Letermovir for pre-emptive cytomegalovirus therapy after allogeneic hematopoietic cell transplantation

Background: Cytomegalovirus (CMV) is a common cause of morbidity after allogeneic haematopoietic cell transplantation (alloHCT). Pre-emptive therapy (PET) with valganciclovir (VGC) is associated with haematological toxicity. Methods: We included alloHCT patients from 2018 to 2021 where letermovir (LTV) was used for CMVPET because of cytopenias. Results: Ten patients were included. Six received VGC prior to LTV. VGC was commenced at median d42, given for median 40 days. LTV was commenced at median d90, given for median 54 days. At commencement of antiviral, CMV viral load was higher for VGC at 3.7 log10 IU/mL, compared to LTV at 2.9 log10 IU/mL. Viral load reduction occurred at 0.18 log10 IU/mL per week forVGC, compared to 0.17 log10 IU/mL per week for LTV. There was no clinically significant CMVviremia after stopping LTV. Cytopenias improved on LTV. Conclusion: LTV was effective in controlling CMVviremiawhen it was given at a lower starting CMV viral load and later post alloHCT than VGC. Further study is required of LTV as upfront PET following alloHCT.