The objectives of this study were to compare the PK and safety profile of once-daily LCPT or PR-Tac in adult de-novo kidney transplant recipients followed for 28 days after transplantation.
Study Population
Adult (≥ 18 years), white, de novo recipients of a living or deceased donor kidney transplant, including patients undergoing a second kidney transplant, with a body mass index (BMI) between 15 and 35 kg/m2, and who provided written informed consent were included in this analysis. Recipients of other transplants and patients who were already on immunosuppressants the day before transplantation were excluded.
Study Design and Sample Collection
This randomized, parallel-group, open-label, multicenter study (NCT02500212) was conducted at seven transplantation centers in France. Eligible patients were randomized 1:1 to either LCPT [Envarsus® 0.75 mg, 1 mg and 4 mg tablets (Veloxis Pharmaceuticals, Copenhagen, Denmark)] or PR-Tac [Advagraf® 0.5 mg, 1 mg, 3 mg, 5 mg capsules (Astellas Ireland Co., Ltd)] once-daily in the morning, initiated within 24 h after surgery, at starting doses of 0.17 mg/kg/day for LCPT and 0.20 mg/kg/day for PR-Tac. Starting doses were according to the respective EU summary of product characteristics [8, 20] and were maintained until day 3; thereafter, doses of LCPT and PR-Tac could be adjusted on the scheduled days (days 4, 8, 15 and 22) according to the trough levels measured on the previous day. Adjustments were performed with the aim of targeting predefined ranges of 5–15 ng/ml from days 2 to 15 and 5–10 ng/ml from days 16 to 28 (Fig. 1). A single whole-blood sample was collected at screening for CYP3A5 genotyping to identify single nucleotide polymorphisms (CYP3A5 *1/*1, *1/*3 and *3/*3). To avoid information on the patient genotype influencing dose adjustments, these data were disclosed at the end of the study. To study the PK profiles of tacrolimus in whole blood, 13 blood samples were collected in K2EDTA tubes pre-dose and 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0, 8.0, 12.0, 16.0, 20.0 and 24.0 h after the morning dose on days 1, 3, 7 and 14. Tacrolimus trough levels were assessed in whole blood every day from day 2 to 8 and then on days 14, 15, 21 and 28 (Fig. 1). More detailed methods for genotyping and the assessment of tacrolimus whole-blood trough levels are provided in the Online Resource.
Compliance to tacrolimus prescription was evaluated based on the counts of tablets/capsules returned by the patients to each study visit and the patient’s diary used for recording drug intake starting from hospital discharge until the end of the study.
Concomitant immunosuppressive drugs were standardized to basiliximab (Simulect®, Novartis Pharmaceutical Corp., NJ, USA; 20 mg intravenously on day 0 and 4), mycophenolate mofetil (CellCept®, Hoffmann-La Roche Ltd., Mississauga, Ontario, Canada; 1 g orally twice daily until day 14 ± 2 days; 0.5 g orally twice daily until day 28 ± 2 days) and corticosteroids (intravenous methylprednisone: 10 mg/kg on day 0, 1 mg/kg on days 1 and 2; oral prednisone: 0.5 mg/kg on days 3–7 ± 2 days and then 0.3 mg/kg until day 15 ± 2 days and 10 mg until 28 ± 2 days).
A list of medications known to significantly interfere with the metabolism of tacrolimus was provided with the study protocol with the recommendation to avoid such medications unless clinically necessary.
PK Outcomes
The PK population was defined as all randomized subjects in the safety population (who had received ≥ one dose of study treatment) excluding subjects without any valid PK measurement. Patients with major protocol deviations significantly affecting PK were excluded from PK analysis for the period of the deviation, but not from the PK population.
All PK variables were calculated using non-compartmental analysis (NCA) with Phoenix WinNonlin 7.0 (Certara, Inc., Princeton, NJ, USA). The PK outcomes of this study were the ratio between the area under the curve from 0 to 24 h and daily dose (AUC0–24h)/daily dose) as an index of relative oral bioavailability, percentage peak-to-trough fluctuation [maximum whole-blood drug concentration (Cmax) − minimum whole-blood drug concentration (Cmin) × 100/average whole-blood drug concentration (Cavg)] and time to peak concentration (tmax) on days 1, 3, 7 and 14. Additional outcomes included AUC0– 24h, Cmax, Cavg and Cmin on days 1, 3, 7 and 14; trough levels [whole-blood trough drug concentration 24 h post dose (C24h)] daily from day 2 to day 8 and on days 14, 15, 21 and 28; proportion of patients with trough levels lower than, within and higher than the target range; proportion of patients with trough levels within the target range between day 2 to 4; and number of dose adjustments.
Safety Assessments
The safety population was defined as all randomized subjects who had received ≥ one dose of study treatment.
Safety parameters included vital signs, weight, BMI, serum creatinine, estimated glomerular filtration rate (eGFR; calculated according to the chronic Kidney Disease Epidemiology Collaboration creatinine equation [21]), blood chemistry, hematology, urinalysis, incidence of delayed graft function (DGF; defined as hemodialysis within 1 week following transplant or serum creatinine > 5 mg/dl by day 7), AEs, serious adverse events, adverse drug reactions (ADRs), serious ADRs, severe AEs, AEs leading to study discontinuation and AEs leading to death. Safety laboratory analyses were conducted at each site.
Statistical Analysis
No formal sample size calculations were undertaken. A sample size of 32 evaluable patients per treatment group was considered sufficient to characterize the PK of the study drugs. Based on a dropout rate of ~ 12%, 72 participants were planned (36 per treatment group).
All statistical analyses were performed using SAS 9.3 (SAS Institute Inc., Cary, NC, USA). Tacrolimus AUC0–24, C24h, Cmax, Cavg, Cmin, tmax, percentage peak-to-trough fluctuation [(Cmax − Cmin) × 100/Cavg] and AUC0–24h/daily dose were summarized using descriptive statistics by treatment and visit. Fluctuation (%) and AUC0–24h/daily dose at day 3, day 7 and day 14 were log-transformed to the natural logarithmic scale and then analyzed using an analysis of variance (ANOVA) model with treatment as a fixed effect. Alpha was set at 0.05, but the ratios of adjusted geometric means (GM) between the two groups were provided with 90% CIs. Due to the exploratory nature of the study, comparisons were done independently at three different time points without adjustment for any covariates and without accounting for repeated measures and multiple comparisons.
Tmax at day 3, day 7 and day 14 was analyzed using the Wilcoxon signed-rank test based on untransformed data. Hodges-Lehman estimates with 90% two-sided CIs for the median difference between the two treatments were applied.
The proportion of patients with tacrolimus C24h within the target range at day 2 and maintained within this range at day 3 and 4 was calculated by treatment. Differences between treatments were evaluated using Fisher’s exact test at the 0.05 significance level, with 95% CIs.
Compliance with Ethical Guidelines
All procedures performed in studies involving human participants were according to the clinical study protocol, the current International Council for Harmonization Good Clinical Practice guidelines, all local guidelines and the Declaration of Helsinki (1964 and amendments). The independent ethics committee/institutional research board for this study was the Committee for the Protection of Persons South Mediterranean V, CHU de Nice-Hôpital De Cimiez.
Informed consent was obtained from all individual participants included in the study. A specific Patient Information Sheet-Informed Consent Form for genotyping tests was obtained.