Strategies for the optimization of immunotherapy in kidney transplantation

Anisha E Mendonza, University of Rhode Island

Abstract

The success of kidney transplantation is dependent upon a life-long maintenance therapy with immunosuppressants. Immunosuppressants are narrow therapeutic index drugs that exhibit high intra and inter-individual variability in their pharmacokinetics (PK) and pharmacodynamics (PD). Immunosuppressant doses are adjusted by their concentrations, a practice referred to as 'therapeutic drug monitoring'. This dissertation aimed to devise novel strategies/methods to improve the monitoring of immunosuppressive agents and to compare their PK/PD between diabetic (D) and non-diabetic (ND) kidney transplant recipients. ^ A liquid chromatography tandem mass spectrometric assay was developed and validated to analyze the concentrations of mycophenolic acid (MPA) in saliva over a 12-hour dosing interval from 29 stable kidney transplant recipients. The MPA saliva concentrations were significantly associated with its total (r=0.322, p<0.001) or unbound (r=0.435, p<0.001 ) plasma concentrations indicating that salivary MPA concentrations may prove to be a non-invasive method for its monitoring. ^ Pharmacokinetic characteristics of tacrolimus (TAC) and ciclosporin (CsA) were compared between D and ND patients. Tacrolimus maximum concentration (Cmax), time to maximum concentration (tmax) and the area under the concentration time curves (AUC0-12) were comparable between D and ND patients. In contrast, absorption of CsA was delayed (t max D=128.4 vs. ND=93 min, p=0.009], AUC0-12 was lower and the unbound fraction was higher (D=1.20% vs. ND=0.72%, p=0.066) in diabetic patients. The mechanism of differential effect of diabetes on the pharmacokinetics of CsA and TAC requires further characterization. ^ Pharmacodynamic properties of CsA and TAC were assessed using intracellular cytokine staining for IL-2, TNF-alpha and IFN-gamma in mitogen stimulated CD3+ T-lymphocytes. A strong correlation was observed between the expression of IL-2 with total CsA or TAC concentrations. The degree of immunosuppression was also compared between D (n=14) and ND (n=15) patients before dose and 2-hours after dose. B-cell activity was also determined by measuring fluorescence of surface markers CD54 (ICAM-1), CD86 (B7.2) and CD95 (Fas antigen) in pokeweed mitogen stimulated CD19 cells. Expression of intracellular IL-2 in CD3 cells was significantly lower in diabetics while CD95 in B-cells were significantly lower in diabetics both at resting and stimulated states. These results indicate that diabetics require lower concentrations of immunosuppressants than non-diabetics. ^

Subject Area

Health Sciences, Pharmacy|Health Sciences, Immunology

Recommended Citation

Anisha E Mendonza, "Strategies for the optimization of immunotherapy in kidney transplantation" (2007). Dissertations and Master's Theses (Campus Access). Paper AAI3276998.
http://digitalcommons.uri.edu/dissertations/AAI3276998

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