Maribavir and human cytomegalovirus—what happened in the clinical trials and why might the drug have failed?

We summarize the history of the clinical drug development of maribavir for its use as prophylaxis in stem-cell transplant recipients. We highlight key aspects in the design and interpretation of the results of the dose escalation phase II maribavir study that may have contributed to the negative findings on the phase III trials. We discuss key aspects of study design that should be considered in the study of new interventions needed to advance the prevention and treatment of CMV in transplant recipients.

► We summarize the history of the clinical drug development of maribavir for its use as prophylaxis in stem-cell transplant recipients.
► We highlight key aspects in the design and results of the phase 2 study that may have contributed to the negative findings on the phase 3 trials.
► We discuss key aspects of study design to consider in the study of new interventions for the prevention and treatment of CMV in transplantation.