Developments in small molecule immunosuppressive drugs

Most of the immunosuppressive agents used in clinic are developed from microbial secondary metabolites, such as tacrolimus, cyclosporine and so on. They have satisfactory therapeutic effects on organ transplantation and autoimmune diseases, but their clinical application is limited by their side effects. In recent years, a lot of novel small molecule immunosuppressants with higher activity and milder side effects have been developed. In this paper, small molecule immunosuppressive drugs were classified according to their targets and the mechanisms, and the development status and adverse reactions of some novel immunosuppressive drugs were reviewed. These drugs include sphingosine-1-phosphate (S1P) agonists, and the inhibitors of dihydroorotate dehydrogenase (DHODH), protein kinase C (PKC) and Janus kinase 3 (JAK3).