GeoVax Labs, Inc. (Nasdaq: GOVX) announced results from a newly published peer-reviewed research article in JCI Insight that validates the potential of its Gedeptin platform to enhance immune checkpoint inhibitor responses in treatment-resistant solid tumors. The study, titled "Broadening Activity of Checkpoint Blockade Agents by Intratumoral Nucleoside Cleavage," provides scientific rationale for combining Gedeptin with immune checkpoint inhibitors to potentially improve outcomes in patients with metastatic disease.
The research utilized a triple-negative breast cancer (TNBC) cell line known to be resistant to conventional treatments, including radiation, immune checkpoint inhibitors, and anti-TGF-β therapy. Investigators tested the therapeutic concept underlying Gedeptin, which involves E. coli purine nucleoside phosphorylase (PNP) combined with the prodrug F-araA. In vitro results showed that this treatment initiated a signaling cascade associated with immune sensitization and enhanced responsiveness to checkpoint inhibitors.
In vivo studies in BALB/c mice implanted with TNBC tumors expressing E. coli PNP demonstrated that treatment with F-araAMP, a prodrug of F-araA, led to complete regression and cure of all treated tumors. When subcurative doses were followed by immune checkpoint inhibitors, significant reductions in tumor burden were observed, with complete regressions in some animals.
A key finding was the abscopal effect: immune checkpoint blockade of non-PNP-expressing tumors was enhanced when a contralateral PNP-expressing tumor was treated with F-araAMP. This anti-tumor effect on distant, untreated tumors occurred after a single treatment cycle, suggesting that localized Gedeptin therapy could broaden checkpoint inhibitor activity beyond directly treated lesions.
"These findings substantially expand the scientific relevance of Gedeptin beyond localized tumor control," said David Dodd, Chairman and CEO of GeoVax. "The data suggest that localized Gedeptin treatment may function as a force multiplier for checkpoint inhibitors by activating systemic anti-tumor immunity, disrupting immunosuppressive tumor microenvironments, and potentially broadening immune checkpoint inhibitor responses beyond directly treated tumors."
The publication also references prior clinical experience with PNP-based gene therapy approaches, supporting the translational relevance of the mechanism. Gedeptin is a gene-directed enzyme prodrug therapy (GDEPT) that uses a non-replicating adenoviral vector to deliver PNP into tumor cells. After administration of fludarabine, the enzyme converts the prodrug into a potent cytotoxic compound locally, with a strong bystander effect that can destroy neighboring tumor cells even if only a small fraction are transduced.
GeoVax is advancing development plans to evaluate Gedeptin in combination with checkpoint inhibitors, including pembrolizumab-based regimens. The company believes the platform could be applicable across multiple solid tumors where immune checkpoint therapy alone remains insufficient. For more information, visit www.geovax.com.
