On July 25, 2025 Phio Pharmaceuticals Corp. (NASDAQ: PHIO) a clinical-stage siRNA biopharmaceutical company developing therapeutics using its proprietary INTASYL gene silencing technology to eliminate cancer, reported that pathologic results are available for four of the five patients treated in the fourth cohort (Press release, Agenus, JUL 25, 2025, View Source [SID1234654551]). A complete pathologic response (100% tumor clearance) has been reported for one patient with cutaneous squamous cell carcinoma (cSCC). One patient with metastatic Merkel cell carcinoma was reported as a partial response (> 50% clearance). Two patients with cSCC were reported as having a pathologic non-response (<50% tumor clearance). Pathologic results for the remaining patient with cSCC are still pending.
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Phio’s ongoing Phase 1b dose escalation clinical trial (NCT 06014086) is designed to evaluate the safety and tolerability of neoadjuvant use of intratumoral PH-762 in Stages 1, 2 and 4 cSCC, Stage 4 melanoma, and Stage 4 Merkel cell carcinoma. To date, a total of 15 patients with cutaneous carcinomas have been treated across the four cohorts. 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. No patients exhibited clinical progression of disease.
The cumulative pathologic response in 13 patients with cSCC include five complete response (100% clearance), one patient with a near complete response (>90% clearance) and one with a partial response (>50% clearance) and six patients with a pathologic non-response (< 50% clearance).
The one Merkel cell carcinoma patient with stage 4 metastatic disease had a partial response (>50% clearance). The melanoma patient was a non-responder (<50% clearance).
Phio is now enrolling what is expected to be the 5th and final cohort in the Phase 1b study.
"The positive safety and efficacy outcomes through the fourth cohort continue to indicate that PH-762 may present a viable non-surgical alternative in this large and continually expanding skin cancer market," said Robert Bitterman, CEO and Chairman of Phio Pharmaceuticals.