Antigen recognition and activation of T cells is a key step in the immune system. Cyclosporin A, which is used clinically as an immunosuppressant, is known to repress T cell activation by inhibition of cytokine gene expression1}. In our screening for novel immunosuppressants, we isolated four novel depsipeptide congenors, NK374186A, B, B3 and C3, and showed their inhibitory activities against T cell actvation2). In this report, we name the congenors stevastelin and show their immunosuppressive effects in vitro and low toxicity in vivo.