Preclinical absorption, distribution, metabolism, excretion and pharmacokinetics of a novel selective inhibitor of breast cancer resistance protein (BCRP)

1. Breast Cancer resistance protein (BCRP) plays an important role in drug absorption, distribution and excretion. It is challenging to evaluate BCRP functions in preclinical models because commonly used BCRP inhibitors are nonspecific or unstable in animal plasma. 2. In this work, in vitro absorption, distribution, metabolism and elimination (ADME) assays and pharmacokinetic (PK) experiments in BCRP knockout (KO) (Abcg2^-/-) and wild-type (WT) FVB mice and Wistar rats were conducted to characterize the preclinical properties of a novel selective BCRP Inhibitor (ML753286, a Ko143 analog). 3. ML753286 is a potent inhibitor for BCRP, but not for P-glycoprotein (P-gp), organic anion-transporting polypeptide (OATP) or major cytochrome P450s (CYPs). It has high permeability, but is not an efflux transporter substrate. ML753286 has low to medium clearance in rodent and human liver S9 fractions, and is stable in plasma cross species. BCRP inhibition affects oral absorption and clearance of sulfasalazine in rodents. A single dose of ML753286 at 50-300 mg/kg orally, and at 20 mg/kg intravenously or 25 mg/kg orally inhibits BCRP functions in mice and rats, respectively. 4. These findings confirm that ML753286 is a useful selective inhibitor to evaluate BCRP/BCRP activity in vitro and in rodent model systems.