Xencor Doses First Subject in Phase 1 Study of XmAb564, an Engineered IL-2 Cytokine in Development for Autoimmune Diseases

Xencor, Inc. (NASDAQ: XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies and cytokines for the treatment of cancer and autoimmune diseases, today announced that the first subject has been dosed in a randomized, double-blind, placebo-controlled Phase 1 clinical study of XmAb564, an engineered IL-2-Fc cytokine in development as a potential treatment for patients with autoimmune diseases. The study will evaluate the safety and tolerability of XmAb564, administered subcutaneously in healthy adult volunteers.

Interleukin-2 (IL-2) is a signaling protein that activates and expands certain immune cell populations, including regulatory T cells (Tregs). Tregs prevent autoimmunity by suppressing other immune cells from attacking normal tissue; however, in many autoimmune diseases, Tregs become dysregulated. An existing approach to restore normal immune activity and improve outcomes for patients has been to activate Tregs with IL-2 provided therapeutically at low doses. These regimens, however, suffer from a narrow therapeutic window, because IL-2 is a highly potent molecule that also activates the immune cell populations that Tregs are intended to suppress.

"We engineered XmAb564 to selectively activate and expand regulatory T cells over other immune cells by tuning the binding affinities for both IL-2's alpha and beta receptors. Our modular XmAb heterodimeric Fc domain additionally provides XmAb564 with a stable protein scaffold and improves its pharmacologic properties, and we further enhanced circulating half-life by adding our Xtend Fc technology," said John Desjarlais, Ph.D., senior vice president and chief scientific officer at Xencor. "In preclinical studies, XmAb564 was well tolerated and promoted the selective and sustained proliferation of Tregs over effector T cells and natural killer (NK) cells."

"The goal of an IL-2 therapy for autoimmune disease is to provide sustained low-intensity activation of Tregs while avoiding the pro-inflammatory systemic activation of effector T cells," said Allen Yang, M.D., Ph.D., senior vice president and chief medical officer at Xencor. "An IL-2 therapy that is selective for Tregs, with an expanded therapeutic window compared to other IL-2 approaches, would have broad potential across many different autoimmune diseases."