Xencor Announces the Planned Retirement of Chief Medical Officer Paul Foster, M.D.

Xencor, Inc. (NASDAQ: XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer, autoimmune diseases, asthma and allergic diseases, today announced that Paul Foster, M.D., senior vice president and chief medical officer at Xencor, plans to retire from Xencor effective October 31, 2019, following a transition period with a successor. Dr. Foster's career spans 35 years in academic research, medical practice and industry leadership. For ten years, he has led Xencor's clinical development strategy, as both chief medical officer and as a consultant in a substantially similar capacity. Xencor has initiated an executive search for a successor.

"On behalf of Xencor's board and employees, we thank Paul for his leadership and significant contributions throughout our transformation into a clinical-stage organization," said Bassil Dahiyat, Ph.D., president and chief executive officer at Xencor. "We are grateful that we will continue to benefit from Paul's tremendous expertise throughout the search for his successor and for his assistance during a transition period."

Dr. Foster said, "Our dedicated team is translating innovative science into potential breakthrough medicines to improve patient outcomes and quality of life. I am thankful for the opportunity to have served with them and am proud of our achievements over the past decade, especially advancing a diverse pipeline of novel XmAb® bispecific antibodies into early-stage clinical development."

About Xencor, Inc.

Xencor is a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer, autoimmune diseases, asthma and allergic diseases. Currently, 14 candidates engineered with Xencor's XmAb® technology are in clinical development internally and with partners. Xencor's XmAb antibody engineering technology enables small changes to the structure of monoclonal antibodies resulting in new mechanisms of therapeutic action. For more information, please visit www.xencor.com.

Forward-Looking Statements

Statements contained in this press release regarding matters that are not historical facts are forward-looking statements within the meaning of applicable securities laws, including, but not limited to, the quotations from Xencor's chief executive officer and any expectations relating to the search for a successor to Dr. Foster. Such statements involve known and unknown risks, uncertainties and other factors that may cause actual results, performance or achievements and the timing of events to be materially different from those implied by such statements, and therefore these statements should not be read as guarantees of future performance or results. Such risks include, without limitation, the risks associated with the process of discovering, developing, manufacturing and commercializing drugs that are safe and effective for use as human therapeutics and other risks described in Xencor's public securities filings. For a discussion of these and other factors, please refer to Xencor's annual report on Form 10-K for the year ended December 31, 2018 as well as Xencor's subsequent filings with the Securities and Exchange Commission. All forward-looking statements are based on Xencor's current information and belief as well as assumptions made by Xencor. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. This caution is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. All forward-looking statements are qualified in their entirety by this cautionary statement and Xencor undertakes no obligation to revise or update this press release to reflect events or circumstances after the date hereof, except as required by law.