Medium-term outcome using sirolimus-tacrolimus combination in adult renal transplant recipients

Sirolimus enhances cyclosporine a-induced cytotoxicity in human renal glomerular mesangial cells

End Stage Renal Disease (ESRD) is an ever increasing problem worldwide. However the mechanisms underlying disease progression are not fully elucidated. This work addressed nephrotoxicity induced by the immunosuppressive agents' cyclosporine A (CsA) and sirolimus (SRL). Nephrotoxicity is the major limiting factor in long term use of CsA. SRL causes less nephrotoxicity than CsA. Therefore investigations into the differential effects of these agents may identify potential mechanisms of nephrotoxicity and means to prevent ESRD induced by therapeutic drugs. Using ELISA, Western blotting, quantitative PCR and a reporter gene assay we detailed the differential effects of CsA and SRL in human renal mesangial cells. CsA treatment increased profibrotic TGF-β1 secretion in human mesangial cells whereas SRL did not, indicating a role for TGF-β in CsA toxicity. However we observed a synergistic nephrotoxic effect when CsA and SRL were co-administered. These synergistic alterations may have been due to an increase in CTGF which was not evident when the immunosuppressive drugs were used alone. The CsA/SRL combination therapy significantly enhanced Smad signalling and altered the extracellular matrix regulator matrix metalloproteinase 9 (MMP-9). Inhibition of the ERK 1/2 pathway, attenuated these CsA/SRL induced alterations indicating a potentially significant role for this pathway.

A fast and simple high-performance liquid chromatography/mass spectrometry method for simultaneous measurement of whole blood tacrolimus and sirolimus

CONTEXT

Combined immunosuppressant therapy using tacrolimus and sirolimus has demonstrable benefits. Simultaneous chromatographic monitoring of whole blood tacrolimus and sirolimus is useful for reducing reagent consumption and turnaround time. We report here a simple and rapid method using high-performance liquid chromatography/mass spectrometry for simultaneous measurement of whole blood tacrolimus and sirolimus.

OBJECTIVE

To develop and validate a high-performance liquid chromatography/mass spectrometry method that is suitable for clinical laboratories and that is simple, rapid, and cost-effective.

DESIGN

Whole blood (80 microL) was mixed with zinc sulfate solution, followed by protein precipitation with acetonitrile containing the internal standards. After brief centrifugation, the supernatant (20 microL) was injected onto a C18 guard column. The drug and the internal standard ammonium adducts were monitored by multiple reaction monitoring. One-point calibration at levels of 200 ng/mL (249 nM) tacrolimus and 100 ng/mL (109 nM) sirolimus was prepared by adding tacrolimus and sirolimus to immunosuppressant-free whole blood.

RESULTS

The assay took 2.5 minutes per sample injection. The total imprecision was between 2.46% and 7.04% for tacrolimus and between 5.22% and 8.30% for sirolimus across the concentrations tested. No carryover was observed, and recoveries were 92% to 98% for tacrolimus and 100% for sirolimus at all levels tested. The tacrolimus was linear from 0.52 to 155.5 ng/mL (0.65-193.4 nM), and sirolimus was linear from 0.47 to 94.8 ng/mL (0.51-103.7 nM). Biases of correlations with commercial methods were within 7%.

CONCLUSIONS

This improved method is simple, fast, cost-effective, and suitable for clinical laboratories. It has been implemented for routine clinical monitoring of posttransplantation immunosuppressant therapy.

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.