Xencor to Present Data from the Phase 1 Study of XmAb®20717 and Three Research Programs at the SITC Annual Meeting

Xencor, Inc. (NASDAQ:XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer and autoimmune diseases, today announced four poster presentations at the 35th Annual Meeting of the Society for Immunotherapy of Cancer, being held virtually November 9-14, 2020.

The presentations will include updated results from the ongoing Phase 1 dose-escalation and expansion study of XmAb^®20717, a PD-1 x CTLA-4 bispecific antibody, in patients with advanced solid tumors. While dose-escalation continues, planned expansion cohorts have enrolled patients with melanoma, non-small cell lung cancer, renal cell carcinoma, prostate cancer, and other cancers without approved checkpoint therapies. New data from three preclinical-stage programs, including the IL-12-Fc cytokine program, the CD28 bispecific antibody platform, and the PD-1 x TGF?R2 bispecific antibody program, will also be presented.

Presentation Details

• Abstract 648, "Preliminary safety, pharmacokinetics/pharmacodynamics, and antitumor activity of XmAb20717, a PD-1 x CTLA-4 bispecific antibody, in patients with advanced solid tumors"
  
• Abstract 564, "Potency-reduced and extended half-life IL-12 heterodimeric Fc-fusions exhibit strong anti-tumor activity with potentially improved therapeutic index compared to native IL-12 agents"
  
• Abstract 697, "Tumor-targeted CD28 costimulatory bispecific antibodies enhance T cell activation in solid tumors"
  
• Abstract 714, "PD-1 x TGF?R2 bispecifics selectively block TGF?R2 on PD1-positive T cells, promote T cell activation, and elicit an anti-tumor response in solid tumors"

Posters will be available to registrants of the SITC Annual Meeting in the Virtual Poster Hall between 9:00 a.m. and 5:00 p.m. ET on each day from November 11-14, 2020. Posters will be archived under "Events & Presentations" in the Investors section of the Company's website located at www.xencor.com.

About XmAb^®20717

XmAb20717 is a bispecific antibody that simultaneously targets immune checkpoint receptors PD-1 and CTLA-4 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 (Fc?R) binding, with the intent to prevent activation and/or depletion of T cells via engagement by Fc?R-expressing cells. XmAb20717 is being evaluated in an ongoing Phase 1 study, which is enrolling patients with advanced solid tumors to expansion cohorts and additional dose-escalation cohorts.

About Xencor, Inc.

Xencor is a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of cancer and autoimmune diseases. Currently, 18 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 any expectations relating to current or 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.