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Xencor, Inc. Important Notice Regarding the Availability of Proxy Materials P.O. BOX 8016, CARY, NC 27512-9903 Stockholders Meeting to be held on June 23, 2022 For Stockholders of record as of April 25, 2022 This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. This is not a ballot. You cannot use this notice to vote your shares. We encourage you to access and review all of the important information contained in the proxy materials before voting. To view the proxy materials, and to obtain directions to attend the meeting, go to: www.proxydocs.com/XNCR To vote your proxy while visiting this site, you will need the 12 digit control number in the box below. Under United States Securities and Exchange Commission rules, proxy materials do not have to be delivered in paper. Proxy materials can be distributed by making them available on the internet. For a convenient way to view proxy materials and VOTE go to www.proxydocs.com/XNCR Have the 12 digit control number located in the shaded box above available when you access the website and follow the instructions. If you want to receive a paper or e-mail copy of the proxy material, you must request one. There is no charge to you for requesting a copy. In order to receive a paper package in time for this year's meeting, you must make this request on or before June 13, 2022. To order paper materials, use one of the following methods. When requesting via the Internet or telephone you will need the 12 digit control number located in the shaded box above. * If requesting material by e-mail, please send a blank e-mail with the 12 digit control number (located above) in the subject line. No other requests, instructions OR other inquiries should be included with your e-mail requesting material. Xencor, Inc. Meeting Type: Annual Meeting of Stockholders Date: Thursday, June 23, 2022 Time: 1:30 PM, Pacific Time Place: 111 West Lemon Avenue Monrovia, California 91016 SEE REVERSE FOR FULL AGENDA * E-MAIL paper@investorelections.com TELEPHONE (866) 648-8133 INTERNET www.investorelections.com/XNCR

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Xencor, Inc. Annual Meeting of Stockholders THE BOARD OF DIRECTORS RECOMMENDS A VOTE: FOR ON PROPOSALS 1, 2 AND 3 PROPOSAL Election of Directors 1.01 Bassil I. Dahiyat, Ph.D. 1. 1.02 Ellen G. Feigal, M.D. 1.03 Kevin C. Gorman, Ph. D. 1.04 Kurt A. Gustafson 1.05 Yujiro S. Hata 1.06 A. Bruce Montgomery, M.D. 1.07 Richard J. Ranieri 1.08 Dagmar Rosa-Bjorkeson 2. To ratify the selection by the Audit Committee of the Board of Directors of RSM US LLP as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2022. To hold a non-binding advisory vote on the compensation of the Company’s named executive officers, as disclosed in the proxy statement. 3 4. To conduct any other business properly brought before the meeting or any adjournments or postponements thereof.