Mizoribine is an inhibitor of inosine monophosphate dehydrogenase (IMPDH) that exhibits immunosuppressive and, potentially, antifungal activities. Mizoribine is used clinically in organ transplantations and to treat rheumatoid arthritis and lupus. In synovial cells, mizoribine decreases levels of IL-6 and matrix metalloproteinase 1 (MMP1). Mizoribine also inhibits proliferation of mesangial cells, decreasing expression of cyclin D1, skp2, and CDK2; it also increases expression of p27. Additionally, this compound may decrease proliferation of species of Candida and Aspergillus.