Efficacy of Letermovir for Cytomegalovirus Prophylaxis Following Alemtuzumab T-Cell Depleted Allogeneic Hematopoietic Stem Cell Transplant.

In vivo T-cell depletion (TCD) using alemtuzumab decreases the risk of Graft vs Host Disease (GvHD) in recipients of allogeneic hematopoietic stem cell transplant (allo-HSCT). However, this approach increases the risk of infections post-allo-HSCT, including Cytomegalovirus (CMV). Letermovir is approved for the use in CMV prophylaxis post-allo-HSCT. Few studies have investigated the efficacy of letermovir in patients receiving alemtuzumab. This is a single-center retrospective study describing our institutional experience using letermovir in recipients of alemtuzumab TCD allo-HSCT from unrelated donors (URD). The primary outcome was the cumulative incidence of significant CMV infection (defined as viremia leading to preemptive antiviral therapy or CMV disease) within 100 days post-transplant. Secondary outcomes included the cumulative incidence of acute GvHD (grade ≥ 2), the cumulative incidence of extensive chronic GvHD, and overall survival. A total of 84 alemtuzumab TCD URD allo-HSCT recipients were included in the analysis, 30 of whom received letermovir (letermovir group) and 54 who did not receive letermovir (control group). The median age was 59 years (range: 26-75 years) and 55.5 years (range: 20-73 years) in the letermovir and control group, respectively. Most recipients (66.7%) in both groups received unrelated matched allografts, and myeloid neoplasms were the most common indication for allo-HSCT. A significantly lower cumulative incidence of significant CMV infection within 100 days was seen in the letermovir group compared to the control group (10.0% [95% CI: 2.5-23.9%] versus 55.6% [95% CI: 41.2-67.8%], P < .0001). There was no statistically significant difference in the incidence of acute GvHD (grade ≥ 2) or overall survival between the 2 groups. However, lower rates of extensive chronic GvHD were noted in the letermovir group (10.5% [95% CI: 2.6-24.9%] versus. 36.5% [95% CI: 23.6-49.5%], P = .0126). These results demonstrate the efficacy of letermovir in decreasing the rates of clinically significant CMV infection in patients undergoing alemtuzumab T-cell depleted allo-HSCT.