This open-label, randomized (1:1), double arm, multicenter, non-inferiority, conversion study was conducted at three transplant centers in Korea from April 2010 to June 2012. The study protocol was approved by the Institutional Review Board at all participating centers to ensure that study procedures were in accord with the Helsinki Declaration.

The study inclusion criteria were an age between 20 and 65 years and recipient of a primary kidney transplant from a deceased or living donor between 15 and 65 years of age. The study exclusion criteria were receipt or scheduled receipt of an organ transplant other than a kidney or scheduled receipt of a kidney from a non-heart beating or ABO blood group incompatible or lymphocyte cross match positive donor.

All recipients were administered twice-daily tacrolimus (Prograf®, Astellas Pharma Inc.,Tokyo, Japan) with prednisolone and mycophenolate mofetil until 1 month post-transplantation. Methyl-prednisolone was injected intravenously with the following doses: 500 mg on the day of operation and 250 mg on the day after, and corticosteroids were tapered to a maintenance dose of more than 5 mg a day (prednisolone or equivalent) orally twice or once a day. Target dose of mycophenolate mofetil was 1000-2000 mg/day, orally twice a day, for both groups throughout the study period. Tacrolimus (Prograf®) was initiated at 0.05-0.1 mg/kg, starting on the day before transplantation. Within a month after transplantation, dosages were individually adjusted to achieve a trough blood level between 5 and 15 ng/mL. Patients in the investigational group were converted to the same milligram-for-milligram daily dose of once-daily tacrolimus (Advagraf®, Astellas Pharma Inc., Tokyo, Japan) on the 28th day post-transplantation and were then maintained at tacrolimus trough levels of 3 to 12 ng/mL throughout the study. The patients in the control group continued to take twice-daily tacrolimus (Prograf®) at targeted blood trough levels of 3 to 12 ng/mL from 1 month post-transplantation.

Efficacy and safety analyses were performed using a modified intent-to-treat population composed of all randomized patients that received at least one dose of study drug. A composite primary efficacy endpoint was assessed: that is, efficacy failure rate at 6 months post-transplantation, including any mortality, graft failure (return to dialysis for >30 days or re-transplant), treatment for biopsy-confirmed acute rejection (BCAR), or loss to follow-up. The latter was defined as a lack of follow-up information for at least 3 months (90 days). Secondary endpoints incuded patient and graft survival rates at 6 months, incidences of BCAR at 1 and 6 months, estimated glomerular filtration rate (eGFR) as determined using the Nankivell method at 6 months,10 the amount of proteinuria in 24-hour urine at 6 months, creatinine clearance in 24-hour urine at 6 months, and the immunosuppressant therapy barrier scale (ITBS). Adverse events (AE) were recorded and coded during the study period. An adverse event was defined as any untoward medical occurrence, including an exacerbation of a per-existing condition, in a patient in a clinical investigation who received a pharmaceutical product. The event did not necessarily have a causal relationship with this treatment. The severity grade of AE was defined as: 1) mild, usually transient in nature and generally not interfering with normal activities; 2) moderate, sufficiently discomforting to interfere with normal activities; and 3) severe, prevents normal activities. Serious adverse events (SAEs) were defined as any AE undesirable signs, symptoms, or medical conditions that met any one of the following criteria: 1) was fatal or life-threatening, 2) resulted in persistent or significant disability/incapacity, 3) required hospitalization or prolongation of existing hospitalization, 4) was a congenital anomaly/birth defect, or 5) was an important medical event that might jeopardize the patient and might require medical or surgical intervention to prevent one of the outcomes listed above. Differences between adverse event incidences and the incidences of predefined potentially clinically significant laboratory values in the two study groups were assessed and analyzed.

ITBS is a 13-item scale that measures barriers to immunosuppressant adherence in transplant patients. ITBS was measured at 6 months post-transplantation. Each item was measured on a 5-point scale (1=strongly disagree, to 5=strongly agree) assessing respondent agreement with each statement. Items consisted of questions about how often: 1) they forgot to take their immunosuppressants, 2) were careless about taking their immunosuppressants, 3) stopped taking their immunosuppressants because they felt worse, and 4) missed taking their immunosuppressants for any reason.11

Study visits took place prior to transplantation (baseline) and at 1, 2, 4, and 6 months post-transplantation. At each visit, a complete physical examination was performed and laboratory values concerning kidney, liver, hematology, proteinuria, and tacrolimus in blood were measured. Blood pressure, weight, and any problems between visits were documented. All adverse and severe adverse events were documented.

All assessments of non-inferiority were made using a pre-specified margin of 25% with a 0.05 level of significance. Frequency distributions were plotted for categorical variables. The χ² test or Fisher's exact test were used to compare the two treatment groups. Descriptive statistics were analyzed as continuous variables using Student's t-test. Continuous variables were expressed as means±standard deviations.

Based on reference to a previous study, the efficacy failure rates at post-transplant 6 months for the control and investigational groups were 14.0% and 15.1%, respectively.12 A sample size of 25 patients per each treatment group was calculated to have 80% power, 25% non-inferiority margin, and a 10% drop out rate. To allow for discontinuations, 60 patients (n=30 per group) were initially randomly assigned.

In total, 60 patients were enrolled in this study and randomized to either the investigational group (n=29) or the control group (n=31). Fifty-four (90.0%) patients remained on study medication at 6 months post-transplantation. One patient (3.4%) in the investigational group and 5 patients (16.1%) in the control group prematurely discontinued medication during follow-up. The reasons for premature discontinuations were adverse events (n=1), withdrawal of consent (n=3), graft loss (n=1), and protocol deviation (n=1). Donor and recipient characteristics were comparable in the two study groups (Table 1).

Composite efficacy failure rates including the incidence of biopsy-confirmed acute rejection until 6 months post-transplantation were 0% in the investigational group and 10.7% in the control group, and the investigational group was statistically non-inferior to the control group. One graft loss in the control group and no patient death in either group were recorded. No statistical differences were observed between the groups in terms of Kaplan-Meier estimates of patient proportions free of composite efficacy failure at 6 months post-transplantation (100% in the investigational group and 89.3% in the control group; p=0.236).

The incidences of treated BCAR within 6 months of transplantation were not significantly different between the two groups: 0% in the investigational group and 10.7% in the control group (p=0.075), which was statistically non-inferior to the investigational group.

Mean eGFRs (by the Nankivell method) in the investigational group were 40.2±6.9 mL/min/1.73 m² at 1 month, 41.7±6.3 mL/min/1.73 m² at 2 months, 41.2±6.0 mL/min/1.73 m² at 4 months, and 41.8±6.1 mL/min/1.73 m² at 6 months post-transplantation, and in the control group were 41.0±5.2 mL/min/1.73 m² at 1 month, 41.6±5.3 mL/min/1.73 m² at 2 months, 42.5±5.9 mL/min/1.73 m² at 4 months, and 41.9±5.8 mL/min/1.73 m² at 6 months post-transplantation. Group renal functions were not statistically different at any time (p>0.05).

Measured creatinine clearance by 24-hour urine collection at 6 months post-transplantation were similar between the two groups (64.1±21.5 mL/min/1.73 m² in the investigational group and 63.64±21.3 mL/min/1.73 m² in the control group; p=0.933).

Excreted protein amounts at 6 months post-transplantation were similar at 104.3±84.4 and 91.4±83.4 mg per day in the investigational and control groups (p=0.589).

At follow-up visits, most subjects did not require dose adjustment. The mean daily doses and whole blood concentrations of tacrolimus are summarized in Table 2.

Overall incidences of adverse events at 1 month post-transplantation were comparable between the two groups (71.4% of patients in the investigational group and 75.0% in the control group; p=0.763), and incidences of SAEs were also comparable (14.7% in the investigational group and 15.5% in the control group; p=0.415). The incidences of adverse events by system organ class were generally similar between the groups, and most were mild-to-moderate in severity (Table 3).

The summed score of the 13 items of the ITBS (highest value possible 65 and lowest 13) of the investigational group at 6 months post-transplantation was 17.5±3.1, which was comparable to that of the control group (18.4±4.0; p=0.345).