Phio Pharmaceuticals Corp. reported that its lead candidate PH‑762, an INTASYL® anti‑PD‑1 siRNA, achieved an 85 % pathological response rate in the highest‑dose cohort of its Phase 1b intratumoral study, with four of six responders experiencing complete tumor clearance.
The study enrolled 22 patients who received four intratumoral injections and were followed for at least four weeks after the final dose. No serious adverse events or dose‑limiting toxicities were observed, underscoring the safety profile of PH‑762.
Across all five dose‑escalation cohorts, the overall response rate for cutaneous squamous cell carcinoma (cSCC) was 65 %, with 13 of 20 patients classified as pathologic responders. Nine of those were complete responses, two were near‑complete, and two were partial responses. A single patient with metastatic Merkel cell carcinoma also achieved a partial response.
These results support Phio’s planned FDA submission in the second quarter of 2026 and reinforce the clinical potential of the INTASYL platform as a non‑surgical treatment option for skin cancers.
CEO Robert Bitterman said the data “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.”
The announcement triggered a sharp market reaction, with the stock surging 57.8 % in pre‑market trading. Investors cited the high efficacy and clean safety profile as key drivers, viewing the data as a de‑risking milestone for the program.
Phio’s interim data from January 20 2026 had already shown a 70 % overall response rate for cSCC, with 100 % clearance in 10 of 14 responders, setting a strong foundation for the current results. The company is progressing with chemistry, manufacturing, and controls development, expecting API material in March 2026 and cGMP manufacturing in the second half of 2026.
In the competitive landscape, other immunotherapies for skin cancer are emerging, but PH‑762’s siRNA‑based mechanism and intratumoral delivery offer a distinct therapeutic niche. The data position Phio ahead of competitors that rely on systemic checkpoint inhibitors.
Phio’s cash balance was approximately $10.7 million as of June 30 2025, giving the company a runway into the first half of 2027. The strong clinical data may extend this runway by accelerating regulatory progress and potential future funding rounds.
With the FDA submission slated for Q2 2026, Phio is poised to advance PH‑762 into pivotal trials, potentially establishing a new class of non‑surgical skin‑cancer therapies.
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