fee Derivative Liability is estimated using a Monte Carlo simulation. The use of this approach requires the use of Level 3 unobservable inputs. The main inputs when determining the fair value of the Royalty Fee Derivative Liability are the amount and timing of the expected future revenue of the Company, the estimated volatility of these revenues, and the discount rate corresponding to the risk of revenue. The estimated fair value presented is not necessarily indicative of an amount that could be realized in a current market exchange. The use of alternative inputs and estimation methodologies could have a material effect on these estimates of fair value. The main inputs to valuing the Royalty Fee Derivative Liability are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ December 31, ​ ​ ​ 2023 ​ Revenue volatility ​ ​ 67.0 % Revenue discount rate ​ ​ 15.8 % ​ The main inputs to valuing the Royalty Fee Derivative Liability as of the Closing Date were revenue volatility of 61.0%, and a revenue discount rate of 15.8%. ​ Convertible Notes and Conversion Option Derivative Liability ​ At December 31, 2023, the Convertible Notes, net of the Conversion Option Derivative Liability, were carried at amortized cost totaling $20,024, comprised of the $9,138 non-current liability (Note 9) and $10,886 accrued interest (Note 8). At December 31, 2022, the Convertible Notes, net of the Conversion Option Derivative Liability, were carried at amortized cost totaling $37,505, comprised of the $28,749 non-current liability (Note 9) and $8,756 accrued interest (Note 8). The estimated fair value of the Convertible Notes, without the Conversion Option Derivative Liability, was $22,665 and $33,177 at December 31, 2023 and 2022, respectively. ​ The fair value of the Convertible Notes with and without the conversion option is estimated using a binomial lattice approach. The use of this approach requires the use of Level 3 unobservable inputs. The main input when determining the fair value of the Convertible Notes is the bond yield that pertains to the host instrument without the conversion option. The significant assumption used in determining the bond yield is the market yield movements of a comparable instrument issued as of the valuation date, which is assessed and updated each period. The main input when determining the fair value for disclosure purposes is the bond yield which is updated each period to reflect the yield of a comparable instrument issued as of the valuation date. The estimated fair value presented is not necessarily indicative of an amount that could be realized in a current market exchange. The use of alternative inputs and estimation methodologies could have a material effect on these estimates of fair value. ​ The main inputs to valuing the Convertible Notes with the conversion option are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ Company's stock price ​ $ 4.46 ​ $ 2.81 ​ Volatility ​ ​ 88.4 % ​ 93.8 % Bond yield ​ ​ 20.8 % ​ 16.2 % ​ The bond yield was derived by making the fair value of the Convertible Notes equal to the face value on the issuance date. Fair value measurements are highly sensitive to changes in these inputs and significant changes in these inputs would result in a significantly higher or lower fair value.

Equity

Equity	12 Months Ended
	Dec. 31, 2023
Equity
Equity	12. Equity ​ Preferred Stock ​ The Amended and Restated Certificate of Incorporation authorized 5,000,000 shares of preferred stock, $0.0001 par value, all of which is undesignated and none of which are issued outstanding Common Stock ​ The Amended and Restated Certificate of Incorporation authorized 100,000,000 shares of the Company’s common stock. In June 2021, the Company adopted an amended and restated certificate of incorporation increasing the number of its authorized shares of its common stock to ​ On April 5, 2019, the Company entered into an Open Market Sales Agreement (the “2019 Sales Agreement”) with Jefferies LLC (“Jefferies”), under which the Company may offer and sell its common stock having aggregate proceeds of up to $50,000 from time-to-time through Jefferies, acting as agent. The Company did not sell any shares of common stock under the 2019 Sales Agreement in the twelve months ended December 31, 2021. On August 9, 2021, the Company and Jefferies mutually terminated the 2019 Sales Agreement and entered into another Open Market Sale Agreement (the “2021 Sales Agreement”) under which the Company may offer and sell shares of common stock of the Company having an aggregate offering price of up to $100,000 from time to time through Jefferies, acting as agent. In the twelve months ended December 31, 2023, the Company sold 1,514,926 shares of common stock under the 2021 Sales Agreement, resulting in gross proceeds to the Company of $9,897, and net proceeds, after accounting for issuance costs, of $9,532. The Company did not offer or sell shares of its common stock under the 2021 Sales Agreement during the twelve months ended December 31, 2022 and 2021, respectively. ​ On December 13, 2023, the Company entered into an underwriting agreement with Jefferies, BofA Securities, Inc. and Piper Sandler & Co. (collectively “the Underwriters”) in connection with an underwritten public offering of 30,800,000 shares of the Company’s common stock. Under the terms of this underwriting agreement, the Company also granted the Underwriters an option to purchase up to an additional 4,620,000 shares of common stock at the public offering price, less the underwriting discounts and commissions. On December 17, 2023, the Company sold all 35,420,000 shares of common stock and closed this underwritten public offering. The public offering price of the shares in this offering was $3.25 per share, and the Underwriters purchased all of the shares from the Company at a price of $3.055 per share. After deducting underwriting discounts and commissions and offering expenses, the Company received net proceeds from the offering of $107,725. ​ As of December 31, 2023, the Company had reserved 24,933,970 shares of common stock for the exercise of outstanding stock options, the vesting of restricted stock units, and the number of shares remaining available for grant under its stock-based compensation plans (Note 13).

Stock-Based Awards

Stock-Based Awards	12 Months Ended
	Dec. 31, 2023
Stock-Based Awards
Stock-Based Awards	13. Stock-Based Awards ​ For the years ended December 31, 2023 and 2022, the Company had four stock-based compensation plans under which it was able to grant stock-based awards, the 2014 Stock Incentive Plan (the “2014 Plan”), the 2021 Stock Incentive Plan (the “2021 Plan”), the 2019 Inducement Stock Incentive Plan (the “2019 Inducement Plan”), and the 2014 Employee Stock Purchase Plan (the “ESPP”) (collectively the “Stock Plans”). Certain inducement awards made prior to inception of the 2019 Inducement Plan were issued outside of the Stock Plans. The purpose of the Stock Plans is to provide incentives to employees, directors, and nonemployee consultants. The 2014 Plan and the 2021 Plan provide for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units (“RSUs”), stock appreciation rights and other stock-based awards. As of December 31, 2023 and 2022, respectively, the Company had an immaterial number of vested stock awards outstanding that were granted under the Company’s 2006 Stock Incentive Plan (the “2006 Plan”). Effective as of the adoption of the 2014 Plan by the Company’s stockholders in 2014, no new awards have been granted under the 2006 Plan. As of December 31, 2023, all then outstanding awards under the 2006 Plan remained in effect and continued to be governed by the terms of the 2006 Plan. ​ 2014 Plan 2021 Plan 2019 Inducement Plan - The 2019 Inducement Plan provides for the following types of awards, each of which is referred to as an “Award”: non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. Awards under the 2019 Inducement Plan may only be granted to persons who (a) were not previously an employee or director of the Company or (b) are commencing employment with the Company following a bona fide period of non-employment, in either case as an inducement material to the individual’s entering into employment with the Company and in accordance with the requirements of Nasdaq Stock Market Rule 5635(c)(4). For the avoidance of doubt, neither consultants nor advisors shall be eligible to participate in the 2019 Inducement Plan. Each person who is granted an Award under the 2019 Inducement Plan is deemed a “Participant”. On December 10, 2020, the board of directors of the Company amended the 2019 Inducement Plan to increase the aggregate number of shares issuable by . As of December 31, 2023, ​ ESPP Stock options granted pursuant to the Stock Plans, excluding awards under the ESPP, are granted at exercise prices not to be less than the fair value of common shares as of the date of grant. They generally require a service period of 4 years and generally vest monthly, or 1/4 1/3 Valuation of Awards ​ The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The expected life of the options was calculated using the simplified method. The simplified method defines the life as the average of the contractual term of the options and the weighted-average vesting period for all option tranches. The Company utilizes the simplified method because the Company does not have sufficient historical exercise data over the life of awards to provide a reasonable basis upon which to estimate expected term. The expected term of stock options granted to nonemployees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. The Company uses its historical volatility to estimate expected volatility. ​ The assumptions that the Company used to determine the fair value of the stock options granted to employees and directors are as follows, presented on a weighted average basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2023 2022 2021 Risk-free interest rate 3.72 % 2.10 % 0.80 % Expected term (in years) 6 6 6 ​ Expected volatility 77.32 % 81.14 % 87.65 % Expected dividend yield — % — % — % ​ For RSUs, the grant date fair value is the closing price of the Company’s stock on the grant date. ​ Stock Options ​ The following table summarizes the Company’s stock option activity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Shares Issuable ​ Exercise ​ Contractual ​ Intrinsic ​ Under Options Price Term Value ​ ​ ​ ​ ​ ​ ​ (In years) ​ ​ ​ Outstanding as of December 31, 2022 13,669,711 ​ $ 8.45 7.0 ​ $ 7 Granted 3,542,491 ​ 4.00 ​ ​ ​ ​ ​ Exercised (141,952) ​ 3.88 ​ ​ ​ ​ ​ Cancelled/forfeited (933,459) ​ 8.63 ​ ​ ​ ​ ​ Outstanding as of December 31, 2023 16,136,791 ​ $ 7.51 ​ 6.1 ​ $ 3,364 Options vested and expected to vest as of December 31, 2023 14,859,010 ​ $ 7.48 ​ 5.9 ​ $ 2,910 Options exercisable as of December 31, 2023 11,073,110 ​ $ 8.18 ​ 5.0 ​ $ 1,648 ​ The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised was $275, $186 and $6,779 during the years ended December 31, 2023, 2022 and 2021, respectively. ​ The weighted average grant date fair value of stock options granted to employees and directors during the years ended December 31, 2023, 2022 and 2021 was $2.74, $4.95 and $12.48 per share, respectively. ​ As of December 31, 2023, there were 67,509 outstanding unvested service-based stock options held by nonemployees. ​ RSUs ​ The following table summarizes the Company’s activity of unvested RSUs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ average ​ ​ ​ ​ grant date ​ RSU's fair value ​ ​ ​ ​ ​ ​ Unvested balance at December 31, 2022 1,092,682 ​ $ 5.03 Granted 1,113,964 ​ 4.00 Released ​ (393,805) ​ ​ 4.89 Cancelled/forfeited (185,500) ​ 4.75 Unvested balance at December 31, 2023 1,627,341 ​ $ 4.40 ​ ​ ​ ​ ​ ​ ​ Each RSU is equivalent to one share of common stock upon vesting. Typically, each RSU award vests on an annual basis over a three-year period. Holders of RSUs are not entitled to vote on any matters and are not entitled to dividends. The Company has determined the fair value of each RSU based on the closing price of the Company’s common stock on the date of grant and recognizes the compensation expense using the straight-line method over the service period, which coincides with the vesting period. ​ Stock-based Compensation ​ The Company recorded stock-based compensation expense in the following expense categories of its statements of operations and comprehensive loss: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 Research and development ​ $ 4,508 ​ $ 4,166 ​ $ 3,750 Selling and marketing ​ 3,682 ​ 4,684 ​ 4,014 General and administrative ​ 9,635 ​ 8,114 ​ 7,214 ​ ​ $ 17,825 ​ $ 16,964 ​ $ 14,978 ​ As of December 31, 2023, the Company had an aggregate of $16,537 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 2.02 years.

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2023
Employee Benefits
Employee Benefits	14. Employee Benefits ​ The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the plan may be made at the discretion of the board of directors. For the years ended December 31, 2023, 2022 and 2021, the Company has made contributions of $625, $593, and $493, respectively, to the 401(k) Plan.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Taxes
Income Taxes	15. Income Taxes ​ During the years ended December 31, 2023, 2022 and 2021, the Company recorded no income tax benefits for the net operating losses incurred or the research and development tax credits generated in each year, due to its uncertainty of realizing a benefit from those items. ​ A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Research and development tax credits 3.6 ​ 5.4 35.9 ​ State taxes, net of federal benefit 2.0 ​ 2.6 19.3 ​ Stock-based compensation (2.3) ​ (2.1) (7.8) ​ Derivative liability ​ — ​ 2.7 ​ 244.7 ​ Change in tax rate ​ (0.4) ​ 1.4 ​ (8.4) ​ Other (0.2) ​ (0.1) (3.8) ​ Change in the valuation allowance (23.7) ​ (30.9) (300.9) ​ Effective income tax rate — % — % — % ​ Changes in the valuation of the Royalty Fee Derivative Liability, except to the extent that they relate to actual royalties paid or accrued, do not provide a future tax benefit. To the extent the deferred tax asset related to the Royalty Fee Derivative Liability exceeds the deferred tax liability related to the Barings Credit Agreement, the excess is recorded as a permanent item. Changes in the valuation of the Conversion Option Derivative Liability do not provide a future tax benefit. To the extent the deferred tax asset related to the Conversion Option Derivative Liability exceeds the deferred tax liability related to the Convertible Notes, the excess is recorded as a permanent item. Net deferred tax assets consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 120,971 ​ $ 113,801 Tax credit carryforwards ​ 22,597 ​ 19,653 Capitalized start-up costs ​ 121 ​ 255 Capitalized research and development expenses, net - Sec. 59(e) : ​ 3,570 ​ 5,773 Capitalized research and development expenses, net Sec. 174 ​ ​ 19,491 ​ ​ 10,046 Operating lease liabilities ​ ​ 1,970 ​ ​ 2,422 Derivative liability ​ ​ 6,981 ​ ​ 1,497 Stock-based Awards ​ ​ 10,443 ​ ​ 8,783 Accrued expenses and other ​ 8,433 ​ 6,274 Total deferred tax assets ​ 194,577 ​ 168,504 Valuation allowance ​ (183,737) ​ (164,546) Net deferred tax assets ​ ​ 10,840 ​ ​ 3,958 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ Operating lease right of use assets ​ ​ (1,507) ​ ​ (1,895) Convertible Notes ​ ​ (6,603) ​ ​ (2,063) Barings Credit Facility ​ ​ (2,730) ​ ​ — Total deferred tax liabilities ​ ​ (10,840) ​ ​ (3,958) Net deferred tax assets ​ $ — ​ $ — ​ Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2023, 2022 and 2021 related primarily to the increase in net operating loss carryforwards, amortization of capitalized research and development expenses, and increase in research and development tax credit carryforwards were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 2021 Valuation allowance as of beginning of year ​ $ 164,546 ​ $ 142,637 ​ $ 123,020 Increases recorded to income tax provision ​ 19,191 ​ 21,909 ​ 19,617 Valuation allowance as of end of year ​ $ 183,737 ​ $ 164,546 ​ $ 142,637 ​ As of December 31, 2023, the Company had net operating loss (“NOL”) carryforwards for federal and state income tax purposes of $482,561 and $343,803 , respectively. The federal and state NOLs generated for annual periods prior to January 1, 2018 begin to expire in 2026. The Company’s federal NOLs generated for the years ended since December 31, 2018, which amounted to a total of ​ The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management considered the Company’s cumulative net losses and concluded that it is more likely than not that the Company would not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance was established against the net deferred tax assets as of December 31, 2023, 2022 and 2021. ​ The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2023, 2022 or 2021. ​ The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are still open under statute from the Company’s fiscal year 2019 to the present. Earlier years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2023
Net Loss Per Share
Net Loss Per Share	16. Net Loss Per Share ​ Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2023, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2023 2022 2021 Numerator: ​ ​ ​ Net loss attributable to common stockholders ​ $ (80,736) ​ $ (71,038) ​ $ (6,553) Denominator: ​ ​ ​ Weighted average common shares outstanding, basic ​ 79,827,362 ​ 76,875,035 ​ 76,392,870 Net loss per share - basic ​ $ (1.01) ​ $ (0.92) ​ $ (0.09) ​ Basic and diluted net loss per share was calculated as follows for the years ended December 31, 2023, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 ​ 2022 ​ 2021 Net loss attributable to common stockholders, basic ​ $ (80,736) ​ $ (71,038) ​ $ (6,553) Interest expense on Convertible Notes ​ 4,172 ​ 4,596 ​ 4,409 Gain on extinguishment of debt (Note 9) ​ ​ (14,907) ​ ​ — ​ ​ — Change in fair value of derivative liability ​ ​ 4,502 ​ ​ (13,841) ​ ​ (78,121) Net loss attributable to common stockholders, diluted ​ $ (86,969) ​ $ (80,283) ​ $ (80,265) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding, basic ​ ​ 79,827,362 ​ ​ 76,875,035 ​ ​ 76,392,870 Dilutive options (treasury stock method) ​ ​ — ​ ​ — ​ ​ — Shares issuable upon conversion of Convertible Notes, as if converted ​ ​ 5,769,232 ​ ​ 5,769,232 ​ ​ 5,769,232 Weighted average common shares outstanding, diluted ​ 85,596,594 ​ 82,644,267 ​ 82,162,102 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share attributable to common stockholders, diluted ​ $ (1.02) ​ $ (0.97) ​ $ (0.98) ​ The Company excluded the following common stock equivalents, outstanding as of December 31, 2023, 2022 and 2021 from the computation of diluted net loss per share attributable to common stockholders for the years ended December 31, 2023, 2022 and 2021 because they had an anti-dilutive impact due to the net loss incurred for the periods. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 2021 Options to purchase common stock 16,136,791 13,669,711 10,934,828 Restricted stock units ​ 1,627,341 ​ 1,092,682 ​ — ​ 17,764,132 14,762,393 10,934,828 ​

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies.
Commitments and Contingencies	17. Commitments and Contingencies ​ Indemnification Agreements In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend indemnified parties for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. To date, the Company has not incurred any material costs as a result of such indemnifications.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions
Related Party Transactions	18. Related Party Transactions The Company has engaged Wilmer Cutler Pickering Hale and Dorr LLP (“WilmerHale”) to provide certain legal services to the Company. The sister of the Company's former Chief Business Officer Christopher White was a managing partner at WilmerHale, who has not participated in providing legal services to the Company. The Company incurred fees for legal services rendered by WilmerHale of approximately $1,472, $959 and $1,396 for the years ended December 31, 2023, 2022 and 2021, respectively. As of December 31, 2023 and 2022, there was $298 and $0 recorded in accounts payable for WilmerHale. As of December 31, 2023 and 2022, there was $0 and $24 recorded in accrued expenses for WilmerHale. The Company has engaged Heier Consulting, LLC (“Heier Consulting”), an entity affiliated with Jeffrey Heier, M.D. a former member of the Company’s Board of Directors and the Company’s current Chief Scientific Officer, to provide advice or expertise on one or more of the Company’s development-stage drug or medical device products relating to retinal diseases or conditions under a consultant agreement. Compensation for these services is in the form of cash and stock-based awards. The total grant date fair value of stock-based awards granted to Heier Consulting is $96, which is recognized to expense on a straight-line basis over the respective vesting periods. The Company incurred cash-based fees for services rendered by Heier Consulting of approximately $32, 24, and $0 for the years ended December 31, 2023, 2022 and 2021, respectively. As of December 31, 2023 and 2022, there was $6 and $3 recorded in accounts payable for Heier Consulting. As of December 31, 2023 and 2022, there was $0 and $0 recorded in accrued expenses for Heier Consulting. Effective February 21, 2024, the Company and Heier Consulting terminated this relationship. In November 2020, the Company engaged Specialty Pharma Consulting, LLC (“Specialty Pharma”), an entity affiliated with Kevin Coughenour, to provide services for quality engineering and validation activities in the ordinary course of business. Mr. Coughenour is married to the Company’s former Chief Operating Officer Patricia Kitchen. On April 26, 2021, the Company and Specialty Pharma terminated their relationship. The Company incurred fees for quality engineering and validation activities rendered by Specialty Pharma of $0, $0 and $155 for the years ended December 31, 2023, 2022 and 2021, respectively. As of December 31, 2023 and 2022, there were no liabilities recorded with regard to Specialty Pharma.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events
Subsequent Events	19 . Subsequent Events Securities Purchase Agreement On February 21, 2024, the Company, entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain institutional accredited investors (the “Investors”), pursuant to which the Company issued and sold to the Investors in a private placement an aggregate of 32,413,560 shares of the Company’s common stock, par value $0.0001 per share (the “Shares”), at a price of $7.52 per share, and, to certain Investors in lieu of Shares, pre-funded warrants to purchase 10,805,957 shares of the Company’s common stock (the “Pre-Funded Warrants”), at a price of $7.519 per Pre-Funded Warrant (the “2024 Private Placement”). Each Pre-Funded Warrant issued in the 2024 Private Placement has an exercise price of $0.001 per share, is currently exercisable and will remain exercisable until the Pre-Funded Warrant is exercised in full. The 2024 Private Placement closed on February 26, 2024. The Company received aggregate gross proceeds from the 2024 Private Placement of approximately $325,000, before deducting placement agent fees and offering expenses. 2019 Inducement Plan On February 20, 2024, the Company’s board of directors amended the 2019 Inducement Plan to increase the aggregate number of shares issuable thereunder from 1,054,000 to 3,804,000 shares of common stock. On February 22, 2024, the Company granted a total of 1,527,019 non-statutory stock options and a total of 935,279 RSUs under the 2019 Inducement Plan to the Company’s newly appointed Executive Chairman and its new Chief Strategy Officer. ESPP The number of shares of common stock that may be issued under the ESPP will automatically increase on the first day of each fiscal year, commencing on January 1, 2015 and ending on December 31, 2024, in an amount equal to the least of 207,402 shares of the Company’s common stock, 0.5% of the number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year, and an amount determined by the Company’s board of directors. On January 1, 2024, the number of shares available for issuance under the ESPP increased by 207,402.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation ​ The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).
Use of Estimates	Use of Estimates ​ The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the measurement and recognition of reserves for variable consideration related to product sales, revenue recognition related to a collaboration agreement that contains multiple promises, the fair value of derivatives, stock-based compensation, and realizability of net deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.
Cash Equivalents	Cash Equivalents ​ The Company considers all short-term, highly liquid investments with original maturities of ninety days or less at date of purchase to be cash equivalents. Cash equivalents, which primarily consist of investments in money market funds, are stated at fair value.
Revenue Recognition	Revenue Recognition ​ The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606 – Revenue from Contracts with Customers To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies a performance obligation. At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. ​ Product Revenue ​ The Company sells DEXTENZA in the United States primarily to a limited number of specialty distributors (“SDs”) under individually negotiated distribution agreements. These customers then subsequently resell DEXTENZA to physicians, clinics and certain medical centers or hospitals. The Company also sells DEXTENZA directly to a small population of ambulatory surgery centers (“ASCs”) based on individually negotiated direct distribution agreements (the “Direct Customers”). In addition, the Company enters into arrangements with health care providers and payors that provide for government mandated or privately negotiated rebates and chargebacks with respect to the purchase of DEXTENZA. ​ The Company recognizes revenue on product sales when the customer obtains control of the Company's product, which occurs at a point in time (upon delivery to the customer). Product revenues are recorded net of applicable reserves for variable consideration, including discounts and allowances. ​ Transaction Price, including Variable Consideration ​ The amount of variable consideration which is included in the transaction price may be constrained, and is included in the net sales price, only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s original estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. ​ Trade Discounts and Allowances ​ Product Returns The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well as within accrued expenses and other current liabilities, in the accompanying consolidated balance sheets. The Company currently estimates product return reserves using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. ​ Government Chargebacks U.S. U.S. federal government Drug Discount Program Government Rebates ​ Purchaser/Provider Discounts and Rebates — The Company offers rebate payments for which ASCs, hospital out-patient departments and other prescribers qualify by meeting quarterly purchase volumes of DEXTENZA under the Company’s volume-based rebate program. The Company calculates rebate payment amounts due under this program quarterly, based on actual qualifying purchases and applies a contractual discount rate. In the third quarter of 2022, the Company implemented a separate off-invoice discount (“OID”) rebate program whereby end- users receive the discounted price immediately upon purchase, rather than having to wait until the end of the quarter for a rebate payment. The OID amounts are generally determined at the time of resale by SDs or direct sales to ASCs by the Company. The Company generally issues credits for such amounts within a few weeks of the SD’s notification to the Company of the resale. The Company includes the OID on the invoice when it sells to an ASC directly. The calculation of the accrual for all rebates is based on an estimate of claims that the Company expects to receive associated with product that has been recognized as revenue but also remains in the distribution channel inventories at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included as an accrued expenses and other current liabilities for volume-based rebates and as a reduction of accounts receivable for OID rebates. ​ Other Incentives ​ Collaboration Revenue ​ The Company evaluates contracts that contain multiple promises to determine which promises are distinct. Promises are considered to be distinct and therefore, accounted for as separate performance obligations, provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer and (ii) the promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. In assessing whether a promise is distinct, the Company considers factors such as whether: (i) the Company provides a significant service of integrating goods and/or services with other goods and/or services promised in the contract; (ii) one or more of the goods and/or services significantly modifies or customizes, or are significantly modified or customized by one or more of the other goods and/or services promised in the contract; and (iii) the goods and/or services are highly interdependent or highly interrelated. Individual goods or services (or bundles of goods and/or services) that meet both criteria for being distinct are accounted for as separate performance obligations. Promises that are not distinct at contract inception are combined and accounted for as a single performance obligation. Options to acquire additional goods and/or services are evaluated to determine if such option provides a material right to the customer that it would not have received without entering into the contract. If so, the option is accounted for as a separate performance obligation. If not, the option is considered a marketing offer which would be accounted for as a separate contract upon the customer’s election. ​ The Company considers the existence of any significant financing component within its arrangements based on whether a substantive business purpose exists to support the payment structure other than to provide a significant benefit of financing. The Company measures the transaction price based on the amount of consideration to which the Company expects to be entitled in exchange for transferring the promised goods and/or services to the customer. The Company utilizes either the expected value method or the most likely amount method to estimate the amount of variable consideration, depending on which method is expected to better predict the amount of consideration to which the Company will be entitled. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. With respect to arrangements that include payments for a development or regulatory milestone payment, the Company evaluates whether the associated event is considered likely of achievement and estimates the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within the Company’s control or the control of the licensee, such as those dependent upon receipt of regulatory approval, are not considered to be likely of achievement until the triggering event occurs. At the end of each reporting period, the Company re-evaluates the probability of achievement of each milestone and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and net loss in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based upon the achievement of a certain level of product sales, wherein the license is deemed to be the sole or predominant item to which the payments relate, the Company recognizes revenue upon the later of: (i) when the related sales occur or (ii) when the performance obligation to which some or all of the payment has been allocated has been satisfied (or partially satisfied). Consideration that would be received for optional goods and/or services is excluded from the transaction price at contract inception. ​
Accounts Receivable	Accounts Receivable ​ Accounts receivable arise from product sales and are recognized at the amounts invoiced to customers, net of applicable reserves for variable consideration. The Company analyzes the actual payment history of its customers, the aging of receivables, current customer-specific developments and economic trends to estimate the reserve for current expected credit losses.
Inventory	Inventory ​ The Company values its inventories at the lower of cost or estimated net realizable value. Costs, which include amounts related to direct labor, materials and manufacturing overhead, are determined using standard costs, which approximate average cost. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and it writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded within cost of product revenue. The Company capitalizes inventory costs associated with the Company’s products after regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Inventory acquired prior to receipt of marketing approval of a product candidate is expensed as research and development expense as incurred. Inventory that can be used in either the production of clinical or commercial product is expensed as research and development expense when selected for use in a clinical manufacturing campaign. Inventory produced that will be used in promotional marketing campaigns is expensed to selling and marketing expense when it is selected for use in a marketing program.
Fair Value Measurements	Fair Value Measurements ​ Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ● Level 1—Quoted prices in active markets for identical assets or liabilities. ​ ● Level 2—Observable inputs (other than Level 1 quoted prices) such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ​ ● Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.
Derivative Instruments	Derivative Instruments ​ The Company recognizes all derivative instruments as either assets or liabilities at fair value through profit or loss on the Company's consolidated balance sheet. Changes in the estimated fair value of derivative instruments are recognized in other income (expense), net in the consolidated statements of operations and comprehensive loss. If the Company determines that a financial or non-financial contract, a ‘host contract’, includes implicit or explicit terms that affect the cash flows of the contract in a manner similar to a stand-alone derivative instrument, an ‘embedded derivative’, the Company analyzes whether to account for the embedded derivative separately. The Company accounts for an embedded derivative not separately from the host contract if it is clearly and closely related to the host contract or if the entire contract is measured at fair value through profit or loss. In other cases, the Company accounts for an embedded derivative separately. ​ The Company measures the value of embedded derivatives that are accounted for separately at their respective fair values and recognizes changes in the respective estimated fair values in other income (expense), net in the consolidated statements of operations and comprehensive loss during the period of change. Embedded derivatives that are accounted for separately are recognized as derivative liabilities in the Company’s consolidated balance sheet. ​ The Convertible Notes, as discussed in Note 9, allow the holders to convert all or part of the outstanding principal of their Convertible Notes into shares of the Company’s common stock provided that no conversion results in a holder beneficially owning more than 19.99% of the issued and outstanding common stock of the Company. The entire embedded conversion option is required to be separated from the Convertible Notes and accounted for as a freestanding derivative instrument subject to derivative accounting. The main input when determining the fair value of the Convertible Notes is the bond yield that pertains to the host instrument without the conversion option. The significant assumption used in determining the bond yield is the market yield movements of a comparable instrument issued as of the valuation date, which is assessed and updated each period. Therefore, the entire conversion option is bifurcated from the underlying debt instrument and accounted for and valued separately from the host instrument. ​ The Barings Credit Agreement, as discussed in Note 9, contains an embedded obligation to pay a royalty fee that meets the criteria to be bifurcated and accounted for separately from the Barings Credit Facility, as discussed in Note 9, subject to derivative accounting. The main inputs when determining the fair value of the derivative liability are the amount and timing of our expected future revenue, the estimated volatility of these revenues, and the discount rate corresponding to the risk of revenue. ​
Property and Equipment	Property and Equipment ​ Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over a three ​
Leases	Leases ​ The Company determines whether an arrangement is or contains a lease at inception. Operating leases are recognized on the consolidated balance sheets as operating lease assets, current portion of lease liabilities and long-term lease liabilities. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease liabilities and their corresponding operating lease assets are recorded based on the present value of lease payments over the expected remaining lease term. The operating lease assets also include any lease payments made and adjustments for prepayments and lease incentives. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilized its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company reassesses the lease term and remeasures the lease liability if triggering events occur. Lease expense for lease payments is recognized on a straight-line basis over the lease term.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets ​ Long-lived assets consist of property and equipment and right-of-use assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. The Company has had no impairment triggers of long-lived assets.
Research and Development Costs	Research and Development Costs ​ Research and development costs are expensed as incurred. Included in research and development expenses are salaries, stock-based compensation and benefits of employees and other operational costs related to the Company’s research and development activities, including external costs of outside vendors engaged to conduct preclinical studies and clinical trials, manufacturing costs of the Company’s products prior to regulatory approval, costs related to collaboration agreements and facility-related expenses. ​ The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received, estimates provided by vendors, and contracted costs. Judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.
Advertising Costs	Advertising Costs ​ Advertising costs are expensed as incurred.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation ​ The Company measures all stock options and other stock-based awards granted to employees, directors, and nonemployees at the fair value on the date of the grant. The fair value of the awards is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions. ​ The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre-vesting forfeitures for service-based awards. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual forfeiture rate is materially different from the Company’s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods. ​ Compensation cost related to shares purchased through the Company’s employee stock purchase plan, which is considered compensatory, is based on the estimated fair value of the shares on the offering date, including consideration of the discount and the look-back period. The Company estimates the fair value of the shares using a Black-Scholes option pricing model. Compensation expense is recognized over the six ​ The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.
Income Taxes	Income Taxes ​ The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. ​ The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate. ​ Interest and penalties related to income taxes are recorded as part of the income tax provision.
Segment Data	Segment Data ​ The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing its bioresorbable hydrogel product candidates for the programed-release delivery of therapeutic agents, specifically for ophthalmology. All property and equipment, net and all operating lease assets are held in the United States. All product revenue, net is attributable to the United States. Collaboration revenue is attributable to a customer in China (Note 3).
Comprehensive Loss	Comprehensive Loss ​ Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2023, 2022 and 2021, there were no items that gave rise to other comprehensive loss and therefore, there was no difference between net loss and comprehensive loss.
Net Loss Per Share	Net Loss Per Share ​ Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities, outstanding stock options and common stock warrants, except where the result would be anti-dilutive. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of the conversion of convertible debt securities, the exercise of outstanding stock options and common stock warrants. In the diluted net loss per share calculation, net loss would also be adjusted for the elimination of interest expense on convertible debt securities and the mark-to-market gain or loss on bifurcated conversion options, if the impact was not anti-dilutive.
Recently Issued Accounting Pronouncements	​ Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) and adopted by the Company as of the specified effective date. The Company believes that recently issued accounting pronouncements that are not yet effective will not have a material impact on our consolidated financial statements and disclosures.

Licensing Agreements and Defe_2

Licensing Agreements and Deferred Revenue (Tables)	12 Months Ended
	Dec. 31, 2023
Licensing Agreements and Deferred Revenue
Schedule of deferred revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred Revenue Deferred revenue at December 31, 2022 ​ $ 13,963 Additions ​ ​ 1,000 Amounts recognized into revenue ​ ​ (573) Deferred revenue at December 31, 2023 ​ $ 14,390

Cash Equivalents and Restrict_2

Cash Equivalents and Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2023
Cash Equivalents and Restricted Cash
Reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheet to the total amounts shown in the statement of cash flows	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ 2023 2022 2021 Cash and cash equivalents ​ $ 195,807 ​ $ 102,300 ​ $ 164,164 Restricted cash (current) ​ ​ 150 ​ ​ — ​ ​ — Restricted cash (non-current) ​ ​ 1,614 ​ ​ 1,764 ​ ​ 1,764 Total cash, cash equivalents and restricted cash as shown on the statements of cash flows ​ $ 197,571 ​ $ 104,064 ​ $ 165,928

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2023
Inventory
Components of inventory	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Raw materials ​ $ 302 ​ $ 309 Work-in-process ​ ​ 1,012 ​ ​ 899 Finished goods ​ 991 ​ 766 ​ ​ $ 2,305 ​ $ 1,974 ​

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2023
Property and Equipment, net
Schedule of Property and Equipment net	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Equipment ​ $ 15,515 ​ $ 12,485 Leasehold improvements ​ 14,699 ​ 9,074 Furniture and fixtures ​ 1,268 ​ 1,268 Software ​ 236 ​ 236 Construction in progress ​ 281 ​ 4,071 ​ ​ 31,999 ​ 27,134 Less: Accumulated depreciation and amortization ​ (20,260) ​ (17,278) ​ ​ $ 11,739 ​ $ 9,856

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases
Summary of lease cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ 2023 ​ 2022 ​ 2021 Operating lease costs ​ $ 2,663 ​ $ 2,369 ​ $ 2,482 Variable lease costs ​ ​ 987 ​ ​ 756 ​ ​ 629 Total lease costs ​ $ 3,650 ​ $ 3,125 ​ $ 3,111
Schedule of minimum lease payments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Year Ending December 31, ​ ​ 2023 2024 ​ ​ ​ ​ 2,504 2025 ​ ​ ​ ​ 2,673 2026 ​ ​ ​ ​ 2,709 2027 ​ ​ ​ ​ 2,111 2028 ​ ​ ​ ​ 716 Thereafter ​ ​ ​ ​ — Total lease payments ​ ​ ​ $ 10,713 Less: interest ​ ​ ​ ​ 2,249 Present value of operating lease liabilities ​ ​ ​ $ 8,464
Schedule of weighted average remaining lease term and the average incremental borrowing rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, ​ 2023 ​ ​ 2022 Weighted average remaining lease term in years ​ ​ 4.1 ​ ​ 4.9 ​ Weighted average discount rate ​ ​ 12.00 % ​ 13.41 %
Supplemental disclosure of cash flow information related to our operating leases included in cash flows provided by operating activities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ ​ For the ​ For the ​ ​ Year Ended ​ ​ Year Ended ​ Year Ended ​ ​ December 31, ​ ​ December 31, ​ December 31, ​ 2023 ​ ​ 2022 ​ 2021 Cash paid for amounts included in the measurement of lease liabilities ​ $ 2,663 ​ $ 2,549 ​ $ 2,482

Expenses (Tables)

Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Accrued interest payable on Convertible Notes (Note 9) ​ 10,886 ​ 8,756 Accrued payroll and related expenses ​ $ 8,156 ​ $ 7,509 Accrued rebates and programs ​ 5,117 ​ 3,560 Accrued research and development expenses ​ 1,488 ​ 1,816 Accrued interest payable on Barings Credit Facility (Note 9) ​ 803 ​ — Accrued professional fees ​ ​ 691 ​ ​ 1,228 Accrued other ​ 1,525 ​ 1,228 ​ ​ $ 28,666 ​ $ 24,097 ​

Financial Liabilities (Tables)

Financial Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Instrument [Line Items]
Summary of debt	​ ​ ​ ​ ​ ​ December 31, ​ 2022 Borrowings outstanding ​ $ 25,000 Accrued exit fee ​ ​ 335 Unamortized discount ​ ​ (78) Long-term notes payable ​ $ 25,257 ​
Convertible Notes
Debt Instrument [Line Items]
Schedule of interest recognized with regard to debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 Coupon Interest ​ $ 2,130 ​ ​ 2,281 ​ ​ 2,281 Amortization of discount ​ ​ 2,042 ​ ​ 2,314 ​ ​ 2,128 Total ​ $ 4,172 ​ ​ 4,595 ​ ​ 4,409
Summary of debt	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Convertible Notes ​ $ 37,500 ​ $ 37,500 Less: unamortized discount and current portion ​ ​ (28,362) ​ ​ (8,751) Total ​ $ 9,138 ​ $ 28,749
Barings Credit Facility
Debt Instrument [Line Items]
Summary of debt	​ ​ ​ ​ ​ ​ December 31, ​ 2023 Barings Credit Facility ​ $ 82,474 Less: unamortized discount ​ ​ (16,687) Total ​ $ 65,787

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2023
Convertible Notes
Financial Liabilities
Summary of roll-forward of the derivative liability	​ ​ ​ ​ ​ ​ ​ As of Balance at December 31, 2021 ​ $ 20,192 Change in fair value ​ ​ (13,841) Balance at December 31, 2022 ​ ​ 6,351 Change in fair value ​ ​ 4,502 Change in fair value from Convertible Notes Amendment ​ ​ 6,745 Balance at December 31, 2023 ​ $ 17,598
Barings Credit Facility
Financial Liabilities
Summary of roll-forward of the derivative liability	​ ​ ​ ​ ​ ​ ​ As of Balance at August 2, 2023 ​ $ 12,604 Change in fair value ​ ​ (215) Balance at December 31, 2023 ​ $ 12,389

Risks and Fair Value (Tables)

Risks and Fair Value (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Summary of Concentration of Credit Risk and of Significant Suppliers and Customers	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ Customer 1 ​ ​ 49 % ​ 44 % ​ 42 % Customer 2 ​ ​ 25 ​ ​ 25 ​ ​ 26 ​ Customer 3 ​ ​ 11 ​ ​ 17 ​ ​ 17 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ ​ December 31, ​ 2023 ​ 2022 Customer 1 ​ ​ 50 % ​ 52 % Customer 2 ​ ​ 28 ​ ​ 24 ​ Customer 3 ​ ​ 11 ​ ​ 15 ​
Schedule of assets and liabilities measured at fair Value on recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of ​ ​ December 31, 2023 Using: ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 187,951 ​ $ — ​ $ — ​ $ 187,951 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liability: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative liabilities ​ $ — ​ $ — ​ $ 29,987 ​ $ 29,987 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of ​ ​ December 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 30,188 ​ $ — ​ $ — ​ $ 30,188 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liability: ​ ​ ​ ​ Derivative liability ​ $ — ​ $ — ​ $ 6,351 ​ $ 6,351
Schedule of change in fair value of derivative liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the ​ For the ​ For the ​ ​ ​ Year Ended ​ Year Ended ​ Year Ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ 2021 Change in the fair value of the Conversion Option Derivative Liability ​ $ (4,502) ​ $ 13,841 ​ $ 78,121 Change in the fair value of Royalty Fee Derivative Liability ​ ​ 215 ​ ​ — ​ ​ — Barings Royalty Fee ​ ​ (901) ​ ​ — ​ ​ — ​ ​ $ (5,188) ​ $ 13,841 ​ $ 78,121
Royalty Fee Derivative Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Schedule of main inputs to valuing the Derivative Liability	​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ December 31, ​ ​ ​ 2023 ​ Revenue volatility ​ ​ 67.0 % Revenue discount rate ​ ​ 15.8 %
Shares issuable upon conversion of Convertible Notes, if converted
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Schedule of main inputs to valuing the Derivative Liability	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2023 ​ 2022 ​ Company's stock price ​ $ 4.46 ​ $ 2.81 ​ Volatility ​ ​ 88.4 % ​ 93.8 % Bond yield ​ ​ 20.8 % ​ 16.2 %
Summary of roll-forward of the derivative liability	​ ​ ​ ​ ​ ​ ​ As of Balance at December 31, 2021 ​ $ 20,192 Change in fair value ​ ​ (13,841) Balance at December 31, 2022 ​ ​ 6,351 Change in fair value ​ ​ 4,502 Change in fair value from Convertible Notes Amendment ​ ​ 6,745 Balance at December 31, 2023 ​ $ 17,598

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	12 Months Ended
	Dec. 31, 2023
Stock-Based Awards
Schedule of stock-based compensation expense related to stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 Research and development ​ $ 4,508 ​ $ 4,166 ​ $ 3,750 Selling and marketing ​ 3,682 ​ 4,684 ​ 4,014 General and administrative ​ 9,635 ​ 8,114 ​ 7,214 ​ ​ $ 17,825 ​ $ 16,964 ​ $ 14,978
Schedule of Assumptions Used to Determine Fair Value of Stock Options Granted to Employees and Directors Presented on Weighted Average Basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2023 2022 2021 Risk-free interest rate 3.72 % 2.10 % 0.80 % Expected term (in years) 6 6 6 ​ Expected volatility 77.32 % 81.14 % 87.65 % Expected dividend yield — % — % — %
Schedule of Stock Option Activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Shares Issuable ​ Exercise ​ Contractual ​ Intrinsic ​ Under Options Price Term Value ​ ​ ​ ​ ​ ​ ​ (In years) ​ ​ ​ Outstanding as of December 31, 2022 13,669,711 ​ $ 8.45 7.0 ​ $ 7 Granted 3,542,491 ​ 4.00 ​ ​ ​ ​ ​ Exercised (141,952) ​ 3.88 ​ ​ ​ ​ ​ Cancelled/forfeited (933,459) ​ 8.63 ​ ​ ​ ​ ​ Outstanding as of December 31, 2023 16,136,791 ​ $ 7.51 ​ 6.1 ​ $ 3,364 Options vested and expected to vest as of December 31, 2023 14,859,010 ​ $ 7.48 ​ 5.9 ​ $ 2,910 Options exercisable as of December 31, 2023 11,073,110 ​ $ 8.18 ​ 5.0 ​ $ 1,648
Schedule of Restricted Stock Activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ average ​ ​ ​ ​ grant date ​ RSU's fair value ​ ​ ​ ​ ​ ​ Unvested balance at December 31, 2022 1,092,682 ​ $ 5.03 Granted 1,113,964 ​ 4.00 Released ​ (393,805) ​ ​ 4.89 Cancelled/forfeited (185,500) ​ 4.75 Unvested balance at December 31, 2023 1,627,341 ​ $ 4.40 ​ ​ ​ ​ ​ ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Taxes
Reconciliation of Federal Income Tax Rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Research and development tax credits 3.6 ​ 5.4 35.9 ​ State taxes, net of federal benefit 2.0 ​ 2.6 19.3 ​ Stock-based compensation (2.3) ​ (2.1) (7.8) ​ Derivative liability ​ — ​ 2.7 ​ 244.7 ​ Change in tax rate ​ (0.4) ​ 1.4 ​ (8.4) ​ Other (0.2) ​ (0.1) (3.8) ​ Change in the valuation allowance (23.7) ​ (30.9) (300.9) ​ Effective income tax rate — % — % — %
Net Deferred Tax Assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 120,971 ​ $ 113,801 Tax credit carryforwards ​ 22,597 ​ 19,653 Capitalized start-up costs ​ 121 ​ 255 Capitalized research and development expenses, net - Sec. 59(e) : ​ 3,570 ​ 5,773 Capitalized research and development expenses, net Sec. 174 ​ ​ 19,491 ​ ​ 10,046 Operating lease liabilities ​ ​ 1,970 ​ ​ 2,422 Derivative liability ​ ​ 6,981 ​ ​ 1,497 Stock-based Awards ​ ​ 10,443 ​ ​ 8,783 Accrued expenses and other ​ 8,433 ​ 6,274 Total deferred tax assets ​ 194,577 ​ 168,504 Valuation allowance ​ (183,737) ​ (164,546) Net deferred tax assets ​ ​ 10,840 ​ ​ 3,958 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ Operating lease right of use assets ​ ​ (1,507) ​ ​ (1,895) Convertible Notes ​ ​ (6,603) ​ ​ (2,063) Barings Credit Facility ​ ​ (2,730) ​ ​ — Total deferred tax liabilities ​ ​ (10,840) ​ ​ (3,958) Net deferred tax assets ​ $ — ​ $ —
Changes in Valuation Allowance for Deferred Tax Assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 2021 Valuation allowance as of beginning of year ​ $ 164,546 ​ $ 142,637 ​ $ 123,020 Increases recorded to income tax provision ​ 19,191 ​ 21,909 ​ 19,617 Valuation allowance as of end of year ​ $ 183,737 ​ $ 164,546 ​ $ 142,637

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Net Loss Per Share
Schedule of basic and diluted net (loss) income per share attributable to common stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2023, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2023 2022 2021 Numerator: ​ ​ ​ Net loss attributable to common stockholders ​ $ (80,736) ​ $ (71,038) ​ $ (6,553) Denominator: ​ ​ ​ Weighted average common shares outstanding, basic ​ 79,827,362 ​ 76,875,035 ​ 76,392,870 Net loss per share - basic ​ $ (1.01) ​ $ (0.92) ​ $ (0.09) ​ Basic and diluted net loss per share was calculated as follows for the years ended December 31, 2023, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 ​ 2022 ​ 2021 Net loss attributable to common stockholders, basic ​ $ (80,736) ​ $ (71,038) ​ $ (6,553) Interest expense on Convertible Notes ​ 4,172 ​ 4,596 ​ 4,409 Gain on extinguishment of debt (Note 9) ​ ​ (14,907) ​ ​ — ​ ​ — Change in fair value of derivative liability ​ ​ 4,502 ​ ​ (13,841) ​ ​ (78,121) Net loss attributable to common stockholders, diluted ​ $ (86,969) ​ $ (80,283) ​ $ (80,265) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding, basic ​ ​ 79,827,362 ​ ​ 76,875,035 ​ ​ 76,392,870 Dilutive options (treasury stock method) ​ ​ — ​ ​ — ​ ​ — Shares issuable upon conversion of Convertible Notes, as if converted ​ ​ 5,769,232 ​ ​ 5,769,232 ​ ​ 5,769,232 Weighted average common shares outstanding, diluted ​ 85,596,594 ​ 82,644,267 ​ 82,162,102 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share attributable to common stockholders, diluted ​ $ (1.02) ​ $ (0.97) ​ $ (0.98)
Schedule of antidilutive securities, excluded from computation of diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 2021 Options to purchase common stock 16,136,791 13,669,711 10,934,828 Restricted stock units ​ 1,627,341 ​ 1,092,682 ​ — ​ 17,764,132 14,762,393 10,934,828

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details) - USD ($) $ in Thousands	1 Months Ended
	Feb. 29, 2024	Dec. 31, 2023	Aug. 02, 2023	Dec. 31, 2022	Dec. 31, 2021
Nature of Business
Accumulated deficit		$ 697,578		$ 616,842
Cash and cash equivalents		195,807		$ 102,300	$ 164,164
Barings Credit Facility
Nature of Business
Debt Instrument, covenants, minimum liquidity requirement		$ 20,000	$ 20,000
Subsequent Event
Nature of Business
Gross proceeds from common stock	$ 325,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Mar. 01, 2019	Dec. 31, 2023
Summary Of Significant Accounting Policies
ESPP, period for recognition of expense		6 months
Minimum
Summary Of Significant Accounting Policies
Property and equipment, estimated useful life		3 years
Maximum
Summary Of Significant Accounting Policies
Property and equipment, estimated useful life		5 years
Convertible Notes
Summary Of Significant Accounting Policies
Maximum beneficial ownership percent	19.99%	19.99%

Licensing Agreements and Defe_3

Licensing Agreements and Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Collaboration Agreement
Revenue recognized				$ 58,443	$ 51,494	$ 43,522
Total deferred revenue:
Deferred revenue, beginning balance				13,963
Additions				1,000
Amounts recognized into revenue				(573)
Deferred revenue, ending balance				14,390	13,963
Incept
Collaboration Agreement
Royalties paid				1,713	1,466	1,333
License Agreement | AffaMed
Collaboration Agreement
Amount of non-refundable upfront payments received							$ 12,000
Additional payments to be received upon the achievement of certain development and commercial milestones				87,000
Milestone payment received	$ 1,000		$ 1,000
Clinical support payment received		$ 2,000
Transaction price				16,000
Potential regulatory, development and commercial milestone payments excluded from transaction price				$ 87,000
License Agreement | AffaMed | Minimum
Collaboration Agreement
Remaining performance obligation, expected timing of satisfaction, period				7 years
License Agreement | AffaMed | Maximum
Collaboration Agreement
Remaining performance obligation, expected timing of satisfaction, period				8 years
License Agreement | AffaMed | OTX-TIC Product
Collaboration Agreement
Revenue recognized				$ 573	1,037	0
Transaction price allocated to performance obligations partially unsatisfied				390
Collaboration, Option and License Agreement | Regeneron Pharmaceuticals, Inc
Collaboration Agreement
Collaboration Agreement termination, reimbursement of certain development costs no longer required, amount				30,000
Amount of cost recorded, to date, for work performed for preclinical development activities in connection with the revised work plan				$ 0	$ 0	$ 768

Cash Equivalents and Restrict_3

Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 195,807	$ 102,300	$ 164,164
Restricted cash (current)	150
Restricted cash (non-current)	1,614	1,764	1,764
Total cash, cash equivalents and restricted cash as shown on the statements of cash flows	$ 197,571	$ 104,064	$ 165,928	$ 229,821

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory
Raw materials	$ 302	$ 309
Work-in-process	1,012	899
Finished goods	991	766
Total inventory	$ 2,305	$ 1,974

Property and Equipment, net - S

Property and Equipment, net - Schedule of Property and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property and Equipment, net
Property and equipment, gross	$ 31,999	$ 27,134
Less: Accumulated depreciation and amortization	(20,260)	(17,278)
Property and equipment, net	11,739	9,856
Equipment
Property and Equipment, net
Property and equipment, gross	15,515	12,485
Leasehold improvements
Property and Equipment, net
Property and equipment, gross	14,699	9,074
Furniture and fixtures
Property and Equipment, net
Property and equipment, gross	1,268	1,268
Software
Property and Equipment, net
Property and equipment, gross	236	236
Construction in progress
Property and Equipment, net
Property and equipment, gross	$ 281	$ 4,071

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment, net
Depreciation and amortization expense	$ 2,983	$ 2,109	$ 2,421

Leases - Other (Details)

Leases - Other (Details) $ in Thousands		1 Months Ended	12 Months Ended
	Apr. 18, 2019 ft²	Jun. 30, 2016 ft² period	Dec. 31, 2023 USD ($) ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Leases
Operating lease liabilities | $			$ (1,813)	$ 2,729	$ (1,358)
Minimum
Leases
Lease term			1 year
Maximum
Leases
Lease term			4 years 6 months
Office space at 24 Crosby Drive
Leases
Area of lease	30,036
Options to renew	false
Manufacturing space at 36 Crosby Drive
Leases
Area of lease			20,445
Renewal terms			5 years
Operating lease liabilities | $			$ 4,284
Research and manufacturing space at 15 Crosby Drive
Leases
Area of lease		70,712
Renewal terms		5 years
Additional periods for renewal | period		2
Research and manufacturing space at 15 Crosby Drive | Minimum
Leases
Written notice period to extend the lease		12 months
Research and manufacturing space at 15 Crosby Drive | Maximum
Leases
Written notice period to extend the lease		15 months

Leases - Costs (Details)

Leases - Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease Costs
Operating lease costs	$ 2,663	$ 2,369	$ 2,482
Variable lease costs	987	756	629
Total lease costs	$ 3,650	$ 3,125	$ 3,111

Leases - Future minimum payment

Leases - Future minimum payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Minimum lease payments
2024	$ 2,504
2025	2,673
2026	2,709
2027	2,111
2028	716
Total lease payments	10,713
Less: interest	2,249
Present value of operating lease liabilities	$ 8,464

Leases - Terms and discount rat

Leases - Terms and discount rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases
Weighted average remaining lease term in years	4 years 1 month 6 days	4 years 10 months 24 days
Weighted average discount rate	12%	13.41%
Supplemental disclosure of cash flow information related to operating leases
Cash paid for amounts included in the measurement of lease liabilities	$ 2,663	$ 2,549	$ 2,482

Expenses - Summary (Details)

Expenses - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Expenses
Accrued interest payable on Convertible Notes (Note 9)	$ 10,886	$ 8,756
Accrued payroll and related expenses	8,156	7,509
Accrued rebates and programs	5,117	3,560
Accrued research and development expenses	1,488	1,816
Accrued interest payable on Barings Credit Facility (Note 9)	803
Accrued professional fees	691	1,228
Accrued other	1,525	1,228
Total	$ 28,666	$ 24,097

Expenses - Additional Informati

Expenses - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Expenses
Advertising expenses	$ 880	$ 1,166	$ 1,925

Financial Liabilities - Barings

Financial Liabilities - Barings Credit Agreement - Terms (Details) - Barings Credit Facility - USD ($) $ in Thousands		12 Months Ended
	Aug. 02, 2023	Dec. 31, 2023
Financial Liabilities
Borrowing capacity under the agreement	$ 82,474
Principal amount of debt issued	82,474
Proceeds from issuance of debt, net	$ 77,290
Royalty fees payable as percentage of net sales.	3.50%
Minimum liquidity amount	$ 20,000	$ 20,000
Barings Royalty Fees		$ 901
SOFR-based rate
Financial Liabilities
Interest rate floor (as a percent)	1.50%
Basis spread (as a percent)	6.75%
Change of control, Entered on or Prior to Six Months After the Closing Date
Financial Liabilities
Royalty fees payable reduction , percentage of total credit facility amount.	20%
Change of control, Entered After Six Months, but Before Twelve Months, After Closing Date.
Financial Liabilities
Royalty fees payable reduction , percentage of total credit facility amount.	30%

Financial Liabilities - Barin_2

Financial Liabilities - Barings Credit Agreement - Summary (Details) - Barings Credit Facility $ in Thousands	Dec. 31, 2023 USD ($)
Credit Agreement
Debt instrument carrying amount	$ 82,474
Less: unamortized discount	(16,687)
Total	65,787
Due for repayment in 2029	$ 82,474

Financial Liabilities - Convert

Financial Liabilities - Convertible Notes, Terms (Details)			12 Months Ended
	Aug. 02, 2023 USD ($)	Mar. 01, 2019 USD ($) D $ / shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021
Financial Liabilities
Gain (loss) on extinguishment of debt			$ 14,190,000
Common stock, par value | $ / shares		$ 0.0001	$ 0.0001	$ 0.0001
Convertible Notes
Financial Liabilities
Principal amount of debt issued		$ 37,500,000	$ 37,500,000	$ 37,500,000
Interest rate (as a percent)		6%
Extinguishment of debt, amount	$ 51,090,000
Fair value of convertible notes including conversion option	36,183,000
Debt instrument fair value	18,482,000		22,665,000	$ 33,177,000
Conversion option derivative liability, fair value	17,701,000
Convertible Notes, fair value portion included in accrued expenses	$ 9,943,000
Gain (loss) on extinguishment of debt			$ 14,907,000
Effective annual interest rate (as a percent)			19.40%	14.80%	14.80%
Maximum beneficial ownership percent		19.99%	19.99%
Conversion rate		153.8462
Principal amount of debt that is used in conversion calculations		$ 1,000
Initial conversion price | $ / shares		$ 6.50
Consecutive trading days | D		20
Percentage of product of conversion rate and daily VWAP		5%
Percentage of outstanding principal amount		100%
Convertible Notes | On or after March 1, 2022
Financial Liabilities
Debt repurchase price percent		100%
Consecutive trading days | D		30
Minimum percentage of common stock for conversion of debt		130%
Consecutive proceeding trading days for conversion of purchase price | D		20

Financial Liabilities - Conve_2

Financial Liabilities - Convertible Notes, Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Mar. 01, 2019
Financial Liabilities
Total	$ 9,138	$ 28,749
Convertible Notes
Financial Liabilities
Convertible Notes	37,500	37,500	$ 37,500
Less: unamortized discount and current portion	(28,362)	(8,751)
Total	$ 9,138	$ 28,749

Financial Liabilities - Conve_3

Financial Liabilities - Convertible Notes, Interest (Details) - Convertible Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest recognized
Coupon Interest	$ 2,130	$ 2,281	$ 2,281
Amortization of discount	2,042	2,314	2,128
Total	$ 4,172	$ 4,595	$ 4,409

Financial Liabilities - Notes P

Financial Liabilities - Notes Payable, Additional Information (Details) - USD ($)			1 Months Ended			12 Months Ended
	May 04, 2023	Mar. 12, 2023	Aug. 31, 2023	Mar. 31, 2023	Jun. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Credit Agreement
Protective advance requested under Credit Agreement representing a short-term bridge loan						$ 2,000,000
Repayment of protective advance						2,000,000
Gain on extinguishment of debt						$ (14,190,000)
2021 Amended Credit Facility
Credit Agreement
Outstanding borrowings under credit facility, net of unamortized discount					$ 20,833,000			$ 25,000,000
Net proceeds from credit facility					4,167,000
Final payment due at maturity					$ 5,208,000
Exit fee (as a percent)					3.50%
Credit Facility, Final Interest Payment					$ 875,000
Debt instrument carrying amount					$ 25,000,000
2021 Amended Credit Facility | Period commencing May 2024
Credit Agreement
Number of equal monthly installments					19
Required monthly principal payment					$ 1,042,000
2021 Amended Credit Facility | LIBOR
Credit Agreement
Interest rate floor (as a percent)					1%
Basis spread (as a percent)					6.75%
MidCap Credit Facility
Credit Agreement
Debt instrument carrying amount							$ 25,000,000
Protective advance requested under Credit Agreement representing a short-term bridge loan		$ 2,000,000
Repayment of protective advance				$ 2,000,000
Borrowing capacity under the agreement							$ 25,000,000
Repayment of debt including principal, interest, exit and prepayment fees			$ 26,157,000
Repayment of debt, principal and interest			25,017,000
Payment of exit and prepayment fees in satisfaction of debt obligation			1,140,000
Gain on extinguishment of debt			$ 717,000
MidCap Credit Facility | Maximum
Credit Agreement
Threshold percent of cash and cash equivalents to be maintained under debt agreement	50%

Financial Liabilities - Notes_2

Financial Liabilities - Notes Payable, Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Credit Agreement
Long-term notes payable	$ 65,787	$ 25,257
MidCap Credit Facility
Credit Agreement
Debt instrument carrying amount		25,000
Accrued exit fee		335
Less: unamortized discount		(78)
Long-term notes payable		$ 25,257

Derivatives - Liability roll fo

Derivatives - Liability roll forward (Details) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Royalty Fee Derivative Liability
Roll forward of the Derivatives
Balance at beginning of period	$ 12,604
Change in fair value	(215)
Balance at end of period	$ 12,389	$ 12,389
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Derivative Liability, Noncurrent	Derivative Liability, Noncurrent
Conversion Option Derivative Liability
Roll forward of the Derivatives
Balance at beginning of period		$ 6,351	$ 20,192
Change in fair value		4,502	(13,841)
Change in fair value from Convertible Notes Amendment		(6,745)
Balance at end of period	$ 17,598	$ 17,598	$ 6,351
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Derivative Liability, Noncurrent	Derivative Liability, Noncurrent	Derivative Liability, Noncurrent

Derivatives - Warrants (Details

Derivatives - Warrants (Details) - $ / shares		12 Months Ended
	Jan. 29, 2021	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	Jul. 31, 2014	Apr. 30, 2014
Warrants
Warrants outstanding			0	0
Series D-1 Redeemable Convertible Preferred Stock Warrants | Silicon Valley Bank and MidCap Financial SBIC, LP
Warrants
Number of shares callable by warrants							100,000
Weighted average exercise price to purchase common stock							$ 3
Warrants for Common Stock
Warrants
Number of shares callable by warrants	18,939
Weighted average exercise price to purchase common stock	$ 7.92
Warrants for Common Stock | Silicon Valley Bank and MidCap Financial SBIC, LP
Warrants
Number of shares callable by warrants						37,878
Weighted average exercise price to purchase common stock						$ 7.92
Warrants for Common Stock | Silicon Valley Bank
Warrants
Number of shares callable by warrants						18,939
Warrants for Common Stock | MidCap Financial, SBIC, LP
Warrants
Number of shares callable by warrants					18,939	18,939
Warrants for Common Stock | MidCap Financial, SBIC, LP | Weighted Average
Warrants
Weighted average exercise price to purchase common stock					$ 7.92
Common Stock
Warrants
Common stock issued upon exercise of warrants	11,737	11,737

Risks and Fair Value - Concentr

Risks and Fair Value - Concentration of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2023 customer item	Dec. 31, 2022 customer	Dec. 31, 2021 customer
Concentration risk
Number Of financial institutions | item	2
Total revenue | Customer
Concentration risk
Number of major customers	3	3	3
Total revenue | Customer | Customer one
Concentration risk
Concentration risk	49%	44%	42%
Total revenue | Customer | Customer two
Concentration risk
Concentration risk	25%	25%	26%
Total revenue | Customer | Customer three
Concentration risk
Concentration risk	11%	17%	17%
Accounts receivable | Customer
Concentration risk
Number of major customers	3	3
Accounts receivable | Customer | Customer one
Concentration risk
Concentration risk	50%	52%
Accounts receivable | Customer | Customer two
Concentration risk
Concentration risk	28%	24%
Accounts receivable | Customer | Customer three
Concentration risk
Concentration risk	11%	15%

Risks and Fair Value - Change i

Risks and Fair Value - Change in Fair Value of Derivative Labilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Barings Royalty Fees	$ (901)
Total	(5,188)	$ 13,841	$ 78,121
Conversion Option Derivative Liability
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative liability	$ (4,502)	$ 13,841	$ 78,121
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total	Total	Total
Royalty Fee Derivative Liability
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative liability	$ 215
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total	Total	Total

Risks and Fair Value - Fair Val

Risks and Fair Value - Fair Value Measurement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Aug. 02, 2023
Liability:
Transfers Between Fair Value Measurement Levels	$ 0	$ 0
Non-current liability	9,138	28,749
Notes Payable, Noncurrent	65,787	25,257
Barings Credit Facility
Liability:
Debt instrument carrying amount	82,474
Accrued interest payable on Convertible Notes	803
Estimated fair value	72,295
Notes Payable, Noncurrent	65,787
Notes payable, amortized cost, including accrued interest	66,590
Convertible Notes
Liability:
Debt instrument carrying amount	20,024	37,505
Non-current liability	9,138	28,749
Accrued interest payable on Convertible Notes	10,886	8,756
Estimated fair value	22,665	33,177	$ 18,482
Recurring Basis
Liability:
Derivative liabilities	$ 29,987	$ 6,351
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Derivative Liability, Noncurrent	Derivative Liability, Noncurrent
Money Market Funds | Recurring Basis
Assets:
Cash equivalents	$ 187,951	$ 30,188
Level 1 | Money Market Funds | Recurring Basis
Assets:
Cash equivalents	187,951	30,188
Level 3 | Recurring Basis
Liability:
Derivative liabilities	$ 29,987	$ 6,351

Risks and Fair Value - The main

Risks and Fair Value - The main inputs to valuing the Royalty Fee Derivative Liability (Details)) - Royalty Fee Derivative Liability [Member] - Level 3	Dec. 31, 2023	Aug. 02, 2023
Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liability, Measurement Input	0.670	0.610
Revenue discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liability, Measurement Input	0.158	0.158

Risks and Fair Value - Measurem

Risks and Fair Value - Measurement inputs (Details) - Convertible Notes	Dec. 31, 2023	Dec. 31, 2022
Company's stock price
Derivative Liability
Debt instrument, measurement input	4.46	2.81
Volatility
Derivative Liability
Debt instrument, measurement input	88.4	93.8
Bond yield
Derivative Liability
Debt instrument, measurement input	20.8	16.2

Equity - Preferred Stock (Detai

Equity - Preferred Stock (Details) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Equity
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Equity-Common Stock (Details)

Equity-Common Stock (Details) $ / shares in Units, $ in Thousands					12 Months Ended
	Dec. 17, 2023 USD ($) $ / shares shares	Dec. 13, 2023 shares	Aug. 09, 2021 USD ($)	Apr. 05, 2019 USD ($)	Dec. 31, 2023 USD ($) Vote $ / shares shares	Dec. 31, 2022 $ / shares shares	Dec. 31, 2021 shares	Jun. 30, 2021 shares	Dec. 31, 2020 shares
Common Stock
Common stock, shares authorized					200,000,000	200,000,000		200,000,000	100,000,000
Preferred stock, shares authorized					5,000,000	5,000,000
Preferred stock, par value | $ / shares					$ 0.0001	$ 0.0001
Net proceeds from issuance of common stock | $					$ 117,261
Voting right description					Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders.
Common stock shares, reserved					24,933,970
Number of votes per share | Vote					1
Common Stock
Common Stock
Number of shares issued	35,420,000				36,934,926
Net proceeds from issuance of common stock | $	$ 107,725
2019 Sales Agreement | Common Stock
Common Stock
Maximum aggregate proceeds from offering | $				$ 50,000
Over-allotment Option | Common Stock
Common Stock
Number of shares issued		4,620,000
Common stock, price per share | $ / shares	$ 3.055
Follow-on Offering | Common Stock
Common Stock
Number of shares issued		30,800,000
Common stock, price per share | $ / shares	$ 3.25
2021 Sales Agreement | Common Stock
Common Stock
Number of shares issued					1,514,926
Number of shares issued						0	0
Net proceeds from issuance of common stock | $					$ 9,532
Maximum aggregate proceeds from offering | $			$ 100,000		$ 9,897

Stock-Based Awards - Stock Ince

Stock-Based Awards - Stock Incentive Plan (Details)				12 Months Ended
	Jun. 14, 2023 shares	Jun. 16, 2022 shares	Dec. 10, 2020 shares	Dec. 31, 2014 shares	Dec. 31, 2023 item shares	Dec. 31, 2022 item	Dec. 31, 2021 shares	Jan. 01, 2021 shares
Stock-Based Awards
Number of shares of common stock reserved for issuance					24,933,970
2014 and 2006 Stock Incentive Plan
Stock-Based Awards
Granted (in shares)				0
Number of shares of common stock reserved for issuance							9,766,336
2014 Stock Incentive Plan
Stock-Based Awards
Number of stock based compensation plans | item					4	4
Number of shares of common stock reserved for issuance					456,334
2014 Stock Incentive Plan | Common Stock
Stock-Based Awards
Number of shares of common stock reserved for issuance				1,336,907				8,622,647
2021 Incentive Plan
Stock-Based Awards
Number of shares of common stock reserved for issuance					6,000,000
Additional number of shares authorized for issuance	3,900,000	3,600,000
Number of shares of common stock available for issuance					6,219,678
2019 Inducement Plan
Stock-Based Awards
Number of shares of common stock authorized for issuance			1,054,000
Additional number of shares authorized for issuance			554,000
Number of shares of common stock available for issuance					551,375

Stock-Based Awards - ESPP (Deta

Stock-Based Awards - ESPP (Details)			12 Months Ended
	Jan. 01, 2023 shares	Jan. 01, 2015 shares	Dec. 31, 2023 shares
Stock-Based Awards
Number of shares of common stock reserved for issuance			24,933,970
Number of RSU is equivalent to common share			1
Common Stock
Stock-Based Awards
Additional shares of common stock that may be issued under the plan		207,402
Employee Stock Option [Member]
Stock-Based Awards
Service period			4 years
Contractual term of Stock Options granted			10 years
Employee Stock Option [Member] | Share-Based Payment Arrangement
Stock-Based Awards
Percentage of first anniversary of the grant date			25%
Restricted Stock Units (RSUs)
Stock-Based Awards
Service period			3 years
Percentage of first anniversary of the grant date			0.33%
Vesting period			3 years
2014 Employee Stock Purchase Plan | Common Stock
Stock-Based Awards
Number of shares of common stock reserved for issuance			207,402
Additional shares of common stock that may be issued under the plan		207,402
Additional number of shares of common stock , percentage		0.50%
Additional number of shares authorized for issuance	207,402
Number of shares of common stock available for issuance			398,784

Stock-Based Awards - Fair Value

Stock-Based Awards - Fair Value Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assumptions Used to Determine Fair Value of Stock Options Granted to Employees and Directors Presented on a Weighted Average Basis
Risk-free interest rate	3.72%	2.10%	0.80%
Expected term (in years)	6 years	6 years	6 years
Expected volatility	77.32%	81.14%	87.65%

Stock-Based Awards - Schedule o

Stock-Based Awards - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Shares Issuable Under Options
Shares Issuable Under Options, Beginning balance	13,669,711
Shares Issuable Under Options, Granted	3,542,491
Shares Issuable Under Options, Exercised	(141,952)
Shares Issuable Under Options, Cancelled/forfeited	(933,459)
Shares Issuable Under Options, Ending balance	16,136,791	13,669,711
Shares Issuable Under Options, Vested and expected to vest	14,859,010
Shares Issuable Under Options, Exercisable	11,073,110
Weighted Average Exercise Price
Weighted Average Exercise Price, Beginning balance	$ 8.45
Weighted Average Exercise Price, Granted	4
Weighted Average Exercise Price, Exercised	3.88
Weighted Average Exercise Price, Cancelled/forfeited	8.63
Weighted Average Exercise Price, Ending balance	7.51	$ 8.45
Weighted Average Exercise Price, Vested and expected to vest	7.48
Weighted Average Exercise Price, Exercisable	$ 8.18
Weighted Average Remaining Contractual Term	6 years 1 month 6 days	7 years
Weighted Average Remaining Contractual Term, Vested and Expected to vest	5 years 10 months 24 days
Weighted Average Remaining Contractual Term, Exercisable	5 years
Other disclosures
Aggregate Intrinsic Value	$ 3,364	$ 7
Aggregate Intrinsic Value, Vested and Expected to vest	2,910
Aggregate Intrinsic Value, Exercisable	1,648
Aggregate intrinsic value of stock options exercised	$ 275	$ 186	$ 6,779
Weighted average fair value of stock option granted	$ 2.74	$ 4.95	$ 12.48

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details)	Dec. 31, 2023 shares
Stock-Based Awards
Unvested service-based stock options held by nonemployees	67,509

Stock-Based Awards - Schedule_2

Stock-Based Awards - Schedule of Restricted Stock Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Restricted Common Stock
Weighted average grant date fair value, Beginning balance | $ / shares	$ 5.03
Weighted average grant date fair value, Granted | $ / shares	4
Weighted average grant date fair value, Released | $ / shares	4.89
Weighted average grant date fair value, Cancelled/forfeited | $ / shares	4.75
Weighted average grant date fair value, Ending balance | $ / shares	$ 4.40
Restricted Stock Units (RSUs)
Restricted Common Stock
Unvested balance, Beginning balance | shares	1,092,682
Granted | shares	1,113,964
Unvested restricted common stock, Shares, Released | shares	(393,805)
Unvested restricted common stock, Shares, Forfeited | shares	185,500
Unvested balance, Ending balance | shares	1,627,341

Stock-Based Awards - Stock-Base

Stock-Based Awards - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock-Based Awards
Stock-based compensation expense	$ 17,825	$ 16,964	$ 14,978
Unrecognized stock-based compensation cost	$ 16,537
Weighted average period of unrecognized stock-based compensation cost expected to be recognized	2 years 7 days
Research and development expense
Stock-Based Awards
Stock-based compensation expense	$ 4,508	4,166	3,750
Selling and marketing expense
Stock-Based Awards
Stock-based compensation expense	3,682	4,684	4,014
General and administrative expense
Stock-Based Awards
Stock-based compensation expense	$ 9,635	$ 8,114	$ 7,214

Stock-Based Awards - Addition_2

Stock-Based Awards - Additional Information (Details)			12 Months Ended
	Dec. 17, 2023 shares	Jun. 18, 2021 shares	Dec. 31, 2023 item $ / shares shares	Dec. 31, 2014 shares	Dec. 31, 2022 item
Stock-Based Awards
Shares issuable under options, granted (in shares)			3,542,491
Exercise price (in dollars per share) | $ / shares			$ 4
Common Stock
Stock-Based Awards
Issuance of common stock upon public offering, net of issuance costs, shares	35,420,000		36,934,926
2021 Incentive Plan
Stock-Based Awards
Number of shares of common stock available for issuance			6,219,678
2019 Inducement Plan
Stock-Based Awards
Number of shares of common stock available for issuance			551,375
2014 Employee Stock Purchase Plan | Common Stock
Stock-Based Awards
Number of shares of common stock available for issuance			398,784
2014 and 2006 Stock Incentive Plan
Stock-Based Awards
Granted (in shares)				0
2021 and 2014 Stock Incentive Plan
Stock-Based Awards
Granted (in shares)		0
2014 Stock Incentive Plan
Stock-Based Awards
Number of stock based compensation plans | item			4		4
Restricted Stock Units (RSUs)
Stock-Based Awards
Granted (in shares)			1,113,964

Employee Benefits - Additional

Employee Benefits - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Benefits
Contributions to savings plan	$ 625	$ 593	$ 493

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Income tax benefit	$ 0	$ 0	$ 0
Reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate
Federal statutory income tax rate	21%	21%	21%
Research and development tax credits	3.60%	5.40%	35.90%
State taxes, net of federal benefit	2%	2.60%	19.30%
Stock-based compensation	(2.30%)	(2.10%)	(7.80%)
Derivative liability		2.70%	244.70%
Change in tax rate	(0.40%)	1.40%	(8.40%)
Other	(0.20%)	(0.10%)	(3.80%)
Change in valuation allowance	(23.70%)	(30.90%)	(300.90%)
Effective income tax rate

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 120,971	$ 113,801
Tax credit carryforwards	22,597	19,653
Capitalized start-up costs	121	255
Capitalized research and development expenses, net - Sec. 59e	3,570	5,773
Capitalized research and development expenses, net Sec. 174	19,491	10,046
Operating lease liabilities	1,970	2,422
Derivative liability	6,981	1,497
Stock-based Awards	10,443	8,783
Accrued expenses and other	8,433	6,274
Total gross deferred tax assets	194,577	168,504
Valuation allowance	(183,737)	(164,546)	$ (142,637)	$ (123,020)
Net deferred tax assets	10,840	3,958
Operating lease right of use assets	(1,507)	(1,895)
Convertible Notes	(6,603)	(2,063)
Barings Credit Facility	(2,730)
Total deferred tax liabilities	$ (10,840)	(3,958)
Net deferred tax assets

Income Taxes - Changes in Valua

Income Taxes - Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Valuation allowance as of beginning of year	$ 164,546	$ 142,637	$ 123,020
Increase recorded to income tax provision	19,191	21,909	19,617
Valuation allowance as of end of year	$ 183,737	$ 164,546	$ 142,637

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Federal
Net operating loss carryforwards
Net operating loss carryforwards	$ 482,561
Net operating loss carryforward that can be carried forward indefinitely	356,757
State
Net operating loss carryforwards
Net operating loss carryforwards	$ 343,803

Income Taxes - Tax Credit Carry

Income Taxes - Tax Credit Carryforwards (Details) - Research and Development $ in Thousands	Dec. 31, 2023 USD ($)
Federal
Tax credit carryforwards
Tax credit carryforwards	$ 15,383
State
Tax credit carryforwards
Tax credit carryforwards	$ 8,794

Income Taxes - Other (Details)

Income Taxes - Other (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Unrecognized tax benefits	$ 0	$ 0	$ 0

Net Loss Per Share - Basic (Det

Net Loss Per Share - Basic (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Basic and diluted net loss per share attributable to common stockholders
Net loss attributable to common stockholders	$ (80,736)	$ (71,038)	$ (6,553)
Weighted average common shares outstanding, basic (in shares)	79,827,362	76,875,035	76,392,870
Net loss per share, basic (in dollars per share)	$ (1.01)	$ (0.92)	$ (0.09)

Net Loss Per Share - Diluted Ne

Net Loss Per Share - Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of net loss attributable to common stockholders for basic and diluted net loss per share
Net loss attributable to common stockholders, basic	$ (80,736)	$ (71,038)	$ (6,553)
Interest expense on Convertible Notes	4,172	4,596	4,409
Gain on extinguishment of debt	(14,907)
Change in fair value of derivative liability	4,502	(13,841)	(78,121)
Net loss attributable to common stockholders, diluted	$ (86,969)	$ (80,283)	$ (80,265)
Weighted average common shares outstanding, basic (in shares)	79,827,362	76,875,035	76,392,870
Shares issuable upon conversion of Convertible Notes, as if converted (in shares)	5,769,232	5,769,232	5,769,232
Weighted average common shares outstanding, diluted (in shares)	85,596,594	82,644,267	82,162,102
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (1.02)	$ (0.97)	$ (0.98)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Antidilutive Securities, Excluded from Computation of Diluted Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Loss Per Share
Total common stock equivalents	17,764,132	14,762,393	10,934,828
Options to Purchase Common Stock
Net Loss Per Share
Total common stock equivalents	16,136,791	13,669,711	10,934,828
Restricted stock units
Net Loss Per Share
Total common stock equivalents	1,627,341	1,092,682

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transactions
Accounts payable	$ 4,389	$ 5,123
Accrued expenses	$ 28,666	24,097
Total grant date fair value of stock-based awards granted	$ 4
Liabilities	$ 0	0
Specialty Pharma
Related Party Transactions
Expenses incurred	0	0	$ 155
WilmerHale | Chief Business Officer
Related Party Transactions
Expenses incurred	1,472	959	1,396
Accounts payable	298	0
Accrued expenses	0	24
Heier Consulting LLC | Related Party
Related Party Transactions
Accounts payable	6	3
Accrued expenses	$ 0	0
Total grant date fair value of stock-based awards granted	$ 96
Heier Consulting LLC | Related Party | Service
Related Party Transactions
Expenses incurred	$ 32	$ 24	$ 0

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands

1 Months Ended

12 Months Ended

Feb. 26, 2024

Feb. 21, 2024

Feb. 20, 2024

Jan. 01, 2024

Dec. 17, 2023

Jan. 01, 2023

Dec. 10, 2020

Jan. 01, 2015

Feb. 29, 2024

Dec. 31, 2023

Dec. 31, 2021

Feb. 19, 2024

Dec. 31, 2022

Mar. 01, 2019

Subsequent Events

Common stock, par value

$ 0.0001

$ 0.0001

$ 0.0001

Issuance costs from the issuance of common stock

$ 275

Shares issuable under options, granted (in shares)

3,542,491

Restricted Stock Units (RSUs)

Subsequent Events

Granted (in shares)

1,113,964

Common Stock

Subsequent Events

Number of shares issued

35,420,000

36,934,926

Additional shares of common stock that may be issued under the plan

207,402

2014 Employee Stock Purchase Plan | Common Stock

Subsequent Events

Additional shares of common stock that may be issued under the plan

207,402

Additional number of shares of common stock , percentage

0.50%

Additional number of shares authorized for issuance

207,402

2019 Inducement Plan

Subsequent Events

Number of shares of common stock authorized for issuance

1,054,000

Additional number of shares authorized for issuance

554,000

Subsequent Event

Subsequent Events

Gross proceeds from common stock

$ 325,000

Subsequent Event | 2014 Employee Stock Purchase Plan | Common Stock

Subsequent Events

Additional number of shares authorized for issuance

207,402

Subsequent Event | 2019 Inducement Plan

Subsequent Events

Number of shares of common stock authorized for issuance

3,804,000

1,054,000

Shares issuable under options, granted (in shares)

1,527,019

Subsequent Event | 2019 Inducement Plan | Restricted Stock Units (RSUs)

Subsequent Events

Granted (in shares)

935,279

Subsequent Event | Securities Purchase Agreement

Subsequent Events

Number of shares issued

32,413,560

Common stock, par value

$ 0.0001

Common stock, price per share

$ 7.52

Gross proceeds from common stock

$ 325,000,000

Subsequent Event | Securities Purchase Agreement | Pre-Funded Warrants

Subsequent Events

Number of shares callable by warrants

10,805,957

Offering price of warrants

$ 7.519

Weighted average exercise price to purchase common stock

$ 0.001

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (80,736)	$ (71,038)	$ (6,553)

Insider Trading Arrangements

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