*Purpose: Early achievement of therapeutic tacrolimus concentrations has been associated with reduced rates of acute rejection. A prospective, randomized, controlled study demonstrated safe and efficacious use of LCPT in de novo kidney transplantation. The purpose of this analysis is to evaluate trough level attainment in the immediate post-transplant setting for LCPT vs IR-Tac.

*Methods: A post-hoc analysis of a Phase III clinical trial was conducted. Within 48 hours of transplantation patients were randomized to receive LCPT starting at 0.17 mg/kg/day or IR-Tac 0.1 mg/kg/day. Subsequent doses were adjusted to maintain target trough levels of 6-11ng/mL for the first 30 days. Patients were divided into low, medium and high CD ratio (calculated at 1 month) to estimate rapid, intermediate, and slow metabolizers, respectively. The proportion of patients below, within, and above target range were determined for days 2-5 post-tacrolimus initiation.

*Results: A total of 543 patients were randomized in the study. Proportion of patients below, within, and above target range are shown for all patients and by CD ratio group in Figure 1. After initial dosing, 24.7% of IR-Tac patients were within target range, with a predominance of patients (61.8%) being below range. While 33.7% of LCPT patients were within range after initial dosing, more patients demonstrated concentrations above target range (39.8%). A similar pattern was seen across intermediate (P33-P67) and slow (CD>P67) metabolizers. Of note, in rapid metabolizers (CD*Conclusions: These data suggest that LCPT at a starting dose of 0.17 mg/kg/day results in a greater proportion of patients at or above target tacrolimus levels during the early days post-transplant compared IR-Tac at 0.1 mg/kg/day. In particular, very few rapid metabolizers, who are historically difficult to achieve therapeutic concentrations in, exhibited sub-target levels using this dosing approach for LCPT. These findings may assist providers with helpful information to guide tacrolimus therapy in patients where early tacrolimus exposure is desired.

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