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May 06, 2019

Xencor Doses First Patient in Phase 1 Study of XmAb®23104 for the Treatment of Patients with Advanced Solid Tumors

— XmAb23104, a PD-1 x ICOS bispecific antibody, is the sixth XmAb® antibody engineered with Xencor’s bispecific Fc domain to enter clinical development —

MONROVIA, Calif.--(BUSINESS WIRE)--May 6, 2019-- 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 the first patient has been dosed in XmAb23104-01 (DUET-3), a Phase 1 clinical study to evaluate the safety and tolerability of XmAb23104, a bispecific antibody that simultaneously targets the immune receptors PD-1 and ICOS, for the treatment of patients with advanced solid tumors.

“Despite the success of checkpoint inhibitors, the benefit of therapy is not universal. We designed XmAb23104 to improve anti-tumor responses through a novel mechanism of action that activates and induces proliferation of T cells through simultaneous checkpoint inhibition and co-stimulation,” said Paul Foster, M.D., senior vice president and chief medical officer at Xencor. “Both PD-1 and ICOS are more highly expressed on T cells in the tumor microenvironment than on those in the periphery, and through preferential targeting of cells that express both of these receptors, we hope to be able to drive a stronger anti-tumor response than anti-PD-1 monotherapy with improved tolerability for patients.”

DUET-3 is a Phase 1, multiple-dose, dose-escalation study that will characterize the safety and tolerability, pharmacokinetics, pharmacodynamics, immunogenicity and preliminary anti-tumor activity of intravenous administration of XmAb23104 in patients with selected advanced solid tumors. For more information about DUET-3, please visit https://clinicaltrials.gov (identifier: NCT03752398).

About XmAb®23104

XmAb23104 is a bispecific antibody that simultaneously targets PD-1, an immune checkpoint receptor, and ICOS, an immune co-stimulatory receptor, and is designed to promote tumor-selective T-cell activation. Xencor’s XmAb® bispecific Fc domain serves as the scaffold for these two antigen binding domains and confers long circulating half-life, stability and ease of manufacture. XmAb bispecific Fc domains have been engineered to eliminate Fc gamma receptor (FcγR) binding, with the intent to prevent activation and/or depletion of T cells via engagement by FcγR-expressing cells. XmAb23104 is being evaluated in XmAb23104-01 (DUET-3), a Phase 1 study for the treatment of advanced solid tumors.

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, 13 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 medical officer and any expectations relating to Xencor's financial expectations and business, the timing and success of clinical trials, future product candidates, Xencor's research and development programs, partnering efforts and capital requirements. 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.

Source: Xencor, Inc.

Charles Liles

Media Contact
Jason I. Spark
Canale Communications