Celldex Therapeutics (CLDX) 10-Q 9 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 31, 2021
Document and Entity Information
Document Type	10-Q
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	000-15006
Entity Registrant Name	CELLDEX THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3191702
Entity Address, Address Line One	Perryville III Building
Entity Address, Address Line Two	53 Frontage Road
Entity Address, Address Line Three	Suite 220
Entity Address, City or Town	Hampton
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08827
City Area Code	908
Local Phone Number	200-7500
Title of 12(b) Security	Common Stock, par value $.001
Trading Symbol	CLDX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		46,663,872
Entity Central Index Key	0000744218
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Quarterly Report	true

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 72,184	$ 43,836
Marketable securities	350,905	150,586
Accounts and other receivables	197	1,802
Prepaid and other current assets	3,269	1,619
Total current assets	426,555	197,843
Property and equipment, net	3,342	3,815
Operating lease right-of-use assets, net	3,016	3,449
Intangible assets, net	27,190	30,690
Other assets	98	41
Total assets	460,201	235,838
Current liabilities:
Accounts payable	836	1,048
Accrued expenses	10,253	8,459
Current portion of operating lease liabilities	1,366	1,327
Current portion of other long-term liabilities	1,721	3,372
Total current liabilities	14,176	14,206
Long-term portion of operating lease liabilities	1,713	2,154
Other long-term liabilities	7,600	10,121
Total liabilities	23,489	26,481
Commitments and contingent liabilities
Stockholders' equity:
Convertible preferred stock, $.01 par value; 3,000,000 shares authorized; no shares issued and outstanding at September 30, 2021 and December 31, 2020
Common stock, $.001 par value; 297,000,000 shares authorized; 46,663,340 and 39,603,771 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively	47	40
Additional paid-in capital	1,557,576	1,279,824
Accumulated other comprehensive income	2,548	2,589
Accumulated deficit	(1,123,459)	(1,073,096)
Total stockholders' equity	436,712	209,357
Total liabilities and stockholders' equity	$ 460,201	$ 235,838

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
CONDENSED CONSOLIDATED BALANCE SHEETS
Convertible Preferred Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Convertible Preferred Stock, Shares Authorized	3,000,000	3,000,000
Convertible Preferred Stock, Shares Issued	0	0
Convertible Preferred Stock, Shares Outstanding	0	0
Common Stock, Par Value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, Shares Authorized	297,000,000	297,000,000
Common Stock, Shares Issued	46,663,340	39,603,771
Common Stock, Shares Outstanding	46,663,340	39,603,771

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 153	$ 668	$ 4,317	$ 3,633
Operating expenses:
Research and development	13,557	10,708	38,633	32,109
General and administrative	5,821	3,640	14,247	10,833
Intangible asset impairment	3,500		3,500	3,500
(Gain) loss on fair value remeasurement of contingent consideration	(1,901)	662	(1,160)	(4,236)
Total operating expenses	20,977	15,010	55,220	42,206
Operating loss	(20,824)	(14,342)	(50,903)	(38,573)
Investment and other income, net	145	118	313	465
Net loss before income tax benefit	(20,679)	(14,224)	(50,590)	(38,108)
Income tax benefit	227		227	228
Net loss	$ (20,452)	$ (14,224)	$ (50,363)	$ (37,880)
Basic and diluted net loss per common share	$ (0.45)	$ (0.36)	$ (1.21)	$ (1.44)
Shares used in calculating basic and diluted net loss per share	45,453	39,278	41,582	26,303
Comprehensive loss:
Net loss	$ (20,452)	$ (14,224)	$ (50,363)	$ (37,880)
Other comprehensive income (loss):
Unrealized (loss) gain on marketable securities	(44)	14	(41)	(11)
Comprehensive loss	(20,496)	(14,210)	(50,404)	(37,891)
Product development and licensing agreements
Revenues:
Total revenues		12	29	2,297
Contracts and grants
Revenues:
Total revenues	$ 153	$ 656	$ 4,288	$ 1,336

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOW - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (50,363)	$ (37,880)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,291	3,174
Amortization and premium of marketable securities, net	(3,407)	(422)
Gain on sale or disposal of assets	(23)	(29)
Intangible Asset Impairment	3,500	3,500
Gain on fair value remeasurement of contingent consideration	(1,160)	(4,236)
Non-Cash Income Tax Benefit	(227)	(228)
Stock-based compensation expense	5,813	2,658
Changes in operating assets and liabilities:
Accounts and other receivables	1,549	177
Prepaid and other current assets	(2,261)	(1,280)
Accounts payable and accrued expenses	1,757	864
Other liabilities	(3,855)	(1,491)
Net cash used in operating activities	(46,386)	(35,193)
Cash flows from investing activities:
Sales and maturities of marketable securities	129,000	55,600
Purchases of marketable securities	(325,342)	(183,394)
Acquisition of property and equipment	(895)	(1,305)
Proceeds from sale or disposal of assets	25	29
Net cash used in investing activities	(197,212)	(129,070)
Cash flows from financing activities:
Net proceeds from stock issuances	269,893	170,964
Proceeds from issuance of stock from employee benefit plans	2,053	218
Issuance of Term Loan		2,962
Payment of Term Loan		(2,962)
Net cash provided by financing activities	271,946	171,182
Net increase in cash and cash equivalents	28,348	6,919
Cash and cash equivalents at beginning of period	43,836	11,232
Cash and cash equivalents at end of period	72,184	18,151
Non-cash investing activities
Accrued construction in progress	$ 46	$ 63

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2021
Basis of Presentation
Basis of Presentation	(1) Basis of Presentation ​ The accompanying unaudited condensed consolidated financial statements have been prepared by Celldex Therapeutics, Inc. (the “Company” or “Celldex”) in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and reflect the operations of the Company and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. ​ These interim financial statements do not include all the information and footnotes required by U.S. GAAP for annual financial statements and should be read in conjunction with the audited financial statements for the year ended December 31, 2020, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 29, 2021. In the opinion of management, the interim financial statements reflect all normal recurring adjustments necessary to fairly state the Company’s financial position and results of operations for the interim periods presented. The year-end condensed balance sheet data presented for comparative purposes was derived from audited financial statements but does not include all disclosures required by U.S. GAAP. ​ The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for any future interim period or the fiscal year ending December 31, 2021. ​ At September 30, 2021, the Company had cash, cash equivalents and marketable securities of $423.1 million. The Company has had recurring losses and incurred a loss of $50.4 million for the nine months ended September 30, 2021. Net cash used in operations for the nine months ended September 30, 2021 was $46.4 million. The Company believes that the cash, cash equivalents and marketable securities at the filing date of this Form 10-Q will be sufficient to meet estimated working capital requirements and fund planned operations for at least the next twelve months from the date of issuance of these financial statements. ​ During the next twelve months and beyond, the Company may take further steps to raise additional capital to meet its long-term liquidity needs including, but not limited to, one or more of the following: the licensing of drug candidates with existing or new collaborative partners, possible business combinations, issuance of debt, or the issuance of common stock or other securities via private placements or public offerings. Although the Company has been successful in raising capital in the past, there can be no assurance that additional financing will be available on acceptable terms, if at all, and the Company’s negotiating position in capital-raising efforts may worsen as existing resources are used. There is also no assurance that the Company will be able to enter into further collaborative relationships. Additional equity financings may be dilutive to the Company’s stockholders; debt financing, if available, may involve significant cash payment obligations and covenants that restrict the Company’s ability to operate as a business; and licensing or strategic collaborations may result in royalties or other terms which reduce the Company’s economic potential from products under development. The Company’s ability to continue funding its planned operations beyond twelve months from the issuance date is also dependent on the timing and manner of payment of contingent milestones from the acquisition of Kolltan Pharmaceuticals, Inc. (“Kolltan”), in the event that the Company achieves the drug candidate milestones related to those payments. The Company, at its option, may decide to pay those milestone payments in cash, shares of its common stock or a combination thereof. If the Company is unable to raise the funds necessary to meet its long-term liquidity needs, it may have to delay or discontinue the development of one or more programs, discontinue or delay ongoing or anticipated clinical trials, license out programs earlier than expected, raise funds at a significant discount or on other unfavorable terms, if at all, or sell all or a part of the Company. ​ The COVID-19 pandemic continues to have a major impact in the US and around the world. The availability of vaccines holds promise for the future, though new variants of the virus and potential waning immunity from vaccines may result in continued impact from this pandemic in the future, including supply chain and work force issues which could adversely impact our operations. To date, the Company has managed delays and disruptions without significant impact in planned and ongoing preclinical and clinical trials, manufacturing or shipping. Potential impacts to our business include delays in planned and ongoing preclinical and clinical trials including enrollment of patients, disruptions in time and resources provided by independent clinical investigators, contract research organizations, and other third-party service providers, temporary closures of our facilities, disruptions or restrictions on our employees’ ability to travel, and delays in manufacturing and/or shipments to and from third-party suppliers and contract manufacturers for APIs and drug product. Any prolonged negative impacts to our business could materially impact our operating results and could lead to impairments of our Intangible in-process research and development (“IPR&D”) assets with a carrying value of $27.2 million at September 30, 2021.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Significant Accounting Policies
Significant Accounting Policies	(2) Significant Accounting Policies ​ The significant accounting policies used in preparation of these condensed consolidated financial statements on Form 10-Q for the three and nine months ended September 30, 2021 are consistent with those discussed in Note 2 to the financial statements in our Annual Report on Form 10-K for the year ended December 31, 2020. ​ Recent Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements upon adoption. ​ In June 2016, the FASB issued guidance on the Measurement of Credit Losses on Financial Instruments. The guidance requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, the standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard will be effective for the Company on January 1, 2023. We are currently evaluating the potential impact that this standard may have on the Company’s consolidated financial statements and related disclosures. ​ ​

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Measurements
Fair Value Measurements	(3) Fair Value Measurements ​ The following tables set forth the Company’s financial assets and liabilities subject to fair value measurements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 66,929 ​ ​ — ​ $ 66,929 ​ ​ — Marketable securities ​ ​ 350,905 ​ ​ — ​ ​ 350,905 ​ ​ — ​ ​ $ 417,834 ​ ​ — ​ $ 417,834 ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Kolltan acquisition contingent consideration ​ $ 7,107 ​ ​ — ​ ​ — ​ $ 7,107 ​ ​ $ 7,107 ​ ​ — ​ ​ — ​ $ 7,107 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 35,066 ​ ​ — ​ $ 35,066 ​ ​ — Marketable securities ​ ​ 150,586 ​ ​ — ​ ​ 150,586 ​ ​ — ​ ​ $ 185,652 ​ ​ — ​ $ 185,652 ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Kolltan acquisition contingent consideration ​ $ 8,267 ​ ​ — ​ ​ — ​ $ 8,267 ​ ​ $ 8,267 ​ ​ — ​ ​ — ​ $ 8,267 ​ The Company’s financial assets consist mainly of money market funds, cash equivalents and marketable securities and are classified as Level 2 within the valuation hierarchy. The Company values its marketable securities utilizing independent pricing services which normally derive security prices from recently reported trades for identical or similar securities, making adjustments based on significant observable transactions. At each balance sheet date, observable market inputs may include trade information, broker or dealer quotes, bids, offers or a combination of these data sources. ​ The following table reflects the activity for the Company’s contingent consideration liabilities measured at fair value using Level 3 inputs for the nine months ended September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ Other Liabilities: ​ ​ Contingent ​ Consideration Balance at December 31, 2020 ​ $ 8,267 Fair value adjustments included in operating expenses ​ (1,160) Balance at September 30, 2021 ​ $ 7,107 ​ The valuation technique used to measure fair value of the Company’s Level 3 liabilities, which consist of contingent consideration related to the acquisition of Kolltan in 2016, was primarily an income approach. The significant unobservable inputs used in the fair value measurement of the contingent consideration are estimates including probability of success, discount rates and amount of time until the conditions of the milestone payments are met. As of September 30, 2021, the weighted average probability of success used in calculating the fair value of contingent consideration was 48.0% (with a range of 5.1% to 68.6%), the weighted average discount rate was 5.6% ( with a range of 5.1% to 6.7%) and the weighted average amount of time until the conditions of the milestone payments are met was 4 years. Weighted averages are calculated based on the relative fair value of our contingent consideration obligations. ​ During the three and nine months ended September 30, 2021, the Company recorded a $ 1.9 1.2 The Company did not have any transfers in or out of Level 3 assets liabilities during

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2021
Marketable Securities
Marketable Securities	(4) Marketable Securities ​ The following is a summary of marketable debt securities, classified as available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Unrealized ​ ​ Amortized ​ ​ ​ ​ ​ ​ ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) September 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 24,291 ​ $ 5 ​ $ — ​ $ 24,296 Maturing after one year through three years ​ ​ 75,314 ​ ​ 2 ​ ​ (17) ​ ​ 75,299 Total U.S. government and municipal obligations ​ $ 99,605 ​ $ 7 ​ $ (17) ​ $ 99,595 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 183,504 ​ $ — ​ $ (10) ​ $ 183,494 Maturing after one year through three years ​ ​ 67,844 ​ ​ 8 ​ ​ (36) ​ ​ 67,816 Total corporate debt securities ​ $ 251,348 ​ $ 8 ​ $ (46) ​ $ 251,310 Total marketable securities ​ $ 350,953 ​ $ 15 ​ $ (63) ​ $ 350,905 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Unrealized ​ ​ Amortized ​ ​ ​ ​ ​ ​ ​ Fair ​ ​ Cost Gains Losses Value ​ ​ (In thousands) December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 40,328 ​ $ 3 ​ $ (2) ​ $ 40,329 Maturing after one year through three years ​ ​ — ​ ​ — ​ ​ — ​ ​ — Total U.S. government and municipal obligations ​ $ 40,328 ​ $ 3 ​ $ (2) ​ $ 40,329 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 110,265 ​ $ 2 ​ $ (10) ​ $ 110,257 Maturing after one year through three years ​ ​ — ​ ​ — ​ ​ — ​ ​ — Total corporate debt securities ​ $ 110,265 ​ $ 2 ​ $ (10) ​ $ 110,257 Total marketable securities ​ $ 150,593 ​ $ 5 ​ $ (12) ​ $ 150,586 ​ The Company holds investment-grade marketable securities, and none were in a continuous unrealized loss position for more than twelve months as of September 30, 2021 and December 31, 2020. The unrealized losses are attributable to changes in interest rates and the Company does not believe any unrealized losses represent other-than-temporary impairments. Marketable securities include $0.8 million and $0.2 million in accrued interest at September 30, 2021 and December 31, 2020, respectively.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2021
Intangible Assets
Intangible Assets	(5) Intangible Assets ​ At September 30, 2021 and December 31, 2020, the carrying value of the Company’s indefinite-lived intangible assets was $27.2 million and $30.7 million, respectively. Indefinite-lived intangible assets consist of acquired IPR&D related to the development of the anti-KIT program (including CDX-0159) and the TAM program, a broad antibody discovery effort to generate antibodies that modulate the TAM family of RTKs, comprised of Tyro3, AxL and MerTK. CDX-0159 is in Phase 1 development and the TAM program is in preclinical development. As of September 30, 2021, none of the Company’s IPR&D assets had reached technological feasibility nor did any have alternative future uses. ​ The Company performs an impairment test on IPR&D assets at least annually, or more frequently if events or changes in circumstances indicate that IPR&D assets may be impaired. During the fourth quarter of 2020, the Company decided that although it had developed promising data for the AxL target within the TAM program, it would focus its efforts on out-licensing opportunities for its TAM program. As a result, the Company evaluated the TAM program IPR&D asset for potential impairment due to the change in projected development and regulatory timelines related to the program and recorded a non-cash partial impairment charge of $14.5 million for the fourth quarter of 2020. During the third quarter of 2021, the Company evaluated its out-licensing progress since December 31, 2020 and the status and expectation for the TAM program. Despite the Company’s efforts to out-license, there was a lack of interest in the program from third parties. Therefore, the Company evaluated the TAM program IPR&D asset for potential impairment using a discounted cash flow fair value model and concluded that the TAM IPR&D asset was fully impaired. A non-cash impairment charge of $3.5 million was recorded for the three months ended September 30, 2021. As a result of the discontinuation of the CDX-3379 program in the second quarter of 2020, the Company concluded that the CDX-3379 IPR&D asset was fully impaired and a non-cash impairment charge of $3.5 million was recorded in the second quarter of 2020. Due to the nature of IPR&D projects, the Company may experience future delays or failures to obtain regulatory approvals to conduct clinical trials, failures of such clinical trials or other failures to achieve a commercially viable product, and as a result, may recognize further impairment losses in the future. ​

Other Long-Term Liabilities

Other Long-Term Liabilities	9 Months Ended
	Sep. 30, 2021
Other Long-Term Liabilities
Other Long-Term Liabilities	(6) Other Long-Term Liabilities ​ Other long-term liabilities include the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 ​ ​ (In thousands) Net deferred tax liabilities related to IPR&D (Note 11) ​ $ 1,613 ​ $ 1,840 Contingent milestones (Note 3) ​ ​ 7,107 ​ ​ 8,267 Deferred revenue (Note 10) ​ 601 ​ 3,386 Total ​ 9,321 ​ 13,493 Less current portion ​ (1,721) ​ (3,372) Long-term portion ​ $ 7,600 ​ $ 10,121 ​

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity
Stockholders' Equity	(7) Stockholders’ Equity ​ In May 2016, the Company entered into a controlled equity offering sales agreement (the “Cantor Agreement”) with Cantor Fitzgerald & Co. (“Cantor”) to allow the Company to issue and sell shares of its common stock from time to time through Cantor, acting as agent. At September 30, 2021, the Company had $50.0 million remaining in aggregate gross offering price available under the Company’s November 2020 prospectus. ​ In July 2021, the Company issued 6,845,238 shares of its common stock in an underwritten public offering resulting in net proceeds to the Company of $269.9 million, after deducting underwriting fees and offering expenses. ​ The changes in Stockholders’ Equity during the three and nine months ended September 30, 2021 and 2020 are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ Common ​ Common ​ Additional ​ Other ​ ​ ​ ​ Total ​ ​ Stock ​ Stock Par ​ Paid-In ​ Comprehensive ​ Accumulated ​ Stockholders’ ​ ​ Shares ​ Value ​ Capital ​ Income ​ Deficit ​ Equity ​ ​ (In thousands, except share amounts) Consolidated balance at December 31, 2020 39,603,771 $ 40 $ 1,279,824 $ 2,589 $ (1,073,096) $ 209,357 Shares issued under stock option and employee stock purchase plans 10,867 — 74 — — 74 Stock-based compensation — — 1,275 — — 1,275 Unrealized loss on marketable securities — — — (2) — (2) Net loss — — — — (16,538) (16,538) Consolidated balance at March 31, 2021 39,614,638 $ 40 $ 1,281,173 $ 2,587 $ (1,089,634) $ 194,166 Shares issued under stock option and employee stock purchase plans 2,058 — (25) — — (25) Stock-based compensation — — 1,509 — — 1,509 Unrealized gain on marketable securities — — — 5 — 5 Net loss — — — — (13,373) ​ (13,373) Consolidated balance at June 30, 2021 39,616,696 ​ $ 40 ​ $ 1,282,657 ​ $ 2,592 ​ $ (1,103,007) ​ $ 182,282 Shares issued under stock option and employee stock purchase plans ​ 201,406 ​ ​ — ​ ​ 2,004 ​ ​ — ​ ​ — ​ ​ 2,004 Shares issued in underwritten offering, net ​ 6,845,238 ​ ​ 7 ​ ​ 269,886 ​ ​ — ​ ​ — ​ ​ 269,893 Stock-based compensation ​ — ​ ​ — ​ ​ 3,029 ​ ​ — ​ ​ — ​ ​ 3,029 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (44) ​ ​ — ​ ​ (44) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (20,452) ​ ​ (20,452) Consolidated balance at September 30, 2021 ​ 46,663,340 ​ $ 47 ​ $ 1,557,576 ​ $ 2,548 ​ $ (1,123,459) ​ $ 436,712 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ Common ​ Common ​ Additional ​ Other ​ ​ ​ ​ Total ​ ​ Stock ​ Stock Par ​ Paid-In ​ Comprehensive ​ Accumulated ​ Stockholders’ ​ ​ Shares ​ Value ​ Capital ​ Income ​ Deficit ​ Equity ​ ​ (In thousands, except share amounts) Consolidated balance at December 31, 2019 16,972,077 ​ $ 17 ​ $ 1,104,706 ​ $ 2,619 ​ $ (1,013,316) ​ $ 94,026 Shares issued under stock option and employee stock purchase plans 12,573 ​ — ​ 24 ​ — ​ — ​ 24 Shares issued in connection with at the market agreement 746,152 ​ 1 ​ 1,613 ​ — ​ — ​ 1,614 Stock-based compensation — ​ — ​ 686 ​ — ​ — ​ 686 Unrealized loss on marketable securities — ​ — ​ — ​ (22) ​ — ​ (22) Net loss — ​ — ​ — ​ — ​ (12,625) ​ (12,625) Consolidated balance at March 31, 2020 17,730,802 ​ $ 18 ​ $ 1,107,029 ​ $ 2,597 ​ $ (1,025,941) ​ $ 83,703 Shares issued in connection with at the market agreement 5,978,452 ​ 6 ​ 23,686 ​ — ​ — ​ 23,692 Shares issued in underwritten offering, net 15,384,614 ​ 15 ​ 141,346 ​ — ​ — ​ 141,361 Stock-based compensation — ​ — ​ 722 ​ — ​ — ​ 722 Unrealized loss on marketable securities — ​ — ​ — ​ (3) ​ — ​ (3) Net loss — ​ — ​ — ​ — ​ (11,031) ​ (11,031) Consolidated balance at June 30, 2020 39,093,868 ​ $ 39 ​ $ 1,272,783 ​ $ 2,594 ​ $ (1,036,972) ​ $ 238,444 Shares issued under stock option and employee stock purchase plans ​ 68,204 ​ ​ — ​ ​ 194 ​ ​ — ​ ​ — ​ ​ 194 Shares issued in connection with at the market agreement ​ 400,400 ​ ​ 1 ​ ​ 4,296 ​ ​ — ​ ​ — ​ ​ 4,297 Stock-based compensation ​ — ​ ​ — ​ ​ 1,250 ​ ​ — ​ ​ — ​ ​ 1,250 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 14 ​ ​ — ​ ​ 14 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (14,224) ​ ​ (14,224) Consolidated balance at September 30, 2020 ​ 39,562,472 ​ $ 40 ​ $ 1,278,523 ​ $ 2,608 ​ $ (1,051,196) ​ $ 229,975 ​

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Stock-Based Compensation
Stock-Based Compensation	(8) Stock-Based Compensation ​ A summary of stock option activity for the nine months ended September 30, 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ Exercise ​ Remaining ​ ​ ​ ​ Price ​ Contractual ​ Shares Per Share Term (In Years) Options outstanding at December 31, 2020 3,042,229 ​ $ 28.93 ​ 8.2 Granted 1,350,210 ​ $ 28.16 ​ ​ Exercised (192,464) ​ $ 9.53 ​ ​ Canceled (70,349) ​ $ 35.62 ​ ​ Options outstanding at September 30, 2021 4,129,626 ​ $ 29.46 ​ 8.2 Options vested and expected to vest at September 30, 2021 3,982,965 ​ $ 29.81 ​ 8.2 Options exercisable at September 30, 2021 1,387,147 ​ $ 51.75 ​ 6.7 Shares available for grant under the 2021 Plan 3,319,116 ​ ​ ​ ​ ​ ​ The weighted average grant-date fair value of stock options granted during the three and nine months ended September 30, 2021 was $41.34 and $21.86, respectively. ​ The aggregate intrinsic value of stock options vested and expected to vest at September 30, 2021 was $140.6 million. The aggregate intrinsic value of stock options exercisable at September 30, 2021 was $47.3 million. As of September 30, 2021, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $33.7 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.9 years. ​ Stock-based compensation expense for the three and nine months ended September 30, 2021 and 2020 was recorded as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2021 2020 2021 2020 ​ ​ (In thousands) ​ (In thousands) Research and development ​ $ 1,504 ​ $ 642 ​ $ 2,927 ​ $ 1,294 General and administrative ​ 1,525 ​ 608 ​ 2,886 ​ 1,364 Total stock-based compensation expense ​ $ 3,029 ​ $ 1,250 ​ $ 5,813 ​ $ 2,658 ​ The fair values of employee, consultant and non-employee director stock options granted during the three and nine months ended September 30, 2021 and 2020 were valued using the Black-Scholes option pricing model with the following assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, 2021 ​ 2020 2021 2020 Expected stock price volatility 98% ​ 98% ​ 97 – 98% ​ 91 – 98% Expected option term 6.0 Years ​ 6.0 Years ​ 6.0 Years ​ 6.0 Years Risk-free interest rate 1.1 – 1.2% ​ 0.5% ​ 0.8 – 1.3% ​ 0.5 – 0.6% Expected dividend yield None ​ None ​ None ​ None ​

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2021
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income	(9) Accumulated Other Comprehensive Income ​ The changes in accumulated other comprehensive income, which is reported as a component of stockholders’ equity, for the nine months ended September 30, 2021 are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ ​ ​ ​ ​ ​ ​ Loss on ​ ​ ​ ​ ​ ​ ​ ​ Marketable ​ Foreign ​ ​ ​ ​ Securities Currency Items Total ​ ​ (In thousands) Balance at December 31, 2020 ​ $ (7) ​ $ 2,596 ​ $ 2,589 Other comprehensive loss ​ (41) ​ — ​ (41) Balance at September 30, 2021 ​ $ (48) ​ $ 2,596 ​ $ 2,548 ​ No amounts were reclassified out of accumulated other comprehensive income during the nine months ended September 30, 2021.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2021
Revenue
Revenue	(10) Revenue ​ Product Development and Licensing Revenue ​ The Company’s agreement with Rockefeller University, as amended (the “Rockefeller Agreement”), provides for the Company to perform manufacturing and development services for Rockefeller University for their portfolio of antibodies against HIV. This portfolio was licensed to Gilead Sciences in January 2020 from Rockefeller University (“Rockefeller Transaction”). Pursuant to the Rockefeller Agreement, the Company received an upfront payment of $1.8 million as a result of the Rockefeller Transaction which was recorded to revenue during the first quarter of 2020. The Company is eligible to receive additional payments from Rockefeller University if this portfolio progresses through clinical and commercial development. ​ Contract and Grants Revenue ​ The Company has entered into the Rockefeller Agreement and an agreement with Gilead Sciences pursuant to which the Company performs manufacturing and research and development services on a time-and-materials basis or at a negotiated fixed-price. The Company recognized $0.1 million and $4.0 million in revenue under these agreements during the three and nine months ended September 30, 2021, respectively, and $0.3 million and $0.9 million during the three and nine months ended September 30, 2020, respectively. ​ During the third quarter of 2020, the Company was awarded a Small Business Innovation Research (“SBIR”) grant from the National Institutes of Health (NIH) to support the Company’s CDX-1140 and CDX-301 programs. The Company recognized $0.0 million and $0.3 million in grant revenue under the award during the three and nine months ended September 30, 2021, respectively, and $0.3 million during the three and nine months ended September 30, 2020. ​ Contract Assets and Liabilities ​ At September 30, 2021 and December 31, 2020, the Company’s right to consideration under all contracts was considered unconditional, and as such, there were no recorded contract assets. At September 30, 2021, the Company had $0.6 million in contract liabilities recorded, which is expected to be recognized during the next 12 months as manufacturing and research and development services are performed. At December 31, 2020, the Company had $3.4 million in contract liabilities recorded. Revenue recognized from contract liabilities as of December 31, 2020 during the three and nine months ended September 30, 2021 was $0.0 million and $3.4 million, respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Taxes
Income Taxes	(11) Income Taxes ​ The Company has evaluated the positive and negative evidence bearing upon the realizability of its net deferred tax assets and considered its history of losses, ultimately concluding that it is “more likely than not” that the Company will not recognize the benefits of federal, state and foreign deferred tax assets and, as such, has maintained a full valuation allowance on its deferred tax assets as of September 30, 2021 and December 31, 2020. ​ The net deferred tax liability of $1.6 million and $1.8 million at September 30, 2021 and December 31, 2020, respectively, relates to the temporary differences associated with the IPR&D intangible assets acquired in previous business combinations and is not deductible for tax purposes. A $0.2 million non-cash income tax benefit was recorded during the third quarter of 2021 and a $0.9 million non-cash income tax benefit was recorded during the fourth quarter of 2020 related to impairments of the TAM program IPR&D asset. A $0.2 million non-cash income tax benefit was recorded during the second quarter of 2020 related to the impairment of the CDX-3379 IPR&D asset. ​ Massachusetts, New Jersey, New York and Connecticut are the jurisdictions in which the Company primarily operates or has operated and has income tax nexus. The Company is not currently under examination by these or any other jurisdictions for any tax year.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Net Loss Per Share
Net Loss Per Share	(12) Net Loss Per Share ​ Basic net loss per common share is based upon the weighted-average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is based upon the weighted-average number of common shares outstanding during the period plus additional weighted-average potentially dilutive common shares outstanding during the period when the effect is dilutive. In periods in which the Company reports a net loss, there is no difference between basic and diluted net loss per share because dilutive shares of common stock are not assumed to have been issued as their effect is anti-dilutive. The potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive are as follows: ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ 2021 2020 Stock Options 4,129,626 3,074,832 Restricted Stock — — ​ 4,129,626 3,074,832 ​

Kolltan Acquisition

Kolltan Acquisition	9 Months Ended
	Sep. 30, 2021
Kolltan Acquisition
Kolltan Acquisition	(13) Kolltan Acquisition ​ On November 29, 2016, the Company acquired all of the share and debt interests of Kolltan, a clinical-stage biopharmaceutical company, in exchange for 1,217,200 shares of the Company’s common stock plus contingent consideration in the form of development, regulatory approval and sales-based milestones (“Kolltan Milestones”) of up to $172.5 million. The payment of Kolltan Milestones , if any, may be made, at Celldex’s sole election, in cash, in shares of Celldex’s common stock or a combination of both, subject to provisions of the Agreement and Plan of Merger, dated November 1, 2016 (the “Merger Agreement”). Certain Kolltan Milestones related to the METRIC clinical study, TAM partnership closing within two years of the acquisition, CDX-3379 and CDX-0158 have been abandoned and, because of this, as of September 30, 2021, the Company believes that the adjusted amount we may be required to pay for future consideration is up to $107.5 million contingent upon the achievement of the Kolltan Milestones. ​ In October 2019, the Company received a letter from Shareholder Representative Services LLC (“SRS”), the hired representative of the former stockholders of Kolltan, notifying the Company that it objected to the Company’s characterization of the development, regulatory approval and sales-based Kolltan Milestones relating to CDX-0158 as having been abandoned and contending instead that the related milestone payments are due from Celldex to the Kolltan stockholder. The Company disagrees with their objection and believes their objection to be without merit. ​ On August 18, 2020, Celldex filed a Verified Complaint in the Court of Chancery of the State of Delaware against SRS (acting in its capacity as the representative of the former stockholders of Kolltan pursuant to the Merger Agreement) seeking declaratory relief with respect to the rights and obligations of the parties relating to certain contingent milestone payments under the Merger Agreement relating to the discontinued CDX-0158 program. Specifically, Celldex sought the entry of an order declaring that: ​ (i) Celldex’s determination to discontinue the development of CDX-0158 (formerly known as KTN0158) was proper and valid under the Merger Agreement; ​ (ii) the Milestone Abandonment Notice dated December 5, 2018 from Celldex was valid and effective under the Merger Agreement and that the “Successful Completion of Phase I Clinical Trial for KTN0158” Milestone has not been achieved and has properly been abandoned; and ​ (iii) under the Merger Agreement, the CDX-0159 program is not a program that results in milestone payments under the Merger Agreement. ​ In SRS’ responsive Answer and Verified Counterclaim, SRS made claims of breach of contract with respect to the Merger Agreement, breach of implied covenant of good faith and fair dealing, declaratory relief, and unjust enrichment regarding abandonment of the CDX-0158 milestones, based in part on SRS’ assertion that the CDX-0159 program is in essence an extension of the CDX-0158 (formerly KTN0158) program. The parties entered into non-binding mediation in May 2021 following SRS’s approach to Celldex about its interest in settlement or mediation discussions, but those discussions did not result in a resolution of the dispute. The case remains ongoing and we are currently unable to predict or estimate the outcome of this matter. The case is currently scheduled for trial in June 2022. ​ Following the Company’s discontinuation of the CDX-3379 program, the Company sent a milestone abandonment notice to SRS with respect to Kolltan Milestones related to the CDX-3379 program. In October 2020, the Company received notice that SRS has objected to that notice, seeking further information from the Company, which was provided pursuant to the terms of the Merger Agreement.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Significant Accounting Policies
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements upon adoption. ​ In June 2016, the FASB issued guidance on the Measurement of Credit Losses on Financial Instruments. The guidance requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, the standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard will be effective for the Company on January 1, 2023. We are currently evaluating the potential impact that this standard may have on the Company’s consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Measurements
Schedule of financial assets and liabilities subject to fair value measurements	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 66,929 ​ ​ — ​ $ 66,929 ​ ​ — Marketable securities ​ ​ 350,905 ​ ​ — ​ ​ 350,905 ​ ​ — ​ ​ $ 417,834 ​ ​ — ​ $ 417,834 ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Kolltan acquisition contingent consideration ​ $ 7,107 ​ ​ — ​ ​ — ​ $ 7,107 ​ ​ $ 7,107 ​ ​ — ​ ​ — ​ $ 7,107 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 35,066 ​ ​ — ​ $ 35,066 ​ ​ — Marketable securities ​ ​ 150,586 ​ ​ — ​ ​ 150,586 ​ ​ — ​ ​ $ 185,652 ​ ​ — ​ $ 185,652 ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Kolltan acquisition contingent consideration ​ $ 8,267 ​ ​ — ​ ​ — ​ $ 8,267 ​ ​ $ 8,267 ​ ​ — ​ ​ — ​ $ 8,267
Schedule of the contingent consideration liabilities measured at fair value using Level 3 inputs	The following table reflects the activity for the Company’s contingent consideration liabilities measured at fair value using Level 3 inputs for the nine months ended September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ Other Liabilities: ​ ​ Contingent ​ Consideration Balance at December 31, 2020 ​ $ 8,267 Fair value adjustments included in operating expenses ​ (1,160) Balance at September 30, 2021 ​ $ 7,107

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Marketable Securities
Schedule of marketable debt securities, classified as available-for-sale	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Unrealized ​ ​ Amortized ​ ​ ​ ​ ​ ​ ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) September 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 24,291 ​ $ 5 ​ $ — ​ $ 24,296 Maturing after one year through three years ​ ​ 75,314 ​ ​ 2 ​ ​ (17) ​ ​ 75,299 Total U.S. government and municipal obligations ​ $ 99,605 ​ $ 7 ​ $ (17) ​ $ 99,595 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 183,504 ​ $ — ​ $ (10) ​ $ 183,494 Maturing after one year through three years ​ ​ 67,844 ​ ​ 8 ​ ​ (36) ​ ​ 67,816 Total corporate debt securities ​ $ 251,348 ​ $ 8 ​ $ (46) ​ $ 251,310 Total marketable securities ​ $ 350,953 ​ $ 15 ​ $ (63) ​ $ 350,905 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Unrealized ​ ​ Amortized ​ ​ ​ ​ ​ ​ ​ Fair ​ ​ Cost Gains Losses Value ​ ​ (In thousands) December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 40,328 ​ $ 3 ​ $ (2) ​ $ 40,329 Maturing after one year through three years ​ ​ — ​ ​ — ​ ​ — ​ ​ — Total U.S. government and municipal obligations ​ $ 40,328 ​ $ 3 ​ $ (2) ​ $ 40,329 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 110,265 ​ $ 2 ​ $ (10) ​ $ 110,257 Maturing after one year through three years ​ ​ — ​ ​ — ​ ​ — ​ ​ — Total corporate debt securities ​ $ 110,265 ​ $ 2 ​ $ (10) ​ $ 110,257 Total marketable securities ​ $ 150,593 ​ $ 5 ​ $ (12) ​ $ 150,586

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Other Long-Term Liabilities
Schedule of other long-term liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 ​ ​ (In thousands) Net deferred tax liabilities related to IPR&D (Note 11) ​ $ 1,613 ​ $ 1,840 Contingent milestones (Note 3) ​ ​ 7,107 ​ ​ 8,267 Deferred revenue (Note 10) ​ 601 ​ 3,386 Total ​ 9,321 ​ 13,493 Less current portion ​ (1,721) ​ (3,372) Long-term portion ​ $ 7,600 ​ $ 10,121

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity
Schedule of Shareholder's equity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ Common ​ Common ​ Additional ​ Other ​ ​ ​ ​ Total ​ ​ Stock ​ Stock Par ​ Paid-In ​ Comprehensive ​ Accumulated ​ Stockholders’ ​ ​ Shares ​ Value ​ Capital ​ Income ​ Deficit ​ Equity ​ ​ (In thousands, except share amounts) Consolidated balance at December 31, 2020 39,603,771 $ 40 $ 1,279,824 $ 2,589 $ (1,073,096) $ 209,357 Shares issued under stock option and employee stock purchase plans 10,867 — 74 — — 74 Stock-based compensation — — 1,275 — — 1,275 Unrealized loss on marketable securities — — — (2) — (2) Net loss — — — — (16,538) (16,538) Consolidated balance at March 31, 2021 39,614,638 $ 40 $ 1,281,173 $ 2,587 $ (1,089,634) $ 194,166 Shares issued under stock option and employee stock purchase plans 2,058 — (25) — — (25) Stock-based compensation — — 1,509 — — 1,509 Unrealized gain on marketable securities — — — 5 — 5 Net loss — — — — (13,373) ​ (13,373) Consolidated balance at June 30, 2021 39,616,696 ​ $ 40 ​ $ 1,282,657 ​ $ 2,592 ​ $ (1,103,007) ​ $ 182,282 Shares issued under stock option and employee stock purchase plans ​ 201,406 ​ ​ — ​ ​ 2,004 ​ ​ — ​ ​ — ​ ​ 2,004 Shares issued in underwritten offering, net ​ 6,845,238 ​ ​ 7 ​ ​ 269,886 ​ ​ — ​ ​ — ​ ​ 269,893 Stock-based compensation ​ — ​ ​ — ​ ​ 3,029 ​ ​ — ​ ​ — ​ ​ 3,029 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (44) ​ ​ — ​ ​ (44) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (20,452) ​ ​ (20,452) Consolidated balance at September 30, 2021 ​ 46,663,340 ​ $ 47 ​ $ 1,557,576 ​ $ 2,548 ​ $ (1,123,459) ​ $ 436,712 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ Common ​ Common ​ Additional ​ Other ​ ​ ​ ​ Total ​ ​ Stock ​ Stock Par ​ Paid-In ​ Comprehensive ​ Accumulated ​ Stockholders’ ​ ​ Shares ​ Value ​ Capital ​ Income ​ Deficit ​ Equity ​ ​ (In thousands, except share amounts) Consolidated balance at December 31, 2019 16,972,077 ​ $ 17 ​ $ 1,104,706 ​ $ 2,619 ​ $ (1,013,316) ​ $ 94,026 Shares issued under stock option and employee stock purchase plans 12,573 ​ — ​ 24 ​ — ​ — ​ 24 Shares issued in connection with at the market agreement 746,152 ​ 1 ​ 1,613 ​ — ​ — ​ 1,614 Stock-based compensation — ​ — ​ 686 ​ — ​ — ​ 686 Unrealized loss on marketable securities — ​ — ​ — ​ (22) ​ — ​ (22) Net loss — ​ — ​ — ​ — ​ (12,625) ​ (12,625) Consolidated balance at March 31, 2020 17,730,802 ​ $ 18 ​ $ 1,107,029 ​ $ 2,597 ​ $ (1,025,941) ​ $ 83,703 Shares issued in connection with at the market agreement 5,978,452 ​ 6 ​ 23,686 ​ — ​ — ​ 23,692 Shares issued in underwritten offering, net 15,384,614 ​ 15 ​ 141,346 ​ — ​ — ​ 141,361 Stock-based compensation — ​ — ​ 722 ​ — ​ — ​ 722 Unrealized loss on marketable securities — ​ — ​ — ​ (3) ​ — ​ (3) Net loss — ​ — ​ — ​ — ​ (11,031) ​ (11,031) Consolidated balance at June 30, 2020 39,093,868 ​ $ 39 ​ $ 1,272,783 ​ $ 2,594 ​ $ (1,036,972) ​ $ 238,444 Shares issued under stock option and employee stock purchase plans ​ 68,204 ​ ​ — ​ ​ 194 ​ ​ — ​ ​ — ​ ​ 194 Shares issued in connection with at the market agreement ​ 400,400 ​ ​ 1 ​ ​ 4,296 ​ ​ — ​ ​ — ​ ​ 4,297 Stock-based compensation ​ — ​ ​ — ​ ​ 1,250 ​ ​ — ​ ​ — ​ ​ 1,250 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 14 ​ ​ — ​ ​ 14 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (14,224) ​ ​ (14,224) Consolidated balance at September 30, 2020 ​ 39,562,472 ​ $ 40 ​ $ 1,278,523 ​ $ 2,608 ​ $ (1,051,196) ​ $ 229,975

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Stock-Based Compensation
Schedule of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ Exercise ​ Remaining ​ ​ ​ ​ Price ​ Contractual ​ Shares Per Share Term (In Years) Options outstanding at December 31, 2020 3,042,229 ​ $ 28.93 ​ 8.2 Granted 1,350,210 ​ $ 28.16 ​ ​ Exercised (192,464) ​ $ 9.53 ​ ​ Canceled (70,349) ​ $ 35.62 ​ ​ Options outstanding at September 30, 2021 4,129,626 ​ $ 29.46 ​ 8.2 Options vested and expected to vest at September 30, 2021 3,982,965 ​ $ 29.81 ​ 8.2 Options exercisable at September 30, 2021 1,387,147 ​ $ 51.75 ​ 6.7 Shares available for grant under the 2021 Plan 3,319,116 ​ ​ ​ ​ ​ ​
Schedule of stock-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2021 2020 2021 2020 ​ ​ (In thousands) ​ (In thousands) Research and development ​ $ 1,504 ​ $ 642 ​ $ 2,927 ​ $ 1,294 General and administrative ​ 1,525 ​ 608 ​ 2,886 ​ 1,364 Total stock-based compensation expense ​ $ 3,029 ​ $ 1,250 ​ $ 5,813 ​ $ 2,658 ​
Schedule of assumptions used for the fair value of employee stock options granted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, 2021 ​ 2020 2021 2020 Expected stock price volatility 98% ​ 98% ​ 97 – 98% ​ 91 – 98% Expected option term 6.0 Years ​ 6.0 Years ​ 6.0 Years ​ 6.0 Years Risk-free interest rate 1.1 – 1.2% ​ 0.5% ​ 0.8 – 1.3% ​ 0.5 – 0.6% Expected dividend yield None ​ None ​ None ​ None

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2021
Accumulated Other Comprehensive Income
Schedule of changes in accumulated other comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ ​ ​ ​ ​ ​ ​ Loss on ​ ​ ​ ​ ​ ​ ​ ​ Marketable ​ Foreign ​ ​ ​ ​ Securities Currency Items Total ​ ​ (In thousands) Balance at December 31, 2020 ​ $ (7) ​ $ 2,596 ​ $ 2,589 Other comprehensive loss ​ (41) ​ — ​ (41) Balance at September 30, 2021 ​ $ (48) ​ $ 2,596 ​ $ 2,548

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Net Loss Per Share
Schedule of potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive	​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ 2021 2020 Stock Options 4,129,626 3,074,832 Restricted Stock — — ​ 4,129,626 3,074,832

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Unusual Risk or Uncertainty [Line Items]
Cash, cash equivalents and marketable securities	$ 423,100						$ 423,100
Net loss	(20,452)	$ (13,373)	$ (16,538)	$ (14,224)	$ (11,031)	$ (12,625)	(50,363)	$ (37,880)
Net cash used in operations							(46,386)	(35,193)
Indefinite-lived intangible assets	27,200						27,200		$ 30,700
Intangible asset impairment	$ 3,500						3,500	$ 3,500
COVID-19
Unusual Risk or Uncertainty [Line Items]
Intangible asset impairment							$ 27,200

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Liabilities:
Kolltan acquisition contingent consideration	$ 7,107	$ 8,267
Fair value | Level 3
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Fair Value Measurements. | Level 2
Assets:
Money market funds and cash equivalents	66,929	35,066
Marketable securities	350,905	150,586
Total financial assets at fair value	417,834	185,652
Fair Value Measurements. | Level 3
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Total financial liabilities at fair value	7,107	8,267
Fair Value Measurements. | Fair value
Assets:
Money market funds and cash equivalents	66,929	35,066
Marketable securities	350,905	150,586
Total financial assets at fair value	417,834	185,652
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Total financial liabilities at fair value	$ 7,107	$ 8,267

Fair Value Measurements - Conti

Fair Value Measurements - Contingent Consideration Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Contingent consideration liabilities measured at fair value
Balance at beginning of period	$ 8,267
Balance at end of period	7,107
Fair value | Level 3
Contingent consideration liabilities measured at fair value
Balance at beginning of period	8,267
Fair value adjustments included in operating expenses	(1,160)
Balance at end of period	$ 7,107

Fair Value Measurements - Addit

Fair Value Measurements - Additional information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Fair value measurements
Gain on Fair Value Remeasurement of Contingent Consideration	$ 1,901	$ (662)	$ 1,160	$ 4,236
Discount rate | Weighted average
Fair value measurements
Measurement input	5.6		5.6
Discount rate | Minimum
Fair value measurements
Measurement input	5.1		5.1
Discount rate | Maximum
Fair value measurements
Measurement input	6.7		6.7
Time until the conditions of the milestone payments are met
Fair value measurements
Measurement input	4		4
Fair value
Fair value measurements
Asset transfer out of level 3			$ 0
Asset transfer into level 3			0
Liabilities transfers out of level 3			$ 0
Fair value | Weighted average
Fair value measurements
Measurement input	48		48
Fair value | Minimum
Fair value measurements
Measurement input	5.1		5.1
Fair value | Maximum
Fair value measurements
Measurement input	68.6		68.6

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Amortized Cost
Amortized Cost	$ 350,953	$ 150,593
Gross Unrealized Gains
Gross Unrealized Gains	15	5
Gross Unrealized Losses
Gross Unrealized Losses	(63)	(12)
Fair Value
Fair Value	350,905	150,586
U.S. government and municipal obligations
Amortized Cost
Maturing in one year or less	24,291	40,328
Maturing after one year through three years	75,314
Amortized Cost	99,605	40,328
Gross Unrealized Gains
Maturing in one year or less	5	3
Maturing after one year through three years	2
Gross Unrealized Gains	7	3
Gross Unrealized Losses
Maturing in one year or less		(2)
Maturing after one year through three years	(17)
Gross Unrealized Losses	(17)	(2)
Fair Value
Maturing in one year or less	24,296	40,329
Maturing after one year through three years	75,299
Fair Value	99,595	40,329
Corporate debt securities
Amortized Cost
Maturing in one year or less	183,504	110,265
Maturing after one year through three years	67,844
Amortized Cost	251,348	110,265
Gross Unrealized Gains
Maturing in one year or less		2
Maturing after one year through three years	8
Gross Unrealized Gains	8	2
Gross Unrealized Losses
Maturing in one year or less	(10)	(10)
Maturing after one year through three years	(36)
Gross Unrealized Losses	(46)	(10)
Fair Value
Maturing in one year or less	183,494	110,257
Maturing after one year through three years	67,816
Fair Value	$ 251,310	$ 110,257

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Marketable Securities
Number of investment-grade securities in unrealized loss position over 12 months	$ 0	$ 0
Accrued interest	$ 800	$ 200

Intangible Assets - Intangible

Intangible Assets - Intangible Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Intangible assets
Indefinite-lived intangible assets	$ 27,200	$ 30,700		$ 27,200
Intangible Asset Impairment	3,500			$ 3,500	$ 3,500
IPR&D
Intangible assets
Intangible Asset Impairment	$ 3,500	$ 14,500	$ 3,500

Other Long-Term Liabilities (De

Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other Long-Term Liabilities
Net deferred tax liabilities related to IPR&D (Note 11)	$ 1,613	$ 1,840
Contingent milestones (Note 3)	7,107	8,267
Deferred revenue (Note 10)	601	3,386
Total	9,321	13,493
Less current portion	(1,721)	(3,372)
Long-term portion	$ 7,600	$ 10,121

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended						9 Months Ended
	Jul. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Common Stock
Balance	$ 182,282	$ 182,282	$ 194,166	$ 209,357	$ 238,444	$ 83,703	$ 94,026	$ 209,357	$ 94,026
Balance (in shares)				39,603,771				39,603,771
Shares issued under stock option and employee stock purchase plans		2,004		$ 74	194		24
Shares issued under stock option and employee stock purchase plans			(25)
Shares issued in connection with at the market agreement					4,297	23,692	1,614
Shares issued in underwritten offering, net		269,893				141,361
Stock-based compensation		3,029	1,509	1,275	1,250	722	686
Unrealized (loss) gain on marketable securities		(44)	5	(2)	14	(3)	(22)	$ (41)	(11)
Net loss		(20,452)	(13,373)	(16,538)	(14,224)	(11,031)	(12,625)	(50,363)	(37,880)
Balance		$ 436,712	182,282	194,166	229,975	238,444	83,703	$ 436,712	229,975
Balance (in shares)		46,663,340						46,663,340
Aggregate gross offering price available		$ 50,000						$ 50,000
Net proceeds from sale of common stock								269,893	170,964
Underwritten Public Offering
Common Stock
Common stock issued (in shares)	6,845,238
Net proceeds from sale of common stock	$ 269,900
Common Stock
Common Stock
Balance	$ 40	$ 40	$ 40	$ 40	$ 39	$ 18	$ 17	$ 40	$ 17
Balance (in shares)	39,616,696	39,616,696	39,614,638	39,603,771	39,093,868	17,730,802	16,972,077	39,603,771	16,972,077
Shares issued under stock option and employee stock purchase plans (in shares)		201,406		10,867	68,204		12,573
Shares issued under stock option and employee stock purchase plans (in shares)			2,058
Shares issued in connection with at the market agreement					$ 1	$ 6	$ 1
Shares issued in connection with at the market agreement (in shares)					400,400	5,978,452	746,152
Shares issued in underwritten offering, net		$ 7				$ 15
Shares issued in underwritten offering, net (in shares)		6,845,238				15,384,614
Balance		$ 47	$ 40	$ 40	$ 40	$ 39	$ 18	$ 47	$ 40
Balance (in shares)		46,663,340	39,616,696	39,614,638	39,562,472	39,093,868	17,730,802	46,663,340	39,562,472
Additional Paid-In Capital
Common Stock
Balance	$ 1,282,657	$ 1,282,657	$ 1,281,173	$ 1,279,824	$ 1,272,783	$ 1,107,029	$ 1,104,706	$ 1,279,824	$ 1,104,706
Shares issued under stock option and employee stock purchase plans		2,004		74	194		24
Shares issued under stock option and employee stock purchase plans			(25)
Shares issued in connection with at the market agreement					4,296	23,686	1,613
Shares issued in underwritten offering, net		269,886				141,346
Stock-based compensation		3,029	1,509	1,275	1,250	722	686
Balance		1,557,576	1,282,657	1,281,173	1,278,523	1,272,783	1,107,029	1,557,576	1,278,523
Accumulated Other Comprehensive Income
Common Stock
Balance	2,592	2,592	2,587	2,589	2,594	2,597	2,619	2,589	2,619
Unrealized (loss) gain on marketable securities		(44)	5	(2)	14	(3)	(22)
Balance		2,548	2,592	2,587	2,608	2,594	2,597	2,548	2,608
Accumulated Deficit
Common Stock
Balance	$ (1,103,007)	(1,103,007)	(1,089,634)	(1,073,096)	(1,036,972)	(1,025,941)	(1,013,316)	(1,073,096)	(1,013,316)
Net loss		(20,452)	(13,373)	(16,538)	(14,224)	(11,031)	(12,625)
Balance		$ (1,123,459)	$ (1,103,007)	$ (1,089,634)	$ (1,051,196)	$ (1,036,972)	$ (1,025,941)	$ (1,123,459)	$ (1,051,196)

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - Stock Options - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Shares
Options outstanding at beginning of the period (in shares)	3,042,229
Granted (in shares)	1,350,210
Exercised (in shares)	(192,464)
Canceled (in shares)	(70,349)
Options outstanding at the end of the period (in shares)	4,129,626	3,042,229
Options vested and expected to vest at the end of the period (in shares)	3,982,965
Options exercisable at the end of the period (in shares)	1,387,147
Shares available for grant under the 2021 Plan	3,319,116
Weighted Average Exercise Price Per Share
Options outstanding at beginning of the period (in dollars per share)	$ 28.93
Granted (in dollars per share)	28.16
Exercised (in dollars per share)	9.53
Canceled (in dollars per share)	35.62
Options outstanding at the end of the period (in dollars per share)	29.46	$ 28.93
Options vested and expected to Vest at the end of the period (in dollars per share)	29.81
Options exercisable at the end of the period (in dollars per share)	$ 51.75
Weighted Average Remaining Contractual Term (In Years)
Options outstanding at the end of the period	8 years 2 months 12 days	8 years 2 months 12 days
Options vested and expected to vest at the end of the period	8 years 2 months 12 days
Options exercisable at the end of the period	6 years 8 months 12 days

Stock-Based Compensation - Expe

Stock-Based Compensation - Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation expense
Stock-based compensation expense	$ 3,029	$ 1,250	$ 5,813	$ 2,658
Research and development
Stock-based compensation expense
Stock-based compensation expense	1,504	642	2,927	1,294
General and administrative
Stock-based compensation expense
Stock-based compensation expense	$ 1,525	$ 608	$ 2,886	$ 1,364

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Black-Scholes option with following assumptions:
Expected stock price volatility (as a percent)	98.00%	98.00%
Expected stock price volatility, minimum (as a percent)			97.00%	91.00%
Expected stock price volatility, maximum (as a percent)			98.00%	98.00%
Expected option term	6 years	6 years	6 years	6 years
Risk-free interest rate (as a percent)		0.50%
Risk-free interest rate, minimum (as a percent)	1.10%		0.80%	0.50%
Risk-free interest rate, maximum (as a percent)	1.20%		1.30%	0.60%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Option and Incentive Plan Activity Additional Information (Details) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2021USD ($)$ / shares
Additional information
Weighted average grant-date fair value (in dollars per share) | $ / shares	$ 41.34	$ 21.86
Intrinsic value of options vested and expected to vest	$ 140.6	$ 140.6
Intrinsic value of options exercisable	47.3	47.3
Compensation cost not yet recognized	$ 33.7	$ 33.7
Weighted average period compensation cost is expected to be recognized (in years)		2 years 10 months 24 days

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Accumulated Other Comprehensive Income
Balance	$ 209,357
Balance	436,712
Amounts reclassified from AOCI	0
Unrealized Loss on Marketable Securities
Accumulated Other Comprehensive Income
Balance	(7)
Other comprehensive loss	(41)
Balance	(48)
Foreign Currency Items
Accumulated Other Comprehensive Income
Balance	2,596
Balance	2,596
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Balance	2,589
Other comprehensive loss	(41)
Balance	$ 2,548

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue
Revenue, contract liabilities	$ 0			$ 3,400
Revenues	153	$ 668		4,317	$ 3,633
Contract assets	0			0		$ 0
Contract liability	601			601		$ 3,386
Product development and licensing agreements
Revenue
Revenues		12		29	2,297
Contracts and grants
Revenue
Revenues	153	656		4,288	1,336
Rockefeller | Product development and licensing agreements
Revenue
Revenue, contract liabilities			$ 1,800
Rockefeller University and Duke University | Contracts and grants
Revenue
Revenues	100	300		4,000	900
National Institute of Health
Revenue
Revenues	$ 0	$ 300		$ 300	$ 300

Income Taxes - Summary of Defer

Income Taxes - Summary of Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gross deferred tax liabilities
Net deferred tax liability	$ 1,613	$ 1,840		$ 1,613
Principal components of the deferred tax assets and liabilities
Income Tax Benefit	$ (227)	$ 900	$ (200)	$ (227)	$ (228)

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Anti-dilutive securities
Potentially dilutive common shares not been included in net loss per common share calculations because the effect would have been anti-dilutive	4,129,626	3,074,832
Stock Options
Anti-dilutive securities
Potentially dilutive common shares not been included in net loss per common share calculations because the effect would have been anti-dilutive	4,129,626	3,074,832

Kolltan Acquisition (Details)

Kolltan Acquisition (Details) - Kolltan - USD ($) $ in Millions	Nov. 29, 2016	Sep. 30, 2021
Kolltan Acquisition
Shares issued as part of consideration (in shares)	1,217,200
Potential milestone payments		$ 107.5
Specified development, regulatory approvals or sales-based milestones
Kolltan Acquisition
Potential milestone payments	$ 172.5