Phio Pharmaceuticals (NASDAQ:PHIO) reported that its experimental gene-silencing therapy cleared tumors in the majority of patients during a mid-stage study, marking a significant win for its proprietary INTASYL technology.
The company announced results from its Phase 1b trial of PH-762, an intratumoral injection designed to "silence" the PD-1 gene.
Across 20 patients with cutaneous squamous cell carcinoma (cSCC), the treatment achieved a 70% overall pathologic response rate.
Notably, 10 of those patients saw 100% tumor clearance, while others showed near-complete or partial reductions.
The drug also showed activity in a patient with metastatic Merkel cell carcinoma, further broadening its potential application.
Equally important for the clinical-stage firm was the safety profile; despite escalating the drug concentration 20-fold across five patient cohorts, Phio reported no dose-limiting toxicities or serious adverse events.
The results suggest PH-762 could eventually offer a non-surgical alternative for skin cancer patients.
Phio expects to report extended safety data in the second quarter of 2026 as it moves toward a pivotal study.