Phio Pharmaceuticals Announces Significant Step Forward In Its Drug Development Program For PH-762

• Nonclinical protocol study design accepted by FDA
• Study to commence in First Quarter 2026

Phio Pharmaceuticals Corp. Is a clinical-stage siRNA biopharmaceutical company developing therapeutics using its proprietary INTASYL gene silencing technology to eliminate cancer. Phio announced today that it has taken a major step forward in its drug development program for PH-762. The company will begin a toxicology study, which is required by the FDA prior to commencing a human pivotal trial. Concurrently, initiatives are continuing to advance the delivery of commercially viable drug product in 2026 that meets FDA’s current Good Manufacturing Practices. A portion of the net proceeds from Phio’s recent financing is being directed to these two major initiatives.

Recently, positive interim safety and efficacy results were reported in the on-going Phase 1b dose escalation clinical trial with the INTASYL compound PH-762 for the treatment of skin cancer. To date, a total of 18 patients with cutaneous carcinomas have completed treatment across five dose escalating cohorts in the Phase 1b trial. The cumulative pathologic response in 16 patients with cSCC include six with a complete response (100% clearance), two with a near complete response (> 90% clearance) and two with a partial response (> 50% clearance). A single patient with metastatic Merkel cell carcinoma had a partial response (> 50% clearance). Six patients with cSCC and one patient with metastatic melanoma had a pathologic non-response (< 50% clearance). No patients in the study, 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 conduct of this nonclinical study is a very significant step in progressing the drug development pathway of PH-762 toward an NDA approval. Phio’s communication with FDA is essential in advancing our development strategy for PH-762,” stated Robert Bitterman, CEO and Chairman of Phio Pharmaceuticals. “In addition, the initiative to deliver commercially viable drug product from our US supplier is on target for later in 2026. This is another critical advancement in the drug development program of PH-762.”

About Phio Pharmaceuticals Corp.
Phio Pharmaceuticals Corp. (Nasdaq: PHIO) is a clinical-stage siRNA biopharmaceutical company advancing its INTASYL gene silencing technology focused on immuno-oncology therapeutics. Phio’s INTASYL compounds are designed to enhance the body’s immune cells to more effectively kill cancer cells. Phio’s lead clinical program is an INTASYL compound, PH-762, that silences the PD-1 gene implicated in various forms of skin cancer. The ongoing Phase 1b trial (NCT# 06014086) is evaluating PH-762 for the treatment of cutaneous squamous cell carcinoma, melanoma and Merkel cell carcinoma. PH-762 is a potential non-surgical treatment for skin cancers.

For additional information, visit the Company’s website, www.phiopharma.com.