Phio Pharmaceuticals Corp.

Most cancer immunotherapies work by flooding the body with antibodies delivered through systemic infusion. INTASYL takes a different approach: it silences the specific gene that prevents immune cells from doing their job. By injecting PH-762 directly into the tumor, Phio targets the PD-1 gene at its source in the T cell, reactivating the immune system's ability to recognize and kill cancer cells without the side effects typically associated with systemic treatment.

The PH-762 Phase 1b trial enrolled up to 24 patients with skin cancers including cutaneous squamous cell carcinoma (cSCC), melanoma, and Merkel cell carcinoma. Of the 20 cSCC patients evaluated at week five, 10 achieved 100% tumor clearance, 2 achieved greater than 90% clearance, and no patients experienced disease progression. The treatment phase completed in January 2026 across five escalating dose cohorts with no immune-related or treatment-limiting toxicities observed.

Cutaneous squamous cell carcinoma is the second most common solid tumor in the U.S. by incidence, with approximately 1.8 million new cases annually. For Stages I and II cSCC, which account for roughly 1.4 million of those cases, no FDA-approved drug therapy currently exists. Surgery is the standard of care, making PH-762 a potential non-surgical treatment option in a market Phio estimates at approximately $20 billion.

Because PH-762 is injected directly into the tumor rather than infused systemically, it avoids the off-target side effects common to monoclonal antibody therapies. The formulation requires no lipid nanoparticles, viral vectors, or formulation enhancers, and it is administered in a physician's office rather than an infusion center. Through five escalating dose cohorts representing a 20-fold increase in drug concentration, no patients experienced immune-related or treatment-limiting toxicities.

PH-894 targets the BRD4 gene, which is implicated in multiple cancer types including melanoma, prostate, breast, cervical, lung, liver, head and neck, and cSCC. Unlike earlier BRD4-targeting compounds, PH-894 is precisely selective for the BRD4 gene, which the company reports eliminates the toxicity associated with non-selective predecessors. PH-894 has completed IND-enabling studies and demonstrated a clean toxicology profile in non-human primates, positioning it for the next stage of development.

Phio's intellectual property portfolio covers INTASYL chemistry, specific drug compounds, individual gene targets, and therapeutic indications, with 59 patents issued and additional applications pending in US and otherkey countries. extending protection into 2044.These compounds span both current clinical programs and a broader library of gene silencing compounds across oncology, auto-immune conditions, and other indications that the Company makes available for out-licensing to third parties.