Xilio Therapeutics announced initial positive Phase 2 data for vilastobart (XTX101), a tumor-activated anti-CTLA-4 antibody, combined with atezolizumab (Tecentriq®) in patients with metastatic microsatellite stable colorectal cancer (MSS CRC). The combination showed a 27% objective response rate in heavily pre-treated patients without liver metastases, accompanied by biomarker and symptom improvements. Data also suggested a favorable safety and tolerability profile.
This news holds particular promise for MSS CRC patients, a population with limited treatment options who haven’t benefited significantly from existing immunotherapies, including PD-(L)1 inhibitors used alone. The observed responses and manageable side effects suggest this combination could address a substantial unmet need in this challenging cancer type.
In the trial, 40 heavily pre-treated patients received vilastobart and atezolizumab. Among the 11 evaluable patients without liver metastases, three achieved partial responses. These responses correlated with decreases in carcinoembryonic antigen (CEA) and circulating tumor DNA (ctDNA), and improvements in clinical symptoms. The combination’s safety profile appears encouraging, with a low incidence of immune-related adverse events, notably a 5% rate of colitis.
These early results lay the foundation for further exploration of vilastobart in MSS CRC and potentially other “cold” tumors resistant to traditional immunotherapy. Xilio plans to release updated Phase 2 data mid-2025 and will explore partnerships to expand development of this promising combination therapy.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
