Cell experiment:

Cells are grown in 50 μL medium as specified by the supplier for 7 days starting with 500 and with 1000 cells per well of a 384 well plate in the presence of varying concentrations of compound before measuring viability via cellular ATP levels using the cell titer glow assay.

Animal experiment:

Female CIEA-NOG mice are engrafted intravenously with 1×107 EOL-1 AML cells stably expressing luciferase and GFP. Following injection of the cells animals are randomized based on body weight (n=10/group). Treatment starts on day 5 with either 0.5% Natrosol or BI-9564 formulated with 0.5% Natrosol. All doses are calculated relative to the mouse body weight on the treatment day. BI-9564 and the vehicle control are administered orally with a dosing volume of 10 mL/kg body weight. BI-9564 is administered daily from day 5 until 17 and from day 20 until 22. Dosing is interrupted on day 18 for two days as one mouse in the treatment group reaches -15% body weight loss. Tumour load is measured 2-3 times weekly based on bioluminescence imaging. The following scoring system is used: score 0, no clinical signs; score 1, tail or hind limb weakness. Animals are sacrificed based on severity criteria including appearance of paralysis score 1 and/or body weight loss exceeding -18%. In S54 this tumor mouse model body weight changes can occur due to increased tumor load or due to intolerability.

IC50: 75 nM and 3.4 μM for BRD9 and BRD7 bromodomains, respectively

BI-9564 is a BRD9/7 specific inhibitor.

BRD7 and BRD9 are two important members of the bromodomain family protein. Both BRD7 and BRD9 have been implicated in chromatin remodeling.

In vitro: BI-9564 was identified as a BRD9/7 specific inhibitor via fragment-based screening and structure-guided design. BI-9564 was found to be bind to BRD9 with a higher affinity than to BRD7, and was negative on BET family proteins. In addition, BI-9564 demonstrated in vitro off-target selectivity to CECR2, but not in cells [1].

In vivo: In animal study, BomTac:NMRIFoxn1nu mice were given two oral doses daily and the concentration of BI-9564 in plasma was measured. Dose-dependent AUCs were obtained for BI-9564, achieving exposures that were higher compared to the EC50 level for EOL-1 cells. Moreover, when the oral treatment with BI-9564 at 180 mg/kg was initiated on day 5 and applied daily with an interruption at day 18 and 19, a significant reduction in tumour growth compared to controls was found on day 18 leading to a median tumour growth inhibition value of 52% [1].

Clinical trial: Up to now, BI-9564 is still in the preclinical development stage.

Reference:
[1] Martin LJ et al.  Structure-Based Design of an in Vivo Active Selective BRD9 Inhibitor. J Med Chem. 2016 May 26;59(10):4462-75.