Preliminary in vivo pharmacokinetic and pharmacodynamic evaluation of a novel calcineurin-independent inhibitor of NFAT.

A-285222 (A-285) is a bis-trifluoromethyl-pyrazole (BTP), a novel class of immunosuppressive agents that inhibit NFAT activity in vitro in human and non-human primate cells through a calcineurin-independent mechanism. In this preliminary study, we treated cynomolgus monkeys with different doses of A-285 for several days. Blood was collected from all animals at different times during the study. From these samples, plasma concentrations of A-285 were measured by liquid chromatography/mass spectrometry (LC/MS), and intracellular T-cell production of the cytokines IL-2, IFN-gamma, and TNF-alpha was quantified by flow cytometry using a mitogen-stimulated whole blood assay. Marked inhibition of cytokine production occurred after administration of the first dose of A-285, and this effect was comparable to that of cyclosporine. While neurological toxic side effects were seen when the plasma concentration of A-285 exceeded 4 microg/ml, at lower plasma levels the drug was well tolerated over 2 weeks and its pharmacodynamic effects were sustained throughout this time.