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Immunosuppressive treatment and progression of histologic lesions in kidney allografts

2005; Elsevier BV; Volume: 68; Linguagem: Inglês

10.1111/j.1523-1755.2005.09923.x

1523-1755

Jose J. Morales,

Neurological Complications and Syndromes

Immunosuppressive treatment and progression of histologic lesions in kidney allografts Renal transplantation is the best therapeutic option for patients with end-stage renal disease. Although short-term results are excellent, long-term graft survival has not improved substantially in recent times. Chronic allograft nephropathy (CAN) and death with a functioning graft are the most important causes of graft loss. Recent evidence shows that nephrotoxicity of calcineurin inhibitors contributes to CAN, and the introduction of non-nephrotoxic drugs such as mycophenolate mofetil (MMF) and mammalian target of rapamycin inhibitors may provide new immunosuppressive strategies to improve long-term results after renal transplantation. MMF decreases the risk of developing chronic allograft failure and is useful for treating established CAN, because it has a beneficial effect on allograft fibrosis. Treatment with sirolimus (SRL), a basic immunosuppressive drug given in association with MMF, may offer better renal function, decrease the prevalence of CAN, and downregulate expression of genes responsible for the progression of CAN than treatment with cyclosporine A (CsA). SRL also permits an early elimination of CsA from SRL-CsA-steroid regimens and shows better renal function and improved renal histology without risk of rejection. Notably, this approach improves graft survival at 4 years. Further multicenter studies are needed to determine whether both approaches produce similar results by comparing immunosuppression caused by SRL-based and tacrolimus (TAC)-based treatments. Because TAC is the most commonly used anticalcineurin drug, it is important to compare the effects of steroid-TAC-SRL treatment with and without elimination of TAC. Finally, although caution is needed, the use of non-nephrotoxic immunosuppressive treatment may change the natural history of CAN. Immunosuppressive treatment and progression of histologic lesions in kidney allografts Renal transplantation is the best therapeutic option for patients with end-stage renal disease. Although short-term results are excellent, long-term graft survival has not improved substantially in recent times. Chronic allograft nephropathy (CAN) and death with a functioning graft are the most important causes of graft loss. Recent evidence shows that nephrotoxicity of calcineurin inhibitors contributes to CAN, and the introduction of non-nephrotoxic drugs such as mycophenolate mofetil (MMF) and mammalian target of rapamycin inhibitors may provide new immunosuppressive strategies to improve long-term results after renal transplantation. MMF decreases the risk of developing chronic allograft failure and is useful for treating established CAN, because it has a beneficial effect on allograft fibrosis. Treatment with sirolimus (SRL), a basic immunosuppressive drug given in association with MMF, may offer better renal function, decrease the prevalence of CAN, and downregulate expression of genes responsible for the progression of CAN than treatment with cyclosporine A (CsA). SRL also permits an early elimination of CsA from SRL-CsA-steroid regimens and shows better renal function and improved renal histology without risk of rejection. Notably, this approach improves graft survival at 4 years. Further multicenter studies are needed to determine whether both approaches produce similar results by comparing immunosuppression caused by SRL-based and tacrolimus (TAC)-based treatments. Because TAC is the most commonly used anticalcineurin drug, it is important to compare the effects of steroid-TAC-SRL treatment with and without elimination of TAC. Finally, although caution is needed, the use of non-nephrotoxic immunosuppressive treatment may change the natural history of CAN. Renal transplantation is the therapy of choice for patients with end-stage renal disease1Wolfe R.A. Ashby V.B. Milford E.L. et al.Comparison of mortality in all patients on dialysis, patients on dialysis awaiting transplantation, and recipients of a first cadaveric transplant.N Engl J Med. 1999; 341: 1725-1730Google Scholar. The short-term outcome of renal transplantation has improved dramatically in the past 20 years. Introduction of cyclosporine (CsA) and newer, more efficient immunosuppressive drugs such as tacrolimus (TAC), mycophenolate mofetil (MMF), and rapamycin (sirolimus [SRL]) has reduced the prevalence of acute rejection and increased the rate of graft survival from 90% to 95% at 1 year in most units2Halloran P.F. Immunosuppressive drugs for kidney transplantation.N Engl J Med. 2004; 351: 2715-2729Google Scholar. However, long-term graft survival has not improved substantially3Meier-Kriesche H.-U. Schold J.D. Kaplan B. Long-term renal allograft survival: Have made significant progress or is it time to rethink our analytic and therapeutic strategies?.Am J Transplant. 2004; 4: 1289-1295Google Scholar. The most important causes of late allograft failure are chronic allograft nephropathy (CAN), death of the functioning graft, and de novo or recurrent disease4Seron D. Arias M. Campistol J.M. Morales J.M. For The Spanish Chronic Allograft Nephropathy Study Group Transplantation. 2003; 76: 1588-1594Google Scholar. Chronic CsA-TAC nephrotoxicity can contribute to CAN, which is the second most common cause of graft loss (after death with a functioning graft)5Pascual M. Theruvath T. Kawai T. et al.Strategies to improve long-term outcomes after renal transplantation.N Engl J Med. 2002; 346: 580-590Google Scholar. CAN is characterized by progressive renal dysfunction accompanied by interstitial fibrosis, tubular atrophy, vascular occlusive changes, and glomerulosclerosis6Monaco A.P. Burke JR., J.F. Ferguson R.M. et al.Current thinking on chronic renal allograft rejection: Issues, concerns, and recommendations from a 1997 roundtable discussion.Am J Kidney Dis. 1999; 33: 150-160Google Scholar. Despite the use of potent immunosuppressive combinations, biopsies show that the rate of CAN may be as high as 94% in the first year7Nankiwell B.J. Borrows R.J. Fung C.L.S. et al.The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 394: 2326-2333Google Scholar. The long-term presence of anticalcineurin nephrotoxicity is almost universal7Nankiwell B.J. Borrows R.J. Fung C.L.S. et al.The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 394: 2326-2333Google Scholar. The introduction of MMF and target of rapamycin (TOR) inhibitors, a new class of antirejection dugs, may provide new immunosuppressive strategies to prevent, decrease, or slow the progression of graft failure. In this review, we discuss the most important recent data about the effects of non-nephrotoxic immunosuppression in the treatment of chronic renal dysfunction and focus particularly on the progression of histological lesions in kidney allografts. Histopathologic results of 2-year protocol biopsies from 144 patients enrolled in the United States FK506 kidney study showed that acute rejection occurred in 9% of patients treated with TAC and 9.2% of patients treated with CsA. CAN was also similar with the two treatments (73.2% and 62%, respectively), showing that nephrotoxicity and acute rejection are the most significant predictors of CAN. The authors concluded that non-immunologic factors, such as CsA or TAC nephrotoxicity, may play an important role in CAN8Solez K. Vincenti F. Filo R.S. Histopathologic findings from 2-year protocols biopsies from a U.S. multicenter kidney transplant trial comparing tacrolimus versus cyclosporine: A report of the FK506 Kidney Transplant Study Group.Transplantation. 1988; 66: 1736-1740Google Scholar. Taking protocol biopsies regularly after transplantation, Nankiwell et al evaluated the natural history of CAN in a prospective study of 120 recipients of pancreas–kidney transplantation7Nankiwell B.J. Borrows R.J. Fung C.L.S. et al.The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 394: 2326-2333Google Scholar. They described two distinct phases of injury. The initial phase of early tubulointerstitial lesion arises because of ischemic injury, prior severe rejection, and a subclinical rejection showing that grade I CAN was present in 94.2% of patients. Notably, the combination TAC plus MMF eliminated subclinical rejection and reduced tubulointerstitial damage at 12 months9Nankiwell B.J. Borrows R.J. Fung Cl-S et al.Natural history, risk factors and impact of subclinical rejection in kidney transplantation.Transplantation. 2004; 78: 242-249Google Scholar. Compared with TAC, CsA increases chronic interstitial fibrosis, and MMF is more protective than azathioprine (Aza), independent of their nephrotoxic and immunologic properties10Nankiwell B.J. Borrows R.J. Fung C. S.-L. et al.Delta analysis of posttransplantation tubulointerstitial damage.Transplantation. 2004; 78: 434-441Google Scholar. The later phase of CAN occurs after 1 year and is characterized by microvascular and glomerular injury. The presence of CsA and TAC nephrotoxicity (e.g., arterial hyalinosis, ischemic glomerulosclerosis, and tubulointerstitial damage) implicated in the late permanent injury approaches 100% at 10 years. Severe CAN is present in 58.4% of patients at 10 years6Monaco A.P. Burke JR., J.F. Ferguson R.M. et al.Current thinking on chronic renal allograft rejection: Issues, concerns, and recommendations from a 1997 roundtable discussion.Am J Kidney Dis. 1999; 33: 150-160Google Scholar. This study clearly demonstrated the contribution of nephrotoxicity by anticalcineurin drugs in the development and progression of CAN. Recent studies have compared the effect of anticalcineurin drugs on the development of CAN. Moreso et al 11Moreso F. Seron D. Carrera M. et al.Baseline immunosuppression is associated with histological findings in early protocol biopsies.Transplantation. 2004; 78: 1064-1068Google Scholar performed a case-control study to compare histological lesions in protocol biopsies from patients treated with TAC + MMF with those treated with CsA + MMF. Protocol biopsies were performed 4 to 6 months after transplantation. Although subclinical acute rejection occurred less frequently in TAC patients (14.2% vs. 34.7%), the total chronic score and the prevalence of CAN did not differ between groups (38.8% in CsA and 34.6% in TAC). Jurewicz12Jurewicz W.A. Tacrolimus versus cyclosporin immunosuppression: Long-term outcome in renal transplantation.Nephrol Dial Transplant. 2003; 18: i7-ii11Google Scholar, Murphy et al 13Murphy G.J. Waller J.R. Sandorf R.S. et al.Randomized clinical trial of the effect of microemulsion cyclosporin and tacrolimus on renal allograft fibrosis.Br J Surg. 2003; 90: 680-686Google Scholar, and Baboolal et al 14Baboolal K. Jones G.A. Janezic A. et al.Molecular and structural consequences of early renal allograft injury.Kidney Int. 2002; 61: 686-696Google Scholar used randomized trials to compare treatment with CsA microemulsion and TAC, and reported that treatment with CsA was associated with an increased allograft fibrosis. Baboolal et al also suggest that the development of allograft fibrosis is mediated by an upregulation of profibrotic growth factors14Baboolal K. Jones G.A. Janezic A. et al.Molecular and structural consequences of early renal allograft injury.Kidney Int. 2002; 61: 686-696Google Scholar. A recent article described an extended follow-up of an open-label, randomized trial that examined conversion to Aza as early as 3 months after transplantation. One hundred twenty-eight patients were enrolled in a single center in 1983 and randomly assigned to continue CsA therapy (N = 68) or were converted to Aza (N = 60). At 15 years, graft survival tended to be lower in the CsA group (64% vs. 76.5%). The relative risk (RR) of CAN was significantly higher in patients receiving CsA (RR, 4.3; 95% confidence interval, 1.4–12.9), and the incidence of CAN was lower in patients with Aza (28% vs. 62%). These findings suggest a role of CsA nephrotoxicity in the development of CAN in a study started more than 20 years ago. The authors recommended the same immunosuppressive strategy using MMF instead of Aza15Bakker R.C. Hollander A.A. Mallat M.J. et al.Conversion from cyclosporine to azathioprine at three months reduces the incidence of chronic allograft nephropathy.Kidney Int. 2003; 64: 1027-1034Google Scholar. MMF, the morpholinoethyl ester of mycophenolic acid, inhibits purine metabolism by inhibiting the enzyme inosine monophosphate dehydrogenase. MMF inhibits the proliferation of T and B cells and the synthesis of antibodies by B cells16Platz D.P. Sollinger H.W. Hullet D.A. et al.RS-61443, a new, potent immunosuppressive agent.Transplantation. 1991; 51: 27-31Google Scholar. MMF administration in association with steroids, CsA, or TAC reduces acute rejection17European Mycophenolate Mofetil Cooperative Study Group Placebo-controlled study of mycophenolate mofetil combined with cyclosporin and corticosteroids for prevention of acute rejection.Lancet. 1995; 345: 1321-1325Google Scholar , 18Squifflet J.P. Backman L. Claesson K. et al.Dose optimization of mycophenolate mofetil when administered with a low dose of tacrolimus in cadaver renal transplant recipients.Transplantation. 2001; 72: 63-69Google Scholar. Notably, MMF is not nephrotoxic and does not have any hypertensive effect17European Mycophenolate Mofetil Cooperative Study Group Placebo-controlled study of mycophenolate mofetil combined with cyclosporin and corticosteroids for prevention of acute rejection.Lancet. 1995; 345: 1321-1325Google Scholar , 18Squifflet J.P. Backman L. Claesson K. et al.Dose optimization of mycophenolate mofetil when administered with a low dose of tacrolimus in cadaver renal transplant recipients.Transplantation. 2001; 72: 63-69Google Scholar. The Federal Drug Administration approved its use in renal transplantation in 1995. Currently, nearly 80% of patients receive MMF in various immunosuppressive combinations after renal transplantation in the United States19Shapiro R. Young J.B. Milford E.L. et al.Immunosuppression: Evolution in practice and trends, 1993–2003.Am J Transplant. 2004; 5: 874-886Google Scholar. Ojo et al analyzed 66,774 renal transplant recipients from the US renal transplant registry and showed that MMF decreased the RR of developing CAN by 27% (RR, 0.73)20Ojo A.O. Meier-Kriesche H.-U. Hanson J.A. et al.Mycophenolate mofetil reduces late renal allograft loss independent of acute rejection.Transplantation. 2000; 69: 2405-2409Google Scholar. Notably, this effect was independent of acute rejection, suggesting that, through its antiproliferative effects, MMF could be useful in protecting against vascular damage. In animal models of chronic allograft arteriolopathy, MMF decreases vascular intimal hyperplasia and the development of lesions similar to that seen in patients with CAN. Censored graft survival with MMF was significantly better than that with Aza at 4 years (85.6% vs. 81.9%). The most relevant conclusion of this important study is that MMF decreases the risk of developing chronic allograft failure. Reporting for the Tricontinental Mycophenolate Mofetil Renal Transplant Study Group, Mathew compared 3-year graft survival in two groups of renal transplant patients receiving MMF (1 g or 2 g) or Aza in association with CsA and steroids, and found significantly higher graft survival in the MMF group21Mathew T.H. A blinded, long-term, randomized multicentre studies of mycophenolate mofetil in cadaveric renal transplantation: Results at three years. Tricontinental Mycophenolate Mofetil Renal Transplantation Study Group.Transplantation. 1998; 65: 1450-1454Google Scholar. The Spanish Cooperative Study Group of Chronic Allograft Nephropathy prospectively explored the potential therapeutic role of MMF in patients diagnosed with CAN22Gonzalez Molina M. Seron D. Garcia Del Moral R. et al.Mycophenolate mofetil reduces deterioration of renal function in patients with chronic allograft nephropathy.Transplantation. 2004; 77: 215-220Google Scholar. One hundred-twenty patients with biopsy-proven CAN on double or triple therapy with CsA were treated with MMF. Before the introduction of MMF, patients showed progressive deterioration of renal function (glomerular filtration rate [GFR] 54.8 mL/min vs. 39.7 mL/min). After MMF started, renal function remained stable (GFR 39.7 mL/min vs. 41.3 mL/min) with a significant change in the slope of the GFR from -0.0144 to +0.00045. This positive reduction in the slope of the GFR was also seen in patients in whom CsA blood levels remained unchanged during follow-up. More recently, Dudley et al demonstrated that in patients with progressive deterioration renal function ("creeping creatinine") secondary to CAN, addition of MMF followed by withdrawal of CsA results in a significant improvement of renal function without the risk of acute rejection23Dudley C. Pohanka E. Riad H. et al.Mycophenolate mofetil substitution for cyclosporine in renal transplant recipients with chronic progressive allograft dysfunction: The "creeping creatinine" study.Transplantation. 2005; 79: 466-475Google Scholar. These and other center-based studies24Weir M.R. Ward M.T. Blahut S.A. et al.Long-term impact of discontinued or reduced calcineurin inhibitor in patients with chronic allograft nephropathy.Kidney Int. 2001; 59: 1567-1573Google Scholar have demonstrated that MMF is clinically useful for medium-term treatment of CAN. Little is known about whether MMF can also improve histological lesions associated with CAN. However, two MMF trials (American and tri-continental trials) analyzed sequential protocol biopsies from several centers. The chronic allograft damage index (CADI) was evaluated in biopsies taken at baseline, 12 months, and 36 months25Yilmaz S. Tomlanovich S. Mathew T. et al.Protocol core needle biopsy and histologic chronic allograft damage index (CADI) as surrogate end-point for long-term graft survival in multicenter studies.J Am Soc Nephrol. 2003; 14: 773-779Google Scholar. The CADI increased from 1.3 at baseline to 3.3 at 1 year and 4.1 at 3 years. Unfortunately, the effect of immunosuppression on the progression of histological lesions was not compared between treatment with MMF and Aza/placebo. In the study by Nankiwell that analyzed immunosuppression and interstitial fibrosis10Nankiwell B.J. Borrows R.J. Fung C. S.-L. et al.Delta analysis of posttransplantation tubulointerstitial damage.Transplantation. 2004; 78: 434-441Google Scholar, TAC and MMF were more potent than other conditions in reducing early chronic interstitial fibrosis. MMF was more protective than Aza in preventing a worsening of the chronic interstitial fibrosis score. The beneficial effect of MMF on allograft fibrosis might result from the reduction in tubular destruction by immunologic mechanisms or by a positive effect on fibrogenesis. SRL, a mammalian TOR inhibitor, suppresses graft rejection by interfering with cytoplasmic, biochemical cascades that transduce signals from the cell membrane to the nucleus. In animal models of organ transplantation, SRL exhibits potent anti-rejection activity and the ability to prolong allograft survival26Sehgal S.N. Rapamune (RAPA, rapamycin, sirolimus): Mechanism of action immunosuppressive effect results from blockade of signal transduction and inhibition of cell cycle progression.Clin Biochem. 1998; 31: 335-340Google Scholar , 27Morris R.E. Rapamycins: Antifungal, antitumor, antiproliferative, and immunosuppressive macrolides.Transplant Rev. 1992; 6: 39-87Google Scholar. Because SRL does not inhibit calcineurin, SRL should lack the nephrotoxic profile of calcineurin inhibitors. Preclinical studies have also indicated that SRL has no deleterious effects on renal function27Morris R.E. Rapamycins: Antifungal, antitumor, antiproliferative, and immunosuppressive macrolides.Transplant Rev. 1992; 6: 39-87Google Scholar , 28Shihab F.S. Bennett W.M. Yi H. et al.Combination therapy with sirolimus and mycophenolate mofetil: Effects on the kidney and on transforming grow factor-beta1.Transplantation. 2004; 77: 683-686Google Scholar, and that the combination of SRL and MMF is particularly promising, because it suppresses transforming growth factor-beta and had no effect on glomerular filtration. SRL also inhibits growth factor-stimulated smooth muscle cell proliferation and migration26Sehgal S.N. Rapamune (RAPA, rapamycin, sirolimus): Mechanism of action immunosuppressive effect results from blockade of signal transduction and inhibition of cell cycle progression.Clin Biochem. 1998; 31: 335-340Google Scholar and reduces neointimal hyperplasia by its inhibitory effect on arterial smooth muscle29Ikonen T.S. Gummert J.F. Hayase M. et al.Sirolimus (rapamycin) halts and reverses progression of allograft vascular disease in non-human primates.Transplantation. 2000; 70: 969-975Google Scholar. Additionally, despite elevating serum lipid concentrations, SRL inhibits atherosclerosis in experimental mouse models of atherogenesis30Castro C. Campistol J.M. Sancho D. et al.Rapamycin attenuates atherosclerosis induced by dietary cholesterol in apolipoprotein-deficient mice through a p27Kip1-independent pathway.Atherosclerosis. 2004; 172: 31-38Google Scholar. Clinical studies have confirmed the success of SRL as a prophylaxis for acute renal transplant rejection when used concomitantly with existing therapies. Early studies included a phase 2 trial31Kahan B.D. Julian B.A. Pescovitz M.D. et al.Sirolimus reduces the incidence of acute rejection episodes despite lower cyclosporine doses in Caucasian recipients of mismatched primary renal allografts: A phase II trial. Rapamune Study Group.Transplantation. 1999; 68: 1526-1532Google Scholar and two phase 3 trials that compared an SRL-CsA combination with Aza32Kahan B.D. Efficacy of sirolimus compared with azathioprine for reduction of acute renal allograft rejection: A randomised multicentre study. The Rapamune US Study Group [see comment].Lancet. 2000; 356: 194-202Google Scholar or placebo33Macdonald A.S. Group R.G.S. A worldwide, phase III, randomized, controlled, safety and efficacy study of a sirolimus/cyclosporine regimen for prevention of acute rejection in recipients of primary mismatched renal allografts.Transplantation. 2001; 71: 271-280Google Scholar and demonstrated reduced acute rejection rates. However, the phase 3 trials demonstrated that SRL exacerbated the nephrotoxic effects of CsA. Two early phase 2 studies directly compared the effects of SRL and CsA in Europe34Groth C.G. Backman L. Morales J.M. et al.Sirolimus (rapamycin)-based therapy in human renal transplantation: Similar efficacy and different toxicity compared with cyclosporine. Sirolimus European Transplant Study Group [see comment].Transplantation. 1999; 67: 1036-1042Google Scholar, 35Kreis H. Cisterne J.M. Land W. et al.Sirolimus in association with mycophenolate mofetil induction for the prevention of acute graft rejection in renal allograft recipients.Transplantation. 2000; 69: 1252-1260Google Scholar, 36Morales J.M. Wramner L. Kreis H. et al.Sirolimus does not exhibit nephrotoxicity compared to cyclosporine in renal transplant recipients.Am J Transplantation. 2002; 2: 436-442Google Scholar. Patients received either CsA or SRL in combination therapy with either corticosteroids and Aza or corticosteroids and MMF. SRL did not exhibit the nephrotoxic properties of CsA, and renal function was enhanced after CsA-free, SRL-based therapy. The 2-year data continued to show more favorable outcomes for risk factors such as hypertension and renal function in response to SRL therapy than with CsA therapy36Morales J.M. Wramner L. Kreis H. et al.Sirolimus does not exhibit nephrotoxicity compared to cyclosporine in renal transplant recipients.Am J Transplantation. 2002; 2: 436-442Google Scholar. Although the benefits of decreased hypertension and improved renal function were evident with SRL therapy, the poor lipid profiles were a side effect that had to be managed with increased use of lipid-lowering therapy. Flechner et al directly compared SRL and CsA and reported improved outcomes by adding an induction agent and reducing the doses of SRL to minimize side effects37Flechner S.M. Goldfarb D. Modlin C. et al.Kidney transplantation without calcineurin inhibitor drugs: A prospective, randomized trial of sirolimus versus cyclosporine.Transplantation. 2002; 74: 1070-1076Google Scholar. Their randomized phase 2 trial used basiliximab as an antilymphocyte-induction agent, and SRL or CsA in addition to MMF and steroids in primary renal allograft recipients. The results showed comparable outcomes for patient survival, graft survival, and biopsy-confirmed acute rejection and significantly better renal function in SRL-treated patients. Although higher than at baseline, fasting lipid concentrations were similar in both the SRL and CsA groups at all times studied in the 1-year period. Subsequent analysis at 2 years demonstrated that patients on SRL exhibited better renal function, lower prevalence of CAN (normal biopsies, 66% vs. 20.8%), and downregulated expression of genes linked to the pathways of tissue injury–remodeling and immune or inflammatory responses responsible for the progression of CAN38Flechner S.M. Kurian S.M. Solez K. et al.De novo kidney transplantation without use of calcineurin inhibitors preserves renal structure and function at two years.Am J Transplant. 2004; 4: 1776-1785Google Scholar. The authors concluded that this treatment may provide an alternative to the natural history of CAN with improved graft survival. Because SRL exacerbated CsA nephrotoxicity in phase 3 trials, a new phase 3 trial of early CsA withdrawal, the Rapamune Maintenance Regimen (RMR) study, was conducted39Johnson R.W. Kreis H. Oberbauer R. et al.Sirolimus allows early cyclosporine withdrawal in renal transplantation resulting in improved renal function and lower blood pressure [see comment].Transplantation. 2001; 72: 777-786Google Scholar. The regimen comprised the administration of SRL (2 mg), CsA, and steroids after transplantation, followed by randomization to CsA withdrawal 3 months with SRL through concentrations targeted at 20 ng/mL to 30 ng/mL (immunoassay) until month 12, and 15 ng/mL to 25 ng/mL thereafter. The results of this study confirmed that CsA withdrawal provides the benefits of improved renal function and lower blood pressure. At 12 months40Ruiz J.C. Campistol J.M. Grinyo J.M. et al.Early cyclosporine A withdrawal in kidney-transplant recipients receiving sirolimus prevents progression of chronic pathologic allograft lesions.Transplantation. 2004; 78: 1312-1318Google Scholar, both groups showed similar patient and graft survival rates. Acute rejection rates were 4.2% and 9.8% for SRL-CsA-steroid (ST) and SRL-ST, respectively (P = 0.035). Ruiz et al reported histological data at 1 year on 64 patients from Spain and Portugal enrolled in this trial, and showed that the percentage of patients in whom chronic lesions progressed was lower in the CsA elimination group than in the SRL group40Ruiz J.C. Campistol J.M. Grinyo J.M. et al.Early cyclosporine A withdrawal in kidney-transplant recipients receiving sirolimus prevents progression of chronic pathologic allograft lesions.Transplantation. 2004; 78: 1312-1318Google Scholar. Significant differences were observed in chronic interstitial fibrosis (70% vs. 41%) and tubular lesions (70% vs. 48%), but without differences in acute lesions indicative of subclinical rejection. The prevalence of CAN and the severity and incidence of new cases were lower in the SRL group. This observation at 1 year suggests that the benefits should continue in the long term41Stallone G. Dipaolo S. Schena A. et al.Early withdrawal of cyclosporine A improves 1-year kidney graft structure and function in sirolimus-treated patients.Transplantation. 2003; 75: 998-1003Google Scholar. A similarly designed study from Italy42Oberbauer R. Kreis H. Johnson R.W. et al.Long-term improvement in renal function with sirolimus after early cyclosporine withdrawal in renal transplant recipients: 2-year results of the Rapamune Maintenance Regimen Study.Transplantation. 2003; 76: 364-370Google Scholar evaluated the impact of early CsA withdrawal on kidney graft and structure at 1 year in patients receiving SRL-ST. Forty consecutive renal transplant patients were treated with steroids, CsA, and SRL (2 mg/day). After 3 months, patients were randomly assigned to receive the same therapy or to withdraw CsA and continue with SRL-ST. All patients underwent graft biopsy after reperfusion and 12 months after transplantation. Interestingly, CAN was diagnosed in 55% of all patients at 12 months, 64% in the group treated with SRL-CsA-ST, and 36% in patients treated with SRL-ST. CAN lesions were scored as moderate to severe in 90% of patients treated with SRL-CsA-ST compared with 32% in patients with SRL-ST. Notably, a vascular score ≥2 was present in 90% in the group treated with SRL-CsA-ST and in 38% of patients treated with SRL-ST. In addition, at 1 year, renal function was better in patients treated with SRL-ST. These results suggest that early elimination of CsA allows a significant reduction of chronic histological damage, particularly vascular injury. At 24 months in the RMR study42Oberbauer R. Kreis H. Johnson R.W. et al.Long-term improvement in renal function with sirolimus after early cyclosporine withdrawal in renal transplant recipients: 2-year results of the Rapamune Maintenance Regimen Study.Transplantation. 2003; 76: 364-370Google Scholar, the two groups did not differ significantly on patient survival, graft survival, acute rejection after randomization, and discontinuations. Serum creatinine concentration was significantly lower in the CsA withdrawal group than in the SRL group (167 μmol/L vs. 128 μmol/L, P < 0.001). The slope of 1/creatinine and systolic blood pressure was also significantly lower (141 mm Hg vs. 134 mm Hg, P < 0.001) in the CsA-withdrawal group. High-density lipoprotein cholesterol concentration was significantly higher in the SRL-ST group, whereas the concentrations of total cholesterol, low-density lipoprotein cholesterol, and triglyceride did not differ significantly between the two groups. Analysis of the RMR data at 36 months43Kreis H. Oberbauer R. Campistol J.M. et al.Long-term benefits with sirolimus-based therapy after early cyclosporine withdrawal.J Am Soc Nephrol. 2004; 15: 809-817Google Scholar showed a continuing beneficial trend in graft survival in the SRL-ST group. Acute rejection rates from randomization to month 36 did not differ significantly between the SRL-ST and SRL-CsA-ST groups, although serum creatinine concentration was significantly lower, and overall renal function improved or remained stable in the SRL-ST group. Blood lipid measures and cumulative use of statins were similar between the groups. Histological data at 3 years was available from 484 biopsies performed at engraftment at 12 and 36 months44Mota A. Arias M. Taskinen E.I. et al.Sirolimus-based therapy following early cyclosporine withdrawal provides significantly improved renal histology and function at 3 years.Am J Transplant. 2004; 4: 953-961Google Scholar. Two pathologists blindly evaluated all biopsies to obtain the CADI scores. At 36 months, among 63 patients with serial biopsies, the SRL-ST group had a significantly lower main CADI score (4.7 vs. 3.2, P = 0.003) and mean tubular atrophy score (0.77 vs. 0.32, P < 0.001). All six components of the CADI score (inflammation, tubular atrophy, intimal proliferation, glomerular sclerosis, mesangial matrix, and fibrosis) were numerically lower in the SRL-ST group. The inflammation and tubular atrophy scores decreased significantly between 12 and 36 months in the SRL-ST group (0.82 to 0.50, and 0.56 to 0.32, respectively) Table 1 . The calculated GFR was significantly higher in SRL-ST patients (68.2 mL/min vs. 54.8 mL/min). This study clearly demonstrated that withdrawing CsA from the SRL-CsA-ST regimen results in improved renal function and renal histology.Table 1Histological changes at 3 years in patients receiving sirolimus-based therapy after early CsA eliminationEngraftment12 months36 monthsScore (mean ± SD)SRL+CsASRLSRL+CsASRLSRL+CsASRLCADI1.26 ± 1.600.99 ± 0.923.74 ± 1.843.53 ± 1.664.70 ± 1.86aP < 0.05 between groups, analysis of covariance, change from engraftment.3.20 ± 1.85aP < 0.05 between groups, analysis of covariance, change from engraftment.Inflammation0.11 ± 0.350.01 ± 0.060.59 ± 0.43aP < 0.05 between groups, analysis of covariance, change from engraftment.0.82 ± 0.51aP < 0.05 between groups, analysis of covariance, change from engraftment.0.64 ± 0.51bP < 0.05 between groups, analysis of covariance, change 12 to 36 months.0.50 ± 0.51bP < 0.05 between groups, analysis of covariance, change 12 to 36 months.Tubular atrophy0.08 ± 0.270.08 ± 0.190.70 ± 0.420.56 ± 0.520.77 ± 0.50a,b0.32 ± 0.41a,bIntimal proliferation0.10 ± 0.240.14 ± 0.380.46 ± 0.520.34 ± 0.390.67 ± 0.700.41 ± 0.52Glomerular sclerosis0.33 ± 0.410.23 ± 0.380.27 ± 0.540.18 ± 0.280.64 ± 0.570.37 ± 0.57Mesangial matrix0.27 ± 0.340.20 ± 0.270.47 ± 0.400.49 ± 0.360.78 ± 0.380.62 ± 0.48Fibrosis0.37 ± 0.520.33 ± 0.381.26 ± 0.631.13 ± 0.701.21 ± 0.530.99 ± 0.61Abbreviations are: CsA, cyclosporine A; SD, standard deviation; SRL, sirolimus; CADI, chronic allograft damage index. Data from Mota, Am J Transplant 4:953–961, 2004.a P < 0.05 between groups, analysis of covariance, change from engraftment.b P < 0.05 between groups, analysis of covariance, change 12 to 36 months. Open table in a new tab Abbreviations are: CsA, cyclosporine A; SD, standard deviation; SRL, sirolimus; CADI, chronic allograft damage index. Data from Mota, Am J Transplant 4:953–961, 2004. At 48 months in the RMR study45Morales J.M. Cardiovascular risk profile in patients treated with sirolimus.Kidney Int. 2005; 67: S69-S73Google Scholar, graft survival censored for loss to follow-up was significantly better after CsA withdrawal, either when including death with a functioning graft as an event (84.1% vs. 91.5%, P = 0.024, Figure 1 ) or when excluding it (90.5% vs. 96.1%, P = 0.025). The incidence of death (7.9% vs. 4.7%) or biopsy-proven acute rejection after randomization (7.0% vs. 10.2%) did not differ significantly between the SRL-CsA-ST and SRL-ST groups. As shown in Figure 2 , the calculated GFR, which included values from discontinued patients and set GFR to 0 for functional graft loss, was significantly higher (43.8 mL/min vs. 58.3 mL/min, P < 0.001) in the CsA withdrawal group. Mean arterial blood pressure (101.0 mm Hg vs. 97.6 mm Hg, P = 0.046) was lower in the SRL-ST group despite significantly less antihypertensive therapy (P < 0.001). The cumulative 4-year data demonstrated superior outcomes for renal function, stabilized lipid values, and the ongoing benefit of lower blood pressure in patients receiving SRL-ST. This was the first trial in the new immunosuppressive era to demonstrate that the protocol based on SRL and eliminating CsA 3 months after transplantation leads to significantly better graft survival, renal function, and renal histology than the CsA and SRL protocol.Figure 2Calculated GFRs (Nankivell method) in the RMR study intention-to-treat analysis.* (with permission from Morales JM, Kidney Int 67:S69–S73, 2005)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Others have explored the conversion from anticalcineurin inhibitors to SRL in patients with chronic allograft dysfunction46Diekmann F. Budde K. Oppenheimer F. et al.Predictors of success in conversion from anticalineurin inhibitor to sirolimus in chronic allograft dysfunction.Am J Transplant. 2004; 4: 1869-1875Google Scholar , 47Peddi V.R. Jensik S. Pescovitz M. et al.An open-label, pilot study evaluating the safety and efficacy of converting from calcineurin inhibitors to sirolimus in established renal allograft recipients with moderate renal insufficiency.Clin Transplant. 2005; 19: 130-136Google Scholar. Diekmann et al showed that proteinuria <800 mg/day at conversion was the only independent predictor for a positive outcome in conversion from anticalcineurin drugs to SRL in patients with chronic allograft dysfunction46Diekmann F. Budde K. Oppenheimer F. et al.Predictors of success in conversion from anticalineurin inhibitor to sirolimus in chronic allograft dysfunction.Am J Transplant. 2004; 4: 1869-1875Google Scholar. These limited data suggest that early conversion to SRL in patients with moderate insufficiency could be useful for treating chronic allograft dysfunction47Peddi V.R. Jensik S. Pescovitz M. et al.An open-label, pilot study evaluating the safety and efficacy of converting from calcineurin inhibitors to sirolimus in established renal allograft recipients with moderate renal insufficiency.Clin Transplant. 2005; 19: 130-136Google Scholar. The antiproteinuric and antiproliferative actions of angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists might be useful in combination with MMF or SRL in patients with CAN. A rat model of renal allograft showed that losartan dramatically reduces nephrotic proteinuria48Dominguez-Gil B. Ortiz M. Sierra M.P. et al.Losartan reduces massive proteinuria in kidney transplant patients: A pilot study.Transplant Proc. 2002; 34: 368-369Google Scholar, diminishes transforming growth factor-beta in patients with CAN49Campistol J.M. Inigo P. Jimenez W. et al.Losartan decreases plasma levels of TGF-beta1 in transplant patients with chronic allograft nephropathy.Kidney Int. 1999; 56: 714-719Google Scholar, and, when combined with MMF, fully protects against chronic rejection50Noris M. Azzollini N. Pezzotta A. et al.Combined treatment with mycophenoalte mofetil and an angiotension II receptor antagonist fully protects from chronic rejection in a rat model of renal allograft.J Am Soc Nephrol. 2001; 12: 1937-1946Google Scholar. A prospective study exploring the value of including losartan in the ST-TAC-MMF protocol to prevent CAN is ongoing. The role of statins as renoprotective drugs in CAN remains to be determined4Seron D. Arias M. Campistol J.M. Morales J.M. For The Spanish Chronic Allograft Nephropathy Study Group Transplantation. 2003; 76: 1588-1594Google Scholar. The introduction of the non-nephrotoxic drugs MMF and mammalian TOR inhibitors may provide new immunosuppressive strategies to improve long-term results after renal transplantation. MMF decreases the risk for developing chronic allograft failure, is useful for treating established CAN, and has a beneficial effect on allograft fibrosis.