EQS-News: GeoVax Highlights Peer-Reviewed Research Supporting Gedeptin(R) Potential to Enhance Cancer Immunotherapy Responses

Publication Highlights Potential for Intratumoral Gedeptin® Therapy to Enhance Checkpoint Inhibitor Responses and Activate Systemic Anti-Tumor Immunity

ATLANTA, GA - June 8, 2026 (NEWMEDIAWIRE) - 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 (Journal of Clinical Investigation) 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.

The 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.

About Gedeptin®

Gedeptin® is GeoVax’s proprietary gene-directed enzyme prodrug therapy (GDEPT) platform under development for the treatment of solid tumors. The therapy is designed for intratumoral administration and utilizes a non-replicating adenoviral vector encoding purine nucleoside phosphorylase (PNP). Following administration of fludarabine, the PNP enzyme converts the prodrug into a potent localized cytotoxic compound within the tumor microenvironment.

Key characteristics of Gedeptin include:

• Localized activation of the prodrug fludarabine into the potent cytotoxic compound F-Ade;
• Strong bystander killing effect capable of destroying neighboring tumor cells even when only a small fraction are directly transduced;
• Tumor microenvironment remodeling and immune-sensitizing properties that may enhance responsiveness to checkpoint inhibitors;
• Potential systemic immune activation supported by preclinical evidence of anti-tumor effects in distant untreated lesions;
• Favorable safety observations demonstrated across prior Phase 1 and Phase 1/2a clinical studies.

GeoVax is advancing development plans to evaluate Gedeptin in combination with checkpoint inhibitors, including pembrolizumab-based regimens, with the goal of amplifying anti-tumor immune activation and broadening the therapy’s applicability across multiple solid tumor settings.

About GeoVax

GeoVax Labs, Inc. is a clinical-stage biotechnology company focused on the development of vaccines and immunotherapies addressing high-consequence infectious diseases and solid tumor cancers. GeoVax’s priority program is GEO-MVA, a Modified Vaccinia Ankara (MVA)–based vaccine targeting mpox and smallpox. The program is advancing under an expedited regulatory pathway, with plans to initiate a pivotal Phase 3 clinical trial in the second half of 2026, to address critical global needs for expanded orthopoxvirus vaccine supply and biodefense preparedness. In oncology, GeoVax is developing Gedeptin®, a gene-directed enzyme prodrug therapy (GDEPT) designed to enhance immune checkpoint inhibitor activity. Gedeptin has completed a multicenter Phase 1/2 clinical trial in advanced head and neck cancer and is being advanced into combination strategies, including planned neoadjuvant and first-line settings. GeoVax maintains a global intellectual property portfolio supporting its infectious disease and oncology programs and continues to evaluate strategic partnerships and funding opportunities aligned with its development priorities. For more information, visit www.geovax.com.

Forward-Looking Statements

This release contains forward-looking statements regarding GeoVax’s business plans. The words “believe,” “look forward to,” “may,” “estimate,” “continue,” “anticipate,” “intend,” “should,” “plan,” “could,” “target,” “potential,” “is likely,” “will,” “expect” and similar expressions, as they relate to us, are intended to identify forward-looking statements. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. Actual results may differ materially from those included in these statements due to a variety of factors, including whether: GeoVax is able to obtain acceptable results from ongoing or future clinical trials of its investigational products, GeoVax’s immuno-oncology products and preventative vaccines can provoke the desired responses, and those products or vaccines can be used effectively, GeoVax’s viral vector technology adequately amplifies immune responses to cancer antigens, GeoVax can develop and manufacture its immuno-oncology products and preventative vaccines with the desired characteristics in a timely manner, GeoVax’s immuno-oncology products and preventative vaccines will be safe for human use, GeoVax’s vaccines will effectively prevent targeted infections in humans, GeoVax’s immuno-oncology products and preventative vaccines will receive regulatory approvals necessary to be licensed and marketed, GeoVax raises required capital to complete development, there is development of competitive products that may be more effective or easier to use than GeoVax’s products, GeoVax will be able to enter into favorable manufacturing and distribution agreements, and other factors, over which GeoVax has no control.

Further information on our risk factors is contained in our periodic reports on Form 10-Q and Form 10-K that we have filed and will file with the SEC. Any forward-looking statement made by us herein speaks only as of the date on which it is made. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.

Company Contact: info@geovax.com 678-384-7220

Media Contact: Jessica Starman media@geovax.com