Y-mAbs Therapeutics (YMAB) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 05, 2020
Document and Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity Registrant Name	Y-mAbs Therapeutics, Inc.
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		39,757,623
Entity Central Index Key	0001722964
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 185,774	$ 207,136
Other current assets	4,062	4,819
Total current assets	189,836	211,955
Property and equipment, net	1,992	2,052
Operating lease right-of-use assets	1,865	1,989
Other assets	381	370
TOTAL ASSETS	194,074	216,366
LIABILITIES
Accounts payable	10,260	8,520
Accrued liabilities	4,035	4,550
Operating lease liabilities, current portion	548	516
Total current liabilities	14,843	13,586
Accrued milestone and royalty payments	1,901	1,921
Operating lease liabilities, long-term portion	1,543	1,714
Other liabilities	457	242
TOTAL LIABILITIES	18,744	17,463
Commitments and contingencies (Note 6)
STOCKHOLDERS? EQUITY
Preferred stock, $0.0001 par value, 5,500,000 shares authorized at March 31, 2020 and December 31, 2019; none issued at March 31, 2020 and December 31, 2019
Common stock, $0.0001 par value, 100,000,000 shares authorized at March 31, 2020 and December 31, 2019; 39,757,623 and 39,728,416 shares issued at March 31, 2020 and December 31, 2019, respectively	4	4
Additional paid in capital	367,293	364,712
Accumulated other comprehensive income	75	50
Accumulated deficit	(192,042)	(165,863)
TOTAL STOCKHOLDERS' EQUITY	175,330	198,903
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 194,074	$ 216,366

Consolidated Balance Sheets (pa

Consolidated Balance Sheets (parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
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	39,757,623	39,728,416

Consolidated Statements of Net

Consolidated Statements of Net Loss and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING EXPENSES
Research and development	$ 18,622	$ 12,511
General and administrative	8,125	3,742
Total operating expenses	26,747	16,253
Loss from operations	(26,747)	(16,253)
OTHER INCOME, NET
Interest and other income, net	568	319
NET LOSS	(26,179)	(15,934)
Other comprehensive income
Foreign currency translation	25	56
COMPREHENSIVE LOSS	$ (26,154)	$ (15,878)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.66)	$ (0.47)
Weighted average common shares outstanding, basic and diluted	39,753,583	34,193,666

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, 2018	$ 3	$ 225,352	$ 7	$ (84,835)	$ 140,527
Balance at the beginning of period (in shares) at Dec. 31, 2018	34,193,666
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense		864			864
Foreign currency translation			56		56
Net loss				(15,934)	(15,934)
Balance at the end of period at Mar. 31, 2019	$ 3	226,216	63	(100,769)	125,513
Balance at the end of period (in shares) at Mar. 31, 2019	34,193,666
Balance at the beginning of period at Dec. 31, 2018	$ 3	225,352	7	(84,835)	140,527
Balance at the beginning of period (in shares) at Dec. 31, 2018	34,193,666
Balance at the end of period at Dec. 31, 2019	$ 4	364,712	50	(165,863)	198,903
Balance at the end of period (in shares) at Dec. 31, 2019	39,728,416
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		370			$ 370
Exercise of stock options (in shares)	25,778				25,778
Stock-based compensation expense		2,211			$ 2,211
Stock-based compensation expense (in shares)	3,429
Foreign currency translation			25		25
Net loss				(26,179)	(26,179)
Balance at the end of period at Mar. 31, 2020	$ 4	$ 367,293	$ 75	$ (192,042)	$ 175,330
Balance at the end of period (in shares) at Mar. 31, 2020	39,757,623

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (26,179)	$ (15,934)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	86	19
Stock-based compensation	2,211	864
Foreign currency transactions	25	51
Changes in assets and liabilities:
Other current assets	759	902
Other assets	(11)	(56)
Accounts payable	1,740	(134)
Accrued liabilities and other	(387)	805
NET CASH USED IN OPERATING ACTIVITIES	(21,756)	(13,483)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(26)	(126)
NET CASH USED IN INVESTING ACTIVITIES	(26)	(126)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercised stock options	370
NET CASH PROVIDED BY FINANCING ACTIVITIES	370
Effect of exchange rates on cash, cash equivalents and restricted cash	50	13
NET DECREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(21,362)	(13,596)
Cash, cash equivalents and restricted cash at the beginning of period	207,136	147,871
Cash, cash equivalents and restricted cash at the end of period	$ 185,774	134,275
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Property and equipment purchases in accounts payable		88
Right-of-use assets obtained in exchange for lease obligations		$ 2,320

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF BUSINESS	3 Months Ended
	Mar. 31, 2020
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 late-stage clinical biopharmaceutical company focused on the development and commercialization of novel antibody-based therapeutic products for the treatment of cancer. We have entered into a worldwide license and research collaboration agreement (the “MSK License Agreement”) with Memorial Sloan‑Kettering Cancer Center (“MSK”), under which we obtained the exclusive rights to MSK’s rights to two clinical stage antibody‑based product development programs for the treatment of neuroblastoma and other oncology indications. The MSK License Agreement also includes rights to certain next‑generation humanized, affinity matured bispecific antibodies. The Company is headquartered in New York, 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, 2020
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE 2—BASIS OF PRESENTATION The Company has not generated any revenue and 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 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 preclinical 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 the development stage. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval 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 and had an accumulated deficit of $192.0 million as of March 31, 2020 and $165.9 million as of December 31, 2019. Through March 31, 2020, the Company has funded its operations through proceeds from sales of shares of its common stock, including its initial public offering (“IPO”), in September 2018 and its secondary public offering in November 2019. As of March 31, 2020, the Company had cash and cash equivalents of $185.8 million, and as of December 31, 2019 the Company had cash and cash equivalents of $207.1 million. As of the issuance date of the quarterly financial statements for the three months ended March 31, 2020, the Company expects that its cash and cash equivalents at March 31, 2020 will be sufficient to fund its operating expenses and capital expenditure requirements through at least the next twelve months. The future viability of the Company, until such time that the Company has commercialized any of its products, is dependent on its ability to raise additional capital to finance its operations. The Company may be required to 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 at all or on attractive terms when needed from equity or debt financing. If the Company is unable to obtain additional financing from these or other sources when needed, or to the extent needed, it may be necessary to significantly reduce its current rate of spending through delaying, scaling back, 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 subsidiary 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, 2020 are not necessarily indicative of the results that may be expected for the year ended December 31, 2020, any other interim periods, or any future year or period. The December 31, 2019 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 condensed 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, 2019.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 3—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Our critical accounting policies are detailed in our Annual Report on Form 10-K for the year ended December 31, 2019. Effective January 1, 2020, the Company adopted Accounting Standards Update No. 2018-15 (“ASU 2018-15”), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service. The adoption of ASU 2018-15 did not have a material impact on the Company’s consolidated financial statements. Operating Leases As described below, the Company adopted Topic 842 as of January 1, 2019. 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. Topic 842 also provides practical expedients and certain exemptions for an entity’s ongoing accounting post implementation. The Company currently elected 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 elected 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 6 for the related disclosures. 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. We do not anticipate any losses with respect to such cash balances. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (i.e. an exit price). The accounting guidance includes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy are as follows: • 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, 2020 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 Fair Value Measurements at December 31, 2019 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 197,879 $ — $ 197,879 $ — $ 197,879 $ — $ 197,879 During the quarter ended March 31, 2020, there were no transfers between Level 1, Level 2, and Level 3. 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, 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. We have made estimates of the impact of COVID-19 within our financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates. Segment Information The Company is engaged solely in the discovery and development 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 In August 2018, the FASB issued Accounting Standards Update No. 2018-15 (“ASU 2018-15”), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement, which was issued in April 2015. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal use software (and hosting arrangements that include an internal-use software license). ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years with early adoption permitted. The adoption of this standard on January 1, 2020 did not have a material impact on our consolidated financial statements and related disclosures. In July 2018, the FASB issued Accounting Standards Update No. 2018-09 (“ASU 2018-09”), Codification Improvements, which clarify, correct errors in, or make minor improvements to a variety of ASC topics. The changes in ASU 2018-09 are not expected to have a significant effect on current accounting practices. Some of the amendments in this update do not require transition guidance and will be effective upon this update. However, many of the updates do have transition guidance with effective dates for periods beginning after December 15, 2018. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU No. 2018‑07, Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share‑Based Payment Accounting (“ASU 2018‑07”). ASU 2018‑07 is intended to simplify aspects of share‑based compensation issued to non‑employees by making the guidance consistent with the accounting for employee share‑based compensation. ASU 2018‑07 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In February 2018, the FASB issued Accounting Standards Update No. 2018‑02, (“ASU 2018-02”), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. ASU 2018‑02 allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018‑07 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In February 2016, the FASB issued Accounting Standards Update No. 2016‑02 (“ASU 2016‑02”), Leases, which is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018 with early adoption permitted. Under ASU 2016‑02, lessees will be required to recognize for all leases, at the commencement date of the lease, a lease liability, which is a lessee’s obligation to make lease payments arising from a lease measured on a discounted basis, and a right‑to‑use asset, which is an asset that represents the lessee’s right to use or control the use of a specified asset for the lease term. Topic 842 was subsequently amended by ASU 2017-13, Revenue and Leases: Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments; ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU No. 2018-10, Codification Improvements to Topic 842, Leases; ASU No. 2018-11, Targeted Improvements and ASU No. 2018-20, Narrow Scope Improvements for Lessors. The Company adopted the new leasing standards using the modified retrospective transition approach as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company used the effective date as our date of initial application. Consequently, financial information was not updated and the disclosures required under the new standard are not provided for dates and periods before January 1, 2019. The new standard also provides a number of optional practical expedients in transition. The Company elected the package of practical expedients, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. Upon adoption of the new leasing standards, the Company recognized a lease liability of $1.8 million and a related right-of-use asset of $1.5 million with the difference being due to the elimination of previously reported deferred rent. The Company subsequently entered into two new lease agreements during the three months ended March 31, 2019, and recognized an incremental lease liability and related right-of-use asset of $0.9 million.

NET LOSS PER SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2020
NET LOSS PER SHARE
NET LOSS PER SHARE	NOTE 4—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: Three months ended March 31, 2020 2019 (in thousands, except per share amounts) Net loss (numerator) $ (26,179) $ (15,934) Weighted-average shares (denominator) 39,754 34,194 Basic and diluted net loss per share $ (0.66) $ (0.47) Potentially dilutive securities excluded from the computation of diluted earnings per share relate to stock options outstanding and unvested restricted shares and RSUs and totaled 4,721,824 shares as of March 31, 2020 and 3,388,169 shares as of March 31, 2019.

ACCRUED LIABILITIES

ACCRUED LIABILITIES	3 Months Ended
	Mar. 31, 2020
ACCRUED LIABILITIES
ACCRUED LIABILITIES	NOTE 5—ACCRUED LIABILITIES Accrued short‑term liabilities at March 31, 2020 and December 31, 2019 are as follows: March 31, December 31, 2020 2019 (in thousands) Accrued milestone and royalty payments $ 374 $ 354 Accrued clinical costs 927 1,584 Accrued compensation and board fees 1,574 1,475 Accrued manufacturing costs 759 760 Other 401 377 Total $ 4,035 $ 4,550

LICENSE AGREEMENTS AND COMMITME

LICENSE AGREEMENTS AND COMMITMENTS	3 Months Ended
	Mar. 31, 2020
LICENSE AGREEMENTS AND COMMITMENTS
LICENSE AGREEMENTS AND COMMITMENTS	NOTE 6—LICENSE AGREEMENTS AND COMMITMENTS As of March 31, 2020, the Company has entered into two license agreements and certain other agreements with MSK. The license agreements are further described below as the MSK License and the CD33 License Agreement. Additionally, through a Settlement and Assumption and Assignment of the MSK License and Y-mAbs Sublicense Agreement (SAAA) with MabVax and MSK, the Company has established a direct license with MSK relating to the GD2-GD3 Vaccine, which was originally sublicensed in 2018 from MabVax. These license agreements with MSK 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. Certain of the payments are contingent milestone and royalty payments, the terms of which are further described below. Amounts disclosed in footnote 5 for accrued milestone and royalty payments are inclusive of obligations under the MSK License and CD33 License Agreement, collectively. MSK License Agreement On August 20, 2015, we entered into the MSK License Agreement that grants us a worldwide, sublicensable license to MSK’s rights to certain patent rights and intellectual property rights to develop, make, and commercialize licensed products and to perform services for all therapeutic and diagnostic uses in the field of cancer diagnostics and cancer treatments. The patents and patent applications covered by this agreement are directed, in part, to naxitamab, an anti-GD2 antibody, and omburtamab, which is an anti B3‑H7 antibody, as well as affinity matured versions of certain antibodies and certain single chain variable fragments (Fv) constructs, and their use for immunotherapy, targeting the treatment of oncology indications. Upon entering into the MSK License Agreement in 2015 and in exchange for the licenses, we paid MSK an upfront payment, issued 1,428,500 shares of our common stock to MSK and provided certain anti‑dilution rights to MSK. In addition, we are required to pay to MSK certain royalty and milestone payments. We expensed the upfront payment and the issuance of shares to MSK in 2015. We also recorded expense related to common stock issued related to certain anti‑dilution rights held by MSK. The MSK License Agreement requires us to pay to MSK mid to high single digit royalties based on annual net sales of licensed products or the performance of licensed services by us and our affiliates and sublicensees. We are obligated to pay annual minimum royalties of $80,000 over the royalty term, commencing on the fifth anniversary of the license agreement. These amounts are non‑refundable but are creditable against royalty payments otherwise due under the MSK License Agreement. The Company expensed the total minimum royalty payments of $1,200,000 in 2016. As of December 31, 2019, $29,000 was recorded as short-term accrued liabilities and $1,171,000 was recorded as long‑term accrued liabilities. As of March 31, 2020, $49,000 was recorded as short-term accrued liabilities and $1,151,000 was recorded as long‑term accrued liabilities. We are also obligated to pay MSK certain clinical, regulatory and sales‑based milestone payments under the MSK License Agreement. Certain of the clinical and regulatory milestone payments become due at the earlier of completion of the related milestone activity or the date indicated in the MSK License Agreement. Total clinical and regulatory milestones potentially due under the MSK License Agreement are $2,450,000 and $9,000,000, respectively. There are also sales‑based milestones, totaling $20,000,000, that become due should the Company achieve certain amounts of sales of licensed products. The Company records milestones in the period in which the contingent liability is probable and the amount is reasonably estimable. In addition, to the extent we enter into sublicense arrangements, we are obligated to pay to MSK a percentage of certain payments received from sublicensees of the rights licensed to us by MSK, which percentage will be based upon the achievement of certain clinical milestones. The Company has not entered into any sublicenses related to the MSK License Agreement. Failure by the Company to meet certain conditions under the arrangement could cause the related license to such licensed product to be canceled and could result in termination of the entire arrangement with MSK. In addition, the Company may terminate the MSK License Agreement with prior written notice to MSK. No milestones were expensed during the three months ended March 31, 2020 or 2019. As of March 31, 2020 and December 31, 2019, $225,000 of accrued milestone obligations were recorded in accrued short‑term liabilities and $300,000 was recorded within accrued long‑term liabilities. These clinical milestone-related charges were recorded as research and development expense upon determination that payment was probable. Research and development is inherently uncertain and as described above, should such research and development fail, the MSK License Agreement is cancelable at the Company’s option. The Company also considered the development risk and each party’s termination rights under the agreement when considering whether any regulatory‑based milestone payments, certain of which also contain time‑based payment requirements, were probable. Such regulatory‑based obligations were determined not to be probable as of March 31, 2020 and December 31, 2019, and therefore have not been accrued. CD33 License Agreement On November 13, 2017, we entered into an exclusive license agreement for MSK rights in connection with certain CD33 antibodies, which we refer to as the CD33 License Agreement. The CD33 License Agreement obligates us to pay to MSK mid to high single digit royalties based on annual net sales of licensed products or the performance of licensed services by us and our affiliates and sublicensees. We are obligated to pay annual minimum royalties of $40,000 over the royalty term, increasing to $60,000 once a patent within the licensed rights is issued, and commencing on the tenth anniversary of the CD33 License Agreement. These amounts are non‑refundable but are creditable against royalty payments otherwise due under the agreement. We were also obligated to pay MSK certain fees under a sponsored research agreement under the CD33 License Agreement during the years 2017 through 2019. In addition, milestone payments become due upon achievement of the related clinical, regulatory or sales‑based milestones defined in the CD33 License Agreement. Certain of these payments become due at the earlier of completion of the related milestone activity or the date indicated in the CD33 License Agreement. Total potential clinical and regulatory milestones potentially due under the CD33 License Agreement are $1,050,000. There are also sales‑based milestones that become due should the Company achieve certain amounts of sales of licensed products, with total sales‑based milestones potentially due of $7,500,000. The Company may terminate the CD33 License Agreement with prior written notice to MSK. The Company records milestones in the period in which the contingent liability is probable and the amount is reasonably estimable. In addition, to the extent we enter into sublicense arrangements, we are obligated to pay to MSK a percentage of certain payments received from sublicensees of the rights licensed to us by MSK, which percentage will be based upon the achievement of certain clinical milestones. The Company has not entered into any sublicenses related to the CD33 License Agreement. Total milestone obligations previously expensed under the CD33 License Agreement with MSK were $550,000, all of which related to clinical milestones. Such clinical milestone obligations become due either based upon the passage of time or achievement of the related milestone activities. None of these clinical milestone obligations were paid in 2020 or 2019. A total of $450,000 was recorded as accrued long‑term liabilities and $100,000 as accrued short-term liabilities as of March 31, 2020 and December 31, 2019. Research and development is inherently uncertain and as described above, should such research and development fail, the CD33 License Agreement is cancelable at the Company’s option. The Company considered risks as well as each party’s termination rights under the CD33 License Agreement when considering whether any regulatory‑based milestone payments and minimum royalty payments, certain of which also contain time‑based payment requirements, were probable. Given the uncertainty associated with research and development and the Company’s ability to cancel the CD33 License Agreement, such obligations were determined not to be probable as of March 31, 2020 and December 31, 2019 and therefore have not been accrued. MabVax Sublicense Agreement On June 27, 2018, we entered into a sublicense agreement with MabVax pursuant to which MabVax has sublicensed to the Company certain of MabVax’s patent rights and know‑how for development and commercialization of products for the prevention or treatment of neuroblastoma by means of administering a GD2-GD3 Vaccine, granted to MabVax pursuant to an exclusive license agreement between MabVax and MSK. Under the sublicense agreement, the Company previously paid and expensed the license fees. The Company has agreed to become solely responsible for future amounts payable to MSK and to handle other of MabVax’ obligations applicable to the licensed indication towards MSK. This includes the obligation to pay development milestones totaling $1,400,000 and mid single digit royalty payments to MSK. On March 21, 2019, MabVax filed a voluntary petition for relief under Chapter 11 of the Bankruptcy Code. On December 2, 2019, we entered into the SAAA to preserve the License Agreement and the rights granted to us under the Sublicense Agreement and to create a direct relationship between MSK and us with respect to the rights covered under the Sublicense Agreement. Research and development is inherently uncertain and as described above, should such research and development fail, the SAAA is cancelable at the Company’s option. The Company considered risks as well as each party’s termination rights under the SAAA when considering whether any milestone payments and minimum royalty payments were probable. Given the uncertainty associated with research and development and the Company’s ability to cancel the SAAA, such obligations were determined not to be probable as of March 31, 2020 and December 31, 2019 and therefore have not been accrued. SADA License Agreement As a subsequent event, on April 15, 2020, we entered into the SADA License Agreement that grants us a worldwide, sublicensable license to MSK’s and Massachusetts Institute of Technology’s (MIT’s) rights to certain patent rights and intellectual property rights to develop, make, and commercialize licensed products and to perform services for all therapeutic and diagnostic uses in the field of cancer diagnostics and cancer treatments using the SADA BiDE Pre-targeted Radioimmunotherapy Platform (SADA technology). The patents and patent applications covered by this agreement are directed, in part, to the SADA technology, as well as a number of SADA constructs developed by MSK. Upon entering into the SADA License Agreement in April 2020 and in exchange for the licenses, we will pay MSK and MIT an upfront payment of $1,995,000 and will issue 42,900 shares of our common stock to the licensors. We will expense the upfront payment and the issuance of shares at the effective date of the SADA License Agreement. The SADA License Agreement requires us to pay to MSK and MIT mid to high single digit royalties based on annual net sales of licensed products or the performance of licensed services by us and our affiliates and sublicensees. We are obligated to pay annual minimum royalties of $40,000, increasing to $60,000 once a patent has been issued, over the royalty term, commencing on the tenth anniversary of the license agreement. These amounts are non-refundable but are creditable against royalty payments otherwise due under the SADA License Agreement. We are also obligated to pay MSK and MIT certain clinical, regulatory and sales-based milestone payments under the SADA License Agreement. Certain of the clinical and regulatory milestone payments become due at the earlier of completion of the related milestone activity or the date indicated in the SADA License Agreement. Total clinical and regulatory milestones potentially due under the SADA License Agreement are $4,730,000 and $18,125,000, respectively. There are also sales-based milestones, totaling $23,750,000, that become due should the Company achieve certain amounts of sales of licensed products. The Company records milestones in the period in which the contingent liability is probable and the amount is reasonably estimable. In addition, to the extent we enter into sublicense arrangements, we are obligated to pay to MSK and MIT a percentage of certain payments received from sublicensees of the rights licensed to us by MSK and MIT, which percentage will be based upon the achievement of certain clinical milestones. The Company has not entered into any sublicenses related to the SADA License Agreement. For each of the constructs previously generated by MSK or MIT using the SADA technology and sold for the Company by a sublicensee , the Company will pay sales milestones up to $60,000,000 in total. Failure by the Company to meet certain conditions under the arrangement could cause the related license to such licensed product to be canceled and could result in termination of the entire arrangement with MSK and MIT. In addition, the Company may terminate the SADA License Agreement with prior written notice. Research and development is inherently uncertain and as described above, should such research and development fail, the SADA License Agreement is cancelable at the Company’s option. The Company will also consider the development risk and each party’s termination rights under the agreement when considering whether any regulatory based milestone payments, certain of which also contain time-based payment requirements, are probable. 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 a CD33 sponsored research agreement pursuant to which we agreed to pay MSK to provide research services over a period of two years related to the intellectual property licensed under the CD33 License Agreement. For three months ended March 31, 2020 and 2019, we incurred research and development expenses of $1,049,000 and $1,723,000, respectively, under these agreements. Lease Agreements In February 2019, the Company entered into a lease agreement in connection with its 4,500 square feet laboratory in New Jersey. 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. 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. Additionally, 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. The lease is payable in monthly installments of approximately $19,000, which are recognized on a straight‑line basis. Until the end of March 2018, the Company has maintained a lease for certain office space in Denmark. As described above in Note 3, the Company adopted Topic 842 as of January 1, 2019. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under Topic 840. Total operating lease costs were $174,000 and $141,000 for the three months ended March 31, 2020 and 2019, respectively. During the three months ended March 31, 2020, the expenses were recorded as $123,000 in research and development expense and $51,000 in general and administrative expense. During the three months ended March 31, 2019, the expenses were recorded as $97,000 in research and development expense and $44,000 in general and administrative expense. Cash paid for amounts included in the measurement of lease liabilities for the three months ended March 31, 2020 and 2019 was $188,000 and $32,000, 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, 2020 were as follows (in thousands): Operating Leases at March 31, 2020 Remainder of 2020 $ 563 Years ending December 31, 2021 754 2022 647 2023 540 2024 64 Total lease payments 2,568 Less: Imputed interest (477) Total operating lease liabilities at March 31, 2020 $ 2,091 Maturities of operating lease liabilities at December 31, 2019 were as follows (in thousands): Operating Leases at December 31, 2019 2020 $ 749 2021 753 2022 646 2023 539 2024 77 Total lease payments 2,764 Less: Imputed interest (534) Contractual obligations at December 31, 2019 $ 2,230 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, 2020, the weighted average remaining lease term is 3.51 years and the weighted average discount rate used to determine the operating lease liability was 11.0%.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2020
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 7—STOCKHOLDERS’ EQUITY Authorized Stock As of March 31, 2020 and December 31, 2019, 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 39,757,623 shares of its common stock as of March 31, 2020 and 39,728,416 shares of its common stock as of December 31, 2019. 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, 2020 or December 31, 2019. Stock grant agreements with non‑employees In August 2015, we entered into certain stock grant agreements with non‑employees of the Company. We agreed to issue a total of 2,800,000 shares to two non‑employee researchers who were involved in the development of technology licensed from MSK in consideration for their prior service. These two researchers were employees of MSK. The shares are released according to a vesting schedule. A total of 560,000 shares were issued in 2015, and a total of 448,000 shares issued in each of 2016 and 2017. In 2018, a total of 544,000 shares were issued to the two researchers, whereby one of the two grants were fully issued. In 2019 a total of 400,000 shares were issued to one of the physicians, and the remaining 400,000 shares are to be issued in August 2020, subject to certain conditions, such that the total grant will have been issued. The total award was expensed at its estimated fair value in 2015, as no future service was required to continue to vest in and receive the shares. Issuance of common stock In November 2019, we completed a secondary public offering and issued 5,134,750 shares of our Common Stock at a purchase price of $28.00 per share for an aggregate consideration of $134,704,000, net of issuance costs of $9,100,000.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2020
SHARE-BASED COMPENSATION
SHARE-BASED COMPENSATION	NOTE 8—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, 2020 and 2019, stock-based compensation for stock option grants were $2,188,000 and $848,000, respectively, for options granted to employees and directors. During the three months ended March 31, 2020, the expenses were recorded as $489,000 in research and development expense and $1,699,000 in general and administrative expense. During the three months ended March 31, 2019, the expenses were recorded as $145,000 in research and development expense and $703,000 in 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, 2019 4,005,873 $ 10.67 $ 82,944 7.34 Granted 717,000 29.26 Exercised (25,778) 14.35 Outstanding and expected to vest at March 31, 2020 4,697,095 $ 13.49 $ 63,082 7.51 Exercisable at March 31, 2020 2,626,106 $ 5.65 $ 53,554 6.24 The weighted average fair value of stock options granted during the three months ended March 31, 2020 and 2019 was $16.94 and $12.88, respectively. 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. As of March 31, 2020, we had $25.9 million of unrecognized compensation related to employee stock options that are expected to vest over a period of 3.03 years. As of December 31, 2019, we had $15.9 million of unrecognized compensation related to employee stock options that are expected to vest over a period of 2.72 years. Restricted Stock Unit Activity During the three months ended March 31, 2020 and March 31, 2019, stock-based compensation for restricted stock unit grants was $23,000 and $16,000, respectively. During the three months ended March 31, 2020, the expenses were recorded as $21,000 in research and development expense and $2,000 in general and administrative expense. During the three months ended March 31, 2019, the expenses were recorded as $14,000 in research and development expense and $2,000 in general and administrative expense. The following table summarizes restricted stock units issued and outstanding: Restricted Stock Units Outstanding and expected to vest at December 31, 2019 10,296 Granted 17,862 Vested (3,429) Outstanding and expected to vest at March 31, 2020 24,729 The weighted average fair value of restricted stock units granted during the three months ended March 31, 2020 was $20.74. As of March 31, 2020, we had $486,000 of unrecognized compensation related to employee restricted stock units that are expected to vest over a period of 2.54 years. As of March 31, 2019, we had $222,000 of unrecognized compensation related to employee restricted stock units that are expected to vest over a period of 2.80 years.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2020
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	NOTE 9—RELATED PARTY TRANSACTIONS MSK is a shareholder of the Company. Under the MSK License Agreement, the CD33 License Agreement, CTA, CFAs, SRA and MDSA, we have expensed costs in the total amount of $1,049,000 and $1,723,000 in the three months ended March 31, 2020 and 2019, respectively, for milestones, minimum royalties, and research and development costs. Please refer to Note 6 for additional details on our agreements with MSK. As of March 31, 2020 and December 31, 2019, we had a total of $3,711,000 and $4,171,000, respectively, recorded as accounts payable and accrued liabilities related to amounts due to MSK.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2020
INCOME TAXES
INCOME TAXES	NOTE 10—INCOME TAXES The Company provided no current and deferred income taxes on net losses of $26,179,000 and $15,934,000 for the three-month periods ended March 31, 2020 and 2019, 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. As of March 31, 2020 and December 31, 2019, the Company has determined that there were no uncertain tax positions. The Company’s tax returns for years 2019, 2018, 2017, 2016, and 2015 are open for tax examination by U.S. federal and state, and the Danish tax authorities. The valuation allowance related primarily to net U.S. deferred tax assets from operating losses, research and development tax credit carryforwards, and acquired intangibles. 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, 2020
OTHER BENEFITS
OTHER BENEFITS	NOTE 11—OTHER BENEFITS The Company has adopted a defined contribution 401(k) savings plan (the 401(k) plan) covering all U.S. employees of the Company. 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, 2020 and 2019. The Company has established a retirement program for employees of the Company’s 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. No contributions from our Danish subsidiary were made during the three months ended March 31, 2020, and contributions were immaterial during the three months ended March 31, 2019. 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.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2020
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 12-SUBSEQUENT EVENTS As discussed previously in Note 6 License Agreements and Commitments, in April 2020 the Company entered into an agreement with MSK and MIT for a worldwide exclusive license and research collaboration to develop and commercialize antibody constructs based on the SADA-BiDE (2-step Self-Assembly and DisAssembly-Bispecific DOTA-Engaging antibody system) Pre-targeted Radioimmunotherapy Platform (the SADA technology), a concept also referred to as Liquid Radiation TM .

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Operating Leases	Operating Leases As described below, the Company adopted Topic 842 as of January 1, 2019. 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. Topic 842 also provides practical expedients and certain exemptions for an entity’s ongoing accounting post implementation. The Company currently elected 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 elected 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 6 for the related disclosures.
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. We do not anticipate any losses with respect to such cash balances.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (i.e. an exit price). The accounting guidance includes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy are as follows: • 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, 2020 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 Fair Value Measurements at December 31, 2019 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 197,879 $ — $ 197,879 $ — $ 197,879 $ — $ 197,879 During the quarter ended March 31, 2020, there were no transfers between Level 1, Level 2, and Level 3.
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, 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. We have made estimates of the impact of COVID-19 within our financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates.
Segment Information	Segment Information The Company is engaged solely in the discovery and development 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 In August 2018, the FASB issued Accounting Standards Update No. 2018-15 (“ASU 2018-15”), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement, which was issued in April 2015. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal use software (and hosting arrangements that include an internal-use software license). ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years with early adoption permitted. The adoption of this standard on January 1, 2020 did not have a material impact on our consolidated financial statements and related disclosures. In July 2018, the FASB issued Accounting Standards Update No. 2018-09 (“ASU 2018-09”), Codification Improvements, which clarify, correct errors in, or make minor improvements to a variety of ASC topics. The changes in ASU 2018-09 are not expected to have a significant effect on current accounting practices. Some of the amendments in this update do not require transition guidance and will be effective upon this update. However, many of the updates do have transition guidance with effective dates for periods beginning after December 15, 2018. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU No. 2018‑07, Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share‑Based Payment Accounting (“ASU 2018‑07”). ASU 2018‑07 is intended to simplify aspects of share‑based compensation issued to non‑employees by making the guidance consistent with the accounting for employee share‑based compensation. ASU 2018‑07 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In February 2018, the FASB issued Accounting Standards Update No. 2018‑02, (“ASU 2018-02”), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. ASU 2018‑02 allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018‑07 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The adoption of this standard on January 1, 2019 did not have a material impact on our consolidated financial statements and related disclosures. In February 2016, the FASB issued Accounting Standards Update No. 2016‑02 (“ASU 2016‑02”), Leases, which is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018 with early adoption permitted. Under ASU 2016‑02, lessees will be required to recognize for all leases, at the commencement date of the lease, a lease liability, which is a lessee’s obligation to make lease payments arising from a lease measured on a discounted basis, and a right‑to‑use asset, which is an asset that represents the lessee’s right to use or control the use of a specified asset for the lease term. Topic 842 was subsequently amended by ASU 2017-13, Revenue and Leases: Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments; ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU No. 2018-10, Codification Improvements to Topic 842, Leases; ASU No. 2018-11, Targeted Improvements and ASU No. 2018-20, Narrow Scope Improvements for Lessors. The Company adopted the new leasing standards using the modified retrospective transition approach as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company used the effective date as our date of initial application. Consequently, financial information was not updated and the disclosures required under the new standard are not provided for dates and periods before January 1, 2019. The new standard also provides a number of optional practical expedients in transition. The Company elected the package of practical expedients, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. Upon adoption of the new leasing standards, the Company recognized a lease liability of $1.8 million and a related right-of-use asset of $1.5 million with the difference being due to the elimination of previously reported deferred rent. The Company subsequently entered into two new lease agreements during the three months ended March 31, 2019, and recognized an incremental lease liability and related right-of-use asset of $0.9 million.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 $ — $ 173,587 Fair Value Measurements at December 31, 2019 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 197,879 $ — $ 197,879 $ — $ 197,879 $ — $ 197,879

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2020
NET LOSS PER SHARE
Schedule of basic and diluted net loss per share	Three months ended March 31, 2020 2019 (in thousands, except per share amounts) Net loss (numerator) $ (26,179) $ (15,934) Weighted-average shares (denominator) 39,754 34,194 Basic and diluted net loss per share $ (0.66) $ (0.47)

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2020
ACCRUED LIABILITIES
Summary of accrued short-term liabilities	March 31, December 31, 2020 2019 (in thousands) Accrued milestone and royalty payments $ 374 $ 354 Accrued clinical costs 927 1,584 Accrued compensation and board fees 1,574 1,475 Accrued manufacturing costs 759 760 Other 401 377 Total $ 4,035 $ 4,550

LICENSE AGREEMENTS AND COMMIT_2

LICENSE AGREEMENTS AND COMMITMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
LICENSE AGREEMENTS AND COMMITMENTS
Maturities of operating lease liabilities	Maturities of operating lease liabilities at March 31, 2020 were as follows (in thousands): Operating Leases at March 31, 2020 Remainder of 2020 $ 563 Years ending December 31, 2021 754 2022 647 2023 540 2024 64 Total lease payments 2,568 Less: Imputed interest (477) Total operating lease liabilities at March 31, 2020 $ 2,091 Maturities of operating lease liabilities at December 31, 2019 were as follows (in thousands): Operating Leases at December 31, 2019 2020 $ 749 2021 753 2022 646 2023 539 2024 77 Total lease payments 2,764 Less: Imputed interest (534) Contractual obligations at December 31, 2019 $ 2,230

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2019 4,005,873 $ 10.67 $ 82,944 7.34 Granted 717,000 29.26 Exercised (25,778) 14.35 Outstanding and expected to vest at March 31, 2020 4,697,095 $ 13.49 $ 63,082 7.51 Exercisable at March 31, 2020 2,626,106 $ 5.65 $ 53,554 6.24
Schedule of restricted stock units issued and outstanding	Restricted Stock Units Outstanding and expected to vest at December 31, 2019 10,296 Granted 17,862 Vested (3,429) Outstanding and expected to vest at March 31, 2020 24,729

ORGANIZATION AND DESCRIPTION _2

ORGANIZATION AND DESCRIPTION OF BUSINESS (Details)	3 Months Ended
	Mar. 31, 2020agreement
ORGANIZATION AND DESCRIPTION OF BUSINESS
Number of product development programs for which entity has obtained exclusive rights	2

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Issuance of stock
Accumulated deficit	$ 192,042	$ 165,863
Cash and cash equivalents	$ 185,774	$ 207,136

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Operating Leases (Details) $ in Millions	Mar. 31, 2020USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Residual value guarantees	$ 0

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value Measurement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
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	173,587	$ 197,879
Recurring | Money market funds
Fair value measurements
Cash equivalents	173,587	197,879
Recurring | Level 2
Fair value measurements
Cash equivalents	173,587	197,879
Recurring | Level 2 | Money market funds
Fair value measurements
Cash equivalents	$ 173,587	$ 197,879

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Segment (Details)	3 Months Ended
	Mar. 31, 2020segment
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Number of operating segments	1

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently issued accounting pronouncements (Details) $ in Thousands	Jan. 01, 2019USD ($)	Mar. 31, 2019USD ($)lease	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
New accounting pronouncements
Lease liability			$ 2,091	$ 2,230
Operating lease right-of-use assets			$ 1,865	$ 1,989
Number of lease agreements entered into during the period | lease		2
Increase in lease liability upon entering into new lease agreements		$ 900
Increase in right-of-use assets upon entering into new lease agreements		$ 900
ASU 2016-02
New accounting pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected	Modified Retrospective
New Accounting Pronouncement or Change in Accounting Principle, Prior Period Not Restated	true
Lease, Practical Expedients, Package	true
ASU 2016-02 | Adjustment
New accounting pronouncements
Lease liability	$ 1,800
Operating lease right-of-use assets	$ 1,500

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, 2020	Mar. 31, 2019
NET LOSS PER SHARE
Net loss (numerator)	$ (26,179)	$ (15,934)
Weighted-average shares (denominator)	39,753,583	34,193,666
Basic and diluted net loss per share (in dollars per share)	$ (0.66)	$ (0.47)

NET LOSS PER SHARE - Anti-dilut

NET LOSS PER SHARE - Anti-dilutive securities (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
NET LOSS PER SHARE
Potentially dilutive securities outstanding	4,721,824	3,388,169

ACCRUED LIABILITIES (Details)

ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued short term liabilities
Accrued milestone and royalty payments	$ 374	$ 354
Accrued clinical costs	927	1,584
Accrued compensation and board fees	1,574	1,475
Accrued manufacturing costs	759	760
Other	401	377
Total	$ 4,035	$ 4,550

LICENSE AGREEMENTS AND COMMIT_3

LICENSE AGREEMENTS AND COMMITMENTS - MSK License Agreement (Details) - MSK License Agreement $ in Thousands	Aug. 20, 2015USD ($)shares	Mar. 31, 2020USD ($)agreement	Mar. 31, 2019USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2019USD ($)
Agreements
Number of license agreements | agreement		2
Issuance of common stock to strategic partner (in shares) | shares	1,428,500
Annual minimum royalties payable from fifth anniversary	$ 80
Expensed minimum royalty payments				$ 1,200
Clinical milestones potentially due	2,450
Regulatory milestones potentially due	9,000
Sales-based milestones potentially due	$ 20,000
Milestone expenses		$ 0	$ 0
Accrued short-term liabilities
Agreements
Short-term accrued minimum royalties		49			$ 29
Accrued milestone payments, current		225			225
Accrued long-term liabilities
Agreements
Long-term accrued minimum royalties		1,151			1,171
Accrued milestone payments, noncurrent		$ 300			$ 300

LICENSE AGREEMENTS AND COMMIT_4

LICENSE AGREEMENTS AND COMMITMENTS - CD33 License Agreement (Details) - CD33 License Agreement - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Nov. 13, 2017
Agreements
Annual minimum royalties payable				$ 40
Annual minimum royalties payable from tenth anniversary				60
Clinical and regulatory milestones potentially due				1,050
Sales-based milestones potentially due				$ 7,500
Clinical milestone expense			$ 550
Clinical milestone payment	$ 0	$ 0
Accrued short-term liabilities
Agreements
Accrued milestone payments, current	100	100
Accrued long-term liabilities
Agreements
Accrued milestone payments, noncurrent	$ 450	$ 450

LICENSE AGREEMENTS AND COMMIT_5

LICENSE AGREEMENTS AND COMMITMENTS - MabVax Sublicense Agreement (Details) $ in Thousands	Jun. 27, 2018USD ($)
MabVax Sublicense Agreement
Agreements
Development milestone payments due	$ 1,400

LICENSE AGREEMENTS AND COMMIT_6

LICENSE AGREEMENTS AND COMMITMENTS - SADA License Agreement (Details) - SADA License Agreement - Subsequent Event $ in Thousands	Apr. 15, 2020USD ($)shares
Agreements
Upfront payment	$ 1,995
Issuance of common stock to strategic partner (in shares) | shares	42,900
Annual minimum royalties payable	$ 40
Annual minimum royalties payable from tenth anniversary	60
Clinical milestones potentially due	4,730
Regulatory milestones potentially due	18,125
Sales-based milestones potentially due	23,750
Additional sales based milestone payments potentially due for each construct previously generated by MSK or MIT using SADA technology	$ 60,000

LICENSE AGREEMENTS AND COMMIT_7

LICENSE AGREEMENTS AND COMMITMENTS - Other agreements (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)employeeagreement	Mar. 31, 2019USD ($)employeeagreement	Dec. 31, 2019
CFAs
Agreements
Number of service agreements | agreement	2	2
CD33-SRA
Agreements
Research service period			2 years
Researchers, Employees of MSK | MDSA
Agreements
Number of individuals | employee	5	5
Research and development expense | MSK | MSK License Agreement, the CD33 License Agreement, CTA, CFAs, SRA and MDSA
Agreements
Related party expenses | $	$ 1,049	$ 1,723

LICENSE AGREEMENTS AND COMMIT_8

LICENSE AGREEMENTS AND COMMITMENTS - Lease agreements (Details) $ in Thousands	1 Months Ended
	Feb. 28, 2019USD ($)ft²	Feb. 28, 2018	Jan. 31, 2018USD ($)
Laboratory, New Jersey
Leases
Leased area (in square feet) | ft²	4,500
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
Lease term		3 years
Lease payable per month	$ 19

LICENSE AGREEMENTS AND COMMIT_9

LICENSE AGREEMENTS AND COMMITMENTS - Lease costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases
Total operating lease costs	$ 174	$ 141
Cash paid for amounts included in the measurement of lease liabilities	188	32
Research and development expense
Leases
Total operating lease costs	123	97
General and administrative expense
Leases
Total operating lease costs	$ 51	$ 44

LICENSE AGREEMENTS AND COMMI_10

LICENSE AGREEMENTS AND COMMITMENTS - Lease maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Future minimum commitments under all non-cancelable operating leases
Remainder of 2020	$ 563	$ 749
2021	754	753
2022	647	646
2023	540	539
2024	64	77
Total lease payments	2,568	2,764
Less: Imputed interest	(477)	(534)
Total operating lease liabilities at December 31, 2019	$ 2,091	$ 2,230

LICENSE AGREEMENTS AND COMMI_11

LICENSE AGREEMENTS AND COMMITMENTS - Lease term and discount rate (Details)	Mar. 31, 2020
LICENSE AGREEMENTS AND COMMITMENTS
Weighted average remaining lease term	3 years 6 months 4 days
Weighted average discount rate	11.00%

STOCKHOLDERS' EQUITY - Authoriz

STOCKHOLDERS' EQUITY - Authorized, Common and Preferred Stock (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)Vote$ / sharesshares	Dec. 31, 2019USD ($)Vote$ / 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	39,757,623	39,728,416
Preferred stock, shares issued	0	0

STOCKHOLDERS' EQUITY - Stock gr

STOCKHOLDERS' EQUITY - Stock grant agreements with non-employees, Stock (Details) - Nonemployees - Researchers, Employees of MSK	1 Months Ended	12 Months Ended						32 Months Ended
	Aug. 31, 2015individualshares	Dec. 31, 2020shares	Dec. 31, 2019individualshares	Dec. 31, 2018itemindividualshares	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015shares	Aug. 31, 2020item
Share-Based Compensation Awards
Number of individuals | individual	2		1	2
Number of stock grants | item				1
Forecast
Share-Based Compensation Awards
Number of stock grants | item								2
Common Stock
Share-Based Compensation Awards
Shares agreed to be issued	2,800,000
Issuance of common stock to nonemployees (in shares)			400,000	544,000	448,000	448,000	560,000
Common Stock | Forecast
Share-Based Compensation Awards
Issuance of common stock to nonemployees (in shares)		400,000

STOCKHOLDERS' EQUITY - Stock _2

STOCKHOLDERS' EQUITY - Stock grant agreements with non employees, Stock options (Details)	3 Months Ended
	Mar. 31, 2020shares
Share-Based Compensation Awards
Granted (in shares)	717,000

STOCKHOLDERS' EQUITY - Issuance

STOCKHOLDERS' EQUITY - Issuance of common stock (Details) - Secondary Public Offering $ / shares in Units, $ in Thousands	1 Months Ended
	Nov. 30, 2019USD ($)$ / sharesshares
Issuance of stock
Payment of offering costs	$ 9,100
Common Stock
Issuance of stock
Shares issued (in shares) | shares	5,134,750
Share price (in dollars per share) | $ / shares	$ 28
Issuance of shares of common stock, net of issuance costs	$ 134,704

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 | Employees and nonemployees owning less than 10% of voting power
Share-Based Compensation Awards
Vesting period	4 years

SHARE-BASED COMPENSATION - 2018

SHARE-BASED COMPENSATION - 2018 Plan (Details)	3 Months Ended
	Mar. 31, 2020shares
Share-Based Compensation Awards
Options granted (in shares)	717,000
2018 Plan
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%
2018 Plan | 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
2018 Plan | Stock options | Participants owning more than 10% of voting power
Share-Based Compensation Awards
Term of award	5 years
2018 Plan | 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 - Expe

SHARE-BASED COMPENSATION - Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock options | Employees and directors
Share-Based Compensation Awards
Stock-based compensation expenses	$ 2,188	$ 848
Stock options | Employees and directors | Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	489	145
Stock options | Employees and directors | General and administrative expense
Share-Based Compensation Awards
Stock-based compensation expenses	1,699	703
RSUs
Share-Based Compensation Awards
Stock-based compensation expenses	23	16
RSUs | Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	21	14
RSUs | General and administrative expense
Share-Based Compensation Awards
Stock-based compensation expenses	$ 2	$ 2

SHARE-BASED COMPENSATION - Stoc

SHARE-BASED COMPENSATION - Stock options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Options
Outstanding at beginning of period (in shares)	4,005,873
Granted (in shares)	717,000
Exercised (in shares)	(25,778)
Outstanding at end of period (in shares)	4,697,095		4,005,873
Exercisable at end of period (in shares)	2,626,106
Weighted average exercise price
Outstanding at beginning of period (in dollars per share)	$ 10.67
Granted (in dollars per share)	29.26
Exercised (in dollars per share)	14.35
Outstanding at end of period (in dollars per share)	13.49		$ 10.67
Exercisable at end of period (in dollars per share)	$ 5.65
Aggregate intrinsic value and Weighted average remaining contractual life (years)
Outstanding (in dollars)	$ 63,082		$ 82,944
Exercisable (in dollars)	$ 53,554
Outstanding (in years)	7 years 6 months 4 days		7 years 4 months 2 days
Exercisable (in years)	6 years 2 months 27 days
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 16.94	$ 12.88

SHARE-BASED COMPENSATION - Unre

SHARE-BASED COMPENSATION - Unrecognized compensation (Details) - Stock options - Employees - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Unrecognized compensation related to employee stock options
Unrecognized compensation	$ 25.9	$ 15.9
Expected vesting period	3 years 11 days	2 years 8 months 19 days

SHARE-BASED COMPENSATION - Rest

SHARE-BASED COMPENSATION - Restricted Stock Unit Activity (Details) - RSUs - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-Based Compensation Awards
Stock-based compensation expenses	$ 23	$ 16
Restricted stock units issued and outstanding
Outstanding and expected to vest at beginning of period (in shares)	10,296
Granted (in shares)	17,862
Vested (in shares)	(3,429)
Outstanding and expected to vest at end of period (in shares)	24,729
Weighted average fair value of units granted in period (in dollars per share)	$ 20.74
Unrecognized compensation	$ 486	$ 222
Expected vesting period	2 years 6 months 15 days	2 years 9 months 18 days
Research and development expense
Share-Based Compensation Awards
Stock-based compensation expenses	$ 21	$ 14
General and administrative expense
Share-Based Compensation Awards
Stock-based compensation expenses	$ 2	$ 2

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - MSK - MSK License Agreement, the CD33 License Agreement, CTA, CFAs, SRA and MDSA - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related party transactions
Due to related parties	$ 3,711		$ 4,171
Research and development expense
Related party transactions
Related party expenses	$ 1,049	$ 1,723

INCOME TAXES - Expense (Details

INCOME TAXES - Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Domestic and foreign loss before income taxes:
Losses before taxes	$ (26,179)	$ (15,934)
Income tax expense
Current income taxes	0	0
Deferred income taxes	$ 0	$ 0

INCOME TAXES - Uncertain tax po

INCOME TAXES - Uncertain tax positions (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
INCOME TAXES
Uncertain tax position	$ 0	$ 0

OTHER BENEFITS (Details)

OTHER BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employer matching contribution to defined contribution plan (as a percent)	0.00%	0.00%
Danish Subsidiary
Employer matching contribution to defined contribution plan (as a percent)	0.00%
Costs for employee health insurance benefits	$ 0	$ 0