In vitro activity: I-BET-762 is an inhibitor for BET (bromodomain and extra terminal domain) proteins, BRD2, BRD3 and BRD4, binds to the tandem bromodomains of BET with Kd of 50.5–61.3 nM, displaces a tetra-acetylated H4 peptide prebound to tandem bromodomains of BET with IC50 of 32.5–42.5 nM in FRET analysis. I-BET-762 occupies the acetyl-lysine binding pocket of BET proteins and inhibits binding of BET proteins to acetylated histones, thus disrupts the formation of the chromatin complexes essential for expression of inflammatory genes. I-BET-762 treatment during the first 2 d of differentiation alters CD4+ T-cell cytokine production, up-regulated expression of several antiinflammatory gene products and down-regulated expression of several proinflammatory cytokines.

Kinase Assay: Fluorescence resonance energy transfer (FRET) titrations. I-BET is titrated against BRD2 (200 nM), BRD3 (100 nM) and BRD4 (50 nM) in 50 mM HEPES pH7.5, 50 mM NaCl, 0.5 mM CHAPS in the presence of tetra-acetylated Histone H4 peptide (200 nM). After equilibrating for 1 hour, the bromodomain protein : peptide interaction is detected using FRET following the addition of 2nM Europium cryptate labelled streptavidin and 10 nM XL-665-labelled anti-6His antibody in assay buffer containing 0.05% (v/v) BSA and 400 mM KF. Plates are read using an Envision Plate reader (excitation 320 nm, emission 615 nm and 665 nm).

Cell Assay: CD4+ T cells are isolated from lymph nodes and spleens of 10- to 12-wk old mice and activated with plate bound anti-CD3 and anti-CD28 antibodies in the presence of indicated cytokines. I-BET-762 compounds is included during the 60–72 h of initial activation. Over the course of 5 d of T-cell culture and expansion, the compounds is diluted 12-fold relative to the starting concentrations.