The goal of this laboratory research study is to learn if interrupting a patient's letermovir dosing based on their immune system response can help HSC transplant patients avoid post-treatment CMV infections better than taking letermovir every day without interruption.
Allogeneic HCT recipients with positive CMV serostatus
On letermovir prophylaxis at day 90 post transplant (+/- 7 days)
Prior or active graft versus host disease requiring systemic steroids
Mismatch stem cell donor (includes haploidentical, mismatch unrelated donor (MMUD), match related donor with at least one mismatch at one of the three specified HLA gene loci (HLA-A, HLA-B, or HLA-DR) and cord donor recipients)
Patients under the age of 18
Patients are discharged from our institution and unwilling to come back for follow up
Patients are actively undergoing treatment for CS-CMVi at time of screening. Prior CS-CMVi is not an exclusion from study.
Patients are allergic or intolerant to letermovir or have history of letermovir resistant CMV infection.