Prevention of rejection
Only two RCT have compared MMF with AZA (4,5), with one update (6) (Table 1). The first (4) evaluated MMF/AZA in a cyclosporine-based quadruple regimen using antilymphocyte preparations for induction: 28 patients were randomized to MMF (1 g b.d.) and 29 to AZA (1–2 mg/kg daily); median follow-up was short, only 10 ± 3.2 months. The patient and graft survival was not different: MMF 89.3% and 89.7% versus AZA 85.7% and 82.7%, respectively. Liver biopsy was only performed if a rejection episode was clinically suspected. Histologically proven acute rejection was lower with MMF than with AZA: 21.4% (n = 6, 1 steroid resistant) versus 44.8% (n = 13, 2 steroid resistant) (p = 0.06). Thrombocytopenia was more frequent with AZA: 48.3% versus 21.4% (p < 0.05), as was leukopenia 20% versus 7.1% (p = ns). Gastritis and/or diarrhea occurred in six patients (four MMF and two AZA).
Table 1. Randomized controlled trials comparing azathioprine (AZA) and mycophenolate mofetil (MMF) after liver transplantation with respect to survival, rejection and adverse effects
|Author (ref) year||Immunosuppression Regimen (dose)||No. of patients||Median follow-up (Months)||Survival||Acute rejection1 (%)||Adverse effects|
|Patient (%)||Graft (%)||Infections (%)||GI symptoms (%)||Thrombocytopenia (%)||Leucopenia (%)|
|Sterneck et al. (4) 2000||CsA + steroids + MMF (1 g b.d.)|| 28||10 ± 3.2||89.3||89.7||21.4||32 ||14.2||21.4**|| 7.1|
|CsA + steroids + AZA (1–2 mg/kg/day)|| 29|| ||85.7||82.7||44.8||34 || 6.8||48.3 ||20 |
|Fischer et al. (6)3 2000||CsA + steroids + MMF (1 g b.d.)|| 31||10 ± 3.2||90.3||87.5||19.4||32 ||12.9||19.4**|| 6.5|
|CsA + steroids + AZA (1–2 mg/kg/day)|| 32|| ||83.9||81.3||40.6||31 || 6.2||46.9 ||18.8|
|Wiesner et al. (5) 2001||CsA + steroids + MMF (1.5 g b.d.)||278||At least 12||88 ||85.3|| 38.52*||45.5||51.3||6.9 || 3.6|
|CsA + steroids + AZA (1–2 mg/kg/day)||287|| ||87.1||85.4||47.7||43.2||49.8||12.5 || 0.7|
The update (6) had 31 MMF and 32 AZA patients. Median follow-up remained short: 10 ± 3.2 months; patient and graft survival were unchanged. Paradoxically, the rejection episodes remained numerically the same: MMF 19.4% (n = 6) versus AZA 40.6% (n = 13) (p = ns). The lack of statistical difference in rejection rates could be due to the small number of patients, but in any case the absence of any increase in rejection episodes in the updated report (6) makes interpretation of differences in rejection between AZA and MMF difficult.
The registration study for MMF in liver transplantation was an international multicenter randomized double-blind comparison of MMF versus AZA, each combined with cyclosporine and steroids (5): 278 patients assigned to MMF (1.5 g b.d.) and 287 to AZA (1–2 mg/kg/day). Liver biopsies were obtained only if rejection was suspected clinically. The principal endpoint was whichever occurred first posttransplantation: (1) biopsy-proven and treated acute rejection occurring within the first 6 months and (2) graft loss (death/retransplantation) occurring within the first year. Patients losing grafts within 6 months, without rejection, were counted for the rejection endpoint. The MMF group had a significant reduction in combined endpoint compared to AZA (38.5% vs. 47.7%; p = 0.025), but its two components were not separately described. However, the frequency of more than one acute rejection episode was similar: 7.7% AZA and 5.8% MMF. Moreover, 1-year patient and graft survival rates were not significantly different: MMF 88.8% and 85.3% versus AZA 87.1% and 85.4%, respectively. An absolute neutrophil count <500 occurred in 3.6% MMF but only 0.7% AZA patients (p = not reported) contrary to the increased leucopenia with AZA in the first study (4). Platelet count <25.000 occurred in 12.5% AZA and in 6.9% MMF patients (p = not reported). Opportunistic infections were similar: 45.5% (MMF) versus 43.2% (AZA).
The rejection rate with MMF (3 g/day) (5) was twice as high as in the open-label RCT (4) in which 2 g/day was used, despite similar use of cyclosporine and steroids and indications for biopsy for suspected rejection. Currently, most units use only 2 g/day MMF, so the comparison with AZA in the registration study does not mirror today's clinical practice. Only Sterneck et al. (4) compared 2 g/day MMF with AZA, with a nonsignificant reduction in rejection rates with MMF and no differences in graft or patient survival. Thus, in LT the evidence for a significant benefit in terms of cellular rejection of MMF over AZA is very poor.
Improving CNI-related nephrotoxicity
In patients with CNI-related nephrotoxicity after LT, the complete replacement of CNIs with MMF, although associated with improvement in serum creatinine in 77–100% of patients and improvement of creatinine clearance of about 9–11 mL/min, resulted in more acute cellular rejection. Rejection was frequent when CNI withdrawal occurred within 6 months at 50% (7), or 60% within 12 months (8). If CNI discontinuation (9) or reduction (9–11) occurred after 12 months, including other citated papers (11), acute rejection rates ranged from 0% to 30%.
Two reports document AZA as the primary immunosuppressive agent associated with CNI withdrawal (12,13). In one report (12), 12 patients with cyclosporine A (CsA)-related renal dysfunction at least 12 months after transplant received AZA (2 mg/kg/day) combined with CsA withdrawal. Improvement in renal function was minimal (mean follow-up: 18 months), and six patients (50%) had biopsy-proven acute rejection (two steroid resistant) and two died.
In the second study (13), the results were substantially different. Here, 26 patients received AZA associated with discontinuation or reduction of CsA (median time after LT: 10 months, range 18–57). When CsA was discontinued (n = 14), the mean serum creatinine decreased from 2.42 ± 0.48 to 1.72 ± 0.39 mg/dL (p = 0.00004) with no rejection; when CsA was reduced (n = 12), the mean serum creatinine decreased less markedly (2.08 ± 0.34 to 1.85 ± 0.41 mg/dL; p = 0.69) with one rejection episode.
In LT, no RCT has compared MMF and AZA in patients with CNI-related nephrotoxicity. There is only one retrospective comparative analysis (14) reporting 33 patients with CNI-related nephrotoxicity converted to MMF 1 g b.d. (n = 23) or to AZA 2 mg/kg/day (n = 10) after a mean of 63 ± 51 months. An improvement in creatinine clearance of more than 10% occurred in 16 patients (49%), all receiving MMF (significant univariately, but multivariate analysis was not performed). Six episodes of acute rejection occurred (three MMF and three AZA; p = ns). Side effects were more frequent with MMF: 10 versus 0 (p < 0.05).
Two studies report outcomes after replacing AZA by MMF in patients with renal dysfunction with reduction (15) or discontinuation of CNIs (8). The first (15) evaluated 32 patients, who had MMF (1 g b.d.) added and AZA discontinued at a mean interval of 25.6 ± 34.7 (range 1.2–127.8) months after LT. Mean follow-up after starting MMF was 4.8 ± 0.6 (range 3.1–6) years, with only two biopsy-proven acute rejection episodes. Discontinuation of MMF was necessary in three patients (9.4%), only one due to rejection. At the end of the study, 13 patients (41%) had normal creatinine values. The second study (8) was an RCT: 18 patients with creatinine >150 μmol/L were randomized to MMF (500 mg b.d., increased to 1 g b.d. at 2 weeks) and CNI dose reduction, and then discontinuation at 3 months (study group, n = 9) or to continue to receive AZA and CNIs without dose reduction (control group, n = 9); unfortunately, the failure to reduce CNI negates a useful comparison with MMF. Serum creatinine concentrations fell in six of eight patients treated for more than 1 month following CNI reduction. However, two of five patients receiving MMF who completed 3 months follow-up, developed severe ductopenic rejection requiring retransplantation, and another patient had steroid-responsive severe rejection. Therefore, the study was stopped. It is unclear whether the dosage of MMF was insufficient (2 g/day) and/or whether CNI discontinuation was the major factor.
LT for HCV-related cirrhosis
AZA and MMF both inhibit IMPDH and have some common features with ribavirin, which enhances the activity of interferon in the treatment of HCV. However, whether MMF or AZA are beneficial in HCV-infected liver transplant recipients and whether MMF is more effective compared to AZA is not clear.
Firpi et al. (16) evaluated MMF and HCV viral load randomizing 30 nontransplanted patients with chronic HCV hepatitis to four regimens (1000 mg b.d., 500 mg b.d., 250 mg b.d. or a matched oral placebo b.d.) for 8 weeks. No subject who was HCV–RNA positive on entry had a one-log decrease in virus concentration or became virus negative and no subject normalized serum alanine aminotransferase (ALT) level. There were no significant differences within or between groups. A prospective 9-month cross-over study evaluated MMF (1 g/b.d.), used as substitute for AZA, in 13 transplanted patients with recurrent chronic HCV (17), with a background of CNI and steroids. In all patients at the end of the MMF treatment period, the mean viral load had significantly increased compared to baseline (1.64 × 106± 1.34 × 106 vs. 0.74 × 106± 0.47 × 106 mRNA copies/mL; p = 0.02). When AZA was reintroduced the mean viral load declined and at the end of the study, the mean values were not statistically different to baseline AZA values. However, the increase in viral load compared to baseline (58.2 ± 37.5 vs. 80 ± 69 U/L) was not associated with ALT flares.
Nine studies between 1996 and 2008 evaluated AZA and HCV recurrence (18–26). AZA was associated with reduced severity of HCV recurrence in five studies (56%) (18,19,22,23,25), evaluated in a univariate analysis in one, multivariate in three, and with chi-square test in one, whereas in four studies (44%) (20,21,24,26) there was similar severity. However, no study with AZA showed increased severity of recurrent HCV. In contrast in 17 studies evaluating MMF and HCV recurrence between 2001 and 2007 (5,19,23,24,26–38), only two studies (12%) (31,33) found decreased severity of HCV recurrence, and in one (31) there was no multivariate analysis. Nine studies (53%) (5,19,24,26–30,32) documented similar severity of HCV recurrence, but six (35%) (23,34–38) showed increased severity of HCV recurrence (Tables 2 and 3).
Table 2. Studies with AZA (5/9) and MMF (2/17) documenting reduced severity of HCV recurrence
|Author||No. of patients total/HCV||Outcome||Variables||Results||p-Value|
| Hunt et al. (22) 2001||65/65||HCV recurrence||Use vs. nonuse of AZA1||6/17 vs. 37/48||<0.005 |
| ||Progression of HCV recurrence|| ||1/6 vs. 18/37||0.014|
| Berenguer et al. (19) 2002||522/283||Cirrhosis (fibrosis stage 4)||Induction without AZA2||Associated in the univariate analysis||–|
| Berenguer et al. (23) 2003||554/554||Severe HCV recurrence (Fibrosis 3 and 4 within the first 2 years)||AZA use <12 months3||OR 3.24; 95%CI 1.51–6.96||0.003|
| Samonakis et al. (18) 2005||193/193||Overall survival||AZA at 3 months3||OR 0.3; 95%CI 0.18–0.64||–|
| ||3 months survival||No maintenance AZA3||OR 0.3; 95%CI 16–0.64||–|
| ||Severe fibrosis||No maintenance AZA2||–||0.029|
| Eid et al. (25) 2007||92/92||Cirrhosis (Fibrosis stage 4)||Use of AZA3||OR 0.37; 95%CI 0.14–0.92||0.033|
| Bahra et al. (31) 2005||80/80||Fibrosis score (after 24 months of treatment)||MMF vs. no MMF||1 ± 0.4 vs. 2.05 ± 1.02||<0.013 |
| Sanchez-Bueno et al. (33) 2006||476/142||HCV recurrence||No maintenance MMF||OR 53||0.015|
Table 3. Studies with MMF (6 of 17) documenting increased severity of HCV recurrence
|Author||No. of patients Total/HCV||Outcome||Variable||Results||p-Value|
|Berenguer et al. (37) 2000||284/284||Fibrosis progression2||Induction with MMF||–||0.05 |
|Fasola et al. (38) 2002||125/125||Severe fibrosis1||No/low-dose MMF vs. high-dose MMF||Number of patients: 26 vs. 0||0.07 |
|Burak et al. (36) 2002||93/93||Graft failure3||Use of MMF vs. AZA||RR 2.75; 95%CI 1.14–6.61||0.024|
|Berenguer et al. (23) 2003||554/554||Severe HCV recurrence3 (Fibrosis 3 and 4 within the first 2 years)||Induction with MMF||OR 8.89; 95%CI 2.67–29.6||0.001|
|Kornberg et al. (34) 2005||21/21||Stage of fibrosis (6 months vs. pre-MMF)1||Use of MMF||Stage increasing (1.5 ± 0.5 vs. 2.3 ± 0.5)||0.04 |
|Kornberg et al. (35) 2007||19/19||Stage of fibrosis (12 months vs. pre-MMF)1||Use of MMF||Stage increasing (1.5 ± 0.5 vs. 2.3 ± 0.7)||0.02 |
A single direct comparison between MMF and AZA was evaluated in 56 HCV-positive liver transplanted patients—an RCT subgroup (5): 27 received CsA, steroids and MMF (1 g b.d. i.v. for 4 to 10 days, then oral 1.5 g b.d.) and 27 received CsA, steroids and AZA (1–2 mg/kg/day i.v. then by oral administration). The combined incidence at 6 months after transplantation of acute cellular rejection and/or graft loss was significantly reduced with MMF compared to AZA (30.6% vs. 41.4%; p < 0.04). A multivariate analysis showed that MMF was superior in preventing rejection within 6 months. Graft loss rates were 16.1% (AZA) and 9.4% (MMF). Histological HCV recurrence, associated with HCV–RNA in serum, was 18.5% MMF and 29.1% AZA (p = not reported) at 6 months. However, despite 1-year data being available for the main study (5), the 1-year and other long-term data for the HCV subgroup were not available. In particular, HCV recurrence rate and its severity were not reported.
Recently, Kornberg et al. (34) performed a prospective study, with contrasting early and delayed results: 21 patients received quadruple induction CsA-based immunosuppression, augmented by MMF (n = 12) or by AZA (n = 9). Recurrent HCV disease was diagnosed earlier with MMF, than with AZA (50 ± 35 vs. 35 ± 35 weeks), but patients taking MMF had less severe allograft fibrosis at diagnosis of disease recurrence (Ishak–Knodell) (1.5 ± 0.5 vs. 2.2 ± 1.2). However, stage of fibrosis significantly increased with MMF, during 6 months of antiviral treatment compared to AZA (1.5 ± 0.5 vs. 2.3 ± 0.5; p = 0.04). As details of the adequacy of liver biopsy samples were not given, and this is important for staging, these paradoxical results of earlier recurrence with less severe disease are difficult to interpret (39).
The data on MMF and AZA with respect to HCV recurrence need to be better known, given that 41% of 36 US transplant centers responding to a questionnaire about patients transplanted for HCV-related cirrhosis.(40), used MMF, and that azathioprine use was not mentioned at all.