Impact of Converting from Immediate-Release Tacrolimus to Envarsus on BK Viremia Incidence in Kidney Transplant Patients with Rapid Metabolism

BACKGROUND: BK infections have been observed more frequently among people who are rapid metabolizers. The tacrolimus c/d ratio identifies rapid metabolizers after transplantation. Envarsus has a lower peak drug level exposure than tacrolimus and is more pronounced in rapid metabolizers. This study hypothesized that less exposure to high tacrolimus levels through use of Envarsus would reduce the incidence of BK infections. MATERIAL/METHODS: This study prospectively converted 43 consecutive kidney transplant recipients (identified as rapid metabolizers by c/d ratio of <1) with negative serum BK viral load at month 2 following transplantation from IR tacrolimus to Envarsus. We compared their rates of BK infection with 45 historical well-matched rapid metabolizers who remained on IR tacrolimus. Bk urine and serum PCR were monitored at specified time points up to 12 months following transplantation. RESULTS: Most patients in the study cohort were deceased donor kidney transplant recipients, mean age 50 years, and predominantly of African American ethnicity. The incidences of BK viremia (18.6% vs 33.3%) and BK viruria (41.9% vs 46.7%) were numerically lower in the Envarsus-converted group as compared to patients remaining on IR tacrolimus at 1 year after transplantation. The cumulative risk ratio for the development of BK viremia for the Envarsus group was 0.53 compared to the IR tacrolimus group. CONCLUSIONS: The study did not demonstrate a significant reduction in the incidence of BK virus infection in the Envarsus-converted group as compared to the IR tacrolimus group, although there was a numerical reduction. The study likely lacked sufficient statistical powered to detect a difference.