​ CELLDEX THERAPEUTICS, INC. CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) ​ (In thousands, except share and per share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ ​ ​ 2026 ​ ​ ​ 2025 Assets ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 47,454 ​ $ 28,871 Marketable securities ​ 670,133 ​ 489,702 Accounts and other receivables ​ 230 ​ 2,015 Prepaid and other current assets ​ 7,114 ​ 14,076 Total current assets ​ 724,931 ​ 534,664 Property and equipment, net ​ 9,756 ​ 5,334 Operating lease right-of-use assets, net ​ ​ 5,038 ​ ​ 2,437 Intangible assets ​ 27,190 ​ 27,190 Other assets ​ 15,434 ​ 13,358 Total assets ​ $ 782,349 ​ $ 582,983 Liabilities and stockholders’ equity ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 14,675 ​ $ 1,180 Accrued expenses ​ 43,863 ​ 47,029 Current portion of operating lease liabilities ​ ​ 1,557 ​ ​ 1,552 Current portion of other long-term liabilities ​ 1,230 ​ 1,230 Total current liabilities ​ 61,325 ​ 50,991 Long-term portion of operating lease liabilities ​ ​ 3,347 ​ ​ 784 Other long-term liabilities ​ 3,113 ​ 4,043 Total liabilities ​ 67,785 ​ 55,818 Commitments and contingent liabilities ​ ​ ​ ​ ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ Convertible preferred stock, $.01 par value; 3,000,000 shares authorized; no shares issued and outstanding at June 30, 2026 and December 31, 2025 ​ — ​ — Common stock, $.001 par value; 297,000,000 shares authorized; 78,500,173 and 66,549,442 shares issued and outstanding at June 30, 2026 and December 31, 2025, respectively ​ 79 ​ 67 Additional paid-in capital ​ 2,679,356 ​ 2,337,453 Accumulated other comprehensive income ​ 1,298 ​ 3,626 Accumulated deficit ​ (1,966,169) ​ (1,813,981) Total stockholders’ equity ​ 714,564 ​ 527,165 Total liabilities and stockholders’ equity ​ $ 782,349 ​ $ 582,983 ​ See accompanying notes to unaudited condensed consolidated financial statements ​ 3 Table of Contents CELLDEX THERAPEUTICS, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) ​ (In thousands, except per share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Three Months Ended ​ Six Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 Revenues: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Product development and licensing agreements ​ $ 7 ​ $ 7 ​ $ 7 ​ $ 57 Contracts and grants ​ 15 ​ 723 ​ 30 ​ 1,367 Total revenues ​ 22 ​ 730 ​ 37 ​ 1,424 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ 67,542 ​ 54,196 ​ 140,543 ​ 106,810 General and administrative ​ 13,103 ​ 10,391 ​ 24,552 ​ 21,211 Total operating expenses ​ 80,645 ​ 64,587 ​ 165,095 ​ 128,021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating loss ​ (80,623) ​ (63,857) ​ (165,058) ​ (126,597) Investment and other income, net ​ 7,120 ​ 7,257 ​ 12,870 ​ 16,201 Net loss ​ $ (73,503) ​ $ (56,600) ​ $ (152,188) ​ $ (110,396) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and diluted net loss per common share ​ $ (0.94) ​ $ (0.85) ​ $ (2.11) ​ $ (1.66) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shares used in calculating basic and diluted net loss per share ​ 77,840 ​ 66,392 ​ 72,234 ​ 66,388 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Comprehensive loss: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (73,503) ​ $ (56,600) ​ $ (152,188) ​ $ (110,396) Other comprehensive (loss) income: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized (loss) gain on marketable securities ​ (1,224) ​ (229) ​ (2,328) ​ 25 Comprehensive loss ​ $ (74,727) ​ $ (56,829) ​ $ (154,516) ​ $ (110,371) ​ See accompanying notes to unaudited condensed consolidated financial statements ​ 4 Table of Contents CELLDEX THERAPEUTICS, INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (In thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 Cash flows from operating activities: ​ ​ ​ ​ ​ ​ Net loss ​ $ (152,188) ​ $ (110,396) Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ Depreciation and amortization ​ 1,756 ​ 1,740 Amortization and premium of marketable securities, net ​ (2,328) ​ (3,955) Loss on sale or disposal of assets ​ ​ 4 ​ ​ 6 Stock-based compensation expense ​ 16,931 ​ 18,507 Changes in operating assets and liabilities: ​ ​ ​ ​ ​ ​ Accounts and other receivables ​ 1,785 ​ 610 Prepaid and other current assets ​ 5,116 ​ 3,020 Other assets ​ ​ (2,076) ​ ​ 447 Accounts payable and accrued expenses ​ 9,850 ​ (6,632) Other liabilities ​ (1,848) ​ (1,724) Net cash used in operating activities ​ (122,998) ​ (98,377) Cash flows from investing activities: ​ ​ ​ ​ ​ ​ Sales and maturities of marketable securities ​ 283,876 ​ 367,873 Purchases of marketable securities ​ (462,461) ​ (274,080) Acquisition of property and equipment ​ ​ (4,818) ​ ​ (993) Net cash (used in) provided by investing activities ​ (183,403) ​ 92,800 Cash flows from financing activities: ​ ​ ​ ​ ​ ​ Net proceeds from stock issuances ​ ​ 323,832 ​ ​ — Proceeds from issuance of stock from employee benefit plans ​ 1,152 ​ 265 Net cash provided by financing activities ​ 324,984 ​ 265 ​ ​ ​ ​ ​ ​ ​ Net increase (decrease) in cash and cash equivalents ​ 18,583 ​ (5,312) Cash and cash equivalents at beginning of period ​ 28,871 ​ 28,356 Cash and cash equivalents at end of period ​ $ 47,454 ​ $ 23,044 ​ ​ ​ ​ ​ ​ ​ Non-cash investing activities ​ ​ ​ ​ ​ ​ Accrued construction in progress ​ $ 577 ​ $ 49 ​ See accompanying notes to unaudited condensed consolidated financial statements ​ 5 Table of Contents CELLDEX THERAPEUTICS, INC. Notes to Unaudited Condensed Consolidated Financial Statements June 30, 2026 (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, 2025, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 25, 2026. 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, 2026. At June 30, 2026, the Company had cash, cash equivalents and marketable securities of $717.6 million. The Company has had recurring losses and incurred a loss of $152.2 million for the six months ended June 30, 2026. Net cash used in operations for the six months ended June 30, 2026 was $123.0 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 16), 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. ​ 6 Table of Contents (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 six months ended June 30, 2026 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, 2025. 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 2024, the FASB issued ASU 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures, which requires enhanced disclosures about specific types of expenses included in the expense captions presented on the face of the income statement. The standard is effective for annual reporting periods in fiscal years beginning after December 15, 2026, and interim reporting periods in fiscal years beginning after December 31, 2027, with early adoption permitted. The Company is currently evaluating the impact that the adoption of ASU 2024-03 may have on its expense disclosures in the notes to the consolidated financial statements. (3) Segment Information The Company is managed as a single operating and reportable segment that operates in the business of development, manufacturing and commercialization of novel therapeutics for human health care. Our chief operating decision maker (“CODM”), the Chief Executive Officer, evaluates performance based on consolidated net loss. Other than general and administrative expenses as presented on the consolidated statement of operations, research and development expense disaggregated by program and by nature are considered to be the Company’s significant segment expenses. These results are used, in part, by our CODM in evaluating the performance of the Company by comparing budget to actual results, and to allocate resources. All revenue is derived in and long-lived assets are located in the United States. The CODM does not receive asset information other than what is presented on the consolidated balance sheets. The following table is a summary of the Company’s research and development expenses disaggregated by program. The amounts disclosed reflect direct research and development costs and an allocation of indirect research and development costs to each program. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Three Months Ended ​ Six Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 ​ ​ (In thousands) Barzolvolimab/Anti-KIT Program ​ $ 54,946 ​ $ 42,645 ​ $ 117,110 ​ $ 82,348 CDX-622 ​ 3,501 ​ 3,838 ​ 7,795 ​ 9,289 Other Programs (a) ​ 9,095 ​ 7,713 ​ 15,638 ​ 15,173 Total R&D Expense ​ $ 67,542 ​ $ 54,196 ​ $ 140,543 ​ $ 106,810 ​ (a) Other program expenses primarily include research and development expenses related to early-stage programs, revenue-generating programs and discontinued programs. 7 Table of Contents The following table is a summary of the Company’s research and development expenses disaggregated by nature. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Three Months Ended ​ Six Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 ​ ​ ​ June 30, 2026 ​ ​ ​ June 30, 2025 ​ (In thousands) Personnel ​ $ 15,885 ​ $ 14,129 ​ $ 31,454 ​ $ 27,729 Laboratory supplies ​ 2,593 ​ 1,544 ​ 4,051 ​ 3,712 Facility ​ 1,178 ​ 1,398 ​ 2,118 ​ 2,803 Product development (b) ​ 41,746 ​ 33,536 ​ 91,903 ​ 65,702 Other expenses (c) ​ 6,140 ​ 3,589 ​ 11,017 ​ 6,864 Total R&D expense ​ $ 67,542 ​ $ 54,196 ​ $ 140,543 ​ $ 106,810 ​ (b) Product development expenses include clinical investigator site fees, external trial monitoring costs, data accumulation costs, contracted research and outside clinical drug product manufacturing. (c) Other expenses primarily include research and development consulting, insurance, licensing and software expenses. (4) Fair Value Measurements The following tables set forth the Company’s financial assets and liabilities subject to fair value measurements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2026 ​ ​ ​ Level 1 ​ ​ ​ Level 2 ​ ​ ​ Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 33,273 ​ ​ — ​ $ 33,273 ​ ​ — Marketable securities ​ ​ 670,133 ​ ​ — ​ ​ 670,133 ​ ​ — ​ ​ $ 703,406 ​ ​ — ​ $ 703,406 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2025 ​ ​ ​ Level 1 ​ ​ ​ Level 2 ​ ​ ​ Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds and cash equivalents ​ $ 19,115 ​ ​ — ​ $ 19,115 ​ ​ — Marketable securities ​ ​ 489,702 ​ ​ — ​ ​ 489,702 ​ ​ — ​ ​ $ 508,817 ​ ​ — ​ $ 508,817 ​ ​ — ​ 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 June 30, 2026 and December 31, 2025. 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 six months ended June 30, 2026 or June 30, 2025. 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 or liabilities during the six months ended June 30, 2026 or June 30, 2025. 8 Table of Contents (5) 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) June 30, 2026 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 165,974 ​ $ 50 ​ $ (261) ​ $ 165,763 Maturing after one year through three years ​ ​ 101,406 ​ ​ — ​ ​ (504) ​ ​ 100,902 Total U.S. government and municipal obligations ​ $ 267,380 ​ $ 50 ​ $ (765) ​ $ 266,665 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 325,803 ​ $ 35 ​ $ (449) ​ $ 325,389 Maturing after one year through three years ​ ​ 78,248 ​ ​ — ​ ​ (169) ​ ​ 78,079 Total corporate debt securities ​ $ 404,051 ​ $ 35 ​ $ (618) ​ $ 403,468 Total marketable securities ​ $ 671,431 ​ $ 85 ​ $ (1,383) ​ $ 670,133 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Gross Unrealized ​ Gross Unrealized ​ Fair ​ ​ ​ ​ Cost ​ ​ ​ Gains ​ ​ ​ Losses ​ ​ ​ Value ​ ​ (In thousands) December 31, 2025 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and municipal obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 151,270 ​ $ 479 ​ $ — ​ $ 151,749 Maturing after one year through three years ​ ​ 42,358 ​ ​ 127 ​ ​ — ​ ​ 42,485 Total U.S. government and municipal obligations ​ $ 193,628 ​ $ 606 ​ $ — ​ $ 194,234 Corporate debt securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Maturing in one year or less ​ $ 257,064 ​ $ 373 ​ $ — ​ $ 257,437 Maturing after one year through three years ​ ​ 37,980 ​ ​ 55 ​ ​ (4) ​ ​ 38,031 Total corporate debt securities ​ $ 295,044 ​ $ 428 ​ $ (4) ​ $ 295,468 Total marketable securities ​ $ 488,672 ​ $ 1,034 ​ $ (4) ​ $ 489,702 ​ 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 June 30, 2026 and December 31, 2025 was $536.9 million and $19.4 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 the Company’s credit risk. As a result, the Company determined it did not hold any investments with a credit loss at June 30, 2026 and December 31, 2025. Marketable securities include $6.3 million and $4.4 million in accrued interest at June 30, 2026 and December 31, 2025, respectively. 9 Table of Contents (6) Leases In June 2026, the Company entered into an amendment to its Hampton, New Jersey lease to expand its leased space from approximately 33,400 square feet to approximately 66,000 square feet and extend the lease term by an additional 36 months. As a result of the lease modification, the Company’s operating lease right-of-use asset and operating lease liability increased by $3.5 million during the quarter ended June 30, 2026. The lease modification also increased the Company’s undiscounted future lease payments under non-cancellable operating leases by approximately $4.4 million through 2030. (7) Intangible Assets At June 30, 2026 and December 31, 2025, 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 June 30, 2026, 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. (8) 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 $14.8 million and $12.8 million at June 30, 2026 and December 31, 2025, respectively. (9) Other Long-Term Liabilities Other long-term liabilities include the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ ​ ​ December 31, ​ ​ 2026 ​ 2025 ​ ​ (In thousands) Net deferred tax liabilities related to IPR&D (Note 14) ​ $ 1,613 ​ $ 1,613 Deferred income from sale of tax benefits ​ 930 ​ ​ 1,860 Deferred revenue (Note 13) ​ 1,800 ​ ​ 1,800 Total ​ 4,343 ​ ​ 5,273 Less current portion ​ (1,230) ​ ​ (1,230) Long-term portion ​ $ 3,113 ​ $ 4,043 ​ 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 during the three and six months ended June 30, 2026, respectively, and $0.0 million and $0.9 million during the three and six months ended June 30, 2025, respectively. 10 Table of Contents (10) 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. 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. At June 30, 2026, 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 April 2026, the Company issued 11,896,750 shares of its common stock in an underwritten public offering resulting in net proceeds to the Company of $323.8 million, after deducting underwriting fees and offering expenses. The changes in Stockholders’ Equity during the three and six months ended June 30, 2026 and 2025 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, 2025 66,549,442 ​ $ 67 ​ $ 2,337,453 ​ $ 3,626 ​ $ (1,813,981) ​ $ 527,165 Shares issued under stock option and employee stock purchase plans 19,529 ​ ​ — ​ ​ 327 ​ ​ — ​ ​ — ​ ​ 327 Stock-based compensation — ​ ​ — ​ ​ 8,523 ​ ​ — ​ ​ — ​ ​ 8,523 Unrealized loss on marketable securities — ​ ​ — ​ ​ — ​ ​ (1,104) ​ ​ — ​ ​ (1,104) Net loss — ​ ​ — ​ ​ — ​ ​ — ​ ​ (78,685) ​ ​ (78,685) Consolidated balance at March 31, 2026 66,568,971 ​ $ 67 ​ $ 2,346,303 ​ $ 2,522 ​ $ (1,892,666) ​ $ 456,226 Shares issued under stock option and employee stock purchase plans ​ 34,452 ​ ​ — ​ ​ 825 ​ ​ — ​ ​ — ​ ​ 825 Shares issued in underwritten offering, net ​ 11,896,750 ​ ​ 12 ​ ​ 323,820 ​ ​ — ​ ​ — ​ ​ 323,832 Stock-based compensation ​ — ​ ​ — ​ ​ 8,408 ​ ​ — ​ ​ — ​ ​ 8,408 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (1,224) ​ ​ — ​ ​ (1,224) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (73,503) ​ ​ (73,503) Consolidated balance at June 30, 2026 ​ 78,500,173 ​ $ 79 ​ $ 2,679,356 ​ $ 1,298 ​ $ (1,966,169) ​ $ 714,564 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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, 2024 66,374,549 $ 66 $ 2,298,849 $ 3,314 $ (1,555,224) $ 747,005 Shares issued under stock option and employee stock purchase plans 9,642 — 202 — — 202 Stock-based compensation — — 9,316 — — 9,316 Unrealized gain on marketable securities — — — 254 — 254 Net loss — — — — (53,796) ​ (53,796) Consolidated balance at March 31, 2025 66,384,191 ​ $ 66 ​ $ 2,308,367 ​ $ 3,568 ​ $ (1,609,020) ​ $ 702,981 Shares issued under stock option and employee stock purchase plans ​ 10,050 ​ ​ — ​ ​ 63 ​ ​ — ​ ​ — ​ ​ 63 Stock-based compensation ​ — ​ ​ — ​ ​ 9,191 ​ ​ — ​ ​ — ​ ​ 9,191 Unrealized loss on marketable securities ​ — ​ ​ — ​ ​ — ​ ​ (229) ​ ​ — ​ ​ (229) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (56,600) ​ ​ (56,600) Consolidated balance at June 30, 2025 ​ 66,394,241 ​ $ 66 ​ $ 2,317,621 ​ $ 3,339 ​ $ (1,665,620) ​ $ 655,406 ​ ​ ​ ​ 11 Table of Contents (11) Stock-Based Compensation A summary of stock option activity for the six months ended June 30, 2026 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ Exercise ​ Remaining ​ ​ ​ ​ Price ​ Contractual ​ ​ ​ ​ Shares ​ ​ ​ Per Share ​ ​ ​ Term (In Years) Options outstanding at December 31, 2025 9,134,278 ​ $ 26.49 ​ 7.1 Granted 2,588,670 ​ $ 33.83 ​ — Exercised (41,894) ​ $ 22.30 ​ — Canceled (250,328) ​ $ 42.97 ​ — Options outstanding at June 30, 2026 11,430,726 ​ $ 27.80 ​ 7.5 Options vested and expected to vest at June 30, 2026 11,288,830 ​ $ 27.77 ​ 7.4 Options exercisable at June 30, 2026 6,194,728 ​ $ 25.60 ​ 6.0 Shares available for grant under the Celldex Therapeutics, Inc. 2021 Omnibus Equity Incentive Plan (as amended, effective as of June 25, 2026) at June 30, 2026 3,686,494 ​ ​ ​ ​ ​ ​ The weighted average grant-date fair value of stock options granted during the three and six months ended June 30, 2026 was $20.96 and $20.90, respectively. The aggregate intrinsic value of stock options vested and expected to vest at June 30, 2026 was $107.2 million. The aggregate intrinsic value of stock options exercisable at June 30, 2026 was $72.5 million. As of June 30, 2026, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $98.5 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 3.0 years. Stock-based compensation expense for the three and six months ended June 30, 2026 and 2025 was recorded as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ (In thousands) ​ (In thousands) Research and development ​ $ 4,588 ​ $ 4,882 ​ $ 9,235 ​ $ 9,467 General and administrative ​ 3,820 ​ 4,309 ​ 7,696 ​ 9,040 Total stock-based compensation expense ​ $ 8,408 ​ $ 9,191 ​ $ 16,931 ​ $ 18,507 ​ The fair values of employee, consultant and non-employee director stock options granted during the three and six months ended June 30, 2026 and 2025 were valued using the Black-Scholes option pricing model with the following assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ 2026 ​ ​ ​ 2025 Expected stock price volatility 63 – 74% ​ 76% ​ 63 – 76% ​ 76 – 81% Expected option term 6.0 Years ​ 6.0 Years ​ 6.0 Years ​ 6.0 Years Risk-free interest rate 4.0 – 4.4% ​ 4.1 – 4.3% ​ 3.8 – 4.4% ​ 4.1 – 4.7% Expected dividend yield None ​ None ​ None ​ None ​ ​ ​ 12 Table of Contents (12) Accumulated Other Comprehensive Income The changes in accumulated other comprehensive income, which is reported as a component of stockholders’ equity, for the six months ended June 30, 2026 are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) on ​ ​ ​ ​ ​ ​ ​ ​ Marketable ​ Foreign ​ ​ ​ ​ ​ ​ ​ Securities ​ ​ ​ Currency Items ​ ​ ​ Total ​ ​ (In thousands) Balance at December 31, 2025 ​ $ 1,030 ​ $ 2,596 ​ $ 3,626 Other comprehensive loss ​ (2,328) ​ — ​ (2,328) Balance at June 30, 2026 ​ $ (1,298) ​ $ 2,596 ​ $ 1,298 ​ No amounts were reclassified out of accumulated other comprehensive income during the six months ended June 30, 2026. (13) 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 no material revenue under the agreements with Rockefeller during the three and six months ended June 30, 2026. The Company recognized $0.7 million and $1.4 million under the agreements with Rockefeller during the three and six months ended June 30, 2025, respectively. Contract Assets and Liabilities At June 30, 2026 and December 31, 2025, the Company’s right to consideration under all contracts were considered unconditional, and as such, no contract assets were recorded. Accordingly, amounts billed but not yet paid by customers were recorded as trade receivables at June 30, 2026 and December 31, 2025. At June 30, 2026, the Company had $1.8 million in contract liabilities recorded, representing consideration billed in advance of performing manufacturing and research and development services. The Company expects to recognize this amount as revenue over the next 24 months as the related services are performed. At December 31, 2025, the Company had $1.8 million in contract liabilities recorded. No revenue was recognized from contract liabilities as of December 31, 2025 during the six months ended June 30, 2026. (14) Income Taxes On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was enacted in the United States. The OBBBA includes significant corporate tax reforms, including (i) the permanent reinstatement of deducting domestic research and development expenditures as incurred (under prior law such expenditures were capitalized and amortized over five years) and (ii) the option to claim 100% accelerated depreciation deductions on qualified property. The corporate tax changes included in the OBBBA did not have a material impact on our effective income tax rate during the three and six months ended June 30, 2026, and we do not anticipate a material impact on our effective income tax rate in future periods. 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 June 30, 2026 and December 31, 2025. 13 Table of Contents The net deferred tax liability of $1.6 million at June 30, 2026 and December 31, 2025 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. (15) 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: ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, ​ ​ ​ ​ 2026 ​ ​ ​ 2025 Stock Options 11,430,726 9,290,328 Restricted Stock — — ​ 11,430,726 9,290,328 ​ ​ (16) 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. 14 Table of Contents 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 4). 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. ​ 15 Table of Contents