members to assess the effectiveness of the Board and its committees. Using these surveys, the Lead Director assesses the Board’s performance and the performance of individual members, and reports his conclusions to the full Board. The assessment also evaluates the Board’s effectiveness in reviewing executive management, conducting appropriate oversight and adding value to Agenus. Each of the Board’s standing committees also conducts annual self-evaluations.

At each Board meeting, each Board member has the opportunity to assess the effectiveness of the materials presented and the conduct of the meeting, and to offer suggestions for improvement at future meetings.

Code of Business Conduct and Ethics

The Board originally adopted our Code of Business Conduct and Ethics (the “Code of Ethics”) in 2003. The Board reviewed, revised, and updated the Code of Ethics most recently in January 2020. The Code of Ethics applies to all members of the Board and all employees of Agenus, including our Chief Executive Officer, President and Principal Financial and Accounting Officer. Among other matters, our Code of Ethics prohibits the members of the Board and all employees of Agenus from buying or selling our securities while in possession of material,non-public information about the Company. Our Code of Ethics is posted on the corporate governance section of our website athttp://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement. We intend to post on our website all disclosures that are required by law or Nasdaq listing rules concerning any amendments to, or waivers from, our Code of Ethics. Stockholders may request a free copy of our Code of Ethics by writing to Investor Relations, Agenus Inc., 3 Forbes Road, Lexington, MA 02421.

Independence of DirectorsAUTHORIZED SHARES OF COMMON STOCK FROM 400,000,000 TO 800,000,000

Our Governance Guidelines and Nasdaq listing rules provide that a majorityBoard has approved, subject to stockholder approval, an amendment to our Articles of Incorporation to increase our authorized shares of common stock from 400,000,000 to 800,000,000. The increase in our authorized shares of common stock will become effective upon the filing of the Board should be composedamendment to our Articles of independent directors. Incorporation with the Delaware Secretary of State. If the amendment to increase our authorized shares of common stock is approved by stockholders at the Special Meeting, we intend to file the amendment to our Articles of Incorporation as soon as practicable following the Special Meeting.

The Corporate Governance and Nominating Committee annually reviews the independenceform of the directorstext of the amendment (which would be filed with the Delaware Secretary of State on its then prescribed form of Certificate of Amendment) is set forth as Appendix A to this proxy statement (subject to any changes required by applicable law).

Outstanding Shares and reports toPurpose of the Board which directors it recommends that the Board determine are independent. The Board then makes the final determination. The Board takes into account Nasdaq listing rules, applicable laws and regulations, and other factors in making its determinations including potential conflicts of interest, transactions, and other relationships that would reasonably be expected to compromise a director’s independence. The Board has determined that Mr. Corvese, Ms. Jeynes-Ellis, Mr. Jordan, Mr. Wiinberg, and Mr. Wright are currently independent directors. Dr. Armen is currently not an independent director because he is employed as our Chief Executive Officer. In making independence determinations with regard to other directors, the Board considered transactions between us and a director or a director’s affiliates and any positions a director holds with entities with commercial relationships with us.

Executive Sessions of Independent DirectorsProposal

Our independent directors typically meet in executive session without management present immediately priorArticles of Incorporation currently authorizes us to regularly scheduled Board meetings and at least quarterly. Four such meetings were held during 2019.

Leadership Structureissue a maximum of the Board

Mr. Wright, an independent director, serves as the Lead Director400,000,000 shares of the Board and as Chair of the Corporate Governance and Nominating Committee. Mr. Wright also serves on the Compensation Committee, the Audit and Finance Committee and the Executive Committee. In additioncommon stock, par value $0.01 per share, subject to the duties of all directors, the specific responsibilities of the Lead Director include: (i) acting as chair of the Corporate Governance and Nominating Committee; (ii) developing the agenda for and presiding over all executive sessions of the independent directors; (iii) acting as principal liaison between the independent directors and the Chief Executive Officer on sensitive issues and raising at any meeting of the Board items that are not appropriately or best put forward by the Chief Executive Officer; and (iv) communicating to the Chief Executive Officer the independent directors’ annual evaluation of the Chief Executive Officer. The Company’s Chief Executive Officer serves as the Chairman of the

Board. We believe that the Company’s Chief Executive Officer is best situated to serve as Chairman because he is the director most familiar with the Company’s business, and most capable of effectively identifying strategic priorities and leading the discussion and execution of our Company’s strategy. Our independent directors and management have different perspectives and roles in strategy development. The Company’s independent directors bring experience, oversight, and expertise from outside the Company and from inside and outside the Company’s industry, while the Chief Executive Officer brings Company-specific experience and expertise. To assure effective independent oversight, the Company has adopted a number of governance practices, including:

While there may be circumstances in the future that would lead the Company to separate the offices of Chairman and Chief Executive Officer, we do not believe this is currently necessary due to the nature and size of the operations of the Company, the overall independence of the Board from management, and the strength of the Lead Director’s role on the Board.

Committees of the Board

The Board currently has four standing committees: the Audit and Finance Committee, the Compensation Committee, the Corporate Governance and Nominating Committee and the Executive Committee. The Board also appoints from time to time ad hoc committees to address specific matters.

Audit and Finance Committee

The Audit and Finance Committee consists entirely of independent directors within the meaning of the Nasdaq listing rules and the requirements contemplated by Rule10A-3 of the Securities Exchange Act of 1934, as amended (the “1934 Act”). Until December 24, 2019, the Audit and Finance Committee consisted of Mr. Corvese (Chair), Mr. Jordan and Mr. Wright. On December 24, 2019, Mr. Corvese stepped down as a member and Chair of the Audit and Finance Committee, and Mr. Wiinberg was appointed to replace Mr. Corvese in such roles. The Board determined that both Mr. Corvese and Mr. Wiinberg qualify as an audit committee financial expert. For a description of Mr. Wiinberg’s relevant experiences that qualify him as an audit committee financial expert, please see his biography on page 8. The Audit and Finance Committee’s primary function is to assist the Board in monitoring the integrity of our consolidated financial statements and our system of internal control. The Audit and Finance Committee has direct responsibility for the appointment, independence, and monitoring of the performance of our independent registered public accounting firm. The committee is responsible forpre-approving any engagements of our independent registered public accounting firm. The committee also reviews our risk management practices, strategic tax planning, preparation of quarterly and annual financial reports, and compliance processes.

The Audit and Finance Committee members meet regularly with our independent registered public accounting firm, without management present and with members of management in separate private sessions, to discuss any matters that the committee or these individuals believe should be discussed privately with the committee, including any significant issues or disagreements concerning our accounting practices or consolidated financial statements. The committee also reviews the Code of Ethics annually, and periodically meets with our

Chief Compliance Officer. The committee conducts a meeting each quarter to review our consolidated financial statements prior to the public release of earnings. The committee has the authority to engage special legal, accounting or other consultants to advise the committee. The committee also has the authority to delegate to subcommittees any responsibilities of the full committee. The Audit and Finance Committee charter is posted on the corporate governance section of our website athttp://investor.agenusbio.com/board-committees. No material on our website is partapproval of this proxy statement. Please also see the ReportProposal No. 1, and 5,000,000 shares of the Auditpreferred stock, $0.01 par value per share. Our issued and Finance Committee on page 46.

Compensation Committee

The Compensation Committee consists entirely of independent directors within the meaning of applicable Nasdaq listing rules. During the entirety of 2019, Mr. Jordan (Chair), Mr. Corvese and Mr. Wright were members of the Compensation Committee. The committee’s primary purpose is to approve, administer and interpret our executive, key employee and director compensation and benefit policies. The committee reviews, determines and approves the compensation of the Chief Executive Officer, all other executive officers and certain other key employees. It also reviews and recommends compensation for members of the Board. Additionally, the committee makes recommendations to the Board regarding the adoption of new incentive compensation and equity-based plans and administers existing incentive compensation and equity-based plans.

The Compensation Committee considers data from other companies for compensation comparison purposes and retained an outside compensation consultant in 2019, Radford, an Aon Hewitt Company—a division of Aon Corporation (“Radford”), to evaluate our executive and board compensation programs and to provide market reference information relating to executive and board compensation. The committee has the authority to retain legal, accounting, or other consultants to advise the committee. The committee also has the authority to delegate to subcommittees any responsibilities of the full committee. The Compensation Committee charter is posted on the corporate governance section of our website athttp://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement. Radford does not provide any services to the Company or the Compensation Committee other than those described above. After consideration of the six independence assessment factors provided under the listing rules of Nasdaq, the Compensation Committee determined that Radford, as an advisor to the Compensation Committee during 2019, was independent and that the work performed by Radford did not raise any conflicts of interest in 2019 that would preclude the Compensation Committee from reviewing and considering Radford’s analyses when making compensation decisions.

Corporate Governance and Nominating Committee

The Corporate Governance and Nominating Committee consists entirely of independent directors within the meaning of applicable Nasdaq listing rules. During 2019, the Corporate Governance and Nominating Committee consisted of Mr. Wright (Chair) and Mr. Wiinberg. Mr. Corvese joined the Corporate Governance and Nominating Committee on December 24, 2019. The Corporate Governance and Nominating Committee is responsible for recommending to the Board policies relating to the conduct of Board affairs, the process for annual evaluation of the Board and the Chief Executive Officer, issues of corporate public responsibility, and

overseeing the Company’s management succession planning process. It periodically evaluates the composition of the Board, the contributions of individual directors, and the Board’s effectiveness as a whole. The committee reviews the Company’s ethics and compliance activities under the Code of Ethics and meets periodically with our Chief Compliance Officer, including meeting, as needed, for separate private sessions with the Chief Compliance Officer without other members of management present.

The Corporate Governance and Nominating Committee recommends to our full Board individuals to serve as directors. The committee recommends to the Board guidelines and criteria for Board membership and reviews with the Board, on a periodic basis, the appropriate skills and characteristics required of Board members in the context of the then current needs of Agenus. The committee is responsible for reviewing with the Board the appropriate personal characteristics and professional competencies preferred of Board members, who are expected to work together as a team to properly oversee our strategies and operations. In general, all directors are expected to possess certain personal characteristics necessary to create a highly functional and collegial Board, which include personal and professional integrity, practical wisdom and mature judgment, an inquisitive and objective perspective, and time availability for performing the duties of a director.

The Board, as a group, is expected to encompass a range of talents, ages, skills, diversity, and expertise sufficient to provide sound and prudent guidance with respect to the operations and interests of our business. Examples of desired professional competencies include accounting and financial literacy, industry knowledge, medical or scientific knowledge, and management experience. When evaluating potential new Board appointments, the Corporate Governance and Nominating Committee considers these factors, but does not have any fixed criteria for candidates it recommends because the Board believes that a flexible evaluation process allows the committee to make sound judgments based on the needs of the organization and specific attributes of each candidate without a need for a formal policy on diversity. Candidates should also be enthusiastic about service on our Board and working collaboratively with existing Board members to create value for all of our stockholders.

The Corporate Governance and Nominating Committee does not have a formal policy with regard to the consideration of director candidates recommended by stockholders because it does not believe such a policy is necessary given that no unaffiliated stockholder has ever recommended a director candidate. When considering director candidates, the Corporate Governance and Nominating Committee, in consultation with the Chief Executive Officer and full Board, considers the current strengths on the existing Board, the current needs of the organization, and anticipated future activities and requirements of both the Board and the organization as a whole. Historically, director candidates have been generally identified primarily through referrals and the executive network pool of the Board and senior executives. If the committee were to receive a recommendation for a director candidate from a stockholder, the committee expects that it would evaluate such a candidate using the criteria described above. The committee will consider a recommendation only if appropriate biographical information and background material is provided on a timely basis, accompanied by a statement as to whether the stockholder or group of stockholders making the recommendation has beneficially owned more than 5% of our common stock for at least one yearoutstanding securities, as of the date that the recommendation is made. To submit a recommendation for a nomination, a stockholder may write to the Lead Director, Agenus Inc., 3 Forbes Road, Lexington, Massachusetts 02421, Attention: Lead Director c/o Chief Compliance Officer.

In addition, ourby-laws permit stockholders to nominate individuals, without any action or recommendation by the committee or the Board, for election as directors at an annual meeting of stockholders. For a description of thisby-law provision, see Additional Information on page 47 of this proxy statement. The charter of the Corporate Governance and Nominating Committee is posted on the corporate governance section of our website athttp://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement.

Communications with the Board

You may contact the Board or any committee of the Board by writing to Board of Directors (or specified committee), Agenus Inc., 3 Forbes Road, Lexington, Massachusetts 02421, Attn: Lead Director c/o Chief

Compliance Officer. You should indicate on your correspondence that youRecord Date are an Agenus stockholder. Communications will be distributed to the Lead Director, the appropriate committee chairman, or other members of the Board or executive management, as appropriate, depending on the facts and circumstances stated in the communication received. Executive management will generally determine the proper response to inquiries of a commercial nature, which generally will not be forwarded to the Lead Director. Inquiries regarding accounting, internal controls over financial reporting, or auditing matters will be forwarded to the Chair of the Audit and Finance Committee, and inquiries involving matters governed by the Code of Ethics will be forwarded to the Chair of the Corporate Governance and Nominating Committee and the Chief Compliance Officer.

Compensation Committee Interlocks and Insider Participation

The members of the Compensation Committee for the year ended December 31, 2019 were Mr. Jordan (Chair), Mr. Corvese, and Mr. Wright. No member of the Compensation Committee was at any time during 2019, or formerly, an officer or employee of Agenus or any subsidiary of Agenus. No executive officer of Agenus has served as a director or member of a compensation committee (or other committee serving an equivalent function) of any other entity while an executive officer of that other entity served as a director of Agenus or member of the Compensation Committee.

Our Executive Officers

Garo H. Armen, Ph. D.—Chairman and Chief Executive Officer—Dr. Armen has been our Chairman and Chief Executive Officer since our founding in 1994. From our founding until December 2019, Dr. Armen also served as our President, at which time he stepped down so that Dr. Buell could assume such role. Additional biographical information on Dr. Armen is set forth on page 8, above.

Jennifer S. Buell, Ph.D.—President and Chief Operating Officer—Dr. Buell, 45, has been our Chief Operating Officer since 2018 and became our President in December 2019. Dr. Buell has more than 20 years of biopharmaceutical R&D experience. From November 2013 to July 2016, Dr. Buell was the Company’s Vice President, Research and Development Operations and Program Management. From July 2016 to November 2017, she was the Company’s Vice President, Research and External Affairs, and from November 2017 to November 2018, she served as the Chief Communications and External Affairs Officer. Dr. Buell obtained her PhD in Cellular, Biochemical, and Molecular Biochemistry with an MS in Biostatistics from Tufts University.

Evan D. Kearns—Vice President and General Counsel—Mr. Kearns, 39, has been our Vice President, General Counsel, Corporate Secretary and Chief Compliance Officer since 2018. Mr. Kearns joined Agenus in 2014 as our Corporate Counsel and became our Associate General Counsel in 2015. Prior to Agenus, Mr. Kearns worked at the law firm Goodwin Procter LLP. Mr. Kearns holds a B.A. in Economics from Colby College and a J.D. degree from the University of Toledo College of Law.

Christine M. Klaskin—Vice President of Finance—Ms. Klaskin, 54, has been Vice President, Finance since October 2006. Since joining Agenus Inc. in 1996 as finance manager, Ms. Klaskin has held various positions within the finance department and has been involved in all equity and debt offerings of the Company including its IPO. From 2012 until 2017, Ms. Klaskin was a member of the board of directors of American DG Energy Inc until its sale to Tecogen Inc. Prior to joining Agenus, Ms. Klaskin was employed by Arthur Andersen as an audit manager. Ms. Klaskin received her Bachelor of Accountancy from The George Washington University.

Under our Bylaws, all of our executive officers are elected to their offices on an annual basis until the first meeting of our Board of Directors following our annual stockholder meeting. No family relationships exist among any of our directors or executive officers.

EXECUTIVE COMPENSATION

This section discusses the compensation of our executives who are named in the “Summary Compensation Table” below, who are referred to throughout this proxy statement as our “named executive officers”. Our named executive officers for 2019 are:

Compensation Philosophy and Competitive Market Review

Our Compensation Committee approves, administers and interprets our executive compensation program. Our executive compensation program is designed to attract and retain the highest caliber executive talent and reward and align the incentives we provide them with the creation of long-term stockholder value, while effectively managing the risks and challenges inherent to a biotechnology company of our size and stage of development. Our executive compensation program combines short- and long-term elements, cash and equity compensation, and fixed and variable compensation, in proportions that we believe appropriately incentivize our executives to achieve the following goals:

Our general philosophy is to emphasize equity over cash compensation and long-term over short-term compensation. Our Compensation Committee has concluded that our current compensation programs present no risks that are reasonably likely to have a material adverse effect on the Company. Our executive compensation program not only aims to be competitive in our industry, but also to be fair relative to other professionals within our organization.

In order to succeed in attracting highly-talented executives, we continuously monitor market trends and draw upon compensation surveys prepared by Radford, our Compensation Committee’s independent compensation consultant, custom research developed by Radford and Radford survey data, and other nationally-recognized compensation surveys. Our Compensation Committee reviews data that analyzes various cross-sections of our industry as well as relevant geographical areas. For 2019, we used two market references to evaluate our executive compensation program against those in the market:

On an annual basis, our compensation consultant recommends, and our Compensation Committee approves, a group of comparable companies as our peer group for executive and director compensation purposes. Our peer groups for 2018 and 2019 were as follows:

We compareThe approval of the amendment to the Articles of Incorporation to increase the authorized shares of common stock is important for the ongoing business of the Company. Without additional authorized shares of common stock, (i) the Company may not be able to raise additional financing which is needed to fund our executive compensation programongoing clinical and research programs, (ii) the amounts of compensation we pay against our peer group by reviewing each compensation element (measured at targetCompany may not be able to attract and retain key employees, officers and directors, and (iii) the Company may not be able to make possible strategic acquisitions, although no such acquisitions are currently contemplated.

The increase in the casenumber of annualauthorized shares of common stock may be available for our Board to issue in future financings, to provide equity incentive to employees, officers and long-term incentive opportunities).

The competitive posturedirectors, to make stock-based acquisitions and for other general corporate purposes, and we intend to use the additional shares of our actual annual compensation paidcommon stock that will be available to undertake any such issuances. We have no specific plan, commitment, arrangement, understanding or earned versus market references will vary yearagreement, either oral or written, regarding the issuance of common stock subsequent to year based on Companythis proposed increase in the number of authorized shares at this time, and individual performance, as well as the performance of our peer group and the respective levels of compensation paid by peer group companies to their executives.

Executive Compensation Program

Components of our Executive Compensation Program

Our executive compensation program consistswe have not allocated any specific portion of the following four components:

Short-Term Compensation.

Base Salary: Base salaries provide a fixed level of compensation. Base salaries for our executive officers are generally positioned at or aroundproposed increase in the 50^th percentile of the market. In establishing the base salary of each of our executive officers, our Compensation Committee (with input from our Chief Executive Officer, other than with respect to his own base salary) takes into account aauthorized number of factors, including such person’s seniority,shares to any particular purpose. The Company is therefore requesting its stockholders approve this proposal to amend its Articles of Incorporation to increase the authorized shares of common stock.

towards potential commercialization. The annual bonuses paid with respect to 2019 are listed in the “Bonus” column of the Summary Compensation Table below.

In December 2019, in connection with her promotion to President and Chief Operating Officer of the Company, Dr. Buell’s target bonus was increased from 40% to 45% of her base salary.

Long-Term Incentives.

Our long-term incentives generally consist of time-vesting and performance-vesting stock options, restricted stock awards and performance shares. During 2019, time-vesting stock options, performance-vesting stock options and performance shares (performance-vesting restricted stock units) were granted to our executive officers. Performance shares and performance-vesting options reward performance and the achievement of key milestones or other performance goals that are important to our success. We believe that time-vesting stock options are also performance-based because no valueBoard determines is created unless the value of our common stock appreciates after grant. More generally, equity-based awards support an ownership culture that align the interests with our executive officers and our stockholders and thereby encourage our executive officers to take actions that arenot in the best interests of the Company’s long-term success. Our Compensation Committee grants equity-based awards to our executives and employees generally to enable them to participateCompany or its stockholders. The proposed increase in authorized shares of common stock therefore may have the long-term appreciationeffect of our stock, as well as to share the impactdiscouraging unsolicited takeover attempts. By potentially discouraging initiation of any business and market setbacks.

Our Compensation Committee takes into considerationsuch unsolicited takeover attempts, the proposed increase in authorized shares of common stock may limit the opportunity for the Company’s stockholders to dispose of their shares at the higher price generally available in takeover attempts or that may be available under a numbermerger proposal. The proposed increase in authorized shares of factors in determiningcommon stock may have the long-term incentive awards granted to our executive officers,effect of permitting the Company’s current management, including the considerations described above under “Base Salary”current Board, to retain its position, and “Annual Incentive Bonuses,” as well as our annual burn rate and overhang,place it in a better position to resist changes that stockholders may wish to make if they are dissatisfied with the number of shares available under our 2019 Equity Incentive Plan, the value of each grant (both the grant date fair value for accounting purposes and the face value (number of shares multiplied by the grant date stock price)), the number of shares granted, and the executives’ equity holdings. Beginning in December 2019, our Compensation Committee changed the timing of granting our annual long-term incentive awards from January to December. As a result, our employees, including our executive officers, received long-term incentive awards in January 2019 and December 2019 that were intended to cover two separate years.

On January 1, 2019 as part of a Company-wide award, each of our executive officers received a grant of time-vesting stock options, with an exercise price equal to the closing price of our common stock on the date of grant, subject to approval of an increase to the available share pool under our equity incentive plan at the 2019 Annual Stockholder Meeting. The options granted to our executive officers in January 2019 vest as toone-thirdconduct of the options on the first anniversaryCompany’s business. The Board is not aware of the grant date and thereafter in quarterly installments, generally subjectany attempt, or contemplated attempt, to the executive’s continued employment or service with the Company. In reviewing the size of Dr. Armen’s annual grant, our Compensation Committee discussed the important need to retain and incentivize Dr. Armen through a critical period for the Company as it approached two planned BLA filings and was on the verge of transitioning into a commercial company. On this same date, Dr. Armen was also granted performance shares that were eligible to vest over time through January 2022 based upon the achievement of certain aggressive milestones on or before March 31, 2020, all subject to approval of an increase to the available share pool under our equity incentive plan at the 2019 Annual Stockholder Meeting. On March 31, 2020, the milestone thresholds were not achieved and these performance shares were forfeited in their entirety.

On July 23, 2019 our Compensation Committee granted performance-vesting stock options to all our executive officers and certain senior Company employees, which are eligible to vest, if at all, on June 30, 2022 (or an earlier change of control), based upon the performance of our common stock prior to such date and the recipient’s continued employment or service with the Company through the vesting date. Our Compensation Committee chose share price hurdles that it believed to be key drivers of our business that will help create long-term value for our stockholders.

On December 24, 2019, as part of a Company-wide award, each of our executive officers received a grant of time-vesting stock options, with an exercise price equal to the closing price of our common stock on the date of grant. The options granted to our executive officers in December 2019 vest as toone-third of the options on the first anniversary of the grant date and thereafter in quarterly installments, generally subject to the executive’s continued employment or service with the Company.

Benefits and Perquisites.

We provide the following benefits to our executive officers generally on the same basis as the benefits provided to all of our employees:

We believe that these benefits are consistent with those offered by companies against which we compete for talent.

We also provide personal benefits and perquisites to our executive officers from time to time. In 2019, our Compensation Committee approved a $150,000 per year allowance for Dr. Armen for personal travel. Dr. Armen did not use any portion of this allowance in 2019.

Severance Compensation and Termination Protection.

We have entered into employment agreements with Drs. Armen and Buell. These agreements provide for severance payments and benefits if the executive’s employment is terminated under certain conditions, such as in connection with a change ofacquire control of the Company, nor is this proposal being presented with the intent that it be used to prevent or discourage any acquisition attempt. However, nothing would prevent the Board from taking any such actions that it deems to be consistent with its fiduciary duties.

Vote Required and Board Recommendation

Approval of an amendment to our Articles of Incorporation to increase our authorized shares of common stock from 400,000,000 to 800,000,000 requires the affirmative vote of the majority of the voting power of the common stock issued and outstanding as of the Record Date, and abstentions will have the effect of a termination without cause by us, as described in further detail under “Potential Payments Upon Termination or Changevote against this proposal.

The Board unanimously recommends a vote “FOR” the approval of Control” below.an amendment to our Articles of Incorporation to increase our authorized shares of common stock from 400,000,000 to 800,000,000

Employment Agreements

We entered into an employment agreement with Dr. Armen in 2005 and subsequently amended the agreement in 2009 and 2010. Dr. Armen’s employment agreement sets forth his initial base salary and target annual bonus opportunity, both of which have subsequently increased, and provides for severance payments and benefits in the event of a qualifying termination of his employment, as described under “Potential Payments Upon Termination or Change in Control” below. Dr. Armen’s employment agreement includes restrictive covenants with respect to confidential information and the assignment of intellectual property, and includesnon-competition and employeenon-solicitation/no-hire covenants that apply for the greater of 18 months following his termination of employment or the period during which Dr. Armen receives severance payments and benefits.

We entered into an employment agreement with Dr. Buell in 2019. Dr. Buell’s employment agreement sets forth her then current base salary and then current target annual bonus opportunity, both of which have subsequently increased, and provides for severance payments and benefits in the event of a qualifying termination of her employment, as described under “Potential Payments Upon Termination or Change in Control” below. Dr. Buell’s employment agreement includes restrictive covenants with respect to confidential information and the assignment of intellectual property, and includesnon-competition and employeenon-solicitation/no-hire covenants that apply for the greater of 12 months following her termination of employment or the period during which Dr. Buell receives severance payments and benefits.

We have not entered into an employment agreement with Mr. Kearns.

Retirement Benefits

We maintain a 401(k) retirement plan in which our eligible U.S. employees, including Drs. Armen and Buell and Mr. Kearns, are able to participate and provide employer matching contributions under such plan equal to $0.50 for each $1.00 contributed by an employee. Our employer matching contribution is capped at 3% of an employee’s overall compensation.

In June 2019, the Compensation Committee of our Board of Directors amended the terms of the outstanding stock options held by Dr. Armen. Pursuant to the amendment, in the event of Dr. Armen’s death, disability or retirement, all of his unvested stock options will vest in full and become exercisable, and each stock option will remain exercisable for the lesser or (i) three years from the date of such event or (ii) the end of the10-year term of each such stock option.

Potential Payments Upon Termination or Change of Control

Our employment agreements with Drs. Armen and Buell that provide for certain payments and benefits in the event of certain terminations of employment or a change of control. Mr. Kearns is not entitled to any

payments or benefits in connection with any termination of his employment or a change of control. The following text and tables summarize the potential payments to Drs. Armen and Buell assuming that the triggering event occurred on December 31, 2019, the last day of our fiscal year. As used in the following summary, the terms “cause,” “good reason” and “change of control” have the meaning set forth in the applicable agreement.

Our Chief Executive Officer

Under Dr. Armen’s employment agreement, if we terminate Dr. Armen’s employment without cause or if he terminates his employment for good reason, he is entitled to receive from the Company:

Upon a change of control, 100% of any of Dr. Armen’s outstanding unvested performance shares immediately vest and 50% of any of Dr. Armen’s outstanding unvested stock options and restricted stock as of the change of control date become vested and exercisable and, in the case of shares of restricted stock, no longer subject to forfeiture. If a change of control occurs and, within 24 months, we terminate Dr. Armen’s employment without cause or if he terminates his employment for good reason, he is entitled to receive from the Company:

Additionally, under Dr. Armen’s employment agreement, he is subject to post-terminationnon-competition andnon-solicitation restrictions that apply for the greater of a period of 18 months post-termination or the period during which he is receiving post-termination payments from us.

Our President and Chief Operating Officer

Under Dr. Buell’s employment agreement, if we terminate Dr. Buell’s employment without cause or if she terminates her employment based on a material reduction in her base salary, she is entitled to receive from the Company:

Upon a change of control, 50% of any of Dr. Buell’s outstanding unvested performance shares immediately vest and 50% of any of Dr. Buell’s outstanding unvested stock options and restricted stock as of the change of control date become vested and exercisable and, in the case of shares of restricted stock, no longer subject to forfeiture. If a change of control occurs and, within 18 months, we terminate Dr. Buell’s employment without cause or if she terminates her employment as a result of a material reduction in her base salary or for good reason, she is entitled to receive from the Company:

Additionally, under Dr. Buell’s employment agreement, she is subject to a12-month post-termination of employmentnon-competition covenant in the event her employment terminates under certain circumstances andnon-solicitation restrictions that apply for the greater of a period of 12 months post-termination or the period during which she is receiving post-termination payments from us. In the event any payment or benefit provided to Dr. Buell, under her employment agreement or otherwise, would be subject to the excise tax imposed by Section 4999 of the Code, the payments and benefits will be automatically reduced to the extent necessary so that such excise tax will not be applicable.

DIRECTOR COMPENSATION

The following table shows the compensation paid or awarded to eachnon-employee director for his or her service as anon-employee director in 2019:

Cash and Equity Compensation forNon-Employee Directors for 2019

The Board has adopted a policy guideline that encourages directors to hold 10,000 shares of our common stock within a reasonable period of time following their election or appointment to the Board. In addition to purchasing shares in the open market, directors may utilize the DDCP or the Agenus Board Compensation Policy, which allows directors to receive their compensation in stock, to acquire these shares. In accordance with the requirements of the DDCP, elections to defer compensation thereunder must be made prior to the end of the third quarter of the prior calendar year. In some cases, a director, due to securities law restrictions, may be unable to purchase such shares until such election takes effect.

OWNERSHIP OF OUR COMMON STOCK

Ownership By Management

On April 24, 2020, Agenus had 167,384,037 shares of common stock issued and outstanding. The table below shows certain information about theregarding beneficial ownership of Agenusour common stock as of April 24, 2020, by:11, 2022:

In accordance with SEC rules, we have included in the column “Number of Issued Shares” all shares of common stock over which the person has sole or shared voting or investment power as of April 24, 2020, and we have included in the column “Number of Shares Issuable” all shares of common stock that the person has the right to acquire within 60 days after April 24, 2020 through the exercise of any stock options, the vesting of restricted shares, or in the case of directors, any shares to be distributed under the DDCP. All shares that a person has a right to acquire within 60 days of April 24, 2020 are deemed outstanding for the purpose of computing the percentage beneficially owned by the person, but are not deemed outstanding for the purpose of computing the percentage beneficially owned by any other person.

Unless otherwise indicated in the footnotes to the following table, each person has the sole power (or shares the power with a spouse) to invest and vote the shares of common stock listed opposite the person’s name. Where applicable, ownership is subject to community property laws. Our inclusion of shares in this table as beneficially owned is not an admission of beneficial ownership of those shares by the person listednamed in the table. Except as noted, thetable has sole voting and investment power and that person’s address of each stockholder is c/o Agenus Inc., 3 Forbes Road, Lexington, Massachusetts 02421.

DELINQUENT SECTION 16(a) REPORTS

Our executive officers, directors, and 10% stockholders are required under Section 16(a) of the 1934 Act, to file reports of ownership and changes in ownership of our securities with the SEC.

Based solely on a review of the copies of reports furnished to us, we believe that during our 2019 fiscal year, our directors, executive officers, and 10% stockholders complied with all applicable Section 16(a) filing requirements, with the following exceptions: Dr. Armen inadvertently filed 2 delinquent Section 16(a) report with respect to 4 transactions relating to a stock option grant, a donation to a charitable organization, a required distribution and a required deposit into a trust all of which occurred in 2018.

CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

Related Party Transactions

Children of Armenia Fund

Our Audit and Finance Committee approved a charitable contribution to the Children of Armenia Fund (“COAF”) totaling $125,000 for 2019. Dr. Garo H. Armen, Agenus’ Chairman and Chief Executive Officer, is the founder and chairman of COAF. The 2019 charitable contribution was comprised of a cash component and anon-cash component. The cash component was $75,000, which Agenus paid in quarterly installments. Thenon-cash component was $50,000, which was the estimated value of a portion of Agenus’ office space in its New York office that was (and continues to be) made available to COAF employees.

Related Party Transaction Policies and Procedures

The Audit and Finance Committee of the Board is responsible for reviewing and approving all material transactions with any related party on a continuing basis. Related parties can include any of our directors or executive officers, certain of our stockholders, and their immediate family members. This obligation is set forth in writing in our Audit and Finance Committee Charter. A copy of the Audit and Finance Committee Charter is posted on the corporate governance section of our website athttp://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement. In evaluating related party transactions, our Audit and Finance Committee members apply the same standards of good faith and fiduciary duty they apply to their general responsibilities as a committee of the Board and as individual directors. The Audit and Finance Committee will approve a related party transaction when, in its good faith judgment, the transaction is fair to, and in the best interest of, Agenus.

To identify related party transactions each year, we submit and require our directors and executive officers to complete Director and Officer Questionnaires identifying any transactions with us in which the officer or director or their family members have an interest. We also review related party transactions due to the potential for a conflict of interest. A conflict of interest occurs when an individual’s private interest interferes, or appears to interfere, in any way with our interests. Our Code of Ethics requires all directors, officers, and employees who may have a potential or apparent conflict of interest to immediately notify our Chief Compliance Officer for review and approval by management and our Corporate Governance and Nominating Committee. A copy of our Code of Ethics is posted on the corporate governance section of our website at http://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement.

PROPOSAL 2—TO APPROVE AN AMENDMENT TO OUR AMENDED AND RESTATED DIRECTORS’ DEFERRED COMPENSATION PLAN TO INCREASE THE NUMBERPROPOSALS OF SHARES OF COMMON STOCK AUTHORIZED FOR ISSUANCE THEREUNDER FROM

425,000 TO 575,000

Description of Proposed Amendment to our Amended and Restated Directors’ Deferred Compensation Plan

Our Amended and Restated Directors’ Deferred Compensation Plan (the DDCP) was originally adopted in 2007 and has subsequently been amended and restated, most recently in 2018. On April 23, 2020, our Board adopted, subject to stockholder approval, an amendment to the DDCP to increase the number of shares of our common stock available for issuance thereunder from 425,000 shares to 575,000 shares. We are requesting that stockholders approve this amendment to the DDCP. We are not requesting approval of any other changes to the DDCP.

If stockholders do not approve this Proposal 2, the proposed 150,000 additional shares will not become available for issuance under the DDCP, but the DDCP will otherwise remain in effect in accordance with its terms.

Background and Reasons to Vote for this Proposal

The DDCP permits members of our Board who are not officers or employees of the Company or its subsidiaries to elect to defer the receipt of all or a portion of the cash compensation payable in respect of services as a director until a later date, with the amount deferred payable in cash and/or shares of our common stock, as elected by the applicable director. We believe that that the DDCP is an important component of our director compensation program and is beneficial to our stockholders because it allows us to preserve our current cash resources, with respect to those directors who elect to defer compensation, and further aligns the interests of ournon-employee directors with those of our stockholders.

As of March 31, 2020, there were 352,919 shares reserved for issuance under the DDCP and we no longer have any shares available for reservation. We are requesting that stockholders approve this Proposal 2 because the shares remaining available for issuance under the DDCP are not sufficient to allow us to continue to offer ournon-employee directors the opportunity to receive shares of our common stock in respect of compensation that they elect to defer.

Summary of the DDCP

The following is a brief summary of the material terms of the DDCP, as amended to increase the number of shares of our common stock available for issuance thereunder. A copy of the amendment to our DDCP is attached as Appendix A to this proxy statement, and we urge stockholders to read it in its entirety. The following description of certain features of the DDCP is qualified in its entirety by reference to the full text of the DDCP.

Administration. The DDCP is administered by the Chief Financial Officer of the Company or another officer designated by our Board, who will have the sole responsibility for interpreting the DDCP. The DDCP is currently administered by the Company’s Vice President, Finance.

Eligibility. Each member of our Board who is not also an officer or an employee of the Company or its subsidiaries is eligible to participate in the DDCP. All of our current directors, except Dr. Armen, are eligible to participate in the DDCP. As of April 24, 2020, fivenon-employee directors are eligible to participate in the DDCP.

Basis of Participation. The DDCP allows each eligible director to defer receipt of all or a portion of the cash compensation payable to him or her for service on our Board. Such compensation may be deferred until termination of service as a director or, subject to the terms of the DDCP, such other date as may be specified by the director.

A director may elect to participate in the DDCP no later than September 30 of the year before the calendar year in which the applicable compensation would be earned and may choose to defer 25, 50, 75 or 100 percent of his or her total cash compensation payable for services as a director. A deferral election remains in effect unless the participant files a written revocation or superseding deferral agreement and a deferral election becomes irrevocable after the last day of the calendar year immediately preceding the year to which the deferral relates. A notional deferral account is established for each participating director, which consists of a notional subaccount for amounts earning interest, denominated on a dollar basis (the “cash account”), and a notional subaccount for amounts invested in hypothetical shares of our common stock, which is denominated on a notional share basis (the “stock account”). Pursuant to the deferral agreement, each participant indicates the percentage of future deferrals to be notionally invested in the cash account and the stock account. Amounts are credited to these accounts on a quarterly basis.

Amounts deferred to the cash account are credited with interest at the rate paid onone-year Treasury bills. Amounts deferred to the stock account are converted on a quarterly basis into a number of units representing shares of our common stock equal to the amount of compensation which the participant has elected to defer to the stock account divided by the applicable stock price for our common stock (determined based on the average closing price of our common stock for all trading days during the applicable calendar quarter). Prior to receiving a distribution from the stock account, units representing shares allocated to a participant’s stock account are not considered actual shares of our common stock for any purpose, and a participant will have no right as a stockholder with respect to such units. A participant with amounts held in the stock account will be eligible for cash and stock dividends in the form of units on the date we pay any such dividends on shares of our common stock. In the event of a stock dividend, recapitalization, reorganization, merger, consolidation,split-up,spin-off, exchange of shares or similar change affecting common stock, appropriate adjustments will be made in the number and/or kind of units representing shares credited to the stock account.

Authorized Shares; Adjustments. Without giving effect to the proposed amendment, the aggregate number of shares of our common stock that are reserved for issuance under the DDCP is 425,000. In the event of a stock dividend,split-up, combination or reclassification of shares, recapitalization or similar capital change, the aggregate number of shares that are reserved for issuance under the DDCP will be appropriately adjusted by our Board. The closing price of our common stock as reported on NASDAQ on April 24, 2020 was $2.79 per share.

Distributions. Distributions from notional accounts under the DDCP will be paid in a lump sum or in annual installments for a period of up to five years and commence in the calendar year following a participant’s termination of service as a director or such other calendar year as may be specified by the participant, provided such other calendar year is at least two years after the date the director elected to receive such distribution. Distributions consist of (a) cash in the amount credited to the participant’s notional account and (b) the number of shares of our common stock equal to the number of units credited to his or her stock account. To the extent a participant would receive a payment from his or her stock account in excess of the number of shares remaining available under the DDCP, the participant shall receive cash in lieu of shares.

Unfunded Plan. The DDCP is unfunded, and the Company has no obligation to set aside, segregate, or deposit any funds or assets of any kind to meet its obligations under the plan. The rights of any participant, beneficiary, or other person under the DDCP will be solely those of a general unsecured creditor of our Company.

Amendment and Termination. The Company may, without the consent of any participant, beneficiary, or other person amend the DDCP at any time, but no amendment may reduce the amount previously credited to a participant’s deferral account. The Company may terminate the DDCP at any time, and the Company may, in its discretion, distribute amounts according to the participant’s deferral election or in a lump sum as soon as practicable after the plan’s termination date.

New Plan Benefits

Participation in the DCPP is entirely within the discretion of the eligible directors. Because we cannot presently determine the rate of contributions by these directors, it is not possible to determine the value of benefits that may be obtained by participants under the DCPP.

The following table sets forth the amounts deferred by ournon-employee directors as a group under the DCPP for the fiscal year ended December 31, 2019. None of our executive officers or other employees are eligible to participate in the DCPP.

PROPOSAL 3—TO APPROVE OUR 2019 EMPLOYEE STOCK PURCHASE PLAN.

Our 2009 Employee Stock Purchase Plan was originally approved by our stockholders on June 10, 2009 and expired on June 10, 2019. Effective June 30 2019, our Board adopted our 2019 Employee Stock Purchase Plan (our “ESPP”). We are requesting that stockholders approve our ESPP. The material terms of our ESPP are described under “Summary of our ESPP” below.

Following the approval by our Board, we commenced our first option period under our ESPP, which ended on December 31, 2019, and commenced another option period under our ESPP on January 1, 2019, which is scheduled to end on June 30, 2020. 236,855 shares of our common stock were delivered in satisfaction of options granted in the first option period under our ESPP in January 2020. As of March 31, 2020, there were 263,145 shares remaining available for issuance under our ESPP.

If stockholders do not approve this Proposal 3, all options granted under our ESPP will be cancelled and will become null and void and any shares previously delivered under the ESPP will be required to be returned to the Company.

As of March 31, 2020, 36,031,332 shares of our common stock were available for future issuance or subject to outstanding awards under our 2009 Equity Incentive Plan, our 2019 Equity Incentive Plan, our 2015 Inducement Equity Plan, our DDCP and our ESPP, which represents 22% of our common stock outstanding on such date, and an additional 650,000 shares, representing 0.4% of our common stock outstanding as of March 31, 2020, are proposed to be made available for issuance under our DDCP and our ESPP pursuant to Proposal 2 and this Proposal 3.

Summary of our ESPP

The following is a brief summary of the material terms of our ESPP. A copy of our ESPP is attached as Appendix B to this proxy statement, and we urge stockholders to read it in its entirety. The following description of the material terms of our ESPP is qualified in its entirety by reference to the full text of our ESPP.

In General.Our ESPP is intended to enable eligible employees to purchase shares of our common stock and thereby acquire an interest in the future of the Company. Our ESPP is generally implemented by a series of separate offerings, which we refer to as option periods. On the first day of each option period, participating employees will be granted an option to purchase shares of our common stock, which will be automatically exercised on the last business day of the option period. Our ESPP is intended to satisfy the requirements of Section 423 of the Code.

Administration.Our ESPP is administered by the Board and its delegates, which will have the right to determine any questions that may arise regarding the interpretation and application of our ESPP and to make, administer and interpret such rules and regulations as it deems necessary or advisable. The Board may delegate any or all of its powers under our ESPP to one or more committees or subcommittees to the extent permitted by applicable law and has so delegated its powers to our Compensation Committee. As used in this summary, the term “Board” refers to the Board or any authorized delegates, as applicable.

Eligibility.Participation in our ESPP is limited to our employees and those of our designated subsidiaries. No employee will be granted an option under our ESPP if, immediately after the option is granted, the employee would own (or would be deemed to own) shares of our common stock possessing five percent or more of the total combined voting power or value of all classes of shares of us, our parent or our subsidiaries. In addition, no employee will be granted an option under our ESPP that would permit his or her rights to purchase shares under all employee stock purchase plans maintained by us and our parent and subsidiaries to accrue at a rate that exceeds $25,000 (or such other maximum prescribed by the Code) of fair market value of stock for each calendar year during which any option granted to such employee is outstanding at any time, determined in accordance with Section 423(b)(8) of the Code. As of April 24, 2020 approximately 250 employees are eligible to participate in our ESPP, including all of our executive officers.

Authorized Shares.Subject to adjustment as described below, 500,000 shares of our common stock are reserved for issuance under our ESPP (263,145 of which shares remained available for issuance as of March 31, 2020). If any option granted under our ESPP expires or terminates for any reason without having been exercised in full or ceases for any reason to be exercisable in whole or in part, the unpurchased shares subject to such option will again be available for sale pursuant to the exercise of options under our ESPP. The closing price of our common stock as reported on NASDAQ on April 24, 2020 was $2.79 per share.

Shares that may be issued under our ESPP may be authorized but unissued shares or reacquired shares.

Participation.Eligible employees may elect to participate in an option period under our ESPP in the manner and within the time periods established by the Board. A participant who holds an option under our ESPP may at any time prior to exercise cancel all (but not less than all) of his or her option by written notice to the Company. Upon cancellation, the balance of the participant’s account under our ESPP will be returned to the participant.

Option Periods.Unless otherwise determined by the Board, option periods under our ESPP will be approximately six months in duration and commence on the first business day of January and July of each year and end on the last business day of June and December of each year, respectively.

Options.Subject to the limitations in our ESPP, on the first day of each option period, participating employees will be granted an option to purchase no more than 20,000 shares of our common stock. On the last day of each option period, each employee who is a participant in our ESPP will be deemed to have exercised the option granted to him or her for the option period.

Purchase Price.The purchase price of each share issued pursuant to the exercise of an option under our ESPP on an exercise date will be 85% of the lesser of (i) the fair market value of a share on the date the option is granted and (ii) the fair market value of a share on the exercise date.

Transfer Restrictions. Options granted under our ESPP during the participant’s lifetime will be exercisable only by such participant and may not be sold, pledged, assigned or transferred in any manner.

Adjustments.In the event of any change in the outstanding stock of the Company by reason of a stock dividend,split-up, recapitalization, merger, consolidation, reorganization, or other capital change, the aggregate number and type of shares available under our ESPP, the number and type of shares under options granted but not exercised, the maximum number and type of shares purchasable under an option, and the option price will be appropriately adjusted; provided that no adjustment will be made unless the Company is satisfied that it will not constitute a modification of rights granted under our ESPP or otherwise disqualify our ESPP as an employee stock purchase plan under Section 423 of the Code.

Certain Transactions. In the event of a sale of all or substantially all of our stock or assets, or a merger or similar transaction in which the Company does not survive or which results in the acquisition of the Company by another person, the Board will (i) if the Company is merged with or acquired by another corporation, provide that each outstanding option will be assumed or that a substitute option will be granted by the acquirer, the successor or one of their parents or subsidiaries, (ii) cancel each option and return the balances in participants’ accounts under our ESPP to participants, or (iii) end the option period on or before the date of the proposed sale or merger.

Term.Our ESPP, became effective on June 30, 2019, the date it was approved by the board, subject to stockholder approval within 12 months following such date of approval, and no rights shall be granted thereunder after the tenth anniversary of such date of board approval.

Amendment and Termination.The Board may at any time amend our ESPP to the extent, and in any manner, it may deem advisable, subject to stockholder approval if the amendment would be treated as the adoption of a new plan for purposes of Section 423 of the Code. The Board may suspend or terminate our ESPP at any time. In connection with any such suspension or termination, the Board may provide that outstanding options will be exercisable either at the end of the applicable option period or such earlier date as the Board may specify.

Certain Federal Income Tax Consequences of our ESPP

The following is a summary of certain U.S. federal income tax consequences associated with options granted under our ESPP. This summary does not purport to cover federal employment tax or other U.S. federal tax consequences that may be associated with our ESPP, nor does it cover state, local ornon-U.S. taxes.

Our ESPP is intended to qualify under the provisions of Section 423 of the Code. Our ESPP is not subject to any provisions of the Employee Retirement Income Security Act of 1974.

Assuming our ESPP is and remains so qualified, no income will be taxable to a participant until the sale or other disposition of the shares of common stock purchased under our ESPP (the “ESPP shares”). Upon such sale or disposition, the participant will generally be subject to tax in an amount that depends upon the participant’s holding period with respect to the ESPP shares. If the ESPP shares are sold or disposed of more than two years from the first day of the applicable option period and more than one year from the date of purchase, or upon the participant’s death while owning the ESPP shares, the participant will recognize ordinary income measured as the lesser of (1) the excess of the fair market value of the ESPP shares at the time of such sale or disposition over the purchase price or (2) an amount equal to the excess of the fair market value of the ESPP shares as of the first day of the option period over the purchase price. Any additional gain will be treated as long-term capital gain. If the ESPP shares held for the periods described above are sold and the sale price is less than the purchase price, there is no ordinary income and the participant generally will have long-term capital loss equal to the difference between the sale price and the purchase price. If shares are sold or otherwise disposed of before the expiration of the holding periods described above, other than following the participant’s death while owning the shares, the participant will recognize ordinary income generally measured as the excess of the fair market value of the ESPP shares on the date the ESPP shares were purchased over the purchase price. Any additional gain or loss on such sale or disposition will generally be long-term or short-term capital gain or loss, depending on the participant’s holding period with respect to the ESPP shares. The Company is not generally entitled to a deduction for amounts taxed as ordinary income or capital gain to a participant except generally to the extent of ordinary income recognized upon a sale or disposition of shares prior to the expiration of the holding periods described above.

New Plan Benefits

The amounts of future stock purchases under our ESPP are not determinable because, under the terms of our ESPP, purchases are based upon elections made by participants. Future purchase prices are not determinable because they are based upon fair market value of shares of our common stock at the beginning and end of each applicable option period.

The following table sets forth the number of shares under our ESPP that were acquired by our named executive officers, our executive officers as a group and our other employees (who are not executive officers) as a group for the option period ending on December 31, 2019, in each case, subject to stockholder approval.Non-employee directors are not eligible to participate in our ESPP.

Vote Required

To approve Proposal 3, a majority of the votes cast by stockholders present in person or by proxy and voting on the matter must vote FOR Proposal 3. If your shares are held by your broker, bank, or nominee in “street name,” and you do not vote your shares, your broker, bank, or nominee has authority to vote your unvoted shares on Proposal 3. If the broker, bank, or nominee does not vote your unvoted shares, there will be no effect on the vote because these “brokernon-votes” are not considered to be voting on the matter. Abstentions and “brokernon-votes” will not be counted as votes cast or shares voting on Proposal 3, and will have no effect on the vote.

The Board of Directors recommends a vote FOR Proposal 3.

EQUITY PLANS

Securities Authorized For Issuance Under Equity Compensation Plans

The following table provides information about the securities authorized for issuance under our equity compensation plans as of December 31, 2019. The following table does not include any shares available under the ESPP or that would become available following approval of the amendment to our DDCP.

PROPOSAL 4—TO RATIFY THE APPOINTMENT OF KPMG LLP AS OUR INDEPENDENT

REGISTERED PUBLIC ACCOUNTING FIRMSTOCKHOLDERS FOR THE FISCAL YEAR ENDING

DECEMBER 31, 2020

Our Audit and Finance Committee has selected KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2020. Although stockholder approval of the selection of KPMG LLP is not required by law, our Board believes that it is advisable to give stockholders an opportunity to ratify this selection.

If stockholders do not approve this proposal at the 2020 Annual Meeting, our Audit and Finance Committee will reconsider their selection of KPMG LLP. If stockholders do ratify this appointment, the Audit and Finance Committee, which has direct authority to engage our independent registered public accounting firm, may appoint a different independent registered public accounting firm at any time during the year if the Audit and Finance Committee determines that the change would be in the best interests of Agenus and our stockholders.

The Audit and Finance Committee has approved all services provided to Agenus by KPMG LLP during 2019. Representatives of KPMG LLP are expected to be present at the 2020 Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will also be available to respond to appropriate questions from stockholders.

KPMG LLP has served as our independent registered public accounting firm since 1997.

Audit Fees

Fees incurred by us for professional services rendered by KPMG LLP for the audit of the annual consolidated financial statements and of the effective operation of internal control over financial reporting, included in our Annual Report on Form10-K, for the reviews of the consolidated financial statements included in our Forms10-Q and for comfort letters, consents and review of registration statements were $908,690 for 2019 and $886,870 for 2018.

Audit-Related Fees

Fees paid to KPMG LLP for the audit of our 401(k) Retirement Plan were $30,750 in 2018. KPMG did not audit our 401(k) Retirement Plan in 2019.

Tax Fees

Fees paid to KPMG LLP associated with tax compliance services were $101,447 in 2019 and $111,681 in 2018.

Fees paid to KPMG LLP associated with tax consultation services were $165,986 in 2019 and $61,962 in 2018.

All Other Fees

We paid no other fees to KPMG LLP for 2019 or 2018.

Pre-Approval of Audit andNon-Audit Services

All of the KPMG LLP fees for 2019 and 2018 shown above werepre-approved by the Audit and Finance Committee. The Audit and Finance Committeepre-approves all audit and other permittednon-audit services provided by our independent registered public accounting firm.Pre-approval is generally provided for up to one year, is detailed as to the particular category of services and is subject to a monetary limit. Our independent

registered public accounting firm and senior management periodically report to the Audit and Finance Committee the extent of services provided by the independent registered public accounting firm in accordance with thepre-approval, and the fees for the services performed to date. The Audit and Finance Committee may alsopre-approve particular services on acase-by-case basis.

Vote Required

To approve Proposal 4, a majority of the votes cast by stockholders present in person or by proxy and voting on the matter must vote FOR Proposal 4. If your shares are held by your broker, bank, or nominee in “street name,” and you do not vote your shares, your broker, bank, or nominee has authority to vote your unvoted shares on Proposal 4. If the broker, bank, or nominee does not vote your unvoted shares, there will be no effect on the vote because these “brokernon-votes” are not considered to be voting on the matter. Abstentions and “brokernon-votes” will not be counted as votes cast or shares voting on Proposal 4, and will have no effect on the vote.

The Board of Directors recommends a vote FOR Proposal 4.

PROPOSAL 5—TO APPROVE, IN ANON-BINDING ADVISORY VOTE,

THE COMPENSATION OF THE COMPANY’S NAMED EXECUTIVE OFFICERS

The Company is providing stockholders with the opportunity at the 2020 Annual Meeting to vote on the following advisory resolution, commonly known as“Say-on-Pay”:

RESOLVED, that the stockholders of the Company approve, in anon-binding, advisory vote, the compensation of the Company’s named executive officers as disclosed in the Company’s proxy statement under the headings “Executive Compensation” and “Compensation of Executive Officers.”

As described above in the Executive Compensation section of this proxy statement, the Compensation Committee has structured our executive compensation program to provide an overall compensation package that enables us to attract and retain talented employees, provide incentives for performance and create long-term value for our stockholders. The Company’s executive compensation programs have a number of features designed to promote these objectives.

The Board urges stockholders to read the Executive Compensation section beginning on page 17 of this proxy statement, which describes in more detail how the Company’s executive compensation policies and procedures operate and are designed to achieve our compensation objectives, as well as the Summary Compensation Table and other related compensation tables and narrative, appearing on pages 22 through 27 of this proxy statement, which provide detailed information on the compensation of our named executive officers. The Compensation Committee and the Board believe that the policies and procedures articulated in the Executive Compensation section are effective in achieving our goals and that the compensation of our named executive officers reported in this proxy statement reflects and supports these compensation policies and procedures.

While the vote is advisory, the Board and the Compensation Committee will consider the outcome of the vote when considering future executive compensation arrangements.

Vote Required

To approve Proposal 5, a majority of the votes cast by stockholders present in person or represented by proxy at the 2020 Annual Meeting and voting on the matter must vote FOR Proposal 5. Abstentions and “brokernon-votes” will not be counted as votes cast or shares voting on Proposal 5 and will have no effect on the vote.

The Board of Directors recommends a vote FOR Proposal 5.

REPORT OF THE AUDIT AND FINANCE COMMITTEE

The Audit and Finance Committee of the Board consists entirely of independent directors who are not officers or employees of Agenus. The Board has adopted a written charter for the Audit and Finance Committee, the current version of which is available on our website at http://investor.agenusbio.com/board-committees. No material on our website is part of this proxy statement.

In the course of its oversight of the Company’s reporting process, the Audit and Finance Committee of the Board has (1) reviewed and discussed with management the Company’s audited consolidated financial statements and management’s assessment of the effectiveness of internal control over financial reporting for the fiscal year ended December 31, 2019, (2) discussed with KPMG LLP, our independent registered public accounting firm, the matters required to be discussed pursuant to the applicable requirements of the Public Company Accounting Oversight Board and SEC, and (3) discussed with KPMG LLP matters relating to its independence, including a review of audit andnon-audit fees and the written disclosures and letter from KPMG LLP pursuant to applicable requirements of the Public Company Accounting Oversight Board regarding the independent accountant’s communications with the Audit and Finance Committee concerning independence.

Based on the foregoing review and discussions, the Audit and Finance Committee recommended to the Board that the audited consolidated financial statements be included in the Company’s Annual Report onForm 10-K for the year ended December 31, 2019 for filing with the SEC.

ADDITIONAL INFORMATION2023 ANNUAL MEETING

Stockholder Proposals for 20212023 Annual Meeting of Stockholders

Proposals to be included in the Company’s proxy statement. Under SEC rules, if a stockholder wants us to include a proposal in our proxy statement and form of proxy for presentation at our 20212023 Annual Meeting of Stockholders, the proposal must comply with Rule14a-8 under the Exchange Act and must also meet the advance notice requirements in our bylaws applicable to all stockholder proposals (as described in the following paragraphs).

Proposals to be brought before an annual meeting.meeting. Under ourby-laws, bylaws, a stockholder must follow certain procedures to nominate persons for election as directors or to introduce an item of business at an annual meeting of stockholders. Among other requirements, these procedures require any nomination or proposed item of business to be submitted in writing to our Chairman of the Board or Corporate Secretary at our principal executive offices. Assuming our 20212023 Annual Meeting of Stockholders is not more than 30 days before or 30 days after June 16, 2021,8, 2023, if you wish to bring business before the 20212023 Annual Meeting of Stockholders, you must give us written notice by December 29, 2020.31, 2022.

However, if at least 60 days’ notice or prior public disclosure of the date of the 20212023 Annual Meeting of Stockholders is given or made and the date of the 20212023 Annual Meeting of Stockholders is not within 30 days before or after June 16, 2021,8, 2023, notice by the stockholder must be received by the Company 45 days prior to the date of the 20212023 Annual Meeting of Stockholders. If less than 60 days’ notice or prior public disclosure of the date of the 20212023 Annual Meeting of Stockholders is given or made and the date of the 20212023 Annual Meeting of Stockholders is not within 30 days before or after June 16, 2021,8, 2023, notice by the stockholder must be received by the Company no later than 15 days after the date Agenus sends notice of the 20212023 Annual Meeting of Stockholders. If a stockholder fails to provide timely notice of a proposal to be presented at the 20212023 Annual Meeting of Stockholders, the proxies designated by the Board will have discretionary authority to vote on the proposal.

Householding of Meeting Materials

Some banks, brokers, and other nominee record holders may be participating in the practice of “householding” proxy statements and annual reports. This means that only one copy of our proxy statement or annual report may have been sent to multiple stockholders in your household. We will promptly provide a separate copy of either document to you if you contact Investor Relations at Agenus Inc., 3 Forbes Road, Lexington, Massachusetts 02421, or telephone ore-mail Investor Relations at800-962-2436781-674-4400 orIR@agenusbio.com. investor@agenusbio.com. If you want to receive separate copies of the annual report and proxy statement in the future or if you are receiving multiple copies and would like to receive only one printed copy for your household, you should contact your bank, broker or other nominee record holders, or you may contact us.

APPENDIX B

AGENUS INC.

2019 EMPLOYEE STOCK PURCHASE PLAN

Exhibit A, which is incorporated by reference, defines certain terms used inIN WITNESS WHEREOF, the Plan and sets forth operational rules related to those terms.

The Plan is intended to enable Eligible Employees to purchase shares of Stock in offerings under the Plan, and thereby acquire an interest in the Company. The Plan is intended to qualify as an “employee stock purchase plan” under Section 423 and to be exempt from the requirements of Section 409A, and will be construed consistently with that intent.

(a)Number of Shares. Subject to adjustment as provided in Section 16, 500,000 shares of Stock are available for purchase pursuant to the exercise of Options granted under the Plan (the “Share Pool”). Shares of Stock will not be treated as issued under the Plan, and will not reduce the Share Pool, unless and until, and to the extent, the shares are actually issued pursuant to the exercise of Options under the Plan. If any Option expires or terminates for any reason without having been exercised in full or ceases for any reason to be exercisable in whole or in part, the unpurchased shares of Stock subject to such Option will not reduce the Share Pool. If, on any Exercise Date, the total number of shares of Stock that would otherwise be subject to Options granted under the Plan exceeds the number of shares then available in the Share Pool, the Administrator will make a pro rata allocation of the shares remaining available in as uniform a manner as practicable and as it determines to be equitable. In such event, the Administrator will give written notice to each Participant affected by such reduction.

(b)Type of Shares. The shares of Stock issued under the Plan may be shares of authorized but unissued Stock, treasury Stock, or Stock acquired in an open-market transaction. No fractional shares of Stock will be issued under the Plan.

(a)Eligibility Requirements.Subject to the limitations contained in the Plan, each Employee (i) who is employed by the Company or a Designated Subsidiary, as applicable, on the first day of an Option Period and (ii) who satisfies the requirements set forth in the Plan, will be an Eligible Employee.

(b)Five Percent Shareholders.No Employee may be granted an Option under the Plan if, immediately after the Option is granted, the Employee would own (or pursuant to Section 424(d) of the Code would be deemed to own) shares possessing five percent (5%) or more of the total combined voting power or value of all classes of shares of the Company or of its Parent or Subsidiaries, if any.

(c)Additional Requirements.The Administrator may, for Option Periods that have not yet commenced, establish additional or other eligibility requirements, or amend the eligibility requirements set forth in subsection (a) above, in each case, consistent with the requirements of Section 423.

The Plan will generally be implemented by a series of separate offerings referred to as “Option Periods.” Unless otherwise determined by the Administrator, the Option Periods will be successive periods of

approximately six (6) months commencing on the first Business Day in January and July of each year, anticipated to be on or around January 1 and July 1, and ending approximately six (6) months later on the last Business Day in June or December, as applicable, of each year, anticipated to be on or around June 30 and December 31. The last Business Day of each Option Period will be an “Exercise Date.” The Administrator may change the Exercise Date and the commencement date, ending date and duration of Option Periods, in each case, to the extent permitted by Section 423. In no event may any Option be exercised after twenty-seven (27) months from its grant date.

Subject to the limitations set forth in the Plan and the Maximum Share Limit (as defined below), on the first day of an Option Period, each Participant automatically will be granted an Option to purchase shares of Stock on the Exercise Date;provided,however, that no Participant will be granted an Option under the Plan that permits the Participant’s right to purchase shares of Stock under the Plan and under all other employee stock purchase plans of the Company and its Parent and Subsidiaries, if any, to accrue at a rate that exceeds $25,000 in Fair Market Value (or such other maximum as may be prescribed from time to time by the Code) for each calendar year during which any Option granted to such Participant is outstanding at any time, as determined in accordance with Section 423(b)(8) of the Code.

(a)Enrollment Election Form. To participate in an Option Period, an Eligible Employee must execute and deliver to the Administrator an enrollment election form, in accordance with the procedures prescribed by, and in a form acceptable to, the Administrator. Such enrollment election form must be delivered not later than ten (10) Business Days prior to the first day of an Option Period, or such other time as specified by the Administrator. The Eligible Employee will become a Participant as of the first day of the Option Period for which he or she timely delivered such enrollment election form and will remain a Participant with respect to subsequent Option Periods until his or her participation in the Plan is terminated as provided herein.

(b)Election Amount.Each enrollment election form will (i) authorize either a whole percentage of the Eligible Employee’s Eligible Compensation, greater than one percent (1%) of Eligible Compensation, or a specified dollar amount, in each case, to be deducted from the Eligible Employee’s pay during each payroll period occurring during the applicable Option Period and/or (ii) provide for a specified dollar amount to be paid in a lump sum in cash for the applicable Option Period.

(c)Participant Account.All payroll deductions made pursuant toundersigned has duly executed this Section 7, and all lump sum cash payments made by a Participant during an Option Period prior to the applicable Exercise Date, will be credited to the Participant’s Account. Amounts credited to Participants’ Account will not be required to be set aside in trust or otherwise segregated from the Company’s general assets.

(d)Changes to Enrollment Election During an Option Period.During an Option Period, elections and rates of contribution may not be reduced or increased. A Participant may terminate his or her election during an Option Period by terminating his or her participation in the Plan.

(e)Changes to Election for Subsequent Option Periods. A Participant’s election will remain in effect for subsequent Option Periods unless the Participant delivers a new election not later than ten (10) Business Days prior to the first day of the subsequent Option Period, or such other time as specified by the Administrator, or the Participant’s participation in the Plan is terminated pursuant to Section 13 or Section 14.

A Participant must pay for shares of Stock purchased upon the exercise of an Option with the accumulated payroll deductions credited to the Participant’s Account during the applicable Option Period, by lump sum cash payment delivered to the Company prior to the start of the applicable Option Period, or a combination thereof.

The Purchase Price of shares of Stock issued pursuant to the exercise of an Option on each Exercise Date will be eighty-five percent (85%) (or such other percentage specified by the Administrator to the extent permitted under Section 423) of the lesser of (i) the Fair Market Value of a share of Stock on the date on which the Option was granted pursuant to Section 6 (i.e., the first day of the Option Period) and (ii) the Fair Market Value of a share of Stock on the date on which the Option is deemed exercised pursuant to Section 10 (i.e., the Exercise Date).