Y-mAbs Therapeutics (YMAB) 10-K 29 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 22, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-38650
Entity Registrant Name	Y-mAbs Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4619612
Entity Address, Address Line One	230 Park Avenue
Entity Address, Address Line Two	Suite 3350
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10169
City Area Code	646
Local Phone Number	885-8505
Title of 12(b) Security	Common Stock
Trading Symbol	YMAB
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 246
Entity Common Stock, Shares Outstanding		43,777,105
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Florham Park, New Jersey
Entity Central Index Key	0001722964
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 78,637	$ 105,762
Accounts receivable, net	22,454	12,531
Inventories	5,065	6,702
Other current assets	4,955	5,452
Total current assets	111,111	130,447
Property and equipment, net	224	604
Operating lease right-of-use assets	1,412	1,739
Intangible assets, net	2,631	2,986
Other assets	12,491	5,680
TOTAL ASSETS	127,869	141,456
LIABILITIES
Accounts payable	6,060	14,175
Accrued liabilities	13,166	13,241
Operating lease liabilities, current portion	902	868
Total current liabilities	20,128	28,284
Accrued milestone and royalty payments	5,375	2,250
Operating lease liabilities, long-term portion	517	899
Other liabilities	864	802
TOTAL LIABILITIES	26,884	32,235
Commitments and contingencies (Note 9)
STOCKHOLDERS' EQUITY
Preferred stock, $0.0001 par value, 5,500,000 shares authorized and none issued at December 31, 2023 and December 31, 2022
Common stock, $0.0001 par value, 100,000,000 shares authorized at December 31, 2023 and December 31, 2022; 43,672,112 and 43,670,109 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	4	4
Additional paid-in capital	558,002	543,929
Accumulated other comprehensive income	449	1,331
Accumulated deficit	(457,470)	(436,043)
TOTAL STOCKHOLDERS' EQUITY	100,985	109,221
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 127,869	$ 141,456

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized shares	5,500,000	5,500,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized shares	100,000,000	100,000,000
Common stock, shares issued	43,672,112	43,670,109
Common stock, shares outstanding	43,672,112	43,670,109

Consolidated Statements of Net

Consolidated Statements of Net Loss and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
REVENUES
Total revenues	$ 84,819	$ 65,267
OPERATING COSTS AND EXPENSES
Cost of goods sold	11,366	7,467
License royalties	50	100
Research and development	54,219	91,572
Selling, general, and administrative	44,856	60,939
Total operating costs and expenses	110,491	160,078
Loss from operations	(25,672)	(94,811)
OTHER INCOME / (LOSS), NET
Interest and other income/(loss)	4,806	(757)
LOSS BEFORE INCOME TAXES	(20,866)	(95,568)
Provision for income taxes	561	0
NET LOSS	(21,427)	(95,568)
Other comprehensive loss
Foreign currency translation	(882)	(40)
COMPREHENSIVE LOSS	$ (22,309)	$ (95,608)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.49)	$ (2.19)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.49)	$ (2.19)
Weighted average common shares outstanding, basic (in shares)	43,645,388	43,703,663
Weighted average common shares outstanding, diluted (in shares)	43,645,388	43,703,663
Product
REVENUES
Total revenues	$ 84,319	$ 49,267
License
REVENUES
Total revenues	$ 500	$ 16,000

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balance at the beginning of period at Dec. 31, 2021	$ 4	$ 519,206	$ 1,371	$ (340,475)	$ 180,106
Balance at the beginning of period (in shares) at Dec. 31, 2021	43,694,716
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		84			84
Exercise of stock options (in shares)	20,000
Retirement of treasury shares - refer to Note 10		(963)			(963)
Retirement of treasury shares - refer to Note 10 (in shares)	(57,887)
Stock-based compensation expense		25,602			25,602
Stock-based compensation expense (in shares)	13,280
Foreign currency translation			(40)		(40)
Net Income (Loss)				(95,568)	(95,568)
Balance at the end of period at Dec. 31, 2022	$ 4	543,929	1,331	(436,043)	$ 109,221
Balance at the end of period (in shares) at Dec. 31, 2022	43,670,109				43,670,109
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		100			$ 100
Exercise of stock options (in shares)	50,000				50,000
Retirement of treasury shares - refer to Note 10		(480)			$ (480)
Retirement of treasury shares - refer to Note 10 (in shares)	(58,763)
Stock-based compensation expense		14,453			14,453
Stock-based compensation expense (in shares)	10,766
Foreign currency translation			(882)		(882)
Net Income (Loss)				(21,427)	(21,427)
Balance at the end of period at Dec. 31, 2023	$ 4	$ 558,002	$ 449	$ (457,470)	$ 100,985
Balance at the end of period (in shares) at Dec. 31, 2023	43,672,112				43,672,112

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (21,427)	$ (95,568)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	735	839
Stock-based compensation	14,453	25,602
Foreign currency transactions and other transactions	(1,259)	3,577
Changes in assets and liabilities:
Accounts receivable, net	(9,923)	(4,819)
Inventories	1,637	(1,190)
Other current assets	17	(360)
Other assets	(6,812)	(2,510)
Accounts payable	(6,856)	(919)
Accrued liabilities and other	2,203	(573)
NET CASH USED IN OPERATING ACTIVITIES	(27,232)	(75,921)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercised stock options	100	84
NET CASH PROVIDED BY FINANCING ACTIVITIES	100	84
Effect of exchange rates on cash and cash equivalents	7	35
NET DECREASE IN CASH AND CASH EQUIVALENTS	(27,125)	(75,802)
Cash and cash equivalents at the beginning of period	105,762	181,564
Cash and cash equivalents at the end of period	78,637	105,762
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for income taxes	367
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Intangible assets acquisition in accrued liabilities		1,500
Right-of-use assets obtained in exchange for lease obligations	636	347
Acquisition of treasury shares upon repayment of secured promissory note - refer to Note 10	$ 480	$ 963

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF BUSINESS	12 Months Ended
	Dec. 31, 2023
ORGANIZATION AND DESCRIPTION OF BUSINESS
ORGANIZATION AND DESCRIPTION OF BUSINESS	NOTE 1—ORGANIZATION AND DESCRIPTION OF BUSINESS Y-mAbs Therapeutics, Inc. (“we,” “us,” “our,” the “Company,” or “Y-mAbs”) is a commercial-stage biopharmaceutical company focused on the development and commercialization of novel, antibody-based therapeutic products for the treatment of cancer. Y-mAbs is leveraging the Company’s proprietary antibody platforms and deep expertise in the field of antibodies to develop a broad portfolio of innovative medicines. ​ The Company is headquartered in New York and was incorporated on April 30, 2015 under the laws of the State of Delaware.

BASIS OF PRESENTATION

BASIS OF PRESENTATION	12 Months Ended
	Dec. 31, 2023
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE 2—BASIS OF PRESENTATION The Company has incurred losses all years since inception. Operations of the Company are subject to certain risks and uncertainties, including, among others, uncertainty of drug candidate development; technological uncertainty; uncertainty regarding patents and proprietary rights; uncertainty in obtaining the FDA approval in the United States and regulatory approval in other jurisdictions; marketing or sales capability or experience; uncertainty in getting adequate payor coverage and reimbursement; dependence on key personnel; compliance with government regulations and the need to obtain additional financing. The Company’s drug candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance reporting capabilities. The Company’s drug candidates are in various stages of development. DANYELZA received accelerated approval by the FDA in November 2020, but there can be no assurance that the Company’s other research and development efforts will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development and commercialization efforts are successful, it is uncertain when, if ever, the Company will become profitable. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. The Company’s consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. The Company has experienced negative cash flows from operations since inception, and had an accumulated deficit of $457,470,000 as of December 31, 2023 and $436,043,000 as of December 31, 2022. Through December 31, 2023, the Company has funded the operations primarily through proceeds from sales of shares of the Company’s common stock, including initial public offering in September 2018 and the Company’s subsequent public offerings in November 2019 and February 2021, as well as additional funding from the sales of DANYELZA and from the sale of the Company’s Priority Review Voucher (“PRV”) obtained upon FDA approval of DANYELZA. The Company had cash and cash equivalents of $78,637,000 and $105,762,000 as of December 31, 2023 and 2022, respectively. As of the issuance date of the consolidated financial statements for the year ended December 31, 2023, the Company expects that the cash and cash equivalents at December 31, 2023 will be sufficient to fund the Company’s operating expenses and capital expenditure requirements as currently planned through at least the next 12 months. The Company may raise additional capital to fund future operations through the sale of the Company’s equity securities, incurring debt, entering into licensing or collaboration agreements with partners, grants or other sources of financing. These potential financing sources are in addition to successful commercialization of DANYELZA and our product candidates, for which the Company may obtain regulatory approval and marketing authorization. The Company’s commercialization strategy may include working with a collaborator or distributor. Sufficient funds may not be available to the Company on attractive terms or at all when needed from equity, debt or other financing. If the Company is unable to obtain additional financing from these or other sources when needed, it will likely be necessary to take other actions to enhance the Company’s liquidity position which may include significantly reducing the rate of spending through delaying or scaling back operations, or suspending certain research and development programs and other operational programs in addition to other measures. The accompanying consolidated financial statements reflect the accounts of the Company and the Company’s wholly owned subsidiary and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). All intercompany balances and transactions have been eliminated.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 3—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, net product revenues, the accrual for research and development expenses, the accrual of milestone and royalty payments, the valuation of stock options and asset impairments. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid instruments with original maturities of three months or less from date of purchase to be cash equivalents. All cash and cash equivalents are held in highly rated securities including a treasury money market fund, which is unrestricted as to withdrawal or use. To date, the Company has not experienced a loss on the cash and cash equivalents. The carrying amount of cash and cash equivalents approximates its fair value due to its short-term and liquid nature. The Company’s cash and cash equivalents are held at a large major federal, national bank. The Company maintains cash balances in excess of insured limits. The Company monitors the financial performance, credit ratings and liquidity of the money market fund to timely assess and respond to any changes in the asset values of the fund. The Company does not anticipate any loss with respect to such cash balances. Accounts Receivable, Net The Company’s accounts receivable, net balance consists of amounts due from sales of our approved product, DANYELZA. Receivables from product sales are recorded net of allowances which generally include chargebacks, doubtful accounts, rebates, returns, and discounts. The allowance is based primarily on assessment of specific identifiable customer accounts considered at risk or uncollectible, as well as an analysis of current receivables aging and expected future write-offs. The Company has not historically experienced any significant credit losses. All customer accounts are actively managed, and no losses are currently expected. The Company has not experienced any write-offs related to customer accounts receivables and has not recognized any allowance for doubtful accounts nor reversed any allowances during the years ended December 31, 2023 and 2022. Concentration of Credit Risk The Company’s product sales are made through arrangements primarily with three national U.S. specialty distributors. As of December 31, 2023, the accounts receivable balances from such distributors totaled 66% of the Company’s outstanding accounts receivable. See Note 4 – Product Revenues, Net receivable as of December 31, 2023 represented balances from international distribution partners. The Company has contractual payment terms with each customer and monitors their financial performance, historical payment terms and credit worthiness to timely assess and respond to any changes in their credit profile. Inventories The Company values the inventories at the lower of cost or net realizable value on a first-in, first-out basis. The Company’s inventory cost includes amounts related to materials, third-party contract manufacturing, third-party packaging services, freight, labor costs for personnel involved in the manufacturing process, and indirect overhead costs. Raw and intermediate materials that may be utilized for both commercial and clinical programs are identical and given the alternative future use such amounts are initially classified as inventory. Amounts in inventory associated with clinical development programs are charged to research and development expense when the product enters the research and development process and can no longer be used for commercial purposes and, therefore, does not have an alternative future use. The Company capitalizes inventory costs related to products to be sold in the ordinary course of business. The Company makes a determination of capitalizing inventory costs for a product based on, among other factors, status of regulatory approval, information regarding safety, efficacy and expectations relating to commercial sales and recoverability of costs. For DANYELZA, the Company commenced capitalization of inventory at the receipt of FDA approval. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment occurs. Such impairment charges, should they occur, are recorded within cost of goods sold. The determination of whether inventory costs will be realizable requires estimates by management. The Company had inventory write-offs totaling $831,000 and $1,200,000 in the years ended December 31, 2023 and 2022, respectively, which were each recorded in cost of goods sold on the Consolidated Statements of Net Loss and Comprehensive Loss. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. ​ ● Level 1 — Unadjusted quoted prices for identical assets or liabilities in active markets; ● Level 2 — Inputs other than quoted prices in active markets for identical assets and liabilities that are observable either directly or indirectly for substantially the full term of the asset or liability; and ● Level 3 — Unobservable inputs for the asset or liability, which include management's own assumption about the assumptions market participants would use in pricing the asset or liability, including assumptions about risk. Cash equivalents held in money market funds are valued using other significant observable inputs, which represent a Level 2 measurement within the fair value hierarchy. The Company has no other cash equivalents. The following tables present the Company’s fair value hierarchy for cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2023 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 Total ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965 Total ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965 ​ During the years ended December 31, 2023 and 2022, there were no transfers between Level 1, Level 2 and Level 3. Operating Lease Right-of-Use Assets and Operating Lease Liabilities The Company determines if an arrangement includes a lease at inception. Operating lease right-of-use assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses an estimated incremental borrowing rate based on information available at the lease commencement date. Because most of the Compnay’s leases do not provide an implicit rate of return, an incremental borrowing rate is used based on the information available at the commencement date in determining the present value of lease payments on an individual lease basis. The Company’s incremental borrowing rate for a lease is the estimated rate of interest the Company would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. The Company’s leases may include options to extend or terminate a lease which are included in the lease term when it is reasonably certain that the Company will exercise any such options. None of the Company’s leases contain any residual value guarantees. Lease expense is recognized on a straight-line basis over the expected lease term. Related variable lease costs incurred are not material to the Company. The Company currently elects the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize right-of-use assets or liabilities. The Company also elects the practical expedient to not separate lease and non-lease components for all of our leases. The Company has made an accounting policy election to account for each separate lease component of a contract and its associated non-lease components as a single lease component. See the Lease Agreements section in NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS Revenue Recognition To determine revenue recognition for product revenue and license revenue arrangements that the Company determines are within the scope of ASC 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 (or as) the Company satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract with a customer under ASC 606, including when it is probable that the Company will collect the consideration the Company is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Under the practical expedient permitted under Topic 606, the Company expenses incremental costs of obtaining a contract as and when incurred if the expected amortization period of the assets is one year or less. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company combines that good or service with other promised goods or services until the Company identifies a bundle of goods or services that is distinct. The standalone selling price is generally determined based on the prices charged to customers. Product revenue, net The Company recognizes revenue from sales of DANYELZA at a point in time when customer is deemed to have obtained control of the product, which generally occurs upon receipt at the end-user hospital for sales in the United States, and upon delivery to the distributors for sales in the international territories. The amount of revenue the Company recognizes from sales of DANYELZA varies due to rebates, chargebacks and discounts provided under governmental and other programs, distribution-related fees and other sales-related deductions. In order to determine those deductions, the Company estimates, utilizing the expected value method, the amount of revenue that the Company will ultimately be entitled to. This estimate is based upon contracts with customers and government agencies, statutorily-defined discounts applicable to government-funded programs, estimated payor mix, and other relevant factors. Calculating these amounts involves estimates and judgments, and the Company reviews these estimates quarterly. If actual results vary from the Company’s original estimates, the Company will adjust these estimates quarterly, which would affect net product revenue and earnings in the period such variances occur. ● Rebates and chargebacks The Company contracts with United States governmental agencies to ensure that DANYELZA will be eligible for coverage under the various programs administered by the agencies. The Company estimates the rebates and chargebacks to be provided and deducts these estimated amounts from gross product revenues. These reserves are recorded in the same period the revenue is recognized, resulting in a reduction of product revenue and the establishment of accrued liabilities for the rebates and a reduction of accounts receivable for the chargebacks. The Company develops estimates for rebates and chargebacks based upon (i) the Company’s contracts with these agencies, (ii) the government-mandated discounts applicable to government-funded programs, and (iii) information obtained from hospitals and third-party consultants regarding the payor mix. The Company’s liability for these rebates and chargebacks mainly consists of claims for which invoices have not yet been received and paid. The Company does not maintain material levels of inventory in the wholesale or retail channel. ● Discounts and distribution-related fees The Company provides invoice discounts on DANYELZA sales to distributors for prompt payment and fees for distribution services and invoice discounts reduce the original accounts receivable balances. The payment terms for sales to distributors generally include a 2% discount for prompt payment or fees for distribution services which are based on contractual rates agreed with the respective distributors. Based on historical data and experiences with the distributors, the Company expects the distributors to earn these discounts and fees and deduct the full amount of these discounts and fees from the Company’s gross product revenue at the time such revenues are recognized. ● Returns The Company offers customers limited product return rights for damaged, defective, or expiring products. The Company estimates returns on sales of DANYELZA mainly based on information provided to the Company from the hospitals and distributors. The return reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. In December 2022, the Company announced a distribution agreement with WEP Clinical Ltd., or WEP, in connection with an early access program for DANYELZA in Europe. There are no regulatory-based or sales-based milestone payments or royalty arrangements under this distribution agreement. The Company recognizes revenue when WEP obtains control of the product upon delivery. The Company invoices WEP based on the terms of the distribution agreement, where a portion is billed upon shipment of product and the unbilled portion is billed at a later date based on terms of the distribution agreement. The Company has an unconditional right to the unbilled portion of the receivable and the Company estimates that the receivable will be collected within one year and therefore has recorded the balance at December 31, 2023, within accounts receivable on the Consolidated Balance Sheets. License revenue The Company’s license agreements include regulatory-based milestone payments and sales-based milestone payments, in addition to royalties. The Company determines whether the achievement of each regulatory-based milestone is constrained as they are contingent upon regulatory approvals, which are not within the control of the Company and therefore not deemed probable. The Company expects that the sales-based milestones and royalty payments will be recognized when the milestone is achieved or the related sales occur. The Company re-evaluates the transaction price each quarter and as uncertain events are resolved or other changes in circumstances occur, the Company assesses whether this resolves the constraint and it is appropriate to recognize revenue. In December 2020, the Company entered into a development and commercialization arrangement with SciClone International Pharmaceuticals Ltd., or SciClone, for certain indications of DANYELZA and omburtamab for Greater China, including Mainland China, Taiwan, Hong Kong and Macau. Based on the terms of the agreement, the Company may receive regulatory-based milestone payments up to $40,000,000, of which $15,000,000 has already been recognized and received in December 2022 for the conditional approval of DANYELZA in China, and sales-based milestone payments up to $60,000,000 and is entitled to royalties based upon the net sales generated by SciClone related to the product indications in the territory. The Company expects that the remaining regulatory-based and sales-based milestones will be recognized when each milestone is achieved. In November 2020, the Company entered into an exclusive license and distribution agreement for DANYELZA and omburtamab with Takeda Israel, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited covering the State of Israel, West Bank and Gaza Strip. Based on the terms of the arrangement, the Company may receive regulatory-based milestone payments up to $750,000, of which $250,000 has already been recognized, and sales-based milestone payments up to $500,000 and is entitled to royalties based upon the net sales generated by Takeda related to the product in the territory. The Company expects that the remaining regulatory-based and sales-based milestones will be recognized when the milestone is achieved, or the related sales occur. In December 2020, the Company entered into a distribution agreement for DANYELZA and omburtamab with Swixx BioPharma AG for the Eastern European territories Bosnia & Herzegovina, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Russia, Serbia, Slovakia and Slovenia. There are no regulatory-based or sales-based milestone payments or royalty arrangements under this distribution agreement. In May 2021, the Company entered into an exclusive distribution agreement with Adium Pharma S.A. (“Adium”) for Adium to be the exclusive distributor in Latin America of the Company’s antibodies omburtamab, if approved, and DANYELZA. Under the terms of the agreement, the Company may receive regulatory-based milestone payments up to $3,000,000, of which $1,000,000 was received in April 2022 upon the submission of the updated FDA BLA dossier for DANYELZA. In addition, the Company is entitled to royalties based upon DANYELZA net sales generated by Adium in Latin America. The agreement with Adium does not contain a regulatory-based milestone related to the Brazilian Health Regulatory Agency’s approval for marketing authorization, which was granted during the three months ended June 30, 2023. During the year ended December 31, 2023, the Company recognized $500,000 in regulatory-based license revenue from Adium pursuant to the distribution agreement in connection with the September 2023 achievement of marketing authorization for DANYELZA in Mexico. In January 2024, the Company accepted the price approval for the first product in Brazil from the Brazilian Medicines Market Regulation Chamber, or CMED. The Company received $0.5 million regulatory-based payment from Adium in connection with the price approval from CMED in the first quarter of 2024. The Company expects that the sales-based milestones and royalty payments will be recognized when and if the milestones are achieved or the related sales occur. In December 2022, the Company announced a distribution agreement with WEP Clinical Ltd., or WEP, in connection with an early access program for DANYELZA in Europe. There are no regulatory, or sales-based milestone payments or royalties under this distribution agreement. Segment Information The Company is engaged solely in operations related to the discovery, development, distribution and commercialization of novel antibody-based therapeutic products for the treatment of cancer, which the Company defines as one operating segment. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: ​ ​ ​ ​ ​ Estimated Useful Life Furniture and fixtures 5 years Machinery and equipment ​ 5 years Leasehold improvements Shorter of life of lease or 15 years ​ Depreciation expense on property and equipment was $386,000 and $662,000 for the years ended December 31, 2023 and 2022. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are expensed as incurred. Impairment of Long-Lived Assets ASC 360, Property, Plant and Equipment, addresses the financial accounting and reporting for impairment or disposal of long-lived assets. The Company reviews the recorded values of long-lived assets for impairment whenever events or changes in business circumstance indicate that the carrying amount of an asset or group of assets may not be fully recoverable. During the year ended December 31, 2022, the Company recorded an impairment charge of $617,000 to write-off the net book value of fixed assets that were related to the production of omburtamab, which did not receive FDA regulatory approval, as the equipment has no alternative use. The impairment charge was recorded within research and development expense within the Company’s Consolidated Statements of Net Loss and Comprehensive Loss and foreign currency and other transactions within the Company’s Consolidated Statements of Cash Flows. The Company did not have impairment of long-lived assets for the year ended December 31, 2023. Provision for Income Taxes The Company accounts for income taxes under the asset and liability approach for the financial accounting and reporting of income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to net operating loss carry forwards and temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. These assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which the temporary differences are expected to reverse. The Company maintains a full valuation allowance on deferred tax assets based on cumulative historical and expected losses. If the Company achieves profitability, the Company will consider the continued need for such a full valuation allowance. Tax returns are prepared and filed based on the Company’s interpretation of tax laws and regulations. In the normal course of business, the Company’s tax returns are subject to examination by various taxing authorities. Such examinations may result in future tax and interest assessments by these taxing authorities. In determining the Company’s provision for income taxes for financial reporting purposes, the Company establishes a reserve for uncertain tax positions unless such positions are determined to be more likely than not of being sustained upon examination based on their technical merits. The Company considers many factors when evaluating and estimating tax positions and tax benefits, which may require periodic adjustments and which may not accurately anticipate actual outcomes. Accordingly, the Company will report a liability for unrecognized tax benefits resulting from any uncertain tax positions taken or expected to be taken on a tax return. The Company’s policy is to recognize, when applicable, interest and penalties on uncertain tax positions as part of income tax expense. In accordance with guidance issued by Financial Accounting Standards Board (“FASB”), companies should make and disclose a policy election as to whether they will recognize deferred taxes for basis differences expected to reverse as Global Intangible Low-Taxed Income (“GILTI”) or whether they will account for GILTI as period costs if and when incurred. The Company has elected to recognize the resulting tax with respect to the GILTI provision as a period cost. No costs were incurred by the Company through December 31, 2023 as a result of GILTI. Research and Development Research and development costs are charged to operations when incurred and are included in operating expenses. Research and development costs consist principally of compensation cost for the Company’s employees and consultants that perform research activities, the fees paid to maintain licenses, the payments to third-party CMOs and CROs for manufacturing and services performed for products in development, and consumables and other materials used in research and development. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of accrued liabilities, we analyze progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Actual results could differ from our estimates. Additionally, the Company is obligated to make certain royalty and clinical, regulatory and sales-based milestone payments in accordance with the contractual terms of the MSK License, CD33 License, MabVax Sublicense, and SADA License based upon the resolution of certain contingencies. The Company records the clinical and regulatory milestone payments when the achievement of the milestones or payment of the milestones is deemed probable, and the amount of the payment is reasonably estimable. As it relates to clinical and regulatory milestone payments under the licensing arrangements, those may become due and payable with the passage of time whether or not the milestones have actually been met. When evaluating whether milestones should be recognized under the licensing arrangements, the Company relies on the collective clinical experience within the organization to determine the likelihood of achievement, as well as the current stage of the compounds under development, estimates of the progress of the Company’s preclinical studies and clinical trials, completion of milestone events per underlying agreements, the time expected to complete certain development activities, each party’s termination right under the license agreements, invoices received and contracted costs when evaluating whether the clinical milestones should be recognized in each reporting period. The Company reviews estimates each period and determines whether to make revisions to such estimates as necessary. Selling, General and Administrative The Company expenses selling, general, and administrative costs as incurred. Selling, general and administrative costs consist primarily of salaries, bonus, benefits, and stock-based compensation expenses for personnel in executive, commercial, finance and administrative functions. Other significant costs include costs of commercialization of DAYNELZA, costs of legal matters and insurance. Other significant costs for 2022 also included commercial cost related to the potential launch of omburtamab in 2022. Advertising and promotion costs are included in selling, general, and administrative expenses and were immaterial in the years ended December 31, 2023 and 2022. Advertising and product promotion costs are expensed as incurred. Stock-Based Compensation The Company measures stock options granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards, over the requisite service period, which for employees and directors is the vesting period of the respective award. Forfeitures are accounted for as they occur. The Company issues stock options with only service-based or immediate vesting conditions and records the expense for these awards using the straight-line method over the requisite service period. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company’s public trading commenced in September 2018, and, as a result, there is limited available historical volatility experience. Therefore, we estimate our expected share price volatility based on the weighting of our own volatility in the estimation with the historical volatility of a group of publicly traded peer companies, and we expect to continue to do so until such time as we have adequate historical data regarding the volatility of our own traded share price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards as the Company has limited historical data to support the expected term assumption. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The expected dividend yield is based on the fact that the Company has never paid cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future. The fair value of restricted stock units is determined at the grant-date price of the Company’s common stock. Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with shareholders. The difference between net loss and comprehensive loss for the period presented in the accompanying consolidated financial statements was due to foreign currency translation. Foreign Currency The consolidated financial statements of the Company’s international subsidiary with a functional currency other than the U.S. dollar is translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates during the period for operating results. Translation gains and losses are included in Accumulated Other Comprehensive Income/(Loss) in the Consolidated Statement of Net Loss and Comprehensive Loss. The Company recognized foreign currency translation losses of $882,000 and $40,000 for the years ended December 31, 2023 and 2022, respectively. Foreign currency transaction gains and losses are included in interest and other income/(loss), net, in the Consolidated Statements of Net Loss and Comprehensive Loss. The Company recorded a foreign currency transaction gain of $524,000 and a foreign currency transaction loss of $848,000 for the years ended December 31, 2023, and 2022, respectively. Earnings Per Share The Company reports net earnings per share in accordance with ASC 260, Earnings per Share. Basic net loss per share (“EPS”) is calculated by dividing net income or loss attributable to common stockholders by the weighted average common stock outstanding. Diluted EPS is calculated by adjusting weighted average common shares outstanding for the dilutive effect of common stock options and restricted stock units. In periods in which a net loss is recorded, no effect is given to potentially dilutive securities, since the effect would be antidilutive. Similarly, securities that could potentially dilute basic EPS in the future are not included in the computation of diluted EPS because to do so would have been antidilutive. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, and are adopted by the Company as of the specific effective date. The Company adopted ASU 2022-04, ASU 2022-02, ASU 2022-01 and ASU 2021-08 effective January 1, 2023, and the adoption of these new standards did not have a material impact on the Company’s consolidated financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09, Improvement to income tax disclosures (Topic 740). ASU 2023-09 addresses annual disclosures related to the income tax rate reconciliation and the income taxes paid within the tax note. ASU 2023-09 requires consistent categories and greater disaggregation of information in the income tax rate re

PRODUCT REVENUE, NET

PRODUCT REVENUE, NET	12 Months Ended
	Dec. 31, 2023
PRODUCT REVENUE, NET
PRODUCT REVENUE, NET	NOTE 4—PRODUCT REVENUE, NET The Company’s product revenue, net was generated from sales of DANYELZA and consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ United States ​ $ 67,814 ​ $ 46,259 Other countries ​ ​ 16,505 ​ ​ 3,008 Total product revenue, net ​ $ 84,319 ​ $ 49,267 ​ The majority of the Company’s product sales were in the United States with additional sales in China, Europe, Latin America and Israel through sublicenses and distribution agreements. The Company’s product revenue, net from other countries for the year ended December 31, 2023, included $8,621,000 of product revenue, net from the Company’s distribution partner, WEP. The Company’s product revenue, net from other countries for the year ended December 31, 2023, also included $3,535,000 of product revenue and related royalties for the commercial launch initial inventory stocking order from the Company’s distribution partner, SciClone, which launched commercial sales in China in June 2023. The Company recognized royalty revenue from the distribution partners of $4,453,000 and $2,120,000 in the years ended December 31, 2023 and 2022, respectively. The Company had product sales to certain customers that accounted for more than 10% of total product revenue, net for the years ended December 31, 2023 and 2022. McKesson, AmerisourceBergen, WEP and Cardinal Health accounted for 46%, 22%, 10% and 13%, respectively, of the Company’s product revenue, net for the year ended December 31, 2023. McKesson, AmerisourceBergen, and Cardinal Health accounted for 71%, 17%, and 10%, respectively, of the Company’s product revenue, net for the year ended December 31, 2022. As of December 31, 2023, the Company has recorded on the Consolidated Balance Sheets accounts receivable of approximately $5,834,000, of which $3,684,000 represents an unbilled portion to which we have unconditional rights to collect the consideration, and accrued liabilities of $326,000 related to product sales to WEP during the year ended December 31, 2023. ​ Revenue from product sales is recorded net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions. Accruals for chargebacks and discounts are recorded as a direct reduction to accounts receivable. Accruals for rebates, distribution-related fees without contractual right of offset and other sales-related deductions are recorded within accrued liabilities. As of December 31, 2023, the Company had recorded accounts receivable allowances of approximately $492,000 and accrued liabilities of $2,309,000 related to product sales. As of December 31, 2022, the Company had recorded accounts receivable allowances of approximately $508,000 and accrued liabilities of $2,474,000 related to product sales. ​ An analysis of the change in reserves for discounts and allowances is summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ ​ ​ ​ Discounts ​ Government Rebates Returns ​ Total ​ ​ Balance December 31, 2022 $ 33 ​ $ 2,905 ​ $ 44 ​ $ 2,982 Current provisions relating to sales in current year ​ 238 ​ ​ 8,361 ​ ​ 519 ​ ​ 9,118 Payments/credits relating to sales in current year ​ (230) ​ ​ (7,482) ​ ​ (497) ​ ​ (8,209) Change in estimate related to sales in the prior year ​ — ​ ​ (1,090) ​ ​ — ​ ​ (1,090) Balance December 31, 2023 $ 41 ​ $ 2,694 ​ $ 66 ​ $ 2,801 ​ During the year ended December 31, 2023, the Company recorded a change in estimate related to assessed Medicaid claims data experience and reserves for historical earned periods. The change in estimate resulted in a benefit of $1,090,000 for the year ended December 31, 2023.

NET LOSS PER SHARE

NET LOSS PER SHARE	12 Months Ended
	Dec. 31, 2023
NET LOSS PER SHARE
NET LOSS PER SHARE	NOTE 5—NET LOSS PER SHARE The calculations of basic and diluted net loss per share are as follows (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss (numerator) ​ $ (21,427) ​ $ (95,568) ​ Weighted-average shares (denominator), basic and diluted ​ 43,645 ​ 43,704 ​ Basic and diluted net loss per share ​ $ (0.49) ​ $ (2.19) ​ ​ Potentially dilutive securities excluded from the computation of diluted earnings per share relate to stock options and unvested restricted share units outstanding totaled 9,658,737 shares and 7,113,122 shares as of December 31, 2023 and 2022, respectively.

INVENTORIES

INVENTORIES	12 Months Ended
	Dec. 31, 2023
INVENTORIES
INVENTORIES	NOTE 6—INVENTORIES Inventories consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 Work In Progress ​ $ 14,021 ​ $ 11,317 Finished Goods ​ ​ 2,992 ​ ​ 666 Total Inventories ​ $ 17,013 ​ $ 11,983 ​ ​ ​ ​ ​ ​ ​ ​ Inventories are classified on the Consolidated Balance Sheets in each respective period (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 CURRENT ASSETS ​ ​ ​ ​ ​ ​ Inventories ​ $ 5,065 ​ $ 6,702 Total recorded in Current Assets ​ ​ 5,065 ​ ​ 6,702 ​ ​ ​ ​ ​ ​ ​ NONCURRENT ASSETS ​ ​ ​ ​ ​ ​ Other assets ​ ​ 11,948 ​ ​ 5,281 Total recorded in Noncurrent Assets ​ ​ 11,948 ​ ​ 5,281 Total Inventories ​ $ 17,013 ​ $ 11,983 ​ As of December 31, 2023 and 2022, the Company has classified $11,948,000 and $5,281,000, respectively, of work in progress inventories as noncurrent assets based on the Company’s current demand schedule and expectation that such inventory will be utilized after one year from the balance sheet date. Changes in noncurrent assets are reflected on the Consolidated Statements of Cash Flows within the caption of other assets. During the year ended December 31, 2023 and 2022, the Company recorded charges to write off inventory of $831,000 and $1,200,000, respectively.

INTANGIBLE ASSETS, NET

INTANGIBLE ASSETS, NET	12 Months Ended
	Dec. 31, 2023
INTANGIBLE ASSETS, NET
INTANGIBLE ASSETS, NET	NOTE 7— INTANGIBLE ASSETS, NET The Company’s intangible assets, net as of December 31, 2023 totaled $2,631,000 , net of $669,000 of accumulated amortization. The Company’s intangible assets, net as of December 31, 2022 totaled $2,986,000 , net of $314,000 of accumulated amortization. The Company recognized an intangible asset of $1,500,000 for the royalty payable to MSK in 2022 for their share of the regulatory-based milestone payment of $15,000,000 by SciClone for the conditional approval of DANYELZA in China. The Company’s intangible assets, net related to capitalized milestone payments made following FDA and other regulatory approvals, and commercialization of DANYELZA. Intangible assets are amortized on a straight-line basis based on a 10-year each year for year

ACCRUED LIABILITIES

ACCRUED LIABILITIES	12 Months Ended
	Dec. 31, 2023
ACCRUED LIABILITIES
ACCRUED LIABILITIES	NOTE 8—ACCRUED LIABILITIES Accrued liabilities as of December 31, 2023 and December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ Accrued licensing, milestone and royalty payments ​ $ 3,452 ​ $ 4,002 Accrued clinical costs ​ 597 ​ 932 Accrued compensation and board fees ​ 3,858 ​ 2,445 Accrued manufacturing costs ​ ​ 2,531 ​ ​ 2,977 Accrued sales reserves ​ ​ 2,309 ​ ​ 2,474 Other ​ 419 ​ 411 Total ​ $ 13,166 ​ $ 13,241 ​

LICENSE AGREEMENTS AND COMMITME

LICENSE AGREEMENTS AND COMMITMENTS	12 Months Ended
	Dec. 31, 2023
LICENSE AGREEMENTS AND COMMITMENTS
LICENSE AGREEMENTS AND COMMITMENTS	NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS The Company has entered into three license agreements and certain other agreements with Memorial Sloan Kettering Cancer Center (“MSK”). The license agreements include the MSK License Agreement, dated August 20, 2015, between the Company and MSK (the “MSK License”), and the CD33 License Agreement, dated November 13, 2017, between the Company and MSK (the “CD33 License”). Through the Settlement and Assumption and Assignment of the MSK License and Y-mAbs Sublicense Agreement, dated December 2, 2019, among MabVax Therapeutics Holdings, Inc. and MabVax Therapeutics, Inc., (together “MabVax"), the Company and MSK (the “SAAA”), the Company has established a direct license with MSK relating to the GD2-GD3 Vaccine, which was originally sublicensed by the Company in 2018 from MabVax. In addition, the Company entered into a license agreement, dated April 15, 2020, with MSK and Massachusetts Institute of Technology (“MIT”) (the “SADA License Agreement”). These license agreements with MSK and MIT grant the Company certain patent rights and intellectual property rights, and in consideration thereof, the Company agreed to make certain payments and issue shares of the Company’s common stock to MSK and MIT. Certain payments are contingent milestone and royalty payments, as disclosed in the table below. Amounts disclosed in NOTE 8—ACCRUED LIABILITIES In the past, the Company had defined MSK as a related-party under the Company’s related-party policy. During the year ended December 31, 2023, the Company updated the related-party policy to remove MSK as a related-party as MSK does not participate on the Company’s Board of Directors, does not have a significant ownership in the Company, and is not in a position to exert decision making power. MSK License The MSK License relates to intellectual property for DANYELZA and requires the Company to pay to MSK mid to high single-digit royalties based on annual net sales of licensed products or the performance of licensed services by the Company and the Company’s affiliates and sublicensees. The Company is required to pay annual minimum royalties of $80,000 over the royalty term, which amounts are non-refundable but are creditable against royalty payments otherwise due thereunder. The Company is also obligated to pay to MSK certain clinical, regulatory and sales-based milestone payments under the MSK License, which payments become due at the earlier of completion of the related milestone activity or the date indicated in the MSK License even if the related milestone activity is not achieved. In addition, to the extent the Company enters into sublicense arrangements, the Company is required to pay to MSK a percentage of certain payments that the Company receives from sublicensees of the rights licensed to the Company by MSK, which percentage will be based upon the date the Company receives such payments or the achievement of certain clinical milestones. The Company has entered into sublicenses and distribution agreements related to DANYELZA and omburtamab under the MSK License with Takeda Israel, Swixx BioPharma AG and SciClone in 2020, with Adium in 2021 and WEP Clinical Ltd. In 2022. The terms of the MSK License provide that MSK is entitled to receive 40% of the income generated from the sale of first PRV, and 33% of any income generated from the sale of any subsequent PRV or the sale of other comparable incentives provided by any non U.S. jurisdiction. The Company sold the first PRV in connection with DANYELZA, and collected the proceeds in January 2021. The MSK License will expire, on a country by country basis, and on a licensed product by licensed product or licensed service by licensed service basis, on the later of (i) the expiration of the last to expire of the patents and patent applications covering such licensed product or service in such country, (ii) the expiration of any market exclusivity period granted by a regulatory authority for such licensed product or service in such country, or (iii) 15 years from the first commercial sale of such licensed product or service in such country. MSK may terminate the MSK License upon prior written notice in the event of our uncured material breach, or upon prior written notice if such breach is of a payment obligation. MSK may also terminate the MSK License upon written notice in the event of our bankruptcy or insolvency or our conviction of a felony relating to the licensed products, or if the Company challenges the validity or enforceability of any licensed patent right. In addition, the Company has the right to terminate the MSK License in its entirety at will upon prior written notice to MSK, but if the Company has commenced the commercialization of licensed products and/or licensed services the Company can only terminate at will if the Company ceases all development and commercialization of such licensed products and/or licensed services. The Company’s failure to meet certain conditions under the MSK License could cause the related license to such licensed product to be canceled and could result in termination of the MSK License by MSK. CD33 License The CD33 License grants the Company a worldwide, sub licensable license to MSK’s rights in certain patent rights and intellectual property rights related to certain know how to develop, make and commercialize licensed products and to perform services for all therapeutic and diagnostic uses in the field of cancer diagnostics in connection with certain CD33 antibodies generated in a specific principal investigator’s laboratory at MSK and constructs thereof. The CD33 License is exclusive with respect to such patent rights and tangible materials within such know how, and nonexclusive with respect to MSK’s rights in such know how and related intellectual property rights. As product candidates progress through clinical development, regulatory approval and commercialization, certain milestone payments will come due either as a result of the milestones having been met or the passage of time even if the milestones have not been met. In addition, the CD33 License contains minimum royalty payments that become due beginning in year 10 of $40,000 per year over the royalty term, increasing to $60,000 once a patent within the licensed rights is issued, subject to increase and creditable against any royalty payments due based on sales in the future. The Company is required to pay mid to high single digit royalties on sales of licensed products. Additionally, the terms of the CD33 License provide that MSK is entitled to receive 25% of any income generated from the sale of any PRV or the sale of other comparable incentives provided by any non U.S. jurisdiction. The MSK CD33 License will expire, on a country by country basis, and on a licensed-product by licensed-product or licensed service by licensed service basis, on the later of (i) the expiration of the last to expire of the patents and patent applications covering such licensed product or service in such country, (ii) the expiration of any market exclusivity period granted by a regulatory authority for such licensed product or service in such country, or (iii) 15 years from the first commercial sale of such licensed product or service in such country. MSK may terminate the CD33 License upon prior written notice in the event of our uncured material breach, or upon prior written notice if such breach is of a payment obligation. MSK may also terminate the CD33 License upon written notice in the event of the Company’s bankruptcy or insolvency or the Company’s conviction of a felony relating to the licensed products, or if the Company challenges the validity or enforceability of any licensed patent right. In addition, the Company has the right to terminate the CD33 License in its entirety at will upon prior written notice to MSK, but if the Company has commenced the commercialization of licensed products and/or licensed services the Company can only terminate at will if the Company ceases all development and commercialization of such licensed products and/or licensed services. MabVax/MSK License Pursuant to the SAAA, the Company is granted certain patent rights and know-how for development and commercialization of products for the prevention or treatment of NB by means of administering a bi-valent ganglioside vaccine. Pursuant to the SAAA, the Company is required to pay development milestones and mid-single digit royalty payments to MSK. In addition, if the Company obtains FDA approval for the GD2-GD3 Vaccine, then the Company is obligated to file with the FDA for a PRV. The SAAA stipulates that, if the Company is granted a PRV from the FDA covering a licensed product under the MabVax/Y-mAbs Sublicense and the PRV is subsequently sold, the Company will pay directly to MSK a total of 20% of the proceeds from the sale thereof. The MabVax License Agreement will expire with effect for the Company, on a country-by-country basis, on the later of the expiration of (i) 10 years from the first commercial sale of the licensed product in such country or (ii) the last to expire valid claim covering such licensed product rights at the time of and in the country of sale. SADA License Pursuant to the SADA License Agreement, the Company was granted an exclusive worldwide, sublicensable license to MSK’s and MIT’s rights to certain patent and intellectual property to develop, make, and commercialize licensed products and to perform services for all therapeutic and diagnostic uses in the field of cancer diagnostics and cancer treatments using the Self-Assembly DisAssembly Pretargeted, or SADA PRIT, technology platform. The SADA License Agreement requires the Company to pay MSK and MIT mid to high single-digit royalties based on annual net sales of licensed products or the performance of licensed services by the Company and the Company’s affiliates and sublicensees. The Company is obligated to pay non-refundable annual minimum royalties of $40,000, increasing to $60,000 once a patent has been issued, over the royalty term, commencing on the tenth anniversary of the license agreement. The Company is also obligated to pay MSK and MIT certain clinical, regulatory and sales-based milestone payments under the SADA License Agreement. Certain clinical and regulatory milestone payments become due at the earlier of completion of the related milestone activity or the date indicated in the SADA License Agreement even if the related milestone activity is not achieved. In addition, to the extent the Company enters into sublicense arrangements, the Company is obligated to pay to MSK and MIT a percentage of certain payments received from sublicensees of the rights licensed to us by MSK and MIT, which percentage will be based upon the achievement of certain clinical milestones. The Company has not entered into any sublicenses related to the SADA License Agreement. For each of the constructs previously generated by MSK using the SADA PRIT Technology and sold for the Company by a sublicensee, the Company may pay sales milestones up to $60,000,000, in total, based on the achievement of various levels of cumulative net sales made by the sublicensee. The Company recognized an expense of $4,125,000 related to clinical milestones under the SADA License Agreement during the year ended December 31, 2023, as the Company determined certain time-based clinical milestones within the agreement are probable based on the availability of necessary data and the assessment of clinical progress. The Company did not recognize any expenses related to milestones under the SADA License Agreement during the year ended December 31, 2022. The Company made a final $1,000,000 license continuation payment under the SADA License Agreement in the year ended December 31, 2022. The Company had current liabilities of $1,000,000 and $605,000 in accrued liabilities as of December 31, 2023 and 2022, respectively. The Company had non-current liabilities of $3,125,000 in accrued milestone and royalty payments as of December 31, 2023. The Company made a payment of $605,000 in the year ended December 31, 2023, related to achievement of the milestone for dosing the first patient in the Phase 1 trial of GD2-SADA in April 2023. Failure by the Company to meet certain conditions under the arrangement could cause the related license to such licensed products to be canceled and could result in termination of the entire arrangement with MSK and MIT. In addition, the Company may terminate the SADA License Agreement with prior written notice. Summary of Significant License Agreements and Related Commitments The below table represents the maximum clinical, regulatory or sales-based milestones as reflected within the significant license agreements, certain of which have been paid in prior periods or are accrued as presented in the table below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maximum Maximum Maximum ​ ​ Clinical ​ Regulatory ​ Sales-based Agreements ​ Milestones ​ Milestones ​ Milestones MSK ​ ​ $ 2,450 ​ ​ $ 9,000 ​ ​ $ 20,000 CD33 ​ ​ 550 ​ ​ 500 ​ ​ 7,500 MabVax ​ ​ 200 ​ ​ 1,200 ​ ​ — SADA ​ ​ 4,730 ​ ​ 18,125 ​ ​ 23,750 The below table represents all obligations pertaining to the significant license agreements that have been paid, expensed or accrued as of and for the years ended December 31, 2023 and 2022 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid Cash paid Expense Expense ​ Accrued Accrued Accrued Accrued ​ ​ Twelve ​ Twelve ​ Twelve ​ Twelve ​ liabilities liabilities liabilities liabilities ​ ​ months ​ months ​ months ​ months ​ Current ​ Non-current ​ Current ​ Non-current ​ ​ ​ ended ​ ended ​ ended ​ ended ​ as of ​ as of ​ as of ​ as of ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ Agreements ​ 2023 ​ 2022 ​ 2023 ​ 2022 ​ 2023 ​ 2023 ​ 2022 ​ 2022 ​ MSK ​ $ 6,027 ​ $ 2,871 ​ $ 5,158 ​ $ 3,582 ​ $ 2,452 ​ $ 1,950 ​ $ 3,397 ​ $ 1,950 ​ CD33 ​ ​ — ​ ​ 150 ​ ​ — ​ ​ — ​ ​ — ​ ​ 300 ​ ​ — ​ ​ 300 ​ MabVax ​ ​ 10 ​ ​ 10 ​ ​ 10 ​ ​ 10 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ SADA ​ ​ 605 ​ ​ 1,000 ​ ​ 4,125 ​ ​ — ​ ​ 1,000 ​ ​ 3,125 ​ ​ 605 ​ ​ — ​ ​ Minimum royalties and certain clinical, regulatory and sales milestones that become due based upon the passage of time under the MSK License Agreement, CD33 License Agreement, the MabVax Agreement, and the SADA License Agreement are excluded from the above table as the Company does not consider such obligations to be probable as of December 31, 2023 and December 31, 2022. Research and development is inherently uncertain and should such research and development fail, the MSK License Agreement, the CD33 License Agreement, the SADA License Agreement and the MabVax License Agreement as well as the MabVax/Y-mAbs Sublicense are cancelable at the Company’s option. The Company will also consider the development risk and each party’s termination rights under the respective agreement when considering whether any clinical or regulatory-based milestone payments, certain of which also contain time-based payment requirements, are probable. The Company records milestones in the period in which the contingent liability is probable and the amount is reasonably estimable. Other agreements The Company has also entered into various other support agreements with MSK including a sponsored research agreement to provide research services related to the intellectual property licensed under the MSK License Agreement; a master data services agreement, for services provided up to approximately five full-time employees at MSK, who are engaged in transferring clinical data, databases, regulatory files and other know-how included in the MSK License Agreement to the Company; a master clinical trial agreement pursuant to which the Company committed to fund certain clinical trials at MSK; two separate core facility service agreements pursuant to which the Company committed to obtaining certain laboratory services from MSK; and in October 2020 the Company entered into a SADA sponsored research agreement pursuant to which the Company agreed to pay MSK to provide research services over a period of three years related to the intellectual property licensed under the SADA License Agreement. The scientific research took place over a period that commenced in September 2020 and ended in February 2022. For the years ended December 31, 2023 and 2022, the Company incurred research and development expenses of $190,000 and $1,746,000, respectively, under these agreements. Lease Agreements In February 2019, the Company entered into a lease agreement in connection with the Company’s 4,548 square feet laboratory in New Jersey. In December 2019, the Company expanded the space with an additional 235 square feet. The original term of the lease was three years from the date the Company occupied the premises, with an option to extend for an additional two years which was to expire in January 2024, which the Company exercised and had included in the determination of the related lease liability. In July 2023, the Company entered into a lease amendment to extend the term to February 2025. Fixed rent payable under the lease is approximately $177,000 per annum and is payable in equal monthly installments of approximately $15,000 per month. In January 2018, the Company entered into a lease agreement in connection with the Company’s corporate headquarters in New York. The term of the lease was six years from the date the Company began to occupy the premises and the lease was to expire in April 2024. In August 2023, the Company entered into a lease amendment to extend the term to April 2025. Fixed rent payable under the lease is approximately In February 2018, the Company entered into a lease agreement for certain office space in Denmark, which has been amended several times. The lease was renewed on November 1, 2021 with a four-year term that expires in November 2025. The lease is payable in monthly installments of approximately $41,000. In January 2023, the Company notified the landlord of the intention to reduce the leased premise as a result of the Company’s strategic restructuring. The lease modification resulted in an immaterial charge in the year ended December 31, 2023. Total operating lease costs were $1,033,000 and $2,646,000 for the years ended December 31, 2023 and 2022, respectively. For the year ended December 31, 2023, the operating lease expenses were recorded as $780,000 in research and development expense and $253,000 in selling, general and administrative expense. For the year ended December 31, 2022, the expenses were recorded as $2,404,000 in research and development expense and $242,000 in selling, general and administrative expense. Cash paid for amounts included in the measurement of lease liabilities was $1,057,000 and $2,286,000 for the years ended December 31, 2023 and 2022, and were included in net cash used in operating activities in the Company’s Consolidated Statements of Cash Flows. Maturities of operating lease liabilities as of December 31, 2023 and 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Operating Leases ​ as of December 31, 2023 ​ as of December 31, 2022 Years ending December 31, ​ ​ ​ ​ ​ ​ 2023 ​ $ — ​ $ 997 2024 ​ ​ 996 ​ ​ 490 2025 ​ ​ 526 ​ ​ 419 Total lease payments ​ ​ 1,522 ​ ​ 1,906 Less: Imputed interest ​ ​ (103) ​ ​ (139) Total operating lease liabilities as of period end ​ $ 1,419 ​ $ 1,767 ​ Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company estimates the incremental borrowing rate based on the information available at the lease commencement date. As of December 31, 2023, the weighted average remaining lease term is 1.61 years and the weighted average discount rate used to determine the operating lease liability is 8.3%. As of December 31, 2022, the weighted average remaining lease term was 2.36 years and the weighted average discount rate used to determine the operating lease liability was 8.3%. ​ Former Chief Executive Officer Contractual Severance Related Benefits ​ On April 27, 2022, the Company announced certain executive management changes. Effective April 22, 2022, Dr. Claus Juan Møller San Pedro stepped down from his positions as Chief Executive Officer and as a member of the Company’s Board of Directors. There were no disagreements with the Company expressed by Dr. Møller on any matters relating to the Company’s operations, policies or practices. Dr. Møller’s contractual severance related benefits provided for cash compensation of $1,589,000, which included salary and certain benefits continuation. All of the cash compensation had been paid as of December 31, 2022. Also, under terms of the equity award agreement, Dr. Møller’s outstanding stock option awards will continue to vest as scheduled and become exercisable when vested. This resulted in a non-cash share-based compensation charge of $9,286,000 in the year ended December 31, 2022 as there was no longer a service condition related to such awards. The total charge of $10,875,000 related to the executive management change was recorded in selling, general and administrative expenses during the year ended December 31, 2022. There was no financial impact in the year ended December 31, 2023. Legal Matters Donoghue vs. Y-mAbs Therapeutics, Inc., and Gad ​ The Company has been named a nominal defendant in a lawsuit filed in the U.S. District Court, Southern District of New York, on August 25, 2021, by one of the Company’s stockholders, Deborah Donoghue (Case No. 1:21-cv-07182). The suit names the Company’s Chief Business Officer, and Vice Chairman of the Company’s board of directors, Mr. Thomas Gad as an additional defendant, and it seeks to compel Mr. Gad to disgorge alleged short swing profits stemming from a certain transaction involving the Company’s common stock undertaken by Mr. Gad on March 10, 2021 together with appropriate interest and costs of the lawsuit. On December 17, 2021, Mr. Gad filed a Motion to Dismiss the lawsuit. On August 8, 2022, the Court denied Mr. Gad’s Motion to Dismiss the lawsuit. The parties have completed documentary discovery and depositions. On February 1, 2024, both the Plaintiff and Mr. Gad filed their respective motions for summary judgment. The Company is of the opinion that the claim is without merit and intends to maintain this position in the proceedings. In addition, the Company has been informed by Mr. Gad that he also believes the claim is without merit, that he has strong defenses against such claim and that he intends to vigorously defend the action. The Company has assessed the proceedings and does not believe that it is probable that a gain or a liability will be realized by the Company. As a result, the Company did not record any loss or gain contingencies for this matter. ​ In re Y-mAbs Therapeutics, Inc. Securities Litigation On January 18, 2023, a putative class-action lawsuit was filed against the Company and certain of the Company’s current and former officers for alleged violations of the U.S. federal securities laws in the United States District Court, Southern District of New York (Case No.: 1:23-cv-00431). The amended complaint filed on May 23, 2023, asserts claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, on behalf of a proposed class consisting of those who acquired the Company’s common stock between October 6, 2020 and October 28, 2022. The amended complaint alleges that there were material misrepresentations and/or omissions regarding the FDA’s consideration of the Company’s BLA for omburtamab for the treatment of pediatric patients with CNS/leptomeningeal metastasis from neuroblastoma firstly submitted in 2020 and resubmitted in 2022. The amended complaint seeks unspecified damages, and costs and expenses, including attorneys’ fees. On September 29, 2023, the defendants’ motion to dismiss the amended complaint was fully briefed. On February 5, 2024, the Court granted in part and denied in part the defendants’ motion to dismiss. The Court dismissed the plaintiff’s claims relating to Hazelton vs. Y-mAbs Therapeutics Inc., and Gad, et al. ​ The Company has been named a nominal defendant in a lawsuit filed in the Court of Chancery of the State of Delaware, on February 8, 2023, by a purported stockholder, Jeffrey Hazelton (Case No. 2023-0147-LWW). The amended complaint filed on May 12, 2023, purports to bring claims on behalf of the Company against current and former members of the Company’s board of directors for allegedly awarding themselves excessive compensation for fiscal years 2020 and 2021. The amended complaint seeks, among other things, recovery of alleged excessive compensation, an order directing the Company to undertake certain corporate governance reforms, and an award of costs and expenses, including attorneys’ fees. The Court has not yet issued its ruling on the defendants’ motion to dismiss the amended complaint, which was fully briefed as of September 8, 2023. The Company is of the opinion that the claims are without merit and intends to maintain this position in the proceedings. The Company has not established a liability for this claim as of December 31, 2023 as the Company does not consider a loss on the claim to be probable.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2023
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 10—STOCKHOLDERS’ EQUITY Authorized Stock As of December 31, 2023 and 2022, the Company had authorized a total of 105,500,000 shares, 100,000,000 of which are common stock, par value $0.0001 per share, and 5,500,000 of which are preferred stock, par value $0.0001 per share. Common Stock Each share of common stock is entitled to one vote. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to preferential dividend rights of the preferred stock, none of which have been issued. The Company had issued 43,672,112 shares and 43,670,109 shares of common stock as of December 31, 2023 and 2022, respectively. Preferred Stock Preferred stock may be issued from time to time in one or more series with such designations, preferences and relative participating, optional or other special rights and qualifications, limitations or restrictions as approved by the Company’s Board of Directors. No preferred stock has been issued as of December 31, 2023 and 2022. Stock Grant Agreements with Non-Employees In April 2020, in connection with the SADA License Agreement, the Company entered into two stock grant agreements pursuant to which the Company agreed to issue a total of 213,996 shares to two non-employee researchers who were involved in the development of the SADA PRIT in consideration for their respective prior service. All 213,996 shares were issued in April 2020 into escrow with 40% of the shares immediately vesting at the time of issuance and the remaining 60% of the shares subject to vesting ratably over the next three years on the anniversary date of the agreement. The remaining 20% of the award vested in April 2023 resulting in all 213,996 shares being vested as of December 31, 2023. There is no cash settlement feature, and no future service is required for the non-employee researchers to vest and receive the shares on grant date. In April 2020, the Company recognized $7,376,000, the fair value of the issued shares on the grant date, within research and development expense. There is no future expense related to these awards. In July 2020, pursuant to the stock grant agreements, the Company also loaned the two researchers a total of $2,610,000 related to their individual tax payments due in conjunction with the stock grants. Each of the loans are evidenced by a Secured Promissory Note, which had respective maturity dates in April 2023 and June 2023. The outstanding principal amount of each loan, together with all accrued interest thereon at the rate of 1% per annum, was due and payable on the respective maturity dates of the loans. The loans were secured by Pledge and Security Agreements, pursuant to which the researchers pledged the shares as security for repayment of the loans. In July 2022, one of the researchers repaid their loan, which had a maturity date in April 2023, and accrued interest, which resulted in a de minimis loss compared to the amortized cost of the loan, in exchange for 57,887 shares that remained pledged as part of its security. Upon receipt, the Company recorded treasury shares at an acquisition cost of $963,000, based on the share price on the settlement date. The Company subsequently cancelled the acquired treasury shares resulting in a reduction of outstanding common stock and a reduction of additional paid-in-capital totaling $963,000. During the fourth quarter of 2022, the Company concluded that the other loan receivable, with a maturity date of June 2023, was impaired, which resulted in a $1,051,000 charge for the year ended December 31, 2022. In June 2023, the other researcher repaid his loan, which resulted in a de minimis gain compared to the book value of the loan, which included the impact of the previous impairment charge. The loan was repaid in exchange for 58,763 shares that remained pledged as part of its security. Upon receipt, the Company recorded treasury shares at an acquisition cost of $480,000, based on the closing price of the Company’s common stock on the settlement date. The Company subsequently cancelled the acquired treasury shares, which resulted in a reduction of outstanding common stock and a reduction of additional paid-in-capital totaling $480,000. There were no shares issued to non-employee researchers in 2023 and 2022.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2023
STOCK-BASED COMPENSATION
STOCK-BASED COMPENSATION	NOTE 11—STOCK-BASED COMPENSATION 2015 Equity Incentive Plan The Company’s board of directors and stockholders approved and adopted the Amended and Restated 2015 Equity Incentive Plan (the “2015 Plan”), which provided for the grant of incentive stock options, within the meaning of Section 422 of the Code (the Internal Revenue Code), to the Company’s employees and any parent and subsidiary corporations’ employees, and for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock and restricted stock units to the Company’s employees, directors and consultants and the Company’s subsidiary corporations’ employees and consultants. A total of 4,500,000 shares of the Company’s common stock were reserved for issuance pursuant to the 2015 Plan. Options granted under the 2015 Plan vest according to the schedule specified in the grant agreements, which is generally a four-year period and generally become immediately exercisable upon the occurrence of a change in control, as defined. Upon the 2018 Equity Incentive Plan (the “2018 Plan”) becoming effective in September 2018, no further grants are allowed under the 2015 Plan. 2018 Equity Incentive Plan The Company’s board of directors and stockholders approved and adopted the 2018 Equity Incentive Plan (the “2018 Plan”) in connection with the Company’s initial public offering in September 2018. However, options outstanding under the 2015 Plan continue to be governed by the 2015 Plan. The 2018 Plan provides for the grant of incentive stock options, within the meaning of Section 422 of the Code (the Internal Revenue Code), to the Company’s employees and any parent and subsidiary corporations’ employees, and for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock and restricted stock units to the Company’s employees, directors and consultants and the Company’s parent and subsidiary corporations’ employees and consultants. A total of 5,500,000 shares of the Company’s common stock, inclusive of the awards previously granted under the 2015 Equity Incentive Plan were initially reserved for issuance pursuant to the 2018 Plan. In addition, the number of shares available for issuance under the 2018 Plan will also include an annual increase on the first day of each fiscal year beginning in 2019 through 2029, equal to 4% of the outstanding shares of common stock as of the last day of the Company’s immediately preceding fiscal year or by a lesser amount determined by the board of directors. As of December 31, 2023, the Company had 3,107,673 shares available for grant under the 2018 Equity Incentive Plan. The exercise price of options granted under the plans must at least be equal to the fair market value of the Company’s common stock on the date of grant. The term of an incentive stock option may not exceed 10 years , except that with respect to any participant who owns more than 10% of the voting power of all classes of the Company’s outstanding stock, the term must not exceed five years and the exercise price must equal at least 110% of the fair market value on the grant date. The administrator will determine the methods of payment of the exercise price of an option, which may include cash, shares or other property acceptable to the administrator, as well as other types of consideration permitted by applicable law. Options granted under the 2018 Plan vest according to the schedule specified in the grant agreements, which is generally between one and four years and generally become immediately exercisable upon the occurrence of a change in control, as defined in the Plan Agreement. Stock Options During the years ended December 31, 2023 and 2022, stock-based compensation for stock option grants were $13,757,000 and $25,274,000, respectively, for options granted to employees and directors. The expense for the year ended December 31, 2023, was inclusive of an acceleration of stock-based compensation of $1,706,000, as described further in NOTE 14— RESTRUCTURING CHARGE NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS The assumptions that the Company used to determine the fair value of the stock options granted to employees and directors were as follows, presented on a weighted average basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended Year Ended ​ ​ ​ December 31, 2023 ​ December 31, 2022 ​ ​ ​ ​ ​ ​ ​ Risk-free interest rate ​ 3.92 % 3.12 % Expected term (in years) ​ 6.2 5.9 Expected volatility ​ 82.9 % 73.6 % Expected dividend yield ​ — % — % ​ The following table summarizes common stock options issued and outstanding: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted ​ Aggregate ​ average ​ ​ ​ ​ average ​ intrinsic ​ remaining ​ ​ ​ ​ exercise ​ value ​ contractual ​ ​ Options ​ price ​ (in thousands) ​ life (years) Outstanding and expected to vest at December 31, 2022 7,079,767 ​ $ 21.27 ​ $ 3,112 ​ 6.45 Granted 2,586,040 ​ ​ 5.25 ​ ​ ​ ​ ​ Exercised ​ (50,000) ​ ​ 2.00 ​ ​ ​ ​ ​ Forfeited ​ (308,477) ​ ​ 11.10 ​ ​ ​ ​ ​ Outstanding and expected to vest at December 31, 2023 9,307,330 ​ $ 17.26 ​ $ 10,012 ​ 6.44 Exercisable at December 31, 2023 5,958,167 ​ ​ 21.00 ​ ​ 6,195 ​ 5.03 ​ The weighted average fair value of stock options granted during the years ended December 31, 2023 and 2022 was $3.86 and $7.64, respectively. There were 2,586,040 and 653,000 stock options granted for the years ended December 31, 2023 and 2022, respectively. Options granted during the years ended December 31, 2023 and 2022 have a maximum contractual term of ten years. There were 1,105,500 options granted in the year ended December 31, 2023 under the Company’s retention program, which were granted to the continuing employees that were not subject to the Company’s strategic restructuring plan. During the second quarter of 2023, 83,700 options were granted to non-executive directors, which will vest ratably on a monthly basis over the next 12 months after the grant date, provided that in each case that the recipient remains as a non-executive director through vesting date. The expected term for the options granted to certain non-executive directors was 5.5 years and the risk-free interest rate was approximately 3.9%. The remaining 1,396,840 options granted in the year ended December 31, 2023, of which 690,240 options were granted in connection with the start of the Company’s new President and Chief Executive Officer and transition of the Company’s interim Chief Executive Officer to Chief Business Officer, have a vesting schedule in which 25% vest on the first anniversary of the grant date and the remainder vest ratably on a monthly basis over the next 36 months, provided in each case that the recipient remains an employee of the Company through each vesting date. The expected term for these options granted in the year ended December 31, 2023 was 5.50 to 6.25 years, the volatility ranged 82.4% to 86.7%, and the risk-free interest rate ranged approximately 3.5% to 4.7%. The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company’s public trading commenced in September 2018, and, as a result, there is only limited available historical volatility experience. Therefore, the Company estimates expected share price volatility based on a combination of the historical volatility of a group of publicly traded peer companies and the historical volatility of the Y-mAbs share price, and the Company expects to continue to do so until such time as the Company has adequate historical data regarding the volatility of the Company’s own traded share price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards as the Company has limited historical data to support the expected term assumption. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The expected dividend yield is based on the fact that the Company has never paid cash dividends on shares of common stock and the Company does not expect to pay any cash dividends in the foreseeable future. There were no significant changes to the inputs included in the Black-Scholes option pricing model during the year ended December 31, 2023. ​ As of December 31, 2023, the Company had $15,937,000 of unrecognized compensation expense related to employee stock options that are expected to vest over a period of 2.75 years. ​ Restricted Stock Units For the years ended December 31, 2023 and 2022, stock-based compensation for restricted stock unit grants was $696,000 and $328,000, respectively. For the year ended December 31, 2023, the expenses were recorded as $410,000 in research and development expense and $286,000 in selling, general, and administrative expense. For the year ended December 31, 2022, the expenses were recorded as $289,000 in research and development expense and $39,000 in selling, general, and administrative expense. The following table summarizes restricted stock units issued and outstanding: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted ​ average ​ ​ ​ ​ average ​ remaining ​ ​ ​ ​ grant ​ vesting ​ ​ Restricted Stock Units ​ price ​ life (years) Outstanding and expected to vest at December 31, 2022 ​ 33,355 ​ $ 17.77 1.77 Granted ​ 389,898 ​ ​ 4.84 Vested ​ (10,766) ​ ​ 18.90 ​ Forfeited ​ (61,080) ​ ​ 8.12 ​ ​ Outstanding and expected to vest at December 31, 2023 ​ 351,407 ​ $ 5.06 1.99 ​ The table above includes 362,400 restricted stock units granted in the year ended December 31, 2023, under the Company’s retention program, which were granted to the continuing employees that were not subject to the Company’s strategic restructuring plan. As of December 31, 2023, the Company had $1,338,000 of unrecognized compensation related to employee restricted stock units that are expected to vest over a period of 1.99 years.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
INCOME TAXES	NOTE 12—INCOME TAXES Domestic and foreign loss before income taxes are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ ​ 2023 ​ 2022 United States ​ $ (17,232) ​ $ (87,827) Foreign ​ (3,634) ​ (7,741) Total ​ $ (20,866) ​ $ (95,568) ​ The Company's current income tax provision was $561,000 during the year ended December 31, 2023, and the Company did not have a current income tax provision during the year ended December 31, 2022. Current and deferred income taxes (tax benefits) are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ 2023 ​ 2022 Current income tax ​ ​ ​ ​ ​ ​ Federal ​ $ 200 ​ $ — State ​ ​ 361 ​ ​ — Foreign ​ ​ — ​ ​ 18 Total current income taxes (tax benefits) ​ ​ 561 ​ ​ 18 Deferred income tax ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ — State ​ ​ — ​ ​ — Foreign ​ ​ — ​ ​ (18) Total deferred income taxes (tax benefits) ​ ​ — ​ ​ (18) Total income taxes (tax benefits) ​ $ 561 ​ $ — ​ The difference between income taxes expected at the U.S. federal statutory income tax rate of 21% for tax years ended December 31, 2023 and 2022, respectively, and income taxes provided are set forth below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ ​ 2023 ​ 2022 Taxes on income at U.S. federal statutory rate ​ $ (4,382) ​ $ (20,069) State and local taxes, net of federal tax effects ​ (411) ​ (5,661) Effect of rate change ​ (2,127) ​ 861 Foreign tax rate differential ​ (110) ​ (95) Valuation allowance ​ 6,407 ​ 25,116 Tax credits ​ (135) ​ (1,749) Uncertain tax position ​ ​ — ​ ​ 18 Deferred adjustments ​ ​ 439 ​ ​ 969 Shared based compensation ​ ​ 1,011 ​ ​ 1,265 Other ​ (131) ​ (655) Total ​ $ 561 ​ $ — ​ Significant components of the Company’s net deferred tax assets/(liabilities) are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Deferred tax assets/(liabilities): ​ ​ Acquired intangibles ​ $ 3,702 ​ $ 2,657 Unrealized foreign exchange loss ​ (87) ​ 263 Accrued royalty ​ 671 ​ 914 Stock based compensation ​ 11,603 ​ 13,353 Net operating loss carryforwards ​ 83,237 ​ 86,072 Tax credit carryforwards ​ 16,336 ​ 16,799 Right of use asset ​ ​ (507) ​ ​ (413) Lease liability ​ ​ 515 ​ ​ 435 Capitalized research and experimentation ​ ​ 33,088 ​ ​ 21,902 Other ​ 402 ​ 572 Total deferred tax assets/(liabilities) ​ 148,960 ​ 142,554 Valuation allowance ​ (148,960) ​ (142,554) Net deferred tax assets/(liabilities) ​ $ — ​ $ — ​ The Company maintains a full valuation allowance on U.S. and foreign deferred tax assets. The assessment regarding whether a valuation allowance is required considers both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable. In making this assessment, significant weight is given to evidence that can be objectively verified. In the Company’s evaluation, the Company considered cumulative losses historically and in recent years and its forecasted losses in the near term as significant negative evidence. Based upon review of available positive and negative evidence, the Company determined that the negative evidence outweighed the positive evidence and a full valuation allowance on the Company’s U.S. and foreign deferred tax assets will be maintained. The Company will continue to assess the realizability of the Company’s deferred tax assets and will adjust the valuation allowance as needed. As of December 31, 2023, the Company had U.S. federal and various state net operating loss (“NOL”) carryforwards of approximately $245,242,000 and $189,831,000, respectively. The Company also had U.S. federal tax credit carryforwards of $16,336,000 as of December 31, 2023. The federal NOL of approximately $245,242,000 can be carried forward indefinitely but is limited to offset 80% of taxable income. The state and local jurisdiction NOLs and tax credit carryforwards will begin to expire in 2030. The NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986 (“IRC”). The Company has performed an analysis of the Company’s Section 382 ownership changes through December 31, 2022. Due to the large annual limitation, the Company believes that it is more likely than not that none of the net operating loss carryforwards will expire as a result of the limitation from the ownership change under Section 382. The Company also has Danish NOL carryforwards of $21,628,000 which have an indefinite carryforward period. The Company recognizes income tax benefits for tax positions determined more likely than not to be sustained upon examination, based on the technical merits of the positions. Changes in the Company’s unrecognized tax benefits, excluding the related accrual of interest and penalties, from January 1 through December 31 are set forth below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2023 2022 Beginning balance ​ $ — ​ $ 304 Additions for prior year tax positions ​ ​ — ​ ​ 18 Settlements ​ ​ — ​ ​ (322) Ending balance ​ $ — ​ $ — ​ The Company’s tax returns for the years 2017 to 2022 are all open for tax examination by U.S. federal and state, and the Danish tax authorities. During 2022, the review of the Company’s transfer pricing policies by the Danish Tax Authorities for tax years 2016 through 2020 was completed resulting in the release of the corresponding reserve. The release did not have a material impact on the Company’s income tax accounts. ​ The Company classifies interest and penalty expense related to income tax expense as components of the tax provision for income taxes. As of December 31, 2023, the Company does not have any interest or penalties accrued related to the total amount of unrecognized tax benefits.

OTHER BENEFITS

OTHER BENEFITS	12 Months Ended
	Dec. 31, 2023
OTHER BENEFITS
OTHER BENEFITS	NOTE 13—OTHER BENEFITS The Company has adopted a defined contribution 401(k) savings plan (the “401(k) plan”) covering all U.S. employees. Participants may elect to defer a percentage of their pretax or after-tax compensation to the 401(k) plan, subject to defined limitations. The plan allows for a discretionary match by the Company. The Company made no matching contributions to the plan for the years ended December 31, 2023 and 2022. ​ The Company has established a retirement program for employees of the Danish subsidiary pursuant to which all such employees can contribute an amount at their election from their base compensation and may receive contributions from our Danish subsidiary. The Danish subsidiary made no contributions during the years ended December 31, 2023 and 2022. In addition, health insurance benefits for our Danish employees are fully paid for by such employees. The Company’s Danish subsidiary does not incur any costs for these health insurance benefits.

RESTRUCTURING CHARGE

RESTRUCTURING CHARGE	12 Months Ended
	Dec. 31, 2023
RESTRUCTURING CHARGE
RESTRUCTURING CHARGE	NOTE 14 — RESTRUCTURING CHARGE On January 4, 2023, following Board approval, the Company announced a strategic restructuring plan designed to extend cash resources and prioritize resources for the commercialization and potential label extension of DANYELZA and the development of the SADA PRIT technology platform. The Company completed the restructuring in May 2023, which resulted in an approximately 35% reduction to the Company’s workforce. Affected employees were offered separation benefits, including severance and outplacement services along with temporary healthcare coverage assistance. As a result, during the year ended December 31, 2023, the Company recognized restructuring expenses of $4,482,000, based on the currency rate for the period. For the year ended December 31, 2023, the Company recorded $3,346,000 and $1,136,000, respectively, within research and development and selling, general, and administrative, on the Consolidated Statements of Net Loss and Comprehensive Loss. The restructuring expenses primarily related to severance benefits of $2,776,000, which were paid as of December 31, 2023, and acceleration of stock-based compensation of $1,706,000 which was recognized in the year ended December 31, 2023 as there is no longer a service condition related to such awards. ​ ​

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, net product revenues, the accrual for research and development expenses, the accrual of milestone and royalty payments, the valuation of stock options and asset impairments. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid instruments with original maturities of three months or less from date of purchase to be cash equivalents. All cash and cash equivalents are held in highly rated securities including a treasury money market fund, which is unrestricted as to withdrawal or use. To date, the Company has not experienced a loss on the cash and cash equivalents. The carrying amount of cash and cash equivalents approximates its fair value due to its short-term and liquid nature. The Company’s cash and cash equivalents are held at a large major federal, national bank. The Company maintains cash balances in excess of insured limits. The Company monitors the financial performance, credit ratings and liquidity of the money market fund to timely assess and respond to any changes in the asset values of the fund. The Company does not anticipate any loss with respect to such cash balances.
Accounts Receivable, Net	Accounts Receivable, Net The Company’s accounts receivable, net balance consists of amounts due from sales of our approved product, DANYELZA. Receivables from product sales are recorded net of allowances which generally include chargebacks, doubtful accounts, rebates, returns, and discounts. The allowance is based primarily on assessment of specific identifiable customer accounts considered at risk or uncollectible, as well as an analysis of current receivables aging and expected future write-offs. The Company has not historically experienced any significant credit losses. All customer accounts are actively managed, and no losses are currently expected. The Company has not experienced any write-offs related to customer accounts receivables and has not recognized any allowance for doubtful accounts nor reversed any allowances during the years ended December 31, 2023 and 2022.
Concentration of Credit Risk	Concentration of Credit Risk The Company’s product sales are made through arrangements primarily with three national U.S. specialty distributors. As of December 31, 2023, the accounts receivable balances from such distributors totaled 66% of the Company’s outstanding accounts receivable. See Note 4 – Product Revenues, Net receivable as of December 31, 2023 represented balances from international distribution partners. The Company has contractual payment terms with each customer and monitors their financial performance, historical payment terms and credit worthiness to timely assess and respond to any changes in their credit profile.
Inventories	Inventories The Company values the inventories at the lower of cost or net realizable value on a first-in, first-out basis. The Company’s inventory cost includes amounts related to materials, third-party contract manufacturing, third-party packaging services, freight, labor costs for personnel involved in the manufacturing process, and indirect overhead costs. Raw and intermediate materials that may be utilized for both commercial and clinical programs are identical and given the alternative future use such amounts are initially classified as inventory. Amounts in inventory associated with clinical development programs are charged to research and development expense when the product enters the research and development process and can no longer be used for commercial purposes and, therefore, does not have an alternative future use. The Company capitalizes inventory costs related to products to be sold in the ordinary course of business. The Company makes a determination of capitalizing inventory costs for a product based on, among other factors, status of regulatory approval, information regarding safety, efficacy and expectations relating to commercial sales and recoverability of costs. For DANYELZA, the Company commenced capitalization of inventory at the receipt of FDA approval. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment occurs. Such impairment charges, should they occur, are recorded within cost of goods sold. The determination of whether inventory costs will be realizable requires estimates by management. The Company had inventory write-offs totaling $831,000 and $1,200,000 in the years ended December 31, 2023 and 2022, respectively, which were each recorded in cost of goods sold on the Consolidated Statements of Net Loss and Comprehensive Loss.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. ​ ● Level 1 — Unadjusted quoted prices for identical assets or liabilities in active markets; ● Level 2 — Inputs other than quoted prices in active markets for identical assets and liabilities that are observable either directly or indirectly for substantially the full term of the asset or liability; and ● Level 3 — Unobservable inputs for the asset or liability, which include management's own assumption about the assumptions market participants would use in pricing the asset or liability, including assumptions about risk. Cash equivalents held in money market funds are valued using other significant observable inputs, which represent a Level 2 measurement within the fair value hierarchy. The Company has no other cash equivalents. The following tables present the Company’s fair value hierarchy for cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2023 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 Total ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965 Total ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965 ​ During the years ended December 31, 2023 and 2022, there were no transfers between Level 1, Level 2 and Level 3.
Operating Lease Right-of-Use Assets and Operating Lease Liabilities	Operating Lease Right-of-Use Assets and Operating Lease Liabilities The Company determines if an arrangement includes a lease at inception. Operating lease right-of-use assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses an estimated incremental borrowing rate based on information available at the lease commencement date. Because most of the Compnay’s leases do not provide an implicit rate of return, an incremental borrowing rate is used based on the information available at the commencement date in determining the present value of lease payments on an individual lease basis. The Company’s incremental borrowing rate for a lease is the estimated rate of interest the Company would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. The Company’s leases may include options to extend or terminate a lease which are included in the lease term when it is reasonably certain that the Company will exercise any such options. None of the Company’s leases contain any residual value guarantees. Lease expense is recognized on a straight-line basis over the expected lease term. Related variable lease costs incurred are not material to the Company. The Company currently elects the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize right-of-use assets or liabilities. The Company also elects the practical expedient to not separate lease and non-lease components for all of our leases. The Company has made an accounting policy election to account for each separate lease component of a contract and its associated non-lease components as a single lease component. See the Lease Agreements section in NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS
Revenue Recognition	Revenue Recognition To determine revenue recognition for product revenue and license revenue arrangements that the Company determines are within the scope of ASC 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 (or as) the Company satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract with a customer under ASC 606, including when it is probable that the Company will collect the consideration the Company is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Under the practical expedient permitted under Topic 606, the Company expenses incremental costs of obtaining a contract as and when incurred if the expected amortization period of the assets is one year or less. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company combines that good or service with other promised goods or services until the Company identifies a bundle of goods or services that is distinct. The standalone selling price is generally determined based on the prices charged to customers. Product revenue, net The Company recognizes revenue from sales of DANYELZA at a point in time when customer is deemed to have obtained control of the product, which generally occurs upon receipt at the end-user hospital for sales in the United States, and upon delivery to the distributors for sales in the international territories. The amount of revenue the Company recognizes from sales of DANYELZA varies due to rebates, chargebacks and discounts provided under governmental and other programs, distribution-related fees and other sales-related deductions. In order to determine those deductions, the Company estimates, utilizing the expected value method, the amount of revenue that the Company will ultimately be entitled to. This estimate is based upon contracts with customers and government agencies, statutorily-defined discounts applicable to government-funded programs, estimated payor mix, and other relevant factors. Calculating these amounts involves estimates and judgments, and the Company reviews these estimates quarterly. If actual results vary from the Company’s original estimates, the Company will adjust these estimates quarterly, which would affect net product revenue and earnings in the period such variances occur. ● Rebates and chargebacks The Company contracts with United States governmental agencies to ensure that DANYELZA will be eligible for coverage under the various programs administered by the agencies. The Company estimates the rebates and chargebacks to be provided and deducts these estimated amounts from gross product revenues. These reserves are recorded in the same period the revenue is recognized, resulting in a reduction of product revenue and the establishment of accrued liabilities for the rebates and a reduction of accounts receivable for the chargebacks. The Company develops estimates for rebates and chargebacks based upon (i) the Company’s contracts with these agencies, (ii) the government-mandated discounts applicable to government-funded programs, and (iii) information obtained from hospitals and third-party consultants regarding the payor mix. The Company’s liability for these rebates and chargebacks mainly consists of claims for which invoices have not yet been received and paid. The Company does not maintain material levels of inventory in the wholesale or retail channel. ● Discounts and distribution-related fees The Company provides invoice discounts on DANYELZA sales to distributors for prompt payment and fees for distribution services and invoice discounts reduce the original accounts receivable balances. The payment terms for sales to distributors generally include a 2% discount for prompt payment or fees for distribution services which are based on contractual rates agreed with the respective distributors. Based on historical data and experiences with the distributors, the Company expects the distributors to earn these discounts and fees and deduct the full amount of these discounts and fees from the Company’s gross product revenue at the time such revenues are recognized. ● Returns The Company offers customers limited product return rights for damaged, defective, or expiring products. The Company estimates returns on sales of DANYELZA mainly based on information provided to the Company from the hospitals and distributors. The return reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. In December 2022, the Company announced a distribution agreement with WEP Clinical Ltd., or WEP, in connection with an early access program for DANYELZA in Europe. There are no regulatory-based or sales-based milestone payments or royalty arrangements under this distribution agreement. The Company recognizes revenue when WEP obtains control of the product upon delivery. The Company invoices WEP based on the terms of the distribution agreement, where a portion is billed upon shipment of product and the unbilled portion is billed at a later date based on terms of the distribution agreement. The Company has an unconditional right to the unbilled portion of the receivable and the Company estimates that the receivable will be collected within one year and therefore has recorded the balance at December 31, 2023, within accounts receivable on the Consolidated Balance Sheets. License revenue The Company’s license agreements include regulatory-based milestone payments and sales-based milestone payments, in addition to royalties. The Company determines whether the achievement of each regulatory-based milestone is constrained as they are contingent upon regulatory approvals, which are not within the control of the Company and therefore not deemed probable. The Company expects that the sales-based milestones and royalty payments will be recognized when the milestone is achieved or the related sales occur. The Company re-evaluates the transaction price each quarter and as uncertain events are resolved or other changes in circumstances occur, the Company assesses whether this resolves the constraint and it is appropriate to recognize revenue. In December 2020, the Company entered into a development and commercialization arrangement with SciClone International Pharmaceuticals Ltd., or SciClone, for certain indications of DANYELZA and omburtamab for Greater China, including Mainland China, Taiwan, Hong Kong and Macau. Based on the terms of the agreement, the Company may receive regulatory-based milestone payments up to $40,000,000, of which $15,000,000 has already been recognized and received in December 2022 for the conditional approval of DANYELZA in China, and sales-based milestone payments up to $60,000,000 and is entitled to royalties based upon the net sales generated by SciClone related to the product indications in the territory. The Company expects that the remaining regulatory-based and sales-based milestones will be recognized when each milestone is achieved. In November 2020, the Company entered into an exclusive license and distribution agreement for DANYELZA and omburtamab with Takeda Israel, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited covering the State of Israel, West Bank and Gaza Strip. Based on the terms of the arrangement, the Company may receive regulatory-based milestone payments up to $750,000, of which $250,000 has already been recognized, and sales-based milestone payments up to $500,000 and is entitled to royalties based upon the net sales generated by Takeda related to the product in the territory. The Company expects that the remaining regulatory-based and sales-based milestones will be recognized when the milestone is achieved, or the related sales occur. In December 2020, the Company entered into a distribution agreement for DANYELZA and omburtamab with Swixx BioPharma AG for the Eastern European territories Bosnia & Herzegovina, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Russia, Serbia, Slovakia and Slovenia. There are no regulatory-based or sales-based milestone payments or royalty arrangements under this distribution agreement. In May 2021, the Company entered into an exclusive distribution agreement with Adium Pharma S.A. (“Adium”) for Adium to be the exclusive distributor in Latin America of the Company’s antibodies omburtamab, if approved, and DANYELZA. Under the terms of the agreement, the Company may receive regulatory-based milestone payments up to $3,000,000, of which $1,000,000 was received in April 2022 upon the submission of the updated FDA BLA dossier for DANYELZA. In addition, the Company is entitled to royalties based upon DANYELZA net sales generated by Adium in Latin America. The agreement with Adium does not contain a regulatory-based milestone related to the Brazilian Health Regulatory Agency’s approval for marketing authorization, which was granted during the three months ended June 30, 2023. During the year ended December 31, 2023, the Company recognized $500,000 in regulatory-based license revenue from Adium pursuant to the distribution agreement in connection with the September 2023 achievement of marketing authorization for DANYELZA in Mexico. In January 2024, the Company accepted the price approval for the first product in Brazil from the Brazilian Medicines Market Regulation Chamber, or CMED. The Company received $0.5 million regulatory-based payment from Adium in connection with the price approval from CMED in the first quarter of 2024. The Company expects that the sales-based milestones and royalty payments will be recognized when and if the milestones are achieved or the related sales occur. In December 2022, the Company announced a distribution agreement with WEP Clinical Ltd., or WEP, in connection with an early access program for DANYELZA in Europe. There are no regulatory, or sales-based milestone payments or royalties under this distribution agreement.
Segment Information	Segment Information The Company is engaged solely in operations related to the discovery, development, distribution and commercialization of novel antibody-based therapeutic products for the treatment of cancer, which the Company defines as one operating segment.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: ​ ​ ​ ​ ​ Estimated Useful Life Furniture and fixtures 5 years Machinery and equipment ​ 5 years Leasehold improvements Shorter of life of lease or 15 years ​ Depreciation expense on property and equipment was $386,000 and $662,000 for the years ended December 31, 2023 and 2022. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are expensed as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets ASC 360, Property, Plant and Equipment, addresses the financial accounting and reporting for impairment or disposal of long-lived assets. The Company reviews the recorded values of long-lived assets for impairment whenever events or changes in business circumstance indicate that the carrying amount of an asset or group of assets may not be fully recoverable. During the year ended December 31, 2022, the Company recorded an impairment charge of $617,000 to write-off the net book value of fixed assets that were related to the production of omburtamab, which did not receive FDA regulatory approval, as the equipment has no alternative use. The impairment charge was recorded within research and development expense within the Company’s Consolidated Statements of Net Loss and Comprehensive Loss and foreign currency and other transactions within the Company’s Consolidated Statements of Cash Flows. The Company did not have impairment of long-lived assets for the year ended December 31, 2023.
Provision for Income Taxes	Provision for Income Taxes The Company accounts for income taxes under the asset and liability approach for the financial accounting and reporting of income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to net operating loss carry forwards and temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. These assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which the temporary differences are expected to reverse. The Company maintains a full valuation allowance on deferred tax assets based on cumulative historical and expected losses. If the Company achieves profitability, the Company will consider the continued need for such a full valuation allowance. Tax returns are prepared and filed based on the Company’s interpretation of tax laws and regulations. In the normal course of business, the Company’s tax returns are subject to examination by various taxing authorities. Such examinations may result in future tax and interest assessments by these taxing authorities. In determining the Company’s provision for income taxes for financial reporting purposes, the Company establishes a reserve for uncertain tax positions unless such positions are determined to be more likely than not of being sustained upon examination based on their technical merits. The Company considers many factors when evaluating and estimating tax positions and tax benefits, which may require periodic adjustments and which may not accurately anticipate actual outcomes. Accordingly, the Company will report a liability for unrecognized tax benefits resulting from any uncertain tax positions taken or expected to be taken on a tax return. The Company’s policy is to recognize, when applicable, interest and penalties on uncertain tax positions as part of income tax expense. In accordance with guidance issued by Financial Accounting Standards Board (“FASB”), companies should make and disclose a policy election as to whether they will recognize deferred taxes for basis differences expected to reverse as Global Intangible Low-Taxed Income (“GILTI”) or whether they will account for GILTI as period costs if and when incurred. The Company has elected to recognize the resulting tax with respect to the GILTI provision as a period cost. No costs were incurred by the Company through December 31, 2023 as a result of GILTI.
Research and Development	Research and Development Research and development costs are charged to operations when incurred and are included in operating expenses. Research and development costs consist principally of compensation cost for the Company’s employees and consultants that perform research activities, the fees paid to maintain licenses, the payments to third-party CMOs and CROs for manufacturing and services performed for products in development, and consumables and other materials used in research and development. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of accrued liabilities, we analyze progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Actual results could differ from our estimates. Additionally, the Company is obligated to make certain royalty and clinical, regulatory and sales-based milestone payments in accordance with the contractual terms of the MSK License, CD33 License, MabVax Sublicense, and SADA License based upon the resolution of certain contingencies. The Company records the clinical and regulatory milestone payments when the achievement of the milestones or payment of the milestones is deemed probable, and the amount of the payment is reasonably estimable. As it relates to clinical and regulatory milestone payments under the licensing arrangements, those may become due and payable with the passage of time whether or not the milestones have actually been met. When evaluating whether milestones should be recognized under the licensing arrangements, the Company relies on the collective clinical experience within the organization to determine the likelihood of achievement, as well as the current stage of the compounds under development, estimates of the progress of the Company’s preclinical studies and clinical trials, completion of milestone events per underlying agreements, the time expected to complete certain development activities, each party’s termination right under the license agreements, invoices received and contracted costs when evaluating whether the clinical milestones should be recognized in each reporting period. The Company reviews estimates each period and determines whether to make revisions to such estimates as necessary.
Selling, General and Administrative	Selling, General and Administrative The Company expenses selling, general, and administrative costs as incurred. Selling, general and administrative costs consist primarily of salaries, bonus, benefits, and stock-based compensation expenses for personnel in executive, commercial, finance and administrative functions. Other significant costs include costs of commercialization of DAYNELZA, costs of legal matters and insurance. Other significant costs for 2022 also included commercial cost related to the potential launch of omburtamab in 2022. Advertising and promotion costs are included in selling, general, and administrative expenses and were immaterial in the years ended December 31, 2023 and 2022. Advertising and product promotion costs are expensed as incurred.
Stock-Based Compensation	Stock-Based Compensation The Company measures stock options granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards, over the requisite service period, which for employees and directors is the vesting period of the respective award. Forfeitures are accounted for as they occur. The Company issues stock options with only service-based or immediate vesting conditions and records the expense for these awards using the straight-line method over the requisite service period. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company’s public trading commenced in September 2018, and, as a result, there is limited available historical volatility experience. Therefore, we estimate our expected share price volatility based on the weighting of our own volatility in the estimation with the historical volatility of a group of publicly traded peer companies, and we expect to continue to do so until such time as we have adequate historical data regarding the volatility of our own traded share price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards as the Company has limited historical data to support the expected term assumption. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The expected dividend yield is based on the fact that the Company has never paid cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future. The fair value of restricted stock units is determined at the grant-date price of the Company’s common stock.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with shareholders. The difference between net loss and comprehensive loss for the period presented in the accompanying consolidated financial statements was due to foreign currency translation.
Foreign Currency	Foreign Currency The consolidated financial statements of the Company’s international subsidiary with a functional currency other than the U.S. dollar is translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates during the period for operating results. Translation gains and losses are included in Accumulated Other Comprehensive Income/(Loss) in the Consolidated Statement of Net Loss and Comprehensive Loss. The Company recognized foreign currency translation losses of $882,000 and $40,000 for the years ended December 31, 2023 and 2022, respectively. Foreign currency transaction gains and losses are included in interest and other income/(loss), net, in the Consolidated Statements of Net Loss and Comprehensive Loss. The Company recorded a foreign currency transaction gain of $524,000 and a foreign currency transaction loss of $848,000 for the years ended December 31, 2023, and 2022, respectively.
Earnings Per Share	Earnings Per Share The Company reports net earnings per share in accordance with ASC 260, Earnings per Share. Basic net loss per share (“EPS”) is calculated by dividing net income or loss attributable to common stockholders by the weighted average common stock outstanding. Diluted EPS is calculated by adjusting weighted average common shares outstanding for the dilutive effect of common stock options and restricted stock units. In periods in which a net loss is recorded, no effect is given to potentially dilutive securities, since the effect would be antidilutive. Similarly, securities that could potentially dilute basic EPS in the future are not included in the computation of diluted EPS because to do so would have been antidilutive.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, and are adopted by the Company as of the specific effective date. The Company adopted ASU 2022-04, ASU 2022-02, ASU 2022-01 and ASU 2021-08 effective January 1, 2023, and the adoption of these new standards did not have a material impact on the Company’s consolidated financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09, Improvement to income tax disclosures (Topic 740). ASU 2023-09 addresses annual disclosures related to the income tax rate reconciliation and the income taxes paid within the tax note. ASU 2023-09 requires consistent categories and greater disaggregation of information in the income tax rate reconciliation as well as a disaggregation of taxes paid by jurisdiction for the income taxes paid. ASU 2023-09 is required to be adopted by the Company for annual periods beginning after December 15, 2024. Early adoption is permitted for annual consolidated financial statements that have not yet been issued or made available for issuance. The Company is evaluating the impact of this update on the Company’s disclosures. The Company has evaluated all other accounting pronouncements recently issued but not yet adopted and believes that these pronouncements will not have a material impact on the Company’s consolidated financial statements or disclosures. ​

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of cash equivalents measured at fair value on recurring basis	The following tables present the Company’s fair value hierarchy for cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2023 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 Total ​ $ — ​ $ 75,501 ​ $ — ​ $ 75,501 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965 Total ​ $ — ​ $ 86,965 ​ $ — ​ $ 86,965
Schedule of property and equipment	​ ​ ​ ​ ​ Estimated Useful Life Furniture and fixtures 5 years Machinery and equipment ​ 5 years Leasehold improvements Shorter of life of lease or 15 years

PRODUCT REVENUE, NET (Tables)

PRODUCT REVENUE, NET (Tables)	12 Months Ended
	Dec. 31, 2023
PRODUCT REVENUE, NET
Schedule of product revenue by geographic location	The Company’s product revenue, net was generated from sales of DANYELZA and consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ United States ​ $ 67,814 ​ $ 46,259 Other countries ​ ​ 16,505 ​ ​ 3,008 Total product revenue, net ​ $ 84,319 ​ $ 49,267
Schedule of change in reserves for discounts and allowances	An analysis of the change in reserves for discounts and allowances is summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ ​ ​ ​ Discounts ​ Government Rebates Returns ​ Total ​ ​ Balance December 31, 2022 $ 33 ​ $ 2,905 ​ $ 44 ​ $ 2,982 Current provisions relating to sales in current year ​ 238 ​ ​ 8,361 ​ ​ 519 ​ ​ 9,118 Payments/credits relating to sales in current year ​ (230) ​ ​ (7,482) ​ ​ (497) ​ ​ (8,209) Change in estimate related to sales in the prior year ​ — ​ ​ (1,090) ​ ​ — ​ ​ (1,090) Balance December 31, 2023 $ 41 ​ $ 2,694 ​ $ 66 ​ $ 2,801

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2023
NET LOSS PER SHARE
Schedule of basic and diluted net loss per share	The calculations of basic and diluted net loss per share are as follows (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss (numerator) ​ $ (21,427) ​ $ (95,568) ​ Weighted-average shares (denominator), basic and diluted ​ 43,645 ​ 43,704 ​ Basic and diluted net loss per share ​ $ (0.49) ​ $ (2.19) ​

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
	Dec. 31, 2023
INVENTORIES
Schedule of inventories	Inventories consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 Work In Progress ​ $ 14,021 ​ $ 11,317 Finished Goods ​ ​ 2,992 ​ ​ 666 Total Inventories ​ $ 17,013 ​ $ 11,983 ​ ​ ​ ​ ​ ​ ​ ​ Inventories are classified on the Consolidated Balance Sheets in each respective period (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 CURRENT ASSETS ​ ​ ​ ​ ​ ​ Inventories ​ $ 5,065 ​ $ 6,702 Total recorded in Current Assets ​ ​ 5,065 ​ ​ 6,702 ​ ​ ​ ​ ​ ​ ​ NONCURRENT ASSETS ​ ​ ​ ​ ​ ​ Other assets ​ ​ 11,948 ​ ​ 5,281 Total recorded in Noncurrent Assets ​ ​ 11,948 ​ ​ 5,281 Total Inventories ​ $ 17,013 ​ $ 11,983

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	12 Months Ended
	Dec. 31, 2023
ACCRUED LIABILITIES
Schedule of accrued liabilities	Accrued liabilities as of December 31, 2023 and December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2023 ​ 2022 ​ ​ ​ ​ ​ ​ ​ Accrued licensing, milestone and royalty payments ​ $ 3,452 ​ $ 4,002 Accrued clinical costs ​ 597 ​ 932 Accrued compensation and board fees ​ 3,858 ​ 2,445 Accrued manufacturing costs ​ ​ 2,531 ​ ​ 2,977 Accrued sales reserves ​ ​ 2,309 ​ ​ 2,474 Other ​ 419 ​ 411 Total ​ $ 13,166 ​ $ 13,241 ​

LICENSE AGREEMENTS AND COMMIT_2

LICENSE AGREEMENTS AND COMMITMENTS (Tables)	12 Months Ended
	Dec. 31, 2023
LICENSE AGREEMENTS AND COMMITMENTS
Schedules of maximum clinical, regulatory or sales-based milestones and obligations pertaining to the significant license agreements that have been paid, expensed or accrued	The below table represents the maximum clinical, regulatory or sales-based milestones as reflected within the significant license agreements, certain of which have been paid in prior periods or are accrued as presented in the table below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maximum Maximum Maximum ​ ​ Clinical ​ Regulatory ​ Sales-based Agreements ​ Milestones ​ Milestones ​ Milestones MSK ​ ​ $ 2,450 ​ ​ $ 9,000 ​ ​ $ 20,000 CD33 ​ ​ 550 ​ ​ 500 ​ ​ 7,500 MabVax ​ ​ 200 ​ ​ 1,200 ​ ​ — SADA ​ ​ 4,730 ​ ​ 18,125 ​ ​ 23,750 The below table represents all obligations pertaining to the significant license agreements that have been paid, expensed or accrued as of and for the years ended December 31, 2023 and 2022 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid Cash paid Expense Expense ​ Accrued Accrued Accrued Accrued ​ ​ Twelve ​ Twelve ​ Twelve ​ Twelve ​ liabilities liabilities liabilities liabilities ​ ​ months ​ months ​ months ​ months ​ Current ​ Non-current ​ Current ​ Non-current ​ ​ ​ ended ​ ended ​ ended ​ ended ​ as of ​ as of ​ as of ​ as of ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ December 31, ​ Agreements ​ 2023 ​ 2022 ​ 2023 ​ 2022 ​ 2023 ​ 2023 ​ 2022 ​ 2022 ​ MSK ​ $ 6,027 ​ $ 2,871 ​ $ 5,158 ​ $ 3,582 ​ $ 2,452 ​ $ 1,950 ​ $ 3,397 ​ $ 1,950 ​ CD33 ​ ​ — ​ ​ 150 ​ ​ — ​ ​ — ​ ​ — ​ ​ 300 ​ ​ — ​ ​ 300 ​ MabVax ​ ​ 10 ​ ​ 10 ​ ​ 10 ​ ​ 10 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ SADA ​ ​ 605 ​ ​ 1,000 ​ ​ 4,125 ​ ​ — ​ ​ 1,000 ​ ​ 3,125 ​ ​ 605 ​ ​ — ​
Maturities of operating lease liabilities	Maturities of operating lease liabilities as of December 31, 2023 and 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Operating Leases ​ as of December 31, 2023 ​ as of December 31, 2022 Years ending December 31, ​ ​ ​ ​ ​ ​ 2023 ​ $ — ​ $ 997 2024 ​ ​ 996 ​ ​ 490 2025 ​ ​ 526 ​ ​ 419 Total lease payments ​ ​ 1,522 ​ ​ 1,906 Less: Imputed interest ​ ​ (103) ​ ​ (139) Total operating lease liabilities as of period end ​ $ 1,419 ​ $ 1,767

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2023
STOCK-BASED COMPENSATION
Schedule of assumptions that Company used to determine the fair value of the stock options granted	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended Year Ended ​ ​ ​ December 31, 2023 ​ December 31, 2022 ​ ​ ​ ​ ​ ​ ​ Risk-free interest rate ​ 3.92 % 3.12 % Expected term (in years) ​ 6.2 5.9 Expected volatility ​ 82.9 % 73.6 % Expected dividend yield ​ — % — %
Schedule of common stock options issued and outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted ​ Aggregate ​ average ​ ​ ​ ​ average ​ intrinsic ​ remaining ​ ​ ​ ​ exercise ​ value ​ contractual ​ ​ Options ​ price ​ (in thousands) ​ life (years) Outstanding and expected to vest at December 31, 2022 7,079,767 ​ $ 21.27 ​ $ 3,112 ​ 6.45 Granted 2,586,040 ​ ​ 5.25 ​ ​ ​ ​ ​ Exercised ​ (50,000) ​ ​ 2.00 ​ ​ ​ ​ ​ Forfeited ​ (308,477) ​ ​ 11.10 ​ ​ ​ ​ ​ Outstanding and expected to vest at December 31, 2023 9,307,330 ​ $ 17.26 ​ $ 10,012 ​ 6.44 Exercisable at December 31, 2023 5,958,167 ​ ​ 21.00 ​ ​ 6,195 ​ 5.03
Schedule of restricted stock units issued and outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted ​ average ​ ​ ​ ​ average ​ remaining ​ ​ ​ ​ grant ​ vesting ​ ​ Restricted Stock Units ​ price ​ life (years) Outstanding and expected to vest at December 31, 2022 ​ 33,355 ​ $ 17.77 1.77 Granted ​ 389,898 ​ ​ 4.84 Vested ​ (10,766) ​ ​ 18.90 ​ Forfeited ​ (61,080) ​ ​ 8.12 ​ ​ Outstanding and expected to vest at December 31, 2023 ​ 351,407 ​ $ 5.06 1.99

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
Schedule of domestic and foreign loss before income taxes	Domestic and foreign loss before income taxes are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ ​ 2023 ​ 2022 United States ​ $ (17,232) ​ $ (87,827) Foreign ​ (3,634) ​ (7,741) Total ​ $ (20,866) ​ $ (95,568)
Schedule of components of provision for (benefit from) income taxes	Current and deferred income taxes (tax benefits) are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ 2023 ​ 2022 Current income tax ​ ​ ​ ​ ​ ​ Federal ​ $ 200 ​ $ — State ​ ​ 361 ​ ​ — Foreign ​ ​ — ​ ​ 18 Total current income taxes (tax benefits) ​ ​ 561 ​ ​ 18 Deferred income tax ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ — State ​ ​ — ​ ​ — Foreign ​ ​ — ​ ​ (18) Total deferred income taxes (tax benefits) ​ ​ — ​ ​ (18) Total income taxes (tax benefits) ​ $ 561 ​ $ —
Schedule of difference between incomes taxes expected at U.S. federal statutory income tax rate and income taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For The Year Ended December 31, ​ 2023 ​ 2022 Current income tax ​ ​ ​ ​ ​ ​ Federal ​ $ 200 ​ $ — State ​ ​ 361 ​ ​ — Foreign ​ ​ — ​ ​ 18 Total current income taxes (tax benefits) ​ ​ 561 ​ ​ 18 Deferred income tax ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ — State ​ ​ — ​ ​ — Foreign ​ ​ — ​ ​ (18) Total deferred income taxes (tax benefits) ​ ​ — ​ ​ (18) Total income taxes (tax benefits) ​ $ 561 ​ $ —
Schedule of significant components of net deferred tax assets/(liabilities)	Significant components of the Company’s net deferred tax assets/(liabilities) are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Deferred tax assets/(liabilities): ​ ​ Acquired intangibles ​ $ 3,702 ​ $ 2,657 Unrealized foreign exchange loss ​ (87) ​ 263 Accrued royalty ​ 671 ​ 914 Stock based compensation ​ 11,603 ​ 13,353 Net operating loss carryforwards ​ 83,237 ​ 86,072 Tax credit carryforwards ​ 16,336 ​ 16,799 Right of use asset ​ ​ (507) ​ ​ (413) Lease liability ​ ​ 515 ​ ​ 435 Capitalized research and experimentation ​ ​ 33,088 ​ ​ 21,902 Other ​ 402 ​ 572 Total deferred tax assets/(liabilities) ​ 148,960 ​ 142,554 Valuation allowance ​ (148,960) ​ (142,554) Net deferred tax assets/(liabilities) ​ $ — ​ $ —
Schedule of uncertain tax positions	Changes in the Company’s unrecognized tax benefits, excluding the related accrual of interest and penalties, from January 1 through December 31 are set forth below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2023 2022 Beginning balance ​ $ — ​ $ 304 Additions for prior year tax positions ​ ​ — ​ ​ 18 Settlements ​ ​ — ​ ​ (322) Ending balance ​ $ — ​ $ —

BASIS OF PRESENTATION - Accumul

BASIS OF PRESENTATION - Accumulated deficit (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
BASIS OF PRESENTATION
Accumulated deficit	$ (457,470)	$ (436,043)

BASIS OF PRESENTATION - Cash an

BASIS OF PRESENTATION - Cash and cash equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
BASIS OF PRESENTATION
Cash and cash equivalents	$ 78,637	$ 105,762

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details) - Credit Concentration Risk - Accounts Receivable - Three Customers	12 Months Ended
	Dec. 31, 2023 customer
Concentration risk
Number of customers	3
Concentration risk percentage (as a percent)	66%

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Inventory write-offs	$ 831	$ 1,200

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair value measurements
Level 1 to Level 2 Transfers	$ 0	$ 0
Level 2 to Level 1 Transfers	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Recurring
Fair value measurements
Cash equivalents	75,501	86,965
Recurring | Money market funds
Fair value measurements
Cash equivalents	75,501	86,965
Recurring | Level 2
Fair value measurements
Cash equivalents	75,501	86,965
Recurring | Level 2 | Money market funds
Fair value measurements
Cash equivalents	$ 75,501	$ 86,965

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition - License revenue (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jan. 31, 2024	Apr. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	May 31, 2021	Nov. 30, 2020
Agreements
Revenue			$ 84,819	$ 65,267
Distribution agreement | Adium | Subsequent Event
Agreements
Revenue	$ 500
License
Agreements
Revenue			500	16,000
License | Development and commercialization arrangement | SciClone
Agreements
Revenue				$ 15,000
Maximum regulatory-based milestone payments receivable					$ 40,000
Maximum sales-based milestone payments receivable					60,000
License | License and distribution agreement | Takeda Israel
Agreements
Revenue					$ 250
Maximum regulatory-based milestone payments receivable							$ 750
Maximum sales-based milestone payments receivable							$ 500
License | Distribution agreement | Adium
Agreements
Revenue		$ 1,000	$ 500
Maximum regulatory-based milestone payments receivable						$ 3,000

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Segment Information (Details)	12 Months Ended
	Dec. 31, 2023 segment
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Number of Operating Segments	1

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property and Equipment
Depreciation expense	$ 386	$ 662
Asset Impairment
Impairment of long-lived assets	$ 0	$ 617
Furniture and fixtures
Property and Equipment
Estimated Useful Life	5 years
Machinery and equipment
Property and Equipment
Estimated Useful Life	5 years
Leasehold improvements | Maximum
Property and Equipment
Estimated Useful Life	15 years

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Income Taxes (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Cost incurred as a result of GILTI	$ 0

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Foreign currency translation gain (loss)	$ (882)	$ (40)
Foreign currency transaction gain (loss)	$ 524	$ (848)

PRODUCT REVENUE NET - Disaggreg

PRODUCT REVENUE NET - Disaggregation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue
Revenue	$ 84,819	$ 65,267
Product
Revenue
Revenue	84,319	49,267
United States | Product
Revenue
Revenue	67,814	46,259
Other countries | Product
Revenue
Revenue	16,505	$ 3,008
Other countries | Product | Distribution agreement | SciClone
Revenue
Revenue	3,535
Other countries | Product | Distribution agreement | WEP
Revenue
Revenue	$ 8,621

PRODUCT REVENUE, NET - Concentr

PRODUCT REVENUE, NET - Concentrations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Concentration risk
Revenue	$ 84,819	$ 65,267
Contractual Allowances and Government Rebates, Change in estimate	(1,090)
Product
Concentration risk
Revenue	84,319	49,267
Product, Royalty | Distribution partner
Concentration risk
Revenue	$ 4,453	$ 2,120
McKesson | Customer Concentration Risk | Revenue | Product
Concentration risk
Concentration risk percentage (as a percent)	46%	71%
AmerisourceBergen | Customer Concentration Risk | Revenue | Product
Concentration risk
Concentration risk percentage (as a percent)	22%	17%
WEP | Customer Concentration Risk | Revenue | Product
Concentration risk
Concentration risk percentage (as a percent)	10%
Cardinal Health | Customer Concentration Risk | Revenue | Product
Concentration risk
Concentration risk percentage (as a percent)	13%	10%

PRODUCT REVENUE, NET - Receivab

PRODUCT REVENUE, NET - Receivables, allowances and accrued liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Revenue
Accounts receivable	$ 22,454	$ 12,531
Accrued liabilities	13,166	$ 13,241
Product | WEP | Distribution agreement
Revenue
Accounts receivable	5,834
Accounts receivable, unbilled portion	3,684
Accrued liabilities	$ 326

PRODUCT REVENUE, NET - Reserves

PRODUCT REVENUE, NET - Reserves for discounts and allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue
Revenue	$ 84,819	$ 65,267
Change in reserves for discounts and allowances
Discounts, Balance at beginning of period	33
Discounts, Current provisions relating to sales in current year	238
Discounts, Payments/credits relating to sales in current year	(230)
Discounts, Balance at end of period	41	33
Contractual Allowances and Government Rebates, Balance at beginning of period	2,905
Contractual Allowances and Government Rebates, Current provisions relating to sales in current year	8,361
Contractual Allowances and Government Rebates, Payments/credits relating to sales in current year	(7,482)
Contractual Allowances and Government Rebates, Change in estimate related to sales in the prior year	(1,090)
Contractual Allowances and Government Rebates, Balance at end of period	2,694	2,905
Returns, Balance at beginning of period	44
Returns, Current provisions relating to sales in current year	519
Returns, Payments/credits relating to sales in current year	(497)
Returns, Balance at end of period	66	44
Reserves for discounts and allowances, Balance at beginning of period	2,982
Reserves for discounts and allowances, Current provisions relating to sales in current year	9,118
Reserves for discounts and allowances, Payments/credits relating to sales in current year	(8,209)
Reserves for discounts and allowances, Change in estimate related to sales in the prior year	(1,090)
Reserves for discounts and allowances, Balance at end of period	2,801	2,982
Contractual Allowances and Government Rebates, Change in estimate	(1,090)
Accounts receivable
Change in reserves for discounts and allowances
Reserves for discounts and allowances, Balance at beginning of period	508
Reserves for discounts and allowances, Balance at end of period	492	508
Accrued liabilities
Change in reserves for discounts and allowances
Reserves for discounts and allowances, Balance at beginning of period	2,474
Reserves for discounts and allowances, Balance at end of period	$ 2,309	$ 2,474

NET LOSS PER SHARE - Basic and

NET LOSS PER SHARE - Basic and diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
NET LOSS PER SHARE
Net loss (numerator), Basic (in dollars)	$ (21,427)	$ (95,568)
Net loss (numerator), Diluted (in dollars)	$ (21,427)	$ (95,568)
Weighted-average shares (denominator), basic (in shares)	43,645,388	43,703,663
Weighted-average shares (denominator), diluted (in shares)	43,645,388	43,703,663
Basic net loss per share (in dollars per share)	$ (0.49)	$ (2.19)
Diluted net loss per share (in dollars per share)	$ (0.49)	$ (2.19)

NET LOSS PER SHARE - Anti-dilut

NET LOSS PER SHARE - Anti-dilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
NET LOSS PER SHARE
Potentially dilutive securities outstanding	9,658,737	7,113,122

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Inventories
Work In Progress	$ 14,021	$ 11,317
Finished Goods	2,992	666
Total Inventories	17,013	11,983
CURRENT ASSETS
Inventories	5,065	6,702
NONCURRENT ASSETS
Inventories, Noncurrent	11,948	5,281
Inventory write-offs	831	1,200
Other long-term assets
Inventories
Work In Progress	11,948	5,281
NONCURRENT ASSETS
Inventories, Noncurrent	$ 11,948	$ 5,281

INTANGIBLE ASSETS, NET (Details

INTANGIBLE ASSETS, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023
Intangible assets
Intangible assets, net	$ 2,986	$ 2,631
Accumulated amortization	314	$ 669
Amortization period		10 years
Forecasted amortization expense
2024		$ 355
2025		355
2026		355
2027		355
2028		355
Thereafter		$ 856
SciClone | Development and commercialization arrangement
Intangible assets
Amount of regulatory payments received and recognized during period	15,000
SciClone | Development and commercialization arrangement | Capitalized milestone payments
Intangible assets
Intangible asset recognized during the period	$ 1,500

ACCRUED LIABILITIES (Details)

ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued liabilities
Accrued licensing milestone and royalty payments	$ 3,452	$ 4,002
Accrued clinical costs	597	932
Accrued compensation and board fees	3,858	2,445
Accrued manufacturing costs	2,531	2,977
Accrued sales reserves	2,309	2,474
Other	419	411
Total	$ 13,166	$ 13,241

LICENSE AGREEMENTS AND COMMIT_3

LICENSE AGREEMENTS AND COMMITMENTS - MSK License Agreement (Details) - License Agreement - MSK $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) agreement
Agreements
Number of license agreements | agreement	3
Annual minimum royalties payable | $	$ 80
Percentage of income generated from sale of first PRV MSK is entitled to receive	40%
Percentage of income generated from sale of subsequent PRV MSK is entitled to receive	33%
Minimum term of license agreement	15 years

LICENSE AGREEMENTS AND COMMIT_4

LICENSE AGREEMENTS AND COMMITMENTS - CD33 License (Details) - CD33 License Agreement - MSK $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Agreements
Annual minimum royalties payable from tenth anniversary	$ 40
Annual minimum royalties payable once patent has been issued	$ 60
Percentage of income generated from sale of PRV MSK is entitled to receive	25%
Minimum term of license agreement	15 years

LICENSE AGREEMENTS AND COMMIT_5

LICENSE AGREEMENTS AND COMMITMENTS - MabVax/MSK License (Details) - License Agreement - MabVax	12 Months Ended
	Dec. 31, 2023
Agreements
Percentage of income generated from sale of PRV MSK is entitled to receive	20%
Minimum term of license agreement	10 years

LICENSE AGREEMENTS AND COMMIT_6

LICENSE AGREEMENTS AND COMMITMENTS - SADA License Agreement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Agreements
Accrued milestone and royalty payments	$ 5,375	$ 2,250
SADA License Agreement | MSK and MIT
Agreements
Annual minimum royalties payable from tenth anniversary	40
Annual minimum royalties payable once patent has been issued	60
Maximum sales based milestone payments due for each construct previously generated	60,000
Expense	4,125	0
Accrued liabilities	1,000	605
Accrued milestone and royalty payments	3,125
Cash paid	$ 605	$ 1,000

LICENSE AGREEMENTS AND COMMIT_7

LICENSE AGREEMENTS AND COMMITMENTS - Summary of Significant Agreements and Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Financial statement information
Accrued liabilities, current	$ 13,166	$ 13,241
Accrued liabilities, noncurrent	5,375	2,250
License Agreement | MSK
Milestones
Maximum Clinical Milestones	2,450
Maximum Regulatory Milestones	9,000
Maximum Sales-based Milestones	20,000
Financial statement information
Cash paid	6,027	2,871
Expense	5,158	3,582
Accrued liabilities, current	2,452	3,397
Accrued liabilities, noncurrent	1,950	1,950
License Agreement | MabVax
Milestones
Maximum Clinical Milestones	200
Maximum Regulatory Milestones	1,200
Financial statement information
Cash paid	10	10
Expense	10	10
CD33 License Agreement | MSK
Milestones
Maximum Clinical Milestones	550
Maximum Regulatory Milestones	500
Maximum Sales-based Milestones	7,500
Financial statement information
Cash paid		150
Accrued liabilities, noncurrent	300	300
SADA License Agreement | MSK and MIT
Milestones
Maximum Clinical Milestones	4,730
Maximum Regulatory Milestones	18,125
Maximum Sales-based Milestones	23,750
Financial statement information
Cash paid	605	1,000
Expense	4,125	0
Accrued liabilities, current	1,000	605
Accrued liabilities, noncurrent	3,125
Accrued liabilities	$ 1,000	$ 605

LICENSE AGREEMENTS AND COMMIT_8

LICENSE AGREEMENTS AND COMMITMENTS - Other agreements (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2023 USD ($) employee agreement	Dec. 31, 2022 USD ($)
Agreements
Research and development		$ 54,219	$ 91,572
Other agreements | MSK
Agreements
Research and development		$ 190	$ 1,746
Core Facility Service Agreements | MSK
Agreements
Number of service agreements | agreement		2
Sponsored Research Agreement | MSK
Agreements
Research service period	3 years
Researchers, Employees of MSK | Master Data Services Agreement | MSK | Maximum
Agreements
Number of individuals | employee		5

LICENSE AGREEMENTS AND COMMIT_9

LICENSE AGREEMENTS AND COMMITMENTS - Lease agreements (Details) $ in Thousands	1 Months Ended
	Feb. 28, 2019 ft²	Aug. 31, 2023 USD ($)	Jul. 31, 2023 USD ($)	Nov. 01, 2021 USD ($)	Dec. 31, 2019 ft²	Jan. 31, 2018
Laboratory, New Jersey
Leases
Leased area (in square feet) | ft²	4,548
Additional leased area (in square feet) | ft²					235
Lease term	3 years
Option to extend	true
Option to extend, period	2 years
Fixed rent payable per annum			$ 177
Lease payable per month			$ 15
Corporate headquarters, New York
Leases
Lease term						6 years
Fixed rent payable per annum		$ 408
Lease payable per month		$ 34
Office space, Denmark
Leases
Lease term				4 years
Lease payable per month				$ 41

LICENSE AGREEMENTS AND COMMI_10

LICENSE AGREEMENTS AND COMMITMENTS - Lease costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases
Total operating lease costs	$ 1,033	$ 2,646
Cash paid for amounts included in the measurement of lease liabilities	1,057	2,286
Research and development expense
Leases
Total operating lease costs	780	2,404
Selling, general, and administrative
Leases
Total operating lease costs	$ 253	$ 242

LICENSE AGREEMENTS AND COMMI_11

LICENSE AGREEMENTS AND COMMITMENTS - Lease maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Maturities of operating lease liabilities
First fiscal year	$ 996	$ 997
Second fiscal year	526	490
Third fiscal year		419
Total lease payments	1,522	1,906
Less: Imputed interest	(103)	(139)
Total operating lease liabilities as of end of period	$ 1,419	$ 1,767
Operating Lease, Liability, Statement of Financial Position	Operating lease liabilities, current portion, Operating lease liabilities, long-term portion	Operating lease liabilities, current portion, Operating lease liabilities, long-term portion

LICENSE AGREEMENTS AND COMMI_12

LICENSE AGREEMENTS AND COMMITMENTS - Lease term and discount rate (Details)	Dec. 31, 2023	Dec. 31, 2022
LICENSE AGREEMENTS AND COMMITMENTS
Weighted average remaining lease term	1 year 7 months 9 days	2 years 4 months 9 days
Weighted average discount rate	8.30%	8.30%

LICENSE AGREEMENTS AND COMMI_13

LICENSE AGREEMENTS AND COMMITMENTS - Severance Related Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Stock Option
Severance Agreement
Stock-based compensation expenses	$ 13,757	$ 25,274
Chief Executive Officer, Former
Severance Agreement
Cash compensation for salary and certain benefits continuation		1,589
Total charge related to executive management change		10,875
Chief Executive Officer, Former | Employee Stock Option
Severance Agreement
Stock-based compensation expenses		$ 9,286

LICENSE AGREEMENTS AND COMMI_14

LICENSE AGREEMENTS AND COMMITMENTS - Legal matters (Details) - Class-action lawsuit filed in the U.S. District Court, Southern District of New York, on January 18, 2023	Feb. 05, 2024 category defendant
Legal Matters
Number of categories of challenged statements related to plaintiff claims dismissed by court	3
Number of categories of challenged statements related to plaintiff claims	4
Number of individual defendants the court dismissed | defendant	1

STOCKHOLDERS' EQUITY - Authoriz

STOCKHOLDERS' EQUITY - Authorized, Common and Preferred Stock (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Vote $ / shares shares	Dec. 31, 2022 USD ($) Vote $ / shares shares
STOCKHOLDERS' EQUITY
Total shares authorized	105,500,000	105,500,000
Common stock, authorized shares	100,000,000	100,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Preferred stock, authorized shares	5,500,000	5,500,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Number of votes per common share | Vote	1	1
Common stock dividends issued | $	$ 0	$ 0
Common stock, shares issued	43,672,112	43,670,109
Preferred stock, shares issued	0	0

STOCKHOLDERS' EQUITY - Stock Gr

STOCKHOLDERS' EQUITY - Stock Grant Agreements with Non-Employees (Details) $ in Thousands	1 Months Ended					12 Months Ended		45 Months Ended
	Jun. 30, 2023 USD ($) shares	Apr. 30, 2023	Jul. 31, 2022 USD ($) shares	Jul. 31, 2020 USD ($) individual	Apr. 30, 2020 USD ($) individual agreement shares	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2023 shares
Share-Based Compensation Awards
Retirement of treasury shares, Reduction in outstanding stock and reduction of APIC (in dollars) | $	$ 480					$ 480	$ 963
SADA License Agreement | MSK and MIT
Share-Based Compensation Awards
Impairment charge | $							$ 1,051
Retirement of treasury shares, Reduction in outstanding stock and reduction of APIC (in dollars) | $	$ 480		$ 963			$ 963
SADA License Agreement | MSK and MIT | Researchers, Employees of MSK
Share-Based Compensation Awards
Number of individuals | individual				2
Notes receivable, noncurrent | $				$ 2,610
Notes receivable interest rate (as a percent)				1%
SADA License Agreement | MSK and MIT | Nonemployees | Researchers, Employees of MSK
Share-Based Compensation Awards
Number of stock grant agreements entered into | agreement					2
Number of individuals | individual					2
Vested (in shares) | shares								213,996
Vested (as a percent)		20%
SADA License Agreement | MSK and MIT | Nonemployees | Researchers, Employees of MSK | Research and development expense
Share-Based Compensation Awards
Non-cash expense in connection with equity issuance to non-employees | $					$ 7,376
SADA License Agreement | MSK and MIT | Nonemployees | Researchers, Employees of MSK | Tranche one
Share-Based Compensation Awards
Vesting (as a percent)					40%
SADA License Agreement | MSK and MIT | Nonemployees | Researchers, Employees of MSK | Tranche two
Share-Based Compensation Awards
Vesting (as a percent)					60%
Vesting period					3 years
Common Stock
Share-Based Compensation Awards
Number of shares exchanged | shares						58,763	57,887
Common Stock | SADA License Agreement | MSK and MIT
Share-Based Compensation Awards
Number of shares exchanged | shares	58,763		57,887
Common Stock | SADA License Agreement | MSK and MIT | Nonemployees | Researchers, Employees of MSK
Share-Based Compensation Awards
Issuance of common stock to non-employees (in shares) | shares					213,996	0	0
Shares agreed to be issued | shares					213,996

STOCK-BASED COMPENSATION - 2015

STOCK-BASED COMPENSATION - 2015 Plan (Details) - 2015 Plan	12 Months Ended
	Dec. 31, 2015 shares
Share-Based Compensation Awards
Shares reserved for issuance	4,500,000
Vesting period	4 years

STOCK-BASED COMPENSATION - 2018

STOCK-BASED COMPENSATION - 2018 Plan (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2018
Employee Stock Option | Maximum
Share-Based Compensation Awards
Term of award	10 years	10 years
2018 Plan
Share-Based Compensation Awards
Shares reserved for issuance			5,500,000
Shares available for grant	3,107,673
2018 Plan | Maximum
Share-Based Compensation Awards
Annual increase on share reserve (as a percent)	4%
2018 Plan | Employee Stock Option | Minimum
Share-Based Compensation Awards
Vesting period	1 year
2018 Plan | Employee Stock Option | Maximum
Share-Based Compensation Awards
Vesting period	4 years
2018 Plan | Employee Stock Option | Employees and nonemployees owning less than 10% of voting power | Maximum
Share-Based Compensation Awards
Term of award	10 years
2018 Plan | Employee Stock Option | Participants owning more than 10% of voting power | Minimum
Share-Based Compensation Awards
Ownership (as a percent)	10%
Option price as percentage of fair market value of common stock on the date of grant	110%
2018 Plan | Employee Stock Option | Participants owning more than 10% of voting power | Maximum
Share-Based Compensation Awards
Term of award	5 years

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock-based compensation expense - Options (Details) - Employee Stock Option - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Awards
Stock-based compensation expenses	$ 13,757	$ 25,274
Share based compensation acceleration cost	1,706
Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	8,000	7,540
Selling, general, and administrative
Share-Based Compensation Awards
Stock-based compensation expenses	$ 5,757	17,734
Chief Executive Officer, Former
Share-Based Compensation Awards
Stock-based compensation expenses		$ 9,286

STOCK-BASED COMPENSATION - St_2

STOCK-BASED COMPENSATION - Stock Option Valuation (Details) - Employee Stock Option	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock Option Valuation
Risk-free interest rate (as a percent)	3.92%	3.12%
Expected term (in years)	6 years 2 months 12 days	5 years 10 months 24 days
Expected volatility (as a percent)	82.90%	73.60%

STOCK-BASED COMPENSATION - St_3

STOCK-BASED COMPENSATION - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Options
Outstanding and expected to vest at beginning of period (in shares)	7,079,767
Granted (in shares)	2,586,040	653,000
Exercised (in shares)	(50,000)
Forfeited, shares (in shares)	(308,477)
Outstanding and expected to vest at end of period (in shares)	9,307,330	7,079,767
Exercisable at end of period (in shares)	5,958,167
Weighted average exercise price
Outstanding and expected to vest at beginning of period (in dollars per share)	$ 21.27
Granted (in dollars per share)	5.25
Exercised (in dollars per share)	2
Forfeited (in dollars per share)	11.10
Outstanding and expected to vest at end of period (in dollars per share)	17.26	$ 21.27
Exercisable at end of period (in dollars per share)	$ 21
Aggregate intrinsic value
Outstanding and expected to vest (in dollars)	$ 10,012	$ 3,112
Exercisable (in dollars)	$ 6,195
Weighted average remaining contractual life (years)
Outstanding and expected to vest (in years)	6 years 5 months 8 days	6 years 5 months 12 days
Exercisable (in years)	5 years 10 days

STOCK-BASED COMPENSATION - St_4

STOCK-BASED COMPENSATION - Stock option grants (Details) - $ / shares	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Awards
Weighted average grant-date fair value of stock options granted (in dollars per share)		$ 3.86	$ 7.64
Granted (in shares)		2,586,040	653,000
Employee Stock Option
Share-Based Compensation Awards
Expected term (in years)		6 years 2 months 12 days	5 years 10 months 24 days
Expected volatility, Minimum (as a percent)		82.40%
Expected volatility, Maximum (as a percent)		86.70%
Risk-free interest rate (as a percent)		3.92%	3.12%
Risk-free interest rate, Minimum (as a percent)		3.50%
Risk-free interest rate, Maximum (as a percent)		4.70%
Employee Stock Option | Minimum
Share-Based Compensation Awards
Expected term (in years)		5 years 6 months
Employee Stock Option | Maximum
Share-Based Compensation Awards
Term of award		10 years	10 years
Expected term (in years)		6 years 3 months
Employee Stock Option | Continuing employees under retention program
Share-Based Compensation Awards
Granted (in shares)		1,105,500
Employee Stock Option | Non-executive directors
Share-Based Compensation Awards
Term of award	5 years 6 months
Granted (in shares)	83,700
Vesting period	12 months
Risk-free interest rate (as a percent)	3.90%
Employee Stock Option | Other individuals
Share-Based Compensation Awards
Granted (in shares)		1,396,840
Employee Stock Option | Certain senior executives related to start date of the Company's new President and CEO and transition of executives
Share-Based Compensation Awards
Granted (in shares)		690,240
Employee Stock Option | Tranche one | Other individuals
Share-Based Compensation Awards
Vesting (as a percent)		25%
Employee Stock Option | Tranche two | Other individuals
Share-Based Compensation Awards
Vesting period		36 months

STOCK-BASED COMPENSATION - St_5

STOCK-BASED COMPENSATION - Stock option unrecognized compensation (Details) - Employee Stock Option $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Unrecognized compensation related to employee stock options
Unrecognized compensation	$ 15,937
Expected vesting period	2 years 9 months

STOCK-BASED COMPENSATION - Rest

STOCK-BASED COMPENSATION - Restricted Stock Units (Details) - RSUs $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares
Share-Based Compensation Awards
Stock-based compensation expenses | $	$ 696	$ 328
Restricted stock units issued and outstanding
Outstanding and expected to vest at beginning of period (in shares)	33,355
Granted (in shares)	389,898
Vested (in shares)	(10,766)
Forfeited (in shares)	(61,080)
Outstanding and expected to vest at end of period (in shares)	351,407	33,355
Weighted average grant price
Weighted average grant price, Outstanding and expected to vest, Beginning of period (in dollars per share) | $ / shares	$ 17.77
Weighted average grant price, Granted (in dollars per share) | $ / shares	4.84
Weighted average grant price, Vested (in dollars per share) | $ / shares	18.90
Weighted average grant price, Forfeited (in dollars per share) | $ / shares	8.12
Weighted average grant price, Outstanding and expected to vest, End of period (in dollars per share) | $ / shares	$ 5.06	$ 17.77
Unrecognized compensation | $	$ 1,338
Weighted average remaining vesting life	1 year 11 months 26 days	1 year 9 months 7 days
Continuing employees under retention program
Restricted stock units issued and outstanding
Granted (in shares)	362,400
Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses | $	$ 410	$ 289
Selling, general, and administrative
Share-Based Compensation Awards
Stock-based compensation expenses | $	$ 286	$ 39

INCOME TAXES - Loss before inco

INCOME TAXES - Loss before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Domestic and foreign loss before income taxes:
United States	$ (17,232)	$ (87,827)
Foreign	(3,634)	(7,741)
LOSS BEFORE INCOME TAXES	$ (20,866)	$ (95,568)

INCOME TAXES - Current and defe

INCOME TAXES - Current and deferred income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current income tax
Federal	$ 200
State	361
Foreign		$ 18
Total current income taxes (tax benefits)	561	18
Deferred income tax
Foreign		(18)
Total deferred income taxes (tax benefits)		(18)
Total income taxes (tax benefits)	$ 561	$ 0

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
INCOME TAXES
U.S. federal statutory income tax rate (as a percent)	21%	21%
Difference between income taxes expected at U.S. federal statutory income tax rate and income taxes provided:
Taxes on income at U.S. federal statutory rate	$ (4,382)	$ (20,069)
State and local taxes, net of federal tax effects	(411)	(5,661)
Effect of rate change	(2,127)	861
Foreign tax rate differential	(110)	(95)
Valuation allowance	6,407	25,116
Tax credits	(135)	(1,749)
Uncertain tax position		18
Deferred adjustments	439	969
Shared based compensation	1,011	1,265
Other	(131)	(655)
Total income taxes (tax benefits)	$ 561	$ 0

INCOME TAXES - Deferred assets

INCOME TAXES - Deferred assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets/(liabilities)::
Acquired intangibles	$ 3,702	$ 2,657
Unrealized foreign exchange loss, tax asset		263
Unrealized foreign exchange loss, tax liability	(87)
Accrued royalty	671	914
Stock based compensation	11,603	13,353
Net operating loss carryforwards	83,237	86,072
Tax credit carryforwards	16,336	16,799
Right of use asset	(507)	(413)
Lease liability	515	435
Capitalized research and experimentation	33,088	21,902
Other deferred assets	402	572
Total deferred tax assets/(liabilities)	148,960	142,554
Valuation allowance	(148,960)	(142,554)
Net deferred tax assets/(liabilities)

INCOME TAXES - Net Operating Lo

INCOME TAXES - Net Operating Loss Carryforwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
U.S. federal
Operating Loss Carryforwards
Net operating loss carryforwards	$ 245,242
Tax credit carryforwards	16,336
Operating loss carryforward, indefinite	245,242
State
Operating Loss Carryforwards
Net operating loss carryforwards	189,831
Danish
Operating Loss Carryforwards
Net operating loss carryforwards	$ 21,628

INCOME TAXES - Unrecognized tax

INCOME TAXES - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
INCOME TAXES
Unrecognized tax benefits, Beginning balance	$ 0	$ 304
Additions for prior year tax positions		18
Settlements (decrease)		(322)
Unrecognized tax benefits, Ending balance	$ 0	$ 0

OTHER BENEFITS (Details)

OTHER BENEFITS (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
United States
Benefit plan
Employer matching contribution to defined contribution plan (as a percent)	0%	0%
Denmark
Benefit plan
Employer matching contribution to defined contribution plan (as a percent)	0%	0%

RESTRUCTURING CHARGE (Details)

RESTRUCTURING CHARGE (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2023	Dec. 31, 2023
RESTRUCTURING CHARGE
Reduction in workforce (as a percent)	35%
Restructuring charges		$ 4,482
Research and development expense
RESTRUCTURING CHARGE
Restructuring charges		3,346
Selling, general, and administrative
RESTRUCTURING CHARGE
Restructuring charges		1,136
Employee severance
RESTRUCTURING CHARGE
Severance termination benefits		2,776
Share based compensation acceleration cost		$ 1,706

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)	$ (21,427)	$ (95,568)

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