In vitro activity: Previous study found that CPI-637 was potent against EP300, and its opposite enantiomer showed a over 200-fold loss in potency. Moreover, the biochemical potency of CPI-637 translated well into cells with CBP BRET EC50 of 0.3 μM, and CPI-637 demonstrated a more than 700-fold selectivity over the BET family of bromodomains. In addition, CPI-637 was also highly selective against other bromodomains, showing substantial biochemical activity only against BRD9. Furthermore, it was found that CPI-637 was able to inhibit the expression of MYC with an EC50 of 0.60 μM in a cellular assay.

Kinase Assay: CPI-637 is a potent and selective CBP/EP300 bromodomains inhibitor with IC50 of 0.03±0.01μM and 11.0±0.6 μM for CBP/EP300 and BRD4, respectively.

Cell Assay: The biochemical potency of CPI-637 translated well into cells (CBP BRET EC50 = 0.3 μM), and the compound demonstrated a>700-fold selectivity over the BET family of bromodomains (BRD4 IC50 = 11.0 ± 0.6 μM).CPI-637 was also highly selective against other bromodomains (detailed list in the Supporting Information), displaying substantial biochemical activity only against BRD9, which is acceptable, since inhibition of the BRD9 bromodomain has not been shown to produce a pronounced cellular phenotype . In a cellular assay, CPI-637 inhibits the expression of MYC, a transcription factor widely expressed in human cancer,with an EC50 of 0.60 μM, providing an orthogonal measure of the target engagement of the compound .The inactive enantiomer of CPI-637 displayed an EC50 in the same assay of>10 μM.

ACS Med Chem Lett. 2016 Mar 15;7(5):531-6.