Xilio reports results from ongoing Phase 2 clinical trial of vilastobart

Xilio Therapeutics (XLO) announced initial data from its ongoing Phase 2 clinical trial evaluating vilastobart, or XTX101, a tumor-activated, Fc-enhanced, high affinity binding anti-CTLA-4, in combination with atezolizumab in patients with metastatic microsatellite stable colorectal cancer, or MSS CRC. The data will be presented in a poster session at the American Society of Clinical Oncology 2025 Gastrointestinal Cancer Symposium being held January 23-25, in San Francisco. Data from Phase 2 Trial for Vilastobart, or XTX101, a Tumor-Activated Anti-CTLA-4, in Combination with Atezolizumab in Patients with Metastatic MSS CRC. As of a data cutoff date of January 13, 40 patients with metastatic MSS CRC had been treated with the combination of vilastobart at a dose of 100 mg once every six weeks, or Q6W, and atezolizumab at 1200 mg once every three weeks, or Q3W. The median age was 55 years and patients were heavily pre-treated, with 70% of patients having previously received three or more prior lines of anti-cancer therapy. In patients without liver metastases, the preliminary objective response rate was 27% with three partial responses, including two confirmed PRs. Responses were accompanied by decreases in levels of carcinoembryonic antigen, or CEA, and circulating tumor DNA as well as improvement in clinical symptoms. PR with a 47% decrease in the sum of diameters of target lesions at 13 weeks accompanied by a decrease in levels of the serum tumor marker CEA, a multi-log fold decrease in levels of ctDNA and improvement of clinical symptoms, such as cough. CEA is a serum biomarker that is often elevated in many malignancies, including colorectal cancer, and ctDNA is a biomarker found in the bloodstream of patients with cancer.