XTX101 is an investigational Fc-enhanced, tumor-activated anti-CTLA-4 designed to block CTLA-4 and deplete regulatory T cells when activated (unmasked) in the tumor microenvironment (TME).

About CTLA-4

Checkpoint inhibition is one of the foundational mechanisms of immunotherapy (I-O) and occurs when a drug blocks checkpoint and partner proteins from binding and enables T cells to kill cancer cells. CTLA-4 is a common checkpoint protein that plays a critical role in limiting the ability of T cells to recognize cancer cells. CTLA-4 is also a key marker protein present on immune suppressive regulatory T cells (TREGs) that limits the immune system’s ability to fight cancer.

About the Phase 1/2 Clinical Trial for XTX101 (Monotherapy and Combination)

XTX101 is currently being evaluated in combination with atezolizumab (Tecentriq®) in a Phase 1/2 multicenter, open-label clinical trial in patients with advanced solid tumors. The safety and tolerability of the combination is currently being evaluated in Phase 1 dose escalation. Subject to the results of the Phase 1 combination dose escalation, Xilio plans to evaluate the safety and efficacy of the combination in a Phase 2 clinical trial in patients with microsatellite stable colorectal cancer (MSSCRC).