AntiCMV molécules Monitoring in Real-life in Stem Cell Recipients

Cytomegalovirus (CMV) is a ubiquitous herpesvirus that represent a major cause of morbidity in haematopoietic stem cell transplants (HSCT) recipients, mostly through reactivation of the recipient's virus. If left untreated, 40 to 80% of patients will develop CMV infection, leading to CMV disease in 30 to 35 % patients, and associated with considerable morbi-mortality. Interstitial pneumonia is the most severe and specific manifestation, although CMV replication by itself has also indirect effects such as triggering graft versus host disease and increasing immunosuppression. The current burden of CMV infection increases by 25 to 30% the cost of the graft in France. This also includes the burden for refractory - infections, that represent up to 13% of recipients with CMV infection, including 3% of cases with virological resistance in France (data from the Reference Center cohorts). Ganciclovir, or valganciclovir preemptive treatment, guided by CMV viral load follow-up allowed significant reduction of CMV disease to 2-6% but did not prevent CMV indirect effects. In addition, hematotoxicity can compromise post-transplant haematological reconstitution, thus preventing its use as prophylaxis in France. Foscarnet, iv-administered and nephrotoxic, remains less used. There is thus a high expectation from less toxic molecules for prophylaxis The development letermovir recently available for prophylaxis of CMV infection in high risk patients will modify the patients care and follow-up. This new molecule targeting CMV terminases (developed by Merck) was recently marketed in France (Jan 2020). However, the analysis of the letermovir phase III study and further publications show that the risk of emergence of resistance is low, but may occur in case of breakthrough and thus post AMM monitoring is required. A "real-life" evaluation of these new molecules in terms of efficacy, emergence of resistance, tolerance and morbimortality related to CMV infection, is useful, to propose re