FK778 CONTROL ACUTE REJECTION AFTER RAT LIVER ALLOTRANSPLANTATION INTERACTING WITH FK506 POSITIVELY

Abstract

P1128 Aims: FK778 is one of synthetic malononitrilamide derives from A771726, which is an active metabolite of leflunomide. This agent is used for kidney and heart transplantation and acute or chronic GVHD proved to prevent immunoreactions. The efficacy of FK778 for preventing rejection after liver transplantation was studied. In addition, the synergistic effect of FK778 with FK506 for inhibition of immunoreaction after rat liver transplantation was examined. Methods: Lewis livers were orthotopically transplanted into Brown-Norway under a 7 day-course of 0 (U), 10 (M1), 20 (M2) or 30 (M3) of FK778 (mg/kg BW) oral treatments. In addition, recipients were treated with 0 (UL) and 20 (M2L) from day 7 to 13 for rescue experiment. To examine the synergistic effect of FK778 with FK506, following three groups were administrated FK778 (mg/kg BW) / FK506 (mg/kg BW) under 7 day-course; 0/ 0.125 (T), 10/ 0.125 (TM1) and 20/ 0.125 (TM2). For exam of the graft state, serum AST and ALT were measured and rejection activity index (RAI) based on Banff’s schema was scored. Lymphocyte proliferations in grafts and recipient spleens were analyzed by BrdU uptake. Donor hepatocyte specific IgM were measured using ELISA. Serum trough level of FK778 was examined by HPLC. Results: RAI score was suppressed by FK778 treatment in dose dependent manners (U; 8.2±0.8, M1; 5.6±1.1, M2; 1.4±0.9, M3; 0.8±0.9). Infiltrates in the graft and proliferating splenocytes were decreased remarkably in M1 rats and diminished in M2 and M3 rats. AST and ALT value were both jumped up at U and M1. AST and ALT values of M2 and M3 maintained as normal level. Serum total protein levels of U, M1 and M2 rats were almost nearly equal to that of normal. Only the serum protein level of M3 were remarkable low (P < 0.01 vs.M2). Four of M3 rats suffered from intestinal bleeding with high trough levels (over 4.0 mmol/L) of FK778. Donor specific IgM production was suppressed in dose dependent manners. In rescue experiment, RAI scores were decreased by the M2L treatment (P<0.05 vs. UL). Number of BrdU+ cells in the M2L graft and spleen were almost equal to that of M2 graft and spleen. AST and ALT values were improved by the ML treatment. The RAI scores of the combination therapy (TM1; 3.8±1.5, TM2; 0.8±0.5) were more improved than that of T (4.8±1.0). By FK778 treatment with/ without FK506, number of BrdU+ cells in graft and spleen significantly decreased. Number of BrdU+ cells of TM1 and TM2 in the graft and spleen expressed significantly smaller population than that of T. Especially RAI score and number of BrdU+ cells in graft and spleen of TM2 were suppressed as M3 level without adverse effects. TM2 treatment maintained serum AST and ALT values. IgM value was not be influenced by additional FK506 treatment and was determined by administrated FK778 dose. Conclusions: FK778 was effective for prevention from acute rejection and rescue from ongoing rejection after rat liver transplantation. Appropriate dose was 20 mg/kg BW. FK778 suppressed IgM production by itself. Combination therapy was more useful than FK778 monotherapy.