A phenotypic drug discovery study on thienodiazepine derivatives as inhibitors of T cell proliferation induced by CD28 co-stimulation leads to the discovery of a first bromodomain inhibitor.

A phenotypic screening of thienodiazepines derived from a hit compound found through a binding assay targeting co-stimulatory molecules on T cells and antigen presenting cells successfully led to the discovery of a thienotriazolodiazepine compound (7f) possessing potent immunosuppressive activity. A chemical biology approach has succeeded in revealing that 7f is a first inhibitor of epigenetic bromodomain-containing proteins. 7f is expected to become an anti-cancer agent as well as an immunosuppressive agent.