Drug resistance mutations and associated phenotypes detected in clinical trials of maribavir for treatment of cytomegalovirus infection

BACKGROUND In separate Phase 2 trials, 120 patients received maribavir for cytomegalovirus (CMV) infection failing conventional therapy (trial 202) and 119 received maribavir for asymptomatic infection (trial 203). Overall, 172 cleared their CMV infection (CMV DNA 14 days of therapy, 9 showed T409M or H411Y and 4 others showed C480F alone. CONCLUSIONS After maribavir therapy (400-1200 mg twice daily), UL97 mutations T409M, H411Y or C480F emerge to confer maribavir resistance in patients with recurrent CMV infection while on therapy, or no response to therapy.