On Mar. 10, 2022,  a COVID-19 investigational vaccine, developed by City of Hope scientists and now licensed to GeoVax Labs, produced a robust neutralizing antibody and T cell (an immune cell) response against SARS-CoV-2 with no significant side effects in a Phase 1 clinical trial led by John Zaia, M.D., Aaron D. Miller and Edith Miller Chair for Gene Therapy, according to a study published in The Lancet Microbe.

COH04S1 is uniquely different than the many vaccines that have been developed because it targets both the spike and nucleocapsid proteins, in contrast to the current U.S. Food and Drug Administration (FDA)-approved COVID-19 vaccines, which only target the spike protein.

COH04S1 is being studied in a first-of-its-kind Phase 2 clinical trial for immunocompromised cancer patients who have difficulty producing antibodies and largely depend on T cells to protect against the virus responsible for COVID-19. Likewise, COH04S1 is also being evaluated in a Phase 2 vaccine booster trial format, which is aimed at evaluating how COH04S1 can boost pre-existing vaccine immunity to spike while also causing a strong immune response to nucleocapsid.

COH04S1 elicited neutralizing antibodies against the virus’ spike protein, which interacts with the human cellular ACE2 receptor, allowing the virus to enter cells of the lung, heart and other organs, resulting in damage and significant inflammation. These neutralizing antibodies were effective against the original SARS-CoV-2 and subsequent viral variants. T cells were produced against the SARS-CoV-2 nucleocapsid protein, as well as its spike protein, after just one dose of COH04S1.

In November 2021, GeoVax licensed the vaccine for further development and commercialization, including potentially as a first-line COVID-19 vaccine. GeoVax has now designated the vaccine as GEO-CM04S1.

For the Phase 1 trial at City of Hope, 58 healthy adult volunteers participated and 34 participants received two doses of COH04S1 28 days apart. Five received two placebo doses and 13 volunteers received a first dose of the vaccine and a second dose of the placebo. Volunteers who received the placebo were informed 56 days after first injection — of either the vaccine or placebo — that they didn’t receive one or both vaccine injections. They were offered COH04S1 or one of the then-emergency use authorized vaccines as a second dose.

T cells against the spike and nucleocapsid proteins were induced following the first dose of COH04S1. Following the second dose, given four weeks after the first, high amounts of neutralizing antibodies were detected at the next monitoring period. All vaccinated volunteers reached the primary immunological endpoint, defined as a four-fold increase of antibodies against the spike or nucleocapsid protein eight weeks after the first dose.