Phio Pharmaceuticals Reports Positive Pathology Results for PH-762 in Skin Cancer Trial

Phio Pharmaceuticals Corp. (NASDAQ: PHIO) announced encouraging pathology results from the fourth cohort of its ongoing Phase 1b clinical trial evaluating PH-762, the company’s lead siRNA-based immunotherapy for advanced skin cancers.

Among the five patients enrolled, one with cutaneous squamous cell carcinoma (cSCC) achieved a complete pathologic response, showing 100% tumor clearance, while another patient with stage 4 metastatic Merkel cell carcinoma demonstrated a partial pathologic response with more than 50% tumor reduction. Two other cSCC patients showed less than 50% clearance (classified as non-responses), and pathology results for the fifth patient are still pending.

Importantly, the trial reported no dose-limiting toxicities or serious adverse events, underscoring the favorable safety profile of PH-762. The investigational therapy is being administered intratumorally and is designed using Phio’s proprietary INTASYL® gene-silencing platform, which enhances the body’s immune response against tumor cells by silencing key gene targets within the tumor microenvironment.

Strategic and Clinical Significance

The complete tumor clearance in one cSCC patient and meaningful partial response in a metastatic case suggest early signs of clinical activity in difficult-to-treat cancers. These outcomes reinforce the potential of PH-762 as a non-surgical alternative in dermatologic oncology, particularly for patients who are ineligible for surgery or resistant to current immunotherapies.

For investors, the safety and early efficacy signals represent a key de-risking milestone as Phio advances through the dose-escalation phase. With no major safety concerns identified, the company remains well-positioned to move toward later-stage development and potential partnering opportunities if data remain consistent in subsequent cohorts.

Next Steps

Phio expects additional results from the fifth patient and further cohorts in the coming months. The data will help inform optimal dosing and guide trial expansion into melanoma and other advanced skin cancers.

Investor Outlook

Early signs of efficacy coupled with a strong safety profile are strengthening Phio’s value proposition in the siRNA immunotherapy space, a growing segment of precision oncology. As the trial progresses, investors should watch for:

• Completion of the fifth cohort and full pathology dataset
• Preclinical updates in melanoma and Merkel cell carcinoma models
• Any strategic collaborations or licensing activity around the INTASYL® platform

If PH-762 continues to demonstrate tumor regression and safety consistency, it could emerge as a promising new entrant in the next generation of RNA-based cancer immunotherapies.