Hepatitis C virus therapy, hepatocyte drug metabolism, and risk for acute cellular rejection

We recently reported on a series of patients who experienced acute cellular rejection (ACR) during the treatment of hepatitis C virus (HCV) infection in our posttransplantation cohort. Our hypothesis is that HCV clearance improves hepatic microsomal function, which in turn results in lower trough cyclosporine (CyA) and tacrolimus (TAC) levels, predisposing the patient to ACR. Records of all patients receiving transplants for HCV infection at our center from 1993 to June 2002 were reviewed. Two hundred three patients were identified. Thirty-seven patients (18%) were treated with interferon-hased therapies in combination with ribavirin. Twelve patients were selected for analysis because they became HCV RNA negative during therapy, and 18 patients with no antiviral response were selected as controls (7 other patients had incomplete data or had switched from one immunosuppression [IS) therapy to the other). Baseline IS levels were compared with the first available level after documented negative HCV RNA results in the study group and the last on-treatment IS level in the control group. We also compared frequency and percentage of change in IS levels during therapy. Mean decline in CyA trough levels in the study group was from 187.28 ng/mL at baseline to 118.14 ng/mL immediately after becoming HCV RNA negative (-36.92%; P = .018). Mean decline in TAC levels was from 7.34 ng/mL at baseline to 5.02 ng/mL immediately after becoming HCV RNA negative (-29.17%; P = .044). Overall, 6 of 12 patients who cleared HCV RNA during therapy experienced ACR; 1 patient died as a result of ACR. Using percentage of decrease from baseline IS level, we combined results for patients administered CyA and TAC and found a significant decrease from baseline IS levels in responders (-31.8% after HCV RNA clearance on treatment; P = .0001). Nonresponders experienced a 0.98% decline in IS levels while on treatment, and the difference was significant compared with the change in the responder group (P = .006). A greater proportion of antiviral therapy responders also experienced trough IS levels 20% less than baseline than nonresponder controls during therapy (P = .0006). In conclusion, IS levels decreased significantly in patients responding favorably to anti-HCV therapy. This decrease in IS levels may have a key role in predisposing these patients to ACR.