Real‐World Off‐Label Use of Letermovir Prophylaxis for Cytomegalovirus Prevention in Non‐Kidney Solid Organ Transplant Recipients: Outcomes, Safety, and Review of Literature

ABSTRACT Introduction Cytomegalovirus (CMV) causes substantial morbidity after solid organ transplantation. Valganciclovir (VGCV) remains a first‐line prophylactic agent, but it has significant myelosuppressive effect. Letermovir is approved for CMV prophylaxis in high‐risk kidney transplant recipients, but data on its use outside of that population are limited. We describe characteristics and outcomes of letermovir prophylaxis in non‐kidney transplant recipients. Methods We performed a retrospective, multi‐center study of all adult non‐kidney solid organ transplant recipients (SOTr) who received letermovir (March 2018–June 2024) for CMV prophylaxis. Outcomes included breakthrough and post‐prophylaxis delayed‐onset CMV infections, adverse events, and survival. Results A total of 64 patients were included in the final analysis. Of those, letermovir was used for primary prophylaxis in 56.2% of patients, while the remainder received it for secondary prophylaxis. The main rationale behind selecting letermovir was myelosuppression related to VGCV. During the median follow‐up of 361 days (IQR, 190–536), 40.6% remained on letermovir (median, 387 days); 25.0% completed prophylaxis (median, 116 days); and 34.3% discontinued prematurely (median, 49 days), mainly for cost barriers or adverse effects. Breakthrough infections occurred in 9 patients (14.1%), but only three (4.7%) were clinically significant. After stopping letermovir, 39.5% (15/38 among those who discontinued letermovir) developed post‐prophylaxis delayed‐onset CMV infection. Overall survival was 81.2%; there was one death attributed to CMV. Conclusion In this cohort of non‐kidney solid organ recipients, letermovir was well tolerated with low rates of clinically significant breakthrough infections. Early discontinuation was commonly cost‐driven. Post‐prophylaxis delayed‐onset CMV infections remain common. Large‐scale registry studies are needed to provide evidence for use of letermovir in non‐kidney transplant recipients.