*Purpose: Studies evaluating the efficacy of valganciclovir (VGC) at 450 mg daily versus 900 mg daily for the prevention of cytomegalovirus (CMV) in kidney transplant recipients (KTR) provide conflicting results. At our institution, moderate risk (CMV IgG seropositive) KTR receive a goal dose of VGC at 450 mg daily for the prevention of CMV. We sought to determine the incidence of CMV in patients that VGC 450 mg daily would be appropriate dosing based on allograft function compared to those that were under-dosed on this regimen.

*Methods: A retrospective, single-center chart review of adult (≥ 18 years) moderate CMV risk KTR transplanted from 10/1/15 to 10/1/16 was conducted. Patients were stratified at one month post-transplant into two groups based on whether VGC was under-dosed or not under-dosed per FDA-approved dosing recommendations according to creatinine clearance (CrCl). The primary outcome was the incidence of CMV within 6 months post-transplant in under-dosed versus not under-dosed KTR.

*Results: A total of 151 KTR were included for analysis, with 48 (31.8%) under-dosed on VGC at one month post-transplant and 103 (68.2%) not under-dosed. Overall, CMV infection occurred in 25 (15.9%) patients and CMV disease occurred in 9 (6%) patients. There was no difference in incidence in CMV infection (14.6% vs 17.8%, p=0.656) or CMV disease (8.3% vs 4.9%, p=0.170) in patients that were under-dosed versus not under-dosed, respectively. Patients in the under-dosed cohort had significantly higher mean CrCl on discharge from index hospitalization (46.2 mL/min vs 31.9 mL/min, p=<0.001) as well as 1 month after transplant (66.4 mL/min vs 41.3 mL/min, p<0.001). Under-dosing VGC was not associated with CMV breakthrough while on VGC prophylaxis (8% vs 16%, p=0.739). Patients that were under-dosed had longer median time to their first positive CMV PCR (147 days vs 136 days, p<0.001), but also had a longer median time to clearance of CMV DNAemia (42 vs 14 days, p=0.013). There was no difference in the development of leukopenia between patients that were under-dosed versus not under-dosed (52.1% vs 52.5% respectively) (Table 1).

*Conclusions: Under-dosing VGC was not associated with an increased incidence of CMV infection or CMV disease. The results of this study support that low-dose VGC may be reasonable dosing strategy to prevent CMV infection in moderate risk KTR.

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