OXFORD, UK – 11 November, 2025
- First-in-human RAISIC-1 trial demonstrates favourable safety and tolerability profile across four dose levels with zero dose-limiting toxicities (DLTs)
- Early clinical benefit achieved, with four patients experiencing stable disease and two remaining on treatment for over three months
- Compelling translational data from whole blood transcriptomics and plasma proteomics confirm successful stimulation of interferon-signalling pathways
- Pathios positions to open monotherapy and combination clinical expansion cohorts in 2026
Pathios announced the first public disclosure of clinical data from its ongoing Phase 1 RAISIC-1 trial in a scientific poster presentation at the Society for Immunotherapy of Cancer (SITC) 39th Annual Meeting November 5-9 2025 in National Harbor, Maryland. The presentation marks a major clinical milestone for Pathios, which is the first company globally to successfully target and antagonise the GPR65 receptor in humans.
Key Clinical and Translational Data from SITC 2025
The RAISIC-1 trial is a first-in-human study evaluating PTT-4256, a potent and highly selective oral GPR65 antagonist, in patients with advanced solid tumors. This first look at the emerging clinical data encompasses observations since the first patient was dosed in November 2024:
- Optimised Safety and Tolerability: Across four escalating dose levels, PTT-4256 was well-tolerated by patients. The safety profile remains highly encouraging, with no dose-limiting toxicities (DLTs) or notable safety concerns reported to date.
- Encouraging Signs of Clinical Benefit: Early evidence of anti-tumor activity was observed in heavily pre-treated populations. Four patients achieved documented clinical benefit via stable disease (SD), with two of those patients remaining on active treatment for more than three months.
- Compelling Proof of Mechanism: High-quality translational biomarker data provided clear evidence of target engagement and downstream immune modulation. Analyses of whole blood transcriptomics and plasma proteomics demonstrated that oral administration of PTT-4256 successfully stimulates crucial interferon-signalling pathways, turning an immunosuppressive environment into an immunologically active one.
Looking Ahead: Clinical Expansion in 2026
Based on the strength of these initial safety, PK/PD, and efficacy signals, the company is actively preparing to transition the RAISIC-1 trial into its next phase, with plans to open both monotherapy and combination expansion cohorts in 2026.
The scientific poster presented at the conference is available on the Pathios website here.