scPharmaceuticals (SCPH) 10-K 13 Mar 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Mar. 12, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	SCPH
Entity Registrant Name	SCPHARMACEUTICALS INC.
Entity Central Index Key	0001604950
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.0001
Security Exchange Name	NASDAQ
Entity File Number	001-38293
Document Financial Statement Error Correction [Flag]	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5184075
Entity Address, Address Line One	25 Mall Road
Entity Address, Address Line Two	Suite 203
Entity Address, City or Town	Burlington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01803
City Area Code	617
Local Phone Number	517-0730
Document Annual Report	true
Document Transition Report	false
Auditor Name	RSM US LLP
Auditor Location	Boston, Massachusetts
Auditor Firm ID	49
Entity Common Stock, Shares Outstanding		36,054,409
Entity Public Float			$ 274,229,184
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE None.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 46,814	$ 71,061
Short-term investments	29,199	47,125
Restricted cash		182
Accounts receivable	4,489
Inventory	8,840	1,230
Prepaid expenses	2,436	2,282
Deposits and other current assets	1,160	1,428
Total current assets	92,938	123,308
Property and equipment, net	58	54
Right-of-use lease assets - operating, net	1,401	566
Deposits and other assets	82	267
Total assets	94,479	124,195
Current liabilities
Accounts payable	4,001	1,518
Accrued expenses	8,901	5,289
Lease obligation - operating, short-term	176	567
Other current liabilities	56	42
Total current liabilities	13,134	7,416
Term loan, long-term	38,811	36,794
Derivative liability	3,857	7,517
Lease obligation - operating, long-term	1,282	7
Other liabilities	177	28
Total liabilities	57,261	51,762
Commitments and contingencies (Note 13)
Stockholders’ Equity
Preferred stock, $0.0001 par value; 10,000,000 shares authorized and no shares issued and outstanding
Common stock; $0.0001 par value; 150,000,000 shares authorized at December 31, 2023; 34,257,916 and 35,968,510 shares issued and outstanding at December 31, 2022 and December 31, 2023, respectively	4	3
Additional paid-in capital	318,561	298,934
Accumulated deficit	(281,346)	(226,536)
Accumulated other comprehensive (loss) income	(1)	32
Total stockholders’ equity	37,218	72,433
Total liabilities and stockholders’ equity	$ 94,479	$ 124,195

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	35,968,510	34,257,916
Common stock, shares outstanding	35,968,510	34,257,916

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Product revenues, net	$ 13,593
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:ProductMember
Operating expenses:
Cost of product revenues	$ 3,811
Research and development	11,809	$ 15,533
Selling, general and administrative	53,369	20,624
Total operating expenses	68,989	36,157
Loss from operations	(55,396)	(36,157)
Other income	3,605	1,418
Interest income	5,104	1,203
Interest expense	(8,123)	(3,302)
Net loss	$ (54,810)	$ (36,838)
Net loss per share, basic	$ (1.42)	$ (1.3)
Net loss per share, diluted	$ (1.42)	$ (1.3)
Weighted --average common shares outstanding, basic	38,513,747	28,358,502
Weighted--average common shares outstanding, diluted	38,513,747	28,358,502
Other comprehensive loss:
Unrealized gain (loss) on short-term investments	$ (33)	$ 33
Comprehensive loss	$ (54,843)	$ (36,805)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Offering	Common Stock	Common Stock At The Market Offering	Additional Paid-in Capital	Additional Paid-in Capital At The Market Offering	Accumulated Deficit	Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2021	$ 56,470		$ 3		$ 246,166		$ (189,698)	$ (1)
Beginning Balance, Shares at Dec. 31, 2021			27,366,707
Net loss	(36,838)						(36,838)
Issuance of common stock under at-the-market offering, net of issuance costs		$ 1,114				$ 1,114
Issuance of common stock under at-the-market offering, net of issuance costs, Shares				181,553
Issuance of common stock and pre-funded warrants in common stock offering, net of issuance costs	46,645				46,645
Issuance of common stock and pre-funded warrants in common stock offering, net of issuance costs, Shares			6,620,000
Issuance of common stock upon exercise of stock options	$ 44				44
Issuance of common stock upon exercise of stock options, Shares	11,756		11,756
Issuance of common stock purchased through employee stock purchase plan	$ 173				173
Issuance of common stock purchased through employee stock purchase plan, Shares			45,938
Vesting of restricted stock	(54)				(54)
Vesting of restricted stock, Shares			31,962
Issuance of warrants	2,008				2,008
Stock-based compensation	2,838				2,838
Unrealized gain (loss) on short term investments	33							33
Ending Balance at Dec. 31, 2022	72,433		$ 3		298,934		(226,536)	32
Ending Balance, Shares at Dec. 31, 2022			34,257,916
Net loss	(54,810)						(54,810)
Issuance of common stock under at-the-market offering, net of issuance costs		$ 13,960	$ 1			$ 13,959
Issuance of common stock under at-the-market offering, net of issuance costs, Shares				1,544,490
Issuance of common stock upon exercise of stock options	$ 354				354
Issuance of common stock upon exercise of stock options, Shares	100,322		75,979
Issuance of common stock purchased through employee stock purchase plan	$ 458				458
Issuance of common stock purchased through employee stock purchase plan, Shares			90,125
Stock-based compensation	4,856				4,856
Unrealized gain (loss) on short term investments	(33)							(33)
Ending Balance at Dec. 31, 2023	$ 37,218		$ 4		$ 318,561		$ (281,346)	$ (1)
Ending Balance, Shares at Dec. 31, 2023			35,968,510

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (54,810,000)	$ (36,838,000)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation expense	24,000	37,000
Loss on disposal of property and equipment	11,000
Reduction in carrying value of operating right-of-use lease assets	602,000	431,000
Accretion on short-term investments	(2,112,000)	(244,000)
Stock-based compensation	4,856,000	2,838,000
Non-cash interest expense	2,166,000	884,000
Fair value adjustment to derivative liability	(3,660,000)	(1,335,000)
Changes in operating assets and liabilities
Accounts receivable	(4,489,000)
Inventory	(7,609,000)	(1,230,000)
Prepaid expenses and other assets	221,000	(887,000)
Accounts payable, accrued expenses and other liabilities	5,556,000	1,767,000
Net cash flows used in operating activities	(59,244,000)	(34,577,000)
Cash flows from investing activities
Purchases of property and equipment	(40,000)	(21,000)
Maturities of short-term investments	70,600,000	21,700,000
Purchases of short-term investments	(50,595,000)	(67,538,000)
Net cash flows (used in) provided by investing activities	19,965,000	(45,859,000)
Cash flows from financing activities
Proceeds from common stock offering, net of underwriter discounts and offering costs		46,645,000
Proceeds from at-the-market offering, net	14,038,000	1,120,000
Proceeds from the exercise of stock options	354,000	44,000
Proceeds from employee stock purchase plan	458,000	173,000
Proceeds from term loan		47,301,000
Principal payments on term loan		(17,500,000)
Payment Of Term Loan Final Fee		(500,000)
Settlement of restricted stock units for tax withholding obligations		(54,000)
Net cash flows provided by financing activities	14,850,000	77,229,000
Net decrease in cash	(24,429,000)	(3,207,000)
Cash, cash equivalents and restricted cash, beginning of year	71,243,000	74,450,000
Cash, cash equivalents and restricted cash, end of year	46,814,000	71,243,000
Supplemental cash flow information
Interest paid	5,940,000	2,555,000
Taxes paid	248,000	190,000
Supplemental disclosure of non-cash activities
Operating right-of-use asset received in exchange for lease obligations	1,437,000
Transfer of issuance costs from other noncurrent assets to equity	$ 79,000	$ 6,000

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (54,810)	$ (36,838)

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

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Description of Business scPharmaceuticals LLC was formed as a Limited Liability Company under the laws of the State of Delaware on February 19, 2013. On March 24, 2014, scPharmaceuticals LLC was converted to a Delaware Corporation and changed its name to scPharmaceuticals Inc. (“the Company”). The Company is a pharmaceutical company focused on developing and commercializing products that have the potential to optimize the delivery of infused therapies, advance patient care and reduce healthcare costs. The Company’s strategy is designed to enable the subcutaneous administration of therapies that have previously been limited to intravenous (“IV”) delivery. The Company’s headquarters and primary place of business is Burlington, Massachusetts. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) and have been prepared on a basis which assumes that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary, scPharmaceuticals Securities Corporation. All significant intercompany balances and transactions have been eliminated in consolidation. Liquidity At December 31, 2023 , the Company had cash, cash equivalents and short-term investments of $ 76.0 million and working capital of $ 79.8 million. During the year ended December 31, 2023 , the Company incurred a net loss totaling $ 54.8 million and used cash in operating activities totaling $ 59.2 million. The Company expects to continue to incur losses and use cash in operating activities in 2024. In October 13, 2022 (the "closing date"), the Company entered into a Credit Agreement and Guaranty (the "Oaktree Agreement") with, among others, the lenders from time to time party thereto (the "Lenders") and Oaktree Fund Administration, LLC, in its capacity as administrative agent for the Lenders (Note 10). In November 2022, the Company completed an underwritten public offering with net proceeds of $ 46.6 million (Note 11). In addition, the Company currently has an at-the-market offering program with Cowen and Company, LLC that has $ 34.5 million in capacity remaining at December 31, 2023 (Note 11). The Company believes that, based on its current development plans and activities, its resources will be sufficient to satisfy its liquidity requirements for more than one year from the issuance date of these consolidated financial statements.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include the determination of fair value of financial instruments, accounting policies for revenue recognition, accruals related to development costs and clinical activities, and the establishment of the tax valuation allowance. Actual results could differ from those estimates. Foreign Currency Transactions The functional currency of the Company is the U.S. dollar. Accordingly, gains and losses resulting from translating transactions denominated in currencies and balances of assets and liabilities outstanding at the balance sheet date, other than U.S. dollars, are included in net loss in the Statements of Operations and Comprehensive Loss. Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company places its cash and cash equivalents with institutions with high credit quality. However, at certain times such cash and cash equivalents may be in excess of Federal Deposit Insurance Corporation and Securities Investor Protection Corporation insurance limits. The Company has not experienced any losses with respect to these accounts. As of December 31, 2022 , the Company classified $ 182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 13). As of December 31, 2023, this amount was reclassified to deposits as the funds were transferred upon the cancelation of its letter of credit. Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, December 31, Cash and cash equivalents $ 71,061 $ 46,814 Restricted cash 182 - Cash, cash equivalents and restricted cash $ 71,243 $ 46,814 Accounts Receivable Accounts receivable are recorded net of any estimated expected credit losses. The Company's measurement of expected credit losses is based on relevant information about past events, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. To date, expected credit losses have not been material. Concentration of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and short-term investments. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s short-term investments consist of commercial paper, United States Treasury securities, corporate bonds and United States Government Agency securities. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to hold a minimum rating, thereby reducing credit risk exposure. Customer and Supplier Concentration The Company has a limited number of specialty pharmacy customers and distributors. As of December 31, 2023, 3 customers represent 99 % of accounts receivable. For the year ended December 31, 2023, 2 customers represent 93 % of revenue. The Company depends on suppliers for raw materials, API, and other components that are subject to stringent FDA requirements. Some of these materials may only be available from one or a limited number of sources. Establishing additional or replacement suppliers may take a substantial period of time, as suppliers must be approved by the FDA. If the Company is unable to secure, on a timely basis, sufficient quantities of the materials it depends on to manufacture its products, it could have a materially adverse effect on the Company's business, financial condition and results of operations. Investments The Company invests excess cash balances in available-for-sale debt securities. The Company determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company reports available-for-sale investments at fair value at each balance sheet date and includes any unrealized gains and losses in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses are determined using the specific identification method and are included in other income (expense). If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the intention to sell and, if so, marks the investment to market through a charge to the Company’s consolidated statements of operations and comprehensive loss. Inventory Inventory is stated at the lower of cost and net realizable value and consists of raw materials, work-in-process and finished goods. The Company began capitalizing inventory costs following U.S. Food and Drug Administration ("FDA") approval of FUROSCIX on October 7, 2022. Inventory is sold on a first in, first out ("FIFO") basis. The Company periodically reviews inventory for expiry and obsolescence and writes it down accordingly, if necessary. Prior to FDA approval of FUROSCIX, the Company expensed all inventory-related costs, including that used for clinical development, to research and development ("R&D") costs in the period incurred. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) lease assets, current portion of lease obligations, and long term lease obligations on the Company’s balance sheets. ROU lease assets represent the Company’s right to use an underlying asset for the lease term and lease obligations represent the Company’s obligation to make lease payments arising from the lease. Operating ROU lease assets and obligations are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU lease asset excludes lease incentives. The Company’s lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Debt Issuance Costs Debt issuance costs are amortized to interest expense using the effective interest rate method over the term of the debt. Debt issuance costs paid to the lender and third parties are reflected as a discount to the debt in the consolidated balance sheets . Revenue Recognition The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of Accounting Standards Codification ("ASC") Topic 606, Revenue from Contracts with Customer (“Topic 606”), the Company 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 the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied. The Company has identified one performance obligation, the delivery of FUROSCIX to its customers. The Company has not incurred any incremental costs associated with obtaining contracts with customers. The Company’s revenues consist solely of the sale of FUROSCIX to customers in the United States. Product Net Sales FUROSCIX was approved by the FDA on October 7, 2022. The Company launched sales of FUROSCIX in the first quarter of 2023 and its customers consist of specialty pharmacies (“SPs”) and specialty distributors ("SDs"). The Company recognizes revenue from product sales at a point in time, typically upon receipt of product at the SPs and SDs, the date at which the rights, title, interest and risk of loss are transferred. Revenues from product sales are recorded at the net sales price, which includes estimates of variable consideration that result from (a) sales discounts, (b) rebates (c) co-pay assistance, and (d) product returns. Reserves are established for the estimates of variable consideration based on the amounts earned or to be claimed on the related sales. The reserves for variable consideration are reflected as either as a reduction to the related account receivable or as an accrued liability, depending on how the consideration is settled. The amount of variable consideration that is included in the transaction price may be constrained and is included in net product revenues only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company's estimates. If actual results vary from its estimates, the Company adjusts these estimates, which would affect net product revenue and earnings in the period such variances become known. Sales Discounts : Sales discounts are agreed-upon discounts, from negotiated contracts, taken directly off the Company’s sales invoices. Sales discounts are recorded as an offset to revenue based on contractual terms at the time revenue from the sale is recognized. Rebates : Allowance for rebates include mandated discounts under the Medicaid Drug Rebate Program and the Medicare Part D prescription drug benefit, TRICARE program and contractual rebates with commercial payers. Rebates are amounts owed after the final dispensing of the product to a benefit plan participant and are based upon contractual agreements or statutory requirements. The allowance for rebates is based on contracted or statutory discount rates and expected utilization by benefit plan participants. The Company’s estimates for expected utilization of rebates are based on utilization data received from the SPs since product launch. Rebates are generally invoiced and paid in arrears so that the accrual balance consists of an estimate of the amount expected to be incurred for the current quarter’s activity, plus an accrual balance for prior quarters’ unpaid rebates. If actual future rebates vary from estimates, the Company may need to adjust prior period accruals, which would affect revenue in the period of adjustment. Co-Payment Assistance: The Company offers co-payment assistance to commercially insured patients meeting certain eligibility requirements. Co-payment assistance is accrued at the time of product sale to SPs based on estimated patient participation and average co-pay benefit to be paid per a claim. The Company’s estimated amounts are compared to actual program participation and co-pay amounts paid using data provided by third-party administrators. If actual amounts differ from the original estimates the assumptions being applied are updated and adjustment for prior period accruals will be adjusted in the current period. Product Returns: Consistent with industry practice, the Company offers SPs and SDs limited product return rights for damages, shipment errors, and expiring product, provided that the return is within a specified period around the product expiration date as set forth in the applicable individual distribution agreement. The Company does not allow product returns for product that has been dispensed to a patient. As the Company receives inventory reports from the SPs and has the ability to control the amount of product that is sold to the SPs, it is able to make a reasonable estimate of future potential product returns based on this on-hand channel inventory data and sell-through data obtained from the SPs. Currently, sales to SDs are limited and there is no access to on-hand channel inventory or sell through data. As these arrangements mature, the Company will utilize any data that they can provide as part of this analysis. In arriving at its estimate, the Company also considers historical product returns, the underlying product demand, and industry data specific to the specialty pharmaceutical distribution industry. Research and Development Costs Research and development costs are expensed as incurred. Nonrefundable advance payments, if any, for goods or services used in research and development are initially recorded as an asset and then recognized as an expense as the related goods are delivered or services are performed. Research and development expenses include contract services, consulting, salaries, materials and supplies and overhead. Income Taxes The Company accounts for income taxes in accordance with ASC 740 Income Taxes (“ASC 740”) . Deferred tax assets and liabilities are recorded to reflect the impact of temporary differences between amounts of assets and liabilities for financial reporting purposes and such amounts as measured under enacted tax laws. A valuation allowance is required to offset any net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax asset will not be realized. The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. The tax benefits recorded are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming that the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At December 31, 2022 and 2023 , the Company had no such accruals. Stock-Based Compensation Stock-based compensation expense for stock options is recognized based on the grant-date fair value using the Black-Scholes valuation model. Restricted stock units are valued at the fair market value per share of the Company’s common stock on the date of grant. The Company recognizes compensation expense only for those stock-based awards expected to vest after considering expected forfeitures. Cumulative compensation expense is at least equal to the compensation expense for vested awards. Stock-based compensation is recognized on a straight-line basis over the service period of each award. Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s chief executive officer is the CODM, and he uses consolidated financial information in determining how to allocate resources and assess performance. The Company has determined that it operates in one segment. Recently Issued Accounting Standards In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2023-09, Income Taxes ("ASU 2023-09"), requiring entities to provide additional information in the income tax rate reconciliation and additional disclosures about income taxes paid. The new accounting guidance requires entities to disclose in their rate reconciliation table additional categories of information about federal, state and foreign income taxes and to provide more details about the reconciling items in some categories if the items meet a quantitative threshold. This guidance is effective for annual periods beginning after December 15, 2024, and should be applied prospectively, but entities have the option to apply it retrospectively for each period presented. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. The Company is currently evaluating the impact of the adoption of ASU 2023-09 and does not expect adoption to have a material effect on the Company’s consolidated financial statements or disclosures.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss per Share	3. Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period without consideration of dilutive common stock equivalents. Diluted net loss per share is the same as basic net loss per common share, since the effects of potentially dilutive securities are anti-dilutive. Basic and diluted weighted average shares of common stock outstanding include the weighted average effect of outstanding pre-funded warrants for the purchase of shares of common stock for which the remaining unfunded exercise price is $ 0.001 per share. Dilutive common stock equivalents are comprised of unexercised stock options outstanding under the Company’s equity plan, unexercised warrants and unvested restricted stock. The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except shares and per share data): For the year ended December 31, December 31, Net loss $ ( 36,838 ) $ ( 54,810 ) Weighted—average common shares 28,358,502 38,513,747 Net loss per share, basic and diluted $ ( 1.30 ) $ ( 1.42 ) The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive (in common stock equivalent shares): For the year ended December 31, December 31, Stock options to purchase common stock 4,008,177 4,681,326 Warrants to purchase common stock 516,345 516,345 Unvested restricted stock — 368,411 4,524,522 5,566,082

Investments

Investments	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Investments	4. Investments Cash in excess of the Company’s immediate requirements is invested in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. A summary of the Company’s available-for-sale classified investments as of December 31, 2022 and 2023 consisted of the following (in thousands): At December 31, 2022 Investments - Current: Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Commercial paper $ 16,741 $ - $ - $ 16,741 United States Treasury securities 15,768 7 - 15,775 United States Government Agency securities 14,584 25 - 14,609 Total $ 47,093 $ 32 $ - $ 47,125 At December 31, 2023 Investments - Current: Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value United States Treasury securities $ 13,967 $ 2 $ - $ 13,969 Commercial paper 9,427 - ( 2 ) 9,425 Corporate bonds 3,815 - - 3,815 United States Government Agency securities 1,991 - ( 1 ) 1,990 Total $ 29,200 $ 2 $ ( 3 ) $ 29,199 The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of December 31, 2023 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 29,200 $ 29,199 Total $ 29,200 $ 29,199

Inventory

Inventory	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Inventory	5. Inventory The Company's inventory balance consists of the following (in thousands): As of December 31, 2022 2023 Raw materials $ 1,201 $ 4,256 Work-in-process 29 4,188 Finished goods — 396 $ 1,230 $ 8,840 Inventory is stated at the lower of cost and net realizable value and consists of raw materials, work-in-process and

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Purchased property and equipment consist of the following as of December 31, 2022 and 2023 (in thousands): ESTIMATED 2022 2023 Office equipment 5 years $ 6 $ 31 Office furniture 7 years 126 64 Computer equipment 3 years 15 15 Leasehold improvements Life of lease 95 9 242 119 Less: Accumulated depreciation ( 188 ) ( 61 ) Property and equipment, net $ 54 $ 58 Depreciation expense for the years ended December 31, 2022 and 2023 was $ 37,000 and $ 24,000 , respectively, and is included in operating expenses.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Accrued Expenses	7. Accrued Expenses Accrued expenses at December 31, 2022 and 2023 consist of (in thousands): 2022 2023 Employee compensation and related costs $ 2,754 $ 4,375 Sales allowances and related costs - 1,418 Contract research and development 1,827 1,202 Consulting and professional service fees 603 945 Manufacturing costs - 434 Royalty - 249 Inventory in transit - 150 Other 105 128 Total accrued expenses $ 5,289 $ 8,901

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The Company accounts for income taxes in accordance with ASC 740, which requires an asset and liability approach for measuring deferred taxes based on temporary differences between the financial statement and tax bases of assets and liabilities existing at each balance sheet date using enacted tax rates for the years in which taxes are expected to be paid or recovered. The tax benefit arising from the Company’s net loss has been offset by an increase in the valuation allowance. Accordingly, the Company had no net income tax provision or benefit during the years ended December 31, 2022 and 2023 . Components of the net deferred tax assets at December 31, 2022 and 2023 are as follows (in thousands): 2022 2023 Deferred tax assets: Federal net operating loss carryforwards $ 17,252 $ 30,405 State net operating loss carryforwards 4,585 8,216 Research and development tax credits 4,214 4,729 Accrued liabilities 677 1,088 Stock-based compensation 1,329 1,814 Depreciation and amortization 324 3 Capitalized research and development costs 30,976 27,720 Lease liabilities 146 370 Total deferred tax assets 59,503 74,345 Deferred tax liabilities: Right-of-use lease assets ( 144 ) ( 355 ) Other ( 273 ) ( 833 ) Total deferred tax liabilities $ ( 417 ) $ ( 1,188 ) Valuation allowance $ ( 59,086 ) $ ( 73,157 ) Net deferred tax assets $ — $ — At December 31, 2023 , the Company had available federal net operating loss carryforwards of $ 17.5 million, which expire at various dates through 2037 , and $ 127.3 million, which may be carried forward indefinitely. At December 31, 2023 , the Company had available state net operating loss carryforwards of $ 147.1 million, which expire at various dates through 2043 , and $ 1.8 million, which may be carried forward indefinitely. In assessing the realizability of net deferred tax assets, management considers whether it is more likely than not that the net deferred tax assets will be realized. The ultimate realization of net deferred tax assets is dependent upon the generation of future taxable income during the periods in which temporary differences representing future deductible amounts become deductible. Management has established a full valuation allowance against the net deferred tax assets at December 31, 2022 and 2023 since it is more likely than not that these future tax benefits will not be realized. During 2023 , the valuation allowance increased by $ 14.1 million. A reconciliation of the beginning and ending amount of the valuation allowance is as follows (in thousands): 2022 2023 Beginning valuation allowance $ 51,399 $ 59,086 Current year - increases 7,687 14,071 Ending valuation allowance $ 59,086 $ 73,157 At December 31, 2023, the Company had federal and state research and development credit carryforwards of $ 3.9 million and $ 1.0 million, respectively. The net credit carryforwards may be used to offset future income taxes and expire at various dates through 2043 . Under the provisions of the Internal Revenue Code ("IRC"), the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 %, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. The Company had performed an IRC 382 study during 2017 which resulted in identifying an ownership change had occurred on the initial public offering date of 11/21/2017. For these reasons, in the event the Company experiences a change of control, they may not be able to utilize a material portion of the net operating losses or research and development credit carryforwards even if they attain profitability. The Tax Cuts and Jobs Act ("TCJA") requires taxpayers to capitalize and amortize research and experimental ("R&D") expenditures under section 174 for tax years beginning after December 31, 2021. These rules became effective for the Company during the year ended December 31, 2022. As a result, for tax purposes, the Company has capitalized R&D costs of $ 13.6 million and $ 11.6 million for the years ended December 31, 2022 and 2023, respectively. The Company will amortize these costs for tax purposes over 5 years if the R&D was performed in the U.S. and over 15 years if the R&D was performed outside the U.S. A reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the consolidated financial statements at December 31, 2022 and 2023 are as follows: 2022 2023 Federal income tax at statutory rate 21.00 % 21.00 % State income tax, net of federal benefit 4.28 % 8.65 % Research and development credits 1.39 % 0.96 % Book compensation related to stock options ( 0.80 )% ( 1.00 )% Change in income tax rate ( 4.93 )% ( 3.16 )% Other ( 0.09 )% ( 0.01 )% Increase in valuation allowance ( 20.87 )% ( 25.68 )% Permanent differences — ( 0.76 )% Effective tax rate ( 0.02 )% — % The Company files tax returns in the United States, Massachusetts and other states. The tax years 2019 through 2023 remain open to examination by major taxing jurisdictions to which the Company is subject, which are primarily the United States federal and Massachusetts. Carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service or state tax authorities if they have or will be used in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years. The Company recognizes both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company has not recorded any interest or penalties on any unrecognized tax benefits since its inception. A reconciliation of the beginning and ending amount of uncertain tax benefits is as follows (in thousands): 2022 2023 Beginning uncertain tax benefits $ 977 $ 1,106 Prior year - increases — 28 Current year - increases 129 102 Ending uncertain tax benefits $ 1,106 $ 1,236

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	9. Fair Value of Financial Instruments The FASB ASC Topic, Fair Value Measurements and Disclosures ( “ASC 820” ), provides a fair value hierarchy, which classifies fair value measurements based on the inputs used in measuring fair value. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below: Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and observable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying values of the Company’s cash and restricted cash, prepaid expenses and deposits approximate their fair values due to their short-term nature. The carrying value of the Company’s term loan payable was considered a reasonable estimate of fair value because the Company’s interest rate is near current market rates for instruments with similar characteristics. The following tables summarize the Company’s assets and liabilities that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): As of December 31, 2022 TOTAL Quoted Prices Significant Significant Assets: Cash equivalents $ 65,875 $ 65,875 $ — $ — Total cash equivalents 65,875 65,875 — — Commercial paper 16,741 — 16,741 — United States Treasury securities 15,775 15,775 — — United States Government Agency securities 14,609 — 14,609 — Investments 47,125 15,775 31,350 — Total $ 113,000 $ 81,650 $ 31,350 $ — Liabilities: Derivative liability $ 7,517 $ — $ — $ 7,517 Total $ 7,517 $ — $ — $ 7,517 As of December 31, 2023 TOTAL Quoted Prices Significant Significant Assets: Cash equivalents $ 44,202 $ 44,202 $ — $ — Total cash equivalents 44,202 44,202 — — United States Treasury securities 13,969 13,969 — — Commercial paper 9,425 — 9,425 — Corporate bonds 3,815 — 3,815 — United States Government Agency securities 1,990 — 1,990 — Investments 29,199 13,969 15,230 — Total $ 73,401 $ 58,171 $ 15,230 $ — Liabilities: Derivative liability $ 3,857 $ — $ — $ 3,857 Total $ 3,857 $ — $ — $ 3,857 Changes in the fair value of the Company’s Level 3 derivative liability for the year ended December 31, 2023 are as follows: At December 31, 2022 $ 7,517 Change in fair value of derivative liability ( 3,660 ) At December 31, 2023 $ 3,857 The Oaktree Agreement contains embedded derivatives requiring bifurcation as a derivative instrument. The derivative liability related to the term loan is recorded and accounted for separately in the consolidated financial statements as one compound derivative liability, see Note 10 for additional details. The fair value of the embedded derivative liabilities associated with the term loan was estimated using a hybrid between the discounted cash flow and Monte Carlo simulation methods. This involves significant Level 3 inputs and assumptions including (i) the estimated probability and timing of a change in control and (ii) the probability-weighted net sales of FUROSCIX. A summary of quantitative information about significant unobservable inputs (Level 3 inputs) used in measuring the Company's derivative liability that are categorized within Level 3 of the fair value hierarchy is as follows: December 31, December 31, Net sales discount rate 22.3 % 20.7 % Net sales volatility 80.0 % 70.0 % Risk-free rate 4.0 % 3.9 % Recovery rate 80.0 % 80.0 %

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt	10. Debt The following table presents the carrying value of the Company's debt balance as of December 31, 2022 and 2023 (in thousands): DECEMBER 31, DECEMBER 31, Face value of term loans $ 50,000 $ 50,000 Unamortized debt discount ( 13,206 ) ( 11,189 ) Total debt, net $ 36,794 $ 38,811 Less: short-term debt — — Long-term debt $ 36,794 $ 38,811 Oaktree Agreement On October 13, 2022 (“Closing Date”), the Company entered into a Credit Agreement and Guaranty (the “Oaktree Agreement”) with Oaktree Fund Administration, LLC as administrative agent, and the lenders party thereto (collectively “Oaktree”) to borrow up to $ 100.0 million in three tranches with a maturity date of October 13, 2027 . The first tranche of $ 50.0 million was drawn immediately, with $ 9.8 million of the proceeds used to repay in full the outstanding loan and fees under the 2019 Loan Agreement with SLR Investment Corp. and Silicon Valley Bank and $ 2.7 million in fees and expenses incurred in connection with the financing, leaving $ 37.5 million in available proceeds from the first tranche. The ability to draw the remaining $ 50.0 million is contingent upon reaching certain net sales revenue milestone targets prior to September 30, 2024 and December 31, 2024, respectively. The term loan initially bears interest at the three-month term Secured Overnight Financing Rate (“SOFR”) plus an applicable margin of 8.75 % (with a SOFR floor of 1.00 % and a 3.00 % cap). Once FUROSCIX achieves at least $ 100.0 million in trailing 12-month net sales, the applicable margin will step down to 8.25 %. The Company is required to make quarterly interest-only payments until the third anniversary of the Closing Date, after which the Company is required to make quarterly amortizing payments, with the remaining balance of the principal plus accrued and unpaid interest due at maturity. In connection with entering into the Oaktree Agreement, the Company granted warrants to Oaktree to purchase up to an aggregate of 516,345 shares of the Company’s common stock at an exercise price of $ 5.40 per share. Upon inception, the Company evaluated the warrants and determined that they met all the requirements for equity classification under ASC 815. This transaction was accounted for as a detachable warrant at its fair value, using the relative fair value method, which is based on a number of unobservable inputs and is recorded as an increase to additional paid-in-capital on the consolidated statement of stockholder’s equity. The relative fair value of the warrants, $ 2.0 million, was reflected as a discount to the term loan and will be amortized over the life of the term loan using the effective interest method. The Company used the Black-Scholes option pricing model to determine the fair value of the warrants. Assumptions included the fair market value per share of common stock on the valuation date of $ 5.50 , the exercise price per warrant equal to $ 5.40 , the expected volatility of 77 %, the risk-free interest rate of 4.11 %, the contractual term of 7 years and the absence of a dividend. The warrants are immediately exercisable and the exercise period expires on October 13, 2029. The Company identified a number of embedded derivatives that require bifurcation from the term loan and that were separately accounted for in the consolidated financial statements as one compound derivative liability. Certain of these embedded features include contingent interest rate reset upon event of default, contingent put options, including change in control and going concern provisions, and additional costs as a result of changes in law. These embedded features met the criteria requiring these to be bifurcated because they were not clearly and closely related to the host instrument in accordance with ASC 815-15 and the derivative liability is presented separately in the consolidated balance sheets as of December 31, 2022 and 2023. The fair value of the embedded derivative liabilities associated with the term loan was estimated using a hybrid between the discounted cash flow and Monte Carlo simulation methods. This involves significant Level 3 inputs and assumptions including an estimated probability and timing of a change in control. The Company re-evaluates this assessment each reporting period and any changes in estimated fair value is recorded as other income (expense). The initial recognition of the embedded derivative liability upon issuance of the Term Loan was $ 8.9 million. At December 31, 2022 and 2023 , the fair value of the embedded derivative liability was $ 7.5 million and $ 3.9 million, respectively. In connection with the issuance of the term loan, the Company recorded a debt discount of $ 13.6 million, inclusive of debt issuance costs, the derivative liability and the relative fair value of the warrants. The discount will be amortized over the life of the term loan using the effective interest method. For the years ended December 31, 2022 and 2023 , the Company recorded $ 383,000 and $ 2.0 million, respectively, related to the amortization of the debt discount associated with the Oaktree Agreement. Prepayments of the term loan, in whole or in part, will be subject to a prepayment fee which declines each year until the fourth anniversary date of the Closing Date, after which no prepayment fee is required. The Company is also required to pay an exit fee upon any payment or prepayment equal to 2.0 % of the aggregate principal amount of the loans funded under the Oaktree Agreement. The Company recorded an additional debt discount of $ 1.0 million related to the exit fee. For the years ended December 31, 2022 and 2023 , the Company recorded $ 28,000 and $ 149,000 , respectively, related to the amortization of the exit fee associated with the Oaktree Agreement. The Oaktree Agreement contains customary representations, warranties and affirmative and negative covenants, including financial covenants requiring the Company to (i) maintain unrestricted cash of at least $ 15.0 million at all times, increasing to $ 20.0 million upon accessing the second tranche of the term loan and (ii) meet minimum quarterly net sales revenue targets. In addition, the Oaktree Agreement contains customary events of default that could cause the Company’s indebtedness to become immediately due and payable. The lenders could declare the Company in default under its debt obligation upon the occurrence of any event that the lenders interpret as having a material adverse effect as defined under the Oaktree Agreement. Upon the occurrence and for the duration of an event of default, an additional interest rate equal to 2.0 % per annum could apply to all obligations owed under the Oaktree Agreement. Among other loan covenant requirements, the Oaktree Agreement also requires the Company to provide an audit opinion of its annual financial statements not subject to any "going concern" or like qualification or exception. SLR Investment Corp. and Silicon Valley Bank Term Loan In May 2017, the Company entered into a loan and security agreement (the “2017 Loan Agreement”), with SLR Investment Corp. (f/k/a Solar Capital Ltd.) and Silicon Valley Bank, (together, the “Lenders”) for $ 10.0 million. The 2017 Loan Agreement had a maturity date of May 1, 2021 . Debt issuance costs for the 2017 Loan Agreement were to be amortized to interest expense over the remaining term of the 2017 Loan Agreement using the effective-interest method. In September 2019, the Company replaced the 2017 Loan Agreement with a new $ 20.0 million term loan with the Lenders (the "2019 Loan Agreement"). The restructured four-year term loan facility allowed for an expansion of the 2017 Loan Agreement. Some of the proceeds from the 2019 Loan Agreement were used to pay off the 2017 Loan Agreement including the final fee of $ 325,000 . The 2019 Loan Agreement extended the term of the credit facility until September 17, 2023 . The payoff of the 2017 Loan Agreement was treated as a modification of the debt. Debt issuance costs for the 2019 Loan Agreement, including unamortized issuance costs for the 2017 Loan Agreement, would be amortized to interest expense over the remaining term of the 2019 Loan Agreement using the effective-interest method. The 2019 Loan Agreement allowed the Company to voluntarily prepay all (but not less than all) of the outstanding principal at any time. A prepayment premium of 3 % or 1 % through the one-year anniversary and the two-year anniversary, respectively, would be assessed on the outstanding principal. After the two-year anniversary, a 0.5 % prepayment premium would be assessed on the outstanding principal. A final payment fee of $ 500,000 was due upon the earlier to occur of the maturity date or prepayment of such borrowings. In connection with the Oaktree Agreement, the Company paid off all unpaid borrowings under the 2019 Loan Agreement on October 13, 2022, including the $ 500,000 final fee and a prepayment premium of $ 46,000 . For the year ended December 31, 2022, the Company recorded $ 341,000 related to the amortization of the debt discount associated with the 2019 Loan Agreement. For the year ended December 31, 2022, the Company recorded $ 132,000 related to the amortization of the final payment fee associated with the 2019 Loan Agreement. As of December 31, 2023, future principal payments due under the Oaktree Agreement are as follows (in thousands): Year ended: December 31, 2024 $ - December 31, 2025 2,500 December 31, 2026 10,000 December 31, 2027 37,500 Total minimum principal payments 50,000

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	11. Stockholders’ Equity Common Stock At December 31, 2022 and 2023 , the Company had 150,000,000 shares of common stock authorized with a par value of $ 0.0001 . There were 34,257,916 and 35,968,510 shares issued and outstanding at December 31, 2022 and 2023, respectively. Voting, dividend and liquidation rights of the holders of the common stock are subject to the Company’s articles of incorporation, corporate bylaws and underlying shareholder agreements. Reserved Shares The Company has reserved 4,681,326 and 368,411 shares of common stock for the exercise of outstanding options to purchase common stock and for the vesting of RSUs respectively. 2021 At-the-Market Issuance Sales Agreement On March 23, 2021, the Company entered into an Open Market Sale Agreement SM (the “2021 ATM Agreement”) with Cowen and Company, LLC (“Cowen”) with respect to an at-the-market offering program (the “2021 ATM Program”) under which the Company could offer and sell shares of its common stock (the “2021 ATM Shares”), having an aggregate offering price of up to $ 50.0 million through Cowen as its sales agent. The offering and sale of 2021 ATM Shares are made pursuant to the Company’s shelf registration statement on Form S-3, which was declared effective by the SEC on April 29, 2021 (the “2021 Registration Statement”). The Company agreed to pay Cowen a commission up to 3.0 % of the gross sales proceeds of such 2021 ATM Shares. The Company incurred $ 273,000 of legal, accounting, and other costs to establish and activate the 2021 ATM Program. During the year ended December 31, 2022, the Company sold a total of 181,553 2021 ATM Shares under the 2021 ATM Agreement, in the open market, at a weighted average gross selling price of $ 6.33 per share for net proceeds of $ 1.1 million. The Company charged $ 6,000 in costs related to establishing and activating the program against additional paid in capital upon issuance of shares in 2022. During the year ended December 31, 2023, the Company sold 1,544,490 2021 ATM Shares under the 2021 ATM Agreement at a weighted average gross selling price of $ 9.32 per share for net proceeds of $ 14.0 million. The Company charged $ 79,000 in costs related to establishing and activating the program against additional paid in capital upon issuance of shares in 2023. Sale of Common Stock In November 2022, the Company completed an underwritten public offering of 6,620,000 shares of its common stock (the “2022 Offering Shares”), pursuant to the 2021 Registration Statement. The 2022 Offering Shares were sold at an offering price of $ 5.25 per share. In addition, a prefunded warrant to purchase up to 2,905,000 shares of common stock at a purchase price of $ 5.249 per underlying share was issued as part of the transaction. The pre-funded warrants were accounted for as equity instruments. Net proceeds of the offering were $ 46.6 million, after deducting underwriting discounts, commissions and offering expenses. Preferred Stock At December 31, 2022 and 2023 , the Company had 10,000,000 shares of preferred stock authorized with a par value of $ 0.0001 and no shares of preferred stock were issued or outstanding.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	12. Stock-Based Compensation Stock Options In October 2017, the board of directors approved the 2017 Stock Option and Incentive Plan (the “2017 Stock Plan”) which became effective in November 2017 , upon the closing of the Company’s IPO. The 2017 Stock Plan will expire in October 2027 . Under the 2017 Stock Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards, RSUs and other stock-based awards. The Company’s 2014 Stock Incentive Plan (the “2014 Stock Plan”) terminated in November 2017 effective upon the completion of the Company’s IPO. No additional options will be granted under the 2014 Stock Plan. At December 31, 2023 , there were 571,095 options outstanding under the 2014 Stock Plan. At December 31, 2023 , there were 7,402,457 shares of the Company’s common stock authorized for issuance under the 2017 Stock Plan, including 366,823 options that have been forfeited from the 2014 Stock Plan. At December 31, 2023 , there were 3,067,473 options available for issuance under the 2017 Stock Plan and 3,926,481 options outstanding and 368,411 RSUs outstanding. On February 1, 2023, the Board of Directors of the Company adopted the 2023 Employment Inducement Award Plan (the "Inducement Plan") and, subject to the adjustment provisions of the Inducement Plan, reserved 500,000 shares of the Company’s common stock for issuance pursuant to equity awards granted under the Inducement Plan. At December 31, 2023, there were 316,250 options available for issuance under the Inducement Plan, and 183,750 options outstanding. Awards granted under the 2017 Stock Plan and the Inducement Plan have a term of ten years . Vesting of awards under the 2017 Stock Plan and the Inducement Plan is determined by the compensation committee of the board of directors but is generally over one to four-year terms. The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions: 2022 2023 Risk-free interest rate 1.67 %— 4.18 % 3.40 %— 4.67 % Expected dividend yield 0 % 0 % Expected life 5.5 — 6.7 years 5.5 — 7.0 years Expected volatility 70 %— 84 % 77 %— 85 % Weighted-average grant date $ 3.18 $ 5.26 Due to the lack of a public market for the trading of the Company’s common stock prior to its initial public offering and the lack of company-specific historical volatility, volatility was estimated using historical volatilities of similar companies. The expected life of the awards is estimated based on the simplified method, which calculates the expected life based upon the midpoint of the term of the award and the vesting period. The Company uses the simplified method because it does not have sufficient option exercise data to provide a reasonable basis upon which to estimate the expected term. The Company has no history of paying dividends nor does management expect to pay dividends over the contractual terms of these options. The risk-free interest rates are based on the United States Treasury yield curve in effect at the time of grant, with maturities approximating the expected life of the stock options. The following table summarizes information about stock option activity during 2022 and 2023 (in thousands, except share and per share data): NUMBER OF WEIGHTED- WEIGHTED- AGGREGATE Outstanding, December 31, 2021 2,662,752 $ 6.26 Granted 1,455,594 4.86 Exercised ( 11,756 ) 3.71 Forfeited ( 98,413 ) 6.73 Outstanding, December 31, 2022 4,008,177 5.76 Granted 1,004,632 7.38 Exercised ( 100,322 ) 4.94 Forfeited ( 231,161 ) 6.44 Outstanding, December 31, 2023 4,681,326 $ 6.09 7.02 $ 4,216 Vested and exercisable, December 31, 2023 2,784,463 $ 5.87 5.93 $ 3,110 Vested and expected to vest, December 31, 2023 4,295,457 $ 6.09 6.87 $ 3,960 The following table summarizes information about RSU activity during 2022 and 2023: RSUs AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE) RSUs outstanding, December 31, 2021 42,250 $ 3.25 Granted — — Vested ( 42,250 ) 3.25 Forfeited — — RSUs outstanding, December 31, 2022 — — Granted 387,950 6.04 Vested — — Forfeited ( 19,539 ) 6.03 RSUs outstanding, December 31, 2023 368,411 $ 6.03 The number of RSUs vested includes shares of common stock withheld on behalf of employees to satisfy the minimum statutory tax withholding requirements. During 2022 and 2023 , the Company received $ 44,000 and $ 354,000 , respectively, upon exercise of stock options. The intrinsic value of the options exercised in 2022 and 2023 was $ 17,000 and $ 244,000 , respectively. 24,343 options were exercised on December 29, 2023 and the shares settled on January 2, 2024. Cash received on January 2, 2024 related to this exercise totaled $ 141,000 . This share issuance will be recognized on the Company's Condensed Consolidated Statements of Stockholders' Equity for the quarter ending March 31, 2024. Unrecognized compensation expense related to unvested options as of December 31, 2023 was $ 5.1 million and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 2.3 years. Unrecognized compensation expense related to unvested RSUs as of December 31, 2023 was $ 1.2 million and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 3.1 years. During the three months ended June 30, 2023, as part of a severance arrangement, the Company extended the exercise period to six months for 111,532 vested options, with a weighted exercise price of $ 6.25 , and recorded incremental stock-based compensation of $ 87,000 . Employee Stock Purchase Plan In October 2017, the board of directors approved the 2017 Employee Stock Purchase Plan (“the ESPP”) which became effective in November 2017, upon the closing of the Company’s IPO. As part of the ESPP, eligible employees may acquire an ownership interest in the Company by purchasing common stock, at a discount, through payroll deductions. Eligible employees who elected to participate were able to participate in the ESPP beginning September 1, 2021. During 2022 and 2023 , 45,938 and 90,125 shares of common stock were issued under the ESPP, respectively. As of December 31, 2023, there were 1,257,566 shares of common stock available for issuance under the ESPP. The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations and comprehensive loss for employees, directors and non-employees during the years ended December 31, 2022 and 2023 as follows (in thousands): 2022 2023 Research and development $ 1,050 $ 1,446 Selling, general and administrative 1,788 3,410 Total $ 2,838 $ 4,856

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and Contingencies Operating Leases The Company entered into noncancelable operating leases for office facilities located in Lexington, Massachusetts and Burlington, Massachusetts through December 31, 2022 and November 30, 2023 , respectively. These leases were terminated as of December 31, 2023. In September 2023, the Company entered into a sublease agreement, pursuant to which the Company agreed to sublease office space for its new headquarters in Burlington, Massachusetts, under a non-cancelable operating lease, which expires on August 31, 2029. Rent expense under the operating leases totaled $ 0.5 million and $ 0.6 million for the years ended December 31, 2022 and 2023, respectively. Certain leases provide for increases in future minimum annual rental payments as defined in the lease agreements. The leases generally also include real estate taxes and common area maintenance charges in the annual rental payments. Pursuant to the terms of its lease agreement for the Company’s former headquarters in Burlington, Massachusetts, the Company obtained a letter of credit in the amount of approximately $ 182,000 as security on the lease obligation. During the year ended December 31, 2023, the Company replaced the letter of credit with a $ 182,000 cash deposit which is included in deposits and other current assets on the balance sheet. Short-term leases are leases having a term of twelve months or less. The Company recognizes short-term leases on a straight-line basis and does no t record a related lease asset or liability for such leases. The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of December 31, 2023 (in thousands): Year ended: December 31, 2024 $ 339 December 31, 2025 341 December 31, 2026 349 December 31, 2027 358 December 31, 2028 367 Thereafter 249 Total minimum lease payments 2,003 Less imputed interest ( 545 ) Total $ 1,458 2022 2023 Lease cost: Operating lease cost $ 505 $ 692 Short-term lease cost 37 22 Sublease income ( 47 ) - Total lease cost $ 495 $ 714 Other information Cash paid for amounts included in the $ 551 $ 625 Operating cash flows from operating leases $ ( 57 ) $ 50 Weighted-average remaining lease term - 0.9 years 5.6 years Weighted-average discount rate - 10.1 % 11.7 % In July 2021, the Company signed a lease agreement for a new office facility located in Salem, New Hampshire. The lease commenced on September 1, 2021 and had an initial term of 12 months with an optional extension term through August 2023 which was exercised. In June 2023, the Company extended the lease through August 2024. The lease is considered short-term and is being recognized on a straight-line basis. Research and Development Agreements As part of the Company’s research and development efforts, the Company enters into research and development agreements with unrelated companies. These agreements contain varying terms and provisions which include fees and milestones to be paid by the Company. Some of these agreements also contain provisions which require the Company to make payments for exclusivity in the development of products in the area of loop diuretics. Contingencies The Company follows subtopic 450-20 of the FASB ASC to report accounting for contingencies. Certain conditions may exist as of the date the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. If the assessment of a contingency indicates that it is probable that a material loss has been incurred and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potential material loss contingency is not probable but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, and an estimate of the range of possible losses, if determinable and material, would be disclosed. Loss contingencies considered remote are generally not disclosed unless they involve guarantees, in which case the guarantees would be disclosed.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
401(k) Savings Plan	14. 401(k) Savings Plan In July 2014, the Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code covering all of its employees. Employees may make contributions by withholding a percentage of their salary. The plan includes an employer match equal to 100 % on the first 3 % of deferred compensation and an additional 50 % on the next 2 % of deferred compensation. During the years ended December 31, 2022 and 2023 , the Company has recognized compensation expense of $ 340,000 and $ 712,000 , respectively, for the employer match contribution.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	15. Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The Company evaluated subsequent events through the issuance date of the financial statements and concluded that no subsequent events have occurred that would require recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include the determination of fair value of financial instruments, accounting policies for revenue recognition, accruals related to development costs and clinical activities, and the establishment of the tax valuation allowance. Actual results could differ from those estimates.
Foreign Currency Transactions	Foreign Currency Transactions The functional currency of the Company is the U.S. dollar. Accordingly, gains and losses resulting from translating transactions denominated in currencies and balances of assets and liabilities outstanding at the balance sheet date, other than U.S. dollars, are included in net loss in the Statements of Operations and Comprehensive Loss.
Cash Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company places its cash and cash equivalents with institutions with high credit quality. However, at certain times such cash and cash equivalents may be in excess of Federal Deposit Insurance Corporation and Securities Investor Protection Corporation insurance limits. The Company has not experienced any losses with respect to these accounts. As of December 31, 2022 , the Company classified $ 182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 13). As of December 31, 2023, this amount was reclassified to deposits as the funds were transferred upon the cancelation of its letter of credit. Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, December 31, Cash and cash equivalents $ 71,061 $ 46,814 Restricted cash 182 - Cash, cash equivalents and restricted cash $ 71,243 $ 46,814
Accounts Receivable	Accounts Receivable Accounts receivable are recorded net of any estimated expected credit losses. The Company's measurement of expected credit losses is based on relevant information about past events, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. To date, expected credit losses have not been material.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and short-term investments. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s short-term investments consist of commercial paper, United States Treasury securities, corporate bonds and United States Government Agency securities. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to hold a minimum rating, thereby reducing credit risk exposure. Customer and Supplier Concentration The Company has a limited number of specialty pharmacy customers and distributors. As of December 31, 2023, 3 customers represent 99 % of accounts receivable. For the year ended December 31, 2023, 2 customers represent 93 % of revenue. The Company depends on suppliers for raw materials, API, and other components that are subject to stringent FDA requirements. Some of these materials may only be available from one or a limited number of sources. Establishing additional or replacement suppliers may take a substantial period of time, as suppliers must be approved by the FDA. If the Company is unable to secure, on a timely basis, sufficient quantities of the materials it depends on to manufacture its products, it could have a materially adverse effect on the Company's business, financial condition and results of operations.
Investments	Investments The Company invests excess cash balances in available-for-sale debt securities. The Company determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company reports available-for-sale investments at fair value at each balance sheet date and includes any unrealized gains and losses in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses are determined using the specific identification method and are included in other income (expense). If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the intention to sell and, if so, marks the investment to market through a charge to the Company’s consolidated statements of operations and comprehensive loss.
Inventory	Inventory Inventory is stated at the lower of cost and net realizable value and consists of raw materials, work-in-process and finished goods. The Company began capitalizing inventory costs following U.S. Food and Drug Administration ("FDA") approval of FUROSCIX on October 7, 2022. Inventory is sold on a first in, first out ("FIFO") basis. The Company periodically reviews inventory for expiry and obsolescence and writes it down accordingly, if necessary. Prior to FDA approval of FUROSCIX, the Company expensed all inventory-related costs, including that used for clinical development, to research and development ("R&D") costs in the period incurred.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) lease assets, current portion of lease obligations, and long term lease obligations on the Company’s balance sheets. ROU lease assets represent the Company’s right to use an underlying asset for the lease term and lease obligations represent the Company’s obligation to make lease payments arising from the lease. Operating ROU lease assets and obligations are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU lease asset excludes lease incentives. The Company’s lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term.
Debt Issuance Costs	Debt Issuance Costs Debt issuance costs are amortized to interest expense using the effective interest rate method over the term of the debt. Debt issuance costs paid to the lender and third parties are reflected as a discount to the debt in the consolidated balance sheets
Revenue Recognition	Revenue Recognition The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of Accounting Standards Codification ("ASC") Topic 606, Revenue from Contracts with Customer (“Topic 606”), the Company 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 the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied. The Company has identified one performance obligation, the delivery of FUROSCIX to its customers. The Company has not incurred any incremental costs associated with obtaining contracts with customers. The Company’s revenues consist solely of the sale of FUROSCIX to customers in the United States. Product Net Sales FUROSCIX was approved by the FDA on October 7, 2022. The Company launched sales of FUROSCIX in the first quarter of 2023 and its customers consist of specialty pharmacies (“SPs”) and specialty distributors ("SDs"). The Company recognizes revenue from product sales at a point in time, typically upon receipt of product at the SPs and SDs, the date at which the rights, title, interest and risk of loss are transferred. Revenues from product sales are recorded at the net sales price, which includes estimates of variable consideration that result from (a) sales discounts, (b) rebates (c) co-pay assistance, and (d) product returns. Reserves are established for the estimates of variable consideration based on the amounts earned or to be claimed on the related sales. The reserves for variable consideration are reflected as either as a reduction to the related account receivable or as an accrued liability, depending on how the consideration is settled. The amount of variable consideration that is included in the transaction price may be constrained and is included in net product revenues only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company's estimates. If actual results vary from its estimates, the Company adjusts these estimates, which would affect net product revenue and earnings in the period such variances become known. Sales Discounts : Sales discounts are agreed-upon discounts, from negotiated contracts, taken directly off the Company’s sales invoices. Sales discounts are recorded as an offset to revenue based on contractual terms at the time revenue from the sale is recognized. Rebates : Allowance for rebates include mandated discounts under the Medicaid Drug Rebate Program and the Medicare Part D prescription drug benefit, TRICARE program and contractual rebates with commercial payers. Rebates are amounts owed after the final dispensing of the product to a benefit plan participant and are based upon contractual agreements or statutory requirements. The allowance for rebates is based on contracted or statutory discount rates and expected utilization by benefit plan participants. The Company’s estimates for expected utilization of rebates are based on utilization data received from the SPs since product launch. Rebates are generally invoiced and paid in arrears so that the accrual balance consists of an estimate of the amount expected to be incurred for the current quarter’s activity, plus an accrual balance for prior quarters’ unpaid rebates. If actual future rebates vary from estimates, the Company may need to adjust prior period accruals, which would affect revenue in the period of adjustment. Co-Payment Assistance: The Company offers co-payment assistance to commercially insured patients meeting certain eligibility requirements. Co-payment assistance is accrued at the time of product sale to SPs based on estimated patient participation and average co-pay benefit to be paid per a claim. The Company’s estimated amounts are compared to actual program participation and co-pay amounts paid using data provided by third-party administrators. If actual amounts differ from the original estimates the assumptions being applied are updated and adjustment for prior period accruals will be adjusted in the current period. Product Returns: Consistent with industry practice, the Company offers SPs and SDs limited product return rights for damages, shipment errors, and expiring product, provided that the return is within a specified period around the product expiration date as set forth in the applicable individual distribution agreement. The Company does not allow product returns for product that has been dispensed to a patient. As the Company receives inventory reports from the SPs and has the ability to control the amount of product that is sold to the SPs, it is able to make a reasonable estimate of future potential product returns based on this on-hand channel inventory data and sell-through data obtained from the SPs. Currently, sales to SDs are limited and there is no access to on-hand channel inventory or sell through data. As these arrangements mature, the Company will utilize any data that they can provide as part of this analysis. In arriving at its estimate, the Company also considers historical product returns, the underlying product demand, and industry data specific to the specialty pharmaceutical distribution industry.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Nonrefundable advance payments, if any, for goods or services used in research and development are initially recorded as an asset and then recognized as an expense as the related goods are delivered or services are performed. Research and development expenses include contract services, consulting, salaries, materials and supplies and overhead.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with ASC 740 Income Taxes (“ASC 740”) . Deferred tax assets and liabilities are recorded to reflect the impact of temporary differences between amounts of assets and liabilities for financial reporting purposes and such amounts as measured under enacted tax laws. A valuation allowance is required to offset any net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax asset will not be realized. The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. The tax benefits recorded are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming that the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At December 31, 2022 and 2023 , the Company had no such accruals.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense for stock options is recognized based on the grant-date fair value using the Black-Scholes valuation model. Restricted stock units are valued at the fair market value per share of the Company’s common stock on the date of grant. The Company recognizes compensation expense only for those stock-based awards expected to vest after considering expected forfeitures. Cumulative compensation expense is at least equal to the compensation expense for vested awards. Stock-based compensation is recognized on a straight-line basis over the service period of each award.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s chief executive officer is the CODM, and he uses consolidated financial information in determining how to allocate resources and assess performance. The Company has determined that it operates in one segment.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2023-09, Income Taxes ("ASU 2023-09"), requiring entities to provide additional information in the income tax rate reconciliation and additional disclosures about income taxes paid. The new accounting guidance requires entities to disclose in their rate reconciliation table additional categories of information about federal, state and foreign income taxes and to provide more details about the reconciling items in some categories if the items meet a quantitative threshold. This guidance is effective for annual periods beginning after December 15, 2024, and should be applied prospectively, but entities have the option to apply it retrospectively for each period presented. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. The Company is currently evaluating the impact of the adoption of ASU 2023-09 and does not expect adoption to have a material effect on the Company’s consolidated financial statements or disclosures.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Cash, Cash Equivalents and Restricted Cash	Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, December 31, Cash and cash equivalents $ 71,061 $ 46,814 Restricted cash 182 - Cash, cash equivalents and restricted cash $ 71,243 $ 46,814

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share of Common Stock	The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except shares and per share data): For the year ended December 31, December 31, Net loss $ ( 36,838 ) $ ( 54,810 ) Weighted—average common shares 28,358,502 38,513,747 Net loss per share, basic and diluted $ ( 1.30 ) $ ( 1.42 )
Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive (in common stock equivalent shares): For the year ended December 31, December 31, Stock options to purchase common stock 4,008,177 4,681,326 Warrants to purchase common stock 516,345 516,345 Unvested restricted stock — 368,411 4,524,522 5,566,082

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Classified Investments	A summary of the Company’s available-for-sale classified investments as of December 31, 2022 and 2023 consisted of the following (in thousands): At December 31, 2022 Investments - Current: Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Commercial paper $ 16,741 $ - $ - $ 16,741 United States Treasury securities 15,768 7 - 15,775 United States Government Agency securities 14,584 25 - 14,609 Total $ 47,093 $ 32 $ - $ 47,125 At December 31, 2023 Investments - Current: Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value United States Treasury securities $ 13,967 $ 2 $ - $ 13,969 Commercial paper 9,427 - ( 2 ) 9,425 Corporate bonds 3,815 - - 3,815 United States Government Agency securities 1,991 - ( 1 ) 1,990 Total $ 29,200 $ 2 $ ( 3 ) $ 29,199
Summary of Amortized Cost and Fair Value of Available-for-Sale Investments by Contract Maturity	The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of December 31, 2023 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 29,200 $ 29,199 Total $ 29,200 $ 29,199

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Schedule of Inventory	The Company's inventory balance consists of the following (in thousands): As of December 31, 2022 2023 Raw materials $ 1,201 $ 4,256 Work-in-process 29 4,188 Finished goods — 396 $ 1,230 $ 8,840

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Purchased Property and Equipment	Purchased property and equipment consist of the following as of December 31, 2022 and 2023 (in thousands): ESTIMATED 2022 2023 Office equipment 5 years $ 6 $ 31 Office furniture 7 years 126 64 Computer equipment 3 years 15 15 Leasehold improvements Life of lease 95 9 242 119 Less: Accumulated depreciation ( 188 ) ( 61 ) Property and equipment, net $ 54 $ 58

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Expenses	Accrued expenses at December 31, 2022 and 2023 consist of (in thousands): 2022 2023 Employee compensation and related costs $ 2,754 $ 4,375 Sales allowances and related costs - 1,418 Contract research and development 1,827 1,202 Consulting and professional service fees 603 945 Manufacturing costs - 434 Royalty - 249 Inventory in transit - 150 Other 105 128 Total accrued expenses $ 5,289 $ 8,901

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Net Deferred Tax Assets	Components of the net deferred tax assets at December 31, 2022 and 2023 are as follows (in thousands): 2022 2023 Deferred tax assets: Federal net operating loss carryforwards $ 17,252 $ 30,405 State net operating loss carryforwards 4,585 8,216 Research and development tax credits 4,214 4,729 Accrued liabilities 677 1,088 Stock-based compensation 1,329 1,814 Depreciation and amortization 324 3 Capitalized research and development costs 30,976 27,720 Lease liabilities 146 370 Total deferred tax assets 59,503 74,345 Deferred tax liabilities: Right-of-use lease assets ( 144 ) ( 355 ) Other ( 273 ) ( 833 ) Total deferred tax liabilities $ ( 417 ) $ ( 1,188 ) Valuation allowance $ ( 59,086 ) $ ( 73,157 ) Net deferred tax assets $ — $ —
Summary of Reconciliation of Beginning and Ending Amount of Valuation Allowance	A reconciliation of the beginning and ending amount of the valuation allowance is as follows (in thousands): 2022 2023 Beginning valuation allowance $ 51,399 $ 59,086 Current year - increases 7,687 14,071 Ending valuation allowance $ 59,086 $ 73,157
Schedule of Reconciliation of Income Tax (Expense) Benefit	A reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the consolidated financial statements at December 31, 2022 and 2023 are as follows: 2022 2023 Federal income tax at statutory rate 21.00 % 21.00 % State income tax, net of federal benefit 4.28 % 8.65 % Research and development credits 1.39 % 0.96 % Book compensation related to stock options ( 0.80 )% ( 1.00 )% Change in income tax rate ( 4.93 )% ( 3.16 )% Other ( 0.09 )% ( 0.01 )% Increase in valuation allowance ( 20.87 )% ( 25.68 )% Permanent differences — ( 0.76 )% Effective tax rate ( 0.02 )% — %
Schedule of Reconciliation of Uncertain Tax Benefits	A reconciliation of the beginning and ending amount of uncertain tax benefits is as follows (in thousands): 2022 2023 Beginning uncertain tax benefits $ 977 $ 1,106 Prior year - increases — 28 Current year - increases 129 102 Ending uncertain tax benefits $ 1,106 $ 1,236

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables summarize the Company’s assets and liabilities that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): As of December 31, 2022 TOTAL Quoted Prices Significant Significant Assets: Cash equivalents $ 65,875 $ 65,875 $ — $ — Total cash equivalents 65,875 65,875 — — Commercial paper 16,741 — 16,741 — United States Treasury securities 15,775 15,775 — — United States Government Agency securities 14,609 — 14,609 — Investments 47,125 15,775 31,350 — Total $ 113,000 $ 81,650 $ 31,350 $ — Liabilities: Derivative liability $ 7,517 $ — $ — $ 7,517 Total $ 7,517 $ — $ — $ 7,517 As of December 31, 2023 TOTAL Quoted Prices Significant Significant Assets: Cash equivalents $ 44,202 $ 44,202 $ — $ — Total cash equivalents 44,202 44,202 — — United States Treasury securities 13,969 13,969 — — Commercial paper 9,425 — 9,425 — Corporate bonds 3,815 — 3,815 — United States Government Agency securities 1,990 — 1,990 — Investments 29,199 13,969 15,230 — Total $ 73,401 $ 58,171 $ 15,230 $ — Liabilities: Derivative liability $ 3,857 $ — $ — $ 3,857 Total $ 3,857 $ — $ — $ 3,857
Schedule of Changes in Fair Value of Level 3 Derivative Liability	Changes in the fair value of the Company’s Level 3 derivative liability for the year ended December 31, 2023 are as follows: At December 31, 2022 $ 7,517 Change in fair value of derivative liability ( 3,660 ) At December 31, 2023 $ 3,857
Schedule of Quantitative Information about Significant Unobservable Inputs	A summary of quantitative information about significant unobservable inputs (Level 3 inputs) used in measuring the Company's derivative liability that are categorized within Level 3 of the fair value hierarchy is as follows: December 31, December 31, Net sales discount rate 22.3 % 20.7 % Net sales volatility 80.0 % 70.0 % Risk-free rate 4.0 % 3.9 % Recovery rate 80.0 % 80.0 %

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Carrying Value of Debt Balnce	The following table presents the carrying value of the Company's debt balance as of December 31, 2022 and 2023 (in thousands): DECEMBER 31, DECEMBER 31, Face value of term loans $ 50,000 $ 50,000 Unamortized debt discount ( 13,206 ) ( 11,189 ) Total debt, net $ 36,794 $ 38,811 Less: short-term debt — — Long-term debt $ 36,794 $ 38,811
Schedule of Future Principal Payments Due	As of December 31, 2023, future principal payments due under the Oaktree Agreement are as follows (in thousands): Year ended: December 31, 2024 $ - December 31, 2025 2,500 December 31, 2026 10,000 December 31, 2027 37,500 Total minimum principal payments 50,000

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Estimated Fair Value of Options Valuation Assumptions	The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions: 2022 2023 Risk-free interest rate 1.67 %— 4.18 % 3.40 %— 4.67 % Expected dividend yield 0 % 0 % Expected life 5.5 — 6.7 years 5.5 — 7.0 years Expected volatility 70 %— 84 % 77 %— 85 % Weighted-average grant date $ 3.18 $ 5.26
Summary of Information about Stock Option Activity	The following table summarizes information about stock option activity during 2022 and 2023 (in thousands, except share and per share data): NUMBER OF WEIGHTED- WEIGHTED- AGGREGATE Outstanding, December 31, 2021 2,662,752 $ 6.26 Granted 1,455,594 4.86 Exercised ( 11,756 ) 3.71 Forfeited ( 98,413 ) 6.73 Outstanding, December 31, 2022 4,008,177 5.76 Granted 1,004,632 7.38 Exercised ( 100,322 ) 4.94 Forfeited ( 231,161 ) 6.44 Outstanding, December 31, 2023 4,681,326 $ 6.09 7.02 $ 4,216 Vested and exercisable, December 31, 2023 2,784,463 $ 5.87 5.93 $ 3,110 Vested and expected to vest, December 31, 2023 4,295,457 $ 6.09 6.87 $ 3,960
Schedule of RSU Activity	The following table summarizes information about RSU activity during 2022 and 2023: RSUs AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE) RSUs outstanding, December 31, 2021 42,250 $ 3.25 Granted — — Vested ( 42,250 ) 3.25 Forfeited — — RSUs outstanding, December 31, 2022 — — Granted 387,950 6.04 Vested — — Forfeited ( 19,539 ) 6.03 RSUs outstanding, December 31, 2023 368,411 $ 6.03
Summary of Stock-Based Compensation Expense	The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations and comprehensive loss for employees, directors and non-employees during the years ended December 31, 2022 and 2023 as follows (in thousands): 2022 2023 Research and development $ 1,050 $ 1,446 Selling, general and administrative 1,788 3,410 Total $ 2,838 $ 4,856

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities	The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of December 31, 2023 (in thousands): Year ended: December 31, 2024 $ 339 December 31, 2025 341 December 31, 2026 349 December 31, 2027 358 December 31, 2028 367 Thereafter 249 Total minimum lease payments 2,003 Less imputed interest ( 545 ) Total $ 1,458
Schedule of Lease Cost and Other Information of Operating Lease Liabilities	2022 2023 Lease cost: Operating lease cost $ 505 $ 692 Short-term lease cost 37 22 Sublease income ( 47 ) - Total lease cost $ 495 $ 714 Other information Cash paid for amounts included in the $ 551 $ 625 Operating cash flows from operating leases $ ( 57 ) $ 50 Weighted-average remaining lease term - 0.9 years 5.6 years Weighted-average discount rate - 10.1 % 11.7 %

Description of Business and B_2

Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2022	Dec. 31, 2023	Dec. 31, 2022
Description Of Business And Basis Of Presentation [Line Items]
Cash, cash equivalents, restricted cash and investments		$ 76,000
Working capital		79,800
Net loss		54,810	$ 36,838
Net cash flows used in operating activities		59,244	$ 34,577
Common Stock | Maximum | Cowen
Description Of Business And Basis Of Presentation [Line Items]
Aggregate offering price		$ 34,500
Follow On Offering | Common Stock
Description Of Business And Basis Of Presentation [Line Items]
Proceeds from sale of shares, Net	$ 46,600

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Segment Customer	Dec. 31, 2022 USD ($)
Schedule Of Accounting Policies [Line Items]
Restricted cash, current		$ 182,000
Potential interest and penalties associated with uncertain tax positions, accruals	$ 0	0
Number of operating segments | Segment	1
Accounts Receivable
Schedule Of Accounting Policies [Line Items]
Number of Customer | Customer	3
Revenue
Schedule Of Accounting Policies [Line Items]
Number of Customer | Customer	2
Customer Three | Customer Concentration Risk | Accounts Receivable
Schedule Of Accounting Policies [Line Items]
Percentage of concentration risk	99%
Customer Two | Customer Concentration Risk | Revenue
Schedule Of Accounting Policies [Line Items]
Percentage of concentration risk	93%
Letter of Credit
Schedule Of Accounting Policies [Line Items]
Restricted cash, current		$ 182,000

Significant Accounting Polici_5

Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 46,814	$ 71,061
Restricted cash		182
Cash, cash equivalents and restricted cash	$ 46,814	$ 71,243	$ 74,450

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Details)	Dec. 31, 2023 $ / shares
Earnings Per Share [Abstract]
Exercise price per share	$ 0.001

Net Loss per Share - Computatio

Net Loss per Share - Computation of Basic and Diluted Net Loss Per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Net loss	$ (54,810)	$ (36,838)
Weighted --average common shares outstanding, basic	38,513,747	28,358,502
Weighted--average common shares outstanding, diluted	38,513,747	28,358,502
Net loss per share, basic	$ (1.42)	$ (1.3)
Net loss per share, diluted	$ (1.42)	$ (1.3)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	5,566,082	4,524,522
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	4,681,326	4,008,177
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	516,345	516,345
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	368,411

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Classified Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Cost Basis	$ 29,200	$ 47,093
Accumulated Unrealized Gains	2	32
Accumulated Unrealized Losses	(3)
Fair Value	29,199	47,125
Commercial Paper
Marketable Securities [Line Items]
Cost Basis	9,427	16,741
Accumulated Unrealized Losses	(2)
Fair Value	9,425	16,741
Corporate Bonds
Marketable Securities [Line Items]
Cost Basis	3,815
Fair Value	3,815
United States Treasury Securities
Marketable Securities [Line Items]
Cost Basis	13,967	15,768
Accumulated Unrealized Gains	2	7
Fair Value	13,969	15,775
United States Government Agency Securities
Marketable Securities [Line Items]
Cost Basis	1,991	14,584
Accumulated Unrealized Gains		25
Accumulated Unrealized Losses	(1)
Fair Value	$ 1,990	$ 14,609

Investments - Summary of Amorti

Investments - Summary of Amortized Cost and Fair Value of Available-for-Sale Investments by Contract Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 29,200
Amortized Cost, Total	29,200	$ 47,093
Fair Value, Due in one year or less	29,199
Fair Value, Total	$ 29,199	$ 47,125

Inventory - Schedule of Invento

Inventory - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 4,256	$ 1,201
Work-in-process	4,188	29
Finished goods	396
Inventory, Net, Total	$ 8,840	$ 1,230

Property and Equipment - Schedu

Property and Equipment - Schedule of Purchased Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 119	$ 242
Less: Accumulated depreciation	(61)	(188)
Property and equipment, net	$ 58	54
Office Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years
Property and equipment, gross	$ 31	6
Office Furniture
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	7 years
Property and equipment, gross	$ 64	126
Computer Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	3 years
Property and equipment, gross	$ 15	15
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	us-gaap:UsefulLifeTermOfLeaseMember
Property and equipment, gross	$ 9	$ 95

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 24,000	$ 37,000

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Employee compensation and related costs	$ 4,375	$ 2,754
Sales allowances and related costs	1,418
Contract research and development	1,202	1,827
Consulting and professional service fees	945	603
Manufacturing costs	434
Royalty	249
Inventory in transit	150
Other	128	105
Total accrued expenses	$ 8,901	$ 5,289

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Net income tax provision or benefit	$ 0	$ 0
Federal net operating loss carryforwards expiration year	2037
State net operating loss carryforwards expiration year	2043
Increase in valuation allowance	$ 14,071,000	7,687,000
Research and development credit carryforwards	$ 4,729,000	4,214,000
Federal and state research and development credit carryforwards expiration year	2043
Ownership interest rate change over period	3 years
Capitalized R&D costs	$ 11,600,000	$ 13,600,000
Minimum
Income Taxes [Line Items]
Cumulative changes in ownership interest of shareholders	50%
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 127,300,000
Research and development credit carryforwards	$ 3,900,000
Amortize costs for tax years	5 years
Federal | 2037
Income Taxes [Line Items]
Net operating loss carryforwards	$ 17,500,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	1,800,000
Research and development credit carryforwards	1,000,000
State | 2043
Income Taxes [Line Items]
Net operating loss carryforwards	$ 147,100,000
Outside U.S.
Income Taxes [Line Items]
Amortize costs for tax years	15 years

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Federal net operating loss carryforwards	$ 30,405	$ 17,252
State net operating loss carryforwards	8,216	4,585
Research and development tax credits	4,729	4,214
Accrued liabilities	1,088	677
Stock-based compensation	1,814	1,329
Depreciation and amortization	3	324
Capitalized research and development costs	27,720	30,976
Lease liabilities	370	146
Total deferred tax assets	74,345	59,503
Deferred tax liabilities:
Right-of-use lease assets	(355)	(144)
Other	(833)	(273)
Total deferred tax liabilities	(1,188)	(417)
Valuation allowance	(73,157)	(59,086)	$ (51,399)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Beginning and Ending Amount of Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Components of Deferred Tax Assets [Abstract]
Beginning valuation allowance	$ 59,086	$ 51,399
Current year - increases	14,071	7,687
Ending valuation allowance	$ 73,157	$ 59,086

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax (Expense) Benefit (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	21%	21%
State income tax, net of federal benefit	8.65%	4.28%
Research and development credits	0.96%	1.39%
Book compensation related to stock options	(1.00%)	(0.80%)
Change in income tax rate	(3.16%)	(4.93%)
Other	(0.01%)	(0.09%)
Increase in valuation allowance	(25.68%)	(20.87%)
Permanent differences	(0.76%)	0%
Effective tax rate	0%	(0.02%)

Income Taxes - Schedule of Re_2

Income Taxes - Schedule of Reconciliation of Uncertain Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Beginning uncertain tax benefits	$ 1,106	$ 977
Prior year - increases	28	0
Current year - increases	102	129
Ending uncertain tax benefits	$ 1,236	$ 1,106

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Liabilities:
Derivative liability	$ 3,857	$ 7,517
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	44,202	65,875
Investments	29,199	47,125
Total	73,401	113,000
Liabilities:
Derivative liability	3,857	7,517
Total	3,857	7,517
Fair Value, Measurements, Recurring | Commercial Paper
Assets:
Investments	9,425	16,741
Fair Value, Measurements, Recurring | United States Treasury securities
Assets:
Investments	13,969	15,775
Fair Value, Measurements, Recurring | Corporate Bonds
Assets:
Investments	3,815
Fair Value, Measurements, Recurring | United States Government Agency securitites
Assets:
Investments	1,990	14,609
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Cash equivalents	44,202	65,875
Investments	13,969	15,775
Total	58,171	81,650
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1) [Member] | United States Treasury securities
Assets:
Investments	13,969	15,775
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Investments	15,230	31,350
Total	15,230	31,350
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper
Assets:
Investments	9,425	16,741
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds
Assets:
Investments	3,815
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) [Member] | United States Government Agency securitites
Assets:
Investments	1,990	14,609
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) [Member]
Liabilities:
Derivative liability	3,857	7,517
Total	$ 3,857	$ 7,517

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Schedule of Changes in Fair Value of Level 3 Derivative Liability (Details) - Significant Unobservable Inputs (Level 3) [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 7,517
Change in fair value of derivative liability	$ (3,660)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)
Ending balance	$ 3,857

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Schedule of Quantitative Information about Significant Unobservable Inputs (Details) - Level 3	Dec. 31, 2023	Dec. 31, 2022
Net Sales Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.207	0.223
Net Sales Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.70	0.80
Risk-free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.039	0.04
Recovery Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.80	0.80

Debt - Schedule of Carrying Val

Debt - Schedule of Carrying Value of Debt Balance (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
Face value of term loans	$ 50,000	$ 50,000
Unamortized debt discount	(11,189)	(13,206)
Total debt, net	38,811	36,794
Long-term debt	$ 38,811	$ 36,794

Debt - Additional Information (

Debt - Additional Information (Details)		1 Months Ended		12 Months Ended
	Oct. 13, 2022 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares
Debt Instrument [Line Items]
Loan and security agreement, amount				$ 50,000,000	$ 50,000,000
Proceeds from term loan					$ 47,301,000
Exercise price per share | $ / shares				$ 0.001
Fair market value per share of common stock | $ / shares				$ 5.26	$ 3.18
Unamortized debt discount				$ (11,189,000)	$ (13,206,000)
Minimum
Debt Instrument [Line Items]
Contractual life				5 years 6 months	5 years 6 months
Maximum
Debt Instrument [Line Items]
Contractual life				7 years	6 years 8 months 12 days
SLR Investment Corp. and Silicon Valley Bank | 2017 Loan Agreement
Debt Instrument [Line Items]
Loan and security agreement, amount			$ 10,000,000
Loan agreement, maturity date			May 01, 2021
Payment of final fee		$ 325,000
SLR Investment Corp. and Silicon Valley Bank | 2019 Loan Agreement
Debt Instrument [Line Items]
Loan and security agreement, amount		$ 20,000,000		$ 50,000,000
Loan agreement, maturity date		Sep. 17, 2023
Amortization of debt discount					$ 341,000
Final payment fee				$ 500,000
Amortization of final payment fee					132,000
Loan agreement, term		4 years
Prepayment premium percentage after year two				0.50%
Long term debt prepayment premium amount				$ 46,000
SLR Investment Corp. and Silicon Valley Bank | 2019 Loan Agreement | Minimum
Debt Instrument [Line Items]
Prepayment premium percentage two				0.01
SLR Investment Corp. and Silicon Valley Bank | 2019 Loan Agreement | Maximum
Debt Instrument [Line Items]
Prepayment premium percentage one				0.03
Oaktree Agreement [Member]
Debt Instrument [Line Items]
Loan agreement, maturity date	Oct. 13, 2027
Basis spread on variable base rate	8.25%
Proceeds from (Repayments of) Debt, Total	$ 9,800,000
Payment of financing and stock issuance costs	2,700,000
Long term additional debt discount exit fee				$ 1,000,000
Embedded derivative liability upon issuance of Term Loan	8,900,000
Fair value of embedded derivative liability				3,900,000	7,500,000
Amortization of debt discount				2,000,000	383,000
Unamortized debt discount	$ (13,600,000)
Exit fee				$ 149,000	$ 28,000
Prepayment premium percentage one	0.02
Increase in interest rate on default	2%
Oaktree Agreement [Member] | Minimum
Debt Instrument [Line Items]
Trailing of net sales	$ 100,000,000
Oaktree Agreement [Member] | Maximum
Debt Instrument [Line Items]
Loan and security agreement, amount	$ 100,000,000
Oaktree Agreement [Member] | Warrants
Debt Instrument [Line Items]
Exercise price per share | $ / shares	$ 5.4
Relative fair value of detachable warrants	$ 2,000,000
Risk-free rate	4.11%
Contractual life	7 years
Fair market value per share of common stock | $ / shares	$ 5.5
Exercise price per warrant | $ / shares	$ 5.4
Expected volatility	77%
Oaktree Agreement [Member] | Warrants | Maximum
Debt Instrument [Line Items]
Purchase shares of common stock | shares	516,345
Oaktree Agreement [Member] | SOFR
Debt Instrument [Line Items]
Basis spread on variable base rate	8.75%
Oaktree Agreement [Member] | SOFR | Interest Rate Floor [Member]
Debt Instrument [Line Items]
Basis spread on variable base rate	1%
Oaktree Agreement [Member] | SOFR | Interest Rate Cap [Member]
Debt Instrument [Line Items]
Basis spread on variable base rate	3%
Oaktree Agreement [Member] | Borrowings One [Member]
Debt Instrument [Line Items]
Loan and security agreement, amount	$ 50,000,000
Proceeds from term loan	37,500,000
Unrestricted cash	15,000,000
Oaktree Agreement [Member] | Borrowings Two [Member]
Debt Instrument [Line Items]
Loan and security agreement, amount	50,000,000
Unrestricted cash	20,000,000
Oaktree Agreement [Member] | Borrowings Three [Member]
Debt Instrument [Line Items]
Loan and security agreement, amount	$ 50,000,000

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Payments Due (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2019
Debt Instrument [Line Items]
Total minimum principal payments	$ 50,000	$ 50,000
2019 Loan Agreement | SLR Investment Corp. and Silicon Valley Bank
Debt Instrument [Line Items]
December 31, 2025	2,500
December 31, 2026	10,000
December 31, 2027	37,500
Total minimum principal payments	$ 50,000		$ 20,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Mar. 23, 2021	Nov. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders Equity Note [Line Items]
Common stock, shares authorized			150,000,000	150,000,000
Common stock, par value			$ 0.0001	$ 0.0001
Common stock, shares issued			35,968,510	34,257,916
Common stock, shares outstanding			35,968,510	34,257,916
Reserved shares of common stock for exercise of outstanding options to purchase common stock			4,681,326	4,008,177	2,662,752
Number of reserved shares of common stock for vesting of RSUs			368,411
Preferred stock, shares authorized			10,000,000	10,000,000
Preferred stock, par value			$ 0.0001	$ 0.0001
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
prefunded warrant purchase price			$ 0.001
Cowen | Common Stock | Maximum
Stockholders Equity Note [Line Items]
Aggregate offering price			$ 34,500,000
2021 ATM Agreement | Legal Accounting and Other Costs
Stockholders Equity Note [Line Items]
Stock issuance cost	$ 273,000
2021 ATM Agreement | Additional Paid-in Capital | Legal Accounting and Other Costs
Stockholders Equity Note [Line Items]
Stock issuance cost			$ 79,000	$ 6,000
2021 ATM Agreement | Cowen | Common Stock
Stockholders Equity Note [Line Items]
Number of shares sold			1,544,490	181,553
Proceeds from sale of shares, Net			$ 14,000,000	$ 1,100,000
2021 ATM Agreement | Cowen | Common Stock | Weighted Average
Stockholders Equity Note [Line Items]
Selling price per share			$ 9.32	$ 6.33
2021 ATM Agreement | Cowen | Common Stock | Maximum
Stockholders Equity Note [Line Items]
Aggregate offering price	$ 50,000,000
Percentage of commission on gross sales proceeds	3%
Underwritten Public Offering | Common Stock
Stockholders Equity Note [Line Items]
Number of shares sold		6,620,000
Selling price per share		$ 5.25
Proceeds from sale of shares, Net		$ 46,600,000
prefunded warrant purchase price		$ 5.249
Underwritten Public Offering | Common Stock | Maximum
Stockholders Equity Note [Line Items]
prefunded warrant shares		2,905,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)				3 Months Ended	12 Months Ended
	Jan. 02, 2024	Dec. 29, 2023	Feb. 01, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional options granted					1,004,632	1,455,594
Stock option, number of shares outstanding					4,681,326	4,008,177	2,662,752
Number of restricted stock units outstanding					368,411
Cash received upon exercise of stock options					$ 354,000	$ 44,000
Intrinsic value of options exercised					$ 244,000	$ 17,000
Number of options exercised		24,343			100,322	11,756
Unrecognized compensation expense					$ 5,100,000
Recognition period (in years)					2 years 3 months 18 days
Vested options, number of shares				111,532
Weighted exercise price				$ 6.25
Incremental stock based compensation				87,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense					$ 1,200,000
Recognition period (in years)					3 years 1 month 6 days
Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cash received upon exercise of stock options	$ 141,000
2017 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option and incentive plan effective date					Nov. 30, 2017
Stock option and incentive plan expiration date					Oct. 31, 2027
Stock option, number of shares outstanding					3,926,481
Number of common shares authorized for issuance					7,402,457
Stock options, available for issuance					3,067,473
Term of option granted					10 years
2017 Stock Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term					1 year
2017 Stock Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term					4 years
2017 Stock Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding					368,411
2014 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option and incentive plan expiration date					Nov. 30, 2017
Additional options granted					0
Stock option, number of shares outstanding					571,095
Number of options forfeited					366,823
2017 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock shares issued					90,125	45,938
Number of common stock shares available for issuance					1,257,566
2023 Employment Inducement Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option, number of shares outstanding					183,750
Stock options, available for issuance					316,250
Term of option granted					10 years
Equity awards granted under the inducement , Granted			500,000
2023 Employment Inducement Award Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term					1 year
2023 Employment Inducement Award Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term					4 years

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Estimated Fair Value of Options Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	3.40%	1.67%
Risk-free interest rate, maximum	4.67%	4.18%
Expected dividend yield	0%	0%
Expected volatility, minimum	77%	70%
Expected volatility, maximum	85%	84%
Weighted-average grant date fair value	$ 5.26	$ 3.18
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	7 years	6 years 8 months 12 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Information about Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 29, 2023	Dec. 31, 2023	Dec. 31, 2022
NUMBER OF SHARES
Number of shares outstanding, beginning balance		4,008,177	2,662,752
Number of shares granted		1,004,632	1,455,594
Number of shares exercised	(24,343)	(100,322)	(11,756)
Number of shares forfeited		(231,161)	(98,413)
Number of shares outstanding, ending balance		4,681,326	4,008,177
Vested and exercisable, ending balance		2,784,463
Vested and expected to vest, ending balance		4,295,457
WEIGHTED-AVERAGE EXERCISE PRICE
Weighted average exercise prices, outstanding beginning balance		$ 5.76	$ 6.26
Weighted average exercise prices, granted		7.38	4.86
Weighted average exercise prices, exercised		4.94	3.71
Weighted average exercise prices, forfeited		6.44	6.73
Weighted average exercise prices, outstanding ending balance		6.09	$ 5.76
Weighted average exercise prices, vested and exercisable ending balance		5.87
Weighted average exercise prices, vested and expected to vest ending balance		$ 6.09
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM
Weighted average remaining contractual term, outstanding		7 years 7 days
Weighted average remaining contractual term, vested and exercisable		5 years 11 months 4 days
Weighted average remaining contractual term, vested and expected to vest		6 years 10 months 13 days
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, outstanding ending balance		$ 4,216
Aggregate intrinsic value, vested and exercisable ending balance		3,110
Aggregate intrinsic value, vested and expected to vest ending balance		$ 3,960

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of RSU Activity (Details) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs outstanding	0	42,250
RSUs Granted	387,950	0
RSUs Vested	0	(42,250)
RSUs Forfeited	(19,539)	0
RSUs outstanding	368,411	0
AVERAGE GRANT DATE FAIR VALUE, Outstanding	$ 0	$ 3.25
AVERAGE GRANT DATE FAIR VALUE, Granted	6.04	0
AVERAGE GRANT DATE FAIR VALUE, Vested	0	3.25
AVERAGE GRANT DATE FAIR VALUE, Forfeited	6.03	0
AVERAGE GRANT DATE FAIR VALUE, RSUs outstanding	$ 6.03	$ 0

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,856	$ 2,838
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,446	1,050
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,410	$ 1,788

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 30, 2021	Dec. 31, 2023	Dec. 31, 2022
Commitments And Contingencies [Line Items]
Operating leases rent expense		$ 600,000	$ 500,000
Restricted cash			182,000
Short-term lease asset		1,401,000	566,000
Short-term lease liability		176,000	567,000
Operating sublease term	12 months
Short-term Leases Recognized on Straight-line Basis
Commitments And Contingencies [Line Items]
Short-term lease asset		0
Short-term lease liability		$ 0
Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash			182,000
Lexington, Massachusetts
Commitments And Contingencies [Line Items]
Operating leases expiration date		Dec. 31, 2022
Burlington, Massachusetts
Commitments And Contingencies [Line Items]
Operating leases expiration date		Nov. 30, 2023
Burlington, Massachusetts | Letter of Credit | Lease Agreement Require Standby Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash			$ 182,000
Cash deposit		$ 182,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Year ended:
December 31, 2024	$ 339
December 31, 2025	341
December 31, 2026	349
December 31, 2027	358
December 31, 2028	367
Thereafter	249
Total minimum lease payments	2,003
Less imputed interest	(545)
Total	$ 1,458

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Lease Cost and Other Information of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lease cost:
Operating lease cost	$ 692	$ 505
Short-term lease cost	22	37
Sublease income		(47)
Total lease cost	714	495
Other information
Cash paid for amounts included in the measurement of liabilities	625	551
Operating cash flows from operating leases	$ 50	$ (57)
Weighted-average remaining lease term - operating leases	5 years 7 months 6 days	10 months 24 days
Weighted-average discount rate - operating leases	11.70%	10.10%

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Details) - USD ($)		12 Months Ended
	Jul. 31, 2014	Dec. 31, 2023	Dec. 31, 2022
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Tax Status [Extensible List]		us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember
Compensation expense for employer match contribution		$ 712,000	$ 340,000
First 3% of Deferred Compensation
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	100%
Employer matching contribution percentage of employees contributions of deferred compensation	3%
Defined Contribution Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember
Next 2% of Deferred Compensation
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	50%
Employer matching contribution percentage of employees contributions of deferred compensation	2%
Defined Contribution Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember