Paradoxical response to tacrolimus assessed by interleukin-2 gene expression

Impact of single immunosuppressive drug withdrawal on lymphocyte immunoreactivity

BACKGROUND

Chronic rejection is a major cause of graft loss in kidney transplant recipients. Nonadherence to drug therapy is a well-recognized cause of chronic rejection leading to long-term graft dysfunction and failure for transplant recipients. Immunosuppressive medications with short half-lives that require frequent dosing, such as tacrolimus, complicate transplant regimens and may increase noncompliance. Regimens could be simplified using drugs with long half-lives requiring once-daily administration, such as sirolimus. The impact of missing doses of single agents has not been studied extensively. Erratic compliance or temporary discontinuation of immunosuppressive drugs may have significant implications for chronic rejection.

METHODS

Our study evaluated the impact of single drug withdrawal of commonly used immunosuppressive agents (sirolimus and tacrolimus) on lymphocyte responses. We analyzed lymphocyte proliferation, cytokine secretion, and adenosine triphosphate generation using a crossover study design with normal healthy patients. Lymphocyte proliferation was assessed using 5-bromo-2-deoxyuridine incorporation, and T cell function was analyzed by examining adenosine triphosphate generation.

RESULTS

Our results indicate that sirolimus exerts prolonged suppression of lymphocyte proliferation and decreased interleukin 17A that lasts up to 48 h after drug withdrawal. In comparison, tacrolimus did not have a similar effect on lymphocyte proliferation or interleukin 17A secretion.

CONCLUSION

Future analysis of sirolimus in diverse transplantation populations merits investigation.

Pharmacodynamic monitoring of calcineurin inhibition therapy: principles, performance, and perspectives

The calcineurin inhibitors (CNIs) cyclosporin A and tacrolimus are immunosuppressive drugs used extensively in allograft recipients. These drugs show large interindividual pharmacokinetic variation and are associated with severe adverse affects, including nephrotoxicity and cardiovascular disease. In current practice, CNIs are combined with other immunosuppressive drugs such as steroids and mycophenolate mofetil. Dosage is titrated based on blood concentration measurement. For further optimization of calcineurin (CN) inhibition therapy, new monitoring strategies are required. Pharmacodynamic-monitoring strategies constitute novel approaches for optimization of CNIs therapy. This review focuses on the general aspects of immunosuppressive drug pharmacodynamic monitoring and describes the methodologies used for monitoring CN inhibition therapy. Two different types of pharmacodynamic-monitoring strategies can be distinguished: (1) enzymatic strategies, which monitor inhibition of drug-target enzyme activity, and (2) immunologic strategies, which measure cellular responsiveness after in vitro simulated immunologic responses. Enzymatic tests are drug type-specific markers in which CN activity is directly determined. Immunologic strategies measure immune responsiveness at several levels, such as mRNA transcripts (intracellular) concentrations/excretion of cytokines, expression of surface activation markers, and cell proliferation. This review also discusses analytical issues and clinical experience with these techniques. The call for new methodologies to evaluate immunosuppressive therapy has led to the development of a large variety of pharmacodynamic-monitoring strategies. The first reports of their clinical relevance are available, but further understanding of the analytical and clinical variables involved are required for the development of accurate, reproducible, and clinically relevant markers.

Calcineurin inhibitor sparing in paediatric solid organ transplantation : managing the efficacy/toxicity conundrum

Despite their efficacy, the calcineurin inhibitors (CNIs) ciclosporin and tacrolimus carry a risk of debilitating adverse effects, especially nephrotoxicity, that affect the long-term outcome and survival of children who are given organ transplants. Simple reduction in dosage of CNI has little or no long-term benefit on their adverse effects, and complete withdrawal without threatening graft outcome may only be possible after liver transplantation. Until the last decade, the only option was to increase corticosteroid and/or azathioprine doses, which imposed additional long-term hazards. Considered here are the emerging generation of new agents offering an opportunity for improving long-term graft survival, minimizing CNI-related adverse events and ensuring patient well-being.A holistic, multifaceted strategy may need to be considered - initial selection and optimized use and monitoring of immunosuppressant regimens, early recognition of indicators of patient and graft dysfunction, and, where applicable, early introduction of CNI-sparing regimens facilitating CNI withdrawal. The evidence reviewed here supports these approaches but remains far from definitive in paediatric solid organ transplantation. Because de novo immunosuppression uses CNI in more than 93% of patients, reduction of CNI-related adverse effects has focused on CNI sparing or withdrawal.A recurring theme where sirolimus and mycophenolate mofetil have been used for this purpose is the importance of their early introduction to limit CNI damage and provide long-term benefit: for example, long-term renal function critically reflects that at 1 year post-transplant. While mycophenolic acid shows advantages over sirolimus in preserving renal function because the latter is associated with proteinuria, sirolimus appears the more potent immunosuppressant but also impairs early wound healing. The use of CNI-free immunosuppressant regimens with depleting or non-depleting antibodies plus sirolimus and mycophenolic acid needs much wider investigation to achieve acceptable rejection rates and conserve renal function. The adverse effects of the alternative immunosuppressants, particularly the dyslipidaemia associated with sirolimus, needs to be minimized to avoid replacing one set of adverse effects (from CNIs) with another. While we can only conjecture that judicious combinations with the second generation of novel immunosuppressants currently in development will provide these solutions, a rationale of low-dose therapy with multiple immunosuppressants acting by complementary mechanisms seems to hold the promise for efficacy with minimal toxicity until the vision of tolerance achieves reality.