Fumaric acid esters are potent immunosuppressants: inhibition of acute and chronic rejection in rat kidney transplantation models by methyl hydrogen fumarate

The effectiveness and safety of fumaric acid esters (FAEs) for the treatment of psoriasis has been demonstrated. Their mode of action, however, is poorly understood. To determine the immunomodulatory potential of calcium methyl hydrogen fumarate (CaMHF) in transplant models, we tested the compound in rat transplantation models of acute rejection (AR) and chronic rejection (CR). Orthotopic kidney transplantation was combined with contralateral nephrectomy using the strain combinations WF to BDIX (AR) and F344 to LEW (CR). Recipients were treated orally prophylactically (day-28 to day +28, AR and CR model) or therapeutically (day +30 to day+60, CR model). CaMHF significantly prolonged the time to onset of AR in the WF/BDIX model. The half-lives of the grafts were 14 days in the CaMHF group, 7 days in the placebo-treated control group and 9 days in the untreated control group (P<6.01). Three of ten CaMHF-treated rats showed permanent graft acceptance (defined as survival for >100 days) resulting in a mean survival time of >42.3+/-41.0 (P<0.01) in comparison with >28.3+/- 38.3 days in the placebo-treated group and 9.4+/-2.6 days in the untreated control group. In the F344/LEW model of chronic graft injury, only prophylactic CaMHF treatment significantly inhibited the development of CR (P=0.001; mean survival times >28.4+/-2.0 weeks, >23.9+/-6.0 weeks and >21.1+/-5.4 weeks in the prophylactic CaMHF, therapeutic CaMHF, and placebo group, respectively). By 30 weeks six of ten prophylactically treated animals were still alive, but only three of nine and one of ten were alive in the therapeutically treated and placebo-treated groups, respectively (P<0.05). These findings indicate that CaMHF treatment effectively inhibits AR and CR, and demonstrates marked in vivo immunomodulatory efficacy. Thus, FAEs should be considered as drugs showing considerable immunosuppressive efficacy. This might have implications with regard to safety issues (e.g. immune monitoring) and novel potentially suitable indications (e.g. transplantation and other immune diseases).