Dateline — King of Prussia, Pennsylvania, November 7, 2025:
Phio Pharmaceuticals Corp. (NASDAQ: PHIO) has announced new clinical data from its ongoing Phase 1b study of INTASYL PH-762, an siRNA-based immunotherapy targeting PD-1 in cutaneous squamous cell carcinoma, Merkel cell carcinoma, and melanoma. The results will be presented at the 40th Annual Meeting of the Society for Immunotherapy of Cancer (SITC).
Science Significance
Phio’s INTASYL® gene-silencing platform represents a pioneering step in RNA interference (RNAi) for cancer therapy. The compound PH-762 works by silencing the PD-1 gene, a key immune checkpoint regulator that tumors exploit to evade the immune system. By reducing PD-1 expression directly within tumors through intratumoral injection, Phio aims to locally re-activate immune cells and enhance anti-tumor immunity. This approach offers a novel alternative to systemic checkpoint inhibitors, potentially minimizing systemic toxicities and expanding the therapeutic window in solid tumors.
Regulatory Significance
As an early-stage investigational siRNA therapeutic, PH-762 sits within a rapidly emerging regulatory category of gene-silencing drugs governed by the U.S. FDA’s RNA-based therapy framework. The Phase 1b trial (NCT# 06014086) focuses on safety and dose-escalation, generating crucial data for potential advancement into Phase 2 efficacy trials. The outcomes may inform regulatory guidance on intratumoral RNA delivery, a domain still in development. Phio’s compliance with rigorous GCP standards underpins the reliability of the trial data, supporting future IND amendments and potential global submissions.
Business Significance
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Phio Pharmaceuticals’ clinical milestone strengthens its position as a front-runner in RNA-based immuno-oncology. The presentation at SITC 2025 enhances visibility among potential strategic partners, investors, and pharmaceutical collaborators. The company’s focus on a non-surgical cancer treatment could open new revenue streams in oncology markets, especially in localized and recurrent skin cancers. Moreover, advancing PH-762 reinforces the commercial potential of Phio’s INTASYL® technology platform, offering opportunities for licensing, co-development, and future pipeline expansion across multiple tumor types.
Patients’ Significance
For patients with advanced or recurrent skin cancers, the promise of a non-surgical, localized immunotherapy is highly significant. PH-762 aims to provide an alternative where surgery is not feasible or carries high morbidity. If proven safe and effective, it could improve quality of life, reduce hospitalization, and broaden access to precision immunotherapies. Additionally, limiting PD-1 suppression to the tumor site may reduce systemic immune-related adverse events that often accompany checkpoint inhibitor therapies, enhancing patient safety and tolerability.
Policy Significance
The development of RNA-based immunotherapies aligns with national and global health priorities that promote biotechnological innovation, translational medicine, and patient-centric regulatory pathways. Success in PH-762 may encourage regulatory harmonization between agencies like the FDA and EMA for localized gene therapies. It also underscores the importance of government and industry collaboration to accelerate the approval of next-generation oncology treatments, especially those addressing rare and high-mortality skin cancers.
Phio Pharmaceuticals’ Phase 1b progress with INTASYL PH-762 highlights a defining shift in the oncology landscape—from systemic blockade to localized, precision gene-silencing immunotherapy. As the company prepares to share its results at SITC 2025, the biotech community will watch closely to assess whether this first-in-class siRNA approach can deliver the safety, potency, and specificity needed to redefine cancer immunotherapy. The success of PH-762 could position Phio as a key innovator in the RNA-driven oncology revolution.
Source: Phio Pharmaceuticals press release
