Letermovir as Salvage Therapy for Cytomegalovirus Infection in Transplant Recipients

Background. Letermovir, a new viral terminase complex inhibitor, has been approved for the prevention of cytomegalovirus (CMV) infection in hematopoietic stem cell transplant patients. However, data on the efficacy and safety of letermovir for the treatment of CMV infection in transplant recipients remain scarce. Methods. We performed a single-center retrospective study of stem cell and organ transplant recipients who received letermovir for the treatment of CMV infection from November 2017 to October 2018. Results. Six patients were included, and 5 were evaluable. All received letermovir in the context of a refractory or resistant CMV infection including asymptomatic CMV viremia (n = 3), CMV syndrome (n = 1), and CMV pneumonitis and colitis (n = 1). The 3 asymptomatic patients experienced a decrease of the viral load (VL) to <200 IU/mL after letermovir therapy. One patient displayed a partial VL response (2-log of VL reduction) but a good clinical response, and one who received a suboptimal dose of letermovir experienced an increase of viremia. There were no treatment-related adverse effects. Conclusions. We demonstrate mixed efficacy in patients with refractory CMV infection suggesting that letermovir may be a useful therapeutic adjunct, potentially in combination with other antivirals.