MONROVIA, Calif., October 11, 2013— Xencor, Inc. today announced the filing of a registration statement on Form S-1 with the Securities and Exchange Commission for a proposed initial public offering of shares of its common stock. All of the shares to be sold in the proposed offering will be offered by Xencor. The number of shares and price range for the offering have not been determined. Xencor has applied for a listing of its common stock on The NASDAQ Stock Market under the symbol "XNCR".

Credit Suisse Securities (USA) LLC and Leerink Swann LLC will act as joint book-running managers of the offering. Wedbush PacGrow Life Sciences is acting as a co-manager for the offering. The offering will be made only by means of a prospectus. A copy of the preliminary prospectus relating to and describing the terms this offering may be obtained, when available, by contacting Credit Suisse Securities (USA) LLC, Attention: Prospectus Department, One Madison Avenue, New York, NY 10010, by calling toll-free (800) 221-1037, or by emailing newyork.prospectus@credit-suisse.com; or Leerink Swann LLC, Attention: Syndicate Department, One Federal Street, 37th Floor, Boston, MA, 02110, or by email at Syndicate@Leerink.com, or by phone at 800-808-7525.

A registration statement relating to these securities has been filed with the Securities and Exchange Commission but has not yet become effective. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Xencor
Xencor is a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of autoimmune diseases, asthma and allergic diseases, and cancer. Currently, five antibodies are in clinical development internally and with partners that have been engineered with Xencor's XmAb® technology. Xencor's internally-discovered programs include XmAb5871, in Phase 1b/2a clinical trials for the treatment of rheumatoid arthritis and lupus, XmAb7195 in preclinical development for the treatment of asthma, and XmAb5574/MOR208 which has been licensed to MorphoSys AG and is in Phase 2 clinical trials for the treatment of acute lymphoblastic leukemia and non-Hodgkin lymphoma. Xencor's XmAb antibody engineering technology enables small changes to the structure of monoclonal antibodies resulting in new mechanisms of therapeutic action. Xencor partners include Amgen, Merck, Janssen R&D LLC and Boehringer Ingelheim.

Contact:
Jason Spark
Canale Communications for Xencor
Tel: 619-849-6005
jason@canalecomm.com