(764) - Lower Dose Tacrolimus Monotherapy in Heart Transplant Patients: Is It Safe

Abstract

Monotherapy with CNI alone has been found to be efficacious as seen in the previous published TICTAC trial. In this trial, patients were maintained on a higher tacrolimus level in the range of 8-12 ng/ml which resulted in a higher serum creatinine level. It has not been established as to whether lower blood levels of tacrolimus (5-8 ng/ml) in monotherapy leaves these patients adequately immunosuppressed. The Cylex test allows us to assess how immunosuppressed are heart transplant patients. The Cylex test measures ATP production in stimulated CD4 T-cells. Adequate immunosuppression should result in a targeted ATP level between 200-550 ATP ng/ml. Lower scores correlate to increased immunosuppressed state. We sought to assess whether patients on lower dose tacrolimus monotherapy using the Cylex score are indeed adequately immunosuppressed. Between 2008 - 2013 we identified 8 patients on tacrolimus therapy for at least 1 month. The average time from transplant to initiation on monotherapy was 25±22 months. Cylex scores within 2 months after transition to monotherapy were assessed. The reasons for monotherapy included leukopenia, severe diabetes, recurrent infection. In this cohort, Cylex scores averaged 234 ± 94 ATP ng/ml with concomitant average tacrolimus trough level of 5.2 ± 1.5 ng/ml. For these patients on monotherapy there was complete freedom from subsequent treated rejection and infection within 1 year. Patients on monotherapy appear to be adequately immunosuppressed (by Cylex score) on a relatively low level of tacrolimus without clinical events. The Cylex score appears to be helpful in this unique population where minimal immunosuppression is required.