Birabresib (MK-8628) is a synthetic, small molecule inhibitor of the BET (Bromodomain and Extra-Terminal) family of bromodomain-containing proteins 2, 3 and 4 with potential antineoplastic activity.

BRDs:10-19 nM(EC50)

Birabresib inhibits the binding of BRD2, BRD3, and BRD4 to AcH4 with IC50 ranging from 92 to 112 nM, and inhibits the growth of a variety of human cancer cell lines with GI50 ranging from 60 to 200 nM. [1] Birabresib results in rapid down-regulation of c-MYC expression, and show the synergistic anti-proliferative effects in combination with ALK inhibitors in ALKpos ALCL cell lines. [2]

OTX015 (p.o.) significantly inhibits the growth of Ty82 BRD-NUT midline carcinoma tumors in nude mice by 79% at 100 mg/kg qd and 61% at 10 mg/kg bid, respectively. [1]

TR-FRET Assay [1]: To assess binding of OTX015 to BRD2, BRD3, and BRD4, BRD-expressing CHO cell lysate (from CHO cells transfected with expression plasmids for Flag-tagged BRD2, BRD3, or BRD4 or vector alone), europium-conjugated anti-Flag antibody, XL-665-conjugated streptavidin, and biotinylated OTX015 are incubated at room temperature for 0.2 to 2 h. Fluorescence is measured by TR-FRET using an EnVision 2103 Multilabel Reader and EC50 for binding is calculated by nonlinear regression using PRISM version 5.02.

Effects of OTX015 on cancer cell proliferation are evaluated by incubating human tumor cells for 72 h with increasing concentrations of OTX015 and assessing proliferation using a tetrazolium salt (WST-8)-based colorimetric assay.(Only for Reference)