Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2018	Mar. 14, 2019	Sep. 21, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Y-mAbs Therapeutics, Inc.
Entity Central Index Key	0001722964
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Public Float			$ 301.6
Entity Common Stock, Shares Outstanding		34,193,666

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 147,840	$ 90,483
Restricted cash	31	32
Other current assets	3,661	840
Total current assets	151,532	91,355
Property and equipment, net	205
Deferred offering costs		772
Other assets	187
TOTAL ASSETS	151,924	92,127
LIABILITIES
Accounts payable	5,872	5,909
Accrued liabilities	3,251	2,016
Total current liabilities	9,123	7,925
Accrued milestone and royalty payments	2,050	2,050
Other liabilities	224
TOTAL LIABILITIES	11,397	9,975
Commitments and contingencies (Note 6)
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value, 5,500,000 shares authorized at December 31, 2018 and December 31, 2017; none issued at December 31, 2018 and December 31, 2017
Common stock, $0.0001 par value, 100,000,000 and 50,000,000 shares authorized at December 31, 2018 and December 31, 2017, respectively; 34,193,666 and 26,749,666 shares issued at December 31, 2018, and December 31, 2017, respectively	3	3
Additional paid in capital	225,352	123,879
Accumulated other comprehensive income/(loss)	7	(169)
Accumulated deficit	(84,835)	(41,561)
TOTAL STOCKHOLDERS’ EQUITY	140,527	82,152
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 151,924	$ 92,127

Consolidated Balance Sheets (parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	50,000,000
Common stock, shares issued	34,193,666	26,749,666

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
OPERATING EXPENSES
Research and development	$ 34,269	$ 14,307
General and administrative	8,961	4,937
Total operating expenses	43,230	19,244
Loss from operations	(43,230)	(19,244)
OTHER INCOME/(EXPENSES)
Interest and other income/(expenses)	(44)	83
NET LOSS	(43,274)	(19,161)
Other comprehensive income/(loss)
Foreign currency translation	175	(199)
COMPREHENSIVE LOSS	$ (43,099)	$ (19,360)
Net loss per share attributable to common stockholders, basic and diluted	$ (1.50)	$ (0.99)
Weighted average common shares outstanding, basic and diluted	28,772,384	19,397,506

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive (Loss)/Income	Accumulated Deficit	Total
Balance at the beginning of period at Dec. 31, 2016	$ 2	$ 34,429	$ 30	$ (22,400)	$ 12,061
Balance at the beginning of period (in shares) at Dec. 31, 2016	16,552,884
Increase (Decrease) in Stockholders' Equity
Issuance of common stock to investors, net of issuance costs	$ 1	88,841			88,842
Issuance of common stock to investors, net of issuance costs (in shares)	9,748,782
Issuance of common stock to nonemployees (in shares)	448,000
Stock-based compensation expense		609			609
Foreign currency translation			(199)		(199)
Net loss				(19,161)	(19,161)
Balance at the end of period at Dec. 31, 2017	$ 3	123,879	(169)	(41,561)	82,152
Balance at the end of period (shares) at Dec. 31, 2017	26,749,666
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in initial public offering, net of issuance costs		99,507			99,507
Issuance of common stock (in shares)	6,900,000
Issuance of common stock to nonemployees (in shares)	544,000
Stock-based compensation expense		1,966			1,966
Foreign currency translation			176		176
Net loss				(43,274)	(43,274)
Balance at the end of period at Dec. 31, 2018	$ 3	$ 225,352	$ 7	$ (84,835)	$ 140,527
Balance at the end of period (shares) at Dec. 31, 2018	34,193,666

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (43,274,000)	$ (19,161,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	29,000
Stock-based compensation	1,966,000	609,000
Foreign currency transactions	97,000	(63,000)
Changes in assets and liabilities:
Other current assets	(2,821,000)	(482,000)
Other assets	(187,000)
Accounts payable	1,261,000	2,385,000
Accrued liabilities and other	1,700,000	842,000
NET CASH USED IN OPERATING ACTIVITIES	(41,229,000)	(15,870,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(234,000)
NET CASH USED IN INVESTING ACTIVITIES	(234,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock, net of issuance costs	99,765,000	89,844,000
Payment of offering costs	(1,002,000)	(258,000)
NET CASH PROVIDED BY FINANCING ACTIVITIES	98,763,000	89,586,000
Effect of exchange rates on cash and cash equivalents	56,000	(104,000)
NET INCREASE IN CASH AND CASH EQUIVALENTS	57,356,000	73,612,000
Cash, cash equivalents and restricted cash at the beginning of period	90,515,000	16,903,000
Cash, cash equivalents and restricted cash at the end of period	$ 147,871,000	90,515,000
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES
Common stock issuance cost in accounts payable		1,002,000
Deferred offering costs included in other assets and accounts payable and accrued liabilities and other		$ 514,000

ORGANIZATION AND DESCRIPTION OF BUSINESS	12 Months Ended
ORGANIZATION AND DESCRIPTION OF BUSINESS	Dec. 31, 2018
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”) our strategic partner, under which we have 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 a protein Multimerization Platform Technology—MULTI TAGTM, and an option to obtain the rights to certain chimeric antigen receptor T‑cell, or CAR‑T, technologies, as well as rights to next‑generation humanized, affinity matured bispecific antibodies. 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	12 Months Ended
BASIS OF PRESENTATION	Dec. 31, 2018
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; and dependence on key personnel, compliance with government regulations and the need to obtain additional financing. 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 $84.8 million as of December 31, 2018 and $41.6 million as of December 31, 2017. Through December 31, 2018, the Company has funded its operations through proceeds from sales of shares of its common stock, including its initial public offering, or IPO, in September 2018. As of December 31, 2018, the Company had cash and cash equivalents of $147.8 million, and as of December 31, 2017 the Company had cash and cash equivalents of $90.5 million. As of the issuance date of the annual financial statements for the year ended December 31, 2018, the Company expects that its cash and cash equivalents at December 31, 2018 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’s failure to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. The accompanying 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”). All intercompany balances and transactions have been eliminated.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2018

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 3—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

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, the valuation of shares of common stock and 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.

Cash and Cash Equivalents

The Company considers all highly‑liquid investments with maturities of three months or less from date of purchase to be cash equivalents.

The Company primarily maintains its cash balances with financial institutions in federally insured accounts and cash held in an unrestricted escrow account. The Company has cash in financial institutions in excess of FDIC insurance limits.

Restricted cash represents a bank account with funds to cover the Company’s corporate credit card availability.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight‑line method over the estimated useful life of each asset as follows:


		Estimated Useful Life
Furniture and fixtures		5 years
Leasehold improvements		Shorter of life of lease or 15 years

Depreciation and amortization expense on property and equipment was $29,000 and $0 for the years ended December 31, 2018 and 2017, respectively.

Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of Long‑Lived Assets

ASC 360, Property, Plant and Equipment, addresses the financial accounting and reporting for impairment or disposal of long‑lived assets. The Company reviews the recorded values of long‑lived assets for impairment whenever events or changes in business circumstance indicate that the carrying amount of an asset or group of assets may not be fully recoverable.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third‑party fees that are directly associated with in‑process equity financings as deferred offering costs within other assets until such financings are consummated. After consummation of the equity financing, these costs are recorded in shareholders’ equity as a reduction of proceeds generated as a result of the offering. Should the planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statement of comprehensive loss. The Company did not record any deferred offering costs as of December 31, 2018. The Company recorded deferred offering costs of $0.8 million as of December 31, 2017. Accounts payable and accrued liabilities at December 31, 2017 included $0.2 million of deferred offering costs. These deferred operating costs were reclassified to shareholders’ equity upon the successful completion of the IPO during the year ended December 31, 2018.

Income Taxes

The Company accounts for income taxes under the asset and liability approach for the financial accounting and reporting of income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to net operating loss carry forwards and temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. These assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which the temporary differences are expected to reverse. A valuation allowance is established when management determines that it is more likely than not that some portion or all of the deferred tax assets will not be realized.

The Company prepares and files tax returns based on its interpretation of tax laws and regulations. In the normal course of business, the Company’s tax returns are subject to examination by various taxing authorities. Such examinations may result in future tax and interest assessments by these taxing authorities. In determining the Company’s tax provision for financial reporting purposes, the Company establishes a reserve for uncertain tax positions unless such positions are determined to be more likely than not of being sustained upon examination based on their technical merits. The Company considers many factors when evaluating and estimating its tax positions and tax benefits, which may require periodic adjustments and which may not accurately anticipate actual outcomes. Accordingly, the Company will report a liability for unrecognized tax benefits resulting from any uncertain tax positions taken or expected to be taken on a tax return.

The Company’s policy is to recognize, when applicable, interest and penalties on uncertain tax positions as part of income tax expense.

In accordance with guidance issued by Financial Accounting Standards Board (“FASB”), companies should make and disclose a policy election as to whether they will recognize deferred taxes for basis differences expected to reverse as Global Intangible Low‑Taxed Income (“GILTI”) or whether they will account for GILTI as period costs if and when incurred. The Company has elected to recognize the resulting tax with respect to the GILTI provision as a period cost. No costs were incurred by the Company through December 31, 2018 as a result of GILTI.

Research and Development Costs

Research and development costs are charged to operations when incurred and are included in operating expenses. Research and development costs consist principally of compensation cost for our employees and consultants that perform our research activities, the fees paid to maintain our licenses, the payments to third parties for manufacturing and clinical research organizations and additional product development, and consumables and other materials used in research and development. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Actual results could differ from the Company’s estimates. The Company is obligated to make certain milestone and royalty payments in accordance with the contractual terms of its license agreement with MSK based upon the resolution of certain contingencies. The Company records the milestone and royalty payment when the achievement of the milestone or payment of the milestone or royalty is probable and the amount of the payment is reasonably estimable. Research and development costs were $34.3 million and $14.3 million for the years ended December 31, 2018 and 2017, respectively.

Patent Costs

The Company expenses the costs of obtaining and maintaining patents as general and administrative expenses.

Stock‑Based Compensation

The Company measures stock options granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards, over the requisite service period, which is the vesting period of the respective award. Forfeitures are accounted for as they occur. The Company issues stock options with only service‑based vesting conditions and records the expense for these awards using the straight‑line method over the requisite service period.

For share‑based awards granted to non‑employees, compensation expense is recognized over the period during which services are rendered by such non‑employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then‑current fair value of the Company’s common shares and updated assumption inputs in the Black‑Scholes option‑pricing model.

The fair value of each stock option grant is estimated on the date of grant using the Black‑Scholes option pricing model. The Company historically has been a private company and lacks company‑specific historical and implied volatility information for its shares. Therefore, it estimates its expected share price volatility based on the historical volatility of a group of publicly‑traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded share price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards as the Company has limited historical data to support the expected term assumption. The expected term of stock options granted to non‑employees is equal to the contractual term of the option award. The risk‑free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The expected dividend yield is based on the fact that the Company has never paid cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future.

Segment Information

The Company is engaged solely in the discovery and development of novel antibody therapeutic products to treat cancer. Accordingly, the Company has determined that it operates in one operating segment.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with shareholders. The difference between net loss and comprehensive loss for the period presented in the accompanying financial statements was due to foreign currency translation.

Foreign Currency

The financial statements of our Danish subsidiary with a functional currency other than the U.S. dollar are translated into U.S. dollars using period‑end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates for operating results. Translation gains and losses are included in accumulated other comprehensive income (loss), net of tax, in stockholders’ equity. Foreign currency transaction gains and losses are included in the results of operations in other income and expense, and totaled $(97,000) and $63,000 for the years ended December 31, 2018 and 2017, respectively.

Recently Issued Accounting Pronouncements - Adopted

In March 2018, the FASB issued Accounting Standards Update No. 2018-05 (“ASU 2018-05”), Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118. The ASU adds seven paragraphs to ASC 740, Income Taxes, that contain SEC guidance related to SAB 118 (codified as SEC SAB Topic 5.EE, “Income Tax Accounting Implications of the Tax Cuts and Jobs Act”), which provides guidance for companies that are not able to complete their accounting for the income tax effects of the Tax Cuts and Jobs Act in the period of enactment which is the period that includes December 22, 2017. The measurement period should not extend beyond one year from the enactment date. The Company completed its accounting for the income tax effects for the year ended December 31, 2018. See Note 10 for a discussion of the impact of the guidance on the Company’s consolidated financial statements.

In May 2017, the FASB issued Accounting Standards Update No. 2017‑09 (“ASU 2017‑09”), Compensation—Stock Compensation (Topic 718)—Scope of Modification Accounting. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award changes as a result of the change in terms or conditions. The guidance is effective prospectively for annual periods beginning on or after December 15, 2017 with early adoption permitted. The Company adopted ASU 2017‑09 on January 1, 2018 and will account for any modifications in accordance with ASU 2017‑09 subsequent to the effective date. The adoption of this standard on January 1, 2018 did not have a material impact on our consolidated financial statements and related disclosures.

In November 2016, the FASB issued Accounting Standards Update No. 2016‑18 (“ASU 2016‑18”), Statement of Cash Flows (Topic 230)—Restricted Cash. Under the new guidance, it changes the presentation of restricted cash and cash equivalents on the statement of cash flows. Restricted cash and restricted cash equivalents will be included with cash and cash equivalents when reconciling the beginning‑of‑period and end‑of‑period total amounts shown on the statement of cash flows. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The adoption of this standard on January 1, 2018 did not have a material impact on our consolidated financial statements and related disclosures.

In October 2016, the FASB issued Accounting Standards Update No. 2016-16 (“ASU 2016-16”), Intra-Entity Transfers of Assets Other than Inventory, as part of its simplification initiative. Under the new guidance, an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. Consequently, the amendments in this Update eliminate the exception for an intraentity transfer of an asset other than inventory. ASU 2016-16 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The adoption of this standard on January 1, 2018 did not have a material impact on our consolidated financial statements and related disclosures.

In August 2016, the FASB issued Accounting Standards Update No. 2016‑15 (“ASU 2016‑15”), Classification of Certain Cash Receipts and Cash Payments. ASU 2016‑15 clarifies how certain cash receipts and payments should be presented in the statement of cash flows. The guidance is effective in 2018 with early adoption permitted. The adoption of this standard on January 1, 2018 did not have a material impact on our consolidated financial statements and related disclosures.

In March 2016, the FASB issued Accounting Standards Update No. 2016-09 (“ASU 2016-09”), Compensation-Stock Compensation (Topic 718), as part of its simplification initiative. The areas for simplification in ASU 2016-09 involve several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for periods beginning after December 15, 2016 with early adoption permitted. The adoption of this standard on January 1, 2017 did not have a material impact on our consolidated financial statements and related disclosures.

In November 2015, the FASB issued Accounting Standards Update No. 2015‑17 (“ASU 2015‑17”), Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. ASU 2015‑17 simplifies current guidance and requires companies to classify all deferred tax assets and liabilities as noncurrent on the balance sheet. ASU 2015‑17 can be applied either prospectively or retrospectively and is effective for periods beginning after December 15, 2016, with early adoption permitted. The adoption of this standard on January 1, 2017 did not have a material impact on our consolidated financial statements and related disclosures.

Issued Accounting Pronouncements – Not Yet Adopted

In August 2018, the Securities Exchange Commission (“SEC”) adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders’ equity for interim financial statement. Under the amendments, an analysis of changes in each caption of stockholders’ equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. The Company anticipates its first presentation of changes in stockholders’ equity as required under the new SEC guidance will be included in its Form 10-Q for the three-month period ended March 31, 2019.

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 Company is currently evaluating the impact its adoption may have on its consolidated financial statements.

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 Company does not expect this ASU to have a significant impact on its consolidated financial statements.

In June 2018, the FASB issued Accounting Standards Update No. 2018‑07, (“ASU 2018-07”), Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share‑Based Payment Accounting. 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 Company is currently evaluating the impact that the adoption of ASU 2018‑07 will have on its consolidated financial statements.

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 Company does not expect this ASU to have a significant impact on its consolidated financial statements.

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.

ASU 2016-02 is effective for the Company on January 1, 2019. The Company expects to adopt the new standard on its effective date. A modified retrospective transition approach is required, applying the new standard to all leases existing on the date of initial application. 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 expects to adopt the new standard on January 1, 2019 and use the effective date as our date of initial application. Consequently, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The new standard also provides a number of optional practical expedients in transition. The Company expects to elect 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. The Company is currently evaluating the effect that the new guidance will have on its financial statements and related disclosures and currently believe the most significant effects of the adoption relate to (1) the recognition of new ROU asset and lease liabilities on our balance sheet for our real estate operating leases and (2) providing significant new disclosures for our leasing activities.

ASU 2016-02 also provides practical expedients and certain exemptions for an entity’s ongoing accounting post implementation. The Company currently expects to elect the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, we will not recognize ROU assets or liabilities, and this includes not recognizing ROU assets or liabilities for existing short-term leases of those assets in transition. We also currently expect to elect the practical expedient to not separate lease and non-lease components for all of our leases.We expect to complete our assessment of the full financial impact of ASC 842 during the first quarter of 2019.

LOSS PER SHARE

12 Months Ended

Dec. 31, 2018

LOSS PER SHARE

Earnings Per Share [Text Block]

NOTE 4—LOSS PER SHARE

Basic loss per share (“EPS”) is calculated by dividing net 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 warrants. 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:


	For the year ended December 31,
	2018		2017

	(in thousands, except share and per share amounts)
Net loss (numerator)	$	(43,274)	$	(19,161)
Weighted-average shares (denominator)		28,772,384		19,397,506
Basic and diluted net loss per share	$	(1.50)	$	(0.99)

Potentially dilutive securities outstanding as of December 31, 2018 and 2017 relate to stock options outstanding of 3,357,873 and 2,219,000 shares, respectively.

ACCRUED LIABILITIES

12 Months Ended

Dec. 31, 2018

ACCRUED LIABILITIES

ACCRUED LIABILITIES

NOTE 5—ACCRUED LIABILITIES

Accrued short‑term liabilities are as follows:


	December 31,		December 31,
	2018		2017
	(in thousands)

Accrued milestone payments	$	1,475	$	875
Accrued clinical costs		63		212
Accrued compensation and board fees		1,144		810
Accrued rent		44		—
Other		525		119
Total	$	3,251	$	2,016

LICENSE AGREEMENTS AND COMMITMENTS	12 Months Ended
LICENSE AGREEMENTS AND COMMITMENTS	Dec. 31, 2018
LICENSE AGREEMENTS AND COMMITMENTS
LICENSE AGREEMENTS AND COMMITMENTS	NOTE 6—LICENSE AGREEMENTS AND COMMITMENTS 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 Agreement and the CD33 License Agreement. These license agreements with MSK grant the Company certain patent rights and intellectual property rights. In consideration of obtaining the patent rights and intellectual property rights, 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 Agreement 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 related to certain know‑how to develop, make, and commercialize licensed products and to perform services for all therapeutic and diagnostic uses in the field of cancer diagnostics 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 neuroblastoma and other 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 agreed to provide 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. See further description in note 7, Stockholders’ Equity. 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. Total expensed minimum royalty payments in 2016 under the MSK License Agreement were $1,200,000, upon determination that the payment of such minimum royalties was probable and the amount was estimable in 2016. The accrued minimum royalties were recorded as long‑term accrued liabilities as of December 31, 2018 and 2017. 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 that become due should the Company achieve certain amounts of sales of licensed products resulting from the license arrangement with MSK, with total sales‑based milestones potentially due of $20,000,000. 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 that we receive 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 in the twelve months ended December 31, 2018. The Company expensed $150,000 in milestones in the twelve months ended December 31, 2017. As of both December 31, 2018, and December 31, 2017, $875,000 of accrued milestone obligations were recorded in accrued short‑term liabilities and $300,000 was recorded within accrued long‑term liabilities. These milestone-related charges were recorded as research and development expense upon determination that payment of these clinical milestone obligations was probable after satisfying the financing requirements described herein. 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. Given the uncertainty associated with research and development and the Company’s ability to cancel the MSK License Agreement, such regulatory‑based obligations were determined not to be probable as of December 31, 2018 and 2017, and therefore have not been accrued. CD33 License Agreement On November 13, 2017, we entered into an exclusive license agreement for certain 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 CD33 License Agreement. We are also obligated to pay MSK certain fees under a sponsored research agreement under the CD33 License Agreement. In addition, milestone payments become due upon achievement of the related clinical, regulatory or sales‑based milestone defined in the CD33 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 CD33 License Agreement. Total potential clinical and regulatory milestones potentially due under the CD33 License Agreement are $550,000 and $500,000, respectively. There are also sales‑based milestones that become due should the Company achieve certain amounts of sales of licensed products resulting from the CD33 License Agreement with MSK, with total sales‑based milestones potentially due of $7,500,000. Failure by the Company to meet certain conditions under the CD33 License Agreement could cause the related license to such licensed product to be canceled and could result in termination of the arrangement with MSK. In addition, 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 that we receive 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. In 2017, the total milestone obligations expensed under the CD33 License Agreement with MSK was $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 2017 or 2018, and the total amount of $550,000 was recorded as accrued long‑term liabilities as of December 31, 2018 and December 31, 2017. These milestone‑related charges were recorded as research and development expense in 2017. 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 December 31, 2018 and December 31, 2017 and therefore have not been accrued. MabVax sublicense agreement On June 27, 2018, we entered into a sublicense agreement with MabVax Therapeutics Holding, Inc (“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 bi‑valent ganglioside vaccine, granted to MabVax pursuant to an exclusive license agreement between MabVax and MSK. Under the sublicense agreement, the Company has paid a license fee of $700,000 to MabVax and will pay an additional $600,000 at the first anniversary of the sublicense agreement. The initial license fee of $700,000 was expensed and paid upon execution of the agreement and the continuation fee of $600,000 was accrued in 2018. 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. Research and development is inherently uncertain and as described above, should such research and development fail, the MabVax sublicense agreement is cancelable at the Company’s option. The Company considered risks as well as each party’s termination rights under the MabVax sublicense agreement 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 MabVax sublicense agreement, such obligations were determined not to be probable as of December 31, 2018 and therefore have not been accrued. Other agreements On November 5, 2015, we entered into a sponsored research agreement, which we refer to as the SRA, with MSK pursuant to which we agreed to pay MSK to provide research services over a period of five years related to the intellectual property licensed under the MSK License Agreement. During 2018 and 2017, we incurred research and development expenses of $1,192,000 and $1,160,000, respectively, under the SRA. On September 20, 2016, we entered into a master data services agreement, which we refer to as the MDSA, with MSK pursuant to which we committed to provide make certain payments in exchange for services provided by approximately two 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. On October 11, 2017 the MDSA was amended to increase the resources to approximately three full time employees. During 2018 and 2017, we incurred expenses of $396,000 and $357,000, respectively, under the MDSA. On June 21, 2017, we entered into a master clinical trial agreement, which we refer to as the CTA, with MSK pursuant to which we committed to fund certain clinical trials at MSK. Under the MSK License Agreement, the funding of clinical activities is limited to a five year period. During 2018 and 2017, we incurred research and development expenses of $3,043,000 and $725,000, respectively, under the CTA. On June 27, 2017, we entered into two separate core facility service agreements, which we refer to as the CFSAs, with MSK pursuant to which we committed to obtaining certain laboratory services from MSK. During 2018 and 2017, we incurred research and development expenses of $325,000 and $195,000, respectively, under the CFSAs. On November 13, 2017, we entered into a CD33‑sponsored research agreement, which we refer to as the CD33‑SRA, with MSK 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. During the second half of 2017, we incurred research and development expenses of $88,000 under the CD33‑SRA. During 2018 and 2017, we incurred research and development expenses of $670,000 and $88,000, respectively, under the CD33-SRA. Lease Agreements In 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 further described in footnote 9, Related Party Transactions.

STOCKHOLDERS' EQUITY	12 Months Ended
STOCKHOLDERS' EQUITY	Dec. 31, 2018
STOCKHOLDERS’ EQUITY
STOCKHOLDERS’ EQUITY	NOTE 7—STOCKHOLDERS’ EQUITY Authorized Stock As of December 31, 2018, the Company has authorized a total of 105,500,000 shares, 100,000,000 of which are to be common stock, par value $0.0001 per stock, and 5,500,000 of which are to preferred stock, par value $0.0001 per share. As of December 31, 2017, the Company has authorized a total of 55,500,000 shares, 50,000,000 of which are to be common stock, par value $0.0001 per stock, and 5,500,000 of which are to 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 has issued 34,193,666 shares of its common stock as of December 31, 2018 and 26,749,666 shares of its common stock as of December 31, 2017. Preferred Stock Preferred stock may be issued from time to time in one or more series with such designations, preferences and relative participating, optional or other special rights and qualifications, limitations or restrictions as approved by the Company’s Board of Directors. No preferred stock has been issued as of December 31, 2018 or December 31, 2017. Issuances of common stock for MSK License Agreement In connection with the MSK License Agreement, in August 2015 we issued to MSK 1,428,500 shares of our common stock. We also agreed to provide certain anti‑dilution rights to MSK. If at any time after such issuance, the Company issued any shares of its common stock, the Company was required to issue sufficient shares of common stock to MSK such that at all times prior to the Company obtaining equity financing equal to or greater than $25,000,000 in the aggregate, MSK shall hold shares of the Common Stock of the Company equal to 12.5% of the issued and outstanding shares of common stock. In 2016, our aggregate equity financing reached $25,000,000 since inception, and we issued to MSK an additional 999,929 shares of our common stock in order to maintain MSK’s 12.5% ownership of the Company. The additional shares were issued at the estimated fair market value of such shares at the time of issuance of $4.38 per share, and the total value of $4,380,000 was charged to expense in the period when the anti‑dilution rights were triggered, with $2,280,000 recognized in 2016. Subsequent to the issuance of such shares and upon achievement of the financing requirement, there are no further anti‑dilution rights due to MSK. 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 physicians who were involved in the development of technology licensed from MSK in consideration for their prior service. These two physicians were employees of MSK on the date of grant. The shares are released according to a vesting schedule. A total of 560,000 shares were issued in 2015, with a total of 448,000 shares issued in each of 2016 and 2017. In 2018 a total of 448,000 shares were issued to the two researchers, and upon completion of the IPO we issued an additional 96,000 shares such that one of the two grants was fully issued. The issuance was made pursuant to a stock grant agreement and did not result in proceeds to the Company. A total of 400,000 shares are to be issued in each of 2019 and 2020 to one non-employee physician, 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 of common stock. In August 2016, the Company repurchased and retired a total of 83,600 shares from the two non‑employees of the Company at an amount equal to the estimated fair value of $4.38 per share. The transaction reduced the Company’s shareholders’ equity by $366,000. In April 2018, the Company granted 72,373 common stock options to a non‑employee physician employed by MSK under our 2015 Equity Incentive Plan (the 2015 Plan). The options become exercisable over a four‑year period, with the first twenty‑five percent (25%) exercisable twelve (months) from the date of grant and the remainder becoming exercisable ratably each month over the three years thereafter. The contractual term of the option award is 10 years from the date of grant. The total award was expensed at its estimated fair value in April 2018, as no future service was required by the non‑employee to continue to vest in the option grant. The shares will become immediately exercisable upon the occurrence of a change in control, as defined in the 2015 Plan as further described in footnote 8, Stock Options. Issuance of common stock In September 2018, we completed an initial public offering and issued 6,900,000 shares of Common Stock at a purchase price of $16.00 per share for an aggregate consideration of $99,507,000, net of issuance costs. In November 2017, we issued 3,208,552 shares of Common Stock at a purchase price of $9.35 per share for an aggregate consideration of $28,887,000, net of issuance costs. In October 2017, we issued 5,347,568 shares of Common Stock at a purchase price of $9.35 per share for an aggregate consideration of $49,812,000, net of issuance costs. In January and February 2017, we issued 1,192,662 shares of Common Stock at a purchase price of $8.50 per share for an aggregate consideration of $10,137,000, net of issuance costs.

STOCK OPTIONS

12 Months Ended

Dec. 31, 2018

STOCK OPTIONS

STOCK OPTIONS

NOTE 8—STOCK OPTIONS

2015 Equity Incentive Plan

Our board of directors and stockholders have approved and adopted the 2015 Plan, 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 4,500,000 shares of our common stock are reserved for issuance pursuant to the 2015 Plan. In addition, the number of shares available for issuance under the 2015 Plan will also include an annual increase on the first day of each fiscal year beginning in 2016, equal to 6% 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 2015 Plan vest according to the schedule specified in the grant agreements, which is generally over a four year period and generally become immediately exercisable upon the occurrence of a change in control, as defined. Upon the adoption of the 2018 Equity Incentive Plan in September 2018, no further grants are allowed under the 2015 Equity Incentive 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 over a four year period and generally become immediately exercisable upon the occurrence of a change in control, as defined.

Stock Option Valuation

During the years ended December 31, 2018 and 2017, stock‑based compensation expenses for stock option grants were $1,381,000 and $609,000, respectively, for options granted to employees. During 2018 the expenses were recorded as $276,000 in research and development expense and $1,105,000 in general and administrative expense. During 2017 the expenses were recorded as $167,000 in research and development expense and $442,000 in general and administrative expense. During the year ended December 31, 2018, stock-based compensation for stock option grants was $585,000 in research and development expense for options granted to non-employees. The Company did not grant any options to non‑employees during the year ended December 31, 2017.

The assumptions that the Company used to determine the fair value of the stock options granted to employees and directors were as follows, presented on a weighted average basis:


	Year Ended		Year Ended
	December 31, 2018		December 31, 2017

Risk-free interest rate	2.89	%	2.10	%
Expected term (in years)	6.3		7.0
Expected volatility	57.8	%	58.9	%
Expected dividend yield	—	%	—	%

The assumptions that the Company used to determine the fair value of the stock options granted to non‑employees were as follows, presented on a weighted average basis:


	Year Ended		Year Ended
	December 31, 2018		December 31, 2017

Risk-free interest rate	3.00	%	—	%
Expected term (in years)	10.0		—
Expected volatility	62.7	%	—	%
Expected dividend yield	—	%	—	%

The Company recognizes compensation expense for only the portion of awards that vest.

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, 2017	2,219,000	$	3.21	$	13,626	8.00
Granted	1,138,873	$	16.56
Outstanding and expected to vest at December 31, 2018	3,357,873	$	7.74	$	43,224	7.90
Exercisable at December 31, 2018	1,690,153	$	3.00	$	29,303	6.89

The weighted average grant‑date fair value of stock options granted during the years ended December 31, 2018 and 2017 was $9.58 and $5.59 per share, 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 December 31, 2018, we had $10,848,000 of unrecognized compensation related to employee stock options that are expected to vest over a period of 2.82 years.

RELATED PARTY TRANSACTIONS	12 Months Ended
RELATED PARTY TRANSACTIONS	Dec. 31, 2018
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	NOTE 9—RELATED PARTY TRANSACTIONS MSK is a shareholder of the Company and under the MSK License Agreement, the CD33 License Agreement, CTA, CFAs, SRA and MDSA, we have expensed costs in the total amount of $5,761,000 and $3,730,000 in the years ended December 31, 2018 and 2017, respectively, for milestones, minimum royalties, research and development costs and patent activities. Please refer to footnote 6 for additional details on our various agreements with MSK. As of December 31, 2018 and 2017, we had a total of $4,475,000 and $4,587,000, respectively, recorded as accounts payable and accrued liabilities related to amounts due to MSK. In July 2016, the Company entered into an agreement of lease with a shareholder of the Company, Weco Group, in connection with the subsidiary in Denmark. The lease payable thereunder is approximately $4,000 per month and, as the lease can be terminated with three months’ notice, any future rent commitment thereunder will amount to approximately $12,000. The lease terminated in March 2018, when the Company moved to a new third‑party lease. In addition, the Company has reimbursed Weco Group for certain administrative expenses. The total expenses, including rent, equaled $44,000 and $88,000 during 2018 and 2017, respectively.

INCOME TAXES

12 Months Ended

Dec. 31, 2018

INCOME TAXES

INCOME TAXES

NOTE 10—INCOME TAXES

Domestic and foreign loss before income taxes are as follows:


	For The		For The
	Year Ended		Year Ended
	December 31,		December 31,
	2018		2017
	(thousands)		(thousands)
United States	$	(42,456)	$	(18,975)
Foreign		(818)		(186)
Total	$	(43,274)	$	(19,161)

The Company provided no current and deferred income taxes on net losses of $(43,274,000) and $(19,161,000) for years ended December 31, 2018 and 2017, respectively.

The Tax Cuts and Jobs Act (TCJA) was enacted on December 22, 2017. The TCJA contains significant changes to corporate taxation, including but not limited to, a reduction in the U.S. federal corporate tax rate from a top marginal rate of 35% to 21%, a one‑time mandatory transition tax on accumulated foreign earnings, limitation of the deduction for net operating losses to 80% of annual taxable income while providing that the net operating loss carryovers for years after 2017 will not expire, limitation on the amount of research and development expenses deductible per year beginning in years after 2021 and reduction of the Orphan Drug Credit from 50% to 25% of qualified clinical testing expenditures for years after 2017. The TCJA also made changes to the U.S. federal taxation of foreign earnings and to the timing of recognition of certain revenue and expenses and the deductibility of certain business expenses.

In response to the TCJA, the staff of the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118, (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the TCJA.

As a result of the TCJA being signed into law, the Company recognized a provisional charge of $4,394,000 in the fourth quarter of 2017 related to the re‑measurement of its U.S. deferred tax assets at the lower enacted corporate tax rate. Due to the history of net operating losses, the Company is in a full valuation allowance position. As a result, the additional tax expense due to the TCJA was offset by an equal reduction to the valuation allowance, resulting in no net tax impact from the TCJA to the overall financial condition and results of operations of the Company. The Company was allowed a measurement period of up to one year after the enactment date of the TCJA to finalize the recording of the related tax accounting effects. As of December 31, 2018, the Company had completed its accounting for the effects of the TCJA and no adjustments were recorded to the provisional amount.

The difference between income taxes expected at the U.S. federal statutory income tax rate of 21% and 34% for tax years ended December 31, 2018 and December 31, 2017, respectively, and income taxes provided are set forth below:


	December 31, 2018		December 31, 2017
	(thousands)		(thousands)
Taxes on income at U.S. federal statutory rate	$	(9,127)	$	(6,515)
State and local taxes, net of federal tax effects		(5,778)		(2,152)
Effect of rate change		(9)		4,394
Foreign tax rate differential		(8)		22
Valuation allowance		16,376		5,196
Tax credits		(1,431)		(958)
Other		(23)		13
Total		—		—

For the year ended December 31, 2017, as a result of the enactment of the Tax Cuts and Jobs Act, there was no impact to our financial position or results associated with a write‑off of deferred tax assets due to the rate change from 34% to 21% and their associated valuation allowance, and a one‑time mandatory transition tax.

Significant components of the Company’s net deferred tax assets/(liabilities) are as follows:


	December 31, 2018		December 31, 2017
	(thousands)		(thousands)
Deferred tax assets/(liabilities):
Acquired Intangibles	$	2,682	$	2,381
Accrued bonus		—		200
Unrealized foreign exchange loss		(163)		187
Accrued royalty		415		414
Stock based compensation		981		300
Net operating loss carryforwards		25,285		10,847
Tax credit carryforwards		2,789		1,358
Other		78		—
Total deferred tax assets/(liabilities)		32,067		15,687
Valuation allowance		(32,067)		(15,687)
Net deferred tax assets/(liabilities)		—		—

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 December 31, 2018, and 2017, the Company has determined that there were no uncertain tax positions. The Company’s tax returns for years 2017, 2016 and 2015 are open for tax examination by U.S. federal and state, and the Danish tax authorities.

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 loss 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.

As of December 31, 2018, the Company had U.S. federal and state and local net operating loss (“NOL”) carryforwards of approximately $72,323,000, which are available to reduce future taxable income. The Company also had U.S. federal tax credits of $2,789,000 as of December 31, 2018, which may be used to offset future tax liabilities. The NOL and tax credit carryforwards will begin to expire in 2035. The NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986 (“IRC”). The Company has performed an analysis of its Section 382 ownership changes through December 31, 2018. Due to the large annual limitation, the Company believes that it is more likely than not that none of the net operating loss carryforwards will expire as a result of the limitation from the ownership change under Section 382. The Company also has Danish NOL carryforwards of $1,154,000, which have an indefinite carryforward period.

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)

12 Months Ended

Dec. 31, 2018

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)

NOTE 13—QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)


(In thousands, except per share amounts)	2018
	March 31		June 30		September 30		December 31

Loss from operations	$	(7,479)	$	(10,258)	$	(11,415)	$	(14,078)
Net loss		(7,483)		(10,305)		(11,426)		(14,060)
Net loss per share - basic and diluted	$	(0.28)	$	(0.38)	$	(0.42)	$	(0.42)


	2017
	March 31		June 30		September 30		December 31

Loss from operations	$	(2,897)	$	(3,230)	$	(3,842)	$	(9,275)
Net loss		(2,890)		(3,191)		(3,827)		(9,253)
Net loss per share - basic and diluted	$	(0.16)	$	(0.18)	$	(0.21)	$	(0.44)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2018

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates

Cash, Cash Equivalents, and Restricted Cash

Cash and Cash Equivalents

The Company considers all highly‑liquid investments with maturities of three months or less from date of purchase to be cash equivalents.

Restricted cash represents a bank account with funds to cover the Company’s corporate credit card availability.

Property and Equipment


		Estimated Useful Life
Furniture and fixtures		5 years
Leasehold improvements		Shorter of life of lease or 15 years

Depreciation and amortization expense on property and equipment was $29,000 and $0 for the years ended December 31, 2018 and 2017, respectively.

Impairment of Long-Lived Assets

Impairment of Long‑Lived Assets

Deferred Offering Costs

Income Taxes

The Company’s policy is to recognize, when applicable, interest and penalties on uncertain tax positions as part of income tax expense.

Research and Development Costs

Patent Costs

The Company expenses the costs of obtaining and maintaining patents as general and administrative expenses.

Stock-Based Compensation

Stock‑Based Compensation

Segment Information

Comprehensive Loss

Foreign Currency

Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements - Adopted

Issued Accounting Pronouncements – Not Yet Adopted

LOSS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2018

LOSS PER SHARE

Schedule of basic and diluted net loss per share


	For the year ended December 31,
	2018		2017

	(in thousands, except share and per share amounts)
Net loss (numerator)	$	(43,274)	$	(19,161)
Weighted-average shares (denominator)		28,772,384		19,397,506
Basic and diluted net loss per share	$	(1.50)	$	(0.99)

ACCRUED LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2018

ACCRUED LIABILITIES

Summary of accrued short-term liabilities


	December 31,		December 31,
	2018		2017
	(in thousands)

Accrued milestone payments	$	1,475	$	875
Accrued clinical costs		63		212
Accrued compensation and board fees		1,144		810
Accrued rent		44		—
Other		525		119
Total	$	3,251	$	2,016

STOCK OPTIONS (Tables)

12 Months Ended

Dec. 31, 2018

Stock Options

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, 2017	2,219,000	$	3.21	$	13,626	8.00
Granted	1,138,873	$	16.56
Outstanding and expected to vest at December 31, 2018	3,357,873	$	7.74	$	43,224	7.90
Exercisable at December 31, 2018	1,690,153	$	3.00	$	29,303	6.89

Employees

Stock Options

Schedule of assumptions that Company used to determine the fair value of the stock options granted


	Year Ended		Year Ended
	December 31, 2018		December 31, 2017

Risk-free interest rate	2.89	%	2.10	%
Expected term (in years)	6.3		7.0
Expected volatility	57.8	%	58.9	%
Expected dividend yield	—	%	—	%

Nonemployees

Stock Options

Schedule of assumptions that Company used to determine the fair value of the stock options granted


	Year Ended		Year Ended
	December 31, 2018		December 31, 2017

Risk-free interest rate	3.00	%	—	%
Expected term (in years)	10.0		—
Expected volatility	62.7	%	—	%
Expected dividend yield	—	%	—	%

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2018

INCOME TAXES

Schedule of domestic and foreign loss before income taxes


	For The		For The
	Year Ended		Year Ended
	December 31,		December 31,
	2018		2017
	(thousands)		(thousands)
United States	$	(42,456)	$	(18,975)
Foreign		(818)		(186)
Total	$	(43,274)	$	(19,161)

Schedule of difference between incomes taxes expected at U.S. federal statutory income tax rate and income taxes


	December 31, 2018		December 31, 2017
	(thousands)		(thousands)
Taxes on income at U.S. federal statutory rate	$	(9,127)	$	(6,515)
State and local taxes, net of federal tax effects		(5,778)		(2,152)
Effect of rate change		(9)		4,394
Foreign tax rate differential		(8)		22
Valuation allowance		16,376		5,196
Tax credits		(1,431)		(958)
Other		(23)		13
Total		—		—

Schedule of significant components of net deferred tax assets/(liabilities)


	December 31, 2018		December 31, 2017
	(thousands)		(thousands)
Deferred tax assets/(liabilities):
Acquired Intangibles	$	2,682	$	2,381
Accrued bonus		—		200
Unrealized foreign exchange loss		(163)		187
Accrued royalty		415		414
Stock based compensation		981		300
Net operating loss carryforwards		25,285		10,847
Tax credit carryforwards		2,789		1,358
Other		78		—
Total deferred tax assets/(liabilities)		32,067		15,687
Valuation allowance		(32,067)		(15,687)
Net deferred tax assets/(liabilities)		—		—

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)

Schedule of quarterly consolidated financial data


(In thousands, except per share amounts)	2018
	March 31		June 30		September 30		December 31

Loss from operations	$	(7,479)	$	(10,258)	$	(11,415)	$	(14,078)
Net loss		(7,483)		(10,305)		(11,426)		(14,060)
Net loss per share - basic and diluted	$	(0.28)	$	(0.38)	$	(0.42)	$	(0.42)


	2017
	March 31		June 30		September 30		December 31

Loss from operations	$	(2,897)	$	(3,230)	$	(3,842)	$	(9,275)
Net loss		(2,890)		(3,191)		(3,827)		(9,253)
Net loss per share - basic and diluted	$	(0.16)	$	(0.18)	$	(0.21)	$	(0.44)

BASIS OF PRESENTATION (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
BASIS OF PRESENTATION
Accumulated deficit	$ 84,835	$ 41,561
Cash and cash equivalents	$ 147,840	$ 90,483

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Depreciation and amortization expense	$ 29,000	$ 0
Furniture and fixtures
Property and Equipment
Estimated Useful Life	5 years
Leasehold improvements \| Maximum
Property and Equipment
Estimated Useful Life	15 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Deferred offering costs		$ 772,000
Deferred offering costs included in accounts payable and accrued liabilities		200,000
Research and development	$ 34,269,000	14,307,000
Number of operating segments \| segment	1
Foreign currency transaction gains and losses	$ (97,000)	$ 63,000

LOSS PER SHARE - Basic and diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
LOSS PER SHARE
Net loss (numerator)	$ (14,060)	$ (11,426)	$ (10,305)	$ (7,483)	$ (9,253)	$ (3,827)	$ (3,191)	$ (2,890)	$ (43,274)	$ (19,161)
Weighted average common shares outstanding, basic and diluted (denominator)									28,772,384	19,397,506
Basic and diluted net loss per share (in dollars per share)	$ (0.42)	$ (0.42)	$ (0.38)	$ (0.28)	$ (0.44)	$ (0.21)	$ (0.18)	$ (0.16)	$ (1.50)	$ (0.99)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued short term liabilities
Accrued milestone payments	$ 1,475	$ 875
Accrued clinical costs	63	212
Accrued compensation and board fees	1,144	810
Accrued rent	44
Other	525	119
Total	$ 3,251	$ 2,016

LICENSE AGREEMENTS AND COMMITMENTS - MSK License Agreement (Details) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 20, 2015	Aug. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Agreements
Accrued milestone payments, current			$ 1,475,000	$ 875,000
MSK License Agreement
Agreements
Issuance of common stock to strategic partner (in shares)	1,428,500	1,428,500			999,929
Annual minimum royalties payable from fifth anniversary	$ 80,000
Expensed minimum royalty payments					$ 1,200,000
Clinical milestones potentially due	2,450,000
Regulatory milestones potentially due	9,000,000
Sales-based milestones potentially due	$ 20,000,000
Clinical milestone expense			0	150,000
MSK License Agreement \| Accrued short-term liabilities
Agreements
Accrued milestone payments, current			875,000	875,000
MSK License Agreement \| Accrued long-term liabilities
Agreements
Accrued milestone payments, noncurrent			$ 300,000	$ 300,000

LICENSE AGREEMENTS AND COMMITMENTS - CD33 License Agreement (Details) - CD33 License Agreement - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Nov. 13, 2017
Agreements
Annual minimum royalties payable			$ 40,000
Annual minimum royalties payable from tenth anniversary			60,000
Clinical milestones potentially due			550,000
Regulatory milestones potentially due			500,000
Sales-based milestones potentially due			$ 7,500,000
Clinical milestone expense		$ 550,000
Clinical milestone payment	$ 0	0
Accrued long-term liabilities
Agreements
Accrued milestone payments, noncurrent	$ 550,000	$ 550,000

LICENSE AGREEMENTS AND COMMITMENTS - MabVax sublicense agreement (Details) - MabVax sublicense agreement - USD ($)		12 Months Ended
	Jun. 27, 2018	Dec. 31, 2018
Agreements
License fee paid	$ 700,000
Additional license fee payable at first anniversary	600,000
License fee expense		$ 700,000
Continuation fee		$ 600,000
Development milestone payments due	$ 1,400,000

LICENSE AGREEMENTS AND COMMITMENTS - Other agreements (Details)							6 Months Ended	12 Months Ended
	Nov. 13, 2017	Oct. 11, 2017 employee	Jun. 27, 2017 agreement	Jun. 21, 2017	Sep. 20, 2016 employee	Nov. 05, 2015	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Agreements
Research and development								$ 34,269,000	$ 14,307,000
SRA
Agreements
Research service period						5 years
Research and development								1,192,000	1,160,000
MDSA
Agreements
Research and development								396,000	357,000
Number of full-time employees \| employee		3			2
CTA
Agreements
Research service period				5 years
Research and development								3,043,000	725,000
CFAs
Agreements
Number of core facility service agreements \| agreement			2
Research and development								325,000	195,000
CD33-SRA
Agreements
Research service period	2 years
Research and development							$ 88,000	$ 670,000	$ 88,000

LICENSE AGREEMENTS AND COMMITMENTS - Lease agreements (Details) - USD ($)	Feb. 28, 2018	Jan. 31, 2018
Corporate headquarters, New York
Agreements
Lease term		5 years
Fixed rent payable per annum		$ 384,000
Lease payable per month		$ 32,000
Office space, Denmark
Agreements
Lease term	3 years
Lease payable per month	$ 19,000

STOCKHOLDERS' EQUITY - Authorized, Common and Preferred Stock (Details)	12 Months Ended
	Dec. 31, 2018 Vote $ / shares shares	Dec. 31, 2017 $ / shares shares
STOCKHOLDERS’ EQUITY
Total shares authorized	105,500,000	55,500,000
Common stock, authorized shares	100,000,000	50,000,000
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
Common stock, shares issued	34,193,666	26,749,666
Preferred stock, shares issued	0	0

STOCKHOLDERS' EQUITY - MSK License Agreement (Details) - MSK License Agreement - USD ($)		1 Months Ended	12 Months Ended
	Aug. 20, 2015	Aug. 31, 2015	Dec. 31, 2016
Agreements
Issuance of common stock to strategic partner (in shares)	1,428,500	1,428,500	999,929
Maximum amount of equity financing for anti-dilution rights		$ 25,000,000	$ 25,000,000
Ownership percentage of the issued and outstanding shares of common stock to be held prior to entity reaching equity financing threshold		12.50%	12.50%
Share price (in dollars per share)			$ 4.38
Share issuance charged to expenses			$ 4,380,000
Non-cash expense in connection with equity issuance to strategic partner			$ 2,280,000

STOCKHOLDERS' EQUITY - Stock grant agreements with non-employees (Details)	1 Months Ended		12 Months Ended
	Aug. 31, 2016 USD ($) individual $ / shares shares	Aug. 31, 2015 individual shares	Dec. 31, 2020 individual shares	Dec. 31, 2019 individual shares	Dec. 31, 2018 item individual shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares	Dec. 31, 2015 shares
Stock grant agreements with non-employees
Agreements
Shares agreed to be issued		2,800,000
Number of non-employee physicians \| individual	2	2			2
Issuance of common stock to nonemployees (in shares)					448,000	448,000	448,000	560,000
Shares repurchased and retired	83,600
Estimated fair value of stock repurchased and retired (in dollars per share) \| $ / shares	$ 4.38
Reduction in equity \| $	$ 366,000
Stock grant agreements with non-employees \| Forecast
Agreements
Number of non-employee physicians \| individual			1	1
Issuance of common stock to nonemployees (in shares)			400,000	400,000
Stock grant agreements with non-employees, completion of IPO
Agreements
Issuance of common stock to nonemployees (in shares)					96,000
Number of stock grants fully issued \| item					1
Number of stock grants \| item					2

STOCKHOLDERS' EQUITY - Stock options (Details) - shares	1 Months Ended	12 Months Ended
STOCKHOLDERS' EQUITY - Stock options (Details) - shares	Apr. 30, 2018	Dec. 31, 2018
Stock Options
Granted (in shares)		1,138,873
2015 Equity Incentive Plan \| Nonemployees
Stock Options
Granted (in shares)	72,373
Vesting period	4 years
Term of award	10 years
2015 Equity Incentive Plan \| Nonemployees \| Tranche one
Stock Options
Vesting period	12 months
Vesting (as a percent)	25.00%
2015 Equity Incentive Plan \| Nonemployees \| Tranche two
Stock Options
Vesting period	3 years

STOCKHOLDERS' EQUITY - Issuance of common stock (Details) - USD ($)	1 Months Ended			2 Months Ended	12 Months Ended
	Sep. 30, 2018	Nov. 30, 2017	Oct. 31, 2017	Feb. 28, 2017	Dec. 31, 2018	Dec. 31, 2017
Issuance of common stock
Proceeds from issuance of common stock, net of issuance costs					$ 99,765,000	$ 89,844,000
IPO
Issuance of common stock
Shares issued	6,900,000
Share price (in dollars per share)	$ 16.00
Proceeds from issuance of common stock, net of issuance costs	$ 99,507,000
Investors
Issuance of common stock
Shares issued		3,208,552	5,347,568	1,192,662
Share price (in dollars per share)		$ 9.35	$ 9.35	$ 8.50
Proceeds from issuance of common stock, net of issuance costs		$ 28,887,000	$ 49,812,000	$ 10,137,000

STOCK OPTIONS - Equity Incentive Plan (Details) - 2015 Equity Incentive Plan	8 Months Ended
	Aug. 31, 2018 shares
Stock Options
Shares reserved for issuance pursuant to the plan	4,500,000
Annual increase on share reserve (as a percent)	6.00%
Stock options \| Employees and nonemployees owning less than 10% of voting power
Stock Options
Term of award	10 years
Vesting period	4 years
Stock options \| Employee owning more than 10% of voting power \| Minimum
Stock Options
Ownership (as a percent)	10.00%
Option price as percentage of fair market value of common stock on the date of grant	110.00%
Stock options \| Participants owning more than 10% of voting power
Stock Options
Term of award	5 years

STOCK OPTIONS - 2018 Equity Incentive Plan (Details) - 2018 Equity Incentive Plan	1 Months Ended
	Sep. 30, 2018 shares
Stock Options
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
Stock Options
Term of award	10 years
Vesting period	4 years
Stock options \| Participants owning more than 10% of voting power
Stock Options
Term of award	5 years
Stock options \| Employee owning more than 10% of voting power \| Minimum
Stock Options
Ownership (as a percent)	10.00%
Option price as percentage of fair market value of common stock on the date of grant	110.00%

STOCK OPTIONS - Expense (Details) - USD ($)	1 Months Ended	12 Months Ended
STOCK OPTIONS - Expense (Details) - USD ($)	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Stock Options
Options granted (in shares)		1,138,873
Employees \| Research and development expense
Stock Options
Stock-based compensation expenses		$ 276,000	$ 167,000
Employees \| General and administrative expense
Stock Options
Stock-based compensation expenses		1,105,000	442,000
Nonemployees \| Research and development expense
Stock Options
Stock-based compensation expenses		585,000
Stock options \| Employees
Stock Options
Stock-based compensation expenses		$ 1,381,000	$ 609,000
2015 Equity Incentive Plan \| Nonemployees
Stock Options
Options granted (in shares)	72,373

STOCK OPTIONS - Stock Option Valuation (Details) - Stock options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employees
Stock Option Valuation
Risk-free interest rate	2.89%	2.10%
Expected term (in years)	6 years 3 months 18 days	7 years
Expected volatility	57.80%	58.90%
Nonemployees
Stock Option Valuation
Risk-free interest rate	3.00%
Expected term (in years)	10 years
Expected volatility	62.70%

STOCK OPTIONS - Common stock options issued and outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Options
Outstanding at beginning of period (in shares)	2,219,000
Granted (in shares)	1,138,873
Outstanding at end of period (in shares)	3,357,873	2,219,000
Exercisable at end of period (in shares)	1,690,153
Weighted average exercise price
Outstanding at beginning of period (in dollars per share)	$ 3.21
Granted (in dollars per share)	16.56
Outstanding at end of period (in dollars per share)	7.74	$ 3.21
Exercisable at end of period (in dollars per share)	$ 3.00
Aggregate intrinsic value and Weighted average remaining contractual life (years)
Outstanding (in dollars)	$ 43,224	$ 13,626
Exercisable (in dollars)	$ 29,303
Outstanding (in years)	7 years 10 months 24 days	8 years
Exercisable (in years)	6 years 10 months 21 days
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 9.58	$ 5.59

STOCK OPTIONS - Unrecognized compensation (Details) - Stock options - Employees	12 Months Ended
	Dec. 31, 2018 USD ($)
Unrecognized compensation related to employee stock options
Unrecognized compensation	$ 10,848,000
Expected to vest over period	2 years 9 months 26 days

RELATED PARTY TRANSACTIONS (Details) - USD ($)	1 Months Ended	12 Months Ended
RELATED PARTY TRANSACTIONS (Details) - USD ($)	Jul. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
MSK \| MSK License Agreement, the CD33 License Agreement, CTA, CFAs, SRA and MDSA
Related party transactions
Expenses		$ 5,761,000	$ 3,730,000
Due to related parties		4,475,000	4,587,000
Weco Group \| Lease Agreement
Related party transactions
Expenses		$ 44,000	$ 88,000
Lease payable per month	$ 4,000
Notice period to terminate lease	3 months
Future rent commitment	$ 12,000

INCOME TAXES - Income (Loss) Before Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Domestic and foreign loss before income taxes:
United States	$ (42,456,000)	$ (18,975,000)
Foreign	(818,000)	(186,000)
Total losses before taxes	(43,274,000)	(19,161,000)
Income tax expense
Current income taxes	0	0
Deferred income taxes	$ 0	$ 0

INCOME TAXES - Tax Cuts and Jobs Act (TCJA) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
U.S. federal corporate tax rate (as a percent)		21.00%	34.00%
Limitation of deduction for net operating losses as percentage of annual taxable income		80.00%
Orphan Drug Credit (as a percent)		25.00%	50.00%
Provisional charge	$ 4,394,000
Maximum
U.S. federal corporate tax rate (as a percent)			35.00%

INCOME TAXES - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Difference between income taxes expected at U.S. federal statutory income tax rate and income taxes provided:
Taxes on income at U.S. federal statutory rate	$ (9,127)	$ (6,515)
State and local taxes, net of federal tax effects	(5,778)	(2,152)
Effect of rate change	(9)	4,394
Foreign tax rate differential	(8)	22
Valuation allowance	16,376	5,196
Tax credits	(1,431)	(958)
Other	$ (23)	$ 13
U.S. federal corporate tax rate (as a percent)	21.00%	34.00%

INCOME TAXES - Components of Deferred Tax Assets/(Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets/(liabilities)::
Acquired Intangibles	$ 2,682	$ 2,381
Accrued bonus		200
Unrealized foreign exchange (gain)	(163)
Unrealized foreign exchange loss		187
Accrued royalty	415	414
Stock based compensation	981	300
Net operating loss carryforwards	25,285	10,847
Tax credit carryforwards	2,789	1,358
Other	78
Total deferred tax assets/(liabilities)	32,067	15,687
Valuation allowance	$ (32,067)	$ (15,687)

SUBSEQUENT EVENTS (Details) - Subsequent Event	Feb. 28, 2019 USD ($) ft²
Subsequent Events
Lease term	3 years
Leased area (in square feet) \| ft²	4,500
Lease payable per month \| $	$ 12,000

QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
QUARTERLY CONSOLIDATED FINANCIAL DATA (unaudited)
Loss from operations	$ (14,078)	$ (11,415)	$ (10,258)	$ (7,479)	$ (9,275)	$ (3,842)	$ (3,230)	$ (2,897)	$ (43,230)	$ (19,244)
Net loss	$ (14,060)	$ (11,426)	$ (10,305)	$ (7,483)	$ (9,253)	$ (3,827)	$ (3,191)	$ (2,890)	$ (43,274)	$ (19,161)
Basic and diluted net loss per share (in dollars per share)	$ (0.42)	$ (0.42)	$ (0.38)	$ (0.28)	$ (0.44)	$ (0.21)	$ (0.18)	$ (0.16)	$ (1.50)	$ (0.99)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

OTHER BENEFITS	12 Months Ended
OTHER BENEFITS	Dec. 31, 2018
OTHER BENEFITS
OTHER BENEFITS	NOTE 11—OTHER BENEFITS 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. Contributions from our Danish subsidiary were immaterial during the years ended December 31, 2018 and 2017. 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. On October 1, 2018, the Company 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 years ended December 31, 2018 and December 31, 2017.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2018
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 12—SUBSEQUENT EVENTS In February 2019, the Company entered a three year lease for a 4,500 square feet laboratory lease in Nutley, New Jersey. Monthly lease payments are approximately $12,000 per month during the lease term.

ORGANIZATION AND DESCRIPTION OF BUSINESS (Details)	12 Months Ended
ORGANIZATION AND DESCRIPTION OF BUSINESS (Details)	Dec. 31, 2018 agreement
ORGANIZATION AND DESCRIPTION OF BUSINESS
Number of product development programs for which entity has obtained exclusive rights	2

LICENSE AGREEMENTS AND COMMITMENTS (Details)	Dec. 31, 2018 agreement
LICENSE AGREEMENTS AND COMMITMENTS
Number of license agreements	2

INCOME TAXES - Net Operating Loss Carryforwards (Details)	Dec. 31, 2018 USD ($)
U.S. federal and state and local
Operating Loss Carryforwards
Net operating loss carryforwards	$ 72,323,000
Danish
Operating Loss Carryforwards
Net operating loss carryforwards	$ 1,154,000

INCOME TAXES - Tax Credit Carryforwards (Details)	Dec. 31, 2018 USD ($)
U.S. federal
Tax Credit Carryforward [Line Items]
Tax credit	$ 2,789,000

OTHER BENEFITS (Details)	12 Months Ended
OTHER BENEFITS (Details)	Dec. 31, 2018	Dec. 31, 2017
OTHER BENEFITS
Employer matching contribution to defined contribution plan (as a percent)	0.00%	0.00%