Celldex Therapeutics (CLDX) 10-Q 6 Nov 24 2024 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2024	Oct. 29, 2024
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Securities Act 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	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		66,344,236
Entity Central Index Key	0000744218
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 36,399	$ 34,814
Marketable securities	719,600	388,784
Accounts and other receivables	852	2,628
Prepaid and other current assets	21,991	5,467
Total current assets	778,842	431,693
Property and equipment, net	4,230	4,060
Operating lease right-of-use assets, net	3,170	2,577
Intangible assets	27,190	27,190
Other assets	9,747	107
Total assets	823,179	465,627
Current liabilities:
Accounts payable	1,114	3,494
Accrued expenses	28,204	22,029
Current portion of operating lease liabilities	1,379	1,614
Current portion of other long-term liabilities	1,396	3,988
Total current liabilities	32,093	31,125
Long-term portion of operating lease liabilities	1,708	928
Other long-term liabilities	3,473	4,403
Total liabilities	37,274	36,456
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, 2024 and December 31, 2023
Common stock, $.001 par value; 297,000,000 shares authorized; 66,344,236 and 55,883,377 shares issued and outstanding at September 30, 2024 and December 31, 2023, respectively	66	56
Additional paid-in capital	2,288,683	1,823,168
Accumulated other comprehensive income	5,288	3,308
Accumulated deficit	(1,508,132)	(1,397,361)
Total stockholders' equity	785,905	429,171
Total liabilities and stockholders' equity	$ 823,179	$ 465,627

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
CONDENSED CONSOLIDATED BALANCE SHEETS
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Convertible preferred stock, shares issued (in shares)	0	0
Convertible preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	297,000,000	297,000,000
Common stock, shares issued (in shares)	66,344,236	55,883,377
Common stock, shares outstanding (in shares)	66,344,236	55,883,377

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues:
Total revenues	$ 3,191	$ 1,517	$ 5,845	$ 2,752
Operating expenses:
Research and development	45,263	34,535	116,611	87,585
General and administrative	10,054	8,221	28,285	22,082
Total operating expenses	55,317	42,756	144,896	109,667
Operating loss	(52,126)	(41,239)	(139,051)	(106,915)
Investment and other income, net	10,005	2,979	28,280	8,792
Net loss	$ (42,121)	$ (38,260)	$ (110,771)	$ (98,123)
Basic net loss per common share (in dollars per share)	$ (0.64)	$ (0.81)	$ (1.74)	$ (2.08)
Diluted net loss per common share (in dollars per share)	$ (0.64)	$ (0.81)	$ (1.74)	$ (2.08)
Shares used in calculating basic net loss per share (in shares)	66,294	47,261	63,737	47,243
Shares used in calculating diluted net loss per share (in shares)	66,294	47,261	63,737	47,243
Comprehensive loss:
Net loss	$ (42,121)	$ (38,260)	$ (110,771)	$ (98,123)
Other comprehensive income (loss):
Unrealized gain on marketable securities	3,508	63	1,980	875
Comprehensive loss	(38,613)	(38,197)	(108,791)	(97,248)
Product development and licensing agreements
Revenues:
Total revenues	3	2	5	19
Contracts and grants
Revenues:
Total revenues	$ 3,188	$ 1,515	$ 5,840	$ 2,733

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOW - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (110,771)	$ (98,123)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,358	2,249
Amortization and premium of marketable securities, net	(12,386)	(4,043)
Loss on sale or disposal of assets	12
Stock-based compensation expense	24,462	16,678
Changes in operating assets and liabilities:
Accounts and other receivables	1,776	95
Prepaid and other current assets	(19,961)	1,757
Other assets	(9,640)	(3)
Accounts payable and accrued expenses	3,640	5,507
Other liabilities	(4,792)	1,125
Net cash used in operating activities	(125,302)	(74,758)
Cash flows from investing activities:
Sales and maturities of marketable securities	347,732	249,703
Purchases of marketable securities	(660,745)	(183,172)
Acquisition of property and equipment	(1,163)	(1,152)
Net cash (used in) provided by investing activities	(314,176)	65,379
Cash flows from financing activities:
Net proceeds from stock issuances	432,298
Proceeds from issuance of stock from employee benefit plans	8,765	1,084
Net cash provided by financing activities	441,063	1,084
Net increase (decrease) in cash and cash equivalents	1,585	(8,295)
Cash and cash equivalents at beginning of period	34,814	29,429
Cash and cash equivalents at end of period	36,399	21,134
Non-cash investing activities
Accrued construction in progress	$ 232	$ 488

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2024
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, 2023, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 26, 2024. 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, 2024. ​ At September 30, 2024, the Company had cash, cash equivalents and marketable securities of $756.0 million. The Company has had recurring losses and incurred a loss of $110.8 million for the nine months ended September 30, 2024. Net cash used in operations for the nine months ended September 30, 2024 was $125.3 million. The Company believes that the cash, cash equivalents and marketable securities at the filing date of this Quarterly Report on 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 financings, 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 the future milestone under the Settlement Agreement (defined below) with Shareholder Representative Services LLC (“SRS”) (refer to Note 14), in the event that the Company achieves the milestone related to that payment. The Company, at its option, may decide to pay that milestone payment 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.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Significant Accounting Policies
Significant Accounting Policies	(2) Significant Accounting Policies ​ The significant accounting policies used in preparation of these condensed consolidated financial statements on this Quarterly Report on Form 10-Q for the three and nine months ended September 30, 2024 are consistent with those discussed in Note 2 to the financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. ​ Recent Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“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 adoption of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements or disclosures. ​ In November 2023, the FASB issued ASU 2023-07 Segment Reporting - Improvements to Reportable Segment Disclosures ​ In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, ​ In March 2024, the SEC adopted final rules requiring public entities to provide certain climate-related information in their registration statements and annual reports. The rules require disclosure of, among other things: material climate-related risks; activities to mitigate or adapt to such risks; governance and management of such risks; and material greenhouse gas (GHG) emissions from operations owned or controlled (Scope 1) and/or indirect emissions from purchased energy consumed in operations (Scope 2). Additionally, the rules require disclosure in the notes to the financial statements of the effects of severe weather events and other natural conditions, subject to certain materiality thresholds. In April 2024, the SEC voluntarily stayed the new rules as a result of pending legal challenges. Absent the result of pending legal challenges, and the removal of the stay, the rules were to become effective on a phased-in timeline, with the first requirements to be adopted for the Company’s fiscal year beginning in 2025. The Company is assessing the effect of the new rules on its consolidated financial statements and related disclosures. ​

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2024
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, 2024 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 25,292 ​ ​ — ​ $ 25,292 ​ ​ — Marketable securities ​ ​ 719,600 ​ ​ — ​ ​ 719,600 ​ ​ — ​ ​ $ 744,892 ​ ​ — ​ $ 744,892 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 19,803 ​ ​ — ​ $ 19,803 ​ ​ — Marketable securities ​ ​ 388,784 ​ ​ — ​ ​ 388,784 ​ ​ — ​ ​ $ 408,587 ​ ​ — ​ $ 408,587 ​ ​ — ​ 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. ​ Contingent consideration liabilities measured at fair value using Level 3 inputs were $0.0 million as of September 30, 2024 and December 31, 2023. 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 Pharmaceuticals, Inc. (“Kolltan”) in 2016, is 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. ​ There was no gain or loss on fair value remeasurement of contingent consideration recorded during the three and nine months ended September 30, 2024 or September 30, 2023. The assumptions related to determining the fair value of contingent consideration include a significant amount of judgment, and any changes in the underlying estimates could have a material impact on the amount of contingent consideration adjustment recorded in any given period. ​ 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, 2024
Marketable Securities
Marketable Securities	(4) Marketable Securities ​ The following is a summary of marketable debt securities, classified as available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Gross Unrealized ​ Gross Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) September 30, 2024 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 196,235 ​ $ 729 ​ $ — ​ $ 196,964 Maturing after one year through three years ​ ​ 107,595 ​ ​ 1,081 ​ ​ — ​ ​ 108,676 Total U.S. government and municipal obligations ​ $ 303,830 ​ $ 1,810 ​ $ — ​ $ 305,640 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 375,022 ​ $ 704 ​ $ (5) ​ $ 375,721 Maturing after one year through three years ​ ​ 38,057 ​ ​ 187 ​ ​ (5) ​ ​ 38,239 Total corporate debt securities ​ $ 413,079 ​ $ 891 ​ $ (10) ​ $ 413,960 Total marketable securities ​ $ 716,909 ​ $ 2,701 ​ $ (10) ​ $ 719,600 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Gross Unrealized ​ Gross Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) December 31, 2023 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 132,459 ​ $ 143 ​ $ (53) ​ $ 132,549 Maturing after one year through three years ​ ​ 26,009 ​ ​ 77 ​ ​ — ​ ​ 26,086 Total U.S. government and municipal obligations ​ $ 158,468 ​ $ 220 ​ $ (53) ​ $ 158,635 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 183,625 ​ $ 300 ​ $ (10) ​ $ 183,915 Maturing after one year through three years ​ ​ 45,977 ​ ​ 257 ​ ​ — ​ ​ 46,234 Total corporate debt securities ​ $ 229,602 ​ $ 557 ​ $ (10) ​ $ 230,149 Total marketable securities ​ $ 388,070 ​ $ 777 ​ $ (63) ​ $ 388,784 ​ The Company holds investment-grade marketable securities. Unrealized losses are generally attributable to changes in interest rates. The aggregate fair value of marketable securities held by the Company in an unrealized loss position as of September 30, 2024 and December 31, 2023 was $28.6 million and $80.4 million, respectively. The Company has the intent and ability to hold its marketable securities until recovery and has determined that there has been no material change to their credit risk. As a result, the Company determined it did not hold any investments with a credit loss at September 30, 2024. Marketable securities include $5.3 million and $1.9 million in accrued interest at September 30, 2024 and December 31, 2023, respectively.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2024
Intangible Assets
Intangible Assets	(5) Intangible Assets At September 30, 2024 and December 31, 2023, the carrying value of the Company’s indefinite-lived intangible assets was $27.2 million. Indefinite-lived intangible assets consist of acquired in-process research and development (“IPR&D”) related to the development of the anti-KIT program (including barzolvolimab), which was recorded in connection with the Kolltan acquisition. Barzolvolimab is in Phase 3 development. As of September 30, 2024, the IPR&D asset related to the anti-KIT program had not reached technological feasibility nor did the asset 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. 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 Assets

Other Assets	9 Months Ended
	Sep. 30, 2024
Other Assets
Other Assets	(6) Other Assets The Company records advance payments for services that will not be performed within one year of the balance sheet date as other assets. Such amounts will be recognized as expense in the period in which the related services are performed. Advance payments reflected within other assets in our consolidated balance sheets were $9.6 million and $0.0 million at September 30, 2024 and December 31, 2023, respectively.

Other Long-Term Liabilities

Other Long-Term Liabilities	9 Months Ended
	Sep. 30, 2024
Other Long-Term Liabilities
Other Long-Term Liabilities	(7) Other Long-Term Liabilities ​ Other long-term liabilities include the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2024 ​ 2023 ​ ​ (In thousands) Net deferred tax liabilities related to IPR&D (Note 12) ​ $ 1,613 ​ $ 1,613 Deferred income from sale of tax benefits ​ 2,790 ​ ​ 3,720 Deferred revenue (Note 11) ​ 466 ​ ​ 3,058 Total ​ 4,869 ​ ​ 8,391 Less current portion ​ (1,396) ​ ​ (3,988) Long-term portion ​ $ 3,473 ​ $ 4,403 ​ In March 2022, the Company received approval from the New Jersey Economic Development Authority and agreed to sell New Jersey tax benefits of $5.0 million to an independent third party for $4.7 million. Under the agreement, the Company must maintain a base of operations in New Jersey for five years or the tax benefits must be paid back on a pro-rata basis based on the number of years completed. The Company recognized $0.0 million and $0.9 million in other income related to the sale of these tax benefits for the three and nine months ended September 30, 2024, respectively, and $0.0 million and $0.9 million for the three and nine months ended September 30, 2023, respectively.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2024
Stockholders' Equity
Stockholders' Equity	(8) Stockholders’ Equity ​ In November 2023, the Company filed an automatic shelf registration statement with the SEC to register for sale any combination of the types of securities described in the shelf registration statement, including shares of its common stock. Also in November 2023, the Company issued 8,538,750 shares of its common stock in an underwritten public offering resulting in net proceeds to the Company of $216.2 million, after deducting underwriting fees and offering expenses. ​ On February 26, 2024, the Company entered into a controlled equity offering sales agreement (“ATM 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. Also on February 26, 2024, the Company terminated its pre-existing controlled equity offering sale agreement dated May 19, 2016 with Cantor. At September 30, 2024, the Company had registered $300.0 million of its common stock to be sold pursuant to the Company’s ATM Agreement, all of which remained unsold as of that date. ​ In March 2024, the Company issued 9,798,000 shares of its common stock in an underwritten public offering resulting in net proceeds to the Company of $432.3 million, after deducting underwriting fees and offering expenses. ​ The changes in Stockholders’ Equity during the three and nine months ended September 30, 2024 and 2023 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, 2023 55,883,377 $ 56 $ 1,823,168 $ 3,308 $ (1,397,361) $ 429,171 Shares issued under stock option and employee stock purchase plans 229,171 — 3,814 ​ ​ — — 3,814 Shares issued in underwritten offering, net 9,798,000 10 432,288 — — 432,298 Stock-based compensation — — 7,202 — — 7,202 Unrealized loss on marketable securities — — — (1,064) — (1,064) Net loss — — — — (32,808) ​ (32,808) Consolidated balance at March 31, 2024 65,910,548 $ 66 $ 2,266,472 $ 2,244 ​ $ (1,430,169) $ 838,613 Shares issued under stock option and employee stock purchase plans ​ 370,119 ​ ​ — ​ ​ 3,712 ​ ​ — ​ ​ — ​ ​ 3,712 Stock-based compensation ​ — ​ ​ — ​ ​ 7,640 ​ ​ — ​ ​ — ​ ​ 7,640 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (464) ​ ​ — ​ ​ (464) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (35,842) ​ ​ (35,842) Consolidated balance at June 30, 2024 ​ 66,280,667 ​ $ 66 ​ $ 2,277,824 ​ $ 1,780 ​ $ (1,466,011) ​ $ 813,659 Shares issued under stock option and employee stock purchase plans ​ 63,569 ​ ​ — ​ ​ 1,239 ​ ​ — ​ ​ — ​ ​ 1,239 Stock-based compensation ​ — ​ ​ — ​ ​ 9,620 ​ ​ — ​ ​ — ​ ​ 9,620 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 3,508 ​ ​ — ​ ​ 3,508 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (42,121) ​ ​ (42,121) Consolidated balance at September 30, 2024 ​ 66,344,236 ​ $ 66 ​ $ 2,288,683 ​ $ 5,288 ​ $ (1,508,132) ​ $ 785,905 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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, 2022 47,200,695 ​ $ 47 ​ $ 1,580,829 ​ $ 1,260 ​ $ (1,255,932) ​ $ 326,204 Shares issued under stock option and employee stock purchase plans 43,986 ​ — ​ 694 ​ — ​ — ​ 694 Stock-based compensation — ​ — ​ 4,340 ​ — ​ — ​ 4,340 Unrealized gain on marketable securities — ​ — ​ — ​ 863 ​ — ​ 863 Net loss — ​ — ​ — ​ — ​ (29,361) ​ (29,361) Consolidated balance at March 31, 2023 47,244,681 ​ $ 47 ​ $ 1,585,863 ​ $ 2,123 ​ $ (1,285,293) ​ $ 302,740 Shares issued under stock option and employee stock purchase plans 9,132 ​ — ​ 133 ​ — ​ — ​ 133 Stock-based compensation — ​ — ​ 5,217 ​ — ​ — ​ 5,217 Unrealized loss on marketable securities — ​ — ​ — ​ (51) ​ — ​ (51) Net loss — ​ — ​ — ​ — ​ (30,502) ​ (30,502) Consolidated balance at June 30, 2023 47,253,813 ​ $ 47 ​ $ 1,591,213 ​ $ 2,072 ​ $ (1,315,795) ​ $ 277,537 Shares issued under stock option and employee stock purchase plans ​ 10,384 ​ ​ — ​ ​ 257 ​ ​ — ​ ​ — ​ ​ 257 Stock-based compensation ​ — ​ ​ — ​ ​ 7,121 ​ ​ — ​ ​ — ​ ​ 7,121 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 63 ​ ​ — ​ ​ 63 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (38,260) ​ ​ (38,260) Consolidated balance at September 30, 2023 ​ 47,264,197 ​ $ 47 ​ $ 1,598,591 ​ $ 2,135 ​ $ (1,354,055) ​ $ 246,718 ​

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2024
Stock-Based Compensation
Stock-Based Compensation	(9) Stock-Based Compensation ​ A summary of stock option activity for the nine months ended September 30, 2024 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ Exercise ​ Remaining ​ ​ ​ ​ Price ​ Contractual ​ Shares Per Share Term (In Years) Options outstanding at December 31, 2023 6,378,924 ​ $ 29.69 ​ 7.5 Granted 1,907,820 ​ $ 36.42 ​ ​ Exercised (649,672) ​ $ 12.99 ​ ​ Canceled (109,968) ​ $ 120.83 ​ ​ Options outstanding at September 30, 2024 7,527,104 ​ $ 31.51 ​ 7.7 Options vested and expected to vest at September 30, 2024 7,381,038 ​ $ 31.44 ​ 7.7 Options exercisable at September 30, 2024 3,746,377 ​ $ 29.19 ​ 6.4 Shares available for grant under the Celldex Therapeutics, Inc. 2021 Omnibus Equity Incentive Plan (as amended, effective as of June 13, 2024) at September 30, 2024 2,415,651 ​ ​ ​ ​ ​ ​ The weighted average grant-date fair value of stock options granted during the three and nine months ended September 30, 2024 was $25.09 and $26.36, respectively. ​ The aggregate intrinsic value of stock options vested and expected to vest at September 30, 2024 was $54.4 million. The aggregate intrinsic value of stock options exercisable at September 30, 2024 was $46.2 million. As of September 30, 2024, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $85.4 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.7 years. ​ Stock-based compensation expense for the three and nine months ended September 30, 2024 and 2023 was recorded as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2024 2023 2024 2023 ​ ​ (In thousands) ​ (In thousands) Research and development ​ $ 4,880 ​ $ 3,618 ​ $ 12,457 ​ $ 8,269 General and administrative ​ 4,740 ​ 3,503 ​ 12,005 ​ 8,409 Total stock-based compensation expense ​ $ 9,620 ​ $ 7,121 ​ $ 24,462 ​ $ 16,678 ​ The fair values of employee, consultant and non-employee director stock options granted during the three and nine months ended September 30, 2024 and 2023 were valued using the Black-Scholes option pricing model with the following assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, 2024 2023 2024 2023 Expected stock price volatility 82% ​ 92% ​ 82 – 93% ​ 92% Expected option term 6.0 Years ​ 6.0 Years ​ 6.0 Years ​ 6.0 Years Risk-free interest rate 3.5 – 4.3% ​ 4.1% ​ 3.5 – 4.5% ​ 3.5 – 4.1% Expected dividend yield None ​ None ​ None ​ None ​

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2024
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income	(10) 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, 2024 are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) on ​ ​ ​ ​ ​ ​ ​ ​ Marketable ​ Foreign ​ ​ ​ ​ Securities Currency Items Total ​ ​ (In thousands) Balance at December 31, 2023 ​ $ 712 ​ $ 2,596 ​ $ 3,308 Other comprehensive loss ​ 1,980 ​ — ​ 1,980 Balance at September 30, 2024 ​ $ 2,692 ​ $ 2,596 ​ $ 5,288 ​ No amounts were reclassified out of accumulated other comprehensive income during the nine months ended September 30, 2024.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2024
Revenue
Revenue	(11) Revenue ​ Contract and Grants Revenue ​ The Company has entered into agreements with Rockefeller University (“Rockefeller”) 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 $3.2 million and $5.8 million in revenue under the agreements with Rockefeller during the three and nine months ended September 30, 2024, respectively, and $1.5 million and $2.7 million in revenue during the three and nine months ended September 30, 2023, respectively. ​ Contract Assets and Liabilities ​ At September 30, 2024 and December 31, 2023, the Company’s right to consideration under all contracts was considered unconditional, and as such, there were no recorded contract assets. At September 30, 2024, the Company had $0.5 million of 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, 2023, the Company had $3.1 million in contract liabilities recorded. Revenue recognized from contract liabilities as of December 31, 2023 during the nine months ended September 30, 2024 was $2.8 million.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Taxes
Income Taxes	(12) 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, 2024 and December 31, 2023. ​ The net deferred tax liability of $1.6 million at September 30, 2024 and December 31, 2023 relates to the temporary differences associated with the IPR&D intangible assets acquired in previous business combinations and is not deductible for tax purposes. ​ 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, 2024
Net Loss Per Share
Net Loss Per Share	(13) 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, ​ 2024 2023 Stock Options 7,527,104 6,407,584 Restricted Stock — — ​ 7,527,104 6,407,584 ​

Kolltan Acquisition

Kolltan Acquisition	9 Months Ended
	Sep. 30, 2024
Kolltan Acquisition
Kolltan Acquisition	(14) 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 payable in cash, in shares of Celldex’s common stock or a combination of both, in the sole discretion of Celldex and subject to provisions of the Agreement and Plan of Merger, dated November 1, 2016 (the “Merger Agreement”). ​ In October 2019, the Company received a letter from 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. ​ 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 (the “Litigation”). ​ On July 15, 2022, the Company entered into a definitive settlement agreement between the Company and SRS (the “Settlement Agreement”) and the Company and SRS jointly filed a Stipulation of Dismissal with prejudice relating to the Litigation on July 19, 2022. ​ Pursuant to the terms of the Settlement Agreement, all milestone payments provided for by the Merger Agreement were replaced in their entirety with the following payments, each of which is payable only once: ​ (i) The Company paid $ 15.0 million upon execution of the Settlement Agreement (the “Initial Payment”). ​ (ii) The Company paid $ 12.5 million upon the Successful Completion (as defined in the Settlement Agreement) of a Phase 2 Clinical Trial (as defined in the Merger Agreement) of barzolvolimab. (iii) The Company shall pay $ 52.5 million upon the first United States Food and Drug Administration or European Medicines Agency, or, in each case, any successor organization, regulatory approval of a Surviving Company Product (as defined in the Settlement Agreement). ​ The above payment obligations replace, in their entirety, the contingent consideration in the form of development, regulatory approval and sales-based milestones of up to $172.5 million contained in the Merger Agreement. Under the Settlement Agreement, each of the Company and SRS provided broad mutual releases of all claims relating to or arising out of the Merger Agreement, including without limitation, all claims brought in the Litigation or that could have been brought in the Litigation. The Company paid the Initial Payment in cash in July 2022. The Company paid the second milestone for “successful completion” of a Phase 2 Clinical Trial of barzolvolimab in cash in November 2023. A future milestone payment related to the barzolvolimab program, which was subject to the Litigation, will be recorded when and if payment becomes probable and reasonably estimable in accordance with the loss contingency model under ASC 450. A future milestone payment related to the remaining Surviving Company Products is measured at fair value (refer to Note 3). When and if the remaining payment described above becomes due, it shall be payable, at the Company’s sole election, in either cash or stock (as set forth in the Merger Agreement) or a combination thereof.

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Significant Accounting Policies
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“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 adoption of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements or disclosures. ​ In November 2023, the FASB issued ASU 2023-07 Segment Reporting - Improvements to Reportable Segment Disclosures ​ In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, ​ In March 2024, the SEC adopted final rules requiring public entities to provide certain climate-related information in their registration statements and annual reports. The rules require disclosure of, among other things: material climate-related risks; activities to mitigate or adapt to such risks; governance and management of such risks; and material greenhouse gas (GHG) emissions from operations owned or controlled (Scope 1) and/or indirect emissions from purchased energy consumed in operations (Scope 2). Additionally, the rules require disclosure in the notes to the financial statements of the effects of severe weather events and other natural conditions, subject to certain materiality thresholds. In April 2024, the SEC voluntarily stayed the new rules as a result of pending legal challenges. Absent the result of pending legal challenges, and the removal of the stay, the rules were to become effective on a phased-in timeline, with the first requirements to be adopted for the Company’s fiscal year beginning in 2025. The Company is assessing the effect of the new rules on its consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Measurements
Schedule of financial assets and liabilities subject to fair value measurements	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2024 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 25,292 ​ ​ — ​ $ 25,292 ​ ​ — Marketable securities ​ ​ 719,600 ​ ​ — ​ ​ 719,600 ​ ​ — ​ ​ $ 744,892 ​ ​ — ​ $ 744,892 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 19,803 ​ ​ — ​ $ 19,803 ​ ​ — Marketable securities ​ ​ 388,784 ​ ​ — ​ ​ 388,784 ​ ​ — ​ ​ $ 408,587 ​ ​ — ​ $ 408,587 ​ ​ —

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2024
Marketable Securities
Schedule of marketable debt securities, classified as available-for-sale	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Gross Unrealized ​ Gross Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) September 30, 2024 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 196,235 ​ $ 729 ​ $ — ​ $ 196,964 Maturing after one year through three years ​ ​ 107,595 ​ ​ 1,081 ​ ​ — ​ ​ 108,676 Total U.S. government and municipal obligations ​ $ 303,830 ​ $ 1,810 ​ $ — ​ $ 305,640 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 375,022 ​ $ 704 ​ $ (5) ​ $ 375,721 Maturing after one year through three years ​ ​ 38,057 ​ ​ 187 ​ ​ (5) ​ ​ 38,239 Total corporate debt securities ​ $ 413,079 ​ $ 891 ​ $ (10) ​ $ 413,960 Total marketable securities ​ $ 716,909 ​ $ 2,701 ​ $ (10) ​ $ 719,600 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Gross Unrealized ​ Gross Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (In thousands) December 31, 2023 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 132,459 ​ $ 143 ​ $ (53) ​ $ 132,549 Maturing after one year through three years ​ ​ 26,009 ​ ​ 77 ​ ​ — ​ ​ 26,086 Total U.S. government and municipal obligations ​ $ 158,468 ​ $ 220 ​ $ (53) ​ $ 158,635 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 183,625 ​ $ 300 ​ $ (10) ​ $ 183,915 Maturing after one year through three years ​ ​ 45,977 ​ ​ 257 ​ ​ — ​ ​ 46,234 Total corporate debt securities ​ $ 229,602 ​ $ 557 ​ $ (10) ​ $ 230,149 Total marketable securities ​ $ 388,070 ​ $ 777 ​ $ (63) ​ $ 388,784

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	9 Months Ended
	Sep. 30, 2024
Other Long-Term Liabilities
Schedule of other long-term liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2024 ​ 2023 ​ ​ (In thousands) Net deferred tax liabilities related to IPR&D (Note 12) ​ $ 1,613 ​ $ 1,613 Deferred income from sale of tax benefits ​ 2,790 ​ ​ 3,720 Deferred revenue (Note 11) ​ 466 ​ ​ 3,058 Total ​ 4,869 ​ ​ 8,391 Less current portion ​ (1,396) ​ ​ (3,988) Long-term portion ​ $ 3,473 ​ $ 4,403

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2024
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, 2023 55,883,377 $ 56 $ 1,823,168 $ 3,308 $ (1,397,361) $ 429,171 Shares issued under stock option and employee stock purchase plans 229,171 — 3,814 ​ ​ — — 3,814 Shares issued in underwritten offering, net 9,798,000 10 432,288 — — 432,298 Stock-based compensation — — 7,202 — — 7,202 Unrealized loss on marketable securities — — — (1,064) — (1,064) Net loss — — — — (32,808) ​ (32,808) Consolidated balance at March 31, 2024 65,910,548 $ 66 $ 2,266,472 $ 2,244 ​ $ (1,430,169) $ 838,613 Shares issued under stock option and employee stock purchase plans ​ 370,119 ​ ​ — ​ ​ 3,712 ​ ​ — ​ ​ — ​ ​ 3,712 Stock-based compensation ​ — ​ ​ — ​ ​ 7,640 ​ ​ — ​ ​ — ​ ​ 7,640 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (464) ​ ​ — ​ ​ (464) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (35,842) ​ ​ (35,842) Consolidated balance at June 30, 2024 ​ 66,280,667 ​ $ 66 ​ $ 2,277,824 ​ $ 1,780 ​ $ (1,466,011) ​ $ 813,659 Shares issued under stock option and employee stock purchase plans ​ 63,569 ​ ​ — ​ ​ 1,239 ​ ​ — ​ ​ — ​ ​ 1,239 Stock-based compensation ​ — ​ ​ — ​ ​ 9,620 ​ ​ — ​ ​ — ​ ​ 9,620 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 3,508 ​ ​ — ​ ​ 3,508 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (42,121) ​ ​ (42,121) Consolidated balance at September 30, 2024 ​ 66,344,236 ​ $ 66 ​ $ 2,288,683 ​ $ 5,288 ​ $ (1,508,132) ​ $ 785,905 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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, 2022 47,200,695 ​ $ 47 ​ $ 1,580,829 ​ $ 1,260 ​ $ (1,255,932) ​ $ 326,204 Shares issued under stock option and employee stock purchase plans 43,986 ​ — ​ 694 ​ — ​ — ​ 694 Stock-based compensation — ​ — ​ 4,340 ​ — ​ — ​ 4,340 Unrealized gain on marketable securities — ​ — ​ — ​ 863 ​ — ​ 863 Net loss — ​ — ​ — ​ — ​ (29,361) ​ (29,361) Consolidated balance at March 31, 2023 47,244,681 ​ $ 47 ​ $ 1,585,863 ​ $ 2,123 ​ $ (1,285,293) ​ $ 302,740 Shares issued under stock option and employee stock purchase plans 9,132 ​ — ​ 133 ​ — ​ — ​ 133 Stock-based compensation — ​ — ​ 5,217 ​ — ​ — ​ 5,217 Unrealized loss on marketable securities — ​ — ​ — ​ (51) ​ — ​ (51) Net loss — ​ — ​ — ​ — ​ (30,502) ​ (30,502) Consolidated balance at June 30, 2023 47,253,813 ​ $ 47 ​ $ 1,591,213 ​ $ 2,072 ​ $ (1,315,795) ​ $ 277,537 Shares issued under stock option and employee stock purchase plans ​ 10,384 ​ ​ — ​ ​ 257 ​ ​ — ​ ​ — ​ ​ 257 Stock-based compensation ​ — ​ ​ — ​ ​ 7,121 ​ ​ — ​ ​ — ​ ​ 7,121 Unrealized gain on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ 63 ​ ​ — ​ ​ 63 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (38,260) ​ ​ (38,260) Consolidated balance at September 30, 2023 ​ 47,264,197 ​ $ 47 ​ $ 1,598,591 ​ $ 2,135 ​ $ (1,354,055) ​ $ 246,718 ​

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2024
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, 2023 6,378,924 ​ $ 29.69 ​ 7.5 Granted 1,907,820 ​ $ 36.42 ​ ​ Exercised (649,672) ​ $ 12.99 ​ ​ Canceled (109,968) ​ $ 120.83 ​ ​ Options outstanding at September 30, 2024 7,527,104 ​ $ 31.51 ​ 7.7 Options vested and expected to vest at September 30, 2024 7,381,038 ​ $ 31.44 ​ 7.7 Options exercisable at September 30, 2024 3,746,377 ​ $ 29.19 ​ 6.4 Shares available for grant under the Celldex Therapeutics, Inc. 2021 Omnibus Equity Incentive Plan (as amended, effective as of June 13, 2024) at September 30, 2024 2,415,651 ​ ​ ​ ​ ​
Schedule of stock-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2024 2023 2024 2023 ​ ​ (In thousands) ​ (In thousands) Research and development ​ $ 4,880 ​ $ 3,618 ​ $ 12,457 ​ $ 8,269 General and administrative ​ 4,740 ​ 3,503 ​ 12,005 ​ 8,409 Total stock-based compensation expense ​ $ 9,620 ​ $ 7,121 ​ $ 24,462 ​ $ 16,678 ​
Schedule of assumptions used for the fair value of employee stock options granted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, 2024 2023 2024 2023 Expected stock price volatility 82% ​ 92% ​ 82 – 93% ​ 92% Expected option term 6.0 Years ​ 6.0 Years ​ 6.0 Years ​ 6.0 Years Risk-free interest rate 3.5 – 4.3% ​ 4.1% ​ 3.5 – 4.5% ​ 3.5 – 4.1% Expected dividend yield None ​ None ​ None ​ None ​

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2024
Accumulated Other Comprehensive Income
Summary of changes in accumulated other comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) on ​ ​ ​ ​ ​ ​ ​ ​ Marketable ​ Foreign ​ ​ ​ ​ Securities Currency Items Total ​ ​ (In thousands) Balance at December 31, 2023 ​ $ 712 ​ $ 2,596 ​ $ 3,308 Other comprehensive loss ​ 1,980 ​ — ​ 1,980 Balance at September 30, 2024 ​ $ 2,692 ​ $ 2,596 ​ $ 5,288

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2024
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, ​ 2024 2023 Stock Options 7,527,104 6,407,584 Restricted Stock — — ​ 7,527,104 6,407,584 ​

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Basis of Presentation
Cash, cash equivalents and marketable securities	$ 756,000						$ 756,000
Net loss	$ (42,121)	$ (35,842)	$ (32,808)	$ (38,260)	$ (30,502)	$ (29,361)	(110,771)	$ (98,123)
Net cash used in operations							$ (125,302)	$ (74,758)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Fair Value Measurements - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Level 2
Assets:
Money market funds and cash equivalents	$ 25,292	$ 19,803
Marketable securities	719,600	388,784
Total financial assets at fair value measurements	744,892	408,587
Fair value
Assets:
Money market funds and cash equivalents	25,292	19,803
Marketable securities	719,600	388,784
Total financial assets at fair value measurements	$ 744,892	$ 408,587

Fair Value Measurements - Addit

Fair Value Measurements - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Fair value measurements
Gain or loss on fair value remeasurement of contingent consideration	$ 0	$ 0	$ 0	$ 0
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 | Level 3
Fair value measurements
Contingent consideration liabilities	$ 0		$ 0		$ 0

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost
Amortized Cost	$ 716,909	$ 388,070
Gross Unrealized Gains
Gross Unrealized Gains	2,701	777
Gross Unrealized Losses
Gross Unrealized Losses	(10)	(63)
Fair Value
Fair Value	719,600	388,784
U.S. government and municipal obligations
Amortized Cost
Maturing in one year or less	196,235	132,459
Maturing after one year through three years	107,595	26,009
Amortized Cost	303,830	158,468
Gross Unrealized Gains
Maturing in one year or less	729	143
Maturing after one year through three years	1,081	77
Gross Unrealized Gains	1,810	220
Gross Unrealized Losses
Maturing in one year or less		(53)
Gross Unrealized Losses		(53)
Fair Value
Maturing in one year or less	196,964	132,549
Maturing after one year through three years	108,676	26,086
Fair Value	305,640	158,635
Corporate debt securities
Amortized Cost
Maturing in one year or less	375,022	183,625
Maturing after one year through three years	38,057	45,977
Amortized Cost	413,079	229,602
Gross Unrealized Gains
Maturing in one year or less	704	300
Maturing after one year through three years	187	257
Gross Unrealized Gains	891	557
Gross Unrealized Losses
Maturing in one year or less	(5)	(10)
Maturing after one year through three years	(5)
Gross Unrealized Losses	(10)	(10)
Fair Value
Maturing in one year or less	375,721	183,915
Maturing after one year through three years	38,239	46,234
Fair Value	$ 413,960	$ 230,149

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Marketable Securities
Unrealized loss	$ 28.6	$ 80.4
Accrued interest	$ 5.3	$ 1.9

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Intangible Assets
Indefinite-lived intangible assets	$ 27.2	$ 27.2

Other Assets (Details)

Other Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Other Assets
Advance payment	$ 9.6	$ 0

Other Long-Term Liabilities (De

Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Other Long-Term Liabilities
Net deferred tax liabilities related to IPR&D (Note 12)	$ 1,613	$ 1,613
Deferred income from sale of tax benefits	2,790	3,720
Deferred revenue (Note 11)	466	3,058
Total	4,869	8,391
Less current portion	(1,396)	(3,988)
Long-term portion	$ 3,473	$ 4,403

Other Long-Term Liabilities - A

Other Long-Term Liabilities - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2022	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other Long-Term Liabilities
Other income		$ 10,005	$ 2,979	$ 28,280	$ 8,792
New Jersey tax benefits
Other Long-Term Liabilities
Amount of tax benefit	$ 5,000
Proceeds from sale of tax credits	$ 4,700
Base of operations requirement (in years)	5 years
New Jersey Economic Development Authority
Other Long-Term Liabilities
Other income		$ 0	$ 0	$ 900	$ 900

Stockholders' Equity - Addition

Stockholders' Equity - Additional information (Details) - USD ($) $ in Thousands	1 Months Ended		9 Months Ended
	Mar. 31, 2024	Nov. 30, 2023	Sep. 30, 2024
Stockholders' Equity
Net proceeds from sale of common stock			$ 432,298
Underwritten Public Offering
Stockholders' Equity
Common stock issued (in shares)	9,798,000	8,538,750
Net proceeds from sale of common stock	$ 432,300	$ 216,200
ATM Agreement
Stockholders' Equity
Common stock to be sold pursuant			$ 300,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Increase (Decrease) in Stockholders' Equity
Balance, beginning	$ 813,659	$ 838,613	$ 429,171	$ 277,537	$ 302,740	$ 326,204	$ 429,171	$ 326,204
Balance, beginning (in shares)			55,883,377				55,883,377
Shares issued under stock option and employee stock purchase plans	1,239	3,712	$ 3,814	257	133	694
Shares issued in underwritten offering, net			432,298
Stock-based compensation	9,620	7,640	7,202	7,121	5,217	4,340
Unrealized gain on marketable securities	3,508	(464)	(1,064)	63	(51)	863	$ 1,980	875
Net loss	(42,121)	(35,842)	(32,808)	(38,260)	(30,502)	(29,361)	(110,771)	(98,123)
Balance, ending	$ 785,905	813,659	838,613	246,718	277,537	302,740	$ 785,905	246,718
Balance, ending (in shares)	66,344,236						66,344,236
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance, beginning	$ 66	$ 66	$ 56	$ 47	$ 47	$ 47	$ 56	$ 47
Balance, beginning (in shares)	66,280,667	65,910,548	55,883,377	47,253,813	47,244,681	47,200,695	55,883,377	47,200,695
Shares issued under stock option and employee stock purchase plans (in shares)	63,569	370,119	229,171	10,384	9,132	43,986
Shares issued in underwritten offering, net			$ 10
Shares issued in underwritten offering, net (in shares)			9,798,000
Balance, ending	$ 66	$ 66	$ 66	$ 47	$ 47	$ 47	$ 66	$ 47
Balance, ending (in shares)	66,344,236	66,280,667	65,910,548	47,264,197	47,253,813	47,244,681	66,344,236	47,264,197
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity
Balance, beginning	$ 2,277,824	$ 2,266,472	$ 1,823,168	$ 1,591,213	$ 1,585,863	$ 1,580,829	$ 1,823,168	$ 1,580,829
Shares issued under stock option and employee stock purchase plans	1,239	3,712	3,814	257	133	694
Shares issued in underwritten offering, net			432,288
Stock-based compensation	9,620	7,640	7,202	7,121	5,217	4,340
Balance, ending	2,288,683	2,277,824	2,266,472	1,598,591	1,591,213	1,585,863	2,288,683	1,598,591
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance, beginning	1,780	2,244	3,308	2,072	2,123	1,260	3,308	1,260
Unrealized gain on marketable securities	3,508	(464)	(1,064)	63	(51)	863
Balance, ending	5,288	1,780	2,244	2,135	2,072	2,123	5,288	2,135
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance, beginning	(1,466,011)	(1,430,169)	(1,397,361)	(1,315,795)	(1,285,293)	(1,255,932)	(1,397,361)	(1,255,932)
Net loss	(42,121)	(35,842)	(32,808)	(38,260)	(30,502)	(29,361)
Balance, ending	$ (1,508,132)	$ (1,466,011)	$ (1,430,169)	$ (1,354,055)	$ (1,315,795)	$ (1,285,293)	$ (1,508,132)	$ (1,354,055)

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Option and Incentive Plan (Details) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024 USD ($) $ / shares	Sep. 30, 2024 USD ($) $ / shares
Stock-Based Compensation
Weighted average grant-date fair value (in dollars per share) | $ / shares	$ 25.09	$ 26.36
Intrinsic value of stock options vested and expected to vest	$ 54.4	$ 54.4
Intrinsic value of stock options exercisable	46.2	46.2
Compensation cost not yet recognized	$ 85.4	$ 85.4
Weighted average period compensation cost is expected to be recognized (in years)		2 years 8 months 12 days

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - Employee Stock Option - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Shares
Options outstanding at beginning of the period	6,378,924
Granted	1,907,820
Exercised	(649,672)
Canceled	(109,968)
Options outstanding at the end of the period	7,527,104	6,378,924
Options vested and expected to vest at the end of the period	7,381,038
Options exercisable at the end of the period	3,746,377
Shares available for grant under the Celldex Therapeutics, Inc. 2021 Omnibus Equity Incentive Plan (as amended, effective as of June 13, 2024) at September 30, 2024	2,415,651
Weighted Average Exercise Price Per Share
Options outstanding at beginning of the period	$ 29.69
Granted	36.42
Exercised	12.99
Canceled	120.83
Options outstanding at the end of the period	31.51	$ 29.69
Options vested and expected to Vest at the end of the period	31.44
Options exercisable at the end of the period	$ 29.19
Weighted Average Remaining Contractual Term (In Years)
Options outstanding at the end of the period	7 years 8 months 12 days	7 years 6 months
Options vested and expected to vest at the end of the period	7 years 8 months 12 days
Options exercisable at the end of the period	6 years 4 months 24 days

Stock-Based Compensation - Expe

Stock-Based Compensation - Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Stock-Based Compensation
Total stock-based compensation expense	$ 9,620	$ 7,121	$ 24,462	$ 16,678
Research and development
Stock-Based Compensation
Total stock-based compensation expense	4,880	3,618	12,457	8,269
General and administrative
Stock-Based Compensation
Total stock-based compensation expense	$ 4,740	$ 3,503	$ 12,005	$ 8,409

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation (Details) - Employee Stock Option	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Black-Scholes option with following assumptions:
Expected stock price volatility (as a percent)	82%	92%		92%
Expected stock price volatility, minimum (as a percent)			82%
Expected stock price volatility, maximum (as a percent)			93%
Expected option term	6 years	6 years	6 years	6 years
Risk-free interest rate (as a percent)		4.10%
Risk-free interest rate, minimum (as a percent)	3.50%		3.50%	3.50%
Risk-free interest rate, maximum (as a percent)	4.30%		4.50%	4.10%
Expected dividend yield (as a percent)	0%	0%	0%	0%

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Accumulated Other Comprehensive Income
Balance, beginning	$ 429,171
Balance, ending	785,905
Amounts reclassified from AOCI	0
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Balance, beginning	3,308
Other comprehensive loss	1,980
Balance, ending	5,288
Unrealized Gain (Loss) on Marketable Securities
Accumulated Other Comprehensive Income
Balance, beginning	712
Other comprehensive loss	1,980
Balance, ending	2,692
Foreign Currency Items
Accumulated Other Comprehensive Income
Balance, beginning	2,596
Other comprehensive loss	0
Balance, ending	$ 2,596

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Revenue
Revenues	$ 3,191	$ 1,517	$ 5,845	$ 2,752
Contract assets	0		0		$ 0
Contract liability	466		466		$ 3,058
Revenue, contract liabilities			2,800
Contracts and grants
Revenue
Revenues	3,188	1,515	5,840	2,733
Rockefeller University | Contracts and grants
Revenue
Revenues	$ 3,200	$ 1,500	$ 5,800	$ 2,700

Income Taxes - Summary of defer

Income Taxes - Summary of deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Gross deferred tax liabilities
Net deferred tax liability	$ 1,613	$ 1,613

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Net Loss Per Share
Potentially dilutive common shares not been included in net loss per common share calculations because the effect would have been anti-dilutive	7,527,104	6,407,584
Stock Options
Net Loss Per Share
Potentially dilutive common shares not been included in net loss per common share calculations because the effect would have been anti-dilutive	7,527,104	6,407,584

Kolltan Acquisition (Details)

Kolltan Acquisition (Details) - Kolltan - USD ($) $ in Millions	Jul. 15, 2022	Nov. 29, 2016
Kolltan Acquisition
Shares issued as part of consideration (in shares)		1,217,200
Execution of the settlement agreement	$ 15
Milestone payments made in cash upon Successful Completion of a Phase 2 Clinical Trial	12.5
Milestone payment payable upon regulatory approval of a Surviving Company Product	52.5
Specified development, regulatory approvals or sales-based milestones
Kolltan Acquisition
Potential milestone payments		$ 172.5
Milestone payment payable upon regulatory approval of a Surviving Company Product	$ 172.5