Xencor to Present Data from Four Preclinical XmAb® 2+1 Bispecific Antibody and Cytokine Programs at AACR Virtual Annual Meeting II

Xencor, Inc. (NASDAQ: XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer and autoimmune diseases, today announced it will present new preclinical data on three XmAb^® 2+1 bispecific antibody programs and an IL-12-Fc cytokine program at the second session of the American Association for Cancer Research (AACR) Virtual Annual Meeting, being held June 22-24, 2020. Abstracts for these poster presentations are now available on AACR’s website.

“Xencor has expanded our T-cell redirecting CD3 class of bispecific antibodies with a mixed valency format that uses the same heterodimeric Fc domain as our other bispecific antibodies and cytokines, but with two identical tumor targeting domains and one CD3 targeting domain—the XmAb 2+1 bispecific antibody. These two tumor-targeting binding domains can bind together when there's more target present, a property called avidity,” said John Desjarlais, Ph.D., senior vice president and chief scientific officer at Xencor. “Our 2+1 format, along with avidity tuning, enables higher selectivity for tumor antigen-expressing cells and greater flexibility in tuning the potency and potentially the efficacy and tolerability of the molecule, as well as the ability to address an expanded set of tumor antigens.”

“At AACR, we are presenting data from preclinical models showing strong, selective tumor killing from XmAb 2+1 bispecific antibody programs that target PSMA, mesothelin and ENPP3, the last of which is an underexplored tumor antigen overexpressed on renal cell carcinomas. In addition, we are introducing our next cytokine program in oncology, a potency-reduced IL-12 Fc fusion, which demonstrates strong-anti-tumor activity in preclinical models, as a single agent and in combination with an anti-PD1 antibody,” said Dr. Desjarlais.

Poster Presentation Details

• Abstract: 2286
• Title: XmAb30819, an XmAb 2+1 ENPP3 x CD3 bispecific antibody for RCC, demonstrates safety and efficacy in in-vivo preclinical studies
• Session: Therapeutic Antibodies 1

• Abstract: 5663
• Title: Affinity tuned XmAb 2+1 PSMA x CD3 bispecific antibodies demonstrate selective activity in prostate cancer models
• Session: Therapeutic Antibodies 4

• Abstract: 5654
• Title: Affinity tuned XmAb 2+1 anti-mesothelin x anti-CD3 bispecific antibody induces selective T cell directed cell cytotoxicity of human ovarian cancer cells
• Session: Therapeutic Antibodies 4

• Abstract: 5549
• Title: Potency-reduced IL-12 heterodimeric Fc-fusions exhibit strong anti-tumor activity
• Session: Immunomodulatory Agents and Interventions 2

These posters and audio descriptions will be available to registrants of the AACR Virtual Annual Meeting at 9:00 a.m. EDT on Monday, June 22. Posters will be archived under "Events & Presentations" in the Investors section of the Company's website located at www.xencor.com.

About Xencor, Inc.

Xencor is a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer and autoimmune diseases. Currently, 17 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 senior vice president and chief scientific officer and any expectations relating to future product candidates and Xencor's research and development programs. 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, 2019 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.

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