Amiselimod (MT-1303), a Novel Sphingosine 1-Phosphate Receptor-1 Modulator, Potently Inhibits the Progression of Lupus Nephritis in Two Murine SLE Models

Amiselimod (MT-1303) is a novel and selective sphingosine 1-phosphate receptor-1 (S1P₁) modulator with a more favorable cardiac safety profile than Other S1P₁ receptor modulators. In this study, we evaluated the effects of MT-1303 on the progression of lupus nephritis in two well-known murine systemic lupus erythematosus (SLE) models, MRL/lpr and NZBWF1 mice, compared with those of FK506. Daily oral doses of 0.1 and 0.3 mg/kg MT-1303 not only inhibited the development of lupus nephritis when administered before onset in MRL/lpr and NZBWF1 mice but also improved symptoms of lupus nephritis when administered after onset in MRL/lpr mice. Its efficacy in these models was more potent or comparable to that of FK506 (1 and 3 mg/kg). In histological analysis, treatment with MT-1303 inhibited infiltration of T cells into the kidneys, mesangial expansion, and glomerular sclerosis. MT-1303 treatment resulted in a marked reduction in T cells and B cells in the peripheral blood and significantly inhibited increases in the number of plasma cells in the spleen and T cells in the kidneys. In addition, administration of MT-1303 suppressed elevations in serum anti-dsDNA antibody levels in MRL/lpr mice, but not in NZBWF1 mice. Our findings show that MT-1303 exhibits marked therapeutic effects on lupus nephritis in two SLE models, likely by reducing the infiltration of autoreactive T cells into the kidneys. These results suggest that MT-1303 has the potential to be used as a therapeutic agent for patients suffering from SLE, including lupus nephritis.