GeoVax Study Shows Gedeptin May Enhance Checkpoint Inhibitor Responses in Resistant Tumors
Peer-reviewed research in JCI Insight demonstrates GeoVax's Gedeptin platform can sensitize resistant tumors to immune checkpoint inhibitors and activate systemic anti-tumor immunity, potentially broadening cancer immunotherapy efficacy.
GeoVax Labs, Inc. (Nasdaq: GOVX) announced findings from a peer-reviewed study published in JCI Insight that support the potential of its Gedeptin platform to enhance immune checkpoint inhibitor responses in treatment-resistant solid tumors. The research, titled “Broadening Activity of Checkpoint Blockade Agents by Intratumoral Nucleoside Cleavage,” provides scientific validation for the biologic rationale underlying GeoVax’s planned combination therapy strategies.
The study evaluated E. coli PNP/F-araA, the therapeutic mechanism behind Gedeptin, in triple-negative breast cancer (TNBC) models known to be resistant to conventional treatments including radiation, checkpoint inhibitors, and anti-TGF-β therapy. In vitro results showed that E. coli PNP/F-araA treatment initiated a signaling cascade associated with immune sensitization. In vivo, tumors expressing E. coli PNP were completely regressed and cured in all treated mice after administration of F-araAMP, a prodrug of F-araA.
Importantly, when subcurative doses of F-araAMP were combined with immune checkpoint inhibitors, significant tumor burden reductions and complete regressions were observed in otherwise resistant tumors. The study also found that treating a PNP-expressing tumor with F-araAMP enhanced immune checkpoint blockade in distant, untreated tumors, indicating systemic anti-tumor immunity activation after a single treatment cycle.
“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.”
GeoVax believes these results position Gedeptin as a broader immune-sensitization and tumor microenvironment engineering platform applicable across multiple solid tumors where checkpoint therapy alone is insufficient. The company is advancing development plans to evaluate Gedeptin in combination with checkpoint inhibitors, including pembrolizumab-based regimens.
Gedeptin is a gene-directed enzyme prodrug therapy (GDEPT) that uses a non-replicating adenoviral vector to deliver purine nucleoside phosphorylase (PNP) into tumors. After administration of fludarabine, PNP converts the prodrug into a potent localized cytotoxic compound. Key characteristics include a strong bystander killing effect, tumor microenvironment remodeling, and potential systemic immune activation, supported by prior Phase 1 and Phase 1/2a clinical studies.
GeoVax continues to evaluate strategic partnerships and funding opportunities aligned with its development priorities. The company’s oncology program also includes GEO-MVA, a vaccine targeting mpox and smallpox, which is advancing under an expedited regulatory pathway with a planned Phase 3 trial in the second half of 2026.