GeoVax Labs, Inc. announced the start of an investigator-initiated clinical trial (ClinicalTrials.gov Identifier: NCT05672355), titled ?Randomized observer-blinded phase 2 trial of COVID-19 booster with GEO-CM04S1 or Pfizer-BioNTech Bivalent vaccine in patients with chronic lymphocytic leukemia,? at City of Hope National Medical Center, led by Alexey Danilov, M.D., PhD as principal investigator. GEO-CM04S1, a multi-antigenic SARS-CoV-2 vaccine that targets the spike (S) and nucleocapsid (N) proteins of SARS-CoV-2, is actively under clinical study by GeoVax in severely immunocompromised individuals, as well as in healthy adults for use as a universal heterologous booster.

Despite a high vaccination rate, chronic lymphocytic leukemia (CLL) patients may be at high risk for lethal COVID-19 infection due to poor immune response to COVID-19 infections or vaccination. The GEO-CM04S1 vaccine uses a modified vaccinia virus (MVA) backbone that may be more effective at inducing COVID-19 immunity in patients with poor humoral immune responses since MVA strongly induces T cell expansion even in the background of immunosuppression. Targeting both the spike and nucleocapsid protein antigens broaden the specificity of the immune responses and protects against the loss of efficacy associated with the significant sequence variation observed with the spike antigen.

The study will examine the use of two injections of GEO-CM04S1 three months apart to assess immune responses in these vulnerable patients, with the Pfizer-BioNTech Bivalent vaccine as the control arm. Participants will be randomized 1:1 to receive two boosters with either the GEO-CM04S1 or the control vaccine. The primary immune response outcome will be 56 days following the first booster injection.

Up to 40 participants will be treated in each arm, with immune responses evaluated at the interim and final analyses in each arm. About GEO-CM04S1: GEO-CM04S1 is a next-generation COVID-19 vaccine based on GeoVax?s MVA viral vector platform, which supports the presentation of multiple vaccine antigens to the immune system in a single dose. CM04S1 presents both the spike and nucleocapsid antigens of SARS-CoV-2 and is specifically designed to induce both antibody and T cell responses to non-variable parts of the virus.

The more broadly specific and functional engagement of the immune system is designed to protect against the new and continually emerging variants of COVID-19. Based on data from animal models and a completed Phase 1 clinical study, vaccine-induced immune responses were shown to recognize both early and later variants of SARS-CoV-2, including the Omicron variant. Vaccines of this format should not require repeated modification and updating.

A recent presentation of unpublished data from the open-label portion of the Phase 2 trial of CM04S1 (ClinicalTrials.gov Identifier: NCT04977024) in patients undergoing hematological cancer treatment (i.e., patients who have reduced immune system function as a result of treatment) indicates that CM04S1 is highly immunogenic in these patients, inducing both antibody responses, including neutralizing antibodies, and T cell responses. These data support the planned progression of the Phase 2 clinical study, which will include a direct comparison to currently approved mRNA vaccines. CM04S1 also continues to advance in another Phase 2 clinical trial as a booster for healthy patients who have previously received the Pfizer or Moderna mRNA vaccine (ClinicalTrials.gov Identifier: NCT04639466).

Data from these studies will form the basis for comparing vaccine potential in unique patient groups as well as the general population.