Pharmacist-Driven Specialty Pharmacy Model for Letermovir Prophylaxis in CMV Seropositive Allogeneic HCT Patients

Approximately 45-60% of allogeneic transplant patients are cytomegalovirus seropositive (CMV+) and at risk for reactivation. Prophylaxis with letermovir may prevent CMV reactivation and reduce associated morbidity and mortality.Internal data prior to letermovir use from 2016-2019 demonstrated CMV reactivation in 72% of CMV+ allogeneic patients. Given the high reactivation rate our center initiated a pharmacist-driven letermovir standard operating procedure beginning July 2020. During the pre-transplant evaluation, the BMT Clinical Pharmacy Specialist (CPS) sends a letermovir prescription for CMV+ patients to our in-house specialty pharmacy. Letermovir is utilized during the initial transplant admission beginning on Day +7 through at least Day +100. We sought to characterize CMV reactivation rates after implementation of letermovir as a pharmacist-driven process.All adult CMV+ allogeneic recipients transplanted between July 1, 2020 to July 1, 2023 and prescribed letermovir prophylaxis were evaluated. Patients were included if taking letermovir at the time of reactivation (defined as a viral load of ≥ 300 IU/mL). Patients with early death prior to Day +30 or unable to start letermovir were excluded. Patients considered high-risk for CMV reactivation prior to transplant include those receiving abatacept, post-transplant cyclophosphamide (PTCy), alemtuzumab, or antithymocyte-globulin (ATG).Demographics of 95 patients included are in Table 1. CMV reactivation rate on letermovir was reduced to 5% with a median of 11 days to reactivation after transplant. 19% of patients reactivated after stopping letermovir with a median of 146 days after transplant, 11 of which were on concomitant steroids. Of those patients, 77% were considered high risk for reactivation.Implementing a pharmacist-driven letermovir prophylaxis protocol drastically reduced CMV reactivation rates from 72% to 5%. Opportunities exist to optimize the timing of initiating or extending letermovir prophylaxis given patient-specific risk factors.