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).

XTX101 is currently being evaluated in an ongoing Phase 1 clinical trial in patients with advanced solid tumors.  XTX101 has completed monotherapy dose escalation (Phase 1A) and is being evaluated at the recommended Phase 2 dose and schedule of 150 mg once every six weeks (RP2D) in monotherapy dose expansion (Phase 1B). Xilio also plans to evaluate XTX101 in combination with atezolizumab in patients with microsatellite stable colorectal cancer (MSS CRC) in a Phase 1/2 clinical trial. 

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)

As part of the Phase 1/2 clinical trial, Xilio plans to evaluate XTX101 in combination with atezolizumab. The Phase 1 portion is designed to assess the safety and tolerability of XTX101 in combination with atezolizumab in dose escalation in patients with advanced solid tumors, and the planned Phase 2 portion is designed to evaluate the safety and efficacy of the combination in patients with microsatellite stable colorectal cancer (MSS CRC).