Phio Pharmaceuticals' Nonclinical Protocol For PH-762 Accepted By FDA; Toxicology Study Set To Begin In Q1 2026 Following Phase 1b Skin Cancer Results

Nonclinical protocol study design accepted by FDA

Study to commence in First Quarter 2026

King of Prussia, Pennsylvania--(Newsfile Corp. - December 23, 2025) - Phio Pharmaceuticals Corp. (NASDAQ:PHIO) is a clinical-stage siRNA biopharmaceutical company developing therapeutics using its proprietary INTASYL® gene silencing technology to eliminate cancer. Phio announced today that it has taken a major step forward in its drug development program for PH-762. The company will begin a toxicology study, which is required by the FDA prior to commencing a human pivotal trial. Concurrently, initiatives are continuing to advance the delivery of commercially viable drug product in 2026 that meets FDA's current Good Manufacturing Practices. A portion of the net proceeds from Phio's recent financing is being directed to these two major initiatives.

Recently, positive interim safety and efficacy results were reported in the on-going Phase 1b dose escalation clinical trial with the INTASYL compound PH-762 for the treatment of skin cancer. To date, a total of 18 patients with cutaneous carcinomas have completed treatment across five dose escalating cohorts in the Phase 1b trial. The cumulative pathologic response in 16 patients with cSCC include six with a complete response (100% clearance), two with a near complete response (> 90% clearance) and two with a partial response (> 50% clearance). A single patient with metastatic Merkel cell carcinoma had a partial response (> 50% clearance). Six patients with cSCC and one patient with metastatic melanoma had a pathologic non-response (< 50% clearance). No patients in the study, however, exhibited clinical progression of disease. To date, there were no dose-limiting toxicities or clinically relevant treatment-emergent adverse effects in the patients receiving intratumoral PH-762 in this trial. Moreover, PH-762 has been well tolerated in all enrolled patients in each escalating dose cohort.