Because outcomes after heart and lung transplantation have improved, extended posttransplant survival times have revealed the nephrotoxic toll of long-term immunosuppression based on calcineurin inhibitors (CNIs) (1–3). Thus, the improvement in cardiac and lung graft survival rates achieved after the introduction of CNI therapy is, paradoxically, countered by the impact of CNI-related nephrotoxicity. In kidney transplantation, Nankivell et al. (4) have shown that chronic and irreversible CNI-related nephrotoxicity continues to develop progressively over time with more severe progression predicted by higher CNI exposure. Strategies to reduce maintenance exposure to CNIs are becoming increasingly appealing as clinicians attempt to maximize long-term patient survival and quality of life after heart or lung transplantation.
The mammalian target of rapamycin (mTOR) inhibitor everolimus has a synergistic mode of action to CNI agents (5), such that concomitant administration of everolimus with CNI therapy permits a substantial reduction in CNI exposure without loss of efficacy (6). In maintenance thoracic transplant patients, data concerning the use of everolimus to permit a lower level of CNI exposure—and the implications for renal function—have to date been restricted to a single-arm pilot study (7, 8) and single-center trials (9–11).
The Nordic Certican Trial in Heart and Lung Transplantation trial was a randomized, open-label, multicenter study undertaken with the objective of establishing whether introduction of everolimus with a simultaneous protocol-specified reduction in CNI exposure would improve renal function in maintenance heart or lung transplant recipients with renal impairment (12). On completion of the first 12 months of the study, patients were enrolled in a further 12-month follow-up period with the objective of assessing whether renal benefits were preserved and to monitor the safety profile of each treatment arm. The findings of 24 months after introduction of everolimus are described here.
The first patient visit of the study took place during December 2005, with the final visit of the extension in February 2010. Of the 282 patients who were randomized at the start of the study, 112 of 140 patients (80.0%) in the everolimus group and 133 of 142 patients (93.7%) in the control group completed the first 12 months of the trial. Of these 245 patients, 108 of 112 everolimus patients (96.4%) and 127 of 133 control patients (95.5%) entered the 12-month extension phase (intent-to-treat and safety populations). The reason for noninclusion of the other 10 patients was not recorded. In total, 14 patients discontinued the study during months 12 to 24 (everolimus 10 and controls 4). This included eight patients in the everolimus arm who discontinued because of adverse events compared with no control patients (P=0.002; Fig. 1).
The characteristics of the two treatment groups were similar, other than the time posttransplant at the point of study entry, which was shorter in the everolimus treatment group. This difference was observed in the heart transplant subpopulation (60±48 months vs. 81±58 months in controls, P=0.02) but not in the lung transplant subpopulation (50±31 months vs. 57±42 months, P=0.26; Table 1). Blood pressure and heart transplant function were similar between groups at month 0, but among the lung transplant recipients, forced expiratory volume in 1 sec was significantly higher in the everolimus-treated cohort versus controls (P=0.038; Table 1).
Immunosuppression and Concomitant Medication
Table 2 summarizes immunosuppression for all patients who completed the 24-month study visit (n=222). After randomization, mean everolimus exposure decreased progressively during the 24-month follow-up period, from 7.0±3.2 ng/mL at month 0 to 4.5±1.4 ng/mL at month 24, remaining within the target range of 3 to 8 ng/mL throughout. In the everolimus cohort, mean cyclosporine A (CsA) trough level decreased to below the target, maximum of 75 ng/mL by week 6, remaining stable during the 24-month study. From month 0 to 24, there was a 56.0% reduction in mean CsA trough level (P<0.001) in the everolimus group. The mean tacrolimus trough level decreased from 10.0±3.2 ng/mL at month 0 in the everolimus group to 5.0±1.4 ng/mL at month 24 (a decrease of 50.0% from month 0, P<0.001). In the control arm, mean CsA concentration decreased by 19.7% from baseline to month 24 (P<0.001), whereas mean tacrolimus concentration remained virtually unaltered. Use of azathioprine or mycophenolic acid (MPA) also varied numerically, but not significantly, between groups (P=0.14 and P=0.23, respectively; Table 1). In the everolimus arm, the median dose of mycophenolic acid (expressed as MMF equivalents) was reduced from 2000±733 mg to 1500±715 mg/day and 1375±700 mg/day at months 12 and 24, respectively, reflecting the protocol recommendation of a 25–50% MMF dose reduction in everolimus-treated patients. In the control arm, the median dose of mycophenolic acid was unchanged from baseline. Concomitant drug therapy during the 24 months after randomization in the everolimus and control groups, respectively, was as follows: β blockers, 31.5% and 44.1% (P=0.059); calcium channel blockers, 50.9% and 55.9% (P=0.51); angiotensin-converting enzyme inhibitors, 23.1% and 23.6% (P=1.00); and statins, 75.9% and 78.0% (P=0.76).
Analysis of mGFR was performed for all patients in whom mGFR values were available at month 0, 12, and 24, that is, 222 of 235 patients who entered the extension study (94.5%; everolimus 103 and controls 119). At month 0, mean mGFR was 49.3±14.7 mL/min in the everolimus group and 49.1±13.0 mL/min in the controls (P=0.50). Mean mGFR at month 0 was higher in the heart transplant recipients compared with the lung transplant recipients (51.7±14.4 mL/min vs. 44.9±14.5 mL/min), but it was similar between treatment groups within each category (Table 1). At month 24, mean mGFR was 52.5±16.4 mL/min in the everolimus group versus 46.8±15.2 mL/min in the control group, representing a mean increase of 3.2±12.3 mL/min from month 0 in the everolimus-treated patients and a mean decrease of 2.4±9.0 mL/min in the controls (P<0.001, analysis of covariance [ANCOVA]). The between-group difference in the change of mGFR from month 0 to 24 was significant in both the heart and lung transplant subpopulations, with a mean difference of 5.5 mL/min in favor of everolimus in the heart transplant patients (P=0.003, ANCOVA) and 6.0 mL/min in the lung transplant patients (P=0.02, ANCOVA; Table 3; Fig. 2a).
The change in mGFR was analyzed post hoc according to patients' time posttransplant at the point of randomization using covariance analysis, based on whether they were transplanted within or above the median time and according to tertiles of time after transplantation (Table 3; Fig. 2b). Among the total study population, patients with a shorter time posttransplant (tertile groups 1 and 2) experienced the greatest improvement in mGFR after conversion to everolimus. Similar results were observed in the heart and lung transplant subpopulations (data not shown). This difference was still apparent by month 24 but the interaction between treatment and time from transplant was not significant, partly because tertile groups 1 and 2 showed a similar improvement to one another and partly because group 3 had a somewhat better improvement at month 24 compared with month 12 (Table 3). The improvement in mGFR after conversion to everolimus was also significantly higher in those patients with mGFR lower than median at month 0 (Fig. 2c).
The change in estimated GFR (modification of diet in renal disease) from month 0 to 24 also showed a benefit for everolimus (everolimus 5.0±14.3 mL/min and controls 0.1±10.0 mL/min; P=0.005, ANCOVA), which was not significant for the heart transplant subpopulation (5.0±14.8 mL/min vs. 0.9±10.1 mL/min, P=0.08) but was significant within the lung transplant subpopulation (5.0±13.4 mL/min vs. −1.5±9.7 mL/min, P=0.02).
In the 24-month population, biopsy-proven acute rejection (BPAR) occurred in six everolimus patients (5.6%; five 1A/2 and one 3A) and in five control patients (3.9%; four 1A and one 3A) during months 12 to 24 (P=0.76). No patient died as a result of BPAR. One patient in the everolimus group died from chronic rejection shortly before month 18; autopsy revealed the presence of bronchiolitis obliterans syndrome, chronic rejection, and unspecified inflammation. One control patient died because of complications of a left lower leg amputation. No other deaths or graft losses occurred during this period.
Safety and Tolerability
Safety data are reported for months 12 to 24 after randomization; data during the first year have been published previously (12). In the second year of the study, one or more adverse event was reported in 78.7% (85/108) of everolimus patients and 79.5% (101/127) of control patients (P=0.87), with a total of 288 adverse events reported in the everolimus group and 276 adverse events in the control group. The most frequently reported adverse event was nasopharyngitis (everolimus 14.8% and controls 15.0%) followed by edema (everolimus 8.3% and controls 8.7%). Pneumonia occurred in 8 everolimus patients (7.4%) and 11 control patients (8.7%). The rate of infections was similar in the everolimus group (46.3%, 50/108) and the control arm (46.5%, 59/127).
During months 12 to 24, 33.3% (36/108) of everolimus patients and 38.6% (49/127) of controls (P=0.40) experienced a total of 43 and 64 serious adverse events, representing a rate of 0.39 and 0.50 serious events per patient in the everolimus and control groups, respectively. The most frequent serious adverse event in both groups was pneumonia (everolimus 5/108 [4.6%] and controls 9/127 [7.1%], P=0.43). Adverse events led to study discontinuation in eight everolimus patients (pulmonary emboli [two patients], skin problems, hypercholesterolemia, stroke, diarrhea, edema, and muscular pain) and no control patients.
Table 4 summarizes changes in laboratory and hematology parameters from month 0 to 24. Levels of total cholesterol, low-density lipoprotein-cholesterol, and triglycerides increased significantly in the everolimus cohort versus controls, as observed previously at month 12 (12). There were also significant between-group differences in levels of alanine aminotransferase and bilirubin, which were not considered clinically relevant. There were no clinically relevant differences in serum electrolytes between groups. One patient in the everolimus group discontinued because of abnormal laboratory results (high levels of creatine kinase, aspartate aminotransferase, and alanine aminotransferase).
Left ventricular end-diastolic diameter and ejection fraction remained stable in both treatment groups in the heart transplant cohort, with a mean change in left ventricular end-diastolic diameter from month 0 of −0.1±0.8 cm and 0.0±0.4 cm (P=0.61) in the everolimus and control groups, respectively, and a mean change in ejection fraction from month 0 of −0.6%±8.5% and 0.1%±7.9% (P=1.0). Mean heart rate increased by 3±12 bpm in the everolimus group and decreased by 3±14 bpm in controls (P=0.007). In the lung transplant cohort, the mean change in forced vital capacity from month 0 to 24 was similar between groups (everolimus −0.2±0.3 L, controls −0.1±0.4 L, P=0.47), as was the change in forced expiratory volume in 1 sec (everolimus −0.2±0.2 L/sec, controls −0.10±0.2 L/sec, P=0.32).
The results of this randomized, multicenter study demonstrate that the renal benefit of converting maintenance thoracic transplant recipients to everolimus with low-exposure CNI is sustained to 2 years postconversion. Mean mGFR was approximately 5 mL/min higher in patients receiving everolimus with reduced-exposure CNI versus control patients who continued to receive standard-exposure CNI—a difference that was similar at 12 and 24 months, suggesting that the improvement in renal function may continue long term. A significant difference in mGFR was observed in both heart and lung transplant patients when analyzed separately. Indeed, the benefit of conversion to everolimus became more pronounced over time in the lung transplant group, such that statistical significance was reached by month 24.
This study confirms the findings from previous registry data demonstrating a progressive decline in renal function after heart (13) and lung (14) transplantation, with 10% to 20% of patients experiencing severe renal insufficiency at 5 years posttransplant. This decline can, however, be reversed by shifting the immunosuppression, introducing everolimus with concomitant minimization of CNI exposure. The effect seems to be time dependent, because patients with the shortest time posttransplant experienced the greatest renal benefit to month 12. This benefit lost statistical significance by month 24 although a numerical superiority remained. A recent study of conversion from CNI-based to everolimus-based immunosuppression in heart transplant patients demonstrated that early conversion (average 5.5 months posttransplant) was associated with a greater potential to improve renal function compared with late conversion (average 96 months posttransplant) (15). In kidney transplantation, the CONVERT study randomized patients at 6 to 120 months posttransplant to continue CNI or switch to sirolimus and found no significant benefit in terms of GFR after CNI discontinuation (16), whereas the CONCEPT trial reported improved renal function when conversion was performed at 3 months after kidney transplantation (17). In another randomized study, de novo kidney transplant recipients were randomized to everolimus with low CNI or to higher exposure everolimus and low CNI, but no difference in renal function was observed after 6 months' follow-up (18). Data from kidney transplantation, in which chronic allograft dysfunction is always important, may, however, not be directly applicable to thoracic transplantation.
In our population, exposure to CNI was reduced by 56% for CsA and by 50% for tacrolimus after conversion to everolimus, but the overall rate of BPAR was similar in everolimus-treated patients and in controls. The number of BPAR episodes more than or equal to 3A in the heart transplant subpopulation was also similar between groups, and there was only one rejection graded A2 in everolimus-treated lung transplant recipients. Although immunosuppressive efficacy requires careful monitoring in future studies, it does not seem that this substantial reduction in CNI exposure incurred any marked penalty in terms of immunosuppressive efficacy in the presence of everolimus therapy. Other authors who have reported CNI reduction after introduction of mTOR inhibitor therapy in heart transplantation have reported a similar experience (7–11).
As would be expected in a population of transplant recipients, virtually all patients experienced at least one adverse event during 12 to 24 months after randomization. The higher rate of serious adverse events observed at 12 months (0.58 per patient in the everolimus group vs. 0.42 per patient in the control arm) was no longer present at month 24. Pneumonia reported as a serious adverse event, which had been reported more frequently in everolimus-treated patients versus controls at month 12, occurred at a similar rate in both groups during months 12 to 24. Despite the similar rate of serious adverse events, more patients discontinued study medication because of adverse events in the everolimus arm. In this open-label trial, it is possible that bias may have influenced decisions to discontinue, but this can only be speculation. Hematology parameters did not suggest that bone marrow toxicity was a safety concern with everolimus.
In conclusion, these findings indicate that conversion from a standard CNI regimen to everolimus with reduced CNI in thoracic transplant patients with mild to moderate renal dysfunction achieves a significant benefit in terms of renal function that is maintained for 2 years. Although renal function declined slightly in both arms during the 24-month study period, the between-group difference was sustained, suggesting that the advantage of conversion to an everolimus-based regimen may be preserved long term. The dramatic reduction in CNI exposure was not accompanied by any marked loss of efficacy. The results from this trial suggest that conversion of treatment should take place early after transplantation. Future trials may clarify the optimal timing of conversion to everolimus and identify the patient types and dosing regimens that can minimize the need for discontinuation because of adverse events.
MATERIALS AND METHODS
Nordic Certican Trial in Heart and Lung Transplantation was an open-label, multicenter, randomized, parallel-group, controlled study. The study methodology has been described in detail previously (12). In brief, maintenance heart and lung transplant patients were recruited at specialist transplant centers in Denmark, Norway, and Sweden. Patients were included if they were older than 18 years, had undergone heart or lung transplantation more than or equal to 1 year previously, and their current immunosuppression regimen contained CsA or tacrolimus. A further requirement was that patients had a measured or calculated GFR more than or equal to 20 mL/min/1.73 m2 and less than 90 mL/min/1.73 m2 if GFR was ≥60 mL/min/1.73 m2 and <90 mL/min/1.73 m2, at least one posttransplant GFR value more than 10% above GFR at the point of randomization was required. Key exclusion criteria were as follows: multiorgan transplantation, acute rejection within less than or equal to 3 months before study entry, current or previous treatment with an mTOR inhibitor, low platelet count (<50,000/mm3), low white blood cell count (≤2500/mm3), hemoglobin less than 8 g/dL, severe hypercholesterolemia (≥8.0 mmol/L), or hypertriglyceridemia (≥6.0 mmol/L) despite conventional optimal treatment, planned coronary revascularization, or a major cardiac event within less than or equal to 3 months.
Randomization was performed centrally by a computer-based automated system. The study was open label. In the intervention group, everolimus was initiated on the morning of day 1 at a dose of 0.75 to 1.5 mg two times per day, adjusted from week 1 onward to target an everolimus trough concentration in the range 3 to 8 ng/mL. On the same day, the dose of CsA or tacrolimus was reduced by more than or equal to 20% with further reductions after everolimus trough concentration was in the range 3 to 8 ng/mL to achieve a 30% to 70% reduction in CNI trough level versus preconversion level and aiming for a CsA trough level less than 75 ng/mL or a tacrolimus trough level less than 4 ng/mL. If patients in the intervention group were receiving CsA and MPA, a 25% to 50% reduction in MPA dose was recommended 1 week after introduction of everolimus with further MPA dose reductions as necessary to maintain the preconversion MPA exposure after CsA dose reduction (19, 20). In the control arm, all immunosuppression remained unchanged unless an alteration was medically necessary.
After the 12-month study visit, patients were invited to enter the following 12-month follow-up phase. At the 24-month visit, GFR was measured using Cr-EDTA clearance or an equivalent method. Estimated GFR was calculated using the modification of diet in renal disease formula (21).
The primary efficacy variable was the change in mGFR from the point of randomization (month 0) to month 12, as reported previously (12). The main secondary endpoint specified in the protocol was to compare renal function between treatment groups, as assessed by mGFR, based on the change from month 0 to 24 of treatment. Between-group comparisons of the change in mGFR used the ANCOVA model with treatment, transplant, time from transplant as factors and treatment*transplant, treatment*time from transplant as interaction factors, and month 0 value and age as covariates. Comparisons of treatment groups at month 0 used analysis of variance with treatment and center as factors. Categorical variables were compared using Fisher's exact test. All analyses were two sided at a significance level of 0.05. The sample size calculation for the 12-month study has been described elsewhere (12). All patients provided written informed consent. The study received institutional review board approval and was conducted in accordance with the International Conference on Harmonisation Harmonized Tripartite Guidelines for Good Clinical Practice, applicable local regulations, and the Declaration of Helsinki.
The authors thank the leading contribution made to this study by Claes-Håkan Bergh, who (sadly) has since died. They also thank the Nordic Certican Trial in Heart and Lung Transplantation investigators, coinvestigators and study nurses: Copenhagen, Charlotte Just Poulsen; Ida Steffensen (study investigator); Göteborg, Bengt Rundqvist (study investigator), Annie Janssen and Katarina Karlsson (study nurses); Linköping, Barbro Gustafsson, Anette Gylling, and Monika Karlsson (study nurses); Lund, Björn Kornhall, Öyvind Reitan, Lennart Hansson, and Ingrid Skog (study investigators); Liselotte Persson, Ulrika Nibble, and Elisabeth Svebring (study nurses); Oslo, Anne Relbo, Ingelin Grov, Anne Toril Klette, Hege Merethe Hagen, and Dag Bergli (all nursing team members). The authors thank the members of the Data Monitoring Committee: Prof. Karl Swedberg, Sahlgrenska University Hospital/Östra, Gothenburg, Sweden (Chairman, Cardiologist), Prof. Anders Hartmann, Oslo University Hospital, Oslo, Norway (Nephrologist), Asger Dirksen, Gentofte University Hospital, Copenhagen, Denmark (Pneumunologist), and Prof. Hans Wedel, Nordic School of Public Health, Gothenburg, Sweden (Statistician). Caroline Dunstall provided editorial support.
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