GeoVax's Multi-Antigen COVID-19 Vaccine Shows Superior Efficacy in CLL Patients, Prompting Trial Enrollment Shift

GeoVax Labs, Inc. presented positive interim Phase 2 data for its COVID-19 vaccine candidate GEO-CM04S1 at the International Workshop on Chronic Lymphocytic Leukemia conference, showing superior performance compared to standard mRNA vaccines in patients with chronic lymphocytic leukemia. The data, presented by City of Hope's Professor Alexey V. Danilov, came from an ongoing randomized Phase 2 trial (NCT05672355) comparing both vaccines in this immunocompromised patient population.

The trial results revealed that GEO-CM04S1 met the statistical requirements for the study's primary immune endpoint, while the mRNA vaccine arm did not achieve this benchmark. This differential performance led to a significant protocol change—following interim analysis and Data Safety Monitoring Board recommendation, further enrollment is now proceeding exclusively in the GEO-CM04S1 arm. This decision underscores the vaccine candidate's promising efficacy in a patient group where first-generation COVID-19 vaccines have proven inadequate.

GEO-CM04S1 represents a next-generation approach to COVID-19 vaccination, built on a Modified Vaccinia Ankara vector platform that encodes both the Spike and Nucleocapsid proteins of SARS-CoV-2. This multi-antigen design aims to drive broader, cross-variant, and more durable immune protection compared to single-antigen mRNA vaccines. The vaccine's ability to induce nucleocapsid-specific responses particularly distinguishes it from existing products and addresses a critical gap in protecting immunocompromised individuals.

The implications of these findings extend beyond clinical benefits to substantial market opportunities. With millions of immunocompromised patients worldwide, including those with hematologic malignancies like CLL, GEO-CM04S1 targets a multi-billion dollar market segment where durable protection remains elusive. David Dodd, GeoVax's Chairman and CEO, emphasized that immunocompromised patients have not been adequately protected by current vaccines, positioning GEO-CM04S1 as both a clinical breakthrough and compelling commercial opportunity.

Safety data from the trial showed both vaccines were well tolerated, with no grade 3 or higher adverse events reported. GEO-CM04S1 is currently being evaluated in three Phase 2 clinical trials: as a primary vaccine for immunocompromised patients with blood cancers or post-transplant status, as a booster in CLL patients, and as a more robust COVID-19 booster in previously mRNA-vaccinated healthy adults. For additional information about GeoVax's clinical programs, visit https://www.geovax.com.