Phio Pharmaceuticals (NASDAQ: PHIO) Announces Promising Results of Second Cohort from Its Ongoing Clinical Study of PH-762

Pathologic Complete Response reported for 2 patients with cutaneous Squamous Cell Carcinoma

Marlborough, Massachusetts– January 13, 2025) – Phio Pharmaceuticals Corp. (NASDAQ: PHIO) is a clinical-stage biotechnology company developing therapeutics that use its INTASYL^® siRNA gene silencing technology designed to make the body’s immune cells more effective in killing cancer cells. Phio today announced pathologic responses for patients enrolled in the 2nd cohort, which includes 2 patients with a complete response or 100% tumor clearance.

Phio’s ongoing Phase 1b clinical study (NCT 06014086) is designed to evaluate the safety and tolerability of neoadjuvant use of intratumoral PH-762 in Stages 1, 2 and 4 cutaneous squamous cell carcinoma, Stage 4 melanoma and Stage 4 Merkel cell carcinoma.

Of the patients enrolled to date, 6 patients were diagnosed with cutaneous squamous cell carcinoma and 1 patient was diagnosed with metastatic melanoma. At Day 36 (tumor excision), while patients in the first cohort had stable disease, results are now available for the 4 patients who completed treatment in the 2^nd cohort:

• Complete response (100% tumor clearance) is reported for 2 patients with cutaneous squamous cell carcinoma. Partial response (90% tumor clearance) is reported for 1 patient with cutaneous squamous cell carcinoma and 1 patient had stable disease, having not progressed.

There have been no dose-limiting toxicities, or clinically relevant treatment-emergent adverse events in the patients receiving intratumoral PH-762. The intratumoral injections have been well tolerated.

“We are pleased and encouraged by the profound tumor response in the second dose cohort, coupled with reassuring safety data,” said Mary Spellman MD, Phio’s acting Chief Medical Officer. “We look forward to continued enrollment which will permit assessment of higher dose concentrations of PH-762.”

“These positive results in the early stages of dose escalation offer promise for our vision, ‘striving for a cancer free future’ using INTASYL technology” said Robert Bitterman, CEO of Phio Pharmaceuticals.

About Phio Pharmaceuticals Corp.

Phio Pharmaceuticals Corp. (NASDAQ: PHIO) is a clinical-stage biotechnology company advancing its proprietary INTASYL siRNA gene silencing technology to eliminate cancer. INTASYL can target and silence virtually any gene with high degree of specificity across a wide range of cell types and tissues. INTASYL is designed to enhance the ability of immune cells to more effectively kill tumor cells. INTASYL has also demonstrated enhancement adoptive cell therapy. Notably, INTASYL is a self-delivering RNAi technology focused on immuno-oncology therapeutics without the need for formulation enhancements or manipulations to reach its target.