Significant prolongation of animal survival by combined therapy of FR167653 and cyclosporine A in rat renal allografts.

Abstract

Cyclosporine A (CsA) has improved short-term results in renal transplantation. However, its toxicities have been serious problems in clinical patients undergoing long-term administration. It is necessary to develop a nonnephrotoxic immunosuppressant that allows reducing doses of CsA. The authors tested the effect of a new pyrazolotriazin compound, FR167653 (FR), that inhibits the production of proinflammatory cytokines, using a rat renal acute-rejection model (Wistar-Lewis). The authors first examined the adverse reactions of FR in naive rats. The effect of FR monotherapy was evaluated by treating allograft recipients at a dosage of 32 or 64 mg/kg/day intraperitoneally. The synergistic effect of FR and CsA at a minimum dose was examined by treating the recipients daily with 64 mg/kg of FR and 0.1, 0.5, or 1.0 mg/kg of CsA. Long-term administration of FR caused no severe adverse reactions in naive rats at less than 96 mg/kg/day, and FR is a nonnephrotoxic but liver-toxic agent at higher doses. Monotherapy of FR (8.7+/-1.3 days) or CsA (8.7+/-1.7 days) did not influence graft survival (vs. 8.2+/-0.8 in controls, n=10). However, the combined treatment of FR and CsA significantly prolonged animal survival (>50% of animals survived a 42-day follow-up period; P<0.01 vs. all other groups, n=15/group). Immunologic analysis demonstrated the significantly decreased production of major inflammatory mediators and adhesion molecules in the allografts as compared with those of all other groups. A nonnephrotoxic agent, FR may be a promising candidate for a new combined immunosuppressive regimen that potentially reduces the amount of CsA.