A Single Center Retrospective Analysis of Letermovir for Cytomegalovirus Prophylaxis after Allogeneic Stem Cell Transplant in Cytomegalovirus Seropositive Recipients or Donors

Background: Up to 70% of allogeneic stem cell transplant (alloSCT) recipients who are cytomegalovirus (CMV) seropositive experience CMV reactivation and up to a third are complicated by end-organ disease. Letermovir, an antiviral agent targeting CMV, is FDA-approved for prophylaxis of CMV reactivation in CMV seropositive recipients of alloSCT. 1-4 In CMV seropositive recipients, letermovir use up to week 14 after alloSCT has demonstrated a significantly lower incidence of clinically significant CMV infection (csCMVi) and an overall mortality benefit as far as 24 weeks after transplant. 5-8 However, data on csCMVi beyond 24 weeks is lacking. Additionally, more information is needed on letermovir use in patients who had prior alloSCT, are CMV seronegative, have a detectable CMV viral load but without csCMVi, and/or are high risk*. Methods: This is a single-center, retrospective, comparative cohort analysis of 524 patients who received alloSCT at Barnes-Jewish Hospital from January 2016 to June 2019. Of those, 191 patients were excluded because both the recipient and donor were seronegative for CMV. Patient information was obtained from the electronic medical record systems after IRB approval of the protocol. Gray's sub-distribution methods (while account for death as competing risk) were used to calculate the incidence of csCMVi and to assess the effect of letermovir on csCMVi. Univariate and multivariate Cox proportional hazards models were fitted for the effect of letermovir on overall survival (OS), and time-dependent Cox model was used to determine the effect of csCMVi on OS. Results: Out of 333 patients, 149 received letermovir. The median follow-up period was 13.38 months (0.033 to 63.8 months). A univariate analysis demonstrated that csCMVi was associated with worse OS (HR 2.173, 95% CI 1.602-2.948). Among those who received letermovir, there were reductions in csCMVi for the overall cohort and for high-risk patients at 100 days, 180 days, and 365 days after alloSCT. In seropositive recipients receiving seropositive alloSCT (CMV +/+), there were reductions in csCMVi at days 100, 180, and 365 after transplant. In seropositive recipients receiving seronegative alloSCT (CMV +/-), there was a reduction in csCMVi at 100 days after transplant. There was a reduction in CMV-related mortality at day 180 post-transplant (p=0.03) but not at day 365 (p=0.46). Additionally, for the overall cohort, the letermovir group showed worse OS from days 180-365 (HR 1.938, 9