Filed by the Registrant

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Filed by a Party other than the Registrant

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Preliminary Proxy Statement

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

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material Pursuant to § 240.14a-12

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No fee required.

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Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

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Title of each class of securities to which transaction applies:

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Proposed maximum aggregate value of transaction:

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Total fee paid:

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Fee paid previously with preliminary materials.

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Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously.  Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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Amount Previously Paid:

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Form, Schedule or Registration Statement No.:

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Filing Party:

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Date Filed:

NNNNNNNNNNNN . + NNNNNN C 1234567890 000004 ENDORSEMENT_LINE______________ SACKPACK_____________ MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 ADD 5 ADD 6 Vote by Internet • Go to www.envisionreports.com/XNCR • Or scan the QR code with your smartphone • Follow the steps outlined on the secure website Important Notice Regarding the Availability of Proxy Materials for the Xencor, Inc. Shareholder Meeting to be Held on June 22, 2017 Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual shareholders’ meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy. The items to be voted on and location of the annual meeting are on the reverse side. Your vote is important! This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The proxy statement and annual report to shareholders are available at: www.envisionreports.com/XNCR Easy Online Access — A Convenient Way to View Proxy Materials and Vote When you go online to view materials, you can also vote your shares. Step 1: Go to www.envisionreports.com/XNCR to view the materials. Step 2: Click on Cast Your Vote or Request Materials. Step 3: Follow the instructions on the screen to log in. Step 4: Make your selection as instructed on each screen to select delivery preferences and vote. Q When you go online, you can also help the environment by consenting to receive electronic delivery of future materials. Obtaining a Copy of the Proxy Materials – If you want to receive a copy of these documents, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed on the reverse side on or before June 12, 2017 to facilitate timely delivery. + 2 N O T C O Y 02LP6B NNNNNNNNN Shareholder Meeting Notice1234 5678 9012 345 IMPORTANT ANNUAL MEETING INFORMATION

. Xencor, Inc.’s Annual Meeting of Shareholders will be held on June 22, 2017 at the Courtyard Marriott Monrovia, 700 W. Huntington Dr., Monrovia, California 91016, at 1:30 p.m. Pacific Time. Proposals to be voted on at the meeting are listed below along with the Board of Directors’ recommendations. The Board recommends a vote FOR all nominees, and FOR Proposal 2 and 3, and “ONE YEAR FREQUENCY” for Proposal 4: 1. 2. 3. 4. Election of Directors. Proposal to ratify RSM US, LLP as the independent public accounting firm for 2017. Proposal to approve, on an advisory basis, the compensation of our named executive officers as disclosed in these proxy materials. To approve, on an advisory basis, the frequency of future advisory votes on executive compensation. PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must vote online or request a paper copy of the proxy materials to receive a proxy card. If you wish to attend and vote at the meeting, please bring this notice with you. Directions to the Xencor 2017 Annual Meeting Directions from... Burbank Bob Hope (BUR) — Take the 5 Freeway South to the 134 Freeway East to the 210 Freeway East. Exit Huntington Drive and make a left. As you go under the freeway, the hotel will be to the right. LA/Ontario Int’l (ONT) — Take the 10 Freeway West to the 57 Freeway North to the 210 Freeway West. Exit Monrovia-Huntington Drive, make a left. The hotel will be immediately to the right. Los Angeles Int’l (LAX) — Take the 105 Freeway East to the 605 Freeway North to the 210 Freeway West. Travel approximately 4 miles on the 210 Freeway, take the Monrovia-Huntington Drive exit and make a left. The hotel is immediately to the right. Here’s how to order a copy of the proxy materials and select a future delivery preference: Paper copies: Current and future paper delivery requests can be submitted via the telephone, Internet or email options below. Email copies: Current and future email delivery requests must be submitted via the Internet following the instructions below. If you request an email copy of current materials you will receive an email with a link to the materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a set of proxy materials. g Internet – Go to www.envisionreports.com/XNCR. Click Cast Your Vote or Request Materials. Follow the instructions to log in and order a copy of the current meeting materials and submit your preference for email or paper delivery of future meeting materials. Telephone – Call us free of charge at 1-866-641-4276 and follow the instructions to log in and order a paper copy of the materials by mail for the current meeting. You can also submit a preference to receive a paper copy for future meetings. Email – Send email to investorvote@computershare.com with “Proxy Materials Xencor, Inc.” in the subject line. Include in the message your full name and address, plus the number located in the shaded bar on the reverse, and state in the email that you want a paper copy of current meeting materials. You can also state your preference to receive a paper copy for future meetings. To facilitate timely delivery, all requests for a paper copy of the proxy materials must be received by June 12, 2017. g g 02LP6B Shareholder Meeting Notice

MMMMMMMMMMMM . MMMMMMMMMMMMMMM C123456789 000004 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext ENDORSEMENT_LINE______________ SACKPACK_____________ Electronic Voting Instructions Available 24 hours a day, 7 days a week! Instead of mailing your proxy, you may choose one of the voting methods outlined below to vote your proxy. VALIDATION DETAILS ARE LOCATED BELOW IN THE TITLE BAR. Proxies submitted by the Internet or telephone must be received by 11:59p.m., Eastern Time, on June 21, 2017. MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 ADD 5 ADD 6 Vote by Internet • Go to www.envisionreports.com/XNCR • Or scan the QR code with your smartphone • Follow the steps outlined on the secure website Vote by telephone • Call toll free 1-800-652-VOTE (8683) within the USA, US territories & Canada on a touch tone telephone • Follow the instructions provided by the recorded message Using a black ink pen, mark your votes with an X as shown in this example. Please do not write outside the designated areas. q IF YOU HAVE NOT VOTED VIA THE INTERNET OR TELEPHONE, FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. q Proposals — The Board recommends a vote FOR all nominees, and FOR Proposal 2 and 3, and “ONE YEAR FREQUENCY” for Proposal 4. + 1. Election of Directors: For Withhold For Withhold For Withhold 01 - Dr. Bassil I. Dahiyat 02 - Dr. Kevin C. Gorman 03 - Dr. A. Bruce Montgomery 04 - Kurt Gustafson 05 - Yujiro S. Hata For Against Abstain 1 Year 2 Years 3 Years Abstain 2. Proposal to ratify RSM US, LLP as the independent public accounting firm for 2017. 4. To approve, on an advisory basis, the frequency of future advisory votes on executive compensation. 3. Proposal to approve, on an advisory basis, the compensation of our named executive officers as disclosed in the proxy materials. Non-Voting Items Change of Address — Please print your new address below. Comments — Please print your comments below. Meeting Attendance Mark the box to the right if you plan to attend the Annual Meeting. Authorized Signatures — This section must be completed for your vote to be counted. — Date and Sign Below Please sign exactly as name(s) appears hereon. Joint owners should each sign. When signing as attorney, executor, administrator, corporate officer, trustee, guardian, or custodian, please give full title. Date (mm/dd/yyyy) — Please print date below. Signature 1 — Please keep signature within the box. Signature 2 — Please keep signature within the box. MMMMMMMC 1234567890 J N T MR A SAMPLE (THIS AREA IS SET UP TO ACCOMMODATE 140 CHARACTERS) MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND + 1 U P X3 2 8 8 4 0 1 02LP4B MMMMMMMMM C B A Xencor, Inc. Annual Meeting Proxy Card1234 5678 9012 345 X IMPORTANT ANNUAL MEETING INFORMATION

. q IF YOU HAVE NOT VOTED VIA THE INTERNET OR TELEPHONE, FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. q Proxy — Xencor, Inc. Notice of 2017 Annual Meeting of Shareholders Courtyard Marriott Monrovia, 700 W. Huntington Dr., Monrovia, California 91016 Proxy Solicited by Board of Directors for Annual Meeting — June 22, 2017 Bassil I. Dahiyat or John J. Kuch, or any of them, each with the power of substitution, are hereby authorized to represent and vote the shares of the undersigned, with all the powers which the undersigned would possess if personally present, at the Annual Meeting of Stockholders of Xencor, Inc. to be held on June 22, 2017 or at any postponement or adjournment thereof. Shares represented by this proxy will be voted by the stockholder. If no such directions are indicated, the Proxies will have authority to vote FOR all nominees, FOR Proposal 2 AND 3 AND, “ONE YEAR” FOR Proposal 4. In their discretion, the Proxies are authorized to vote upon such other business as may properly come before the meeting. (Items to be voted appear on reverse side.)