GeoVax Labs, Inc.

GEO-CM04S1 is also being studied in an investigator-initiated clinical trial (ClinicalTrials.gov Identifier: NCT05672355), as a booster vaccine in immunocompromised patients with CLL. Despite high vaccination rates, CLL patients remain at elevated risk for lethal COVID-19 infection due impaired antibody responses to SARS-Cov-2 infections or vaccination. GEO-CM04S1 may induce protective immunity in this patient population by targeting both the S and N protein antigens, potentially mitigating reduced efficacy associated with inadequate antibody responses. The study is evaluating two injections of GEO-CM04S1 administered three months apart, with the Pfizer-BioNTech bivalent vaccine serving as the control arm.

In November 2024, the DSMB conducted an interim review. Following its evaluation, the DSMB recommended continuation of enrollment in the GEO-CM04S1 experimental arm, but discontinuation of the mRNA control arm due to failure to meet the predetermined primary immune endpoint. This outcome suggests a potentially superior immune response in this vulnerable population, however no efficacy conclusions can be drawn until the study is complete. Enrollment of the remaining patient participants is ongoing.

GEO-CM04S1 as a Booster Vaccine

Since GEO-CM04S1 is designed to stimulate both humoral and cellular immune responses against both the S and N proteins, GeoVax believes its administration as a booster may induce a broader and more sustained immune response compared to mRNA boosters. In addition, GEO-CM04S1 addresses the waning effectiveness observed with current COVID-19 vaccines over time, due to the constant sequence variation observed with the S antigen because the N antigen tends not to change significantly amongst variants.

GEO-CM04S1 is being evaluated in a Phase 2 trial (ClinicalTrials.gov Identifier: NCT04639466), as a heterologous booster following FDA-approved mRNA vaccines from Pfizer/BioNTech or Moderna.

The Phase 2 booster study was designed to evaluate the safety and immunogenicity of two dose levels of GEO-CM04S1. The study enrolled 63 healthy adults previously vaccinated with an FDA-approved SARS-CoV-2 mRNA vaccine. Immunological endpoints including binding antibodies, neutralizing antibodies and T-cell responses against variants of concern (VOC), including Delta and Omicron variants.

In February 2024, we announced positive initial safety and immune response findings at one month post-vaccination. Follow-up of enrolled participants was completed in September 2024. No serious adverse events related to vaccination were observed; all adverse events were consistent with those seen following routine vaccinations. Immunological responses included binding antibodies, neutralizing antibodies against multiple variants (including Omicron) and variant-specific T-cell responses. Enrollment for this trial has closed and data readouts are expected in the first half of 2026.

GEO-CM04S1 -- BARDA Project NextGen Award-** Phase 2b Trial**

In June 2024, we announced our receipt of an award through the Rapid Response Partnership Vehicle (RRPV) to advance development of GEO-CM04S1 in a Phase 2b clinical trial. The RRPV is a consortium funded by the Biomedical Advanced Research Development Authority (BARDA), part of the Administration for Strategic Preparedness and Response (ASPR) within the U.S. Department of Health and Human Services (HHS). Advanced Technology International (ATI) administers the RRPV programs on behalf of BARDA.

On April 11, 2025, we received written notification from ATI (the Notice) directing the Company to immediately cease all work related to the ATI-RRPV contract. The Notice instructed GeoVax to halt all activities associated with the project agreement, including all subcontracting, procurement of materials, and any other project-related expenditures. The Notice further indicated that BARDA had determined to terminate the contract for convenience pursuant to the terms of the ATI-RRPV contract. As of receipt of the Notice, GeoVax had met all milestone requirements of the ATI-RRPV contract.