On June 25, 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, reported that the Safety Monitoring Committee (SMC) recommended dose escalation in its Phase 1b clinical trial designed to evaluate the safety and tolerability of intratumoral (IT) PH-762 in the treatment of Stages 1, 2, and 4 cutaneous squamous cell carcinoma (cSCC), Stage 4 melanoma, and Stage 4 Merkel cell carcinoma (Press release, Phio Pharmaceuticals, JUN 25, 2025, View Source [SID1234654114]).
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Five patients were enrolled in the fourth cohort of the Phase 1b clinical trial (NCT 06014086). Four of the enrolled patients were diagnosed with cSCC and one patient with Merkel cell carcinoma. As with the previous three cohorts, injections were well-tolerated and there were no dose-limiting toxicities, serious adverse events, or clinically relevant treatment-emergent adverse reactions reported.
Pathology results related to the efficacy of PH-762 in the fourth cohort will be forthcoming.
"We are encouraged by the continuing safety profile of PH-762 having now progressed through four escalating dose concentrations, and we anticipate that IT administration of the highest dose concentration of PH-762 in cohort 5 will result in a similar safety profile," said Mary Spellman, MD, Phio’s acting Chief Medical Officer.
To date, a total of 15 patients with cutaneous carcinomas have been treated with PH-762 in Cohorts 1 through 4. These cohorts included 13 patients with cSCC, one patient with metastatic melanoma, and one patient with Merkel cell carcinoma.
Pathological response at Day 36 (planned tumor excision) in the previous three cohorts demonstrated complete response (100% tumor clearance) in 4 of 9 patients with cSCC. One cSCC patient had a near complete response (>90% clearance) and one cSCC patient had a partial response (>50% clearance). The other three patients with cSCC and one patient with metastatic melanoma had a pathologic non-response (< 50% clearance). No patients exhibited clinical progression of disease. Patients with a pathologic complete response (100% tumor clearance) may have visual signs of residual scar or subdermal inflammation prior to resection.
Phio expects to complete enrollment in the expected final cohort in this trial in the third quarter of 2025.
"The continuing favorable safety profile of PH-762 through the fourth cohort provides promise of a well-tolerated treatment for skin cancer," said Robert Bitterman, CEO and Chairman of Phio Pharmaceuticals.