Y-mAbs Therapeutics (YMAB) 10-Q 9 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 04, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		43,718,165
Entity Central Index Key	0001722964
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
CURRENT ASSETS
Cash and cash equivalents	$ 156,724	$ 181,564
Accounts receivable, net	9,324	7,712
Inventories	5,588	5,512
Other current assets	6,103	7,473
Total current assets	177,739	202,261
Property and equipment, net	1,697	1,847
Operating lease right-of-use assets	3,155	3,842
Intangible assets, net	1,618	1,663
Other assets	6,838	3,170
TOTAL ASSETS	191,047	212,783
LIABILITIES
Accounts payable	14,661	13,552
Accrued liabilities	12,930	12,540
Operating lease liabilities, current portion	1,451	1,783
Total current liabilities	29,042	27,875
Accrued milestone and royalty payments	2,100	2,100
Operating lease liabilities, long-term portion	1,598	1,851
Other liabilities	835	851
TOTAL LIABILITIES	33,575	32,677
Commitments and contingencies (Note 9)
STOCKHOLDERS' EQUITY
Preferred stock, $0.0001 par value, 5,500,000 shares authorized and none issued at March 31, 2022 and December 31, 2021
Common stock, $0.0001 par value, 100,000,000 shares authorized at March 31, 2022 and December 31, 2021; 43,718,165 and 43,694,716 shares issued at March 31, 2022 and December 31, 2021, respectively	4	4
Additional paid in capital	524,329	519,206
Accumulated other comprehensive income	1,682	1,371
Accumulated deficit	(368,543)	(340,475)
TOTAL STOCKHOLDERS' EQUITY	157,472	180,106
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 191,047	$ 212,783

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
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	43,718,165	43,694,716

Consolidated Statements of Net

Consolidated Statements of Net Income (Loss) and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
REVENUES
Total revenues	$ 10,486	$ 5,383
Revenue from Contract with Customer, Product and Service	Product	Product
OPERATING COSTS AND EXPENSES
Cost of goods sold	$ 1,831	$ 93
Research and development	22,912	21,579
Selling, general, and administrative	13,438	11,970
Total operating costs and expenses	38,181	33,642
Loss from operations	(27,695)	(28,259)
OTHER INCOME / (LOSS), NET
Gain from sale of priority review voucher, net		62,010
Interest and other loss	(373)	(338)
NET INCOME / (LOSS)	(28,068)	33,413
Other comprehensive income / (loss)
Foreign currency translation	311	435
COMPREHENSIVE INCOME / (LOSS)	$ (27,757)	$ 33,848
Net income / (loss) per share attributable to common stockholders, basic (in dollars per share)	$ (0.64)	$ 0.80
Weighted average common shares outstanding, basic (in shares)	43,709,238	41,870,759
Net income / (loss) per share attributable to common stockholders, diluted (in dollars per share)	$ (0.64)	$ 0.75
Weighted average common shares outstanding, diluted (in shares)	43,709,238	44,383,791

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, 2020	$ 4	$ 391,558	$ (526)	$ (285,200)	$ 105,836
Balance at the beginning of period (in shares) at Dec. 31, 2020	40,688,447
Increase (Decrease) in Stockholders' Equity
Issuance of common stock to investors, net of issuance costs		107,725			107,725
Issuance of common stock to investors, net of issuance costs (in shares)	2,804,878
Exercise of stock options		110			110
Exercise of stock options (in shares)	46,000
Stock-based compensation expense		4,698			4,698
Stock-based compensation expense (in shares)	9,094
Foreign currency translation			435		435
Net loss				33,413	33,413
Balance at the end of period at Mar. 31, 2021	$ 4	504,091	(91)	(251,787)	252,217
Balance at the end of period (in shares) at Mar. 31, 2021	43,548,419
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		32			$ 32
Exercise of stock options (in shares)	16,000				16,000
Stock-based compensation expense		5,091			$ 5,091
Stock-based compensation expense (in shares)	7,449
Foreign currency translation			311		311
Net loss				(28,068)	(28,068)
Balance at the end of period at Mar. 31, 2022	$ 4	$ 524,329	$ 1,682	$ (368,543)	$ 157,472
Balance at the end of period (in shares) at Mar. 31, 2022	43,718,165

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (28,068)	$ 33,413
Adjustments to reconcile net loss to net cash used in operating activities:
Gain from sale of priority review voucher, net		(62,010)
Depreciation and amortization	195	130
Stock-based compensation	5,091	4,698
Foreign currency transactions	311	435
Changes in assets and liabilities:
Accounts receivable, net	(1,612)	(5,997)
Inventories	(76)	(1,005)
Other current assets	1,370	2,993
Other assets	(3,668)	(1,543)
Accounts payable	1,109	(2,829)
Accrued liabilities and other	423	(146)
NET CASH USED IN OPERATING ACTIVITIES	(24,925)	(31,861)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment		(400)
Net proceeds from sale of priority review voucher		62,010
NET CASH PROVIDED BY INVESTING ACTIVITIES		61,610
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock, net of issuance costs		107,725
Proceeds from exercised stock options	32	110
NET CASH PROVIDED BY FINANCING ACTIVITIES	32	107,835
Effect of exchange rates on cash and cash equivalents	53	53
NET INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS	(24,840)	137,637
Cash and cash equivalents at the beginning of period	181,564	114,634
Cash and cash equivalents at the end of period	156,724	252,271
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Property and equipment purchases in accounts payable		$ 60
Intangible assets acquisition in accrued milestones and royalty payments	$ 1,500

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF BUSINESS	3 Months Ended
	Mar. 31, 2022
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. We are leveraging our 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	3 Months Ended
	Mar. 31, 2022
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE 2—BASIS OF PRESENTATION Except for the quarter ended March 31, 2021, the Company has incurred losses 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 U.S. Food and Drug Administration (“FDA”) approval in the United States and regulatory approval in other jurisdictions; marketing or sales capability or experience; uncertainty in getting adequate payer 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 (naxitamab-gqgk) was approved by the U.S. 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 efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. The Company’s 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 $368,543,000 as of March 31, 2022 and $340,475,000 as of December 31, 2021. Through March 31, 2022, the Company has funded its operations primarily through proceeds from sales of shares of its common stock, including its initial public offering in September 2018 and its subsequent public offerings in November 2019 and February 2021, as well as additional funding from the proceeds from the sales of DANYELZA and from proceeds from the sale of the DANYELZA PRV. On February 22, 2021, the Company announced the closing of its public offering of 2,804,878 shares of its common stock, at a public offering price of $41.00 per share, which includes the exercise in full of the underwriters' option to purchase 365,853 additional shares of common stock. The aggregate gross proceeds to the Company, before deducting underwriting discounts and commissions and offering expenses payable by the Company, were approximately $115,000,000. As of March 31, 2022, the Company had cash and cash equivalents of $156,724,000, and as of December 31, 2021 the Company had cash and cash equivalents of $181,564,000. As of the issuance date of the financial statements for the first quarter ended March 31, 2022, the Company expects that its cash and cash equivalents at March 31, 2022 will be sufficient to fund its operating expenses and capital expenditure requirements through at least the next 12 months, irrespective of whether any additional product approvals are obtained. The Company may raise additional capital to fund future operations through the sale of its equity securities, incurring debt, entering into licensing or collaboration agreements with partners, grants or other sources of financing. Sufficient funds may not be available to the Company on attractive terms or at all when needed from equity or debt financing. If FDA approval for omburtamab does not occur or is significantly delayed, and 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 its liquidity position which may include significantly reducing the current rate of spending through delaying, scaling back current operations, or suspending certain research and development programs and other operational programs. The accompanying unaudited consolidated financial statements reflect the accounts of the Company and its wholly- owned subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information, Accounting Standards Codification (“ASC”) Topic 270-10 and with the instructions to Form 10-Q. Accordingly, these financial statements do not include all of the information and notes required by GAAP for complete financial statements. The unaudited interim financial statements include all adjustments (consisting only of normal recurring nature) necessary in the judgment of management for a fair statement of the results for the periods presented. All intercompany balances and transactions have been eliminated. The Company has evaluated subsequent events through the date of this filing. Operating results for the three-month period ended March 31, 2022 are not necessarily indicative of the results that may be expected for the year ended December 31, 2022, any other interim periods, or any future year or period. The December 31, 2021 consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. You should read these unaudited interim consolidated financial statements in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2022
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	​ NOTE 3—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Our significant accounting policies are detailed in our Annual Report on Form 10-K for the year ended December 31, 2021. 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 any losses on its cash and cash equivalents. The carrying amount of cash and cash equivalents approximates its fair value due to its short-term and liquid nature. We maintain 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. We do not anticipate any losses with respect to such cash balances. Trade Accounts Receivables The Company’s trade accounts receivable 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 account 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 our customers and has not recognized any allowance for doubtful accounts nor reversed any allowances in the three months ended March 31, 2022. Concentration of Credit Risk The Company product sales are made through arrangements primarily with three national speciality distributors in the United States of America. As of March 31, 2022, the receivables balances from such distributors totaled 94% of our outstanding accounts receivable. The Company has contractual payment terms with each of its customers and the Company monitors their financial performance, historical payment terms and credit worthiness to timely assess and respond to any changes in their credit profile. Inventory The Company values its 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. Prior to FDA approval, the Company expensed such costs as part of research and development expenses. 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. No material inventory write-downs occurred in the three months ended March 31, 2022. 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 its cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at March 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 Total ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2021 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729 Total ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729 ​ During the quarter ended March 31, 2022, there were no transfers Level 3 Operating Leases 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 its 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 its estimated incremental borrowing rate based on information available at the lease commencement date. Because most of the Company’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 it 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 the lease which are included in the lease term when it is reasonably certain that it 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, we will not recognize right-of-use assets or liabilities, and this includes not recognizing right-of-use assets or liabilities for existing short-term leases of those assets in transition. We also elect 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 Use of Estimates The preparation of 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 financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these 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, and the valuation of stock options. 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. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including expenses, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international markets. Revenue Recognition - Product revenue We recognize revenue from sales of DANYELZA at a point in time when our customer is deemed to have obtained control of the product, which generally occurs upon receipt at the end-user hospital. ​ The amount of revenue we recognize 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, we estimate, utilizing the expected value method, the amount of revenue that we 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 we review these estimates quarterly. If actual results vary from our original estimates, we will adjust these estimates quarterly, which would affect net product revenue and earnings in the period such variances occur. ​ ● Rebates and chargebacks ​ We contract with United States governmental agencies to ensure that DANYELZA will be eligible for coverage under the various programs administered by the agencies. We estimate the rebates and chargebacks to be provided and deduct these estimated amounts from our 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. We develop 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. Our liability for these rebates and chargebacks mainly consists of claims for which invoices have not yet been received and paid. We do not maintain material levels of inventory in the wholesale or retail channel. ​ ● Discounts and distribution-related fees ​ We provide invoice discounts on DANYELZA sales to our 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, we expect our distributors to earn these discounts and fees and deduct the full amount of these discounts and fees from our gross product revenue at the time such revenues are recognized. ​ ● Returns ​ We offer our customers limited product return rights for damaged, defective, or expiring products. We estimate 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 an establishment of an accrued liability. ​ Segment Information The Company is engaged solely in the discovery, development, distribution and commercialization of novel antibody-based therapeutic products for the treatment of cancer. Accordingly, the Company has determined that it operates in one operating segment. Recently Issued Accounting Pronouncements – Adopted 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 2020-10, ASU 2021-04 and ASU 2020-06 effective January 1, 2022, and the adoption of these new standards did not have a material impact on the Company’s consolidated financial statements or disclosures. The Company has evaluated accounting pronouncements recently issued but not yet adopted and believes that these pronouncements do not apply to the Company’s operations and therefore will not have a material impact on the Company’s consolidated financial statements or disclosures. ​

PRODUCT REVENUE

PRODUCT REVENUE	3 Months Ended
	Mar. 31, 2022
REVENUE RECOGNITION
REVENUE RECOGNITION	NOTE 4—PRODUCT REVENUE The Company’s product revenues were generated from sales of DANYELZA and totaled $10,486,000 for three months ended March 31, 2022 and $5,383,000 for the three months ended March 31, 2021. ​ 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 and other sales-related deductions are recorded within accrued liabilities. As of March 31, 2022, the company had recorded accounts receivable allowances of approximately $668,000 and accrued liabilities of $2,921,000 related to product sales during the three months ended March 31, 2022. As of December 31, 2021, the company had recorded accounts receivable allowances of approximately $486,000 and accrued liabilities of $2,615,000 related to product sales. ​ An analysis of the change in reserves for discounts and allowances is summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ ​ ​ ​ Discounts ​ Government Rebates Returns ​ Total ​ (in thousands) Balance, December 31, 2021 $ 13 ​ $ 3,027 ​ $ 61 ​ $ 3,101 Current provisions relating to sales in current year ​ 24 ​ ​ 1,085 ​ ​ 126 ​ ​ 1,235 Payments/credits relating to sales in current year ​ (14) ​ ​ (546) ​ ​ (187) ​ ​ (747) Balance, March 31, 2022 $ 23 ​ $ 3,566 ​ $ — ​ $ 3,589 ​ ​ Substantially all of the Company’s product sales were in the United States. The Company had product sales to certain customers that accounted for more than 10% of total gross product revenue for the three months ended March 31, 2022 and March 31, 2021. Mckesson, AmerisourceBergen, and Cardinal Health accounted for 60%, 25%, and 11%, respectively, of our gross product revenue for the three months ended March 31, 2022. Mckesson and Cardinal Health accounted for 80% and 16%, respectively, of our gross product revenue for the three months ended March 31, 2021.

NET LOSS PER SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2022
NET LOSS PER SHARE
NET LOSS PER SHARE	NOTE 5—NET LOSS 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. Securities that could potentially dilute basic EPS in the future were not included in the computation of diluted EPS because to do so would have been antidilutive. The calculations of basic and diluted net loss per share are as follows (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income /(loss) (numerator) ​ $ (28,068) ​ $ 33,413 ​ Weighted-average shares (denominator), basic ​ 43,709 ​ 41,871 ​ Basic net income / (loss) per share ​ $ (0.64) ​ $ 0.80 ​ Weighted-average shares (denominator), diluted ​ ​ 43,709 ​ ​ 44,384 ​ Diluted net income / (loss) per share ​ $ (0.64) ​ $ 0.75 ​ ​ Potentially dilutive securities excluded from the computation of diluted earnings per share relate to stock options and unvested restricted share units (“RSUs”) outstanding totaled 6,686,168 shares as of March 31, 2022 and 1,177,600 shares as of March 31, 2021.

INVENTORIES

INVENTORIES	3 Months Ended
	Mar. 31, 2022
INVENTORIES
INVENTORIES	NOTE 6—INVENTORIES Inventories consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2022 ​ December 31, 2021 ​ ​ ​ ​ ​ ​ Work In Progress ​ ​ 8,747 ​ ​ 4,741 Finished Goods ​ ​ 541 ​ ​ 771 Total inventories ​ $ 9,288 ​ $ 5,512 ​ ​ ​ ​ ​ ​ ​ Inventories are classified on the Consolidated Balance Sheets in each respective period (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2022 ​ December 31, 2021 CURRENT ASSETS ​ ​ ​ ​ ​ ​ Inventories ​ $ 5,588 ​ $ 5,512 Total recorded in Current Assets ​ ​ 5,588 ​ ​ 5,512 ​ ​ ​ ​ ​ ​ ​ NONCURRENT ASSETS ​ ​ ​ ​ ​ ​ Other assets ​ ​ 3,700 ​ ​ — Total recorded in Noncurrent Assets ​ ​ 3,700 ​ ​ — Total Inventories ​ $ 9,288 ​ $ 5,512 ​ The Company has classified $3,700,000 of work in progress inventory as noncurrent assets based on our current demand schedule and expectation that such inventory will be utilized in excess of one year from the balance sheet date. ​

INTANGIBLE ASSETS

INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2022
INTANGIBLE ASSETS
INTANGIBLE ASSETS	d NOTE 7—INTANGIBLE ASSETS The company’s intangible assets as of March 31, 2022 totaled $1,618,000 and related to capitalized milestone payments made following FDA approval and commercialization of DANYELZA. The intangible asset net book value as of March 31, 2022 is net of $182,000 of accumulated amortization. The company’s intangible assets as of December 31, 2021 totaled $1,663,000. The intangible asset net book value as of December 31, 2021 is net of $137,000 of accumulated amortization. Intangible assets are amortized on a straight-line basis based on a 10 year useful of the assets. Annual amortization expense is expected to $180,000 each year five 2022 2026 ​ ​

ACCRUED LIABILITIES

ACCRUED LIABILITIES	3 Months Ended
	Mar. 31, 2022
ACCRUED LIABILITIES
ACCRUED LIABILITIES	NOTE 8—ACCRUED LIABILITIES Accrued short-term liabilities at March 31, 2022 and December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued licensing, milestone and royalty payments ​ $ 3,768 ​ $ 3,090 Accrued clinical costs ​ 1,533 ​ 915 Accrued compensation and board fees ​ 2,119 ​ 1,877 Accrued manufacturing costs ​ ​ 1,153 ​ ​ 2,622 Accrued sales reserves ​ ​ 2,921 ​ ​ 2,615 Other ​ 1,436 ​ 1,421 Total ​ $ 12,930 ​ $ 12,540 ​

LICENSE AGREEMENTS AND COMMITME

LICENSE AGREEMENTS AND COMMITMENTS	3 Months Ended
	Mar. 31, 2022
LICENSE AGREEMENTS AND COMMITMENTS
LICENSE AGREEMENTS AND COMMITMENTS	NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS As of March 31, 2022, the Company has entered into two license agreements and certain other agreements with Memorial Sloan Kettering Cancer Center (“MSK”). The license agreements, as previously disclosed in our annual report on Form 10-K, are the MSK License and the CD33 License Agreement. In addition, the Company entered into the SADA Technology License Agreement, or the SADA License Agreement, with MSK and Massachusetts Institute of Technology (“MIT”) in 2020. Through a 2019 Settlement and Assumption and Assignment of the MSK License and Y-mAbs Sublicense Agreement (“SAAA”) with MabVax, Inc. (“MabVax”) and MSK, 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. 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 of the payments are contingent milestone and royalty payments, as disclosed in the table below. Amounts disclosed for accrued milestone and royalty payments are inclusive of obligations under the MSK License, CD33 License Agreement, MabVax License Agreement, and SADA License Agreement, collectively. We have the following significant license agreements and related commitments which include all obligations that have been paid or are accrued as of and for the period ending March 31, 2022 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued Accrued Accrued Accrued ​ ​ Cash paid Cash paid Expense Expense liabilities liabilities liabilities liabilities ​ ​ Three months ​ Three months ​ Three months ​ Three months ​ Current ​ Non-current ​ Current ​ Non-current ​ ​ ended ​ ended ​ ended ​ ended ​ as of ​ as of ​ as of ​ as of ​ ​ March ​ March ​ March ​ March ​ March ​ March ​ December ​ December Agreements ​ 2022 ​ 2021 ​ 2022 ​ 2021 ​ 2022 ​ 2022 ​ 2021 ​ 2021 MSK ​ ​ $ - ​ ​ $ 450 ​ ​ $ 677 ​ ​ $ - ​ ​ $ 2,163 ​ ​ $ 1,650 ​ ​ $ 1,486 ​ ​ $ 1,650 CD33 ​ ​ — ​ ​ 100 ​ ​ — ​ ​ — ​ ​ — ​ ​ 450 ​ ​ — ​ ​ 450 MabVax ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — SADA ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,605 ​ ​ — ​ ​ 1,605 ​ ​ — ​ Minimum royalties and certain clinical and regulatory milestones that become due based upon the passage of time under the CD33 License Agreement, the SADA Agreement and the MabVax Agreement are excluded from the above table as the Company does not consider such obligations to be probable. The below table represents the maximum clinical, regulatory or sales-based milestones as reflected within the agreements, certain of which have been paid in prior periods or are accrued as presented in the table above (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maximum Maximum Maximum Agreements ​ Clinical Milestones ​ Regulatory Milestones ​ Sales-based milestones ​ MSK ​ ​ $ 2,450 ​ ​ $ 9,000 ​ ​ $ 20,000 ​ CD33 ​ ​ 550 ​ ​ 500 ​ ​ 7,500 ​ MabVax ​ ​ 200 ​ ​ 1,200 ​ ​ — ​ SADA ​ ​ 4,730 ​ ​ 18,125 ​ ​ 23,750 ​ ​ Research and development is inherently uncertain and as described above, should such research and development fail, the MSK License, the CD 33 License, and the SADA License are cancelable at the Company’s option. The Company will also consider the development risk and each party’s termination rights under the agreements when considering whether any clinical or regulatory based milestone payments, certain of which also contain time-based payment requirements, are deemed probable. The Company records milestones in the period in which the contingent liability is probable and the amount is reasonably estimable. The Company did not have an expense related to milestones under the SADA License Agreement in the first quarters of 2022 and 2021 and had $1,605,000 in accrued liabilities as of March 31, 2022 and 2021. This includes clinical-based milestones of Other agreements We have 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 by 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 we committed to fund certain clinical trials at MSK; two separate core facility service agreements pursuant to which we committed to obtaining certain laboratory services from MSK; and in October 2020 we entered into a SADA sponsored research agreement pursuant to which we 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. For three months ended March 31, 2022 and 2021, we incurred research and development expenses of $697,000 and $948,000, respectively, under these agreements. Lease Agreements In July 2019, the Company entered a development, manufacturing and supply agreement with SpectronRx in South Bend, Indiana, to secure access to clinical and commercial scale radiolabeling capacity for omburtamab. Under the terms of the agreement, SpectronRx has agreed to establish a manufacturing unit designated for the Company within its existing facilities, at which both clinical and commercial supply of radiolabeled omburtamab can be produced. Since the Company possesses the right to substantially all the economic benefits and directs the use of the production area, the Company accounts for the payments related to the access to the manufacturing space under ASC 842 as an operating lease. The term of the lease is two years from the commencement date of August 31, 2020. Upon the lease commencement date, we recorded $3,617,000 as right-of-use asset and $2,680,000 as lease liability with the difference of $937,000 resulting from certain prepayments and other costs incurred. The Company pays equal monthly installments of approximately $117,000 per month in additional access fees through September 2022 resulting in total payments of $583,000 remaining under the agreement. There are no renewal options in this agreement. In February 2019, the Company entered into a lease agreement in connection with its 4,548 square feet laboratory in New Jersey. In December 2019, we expanded the space with an additional 235 square feet. The term of the lease is three years from the date the Company occupied the premises, with an option to extend for an additional two years which the Company expects to exercise and has included in the determination of the related lease liability. This lease will expire in the fourth quarter of 2023. Fixed rent payable under the lease is approximately $144,000 per annum and is payable in equal monthly installments of approximately $12,000. January 2018, the Company entered into a lease agreement in connection with its corporate headquarters in New York. The term of the lease is five years from the date the Company begins to occupy the premises. Fixed rent payable under the lease is approximately $384,000 per annum and is payable in equal monthly installments of approximately $32,000, which are recognized on a straight line basis. The Company entered a three-year lease agreement for the lease of certain office space in Denmark in February 2018, as amended in November 2018 and February 2019. Additionally, on September 26, 2021, the Company entered into a lease agreement in Denmark to expand the size of its current office space to a total of 29,288 square feet. The lease is payable in monthly installments of approximately $41,000, which are recognized on a straight line basis. The new lease is expected to last for 48 months and commenced on November 1, 2021 when we were provided access to the leased space. ​ Total operating lease costs were $704,000 and $646,000 for the three months ended March 31, 2022 and 2021, respectively. During the three months ended March 31, 2022, the expenses were recorded as $638,000 in research and development expense and $66,000 in selling, general, and administrative expense. During the three months ended March 31, 2021, the expenses were recorded as $587,000 in research and development expense and $59,000 in selling, general, and administrative expense. Cash paid for amounts included in the measurement of lease liabilities for the three months ended March 31, 2022 and 2021 was $607,000 and $544,000, respectively, and was included in net cash used in operating activities in the Company’s Consolidated Statements of Cash Flows. ​ Maturities of operating lease liabilities at March 31, 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating Leases ​ at March 31, 2022 Remainder of 2022 ​ $ 1,341 Years ending December 31, ​ ​ ​ 2023 ​ ​ 1,016 2024 ​ ​ 540 2025 ​ ​ 436 Total lease payments ​ ​ 3,333 Less: Imputed interest ​ ​ (284) Total operating lease liabilities at March 31, 2022 ​ $ 3,049 ​ Maturities of operating lease liabilities at December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating Leases Years ending December 31, at December 31, 2021 2022 ​ $ 1,953 2023 ​ ​ 1,025 2024 ​ ​ 550 2025 ​ ​ 445 Total lease payments ​ ​ 3,973 Less: Imputed interest ​ ​ (339) Total operating lease liabilities at December 31, 2021 ​ $ 3,634 ​ 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 uses its estimate of its incremental borrowing rate based on the information available at the lease commencement date. As of March 31, 2022, the weighted average remaining lease term is 2.54 years and the weighted average discount rate used to determine the operating lease liability was 6.5%. As of March 31, 2021, the weighted average remaining lease term is 1.97 years and the weighted average discount rate used to determine the operating lease liability was 7.6%. Legal Matters The Company has been named a nominal defendant in a lawsuit instigated by a stockholder against our Board Member and President, Interim Chief Executive Officer and Head of Business Development and Strategy, Mr. Thomas Gad, seeking 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. 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 had 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.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2022
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 10—STOCKHOLDERS’ EQUITY Authorized Stock As of March 31, 2022 and December 31, 2021, the Company has 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 43,718,165 shares of its common stock as of March 31, 2022 and 43,694,716 shares of its common stock as of December 31, 2021. 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 March 31, 2022 or December 31, 2021. Stock grant agreements with non-employees In April 2020, in connection with the SADA License Agreement, we entered into certain stock grant agreements pursuant to which we agreed to issue a total of 213,996 shares to two non-employee researchers who were involved in the development of the SADA technology licensed from MSK and MIT in consideration for their 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. In accordance with the terms of the agreement, the non-employee researchers vested in an additional 20% of the awards in 2021 and the remaining 40% vesting ratably over the years of 2022 and 2023 on the anniversary date of the agreement. The shares are subject to forfeiture to the extent the SADA License Agreement is terminated prior to the vesting of the shares. There is no cash settlement feature, and no future service is required for the non-employee researchers to vest and receive the shares. While the shares vest over time, there is no performance condition for the shares. In April 2020, we recorded an expense within research and development totaling $7,376,000 related to the shares which represents the fair value of the shares on the grant date. In July 2020, pursuant to the stock grant agreements, we 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 three year Secured Promissory Note. The outstanding principal amounts of the loans, together with all accrued interest thereon at the rate of 1% per annum, is due and payable on the maturity date of the loans. The loans are secured by Pledge and Security Agreements, pursuant to which the researchers have pledged the shares as security for repayment of the loans with interest rates. The loans are classified as held to maturity securities, recorded at amortized cost and included in other assets in the Company’s Consolidated Balance Sheet. Issuance of common stock On February 22, 2021, we completed a third public offering of our common stock pursuant to which we issued and sold 2,804,878 shares of our common stock at a price to the public of $41.00 per share which included the exercise in full of the underwriters’ option to purchase additional shares. We received aggregate gross proceeds from our secondary public offering of $115,000,000, or aggregate net proceeds of approximately $107,725,000 after deducting underwriting discounts and commissions and offering expenses.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2022
SHARE-BASED COMPENSATION
SHARE-BASED COMPENSATION	NOTE 11—SHARE-BASED COMPENSATION 2015 Equity Incentive Plan Our board of directors and stockholders have approved and adopted 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 our 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 our employees, directors and consultants and our parent and subsidiary corporations’ employees and consultants. A total of 4,500,000 shares of our 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 Our board of directors and stockholders approved and adopted the 2018 Plan, which became effective upon the Company’s initial public offering in September 2018 and which provides for the grant of incentive stock options, within the meaning of Section 422 of the Code (the Internal Revenue Code), to our 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 our employees, directors and consultants and our parent and subsidiary corporations’ employees and consultants. A total of 5,500,000 shares of our common stock, inclusive of the awards previously granted under the 2015 Equity Incentive Plan, are 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, equal to 4% of the outstanding shares of common stock as of the last day of our immediately preceding fiscal year. The exercise price of options granted under the plans must at least be equal to the fair market value of our 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 our 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 a four-year period and generally become immediately exercisable upon the occurrence of a change in control, as defined. Stock Option Valuation During the three-month periods ended March 31, 2022 and 2021, there were no new stock options granted. During the three month periods ended in March 31, 2022 and 2021, stock-based compensation for stock option grants were $5,017,000 and $4,629,000, respectively, for options granted to employees and directors. During the three months ended March 31, 2022, the expenses were recorded as $1,779,000 in research and development expense and $3,238,000 in selling, general, and administrative expense. During the three months ended March 31, 2021, the expenses were recorded as $1,692,000 in research and development expense and $2,937,000 in selling, general, and administrative expense. 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, 2021 6,687,128 ​ $ 22.43 ​ $ 26,412 ​ 7.21 Exercised ​ (16,000) ​ ​ 2.00 ​ ​ ​ ​ ​ Forfeited ​ (22,167) ​ ​ 28.67 ​ ​ ​ ​ ​ Outstanding and expected to vest at March 31, 2022 6,648,961 ​ $ 22.46 ​ $ 15,726 ​ 6.96 Exercisable at March 31, 2022 4,083,593 ​ $ 17.23 ​ $ 15,720 ​ 5.78 ​ 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, we estimate our 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 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 our stock options has been determined utilizing the “simplified” method for awards as we have 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 we have never paid cash dividends on shares of our common stock and do 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 period ended March 31, 2022. As of March 31, 2022, we had $44,592,000 of unrecognized compensation related to employee stock options that are expected to vest over a period of 2.79 years. As of March 31, 2021, we had $47,610,000 of unrecognized compensation related to employee stock options that are expected to vest over a period of 2.92 years. Restricted Stock Unit Activity During the three months ended March 31, 2022 and March 31, 2021, stock-based compensation for restricted stock unit grants was $74,000 and $69,000, respectively. During the three months ended March 31, 2022, the expenses were recorded as $68,000 in research and development expense and $6,000 in selling, general, and administrative expense. During the three months ended March 31, 2021, the expenses were recorded as $63,000 in research and development expense and $6,000 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, 2021 ​ 28,907 ​ $ 28.04 1.82 ​ Granted ​ 16,283 ​ ​ 9.31 ​ Vested ​ (7,450) ​ ​ 21.05 ​ ​ Forfeited ​ (534) ​ ​ 28.89 ​ ​ ​ Outstanding and expected to vest at March 31, 2022 ​ 37,206 ​ $ 20.74 2.38 ​ ​ As of March 31, 2022, we had $650,000 of unrecognized compensation related to employee restricted stock units that are expected to vest over a period of 2.38 years. As of March 31, 2021, we had $523,000 of unrecognized compensation related to employee restricted stock units that are expected to vest over a period of 1.96 years.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2022
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	NOTE 12—RELATED PARTY TRANSACTIONS Under the MSK License Agreement, SADA License Agreement, the CD33 License Agreement, MabVax Agreement, and various other supporting agreements with MSK, we have expensed costs in the total amount of $1,374,000 and $948,000 in the three months ended March 31, 2022 and 2021, respectively, for milestones, and research and development costs, under these agreements with MSK. Please refer to NOTE 9—LICENSE AGREEMENTS AND COMMITMENTS

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2022
INCOME TAXES
INCOME TAXES	NOTE 13—INCOME TAXES The Company provided no current and deferred income taxes on net loss of $28,068,000 and net income of $33,413,000 for the three-month periods ended March 31, 2022 and 2021, respectively. 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. Unrecognized tax benefits were $0 and $304,000 at March 31, 2022 and December 31, 2021, respectively. As of March 31, 2022 and December 31, 2021, the Company does not have any interest or penalties accrued related to the total amount of unrecognized tax benefits. The Company’s tax returns for the years 2020, 2019, 2018, and 2017 are open for tax examination by U.S. federal and state and 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 no material impacts to our income tax accounts. The Company maintains a full valuation allowance on its 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 its evaluation, the Company considered its 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 its U.S. and foreign deferred tax assets will be maintained. The Company will continue to assess the realizability of its deferred tax assets and will adjust the valuation allowance as needed.

OTHER BENEFITS

OTHER BENEFITS	3 Months Ended
	Mar. 31, 2022
OTHER BENEFITS
OTHER BENEFITS	NOTE 14—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 during the three months ended March 31, 2022 and 2021. The Company has established a retirement program for employees of our 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 three months ended March 31, 2022 and 2021. In addition, health insurance benefits for our Danish employees are fully paid for by such employees. Our Danish subsidiary does not incur any costs for these health insurance benefits. ​

GAIN FROM SALE OF PRIORITY REVI

GAIN FROM SALE OF PRIORITY REVIEW VOUCHER	3 Months Ended
	Mar. 31, 2022
GAIN FROM SALE OF PRIORITY REVIEW VOUCHER
GAIN FROM SALE OF PRIORITY REVIEW VOUCHER	NOTE 15 GAIN FROM SALE OF PRIORITY REVIEW VOUCHER On December 28, 2020, the Company announced that it entered into a definitive agreement to sell its DANYELZA Priority Review Voucher, or PRV, to United Therapeutics Corporation for $105,000,000. The PRV was granted in conjunction with the approval by FDA of DANYELZA, for the treatment of refractory/relapsed high-risk neuroblastoma. Under the terms of the Company’s license agreement with MSK, Y-mAbs retained 60% of the net proceeds received from the sale, and the remaining 40% was paid to MSK. The transaction closed on January 21, 2021 once the substantive closing conditions included within the agreement were resolved. The Company recognized a net gain of $62,010,000 during the quarter ended March 31, 2021 related to the sale. The Company did not recognize a corresponding gain during the quarter ended March 31, 2022. ​

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2022
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	​ NOTE 16 SUBSEQUENT EVENT On April 27, 2022, the Company announced certain executive management changes. Effective April 22, 2022, Dr. Claus Møller 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 the Company’s operations, policies or practices. Dr. Møller’s employment agreement provides for cash compensation of $1,428,000 , which includes salary and certain benefits continuation. 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 will result in a non-cash share-based compensation expense charge of ​

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2022
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
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 any losses on its cash and cash equivalents. The carrying amount of cash and cash equivalents approximates its fair value due to its short-term and liquid nature. We maintain 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. We do not anticipate any losses with respect to such cash balances.
Trade Accounts Receivables	Trade Accounts Receivables The Company’s trade accounts receivable 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 account 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 our customers and has not recognized any allowance for doubtful accounts nor reversed any allowances in the three months ended March 31, 2022.
Concentration of Credit Risk	Concentration of Credit Risk The Company product sales are made through arrangements primarily with three national speciality distributors in the United States of America. As of March 31, 2022, the receivables balances from such distributors totaled 94% of our outstanding accounts receivable. The Company has contractual payment terms with each of its customers and the Company monitors their financial performance, historical payment terms and credit worthiness to timely assess and respond to any changes in their credit profile.
Inventory	Inventory The Company values its 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. Prior to FDA approval, the Company expensed such costs as part of research and development expenses. 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. No material inventory write-downs occurred in the three months ended March 31, 2022.
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 its cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at March 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 Total ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2021 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729 Total ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729 ​ During the quarter ended March 31, 2022, there were no transfers Level 3 Operating Leases 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 its 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 its estimated incremental borrowing rate based on information available at the lease commencement date. Because most of the Company’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 it 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 the lease which are included in the lease term when it is reasonably certain that it 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, we will not recognize right-of-use assets or liabilities, and this includes not recognizing right-of-use assets or liabilities for existing short-term leases of those assets in transition. We also elect 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
Operating Leases	Operating Leases 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 its 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 its estimated incremental borrowing rate based on information available at the lease commencement date. Because most of the Company’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 it 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 the lease which are included in the lease term when it is reasonably certain that it 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, we will not recognize right-of-use assets or liabilities, and this includes not recognizing right-of-use assets or liabilities for existing short-term leases of those assets in transition. We also elect 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
Use of Estimates	Use of Estimates The preparation of 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 financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these 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, and the valuation of stock options. 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. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including expenses, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international markets.
Revenue Recognition	Revenue Recognition - Product revenue We recognize revenue from sales of DANYELZA at a point in time when our customer is deemed to have obtained control of the product, which generally occurs upon receipt at the end-user hospital. ​ The amount of revenue we recognize 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, we estimate, utilizing the expected value method, the amount of revenue that we 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 we review these estimates quarterly. If actual results vary from our original estimates, we will adjust these estimates quarterly, which would affect net product revenue and earnings in the period such variances occur. ​ ● Rebates and chargebacks ​ We contract with United States governmental agencies to ensure that DANYELZA will be eligible for coverage under the various programs administered by the agencies. We estimate the rebates and chargebacks to be provided and deduct these estimated amounts from our 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. We develop 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. Our liability for these rebates and chargebacks mainly consists of claims for which invoices have not yet been received and paid. We do not maintain material levels of inventory in the wholesale or retail channel. ​ ● Discounts and distribution-related fees ​ We provide invoice discounts on DANYELZA sales to our 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, we expect our distributors to earn these discounts and fees and deduct the full amount of these discounts and fees from our gross product revenue at the time such revenues are recognized. ​ ● Returns ​ We offer our customers limited product return rights for damaged, defective, or expiring products. We estimate 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 an establishment of an accrued liability. ​
Segment Information	Segment Information The Company is engaged solely in the discovery, development, distribution and commercialization of novel antibody-based therapeutic products for the treatment of cancer. Accordingly, the Company has determined that it operates in one operating segment.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements – Adopted 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 2020-10, ASU 2021-04 and ASU 2020-06 effective January 1, 2022, and the adoption of these new standards did not have a material impact on the Company’s consolidated financial statements or disclosures. The Company has evaluated accounting pronouncements recently issued but not yet adopted and believes that these pronouncements do not apply to the Company’s operations and therefore 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)	3 Months Ended
	Mar. 31, 2022
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 its cash equivalents, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at March 31, 2022 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 Total ​ $ — ​ $ 141,739 ​ $ — ​ $ 141,739 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2021 Using: ​ Level 1 Level 2 Level 3 Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729 Total ​ $ — ​ $ 166,729 ​ $ — ​ $ 166,729

PRODUCT REVENUE (Tables)

PRODUCT REVENUE (Tables)	3 Months Ended
	Mar. 31, 2022
REVENUE RECOGNITION
Change in reserves for discounts and allowances	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ ​ ​ ​ Discounts ​ Government Rebates Returns ​ Total ​ (in thousands) Balance, December 31, 2021 $ 13 ​ $ 3,027 ​ $ 61 ​ $ 3,101 Current provisions relating to sales in current year ​ 24 ​ ​ 1,085 ​ ​ 126 ​ ​ 1,235 Payments/credits relating to sales in current year ​ (14) ​ ​ (546) ​ ​ (187) ​ ​ (747) Balance, March 31, 2022 $ 23 ​ $ 3,566 ​ $ — ​ $ 3,589

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2022
NET LOSS PER SHARE
Schedule of basic and diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income /(loss) (numerator) ​ $ (28,068) ​ $ 33,413 ​ Weighted-average shares (denominator), basic ​ 43,709 ​ 41,871 ​ Basic net income / (loss) per share ​ $ (0.64) ​ $ 0.80 ​ Weighted-average shares (denominator), diluted ​ ​ 43,709 ​ ​ 44,384 ​ Diluted net income / (loss) per share ​ $ (0.64) ​ $ 0.75 ​

INVENTORIES (Tables)

INVENTORIES (Tables)	3 Months Ended
	Mar. 31, 2022
INVENTORIES
Schedule of inventories	Inventories consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2022 ​ December 31, 2021 ​ ​ ​ ​ ​ ​ Work In Progress ​ ​ 8,747 ​ ​ 4,741 Finished Goods ​ ​ 541 ​ ​ 771 Total inventories ​ $ 9,288 ​ $ 5,512 ​ ​ ​ ​ ​ ​ ​ Inventories are classified on the Consolidated Balance Sheets in each respective period (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2022 ​ December 31, 2021 CURRENT ASSETS ​ ​ ​ ​ ​ ​ Inventories ​ $ 5,588 ​ $ 5,512 Total recorded in Current Assets ​ ​ 5,588 ​ ​ 5,512 ​ ​ ​ ​ ​ ​ ​ NONCURRENT ASSETS ​ ​ ​ ​ ​ ​ Other assets ​ ​ 3,700 ​ ​ — Total recorded in Noncurrent Assets ​ ​ 3,700 ​ ​ — Total Inventories ​ $ 9,288 ​ $ 5,512

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2022
ACCRUED LIABILITIES
Summary of accrued short-term liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued licensing, milestone and royalty payments ​ $ 3,768 ​ $ 3,090 Accrued clinical costs ​ 1,533 ​ 915 Accrued compensation and board fees ​ 2,119 ​ 1,877 Accrued manufacturing costs ​ ​ 1,153 ​ ​ 2,622 Accrued sales reserves ​ ​ 2,921 ​ ​ 2,615 Other ​ 1,436 ​ 1,421 Total ​ $ 12,930 ​ $ 12,540

LICENSE AGREEMENTS AND COMMIT_2

LICENSE AGREEMENTS AND COMMITMENTS (Tables)	3 Months Ended
	Mar. 31, 2022
LICENSE AGREEMENTS AND COMMITMENTS
Summary of significant license agreements, related commitments and milestone information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued Accrued Accrued Accrued ​ ​ Cash paid Cash paid Expense Expense liabilities liabilities liabilities liabilities ​ ​ Three months ​ Three months ​ Three months ​ Three months ​ Current ​ Non-current ​ Current ​ Non-current ​ ​ ended ​ ended ​ ended ​ ended ​ as of ​ as of ​ as of ​ as of ​ ​ March ​ March ​ March ​ March ​ March ​ March ​ December ​ December Agreements ​ 2022 ​ 2021 ​ 2022 ​ 2021 ​ 2022 ​ 2022 ​ 2021 ​ 2021 MSK ​ ​ $ - ​ ​ $ 450 ​ ​ $ 677 ​ ​ $ - ​ ​ $ 2,163 ​ ​ $ 1,650 ​ ​ $ 1,486 ​ ​ $ 1,650 CD33 ​ ​ — ​ ​ 100 ​ ​ — ​ ​ — ​ ​ — ​ ​ 450 ​ ​ — ​ ​ 450 MabVax ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — SADA ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,605 ​ ​ — ​ ​ 1,605 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maximum Maximum Maximum Agreements ​ Clinical Milestones ​ Regulatory Milestones ​ Sales-based milestones ​ MSK ​ ​ $ 2,450 ​ ​ $ 9,000 ​ ​ $ 20,000 ​ CD33 ​ ​ 550 ​ ​ 500 ​ ​ 7,500 ​ MabVax ​ ​ 200 ​ ​ 1,200 ​ ​ — ​ SADA ​ ​ 4,730 ​ ​ 18,125 ​ ​ 23,750 ​
Maturities of operating lease liabilities	Maturities of operating lease liabilities at March 31, 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating Leases ​ at March 31, 2022 Remainder of 2022 ​ $ 1,341 Years ending December 31, ​ ​ ​ 2023 ​ ​ 1,016 2024 ​ ​ 540 2025 ​ ​ 436 Total lease payments ​ ​ 3,333 Less: Imputed interest ​ ​ (284) Total operating lease liabilities at March 31, 2022 ​ $ 3,049 ​ Maturities of operating lease liabilities at December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating Leases Years ending December 31, at December 31, 2021 2022 ​ $ 1,953 2023 ​ ​ 1,025 2024 ​ ​ 550 2025 ​ ​ 445 Total lease payments ​ ​ 3,973 Less: Imputed interest ​ ​ (339) Total operating lease liabilities at December 31, 2021 ​ $ 3,634

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2022
SHARE-BASED COMPENSATION
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, 2021 6,687,128 ​ $ 22.43 ​ $ 26,412 ​ 7.21 Exercised ​ (16,000) ​ ​ 2.00 ​ ​ ​ ​ ​ Forfeited ​ (22,167) ​ ​ 28.67 ​ ​ ​ ​ ​ Outstanding and expected to vest at March 31, 2022 6,648,961 ​ $ 22.46 ​ $ 15,726 ​ 6.96 Exercisable at March 31, 2022 4,083,593 ​ $ 17.23 ​ $ 15,720 ​ 5.78
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, 2021 ​ 28,907 ​ $ 28.04 1.82 ​ Granted ​ 16,283 ​ ​ 9.31 ​ Vested ​ (7,450) ​ ​ 21.05 ​ ​ Forfeited ​ (534) ​ ​ 28.89 ​ ​ ​ Outstanding and expected to vest at March 31, 2022 ​ 37,206 ​ $ 20.74 2.38 ​

BASIS OF PRESENTATION - Accumul

BASIS OF PRESENTATION - Accumulated deficit (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
BASIS OF PRESENTATION
Accumulated deficit	$ (368,543)	$ (340,475)

BASIS OF PRESENTATION - Seconda

BASIS OF PRESENTATION - Secondary public offering (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 22, 2021	Mar. 31, 2021
Common Stock
Issuance of stock
Issuance of common stock, Stock offering (in shares)		2,804,878
Secondary public offering, February 22, 2021
Issuance of stock
Aggregate gross proceeds	$ 115
Secondary public offering, February 22, 2021 | Common Stock
Issuance of stock
Issuance of common stock, Stock offering (in shares)	2,804,878
Share price (in dollars per share)	$ 41
Secondary public offering, February 22, 2021, Underwriters' option | Common Stock
Issuance of stock
Issuance of common stock, Stock offering (in shares)	365,853

BASIS OF PRESENTATION - Cash an

BASIS OF PRESENTATION - Cash and cash equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
BASIS OF PRESENTATION
Cash and cash equivalents	$ 156,724	$ 181,564

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details) - Credit Concentration Risk - Accounts Receivable - Three Customers	3 Months Ended
	Mar. 31, 2022customer
Concentration risk
Number of customers	3
Concentration risk percentage (as a percent)	94.00%

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value Measurement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Fair value measurements
Level 1 to Level 2 Transfers	$ 0
Level 2 to Level 1 Transfers	0
Transfers into Level 3	0
Transfers out of Level 3	0
Recurring
Fair value measurements
Cash equivalents	141,739	$ 166,729
Recurring | Money market funds
Fair value measurements
Cash equivalents	141,739	166,729
Recurring | Level 2
Fair value measurements
Cash equivalents	141,739	166,729
Recurring | Level 2 | Money market funds
Fair value measurements
Cash equivalents	$ 141,739	$ 166,729

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Operating Leases (Details) $ in Millions	Mar. 31, 2022USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Residual value guarantees	$ 0

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue and Segment (Details)	3 Months Ended
	Mar. 31, 2022segment
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Discount for prompt payment (as a percent)	2.00%
Number of operating segments	1

PRODUCT REVENUE - Discounts and

PRODUCT REVENUE - Discounts and Allowances (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenue
Revenue	$ 10,486	$ 5,383
Change in reserves for discounts and allowances
Discounts, Balance at beginning of period	13
Discounts, Current provisions relating to sales in current year	24
Discounts, Payments/credits relating to sales in current year	(14)
Discounts, Balance at end of period	23
Contractual Allowances and Government Rebates, Balance at beginning of period	3,027
Contractual Allowances and Government Rebates, Current provisions relating to sales in current year	1,085
Contractual Allowances and Government Rebates, Payments/credits relating to sales in current year	(546)
Contractual Allowances and Government Rebates, Balance at end of period	3,566
Returns, Balance at beginning of period	61
Returns, Current provisions relating to sales in current year	126
Returns, Payments/credits relating to sales in current year	(187)
Reserves for discounts and allowances, Balance at beginning of period	3,101
Reserves for discounts and allowances, Current provisions relating to sales in current year	1,235
Reserves for discounts and allowances, Payments/credits relating to sales in current year	(747)
Reserves for discounts and allowances, Balance at end of period	3,589
Accounts receivable
Change in reserves for discounts and allowances
Reserves for discounts and allowances, Balance at beginning of period	486
Reserves for discounts and allowances, Balance at end of period	668
Accrued liabilities
Change in reserves for discounts and allowances
Reserves for discounts and allowances, Balance at beginning of period	2,615
Reserves for discounts and allowances, Balance at end of period	2,921
Product, DANYELZA
Revenue
Revenue	$ 10,486

PRODUCT REVENUE - Concentration

PRODUCT REVENUE - Concentrations (Details) - Customer Concentration Risk - Revenue - Product	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
McKesson
Concentration risk
Concentration risk percentage (as a percent)	60.00%	80.00%
AmerisourceBergen
Concentration risk
Concentration risk percentage (as a percent)	25.00%
Cardinal Health
Concentration risk
Concentration risk percentage (as a percent)	11.00%	16.00%

NET LOSS PER SHARE - Basic and

NET LOSS PER SHARE - Basic and diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
NET LOSS PER SHARE
Net income /(loss) (numerator), Basic (in dollars)	$ (28,068)	$ 33,413
Net income /(loss) (numerator), Diluted (in dollars)	$ (28,068)	$ 33,413
Weighted-average shares (denominator), basic (in dollars per share)	43,709,238	41,870,759
Basic net income / (loss) per share (in dollars per share)	$ (0.64)	$ 0.80
Weighted-average shares (denominator), diluted (in dollars per share)	43,709,238	44,383,791
Diluted net income / (loss) per share (in dollars per share)	$ (0.64)	$ 0.75

NET LOSS PER SHARE - Anti-dilut

NET LOSS PER SHARE - Anti-dilutive securities (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
NET LOSS PER SHARE
Potentially dilutive securities outstanding	6,686,168	1,177,600

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Inventories
Work in Process	$ 8,747	$ 4,741
Finished Goods	541	771
Total inventories	9,288	5,512
CURRENT ASSETS
Inventories, Current	5,588	$ 5,512
NONCURRENT ASSETS
Inventories, Noncurrent	3,700
Other long-term assets
NONCURRENT ASSETS
Inventories, Noncurrent	$ 3,700

INTANGIBLE ASSETS (Details)

INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
INTANGIBLE ASSETS
Intangible assets, net	$ 1,618	$ 1,663
Accumulated amortization	$ 182	$ 137
Amortization period	10 years
Forecasted amortization expense
2022	$ 180
2023	180
2024	180
2025	180
2026	$ 180

ACCRUED LIABILITIES (Details)

ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued short-term liabilities
Accrued licensing, milestone and royalty payments	$ 3,768	$ 3,090
Accrued clinical costs	1,533	915
Accrued compensation and board fees	2,119	1,877
Accrued manufacturing costs	1,153	2,622
Accrued sales reserves	2,921	2,615
Other	1,436	1,421
Total	$ 12,930	$ 12,540

LICENSE AGREEMENTS AND COMMIT_3

LICENSE AGREEMENTS AND COMMITMENTS - License Agreements (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)agreement	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)
Financial statement information
Accrued liabilities, current	$ 12,930		$ 12,540
Accrued liabilities, noncurrent	2,100		2,100
Gross intangible assets related to Danyelza	$ 1,618		1,663
MSK
Agreements
Number of license agreements | agreement	2
MSK License Agreement
Financial statement information
Cash paid		$ 450
Expense	$ 677
Accrued liabilities, current	2,163		1,486
Accrued liabilities, noncurrent	1,650		1,650
Milestones
Maximum Clinical Milestones	2,450
Maximum Regulatory Milestones	9,000
Maximums Sales-based Milestones	20,000
CD33 License Agreement
Financial statement information
Cash paid		100
Accrued liabilities, noncurrent	450		450
Milestones
Maximum Clinical Milestones	550
Maximum Regulatory Milestones	500
Maximums Sales-based Milestones	7,500
MabVax Agreement
Milestones
Maximum Clinical Milestones	200
Maximum Regulatory Milestones	1,200
SADA License Agreement
Financial statement information
Accrued liabilities, current	1,605	$ 1,605	$ 1,605
Milestones
Maximum Clinical Milestones	4,730
Maximum Regulatory Milestones	18,125
Maximums Sales-based Milestones	23,750
Accrued liabilities, current - Clinical-based milestones	$ 605
Period for which all time-based milestones coming due have been accrued	36 months

LICENSE AGREEMENTS AND COMMIT_4

LICENSE AGREEMENTS AND COMMITMENTS - Other agreements (Details) - USD ($)	1 Months Ended	3 Months Ended
	Oct. 31, 2020	Mar. 31, 2022	Mar. 31, 2021
Agreements
Research and development		$ 22,912,000	$ 21,579,000
Other Agreements with MSK
Agreements
Research and development		$ 697,000	$ 948,000
Core Facility Service Agreements
Agreements
Number of service agreements		2
Sponsored Research Agreement
Agreements
Research service period	3 years
Researchers, Employees of MSK | Master Data Services Agreement
Agreements
Number of individuals		5

LICENSE AGREEMENTS AND COMMIT_5

LICENSE AGREEMENTS AND COMMITMENTS - Lease agreements (Details) $ in Thousands	1 Months Ended
	Aug. 31, 2020USD ($)	Feb. 28, 2019USD ($)ft²	Mar. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Nov. 01, 2021USD ($)ft²	Dec. 31, 2019ft²	Feb. 28, 2018	Jan. 31, 2018USD ($)
Leases
Operating lease right-of-use assets			$ 3,155	$ 3,842
Lease liabilities			$ 3,049	$ 3,634
Manufacturing facility, Indiana
Leases
Lease term	2 years
Operating lease right-of-use assets	$ 3,617
Lease liabilities	2,680
Difference between right of use asset and lease liability recognized	937
Access fee monthly installment	117
Amount of additional access fees to be paid in monthly installments	$ 583
Option to extend	false
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		$ 144
Lease payable per month		$ 12
Corporate headquarters, New York
Leases
Lease term								5 years
Fixed rent payable per annum								$ 384
Lease payable per month								$ 32
Office space, Denmark
Leases
Leased area (in square feet) | ft²					29,288
Lease term					48 months		3 years
Lease payable per month					$ 41

LICENSE AGREEMENTS AND COMMIT_6

LICENSE AGREEMENTS AND COMMITMENTS - Lease costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Leases
Total operating lease costs	$ 704	$ 646
Cash paid for amounts included in the measurement of lease liabilities	607	544
Research and development expense
Leases
Total operating lease costs	638	587
Selling, general, and administrative expense
Leases
Total operating lease costs	$ 66	$ 59

LICENSE AGREEMENTS AND COMMIT_7

LICENSE AGREEMENTS AND COMMITMENTS - Lease maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Future minimum commitments under all non-cancelable operating leases
Remainder of year	$ 1,341
First fiscal year	1,016	$ 1,953
Second fiscal year	540	1,025
Third fiscal year	436	550
Fourth fiscal year		445
Total lease payments	3,333	3,973
Less: Imputed interest	(284)	(339)
Total operating lease liabilities at end of period	$ 3,049	$ 3,634

LICENSE AGREEMENTS AND COMMIT_8

LICENSE AGREEMENTS AND COMMITMENTS - Lease term and discount rate (Details)	Mar. 31, 2022	Mar. 31, 2021
LICENSE AGREEMENTS AND COMMITMENTS
Weighted average remaining lease term	2 years 6 months 14 days	1 year 11 months 19 days
Weighted average discount rate	6.50%	7.60%

STOCKHOLDERS' EQUITY - Authoriz

STOCKHOLDERS' EQUITY - Authorized, Common and Preferred Stock (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2022USD ($)Vote$ / sharesshares	Dec. 31, 2021USD ($)Vote$ / sharesshares
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	43,718,165	43,694,716
Preferred stock, shares issued	0	0

STOCKHOLDERS' EQUITY - Stock gr

STOCKHOLDERS' EQUITY - Stock grant agreements with non-employees (Details) - SADA License Agreement - Researchers, Employees of MSK $ in Thousands	1 Months Ended		12 Months Ended
	Jul. 31, 2020USD ($)individual	Apr. 30, 2020USD ($)individualshares	Dec. 31, 2021
Share-Based Compensation Awards
Number of individuals | individual	2
Notes receivable, noncurrent | $	$ 2,610
Notes receivable term	3 years
Notes receivable interest rate (as a percent)	1.00%
Nonemployees
Share-Based Compensation Awards
Number of individuals | individual		2
Nonemployees | Research and development expense
Share-Based Compensation Awards
Non-cash expense in connection with equity issuance to inventors | $		$ 7,376
Nonemployees | Tranche one
Share-Based Compensation Awards
Vesting (as a percent)		40.00%
Nonemployees | Tranche two
Share-Based Compensation Awards
Vesting (as a percent)		60.00%	20.00%
Remaining vesting percentage			40.00%
Vesting period		3 years
Common Stock | Nonemployees
Share-Based Compensation Awards
Shares agreed to be issued | shares		213,996
Issuance of common stock to non-employees (in shares) | shares		213,996

STOCKHOLDERS' EQUITY - Issuance

STOCKHOLDERS' EQUITY - Issuance of common stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 22, 2021	Mar. 31, 2021
Issuance of stock
Proceeds from issuance of common stock, net		$ 107,725
Secondary public offering, February 22, 2021
Issuance of stock
Aggregate gross proceeds	$ 115,000
Common Stock
Issuance of stock
Issuance of common stock, Stock offering (in shares)		2,804,878
Common Stock | Secondary public offering, February 22, 2021
Issuance of stock
Issuance of common stock, Stock offering (in shares)	2,804,878
Share price (in dollars per share)	$ 41
Proceeds from issuance of common stock, net	$ 107,725

SHARE-BASED COMPENSATION - 2015

SHARE-BASED COMPENSATION - 2015 Plan (Details) - 2015 Plan - shares	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2018
Share-Based Compensation Awards
Shares reserved for issuance pursuant to the plan	4,500,000
Shares available for grant		0
Stock options
Share-Based Compensation Awards
Vesting period	4 years

SHARE-BASED COMPENSATION - 2018

SHARE-BASED COMPENSATION - 2018 Plan (Details) - 2018 Plan	3 Months Ended
	Mar. 31, 2022shares
Share-Based Compensation Awards
Shares reserved for issuance pursuant to the plan	5,500,000
Annual increase on share reserve (as a percent)	4.00%
Stock options | Employees and nonemployees owning less than 10% of voting power
Share-Based Compensation Awards
Term of award	10 years
Vesting period	4 years
Stock options | Participants owning more than 10% of voting power
Share-Based Compensation Awards
Term of award	5 years
Stock options | Participants owning more than 10% of voting power | Minimum
Share-Based Compensation Awards
Ownership (as a percent)	10.00%
Option price as percentage of fair market value of common stock on the date of grant	110.00%

SHARE-BASED COMPENSATION - Stoc

SHARE-BASED COMPENSATION - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-Based Compensation Awards
Granted (in shares)	0	0
Stock options | Employees and directors
Share-Based Compensation Awards
Stock-based compensation expenses	$ 5,017	$ 4,629
Stock options | Employees and directors | Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	1,779	1,692
Stock options | Employees and directors | Selling, general, and administrative
Share-Based Compensation Awards
Stock-based compensation expenses	3,238	2,937
RSUs
Share-Based Compensation Awards
Stock-based compensation expenses	74	69
RSUs | Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	68	63
RSUs | Selling, general, and administrative
Share-Based Compensation Awards
Stock-based compensation expenses	$ 6	$ 6

SHARE-BASED COMPENSATION - St_2

SHARE-BASED COMPENSATION - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Options
Outstanding at beginning of period (in shares)	6,687,128
Exercised (in shares)	(16,000)
Forfeited, shares (in shares)	(22,167)
Outstanding at end of period (in shares)	6,648,961	6,687,128
Exercisable at end of period (in shares)	4,083,593
Weighted average exercise price
Outstanding at beginning of period (in dollars per share)	$ 22.43
Exercised (in dollars per share)	2
Forfeited (in dollars per share)	28.67
Outstanding at end of period (in dollars per share)	22.46	$ 22.43
Exercisable at end of period (in dollars per share)	$ 17.23
Aggregate intrinsic value and Weighted average remaining contractual life (years)
Outstanding (in dollars)	$ 15,726	$ 26,412
Exercisable (in dollars)	$ 15,720
Outstanding (in years)	6 years 11 months 15 days	7 years 2 months 15 days
Exercisable (in years)	5 years 9 months 10 days

SHARE-BASED COMPENSATION - St_3

SHARE-BASED COMPENSATION - Stock option unrecognized compensation (Details) - Stock options - Employees - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Unrecognized compensation related to employee stock options
Unrecognized compensation	$ 44,592	$ 47,610
Expected vesting period	2 years 9 months 14 days	2 years 11 months 1 day

SHARE-BASED COMPENSATION - Rest

SHARE-BASED COMPENSATION - Restricted Stock Unit Activity (Details) - RSUs - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Restricted stock units issued and outstanding
Outstanding and expected to vest at beginning of period (in shares)	28,907
Granted (in shares)	16,283
Vested (in shares)	(7,450)
Forfeited (in shares)	(534)
Outstanding and expected to vest at end of period (in shares)	37,206		28,907
Weighted average grant price
Weighted average grant price, Outstanding and expected to vest, Beginning of period (in dollars per share)	$ 28.04
Weighted average grant price, Granted (in dollars per share)	9.31
Weighted average grant price, Vested (in dollars per share)	21.05
Weighted average grant price, Forfeited (in dollars per share)	28.89
Weighted average grant price, Outstanding and expected to vest, End of period (in dollars per share)	$ 20.74		$ 28.04
Unrecognized compensation	$ 650	$ 523
Weighted average remaining vesting life	2 years 4 months 17 days	1 year 11 months 15 days	1 year 9 months 25 days

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - Shareholder, MSK - MSK License Agreement, SADA License Agreement, CD33 License Agreement, MabVax Agreement, and other supporting agreements with MSK - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Related party transactions
Expensed costs	$ 1,374	$ 948
Due to related parties	6,455		$ 6,191
Due to related parties, Accounts payable	335		748
Due to related parties, Accrued liabilities	$ 6,120		$ 5,443

INCOME TAXES - Loss before inco

INCOME TAXES - Loss before income taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income tax expense
Provision for (benefit from) income tax	$ 0	$ 0
Domestic and foreign loss before income taxes:
Losses before taxes	$ 28,068	$ (33,413)

INCOME TAXES - Uncertain tax po

INCOME TAXES - Uncertain tax positions (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
INCOME TAXES
Unrecognized tax benefits	$ 0	$ 304
Interest or penalties accrued related to unrecognized tax benefits	$ 0	$ 0

OTHER BENEFITS (Details)

OTHER BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
UNITED STATES
Benefit plan
Employer matching contribution to defined contribution plan (as a percent)	0.00%	0.00%
DENMARK
Benefit plan
Employer matching contribution to defined contribution plan (as a percent)	0.00%	0.00%
Costs for employee health insurance benefits	$ 0

GAIN FROM SALE OF PRIORITY RE_2

GAIN FROM SALE OF PRIORITY REVIEW VOUCHER (Details) - USD ($) $ in Thousands	Jan. 21, 2021	Mar. 31, 2022	Mar. 31, 2021
Disposal
Net gain recognized			$ 62,010
Priority Review Voucher | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposal
Consideration	$ 105,000
Percentage of net proceeds from monetization entitled to be retained	60.00%
Percentage of net proceeds from monetization to be paid to MSK	40.00%
Net gain recognized		$ 0	$ 62,010

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event - Chief Executive Officer, Dr. Claus Moller $ in Thousands	Apr. 27, 2022USS ($)
Subsequent Events
Cash compensation for salary and certain benefits continuation	$ 1,428
Non-cash share-based compensation expense	9,286
Total charge related to executive management change to be recorded during 2022	$ 10,714