Immunosuppressive drug-induced toxicities compromising the half-life of renal allografts

Chronic allograft dysfunction: can we use mammalian target of rapamycin inhibitors to replace calcineurin inhibitors to preserve graft function?

PURPOSE OF REVIEW

Graft loss after first year of transplantation can be due to composite of factors that may include immunological and nonimmunological factors. Among the nonimmunological factors, toxicity of immunosuppression drugs, especially calcineurin inhibitor (CNI) toxicity is perhaps the leading cause of graft dysfunction. The most common phenotype associated with progressive graft dysfunction is the development of interstitial fibrosis and tubular atrophy not otherwise specified, a hallmark finding of chronic allograft nephropathy as well as CNI toxicity. Protocol biopsies have demonstrated that histological lesions of CNI toxicity can develop as early as 3 months posttransplantation.

RECENT FINDINGS

Early detection of interstitial fibrosis and tubular atrophy offers the opportunity for replacement of the CNI with mammalian target of rapamycin inhibitors. Early detection of CNI-associated graft damage even before the onset of graft dysfunction is critical to prevent progressive nephron loss. Furthermore, the conversion to sirolimus in patients with advanced graft dysfunction may not be beneficial.

SUMMARY

Until the day transcriptomic assays and high-density microarrays are available routinely to detect the incipient graft injury, early allograft biopsy, preferably during the first 3-6 months of transplantation can detect the presence of interstitial fibrosis and tubular atrophy not otherwise specified before the onset of graft dysfunction and replacement of CNI with sirolimus could prevent the progressive nephron loss.

Conversion from Cyclosporine to Sirolimus in Stable Renal Transplant Recipients

BACKGROUND

Conversion from cyclosporine (CsA) to sirolimus (SRL) has mainly been done in clinical conditions warranting calcineurin inhibitor discontinuation. Little is known about the clinical outcome of conversion in renal transplant recipients without transplant dysfunction.

METHODS

This prospective, open-label, multicentric pilot study evaluates the safety and efficacy of converting patients with stable renal function from CsA to SRL.

RESULTS

Forty stable patients on CsA, mycophenolate mofetil (MMF) (1.5 g/day), and steroids (ST) were converted at 7.6+/-1.4 months after renal transplantation. At 1 year, graft and patient survival was 100% and the incidence of acute rejection 5%. Calculated glomerular filtration rate (GFR) increased from 54+/-18 to 66+/-16 ml/min (P<0.0001). Blood pressure remained unchanged. A gradual increase in the incidence and severity of proteinuria was observed from month 6 onwards with de novo proteinuria in 30% of the patients at 1 year. Protein excretion was below 1 g/day in 12.5%, between 1 and 3 g/day in 17.5% and above 3 g/day in 7.5% of the proteinuric cohort (P=0.0043, compared to baseline). No predictors could be identified for the development of proteinuria. All patients had a reduction in protein excretion following renin-angiotensin blockade and were continued on SRL.

CONCLUSION

Conversion of stable renal transplant recipients from a CsA-MMF-ST to a SRL-MMF-ST regimen is safe and results in improved renal function but is associated with the development of proteinuria in 30% of the patients requiring renin-angiotensin blockade.

Sirolimus does not exhibit nephrotoxicity compared to cyclosporine in renal transplant recipients

Sirolimus and cyclosporine (CsA) prevent acute rejection in man when used as primary therapies in triple drug regimens. Sirolimus does not act via the calcineurin pathway and therefore is not expected to produce the same renal side-effects. This paper presents the pooled 2-year data analysis of renal function parameters from two open-label, randomized, multicenter studies. Patients (18-68 years) receiving a primary renal allograft were randomized to receive concentration-controlled sirolimus (n = 81) or CsA (n = 80), in combination with azathioprine and steroids (n = 83), or mycophenolate mofetil (MMF) and steroids (n = 78). From week 10 through year 2, calculated glomerular filtration rate (GFR) was significantly higher in sirolimus--than in CsA-treated patients (69.3 vs. 56.8 mL/min, at 2 years, p = 0.004). Serum uric acid was significantly higher in the CsA-treated patients and magnesium was significantly lower; these parameters were more likely to be within normal limits in the sirolimus group. Mean serum potassium and phosphorus were lower in sirolimus-treated patients. In conclusion, sirolimus, when administered as primary therapy in combination with azathioprine or MMF, has a favorable safety profile compared to CsA with regards to renal function.

Randomized trial of blood eosinophil count monitoring as a guide to corticosteroid dosage adjustment after heart transplantation

BACKGROUND

Increases in blood eosinophil counts (EOS) beyond 0.06 x 10(9)/liter precede treated heart allograft rejection. An oral prednisolone dose of 0.35 mg/kg/day usually suppresses EOS below this threshold.

METHODS

We designed a randomized trial to compare our empirical protocol for steroid dose adjustment with a novel protocol guided by EOS monitoring during the first 3 months after heart transplantation. Eighty patients were randomized to either have their EOS reported and used for steroid dose adjustment (RG; n=40), or not reported (NG; n=40). RG patients had their steroid dosage increased if EOS exceeded 0.06 x 10(9)/liter.

RESULTS

RG patients had an 83% lower risk of treated rejection (P=0.035) and lower median intravenous dose of methyl-prednisolone (P=0.017) than NG during the first 6 postoperative weeks. The proportion of diagnostic increases in EOS that were followed within 2 weeks by treated rejection was 42% greater in NG than RG (P=0.0001), compatible with a direct impact of EOS-guided prednisolone dose adjustment on the risk of subsequent rejection. Overall, RG had less than half the risk of rejection of any grade (P<0.001) and significantly more rejection-free biopsies than NG (P=0.001). The mean oral prednisolone dosage was significantly greater in RG than NG during the first (P=0.014) and second (P=0.001) 6 weeks of follow-up. This did not increase the incidence of serious steroid-related side effects.

CONCLUSIONS

EOS monitoring is a simple, cheap, and effective means of optimizing steroid immunosuppression. Restriction of the EOS-guided steroid dosing protocol to periods of prolonged hospitalisation during the first 3 postoperative months should limit the requirement for higher prednisolone dosage without affecting immunosuppressive efficacy.