GeoVax Labs, Inc. has unveiled promising clinical data at the 2025 European Hematology Association Hybrid Congress, showcasing the superior performance of its GEO-CM04S1 vaccine in chronic lymphocytic leukemia (CLL) patients. The vaccine, based on a synthetic Modified Vaccinia Ankara vector, elicited significantly enhanced T cell responses compared to an authorized mRNA-based COVID-19 vaccine in a Phase 2 trial. This development is crucial for immunocompromised individuals, particularly those with hematologic malignancies like CLL, who often exhibit suboptimal responses to conventional vaccines.
The study highlighted that GEO-CM04S1 not only stimulated humoral immune responses but also achieved statistically significant SARS-CoV-2 Nucleocapsid-specific IgG and T cell responses, a feat the mRNA vaccine could not match. With the mRNA vaccine failing to meet the primary immunogenicity endpoint, further trial enrollment is now limited to the GEO-CM04S1 arm. Both vaccines were well-tolerated, with no severe adverse events reported, underscoring the safety profile of GEO-CM04S1.
Dr. Kelly T. McKee, Jr., GeoVax's Chief Medical Officer, emphasized the clinical and immunologic advantages of their multi-antigen approach, which could address critical gaps in COVID-19 protection for vulnerable populations. The ongoing Phase 2 trials across various patient populations, including healthy adults, aim to further validate GEO-CM04S1's potential as a more robust and durable COVID-19 vaccine option.
