GeoVax Labs, Inc. announced that vaccinations have begun in an investigator-initiated clinical trial of GEO-CM04S1 in patients with chronic lymphocytic leukemia, being conducted at City of Hope National Medical Center. Despite a high vaccination rate, CLL patients may be at high risk for lethal COVID-19 infection due to poor immune response to currently available vaccines. The GEO-CM04S1 vaccine uses a modified vaccinia virus (MVA) backbone to carry SARS-CoV-2 virus antigens 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.

By targeting both the spike and nucleocapsid protein antigens, GEO-CM04S1 broadens the specificity of the immune responses and protects against the loss of efficacy associated with current vaccines due to the significant sequence variation observed with the spike antigen. The study is examining the use of two injections of GEO-CM04S1, three months apart, to assess immune responses in these vulnerable patients, with an mRNA 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 assessed at 56 days following the first booster injection. Up to 40 participants in each arm will be vaccinated, with immune responses evaluated and compared at the interim and final analyses. 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.

GEO-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 A recent presentation of unpublished data from the open-label portion of the Phase 2 trial of GEO-CM04S1 in patients undergoing hematological cancer treatment indicates that GEO-CM04S1 is highly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.

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