FR235222, a fungal metabolite, is a novel immunosuppressant that inhibits mammalian histone deacetylase (HDAC). I. Taxonomy, fermentation, isolation and biological activities.

A cyclic tetrapeptide FR235222, a novel immunosuppressant, has been isolated from the fermentation broth of a fungus, Acremonium sp. No. 27082. FR235222 showed potent and selective inhibitory effects on both T cell proliferation and lymphokine production. Further study has revealed this compound exhibits potent inhibitory effects on the activity of mammalian histone deacetylases (HDACs).