Maribavir, sold under the brand name Livtencity, is an antiviral medication that is used to treat post-transplant cytomegalovirus (CMV). Maribavir is a cytomegalovirus pUL97 kinase inhibitor that works by preventing the activity of human cytomegalovirus enzyme pUL97, thus blocking virus replication. The most common side effects include taste disturbance, nausea, diarrhea, vomiting and fatigue. Maribavir was approved for medical use in the United States in November 2021, and in the European Union in November 2022. The US Food and Drug Administration (FDA) considers it to be a first-in-class medication. Medical uses In the United States, maribavir is indicated to treat people twelve years of age and older and weighing at least with post-transplant cytomegalovirus infection/disease that does not respond (with or without genetic mutations that cause resistance) to available antiviral treatment for cytomegalovirus. In the European Union, maribavir is indicated for the treatment of cytomegalovirus (CMV) infection and/or disease that are refractory (with or without resistance) to one or more prior therapies, including ganciclovir, valganciclovir, cidofovir or foscarnet in adults who have undergone a hematopoietic stem cell transplant (HSCT) or solid organ transplant (SOT). Adverse effects Adverse effects of maribavir include taste disturbances, nausea, and vomiting. Contraindications The cytomegalovirus pUL97 kinase activates ganciclovir and valganciclovir, so coadministration with these medications is not recommended because maribavir may reduce their antiviral activity. History Maribavir is licensed by ViroPharma from GlaxoSmithKline in 2003, for the prevention and treatment of human cytomegalovirus (HCMV) disease in hematopoietic stem cell/bone marrow transplant patients. The mechanism by which maribavir inhibits HCMV replication is by inhibition of an HCMV encoded protein kinase enzyme called UL97 or pUL97. Maribavir showed promise in phase II clinical trials and was granted fast track status, but failed to meet study goals in a phase III trial. However, the dosage used in the phase III trial may have been too low to be efficacious. A phase II study with maribavir demonstrated that prophylaxis with maribavir displayed strong antiviral activity, as measured by statistically significant reduction in the rate of reactivation of CMV in recipients of hematopoietic stem cell/bone marrow transplants. In an intent-to-treat analysis of the first 100 days after the transplant, the number of subjects who required pre-emptive anti-CMV therapy was statistically significantly reduced with maribavir compared to placebo. ViroPharma conducted a phase III clinical study to evaluate the prophylactic use for the prevention of cytomegalovirus disease in recipients of allogeneic stem