Randomized, International Study of Cyclosporine Microemulsion Absorption Profiling in Renal Transplantation with Basiliximab Immunoprophylaxis

Abstract

Increasing information suggests that absorption profiling may be superior to trough level monitoring for optimal concentration control of cyclosporine microemulsion (Neoral) therapy, and that CsA exposure early post-transplant may correlate significantly with reduced risk of acute graft rejection. This randomized, prospective, multicenter international concentration-controlled study was conducted in 21 renal transplant centers in 8 countries to test and compare the clinical feasibility, functionality, accuracy, precision and prediction of rejection by cyclosporine microemulsion absorption profiling to conventional trough-level drug monitoring. Primary or second renal allograft recipients treated with basiliximab, cyclosporine microemulsion and prednisone immunosuppression were randomized to two study groups in which cyclosporine microemulsion therapy was monitored using a multipointalgorithm or by trough levels. The two study arms were comparable in terms of baseline characteristics, treatment and clinical outcomes. Treatment failure, consisting of acute rejection, graft loss or death, occurred with equal incidence in the two groups (30% and 33%, respectively). Diagnostic feasibility, measured as the proportion of samples obtained within the designated time window, was marginally lower in area under the time-concentration curve (AUC) than in trough groups, but the therapeutic accuracy and precision were comparable or superior in the AUC group. Cox regression analysis performed across study groups showed a highly significant correlation between the predicted probability of acute rejection and cyclosporine (CsA) exposure measured by AUC over the entire 12-h dosage interval (AUC[0-12]) (p = 0.0068), AUC over the first 4 h of the 12-h dosage interval (AUC[0-4]) (p = 0.0014) or 2h post-dose (C2) CsA level (p = 0.0027). Day 3 dose- and weight-corrected C2 values (EMIT equivalent) separated patients into low (< 200 microg/L/mg/kg dose), intermediate (200-350 microg/L/mg/kg dose) and high absorber categories (> 350 microg/L/mg/kg dose), defining those at greatest risk. Within these categories, C2 values above approximately 1500 microg/L by day 3 post-transplant were associated with the lowest predicted probability of rejection. Comparable analysis by Cox regression using C0 levels did notreach statistical significance. Absorption profiling is a feasible, accurate and precise method for monitoring cyclosporine microemulsion therapy in clinical practice and, as shown in the companion article, may be simplified by the use of single-point C2 concentrations which accurately predict individual AUC[0-4] exposure levels. Both cyclosporine microemulsion relative absorption (i.e. dose- and weight-corrected exposure) and CsA exposure (measured by predicted AUC or C2 levels) are closely correlated with the risk of rejection, and define patients at high and low risk of acute graft rejection. Trough (C0) levels are not closely correlated with either CsA exposure or rejection risk, and should not be considered reliable for monitoring cyclosporine microemulsion therapy.