In vivo Pharmacodynamic and Efficacy Studies

WHIM24 PDX model, initially developed at the Washington University School of Medicine, St. Louis, and tumors were passaged in SCID mice. To develop MDA-MB-453 xenografts, five million cells were injected subcutaneously into SCID. For pharmacodynamics studies, when tumors reached 100-200 mm³, mice were treated with vehicle control or a single dose of the drug, sacrificed at the indicated time-point, and tumor tissue was harvested for analyses. For in vivo efficacy experiments, when tumors reached 80-200 mm³, mice were randomized into groups. BETi-211, BETd-246, BETd-260 or vehicle control (10% PEG400: 3% Cremophor: 87% PBS, or 2% TPGS:98% PEG200) was given at the dose and with the duration indicated. Tumor sizes and animal weights were measured 2-3 times per week. Tumor volume (mm³) = (length×width²)/2. Tumor growth inhibition was calculated as TGI (%) = (Vc-Vt)/(Vc-Vo)*100, where Vc, Vt are the median of control and treated groups at the end of the study and Vo at the start. All the in vivo studies were performed under an animal protocol (PRO00005315) approved by the University Committee on Use and Care of Animals of the University of Michigan, in accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health.