Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. To the extent required, the disclosure required by this item is included in

Unregistered Sales of Equity Securities. The disclosure required by this item is included in

Entry into a Material Definitive Agreement. On August 12, 2026, Agenus West, LLC (the “Borrower”), a subsidiary of Agenus Inc. (the “Company”), and the Company, as guarantor, entered into a Second Loan Modification Agreement (the “Loan Modification Agreement”) with Ocean 1181 LLC (the “Lender”) relating to the promissory note previously entered into with the Lender on November 26, 2024, as previously amended and restated, and previously disclosed by the Company in its Current Report on Form 8…

CEO — Garo H. Armen: The filing discloses a compensatory stock option award to the sitting CEO, not a change in management personnel or role.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. On July 13, 2026, Agenus Inc. (the “Company”) entered into a Securities Purchase Agreement (the “Purchase Agreement”) for a private placement (the “Private Placement”) with certain institutional and other accredited investors (each, a “Purchaser” and collectively, the “Purchasers”). The closing of the Private Placement (the “Closing”) is expected to occur on July 15, 2026, subject to the satisfaction of customary closing conditions. Under the terms…

Other Events. On July 13, 2026, in connection with the Private Placement, the Company also announced that it will conduct, and the net proceeds of the Private Placement are expected to support, a strategic prioritization of botensilimab and balstilimab (“BOT+BAL”) for the neoadjuvant treatment of microsatellite-stable (“MSS”) colon cancer, including the advancement of ROBBIN, the Company’s planned registrational Phase 3 neoadjuvant trial in MSS colon cancer. High-risk Stage II and Stage III M…

Regulation FD Disclosure. On July 13, 2026, the Company made available a press release announcing the Private Placement and certain corporate updates. A copy of the press release is furnished as Exhibit 99.1 to this Form 8-K. On July 13, 2026, the Company made available on its website, www.agenusbio.com, a presentation to be used in meetings with investors in July 2026. A copy of the presentation is furnished as Exhibit 99.2 to this Form 8-K. The information in

Unregistered Sales of Equity Securities. The information contained in

of the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission on February 26, 2015 (the “February 2025 Current Report”) and such brief description is incorporated by reference herein. The forms of the Amended A Warrant, the Amended B Warrant and the C Warrant were previously filed as Exhibits 4.1, 4.2 and 4.3, respectively, to the February 2025 Current Report. The securities issued in connection with the Amendment were issued in reliance on the exemption from r…

Unregistered Sales of Equity Securities. The information provided above under

Entry into a Material Definitive Agreement. On June 29, 2026, Agenus Inc. (the “Company”) entered into an Amendment to Notes, Extension of Warrants and Sale of New Warrants (the “Amendment”) with existing noteholders, pursuant to which the Company: • extended the maturity date of $5.09 million of senior subordinated promissory notes previously issued by the Company to such noteholders in 2015 (the “2015 Notes”) by eight months from June 20, 2026 to February 18, 2027 (all other terms of the 20…

Principal Accounting Officer — Austin Charette: Austin Charette resigned as Principal Accounting Officer.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, except as expressly set forth by specific reference in such filing.

Other Events. On March 24, 2026, the United States District Court for the District of Massachusetts issued a Memorandum and Order in Byron Olsen, Individually and on Behalf of All Others Similarly Situated v. Agenus Inc., Garo H. Armen, Christine M. Klaskin, Steven J. O'Day, and Todd Yancey, Civil Action No. 24-CV-12299-AK, a putative securities class action alleging violations of the federal securities laws in connection with the Company’s public disclosures. The court granted defendants’ mo…

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, except as expressly set forth by specific reference in such filing.

Completion of Acquisition or Disposition of Assets. As previously disclosed, on June 3, 2025, Agenus Inc. (the “Company”) and its wholly-owned subsidiary Agenus West, LLC (“Agenus West” and together with the Company, “Agenus”) entered into an Asset Purchase Agreement (the “Purchase Agreement”) with Zydus Pharmaceuticals (USA) Inc. (subsequently assigned to Zydilac Bio, LLC, “Zydus”), a wholly-owned subsidiary of Zydus Lifesciences Limited, for the sale to Zydus of substantially all of the ass…

Unregistered Sales of Equity Securities. As previously disclosed, on June 3, 2025, and in connection with the execution of the Purchase Agreement referred to in Item 2.01, the Company and Zynext Ventures USA LLC (“Zynext”), a wholly-owned subsidiary of ZyNext Ventures PTE. LTD Singapore, a wholly-owned subsidiary of Zydus Lifesciences Limited, entered into a Securities Purchase Agreement (the “SPA”), pursuant to which Zynext agreed to purchase 2,133,333 shares of the Company’s common stock (t…

interim Chief Financial Officer (CFO) — Dr. Garo Armen: Dr. Garo Armen, the current Chairman and CEO, was appointed as interim CFO.

SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 8, 2026 By: /s/ Garo H. Armen Garo H. Armen, Chairman and CEO

Entry into a Material Definitive Agreement. On January 3, 2026, Agenus Inc. (the “Company”), Agenus Royalty Fund, LLC and Agenus Holdings 2024, LLC entered into an amendment and release agreement (the “Amendment Agreement”) with Ligand Pharmaceuticals Incorporated (“Ligand”) related to a Purchase and Sale Agreement and related Warrant each previously disclosed in the Company’s Current Report on Form 8-K filed with the SEC on May 7, 2024. The Amendment Agreement provides for a release by Ligan…

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. Promissory Note Agreement On October 8, 2025, Agenus Inc. (“Agenus”) entered into a Promissory Note Agreement (the “Note”) with Zydus Pharmaceuticals (USA) Inc. (“Zydus”), a wholly owned subsidiary of Zydus Lifesciences Limited, for up to $10,000,000 (the “Principal Amount”). The Note bears interest at 3.81% per annum and matures upon the closing of the Asset Purchase Agreement and Securities Purchase Agreement signed by Agenus and Zydus on June 3,…

by reference. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 9, 2025 By: /s/ Garo H. Armen, Ph.D. Garo H. Armen, Ph.D., Chairman & CEO

Other Events. As previously announced on June 3, 2025, the Company and Zydus Pharmaceuticals (USA) Inc. entered agreements pursuant to which, (i) under an asset purchase agreement Zydus will acquire assets comprising the Company’s manufacturing operations, (ii) under a stock purchase agreement Zydus will acquire a minority position in the Company and (iii) under a license agreement Zydus will receive certain commercial rights in India and Sri Lanka relating to intellectual property associated…