Phio Pharmaceuticals Completes Enrollment In Phase 1b Trial Of PH-762 siRNA Cancer Therapy

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 the completion of enrollment in its ongoing Phase 1b clinical trial of INTASYL siRNA PH-762. In connection with completing enrollment, Phio continues to treat additional patients in the fifth cohort at the highest dose concentration of PH-762. Pathology results for these patients are expected in Q1 2026.

PH-762 is a potent silencer of the PD-1 gene implicated in various forms of skin cancer.

The Phase 1b clinical trial is designed to evaluate the safety and tolerability of neoadjuvant use of intratumoral PH-762 in Stages 1, 2 and 4 cutaneous squamous cell carcinoma (cSCC), Stage 4 melanoma, and Stage 4 Merkel cell carcinoma. Per the trial's protocol, patients receive four injections of PH-762 at weekly intervals and pathologic response is assessed on day 36 after the initial injection of PH-762 (NCT# 06014086).

Thus far, 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 have 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.