In vivo evaluation of the novel calcineurin inhibitor ISA TX247 in Non-Human primates

Abstract

Background ISA TX247 is a novel calcineurin inhibitor that has shown more potency than cyclosporine in vitro. This is the first in vivo study of the effects of ISA TX247 on lymphocyte functions in non-human primates. Methods Groups of cynomolgus monkeys were treated orally twice daily for 7 days, each dose consisting of 25 mg/kg cyclosporine ( n = 5), 25 mg/kg ISA TX247 ( n = 6) or 50 mg/kg ISA TX247 ( n = 6). Levels of cyclosporine and ISA TX247 in whole blood were measured by liquid chromatography/mass spectrometry. After mitogen stimulation, lymphocyte proliferation was assessed by tritium-labeled thymidine incorporation and by flow cytometry (expression of proliferating cell nuclear antigen in cells in S/G 2M phase). Flow cytometry was also used to assess production of intracellular cytokines by T cells (interleukin-2, interferon-γ, tumor necrosis factor-α) and expression of T-cell surface activation antigens (CD25, CD71, CD11a, CD95, CD154). Results Trough ( C 14hr) and peak ( C 3hr) drug levels, as well as area under the concentration–time curve, were significantly higher for cyclosporine than ISA TX247 (370 ng/ml vs 70 ng/ml, 877 ng/ml vs 303 ng/ml and 6,262 ng · h/ml vs 1,979 ng · h/ml, respectively). On Day 7 at C 14hr, lymphocyte proliferation had been suppressed by approximately 50% in all groups compared with proliferation before treatment. Three hours after dosing, lymphocyte proliferation was inhibited significantly more by ISA TX247 (approximately 80%, with no differences between the two ISA TX247 dose levels) than by cyclosporine (65% inhibition). Similar differences between the immunosuppressive effects of ISA TX247 and cyclosporine were found for inhibition of expression of T-cell surface activation antigens. Despite lower ISA TX247 exposures compared with cyclosporine, the cyclosporine treatment only rarely suppressed cytokine production more than treatment with ISA TX247. Conclusions In non-human primates, ISA TX247 produces a greater or similar inhibition of lymphocyte proliferation, expression of T-cell activation surface antigens, and cytokine production when compared with cyclosporine, despite ISA TX247’s lower blood levels and total exposure. We conclude that ISA TX247 suppresses diverse T-cell functions more potently than cyclosporine in non-human primates in vivo.