Tacrolimus Combined with Two Different Dosages of Sirolimus in Kidney Transplantation: Results of a Multicenter Study

Authors


Abstract

Tacrolimus combined with mycophenolate mofetil (MMF) is an effective regimen in kidney transplantation. This study compared the efficacy of combining tacrolimus and two different dosages of sirolimus with an established tacrolimus-MMF regimen. Each day in addition to tacrolimus, 325 patients received 2 mg sirolimus (TAC-SRL2 mg), 325 patients received 0.5 mg sirolimus (TAC-SRL0.5 mg) and 327 patients 1 g MMF (TAC-MMF). The initial tacrolimus dose was 0.2 mg/kg/day. Sirolimus patients received loading doses of 6 or 1.5 mg, and daily doses of 2 or 0.5 mg thereafter. Steroid administration was identical for all groups. The incidence of biopsy-proven acute rejection was lower in the TAC-SRL2 mg group (15.7%) compared with the TAC-SRL0.5 mg (25.2%, p = 0.003) and the TAC-MMF groups (22.3%, p = 0.036). Six-month graft survival was 91.0% (TAC-SRL2 mg), 92.6% (TAC-SRL0.5 mg) and 92.4% (TAC-MMF); the respective values for patient survival were 98.1%, 97.8% and 97.9%. Thirty-four patients (10.5%), 19 patients (5.8%) and 16 patients (4.9%) in the TAC-SRL2 mg, TAC-SRL0.5 mg and TAC-MMF groups, respectively, discontinued the study because of adverse events. Hyperlipemia was reported more often in the TAC-SRL2 mg group (24.0%) compared with 19.4% (TAC-SRL0.5 mg) and 11.0% (TAC-MMF; p < 0.05). Combining 2 mg sirolimus/day with tacrolimus results in lower rates of acute rejection, but a higher incidence of adverse events.

Introduction

The combination of tacrolimus and mycophenolate mofetil (MMF) has proved to be a highly efficacious treatment for patients undergoing kidney transplantation, and is now the most commonly prescribed immunosuppressive regimen in Europe and the United States (1). The combination is well-tolerated by the patient, has reduced acute rejection to low levels and resulted in substantial improvement in short- and long-term graft survival outcomes (2).

Sirolimus (rapamycin, RAPA) was recently introduced as an adjunctive immunosuppressant for solid organ transplantation. Sirolimus binds to the same immunophilin (FKBP-12) as tacrolimus, but unlike tacrolimus, the sirolimus/FKBP complex does not attach to calcineurin, but rather to a different protein called mammalian target of rapamycin (mTOR) (3). The FKBP/RAPA/mTOR complex prevents the progression of the cell cycle from G1 to S in T cells by inhibiting cytokine-induced signal transduction pathways (4). Therefore, due to the complementary mechanism of action, sirolimus and tacrolimus act synergistically to create effective immunosuppression.

The tacrolimus-sirolimus combination was first tested in 32 recipients of liver, kidney or pancreas transplants, and resulted in a low rate of rejection and excellent graft function (5). In a small study of 11 kidney transplant patients treated with tacrolimus and low-dose sirolimus, the patients had good renal function after 1 year with no acute rejection episodes (6). Several larger studies published recently have reported that the combination of tacrolimus with sirolimus can achieve acute rejection rates of less than 10% (7–9). The overall safety profile of the tacrolimus-sirolimus regimen appears to be good, the main side effect of sirolimus appearing to be a dose-dependent increase in serum lipid levels (7,10,11).

The combination of tacrolimus with 2 mg sirolimus seems very effective in preventing acute rejection in kidney transplant patients, and clinical efficacy appears to start with sirolimus doses as low as 0.5 mg (7). To determine the optimal dose of sirolimus in combination with tacrolimus, we investigated the efficacy and safety of two regimens that combined tacrolimus with either 0.5 or 2 mg sirolimus, and compared these with a tacrolimus and MMF regimen that has proven efficacy in preventing acute rejection in kidney transplant patients. Here, we present the data from the largest multicenter study to compare these three different immunosuppressive regimens.

Patients and Methods

Study design

This was a 6-month, randomized, open-label, parallel-group, comparative, phase III study conducted in 72 centers in 15 European countries, and 3 centers in Australia. The study was performed in accordance with the ethical principles described in the Declaration of Helsinki, and the Ethics Committee of each center reviewed the protocol and granted approval before the start of the study. Assessments were made on days 1 and 8, at week 2 and month 1 and monthly thereafter until month 6.

Patients

Following written informed consent from the patient, male and female patients aged 18 years or older who had end-stage kidney disease and were suitable candidates for primary renal transplantation or retransplantation (unless the previous graft was lost due to rejection within the preceding 12 months) were enrolled in the study. Patients with high immunological risk (defined as having a panel reactive antibody grade >85% in the previous 6 months and/or having a previous graft survival of less than 1 year due to immunological reasons) were excluded from the study. In addition, patients with significant liver disease, defined as having during the past 28 days, continuously elevated ASAT (SGOT) and/or ALAT (SGPT) levels three times greater than the upper value of the normal range of the investigational site were not allowed to enter the study. Further exclusion criteria included malignancy; uncontrolled infections; severe diarrhea; vomiting; upper gastrointestinal malabsorption or active peptic ulcer; intolerance to any of the study drugs, or the requirement of additional immunosuppressive drugs or antibodies; grafts from non-heart-beating donors; a cold ischemia time of the donor kidney of more than 40 h; patients who received a graft from a hepatitis C, hepatitis B or HIV positive donor; patients with severe hypercholesterolemia (<350 mg/dL, 9.1 mmol/dL); patients who had previously received an organ transplant other than kidney; women who were pregnant or breast-feeding and patients who were likely to become noncompliant.

Randomization

Randomization was 1:1:1 and was performed locally at each center using sealed randomization envelopes supplied by the study sponsor. Patients were assigned to one of three treatment groups: tacrolimus, corticosteroids and 0.5 mg sirolimus (TAC-SRL0.5 mg) or tacrolimus, corticosteroids and 2 mg sirolimus (TAC-SRL2 mg) or tacrolimus, corticosteroids and 1 g MMF (TAC-MMF).

Standard immunosuppression

The initial daily dose of tacrolimus was 0.2 mg/kg given as two oral doses (0.1 mg/kg pre-operatively within 12 h prior to graft reperfusion, and if possible, within 3 h of anesthesia). Subsequent oral tacrolimus doses were adjusted to maintain whole blood trough concentrations of 8–16 ng/mL between days 0 and 14, and 5–15 ng/mL between days 15 and 183. Tacrolimus blood concentrations were measured locally.

The administration of corticosteroids was identical for all three treatment groups: 500 mg or less of methylprednisolone or an equivalent on day 0 and 125 mg on day 1. Subsequent daily doses of prednisone or equivalent were tapered from 20 mg (up to day 14), 15 mg (up to day 28), 10 mg (up to day 42) and 5 mg thereafter until study end.

The daily dose of 1 g MMF (500 mg twice daily) was given as soon as the patient was able to tolerate oral administration.

In both sirolimus treatment groups, the liquid formulation of sirolimus was used throughout the study. Sirolimus loading doses were three times the maintenance dose (i.e. 1.5 or 6.0 mg) and were given with the first post-operative dose of tacrolimus. Thereafter daily maintenance doses were 0.5 or 2.0 mg sirolimus administered once daily along with the morning dose of tacrolimus. A central laboratory assayed whole blood trough concentrations of sirolimus using high pressure liquid chromatography with tandem mass spectrometry detection.

None of the patients received antibody induction therapy.

Anti-rejection treatment

During the study, acute rejection episodes were treated according to local practice with pulse corticosteroids, OKT3 or polyclonal antibodies. Any other systemic immunosuppressive medications were prohibited.

Infection prophylaxis

Prophylactic treatment for Pneumocystis carinii pneumonia was mandatory throughout the study. In cases where a CMV positive donor graft was transplanted into a CMV negative recipient, oral ganciclovir was administered prophylactically for up to 3 months.

Assessments

The primary efficacy endpoint of the study was the overall estimated rate of patients with biopsy-proven acute rejection within the first 6 months of transplantation. Secondary endpoints included the incidence of and time to first biopsy-proven acute rejection episode within the first 6 months of transplantation, the incidence of and time to first biopsy-proven corticosteroid-resistant acute rejection, patient and graft survival and renal function as assessed by creatinine clearance estimated by the Cockcroft-Gault formula. A rejection episode was considered as biopsy-proven if one biopsy result between the start and stop date of the rejection episode was classified as rejection according to the Banff criteria (12,13).

Safety assessments included the monitoring of adverse events and vital signs as well as clinical laboratory evaluations (hematology and clinical chemistry, including measurements of hepatic and renal function). An adverse event was defined as any untoward occurrence in a patient during the study regardless of whether or not it was related to the study treatment.

Statistical analyses

A 10% difference between treatment groups in the rate of patients with biopsy-proven acute rejection was considered a clinically meaningful margin of noninferiority. Therefore it was planned to randomize 285 patients per treatment group to give the study a power of 80% to conclude noninferiority if there was no difference between the treatment groups. The intent-to-treat population was used for all of the statistical analyses, i.e. all randomized patients who received at least one dose of the study medication. Kaplan-Meier methods including 95% confidence intervals estimated the rate of patients free of biopsy-proven acute rejection. The incidence of acute rejection, and the various categories of acute rejection were evaluated using Fisher's exact test (two-sided) for three pair-wise comparisons. Fisher's exact test was also used to compare the incidence of adverse events (coded by a modified COSTART dictionary) among treatment groups. Patient and graft survival probabilities were estimated using Kaplan-Meier methods; pair-wise comparisons were made between treatments using the Wilcoxon-Gehan test.

Results

Patient demographics and baseline characteristics

In total, 977 patients made up the intent-to-treat population: 325 patients in both the TAC-SRL0.5 mg and TAC-SRL2 mg treatment groups, and 327 patients in the TAC-MMF group. The treatment groups were comparable with respect to demographic and baseline characteristics (Table 1). The number of grafts from living donors was similar among treatment groups: 9.2%, 11.1% and 8.3% for the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively.

Table 1. Demographic and baseline characteristics
 Tacrolimus + Corticosteroids
0.5 mg Sirolimus2 mg Sirolimus1 g MMF
  1. Intent-to-treat population.

  2. 1Not recorded for all patients.

N325325327
Age in years (mean ± SD)44.6 ± 12.947.3 ± 12.446.0 ± 11.7
Min-Max18–7318–7319–72
Male/Female (%)64.6:35.460.3:39.766.7:33.3
Ethnic group—No. of patients (%)
 Caucasian316 (97.2)317 (97.5)319 (97.6)
 Black4 (1.2)2 (0.6)3 (0.9)
 Oriental3 (0.9)2 (0.6)3 (0.9)
 Other3 (0.6)4 (1.2)2 (0.6)
Viral status at baseline
 CMV positive1217 (69.1)224 (70.9)218 (68.6)
 HBV positive115 (4.6)10 (3.1)14 (4.3)
 HCV positive19 (2.8)13 (4.0)16 (5.0)
CMV positive donor/negative recipients (%)17.815.715.9
Previous transplants
 0296 (91.1)302 (92.9)295 (90.2)
 126 (8.0)20 (6.2)29 (8.9)
 22 (0.6)3 (0.9)3 (0.9)
 31 (0.3)0 (0.0)0 (0.0)
Age of donor in years (Mean ± SD)44.8 ± 13.143.7 ± 14.544.6 ± 13.8
Min-Max5–705–797–70
Mean Total HLA mismatch2.82.92.9
Mean cold ischemia time (hours)17.4 ± 8.616.3 ± 8.017.1 ± 8.1
Pre-existing diabetes mellitus—No. of patients (%)29 (8.9)35 (10.8)32 (9.8)
Pre-study statin administration—No. of patients (%)46 (14.2)72 (22.2)57 (17.4)

Patient disposition

More patients in the TAC-SRL2 mg treatment group discontinued the study (70 patients, 21.5%) compared with the TAC-SRL0.5 mg (49 patients, 15.1%) and TAC-MMF (48 patients, 14.7%). Adverse events were the main reason for study discontinuation in all three groups: 34 patients (10.5%), 19 patients (5.8%) and 16 patients (4.9%) in the TAC-SRL2mg, TAC-SRL0.5 mg and TAC-MMF groups, respectively. The next most frequent reason for study discontinuation was graft failure which occurred in 16 patients (4.9%), in the TAC-SRL2 mg group and in 11 patients (3.4%) in both the TAC-SRL0.5 mg and TAC-MMF treatment groups.

Immunosuppression

Median daily tacrolimus doses and whole blood trough levels were similar among all three treatment groups throughout the study. During week 1, the median daily oral tacrolimus dose/kg body weight was 0.166, 0.162 and 0.158 mg in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively. By months 4–6, the respective median daily tacrolimus dose had decreased to 0.099, 0.090 and 0.081 mg. Median tacrolimus whole blood trough levels during week 1 were 13.73, 13.74 and 14.86 ng/mL in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively. By months 4–6, the respective median whole blood trough levels were 10.09, 9.50 and 10.33 ng/mL.

Median sirolimus whole blood trough levels increased between week 1 and month 3, and stabilized thereafter (Figure 1). Median trough levels in the TAC-SRL0.5 mg group were 0.95 ng/mL during week 1, 1.46 ng/mL at month 3 and 1.43 ng/mL between months 4 and 6. In the TAC-SRL2 mg group, median sirolimus trough levels were 2.71 ng/mL during week 1, 4.57 ng/mL at month 3 and 4.75 ng/mL between months 4 and 6.

Figure 1.

Median sirolimus whole blood trough levels. Median trough levels in the TAC-SRL0.5 mg group were 0.95 ng/mL during week 1, 1.46 ng/mL at month 3 and 1.43 ng/mL between months 4 and 6. In the TAC-SRL2 mg group, median trough levels were 2.71 ng/mL during week 1, 4.57 ng/mL at month 3 and 4.75 ng/mL between months 4 and 6.

Efficacy

The Kaplan-Meier estimated rate of patients free from biopsy-proven acute rejection within the first 6 months of transplantation was 73.9% in the TAC-SRL0.5 mg group, 83.7% in the TAC-SRL2 mg group and 76.6% in the TAC-MMF group (Figure 2). The estimated difference between the TAC-SRL2 mg and TAC-MMF regimen was 7.1% (98.3% CI: −0.004, 0.147), thereby demonstrating statistical noninferiority of the TAC-SRL2 mg regimen compared with the TAC-MMF regimen. In addition, the results of the unadjusted Wilcoxon-Gehan test showed that there was a significant difference in the estimated rate of patients with biopsy-proven acute rejection between the TAC-SRL2 mg and TAC-SRL0.5 mg regimens (p = 0.003), as well between the TAC-SRL2 mg and TAC-MMF regimens (p = 0.026). There was no difference between the TAC-MMF and TAC-SRL0.5 mg regimens.

Figure 2.

Time to biopsy-proven acute rejection. There was a significant difference in the estimated rate of patients with biopsy-proven acute rejection between the TAC-SRL2 mg and TAC-SRL0.5 mg regimens (unadjusted Wilcoxon-Gehan test; p = 0.003), as well as for TAC-SRL2 mg and TAC-MMF (p = 0.026). There was no difference between the TAC-MMF and TAC-SRL0.5 mg regimens.

The incidence of biopsy-proven acute rejection during the study period and the classification of acute rejection episode are summarized in Table 2. Although significantly fewer patients in the TAC-SRL2 mg treatment group experienced biopsy-proven acute rejection compared with the TAC-SRL0.5 mg group (p = 0.003, Fisher's exact test) and the TAC-MMF group (p = 0.036, Fisher's exact test), the incidence of corticosteroid-resistant acute rejection was similar for all three treatment groups: 8.0% (TAC-SRL0.5mg), 7.1% (TAC-SRL2mg) and 6.7% (TAC-MMF).

Table 2. Biopsy-proven acute rejection—number of patients (%)
 Tacrolimus + corticosteroids
0.5 mg Sirolimus (N = 325)2 mg Sirolimus (N = 325)1 g MMF (N = 327)
  1. Intent-to-treat population.

Acute rejection82 (25.2)51 (15.7)73 (22.3)
 Spontaneously resolving1 (0.3)0 (0.0)1 (0.3)
 Corticosteroid-resistant26 (8.0)23 (7.1)22 (6.7)
 Resolved with further treatment20 (6.2)18 (5.5)18 (5.5)

All rejection episodes were of grade I and II, except for five patients (1.5%) in the TAC-SRL0.5 mg group, three patients (0.9%) in the TAC-SRL2 mg group and two patients (0.6%) in the TAC-MMF group who had grade III rejection. Graft survival rates at month 6 were comparable among the three treatment groups: 92.6% (TAC-SRL0.5mg), 91.0% (TAC-SRL2mg) and 92.4% (TAC-MMF). There was no difference among the treatment groups in patient survival during the 6-month study period. By month 6, the Kaplan-Meier overall patient survival rate was 97.8%, 98.1% and 97.9% for the TAC-SRL0.5 mg, TAC-SRL2 mg and TAC-MMF treatment groups, respectively. The main cause of death in all three treatment groups was infection: three patients died because of sepsis in the TAC-SRL0.5 mg group; in the TAC-SRL2 mg group, one patient died because of aspergillosis, one because of EBV-infection and one due to sepsis; and in the TAC-MMF group, one patient died because of aspergillus pneumonia and one patient because of sepsis.

Renal function, measured by serum creatinine, progressed satisfactorily and was good at month 6 with little difference among treatment groups. Median serum creatinine levels decreased in a similar way for most patients during the study, and by month 6, median levels were 130.0 μmol/L (TAC-SRL0.5mg), 132.6 μmol/L (TAC-SRL2mg) and 131.0 μmol/L (TAC-MMF). The median values for creatinine clearance estimated by the Cockcroft-Gault formula at month 6 were 51.7 mL/min (TAC-SRL0.5mg), 49.5 mL/min (TAC-SRL2mg) and 52.5 mL/min (TAC-MMF).

Safety

A total of 295 patients (90.8%) administered the TAC-SRL0.5 mg regimen reported adverse events compared with 308 patients (94.8%) in the TAC-SRL2 mg group, and 300 patients (91.7%) in the TAC-MMF treatment group. Hyperlipemia (p < 0.001, Fisher's exact test), hypertension (p = 0.030, Fisher's exact test), lymphoceles (p = 0.022, Fisher's exact test) and glucose metabolism disorders (p = 0.039, Fisher's exact test) occurred significantly more often in the patients receiving the TAC-SRL2 mg regimen compared with the patients administered TAC-MMF (Table 3). Leucopenia (p = 0.023, Fisher's exact test) and diarrhea (p = 0.010, Fisher's exact test) were observed significantly more often in the MMF-treated patients.

Table 3. Incidence of adverse events—number of patients (%)
 Tacrolimus + corticosteroidsp-Value1
0.5 mg Sirolimus (N = 325)2 mg Sirolimus (N = 325)1 g MMF (N = 327)
  1. Intent-to-treat population.

  2. 1Fisher's exact test.

  3. 2New-onset or worsening.

Hyperlipemia63 (19.4)78 (24.0)36 (11.0)<0.001
Diarrhea37 (11.4)34 (10.5)59 (18.0)0.010
Hypertension248 (14.8)50 (15.4)30 (9.2)0.030
Lymphoceles14 (4.3)28 (8.6)13 (4.0)0.022
Leucopenia15 (4.6)18 (5.5)32 (9.8)0.023
Glucose metabolism disorders54 (16.6)80 (24.6)64 (19.6)0.039
 New-onset diabetes mellitus20/296 (6.8)44/290 (15.2)28/295 (9.5)0.005
  Requiring insulin8/296 (2.7)15/290 (5.2)16/295 (5.4)>0.05

At baseline, 8.9%, 10.8% and 9.8% of patients in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups had glucose metabolism disorders (coded using the modified COSTART dictionary as glucose tolerance decreased, hyperglycemia or diabetes mellitus). Among the patients without pre-existing glucose metabolism disorders, significantly more patients in the TAC-SRL2 mg group developed diabetes mellitus (p = 0.005, Fisher's exact test). The number of patients requiring insulin for new-onset diabetes mellitus was similar in the TAC-SRL2 mg and TAC-MMF treatment groups (Table 3). Oral anti-diabetic medication was necessary for 10 patients (3.4%), 20 patients (6.9%) and 11 patients (3.7%), in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively. HbA1c was measured during the study and at baseline, the median value of HbA1c was 5.2%, 5.2% and 5.3%, in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups respectively; at month 6, the respective values were 5.6%, 5.5% and 5.8%.

The incidence of spontaneous reports of hypercholesterolemia was significantly higher in the TAC-SRL2 mg group (43 patients, 13.2%) compared with 19 patients (5.8%) and 18 patients (5.5%) in the TAC-SRL0.5 mg and TAC-MMF groups, respectively (p < 0.001, Fisher's exact test). Compared with the TAC-MMF treatment group, the patients treated with sirolimus had a larger rise in median total serum cholesterol levels between baseline and month 3, with the patients in the TAC-SRL2 mg group having the greatest increase (Figure 3). Patients receiving 2 mg sirolimus also experienced the largest increase in median levels of triglycerides during the study compared with the other two treatment groups (p < 0.001, Wilcoxon test). At baseline, median triglyceride levels were 1.80 mmol/L in the TAC-SRL2 mg group, 1.74 mmol/L in the TAC-SRL0.5 mg group and 1.80 mmol/L in the TAC-MMF group. By month 6, the respective values were 2.20 mmol/L, 1.77 mmol/L and 1.71 mmol/L. There was no significant difference among treatment groups in LDL-Ch levels between baseline and month 6 (p = 0.282, Kruskal-Wallis test). At baseline, the median LDL-Ch levels were 2.66, 2.92 and 2.70 mmol/L for the patients in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively. The corresponding values at month 6 were 2.96, 3.14 and 2.92 mmol/L.

Figure 3.

Median total serum cholesterol*.

Statins were administered at some time during the study to 132 patients (40.6%) in the TAC-SRL2 mg group, 97 patients (29.8%) in the TAC-SRL0.5 mg group and 80 patients (24.5%) in the TAC-MMF group (p < 0.001, Fisher's exact test). For comparison, 72 patients (22.2%), 46 patients (14.2%) and 57 patients (17.4%) in the TAC-SRL2mg, TAC-SRL0.5 mg and TAC-MMF treatment groups received statins before the study.

The incidence of abnormal wound healing was similar among treatment groups. Eight patients (2.4%) in both the TAC-SRL2 mg and TAC-MMF groups had abnormal wound healing compared with seven patients (2.2%) in the TAC-SRL0.5 mg group. Proteinuria was reported as an adverse event in 16 patients (4.9%) in the TAC-SRL0.5 mg group, 21 patients (6.5%) in the TAC-SRL2 mg group and 14 patients (4.3%) in the TAC-MMF group (p = 0.452, Fisher's exact test). According to laboratory values, 4.6%, 6.5% and 3.7% of patients in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups had proteinuria >1 g/L while 1.2%, 1.5% and 0.9% of patients, respectively, had values >3 g/L.

Infections were recorded for 124 patients (38.2%) in the TAC-SRL0.5 mg group, 149 patients (45.8%) in the TAC-SRL2 mg group and 160 patients (48.9%) in the TAC-MMF treatment groups (p = 0.017, Fisher's exact test). Bacterial infections occurred more often in the TAC-SRL2 mg and TAC-MMF groups (p = 0.128, Fisher's exact test); there was no difference among groups in the incidence of fungal infections. Cytomegalovirus infection was reported for 16 patients (4.9%), 13 patients (4.0%) and 26 patients (8.0%) in the TAC-SRL0.5mg, TAC-SRL2 mg and TAC-MMF groups, respectively (p = 0.084, Fisher's exact test). No malignancies were observed for the patients in the TAC-SRL0.5 mg and the TAC-MMF treatment groups. In the TAC-SRL2 mg group, two patients developed post-transplant lymphoproliferative disorder (a 46-year-old man and a 49-year-old woman with B-cell lymphoma). In both patients, immunosuppressive treatment was interrupted and the patients recovered.

Discussion

This is the largest multicenter study to investigate the efficacy and safety of two different tacrolimus-sirolimus combinations compared with an established tacrolimus-MMF regimen in kidney transplant patients. Sirolimus was added to a standard regimen of tacrolimus plus corticosteroids, and the tacrolimus doses and whole blood trough levels were within the normal range for kidney transplant patients. Sirolimus median whole blood trough levels were between 0.95 and 4.75 ng/mL depending upon dosage and time, and were comparable to those reported in other studies using similar doses of sirolimus. (7,14)

These study data showed that the incidence of biopsy-proven acute rejection observed with the 0.5 mg sirolimus-tacrolimus combination was comparable to that of the tacrolimus-MMF regimen. However, adding 2 mg sirolimus to the tacrolimus-based regimen resulted in a significantly lower incidence of biopsy-proven acute rejection compared with the regimens combining tacrolimus with 1 g MMF or 0.5 mg sirolimus. The acute rejection rate with the TAC-SRL2 mg regimen seen in this study (15.7%) is lower than reported for the combination of cyclosporin with 2 mg sirolimus (15,16), and compares well with the acute rejection rate (13%) described recently in a U.S. study that compared a regimen of tacrolimus and corticosteroids combined with 2 mg sirolimus or 2 g MMF (17). The U.S. group reported an acute rejection rate for the TAC-MMF treatment group of 11% which is lower than that seen in our study. This difference in acute rejection rate is most likely due to the fact that 20% of the patients (those with delayed graft function) in the U.S. study received antibody induction. Also in accordance with U.S. standards, the physicians administered a higher dose of MMF (2 g/day) than is usual in Europe and this also probably contributed to the lower rate of acute rejection.

We noted no difference in the incidence of corticosteroid-resistant, biopsy-proven acute rejection among the three treatment groups in our study.

Patients receiving 2 mg sirolimus experienced the greatest number of adverse events, and more of these patients discontinued the study prematurely because of adverse events. Both tacrolimus-sirolimus combinations caused a significant increase in hyperlipemia and hypertension, and 40% of the patients treated with 2 mg sirolimus required statins to control elevated total serum cholesterol levels. Hyperlipemia was most likely caused by sirolimus (7,8,10) because tacrolimus has been shown not to affect lipid metabolism (18) and may even reduce cholesterol levels (19). If serum cholesterol levels cannot be controlled by statins, then reducing or withdrawing sirolimus from a tacrolimus-based regimen after 3 months could be an option as it appears that sirolimus can be withdrawn at this time without compromising immunosuppressive efficacy (7).

The incidence of new-onset or worsening of hypertension was higher in both groups of sirolimus-treated patients compared with patients receiving tacrolimus and MMF. Lymphoceles, another common side effect of sirolimus treatment, also occurred more often in the patients administered sirolimus. It is known that sirolimus can cause lymphatic leakage for weeks after renal transplantation, and perinephric fluid collections and lymphoceles may require surgical treatment (20,21).

The incidence of CMV infection was lower in the sirolimus-treated patients compared with the patients receiving MMF, and it seems that sirolimus does not increase the likelihood of infection. The patients treated with sirolimus also had a lower incidence of leucopenia and diarrhea compared with the MMF-treated patients.

In all three treatment groups, renal function was good for the majority of patients completing the study. It should be considered, however, that in accordance with the requirements of Good Clinical Practice, only the renal function data for the patients who remained in the study are available. As a larger number of patients in the high-dose sirolimus treatment group were withdrawn because of adverse events, we can assume that the incidence of impaired renal function could have been underreported in the patients receiving 2 mg sirolimus.

In conclusion, tacrolimus appears to be equally effective when combined with 0.5 mg sirolimus or 1 g MMF. Adding 2 mg sirolimus to a tacrolimus-based regimen enhances immunosuppressive activity and results in a lower incidence of biopsy-proven acute rejection. However, the improvement in acute rejection rate is attained at a cost of a higher incidence of adverse events, in particular, hyperlipemia, hypertension and lymphoceles. As cardiovascular disease is the leading cause of late mortality for kidney transplant patients, and hyperlipemia and hypertension are proven risk factors, the value of adding sirolimus long-term to a tacrolimus-based regimen needs to be carefully considered.

Acknowledgments

We thank Claire Foster for preparing the manuscript and Stefan Schleibner for his expert medical input. The study was supported by Fujisawa GmbH, Munich, Germany.

Appendix

Additional members of the TERRA Study Group: F. Mühlbacher (Allgemeines Krankenhaus Wien, Vienna, Austria); G. Russ (Queen Elisabeth Hospital, Woudville South, Australia); J. Eris (Royal Prince Alfred Hospital, Camperdown, Australia); R. Walker (Royal Melbourne Hospital, Parkville, Australia); J. Squifflet (Clinique University St. Luc, Brussels, Belgium); P. Clavien (Universitätsspital Zürich, Zurich, Switzerland); C. Redaelli (Inselspital Bern, Bern, Switzerland); F. Pietruck (Universitätsklinikum, Essen, Germany); P. Neuhaus (Campus Virchow Klinikum, Berlin, Germany); H. Neumayer (Universitätsklinik Charité, Berlin, Germany); M. Wiesel (Universitätsklinikum, Heidelberg, Germany); B. Nonnast-Daniel (Friedrich-Alexander Universität, Erlangen, Germany); B. Krämer (Klinikum der Universität, Regensburg, Germany); I. Hauser (Klinikum der Wolfgang-Goethe-Universität, Frankfurt, Germany); P. Fornara (Martin Luther Universität Halle-Wittenberg, Halle-Salle, Germany); V. Kliem (Nephrologisches Zentrum Niedersachsen, Münden, Germany); H. Seiter (Universität, Rostock, Germany); R. Viebahn (Chirurgische Universitätsklinik, Bochum, Germany); K.A. Jörgensen (University Hospital, Aarhus, Denmark); J.M. Morales Cerdan (Hospital 12 de Octubre, Madrid, Spain); M. Gonzalez-Molina (Hospital Regional Carlos Haya, Malaga, Spain); J. Ortuno Mirete (Hospital Ramon y Cajal, Madrid, Spain); D.R. Sola (Fundacio Puigvert, Barcelona, Spain); D.F.A. Valdes (Hospital Juan Canalejo, La Coruna, Spain); D.M. Arias (Hospital Marques de Valdecilla, Santander, Spain); D. Del Castillo (Hospital Reine Sofia, Cordoba, Spain); L. Capdevila (Hospital Vall d'Hebron, Barcelona, Spain); F. Anaya (Hospital Gregorio Marañon, Madrid, Spain); P. Pereira (Hospital Virgen del Rocio, Seville, Spain); F. Escuin (Hospital La Paz, Madrid, Spain); R. Lauzurica (Hospital Germans Trias y Pujol, Badalona, Spain); L. Pallardo Mateu (Hospital Universitario Dr. Peset, Valencia, Spain); A. Franco (Hospital General de Alicante, Alicante, Spain); G. Mourad (Hôpital Lapeyronie, Montpellier, France); B. Charpentier (Hôpital Bicetre, Le Kremelin Bicetre, France); P. Le Pogamp (CHRU Pontchaillou, Rennes, France); P. Viatel (Hôpital Michallon-CHU Nord, Grenoble, France); P. Merville (Hôpital Pellegrin-Tripode, Bordeaux, France); F. Berthoux (Hôpital Nord, St. Etiene, France); P. Lang (Hôpital Henri Mondor, Paris, France); C. Legendre (Hôpital St. Louis, Paris, France); F. Mignon (Hôpital Bichat, Paris, France); D. Cantarovich (Hotel Dieu, Clinique Nephrologie, Nantes, France); H. Kashi (Walsgrave General Hospital, Walsgrave, UK); P. Szenohradszky (SZOTE Sebeszeti Klinika, Szeged, Hungary); E. Ancona (Ospedale Giustinianeo, Padova, Italy); S. Stefoni (Ospedale Policlinico S. Orsola, Bologna, Italy); G. Calconi (Azienda Ospedaliera S Maria dei Battuti, Treviso, Italy); V. Cambi (Azienda Ospedaliera di Parma, Parma, Italy); G. La Greca (Azienda Ospedaliera di Vicenza, Vicenza, Italy); R. Maiorca (Ospedale Civile, Brescia, Italy); M. Carmellini (Azienda Ospedaliera Policlinico Le Scotte di Siena, Siena, Italy); G. Segoloni (Azienda Ospedaliera S Giovanni Battista, Torino, Italy); M. Castagneto (Policlinico Universitario Agostino Gemelli, Rome, Italy); F.P. Schena (Universita degli studi di Bari, Bari, Italy); J. Van der Heide (Akademisch Ziekenhuis Groningen, Groningen, the Netherlands); M. Lao (Transplantation Institute, Warsaw, Poland); F. Kokot (Silesian University Medical School, Katowice, Poland); G. Tyden (Huddinge University Hospital, Stockholm, Sweden); K. Claesson (University Hospital, Uppsala, Sweden).

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