On May 7, 2025 Phio Pharmaceuticals Corp. (Nasdaq: PHIO) reported it is a clinical-stage siRNA biopharmaceutical company developing therapeutics using its proprietary INTASYL gene silencing technology to eliminate cancer (Press release, Phio Pharmaceuticals, MAY 7, 2025, View Source [SID1234652645]). Phio reported that a complete pathologic response (100% tumor clearance) has been reported for 2 of 3 patients with cutaneous squamous cell carcinoma (cSCC) treated in the third dose cohort. The third patient was reported as having a pathologic non-response (<50% tumor clearance).

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"These positive outcomes 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, President and CEO of Phio Pharmaceuticals.

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 10 patients with cutaneous carcinomas have been treated in Cohorts 1, 2 and 3. These cohorts included 9 patients with cSCC and 1 patient with metastatic melanoma. At day 36 (planned tumor excision), of the 9 patients with cSCC, 4 patients had a pathologic complete response (100% tumor clearance). One patient had a near complete response (>90% clearance) and 1 patient had a partial response (>50% clearance). The other 3 cSCC and one metastatic melanoma patient had a pathologic non-response (< 50% clearance). Patients with pathologic complete response (100% tumor clearance) may have visual signs of residual scar or subdermal inflammation prior to resection. No patients, 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. The fourth cohort is currently enrolling patients; Phio expects to complete enrollment in the trial in the third quarter of 2025.

"The continued positive pathologic responses in this clinical trial of intratumoral PH-762 for cutaneous carcinoma increases our understanding of the potential therapeutic benefit for this immunotherapy. The safety profile supports ongoing dose escalation," said Mary Spellman, MD, Phio’s acting Chief Medical Officer.