-- Engineered IL2-Fc Cytokine is Well-tolerated and Selectively Expands Regulatory T Cells --

Xencor, Inc. (NASDAQ:XNCR), a clinical-stage biopharmaceutical company developing engineered antibodies and cytokines for the treatment of patients with cancer and autoimmune diseases, today announced the presentation of results from its Phase 1a single-ascending dose study of XmAb^®564 in healthy volunteers. XmAb564 is a potency-tuned IL-2-Fc fusion protein, engineered to selectively activate and expand regulatory T cells (Tregs) for the potential treatment of patients with autoimmune diseases. Results will be presented in a poster titled “XmAb564, a Novel Potency-Tuned IL-2 Fc-Fusion Protein Selectively Expands Regulatory T Cells: Results from a Single Ascending-Dose Study in Healthy Adult Volunteers” at the European Congress of Rheumatology (EULAR) being held May 31 to June 3 in Milan, Italy.

“We have previously presented that a single dose of XmAb564 was well tolerated in healthy volunteers and generates durable, dose-dependent and selective expansion of regulatory T cells. The magnitude and duration of Treg induction may be superior to other IL-2 candidates evaluated clinically and could potentially support extended multi-week dosing intervals,” said Bassil Dahiyat, Ph.D., president and chief executive officer at Xencor. “We continue to enroll patients into the Phase 1b, multiple-ascending dose study in patients with atopic dermatitis and psoriasis, and we anticipate completing dose escalation in psoriasis cohorts in early 2024.”

The poster is now available under "Events & Presentations" in the Investors section of the Company's website located at www.xencor.com.

About XmAb^®564 (IL-2 Fc)

XmAb^®564 is a wholly owned, monovalent, potency-tuned IL-2-Fc fusion protein, engineered to selectively activate and expand Tregs for the potential treatment of patients with autoimmune diseases. XmAb564 is engineered with reduced binding affinity for IL-2’s beta receptor (IL-2Rβ, CD122) and increased binding affinity for its alpha receptor (IL-2Rα, CD25). Xencor’s XmAb Bispecific Fc Domain additionally provides a stable protein scaffold and improves XmAb564’s pharmacologic properties, and Xencor’s Xtend™ Fc technology enhances its circulating half-life.

As presented in November 2022, the Phase 1a study of XmAb564 demonstrated that a single dose of XmAb564 in healthy volunteers was well-tolerated, promoted the selective and sustained expansion of Tregs and exhibited a favorable pharmacokinetic profile.

Xencor is conducting a randomized, double-blind, placebo-controlled, multiple-ascending dose Phase 1b clinical study to evaluate the safety and tolerability of XmAb564, administered subcutaneously in patients with atopic dermatitis and psoriasis.

About Xencor

Xencor is a clinical-stage biopharmaceutical company developing engineered antibodies and cytokines for the treatment of patients with cancer and autoimmune diseases. More than 20 candidates engineered with Xencor's XmAb^® technology are in clinical development, and three XmAb medicines are marketed by partners. Xencor's XmAb engineering technology enables small changes to a proteins structure that result in new mechanisms of therapeutic action. For more information, please visit www.xencor.com.

Forward-Looking Statements

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