- Xilio Therapeutics (XLO, Financial) announces a 26% objective response rate for vilastobart in metastatic MSS CRC patients without liver metastases.
- The combination of vilastobart and atezolizumab shows deep and durable responses lasting up to 37 weeks.
- Xilio plans to enroll patients at a higher dose and report additional data in H1 2026.
Xilio Therapeutics (XLO), a clinical-stage biotechnology company, has reported promising Phase 2 data on vilastobart, a tumor-activated anti-CTLA-4, when used in combination with atezolizumab in patients with metastatic microsatellite stable colorectal cancer (MSS CRC) who do not have liver metastases. The trial results, presented at the 2025 ASCO Annual Meeting, revealed a preliminary 26% objective response rate (ORR), showcasing potential progress in an area with significant treatment challenges.
The trial involved 44 patients with a median age of 55, with 80% having undergone three or more prior cancer therapies. Among these, seven partial responses were recorded, with six confirmed, demonstrating the drug combination's effectiveness and the durability of the responses, which lasted up to 37 weeks. The treatment also resulted in substantial reductions in tumor biomarkers and improvements in clinical symptoms, which underline its potential impact on MSS CRC.
Vilastobart exhibited a favorable safety profile, with only 7% of patients experiencing colitis and just 5% discontinuing treatment due to adverse events. These outcomes underscore vilastobart's tumor-activated mechanism, which efficiently limits systemic immune-related toxicities while maintaining its anti-tumor efficacy.
Xilio is currently enrolling patients at an increased dose level of 150 mg every six weeks and anticipates new data from the higher dose cohort in early 2026. The company is also exploring partnership opportunities to further develop the vilastobart program and enhance its potential in the immuno-oncology field.
