GeoVax Labs, Inc. (Nasdaq: GOVX), a clinical-stage biotechnology company developing immunotherapies and vaccines for solid tumors and infectious diseases, today highlighted results from a newly published peer-reviewed research article in JCI Insight supporting the potential for intratumoral Gene Directed Enzyme Prodrug Therapy (GDEPT) to enhance immune checkpoint inhibitor responses across metastatic solid tumors.
The article, titled “Broadening Activity of Checkpoint Blockade Agents by Intratumoral Nucleoside Cleavage,” provides important scientific validation supporting the biologic rationale underlying GeoVax’s Gedeptin® immuno-oncology platform and its planned clinical development strategy evaluating Gedeptin in combination with immune checkpoint inhibitors.
Investigators reported results from studies evaluating the ability of E. coli PNP/F-araA, the therapeutic concept underlying Gedeptin, to both kill treated tumors and enhance immune checkpoint inhibitor activity against both treated and untreated tumors. A triple-negative breast cancer (TNBC-EMT6) cell line, known to be resistant to conventional treatment approaches including radiation, immune checkpoint inhibitors, anti-TGF-β therapy, and other modalities, was utilized for these studies.
Results from in vitro investigations demonstrated that E. coli PNP/F-araA treatment initiated a signaling cascade previously associated with immune sensitization and enhanced responsiveness to immune checkpoint inhibitors. In complementary in vivo studies, tumors expressing E. coli PNP were implanted and grown in BALB/c mice harboring TNBC. Treatment with F-araAMP, a prodrug of F-araA, resulted in complete regression and cure of the PNP-expressing tumors in all treated animals.
To evaluate whether PNP/F-araA therapy could enhance immune checkpoint inhibitor activity in otherwise resistant tumors, investigators administered subcurative doses of F-araAMP followed by treatment with immune checkpoint inhibitors. Significant reductions in tumor burden were observed following combination treatment, with complete tumor regressions reported in treated animals.
Importantly, immune checkpoint blockade of non-PNP-expressing parental tumors was also enhanced when a contralateral PNP-expressing tumor was treated with F-araAMP and induced to regress. This anti-tumor effect on distant, untreated tumors was observed following a single cycle of PNP/F-araAMP therapy.
These findings suggest that localized treatment of lesions with Gedeptin may broaden the anti-tumor activity of immune checkpoint inhibitors beyond just the directly treated lesions. The observation that responses were enhanced in distant untreated tumors is of particular scientific interest given the limited effectiveness of checkpoint blockade in many treatment-resistant tumor settings and supports further investigation of this approach in combination immunotherapy strategies.
“These findings substantially expand the scientific relevance of Gedeptin beyond localized tumor control,” said David Dodd, Chairman and Chief Executive Officer 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.”
“We believe these findings position Gedeptin not simply as an intratumoral therapy, but as a broader immune-sensitization and tumor microenvironment engineering platform with potential applicability across multiple solid tumors where immune checkpoint therapy alone remains insufficient,” continued Mr. Dodd.
The publication also references prior clinical experience with PNP-based gene therapy approaches, supporting the translational relevance and clinical lineage of the underlying therapeutic mechanism.
