On Sept. 14, 2021, City of Hope announced that it had begun enrolling patients in a Phase 2 clinical trial of its COH04S1 vaccine that is the first to study the safety and effectiveness of an investigational vaccine in blood cancer patients who have received a bone marrow transplant or chimeric antigen receptor (CAR) T therapy. The trial was also the first to compare an investigational COVID-19 vaccine to the current FDA-approved COVID-19 vaccine, the Pfizer vaccine, in people who are immunocompromised and receiving immunosuppressive therapy.

It follows a Phase 1 trial in healthy volunteers whose initial results demonstrated that COH04S1 was safe and well tolerated. Patients who are immunocompromised have often shown a weak antibody response after Emergency Use Authorization (EUA) and FDA-approved COVID-19 vaccinations compared with healthy vaccinated individuals.

Blood cancer patients who received a bone marrow transplant, either using a patient’s own stem cells or a donor’s cells, or CAR T cell therapy at least three months prior to enrolling in the study, and who meet other requirements are eligible for the trial.