AGENUS INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant☒

Filed by a Party other than the Registrant☐

Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material Pursuant to §240.14a-12

Agenus Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

A list of stockholders entitled to vote will be open for examination by any stockholder for any purpose germane to the 2025 Annual Meeting of Stockholders for ten days before the meeting during ordinary business hours at our principal offices at 3 Forbes Road, Lexington, Massachusetts 02421.

It is important that your shares be represented at the 2025 Annual Meeting of Stockholders. Therefore, whether or not you plan to attend the meeting virtually, please complete your proxy and return it to us. If you attend the 2025 Annual Meeting of Stockholders virtually and wish to vote at the meeting, your proxy will not be used. You may also vote your shares over the internet or by telephone. Instructions for internet or telephonic voting are printed on your proxy card.

By order of the Board of Directors,

Garo H. Armen, Chief Executive Officer

April 30, 2025

TABLE OF CONTENTS

3 Forbes Road

Lexington, Massachusetts 02421

Telephone: (781) 674-4400

PROXY STATEMENT

April 30, 2025

This proxy statement contains information about the 2025 Annual Meeting of Stockholders of Agenus Inc. (the “Annual Meeting”), including any postponements or adjournments of the meeting. The Annual Meeting will be held virtually by live audio web conference at www.virtualshareholdermeeting.com/AGEN2025 on June 17, 2025 at 10:30 A.M., Eastern Time.

In this proxy statement, we refer to Agenus Inc. as “Agenus,” “us,” “we” or the “Company.”

This proxy statement and solicitation is being made on behalf of the Board of Directors of Agenus. In accordance with the “notice and access” rules approved by the Securities and Exchange Commission (“SEC”) and in connection with the solicitation of proxies by our Board of Directors, on or about April 30, 2025 we first sent a Notice of Internet Availability of Proxy Materials and provided access to our proxy materials (consisting of this proxy statement, our Annual Report on Form 10-K for the year ended December 31, 2024 and a form of proxy) over the internet to each stockholder entitled to vote at the Annual Meeting. We intend to mail to requesting stockholders full sets of our proxy materials (consisting of this proxy statement, our Annual Report on Form 10-K for the year ended December 31, 2024 and a form of proxy) on or about April 30, 2025.

Our Annual Report on Form 10-K for the year ended December 31, 2024 is also available on our corporate website athttps://investor.agenusbio.com/financial-information/sec-filingsand through the SEC’s EDGAR system athttp://www.sec.gov. To request a printed copy of our Annual Report on Form 10-K, which we will provide to you without charge, write to Investor Relations, Agenus Inc., 3 Forbes Road, Lexington, Massachusetts 02421. No material on our website is part of this proxy statement.