Low-dose sirolimus and tacrolimus in kidney transplantation: first results of a single-center experience

Use of sirolimus in solid organ transplantation

Sirolimus is a mammalian target of rapamycin (mTOR) inhibitor that inhibits cell cycle progression and has proven to be a potent immunosuppressive agent for use in solid organ transplant recipients. The drug was initially studied as an adjunct to ciclosporin (cyclosporine) to prevent acute rejection in kidney transplant recipients. Subsequent studies have shown efficacy when combined with a variety of other immunosuppressive agents. The most common adverse effects of sirolimus are hyperlipidaemia and myelosuppression. The drug has unique antiatherogenic and antineoplastic properties, and may promote immunological tolerance and reduce the incidence of chronic allograft nephropathy. Although sirolimus is relatively non-nephrotoxic when administered as monotherapy, it pharmacodynamically enhances the toxicity of calcineurin inhibitors. Ironically, the drug has been used to facilitate calcineurin inhibitor-free protocols designed to preserve renal function after solid organ transplantation. Whether sirolimus can be used safely over the long term with low doses of calcineurin inhibitors requires further study. The use of sirolimus as a corticosteroid-sparing agent also remains to be proven in controlled trials. Postmarketing studies have revealed a number of unforeseen adverse effects including impaired wound healing and possibly proteinuria, oedema, pneumonitis and thrombotic microangiopathy. Overall, sirolimus is a powerful agent when used judiciously with other available immunosuppressants. As is true for all immunosuppressive drugs available for treatment of solid organ transplant recipients, the efficacy of the drug must be balanced against its considerable adverse effects.

Tacrolimus combined with two different dosages of sirolimus in kidney transplantation: results of a multicenter study

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.

Clinical application of sirolimus in renal transplantation: an update

In addition to an analysis of the final results of phase I/II and phase III clinical trials of sirolimus (SRL), this review focuses on the recent results of several studies in renal transplantation, which include diverse combinations of SRL with other immunosuppressive agents. While SRL was initially introduced as an adjunctive agent to calcineurin inhibitors, it is now serving as the base for therapies that spare or avoid these nephrotoxic drugs. However, to optimize the use of SRL as base therapy, further work is necessary to determine target concentrations, requirement for concomitant steroids and/or nucleoside synthesis blockers, and countermeasure therapy to overcome the drug's adverse effects.

Sirolimus addition is beneficial for renal allograft dysfunction due to simultaneous acute rejection episode and calcineurin inhibitor nephrotoxicity

We report a diabetic renal transplant recipient who experienced an episode of acute allograft rejection in the 6th month posttransplant when there was an attempt at steroid withdrawal. The acute rejection was steroid resistant. Furthermore calcineurin inhibitor nephrotoxicity was exacerbated by rescue therapy with tacrolimus conversion. The allograft dysfunction ultimately stabilized upon institution of sirolimus and minimization of tacrolimus.

Comparison of sirolimus-based calcineurin inhibitor-sparing and calcineurin inhibitor-free regimens in cadaveric renal transplantation

INTRODUCTION

This study examines the efficacy and toxicity of sirolimus used as primary immunosuppression in combination with reduced dose tacrolimus (calcineurin inhibitor [CI]-sparing regimen) or mycophenolate mofetil (CI-free regimen) in high-risk cadaveric renal transplantation.

METHODS

Seventy subjects were treated in a quadruple sequential protocol in which 41 were treated with a CI-sparing regimen and 29 were treated with a CI-free regimen. The efficacy and toxicity profiles of these regimens were prospectively monitored and compared.

RESULTS

The study consisted of African Americans (71%), cadaveric donors (100%), donors aged more than 50 years (30%), and patients with delayed graft function (47%). At 1 year, patient survival, graft survival, and incidence of biopsy-proven acute rejection were 98%, 80%, and 10%, respectively, in the CI-sparing group and 100%, 89%, and 7%, respectively, in the CI-free group. Three-month protocol biopsies were performed in 41% (17/41) and 67% (20/29) of the subjects in the CI-sparing and CI-free groups, respectively. Subclinical rejection was detected in 6% (1/17) and 15% (3/20) of the subjects in the CI-sparing and CI-free groups, respectively. Histologic evidence of chronic allograft nephropathy was more prevalent in the CI-sparing group. At 1 year, the mean estimated creatinine clearance was higher in the CI-free group than in the CI-sparing group (72.4 +/-20.0 mL/min vs. 50.5 +/-20.8 mL/min, P <0.01). The two regimens had similar toxicity profiles (hospital readmission, infection, wound complications, and metabolic complications).

CONCLUSIONS

Both sirolimus-based CI-sparing and CI-free regimens are safe and effective in a population with high immunologic risk. The CI-free regimen is associated with better renal function at 1 year post-transplant. Long-term follow-up will aid in determining the risk and benefit ratio of these regimens.

Therapeutic monitoring of sirolimus: its contribution to optimal prescription

It is now common practice to measure immunosuppressive drugs in blood as a guide to therapy. The immunosuppressive drug sirolimus, recently approved for use following kidney transplantation, was developed in the context of this clinical approach. Throughout the early clinical studies, validated analytical techniques based on chromatographic techniques were used to measure the drug. After a brief period in which an immunoassay was available, routine measurements are again being performed by chromatographic assays. In this article the use of blood concentration measurements in the assessment of the early and pivotal clinical trials of the drug is documented. Then, the rationale for the routine monitoring of the drug in clinical practice, a regulatory requirement in some countries, is set out. It is concluded that the development of this compound has benefited from experience gained during the pharmacokinetic assessment of other immunosuppressive drugs. The pharmacokinetic data accumulated on sirolimus have been a key element in formulating guidelines on dosing with this drug, both when used in combination with cyclosporine and when used after cyclosporine withdrawal.

Ten years of sirolimus therapy in orthotopic liver transplant recipients

BACKGROUND

Sirolimus therapy has been used in orthotopic liver transplant (OLT) recipients diagnosed with a variety of diseases; chronic graft rejection (CR), calcineurin associated renal toxicity, preemptive immune suppression, calcineurin related neurotoxicity, preemptive therapy in transplant recipients with history of hepatocellular carcinoma, and steroid resistant allograft rejection.

METHODS

A search for the medical literature and experiences involving sirolimus was done.

RESULTS

Several animal and human reports evaluating the use sirolimus in liver transplant recipients are found and discussed.

CONCLUSION

Sirolimus has been used for multitude of indications, primarily based on anecdotal experiences. However, reports of sirolimus related side effects have decreased the transplant communities' enthusiasm towards promoting this agent as a safe immune suppression agent.

Improved freedom from rejection after a loading dose of sirolimus

BACKGROUND

Sirolimus (SIR) in combination with cyclosporine reduces the incidence of acute rejection in renal transplant recipients. Limited data are available regarding SIR in combination with tacrolimus (TAC).

METHODS

A single-center, retrospective review of renal transplant recipients receiving SIR, TAC, and corticosteroids postoperatively was conducted. A total of 118 consecutive renal transplant recipients were included on the basis of availability of day 1 SIR dose information. Seventy-seven patients received an SIR loading dose (SIR-LD) immediately posttransplantation, and 41 patients did not (SIR no loading dose [SIR-NLD]).

RESULTS

The two groups showed similar demographic and transplant characteristics. SIR doses and trough levels were significantly higher in the SIR-LD patients at 1 and 7 days posttransplantation; however, no differences occurred beyond day 7. Patients receiving an SIR-LD experienced significantly better freedom from rejection at 1, 3, and 6 months posttransplantation (P<0.05). This rejection benefit in the SIR-LD group was independent of donor source and use of antibody induction. SIR-LD patients experienced fewer serious infections (12% SIR-LD vs. 27% SIR-NLD, P=0.04) and a lower incidence of delayed graft function (21% SIR-LD vs. 39% SIR-NLD, P<0.05). No significant differences in serum creatinine, hemoglobin, and platelet counts occurred in the first 180 days posttransplantation, but the patients in the SIR-NLD group experienced lower hemoglobin levels at day 30 than those in the SIR-LD group (10.8 g/dL SIR-LD vs. 9.7 g/dL SIR-NLD, P=0.03).

CONCLUSION

SIR-LD significantly improves early posttransplantation freedom from rejection in renal transplant recipients without increasing other complications.

Therapeutic drug monitoring of immunosuppressive drugs in kidney transplantation

PURPOSE OF REVIEW

Drug monitoring has become an accepted adjunct to optimizing therapy with immunosuppressive drugs. This review assesses publications that relate to the analytical techniques used to measure cyclosporin, tacrolimus, mycophenolic acid, sirolimus and everolimus, as well as the clinical data obtained for these drugs. For all of these drugs there has been a substantial and continuing investment in assessing the clinical value of drug monitoring.

RECENT FINDINGS

Fundamental controversies still persist regarding which time point to use for monitoring. The most significant single development has been the move towards using a timed blood sample 2 h after drug administration (C2) to monitor cyclosporin therapy with the Neoral formulation. The favourable clinical results obtained with this approach have had an impact on reevaluating monitoring data for some of the other drugs. The newest drugs to reach clinical evaluation, sirolimus and everolimus, have been studied in the context of concentration-controlled dosing and there is a good rationale for their measurement. There have also been developments in the analytical techniques used, mostly to improve the selectivity of the assays or to adapt them to new monitoring strategies.

SUMMARY

Interpretation of drug concentration data is becoming ever more complex in this field as the number of potential drug combinations expands. The relatively narrow therapeutic index of these agents and the ever-present risk of clinically significant pharmacokinetic drug interactions makes drug monitoring an important aspect of their prescription.