Xencor 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 Registrantx

Filed by a Party other than the Registranto

Check the appropriate box:

XENCOR, 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 all boxes that apply):

April 27, 2026

Fellow stockholder,

Xencor is a clinical development-stage biotechnology company advancing cutting-edge XmAb® engineered antibodies for patients affected by cancer and autoimmune disease. The plug-and-play nature of our XmAb Fc domains and our protein engineering expertise have enabled a broad clinical pipeline of antibody-based drug candidates for patients with high unmet medical needs. We take a focused approach to research and development with the goals of delivering best-in-class medicines and commercializing our own products.

In 2025, we continued to execute across multiple early- and mid-stage clinical studies of novel XmAb drug candidates in oncology and autoimmune diseases, advancing a pipeline built on our world-class protein engineering capabilities. We are focused on developing targeted T cell-engaging bispecific antibodies, including XmAb819 (ENPP3 x CD3) and XmAb541 (CLDN6 x CD3) for solid tumors, and plamotamab (CD20 x CD3) and XmAb657 (CD19 x CD3) for autoimmune diseases, where targeted B-cell depletion represents a validated therapeutic approach. Our TL1A programs, including XmAb942, a potential best-in-class anti-TL1A antibody, and XmAb412, a TL1A x IL-23p19 bispecific antibody, together represent a differentiated strategy in inflammatory bowel disease and potentially other inflammatory disorders.

In oncology, we reported encouraging initial dose-escalation data for XmAb819 in advanced clear cell renal cell carcinoma and early dose-escalation data for XmAb541 in ovarian, endometrial and germ cell cancers. XmAb819 was generally well tolerated and demonstrated a 25% partial response rate and a 70% disease control rate among efficacy-evaluable patients within the target dose range. XmAb541 also demonstrated confirmed partial responses in patients with ovarian cancer and germ cell tumors. Enrollment continues for both programs, and in the second half of 2026, we expect to present additional clinical data to support dose selection and advancement toward pivotal studies planned for 2027.

In autoimmune diseases, we presented first-in-human data for XmAb942, demonstrating favorable tolerability and an extended half-life supporting a 12-week maintenance dosing interval, and we initiated the global Phase 2b XENITH-UC study in ulcerative colitis. We also advanced XmAb412 as our lead TL1A x IL-23p19 bispecific antibody and plan to initiate first-in-human studies in the second half of 2026. In addition, we initiated proof-of-concept studies of plamotamab in rheumatoid arthritis and XmAb657 in idiopathic inflammatory myopathies.

We look forward to further progress across our partnered pipeline, with multiple candidates now being evaluated in or advancing rapidly toward Phase 3 studies. We ended 2025 with cash, cash equivalents and marketable debt securities of $610.8 million, and under our current operating plans, we believe we are well positioned to reach meaningful clinical decision points across our pipeline, while focusing resources on our highest-value opportunities.

At this year's annual meeting, we are asking for stockholders to vote FOR the proposed amendment to our 2023 Equity Incentive Plan to increase the authorized shares reserved for issuance, among other items. Our future success depends on our ability to attract, retain and motivate highly qualified employees across our entire organization, and competition for talent in oncology and autoimmune drug development remains exceptionally strong. The requested increase represents approximately 5.4% of our outstanding shares as of March 31, 2026 and is designed to cover approximately one year of equity grants. Based on our analysis of peer companies in the biotechnology industry and taking a holistic and industry-based approach to evaluating equity proposals, we believe this request is reasonable and necessary.

We appreciate your continued support and perspective. You are invited to join us at our 2026 Annual Meeting of Stockholders on Tuesday, June 16, 2026 at 1:00 p.m. PT at our laboratories and headquarters in Pasadena, California. As always, please reach out to our investor relations personnel with any questions about our strategy or governance practices.

Bassil I. Dahiyat, Ph.D.

President, Chief Executive Officer and Director

465 North Halstead Street, Suite 200

Pasadena, CA 91107

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held On June 16, 2026

Dear Stockholder:

You are cordially invited to attend the 2026 Annual Meeting of Stockholders of Xencor, Inc., a Delaware corporation (the “Company”) to be held on Tuesday, June 16, 2026 at 1:00 p.m. Pacific Time at the Company’s headquarters, 465 North Halstead Street, Suite 200, Pasadena, California 91107. We are holding the meeting for the following purposes:

1. To elect the nine nominees to the Board of Directors named in the accompanying Proxy Statement to serve until the next annual meeting and until their successors are duly elected and qualified;

2. To ratify the selection by the Audit Committee of the Board of Directors of KPMG LLP as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2026;

3. To approve the proposed amendment to the Company's Amended and Restated 2023 Equity Incentive Plan to increase the number of authorized shares reserved for issuance thereunder by 4,000,000 shares;

4. To approve, on an advisory (non-binding) basis, the compensation of the Company’s named executive officers, as disclosed in the accompanying Proxy Statement; and

5. To conduct any other business properly brought before the meeting or any adjournments or postponements thereof.

These items of business are more fully described in the Proxy Statement accompanying this Notice (the “Proxy Statement”).

The record date for the annual meeting is April 17, 2026. Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof. This Notice is being mailed to all stockholders of record entitled to vote at the annual meeting on or about April 27, 2026.

Our Board of Directors recommends that you vote FOR the election of each of the director nominees and FOR Proposals 2, 3 and 4.

If we decide to make any change in the date, time or location, or to hold the annual meeting virtually by remote communication, an announcement of such changes will be made through a press release that will also be filed with the Securities and Exchange Commission as additional proxy materials and we will post details on our website athttps://investors.xencor.com. Please check our website in advance of the date of the annual meeting if you are planning to attend in person. If we elect to hold a virtual meeting, this will not have any impact on your ability to vote by proxy using the enclosed proxy card, vote by proxy on the internet or vote by proxy over the telephone, each as explained in the Proxy Statement. As always, we encourage you to vote your shares prior to the annual meeting.

April 27, 2026

You are cordially invited to attend the annual meeting. Whether or not you expect to attend the meeting, please complete, date, sign and return the proxy mailed to you as promptly as possible in order to ensure your representation at the meeting. Even if you have voted by proxy, you may still vote if you attend the meeting. Please note, however, that if your shares are held of record by a broker, bank or other nominee and you wish to vote at the meeting, you must obtain a proxy issued in your name from that record holder.

Important Notice Regarding the Availability of Proxy Materials for the Stockholders Meeting to Be Held on June 16, 2026: Our Notice of Annual Meeting of Stockholders, Proxy Statement and Annual Report on Form 10-K for the fiscal year ended December 31, 2025 will be available at https://web.viewproxy.com/xncr/2026.

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