The composite primary endpoint was similar between treatment groups: 22 of 126 (17.5%) in the AD group vs. 17 of 121 (14.1%) in the FD group (P=0.46). There was no difference between the two groups in terms of the proportion of patients with biopsy-proven acute rejection (BPAR) at 3 months or SCAR as determined by protocol biopsy at month 3 (Table 2). These findings were confirmed at 1 year with a similar rate of BPAR (24.6% in the AD group vs. 14.9% in the FD group; P=0.06) and of SCAR (9.3% in the AD group vs. 10% in the FD group; P=0.84) between treatment groups. At 1 year, a similar proportion of protocol biopsies presented as chronic lesions (interstitial fibrosis and tubular atrophy ≥1: 47.5% in the AD group vs. 52.5% in the FD group; P=0.72), and renal function was also similar (mean estimated creatinine clearance: 50.8±16.3 mL/min/1.73 m2 in the AD group and 48.9±18.2 mL/min/1.73 m2 in the FD group). Patient and graft 1-year survival rates were excellent in both groups: 98% and 95%, respectively; six grafts were lost in each group, with the majority due to early thrombosis.
The overall incidence of adverse events was similar for the two treatment regimens. In particular, there was no difference in the incidence or severity of CMV, herpes, or bacterial infections. Furthermore, the incidence of diarrhea, anemia, or leukopenia was not different between patients in the AD and FD groups (Table 3). The percentage of patients who had MMF dose adaptation due to an adverse event was significantly greater in the AD than in the FD group (58.7% vs. 42.2%, respectively; P=0.009). However, the number of patients who discontinued MMF between baseline and week 52 was similar between groups (11.1% in the AD group; 12.4% in the FD group; P=0.754).
Steroid withdrawal was possible at day 7 in 94% of patients in both groups. At 1 year, 67% of patients in the AD group and 69% in the FD group were still free of steroids. Apart from suspected rejections (biopsy proven or not), the main reason for reintroduction of steroids in both groups was borderline lesion treatment: at the end of the study, 21 patients had been treated in AD group versus 28 in the FD group. The incidence of adverse events associated with corticosteroids as de novo diabetes mellitus was low. One-year blood pressure was identical in the two groups: 137/79 mm Hg vs. 137/78 mm Hg.
We conducted this randomized, multicenter trial to assess the benefit of the combination of early corticosteroid withdrawal with intensified MMF dosing and therapeutic drug monitoring (TDM) in kidney transplant recipients receiving CsA maintenance immunosuppression. Two recent systematic reviews confirmed that early steroid withdrawal strategies increase the risk of acute rejection (3, 4) Our results indicate that early steroid withdrawal (<7 days) is feasible and safe in selected patients with a 70% success at 1 year. In fact, only 39 patients in both groups (15.8%) experienced BPAR or SCAR at 3 months posttransplant. Compared with previous published studies (13, 14), this is the first trial that has shown a low acute rejection rate after early steroid withdrawal in low-risk patients receiving anti-interleukin-2-receptor-α (IL-2Rα) induction, CsA, and MMF. In the Freedom study, with a similar immunosuppressive regimen, the 3 months rate of BPAR was 18.3%, but SCAR were not analyzed (14). Per the protocol statistical hypothesis, we estimated that the incidence of SCAR would range between 15% and 25% at the 3-month protocol biopsy depending on the treatment arm. This hypothesis was based on the previously reported data, indicating that the incidence of SCAR varied from 15% to 30% during the 3 months posttransplant in patients receiving CsA (15–17). SCAR is defined by the presence of tubulointerstitial inflammatory infiltrates seen on biopsy of renal transplants with stable function. The presence of SCAR has been associated with the progression of chronic tubulointerstitial damage (18) and a reduction in graft survival (19). In our study, contrary to the hypothesis, a SCAR was a rare clinical event in both the AD and FD treatment groups at 3 months (4% vs. 2.5%, respectively) and 1 year (9.3% vs. 10%, respectively). This interesting result indicates that the rate of SCAR probably is overestimated, at least in low-risk patients. Furthermore, in these recipients, the steroids were successfully withdrawn 2 weeks after transplantation. At 1 year, approximately 70% of patients were still free of steroids with a mean estimated creatinine clearance of 49 mL/min and a lower incidence of de novo diabetes and hypertension than in patients receiving corticosteroids in other studies (13, 20).
It has been clearly established that MPA exposure correlates with clinical efficacy in renal transplantation (11, 21), and a therapeutic window for MPA AUC seems to range from 30 to 60 mg · h/L (22) early after transplantation. At the same time, the pharmacokinetics of MPA is characterized by a high between-subject and within-subject variability in part resulting from a low bioavailability early after transplantation (23). Moreover, 50% of patients receiving CsA and 25% of patients receiving tacrolimus (24) and 2 g/d of MMF are underexposed to MPA within the first weeks posttransplant. To overcome this early MPA underexposure, especially in CsA-treated patients, an initial intensified MMF dosing regimen followed by TDM is an approach to consider. In our study, we evaluated this combined strategy: 3 g of MMF for 10 days with subsequent TDM. The results have shown that MPA exposures were significantly higher in the AD group at week 2 and week 6 but similar in both groups at week 12 and thereafter. It is interesting to note that a 50% MMF dose increase only provided a 20% increase in MPA exposure. In contrast, using the same approach in patients receiving tacrolimus, the CLEAR study group (25) reported a 50% increase in MPA exposure. This illustrates that the dose proportionality of MMF in the early period after transplantation is imperfect when MMF is combined with CsA. Furthermore, according to the FDCC study, early adequate exposure (day 3 or 5 posttransplant) is a better predictor of acute rejection (24). Consequently, an initial dose of 4 g for the first 10 days would have been more appropriate in patients receiving CsA. In our study, therapeutic concentrations were successfully achieved by TDM in 65% of patients at week 2 and in 80% at week 6. TDM started at week 2 yielded MMF doses ranging from 1 to 4 g/d at each visit thereafter and significantly reduced the interpatient variability at the week 26 and 52 visits, although, in the FD group, the AUC was more variable than in the AD group. Approximately 14% of patients in the AD group required an MMF dose more than or equal to 3g/d at 1 year after transplantation to reach the therapeutic window. These data suggest that therapeutic concentrations can be achieved easily by the combined strategy of intensified dosing of MMF and subsequent TDM.
In the present study, there was a high rate of physician compliance with the prespecified MMF dose adjustments. Adjustments of the MMF dose were made rigorously in more than 70% of the patients over the study period according to the MPA AUC values measured.
Despite a higher MPA exposure in the AD group, the primary endpoint (the proportion of patients experiencing BPAR or with SCAR identified on the 3-month protocol biopsy) was low and similar between the groups. This suggests that the low rate of BPAR and SCAR at 3 months could not be optimized by TDM in these patients. Still, for recruitment purposes and feasibility, most of the MPA monitoring studies have been performed in low and even very low-risk patients (12, 25, 26). This can explain the controversial results of previous studies. In the APOMYGRE study (12), higher MPA exposure was associated with a reduction of the incidence of acute rejection. In the CLEAR study (25), there was a trend for fewer BPAR episodes in the intensified dosing group (10.2% vs. 25%; P=0.06). In the Fixed-dose Concentration-controlled trial (24), this relationship was less obvious, but a posthoc analysis showed that higher risk patients receiving tacrolimus had rejection rates 2.5-fold more frequently if their day 3 MPA AUC was less than 30 mg · hr/L (27). Taken together, these results suggest that MPA TDM is essential in patients with high immunologic risk, in patients to be treated with calcineurin inhibitor minimization or avoidance protocols and in regimens with steroid avoidance or early withdrawal. For these recipients, greater MPA exposure than currently recommended as the therapeutic window may be needed.
In summary, in renal transplanted patients with low immunological risk, MMF associated with anti-IL-2Rα antibody induction and CsA allows early corticosteroid discontinuation with good tolerability and safety outcomes. MMF 3 g/d administered as maintenance immunosuppression with CsA and MPA TDM guarantees a higher MPA exposure with 80% of patients achieving therapeutic concentrations 3 weeks after transplantation. MMF doses necessary to achieve therapeutic concentrations vary between individuals, suggesting that TDM should be used. In this study, the rates of SCAR at 3 months and 1 year were unexpectedly low and not improved by TDM of MPA.
MATERIALS AND METHODS
Study Design and Conduct
In this 12-month, prospective, open-label, multicenter study (OPERA trial), de novo renal transplant recipients received anti-IL-2Rα antibody induction followed by a short course of corticosteroid therapy to day 7 posttransplant, MMF (AD or FD) and CsA (C2 monitoring). The study was conducted in 17 centers in France in full compliance with the amended Declaration of Helsinki and the International Conference on Harmonization Harmonized Tripartite Guideline for Good Clinical Practices in the European Community (CPMP/ICH/135/95) and was approved by the Independent Ethics Committee and by the relevant authorities (EUDRACT 2006-000352-41). All study participants provided written informed consent.
Patients aged 18 to 75 years with low immunologic risk defined as receiving a primary kidney transplant from a deceased or living donor with a current (most recent before transplantation) panel reactive antibody level of 0% and a cold ischemia time less than or equal to 36 hr were eligible for study entry. Key exclusion criteria were receipt of a kidney from a donor older than 70 years, a previous kidney transplant, a combined transplant, and patients with any disease requiring corticosteroid therapy.
Randomization and Treatment
Eligible patients were randomized into two treatment groups in a 1:1 ratio using a centralized validated system based on a minimization method and were stratified into groups according to center, graft origin, and donor age. All patients received an anti-IL-2R-α antibody, basiliximab, or daclizumab, as induction therapy. CsA was introduced within 72 hr posttransplantation with the dose adjusted to maintain C2 within the following predefined ranges: 1000 to 1500 ng/mL from day 0 to week 4; 800 to 1200 ng/mL from weeks 4 to 12; 500 to 800 ng/mL from weeks 12 to 52.
In the AD treatment group, MMF (CellCept; F. Hoffmann-La Roche, Ltd.) was initiated preoperatively at 3 g/d and then adjusted to a target MPA AUC of 40 mg · h/L. Patients in the FD group received MMF 2 g/d, and investigators were blinded to MPA AUC assessments. If needed, the MMF dose could be adjusted per clinical experience. In both treatment groups, MPA concentrations were measured by high-performance liquid chromatography at weeks 2, 6, 12, 26, and 52. The MPA AUC0–12h was calculated using Bayesian estimations specific for MMF and based on plasma samples drawn at 20 min, 1 and 3 hr after administration (28).
Until day 7 posttransplant, patients in both treatment groups received a corticosteroid comprising intravenous methylprednisolone 500 mg perioperatively followed by oral prednisolone 0.5 mg/kg/d to a maximum of 60 mg/d. Acute rejection was treated with intravenous methylprednisolone according to local practice. Use of antithymocyte antibodies was permitted in cases of steroid-resistant or vascular rejection.
Local practice dictated Pneumocystis jiroveci pneumonia and CMV prophylaxis. CMV prophylaxis for D+/R− patients was mandatory and was in accordance with each center's usual practice.
The primary efficacy endpoint, a composite endpoint at 3 months posttransplant, was the proportion of patients experiencing BPAR on indicated biopsies and those with SCAR identified on the 3-month protocol biopsy. Biopsies were considered clinically indicated when performed in the setting of an increase in serum creatinine level more than 10% from baseline. Protocol biopsies were scheduled at month 3 and 1 year posttransplant. All biopsies were assessed locally, reviewed by a central reading anatomopathologist and classified by an expert reading board according to the 2007 Banff grading schema (29). The secondary efficacy endpoints were the proportion of patients with a BPAR or a SCAR episode at 1 year, renal function as creatinine clearance estimated by the simplified Modification of Diet in Renal Disease method (30) and graft and patient survival.
After initial screening at baseline (day 0), patients returned to the study site for assessments at weeks 2, 4, 6, 12, 16, 26, 39, and 52. All adverse events were recorded irrespective of severity or relationship to the study medication, with special attention to the following: anemia (hemoglobin level <10 g/dL, excluding the first month posttransplant or evident blood loss); leukopenia (total white cell count <2×109/mL); gastrointestinal adverse events (diarrhea, constipation, anorexia, abdominal pain, nausea, or vomiting); and infections (including CMV and herpes). New onset diabetes mellitus was defined by the 2003 diagnostic criteria for the American Diabetes Association or de novo prescription of hypoglycemic therapy (31).
The primary efficacy analysis population, the intention-to-treat population, included all patients who were randomized, who received at least one dose of MMF and who underwent kidney transplantation. The safety population included all randomized patients who received at least one dose of study medication.
Descriptive statistics summarized demographic and baseline variables. The principal efficacy analysis compared the composite endpoint during the first 3 months between the two groups using a chi-square test. Between-group comparisons for secondary endpoints were performed using Student's t test, variance analysis, Wilcoxon's rank-sum test, the chi-square, or Fisher's exact test, as appropriate. Safety was analyzed in terms of adverse events, changes in vital signs (weight, clinical signs), and laboratory test results. Statistical analyses were performed with a two-sided significance level of 5% using SAS software version 9.1 (SAS Institute, Cary, NC).
The sample size was calculated to provide 90% power with α=5% (two-sided) to detect a between-group difference of 20% in the proportion of patients with BPAR or SCAR during the first 3 months of treatment favoring the AD treatment group (AD group: 20% comprised 5% of BPAR and 15% of SCAR episodes vs. the FD group: 40% comprised 15% of BPAR and 25% of SCAR episode). According to these hypotheses, 128 patients per group were to be randomized.
The authors acknowledge the contributions made by all physicians and site study staff, all local anatomopathologists, the centralized reading board in particular L.H. Noël, all local laboratory scientists, the Limoges Inserm Unit for Mycophenolic Acid Therapeutic Drug Monitoring in particular P. Marquet, the study advisory board, the DSMB, the project team for study management, and Francoise Allano (Roche SAS, France) for her great contribution to the study. They also thank the Zola Associates, Englewood Cliffs, NJ, for the editorial support.
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Early corticosteroid withdrawal; Kidney transplantation; Mycophenolate mofetil; Therapeutic drug monitoring
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