Xilio Therapeutics (XLO) Study Update summary

Platform and Mechanism Overview

• Vilastobart (XTX101) is a tumor-activated, Fc-enhanced anti-CTLA-4 antibody designed for selective activation by dysregulated MMPs in solid tumors, aiming to minimize systemic toxicity and deplete regulatory T cells in the tumor microenvironment.

• The pipeline includes Vilastobart in phase II for MSS-CRC, XTX-301 (tumor-activated IL-12) in phase I, and preclinical bispecific and cell engager programs.

• The program is part of a co-funded clinical collaboration with Roche and is advancing through Phase 1C and Phase 2 trials.

Unmet Need in MSS Colorectal Cancer

• Colorectal cancer is the second leading cause of cancer death in the US and the leading cause in men under 50.

• Most metastatic CRC patients are microsatellite stable (MSS) and lack actionable mutations, with current therapies offering minimal survival benefit and low response rates.

• Immunotherapy has shown little efficacy in MSS-CRC, especially in patients with liver metastases.

Study Design and Patient Population

• Phase 1C enrolled 17 heavily pre-treated patients with advanced solid tumors, including 12 with MSS CRC, median age 69, most with three or more prior therapies.

• Vilastobart was administered at 75, 100, or 150 mg Q6W with atezolizumab 1200 mg Q3W; enrollment is ongoing at 150 mg.

• Seven patients remained on treatment at data cutoff.