Phio Submits FDA Briefing Package for Phase 2b Skin Cancer Trial

Phio Pharmaceuticals has submitted a briefing package and meeting request to the U.S. Food and Drug Administration for its lead skin cancer candidate, PH-762, following the completion of its Phase 1b clinical study.

The regulatory submission marks a transition for the biotechnology company as it prepares for a planned Phase 2b neoadjuvant trial in cutaneous squamous cell carcinoma. In the public markets, Phio Pharmaceuticals Corp. (PHIO) stock traded at $0.99, down 2.8% from its previous close, according to Finnhub market data.

"Delivering this comprehensive briefing package to the FDA is a key achievement for the PH-762 program and an important step toward unlocking its clinical potential in cutaneous squamous cell carcinoma," said Robert J. Bitterman, President and CEO of Phio Pharmaceuticals, in a statement.

Clinical Package and Regulatory Scope

The briefing package submitted to the FDA outlines the nonclinical development program, integrated clinical pharmacology data, and findings from the completed Phase 1b study. It also details the design for the upcoming Phase 2b neoadjuvant clinical study.

The therapy under evaluation, PH-762, is an INTASYL compound engineered to silence the PD-1 gene, which is implicated in various forms of skin cancer. The compound was previously evaluated in a Phase 1b trial (NCT# 06014086) targeting cutaneous squamous cell carcinoma, melanoma, and Merkel cell carcinoma.

Mechanism of INTASYL Compounds

INTASYL technology is Phio's proprietary self-delivering RNA interference platform. Unlike traditional RNAi therapeutics that require specialized delivery vehicles or viral vectors, INTASYL compounds are chemically modified to enter cells independently.

The mechanism works by targeting messenger RNA to silence specific genes, in this case the PD-1 gene, before proteins can be expressed. By silencing PD-1 directly within the tumor microenvironment, the localized treatment aims to reactivate immune responses against cancer cells while minimizing systemic toxicities associated with conventional systemic immunotherapies.

Manufacturing Timelines and Next Steps

Alongside the regulatory review process, Phio is preparing to manufacture clinical supplies for the next planned study. These supplies are expected to be available in the first quarter of 2027.

This manufacturing timeline coincides with the anticipated completion of the dosing phase for the company's ongoing nonclinical toxicology study, which supports the broader clinical development plan for the cutaneous squamous cell carcinoma program.