8-K: Phio PH-762 Skin Cancer Trial Shows Positive Safety & Response

Phio Pharmaceuticals announced positive safety and pathological response results from its Phase 1b clinical trial of PH-762 for skin cancer, with high response rates in the final dose cohort.

Summary

• The Safety Monitoring Committee (SMC) concluded its planned safety review for PH-762 in Phio's Phase 1b clinical trial, reporting no dose-limiting toxicities or serious adverse events for any of the 22 enrolled patients.
• PH-762 was evaluated across five dose-escalating cohorts, increasing drug concentration 20-fold from the first to the fifth and final cohort.
• The maximum dose concentration in the final cohort yielded an 85% pathological response (6 of 7 patients), with 4 of these 6 responders achieving complete response (100% tumor clearance).
• Revised data supports an overall response rate of 65% for squamous cell carcinomas (cSCC) among the 20 cSCC patients, with 13 classified as pathologic responders.
• Among cSCC patients, 9 achieved complete response (100% clearance), 2 had major/near clear response (>90% clearance), and 2 had partial response (>50% clearance).
• A single patient with metastatic Merkel cell carcinoma had a partial response.
• Chemistry, Manufacturing and Controls (CMC) development for drug substance material (API) is expected to have material available in March 2026 for a non-human primate study.
• Manufacturing of cGMP material is expected to commence in the second half of 2026.

Sentiment

Score: 8

Explanation: StockSavvy.ai views this as a highly positive update, driven by strong safety data and encouraging early efficacy signals, particularly the high pathological response rates at the maximum dose, which de-risks the program significantly for future development.

Positives

• The Safety Monitoring Committee (SMC) concluded a positive safety review for PH-762, reporting no dose-limiting toxicities or serious adverse events across all 5 dose-escalation cohorts and 22 patients.
• The highest dose concentration of PH-762 in the final cohort achieved an 85% pathological response (6 out of 7 patients).
• 4 out of 6 responders in the final cohort showed complete response (100% tumor clearance).
• An overall response rate of 65% was observed for squamous cell carcinomas (cSCC), with 9 out of 20 cSCC patients achieving complete response.
• Results support continued evaluation of the highest dose concentration of PH-762 in future clinical trials, indicating strong potential for the lead candidate.
• Expected availability of drug substance material for non-human primate studies by March 2026 and commencement of cGMP material manufacturing in the second half of 2026 demonstrate progress in development timelines.

Negatives

• 7 cSCC patients and one melanoma patient had responses of less than 50% tumor clearance.

Risks

• Actual results may differ materially from forward-looking statements due to factors such as results from preclinical and clinical activities, the ability to execute on business strategies, the timing or likelihood of regulatory filings and approvals.
• The company's ability to manufacture and supply product candidates for clinical activities and commercial use if approved, and the scope of intellectual property protection, are important factors.
• The ability to obtain future financing, as well as market and other conditions, could impact actual results.
• Risks identified in the company's Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q under the caption "Risk Factors" are applicable.

Future Outlook

Phio Pharmaceuticals targets an FDA submission in the second quarter of 2026 to propose and seek guidance for the next clinical study design for PH-762. Chemistry, Manufacturing and Controls (CMC) development expects material for non-human primate studies by March 2026, with cGMP material manufacturing commencing in the second half of 2026. The company believes its INTASYL siRNA gene silencing technology has the potential to make immune cells more effective in killing cancer cells and that PH-762 could be a viable non-surgical alternative for skin cancer.

Management Comments

• "These results support continued evaluation of this highest dose concentration of PH-762 in the next clinical trial."
• "Reported pathological response coupled with a favorable safety-tolerability profile is clinically meaningful."

Industry Context

StockSavvy.ai notes that positive Phase 1b safety and early efficacy data, particularly with high response rates at maximum dosage, are crucial milestones for clinical-stage biopharmaceutical companies. In the competitive immuno-oncology space, a favorable safety profile combined with promising pathological responses for a novel siRNA therapeutic like PH-762 could differentiate Phio Pharmaceuticals, especially as it targets a non-surgical treatment for skin cancers.

Comparison to Industry Standards

• The 85% pathological response rate in the highest dose cohort (6 of 7 patients) and 65% overall response rate for cSCC, including 9 complete responses, are encouraging for a Phase 1b trial, especially given the favorable safety profile.
• While direct comparisons to specific competitor drugs at the same early stage are challenging without detailed trial designs, these early efficacy signals for PH-762, a PD-1 gene silencer, suggest potential in a market with established PD-1 inhibitors like Merck's Keytruda (pembrolizumab) and Bristol Myers Squibb's Opdivo (nivolumab), which are typically systemic treatments for advanced cancers. PH-762's intratumoral delivery and potential as a non-surgical option for skin cancers could carve out a niche.
• The absence of serious adverse events or dose-limiting toxicities across all cohorts is a strong positive, often exceeding typical safety profiles seen in early-stage oncology trials for novel agents.

Stakeholder Impact

• Shareholders: Positive impact due to de-risking of the lead clinical candidate, potentially leading to increased stock value if positive momentum continues.
• Patients: Potential for a new, non-surgical treatment option for various skin cancers, particularly if PH-762 progresses successfully through later stages.
• Employees: Positive impact on morale and job security due to significant progress in the lead development program.

Next Steps

• Continued evaluation of the highest dose concentration of PH-762 in the next clinical trial.
• FDA submission targeted for Q2 2026 to propose and seek guidance for next clinical study design for PH-762.
• Availability of drug substance material (API) in March 2026 for non-human primate study.
• Commencement of manufacturing of cGMP material in the second half of 2026.

Key Dates

Recommendation

The positive safety profile with no serious adverse events and the high pathological response rates, including complete responses, in the highest dose cohort of a Phase 1b trial for PH-762 are significant de-risking events for a clinical-stage biopharmaceutical company. These results provide strong validation for the INTASYL platform and PH-762's potential as a non-surgical treatment for skin cancers. The clear path to an FDA submission and manufacturing scale-up further supports a strong buy recommendation, as these milestones indicate robust progress towards pivotal trials and potential commercialization.

Keywords

Phio Pharmaceuticals, PHIO, PH-762, siRNA, INTASYL, gene silencing, immuno-oncology, skin cancer, cutaneous squamous cell carcinoma, melanoma, Merkel cell carcinoma, Phase 1b clinical trial, safety monitoring committee, pathological response, complete response, biopharmaceutical, clinical-stage