Both metabolizing enzymes and drug transporters play important roles in modulating drug absorption, distribution, metabolism and elimination. Acting alone or in concert with each other they can affect the pharmacokinetics and pharmacodynamics of a drug. This paper will present cases from recent reviews of new drug application (NDA) and literature that exemplify the role of metabolizing enzyme−transporter interplay in a drug’s disposition, and discuss challenges in predicting drug interactions. Finally, the discussion will focus on the need to leverage current knowledge to obtain more meaningful drug interaction information.
The identification of small molecule aminohydantoins as potent and selective human β-secretase inhibitors is reported. These analogues exhibit low nannomolar potency for BACE1, show comparable activity in a cell-based (ELISA) assay, and demonstrate >100× selectivity for the other structurally related aspartyl proteases BACE2, cathepsinD, renin, and pepsin. On the basis of the cocrystal structure of the HTS-hit 2 in the BACE1 active site and by use of a structure-based drug design approach, we methodically explored the comparatively large binding pocket of the BACE1 enzyme and identified key interactions between the ligand and the protein that contributed to the affinity. One of the more potent compounds, (S)-55, displayed an IC50 value for BACE1 of 10 nM and exhibited comparable cellular activity (EC50 = 20 nM) in the ELISA assay. Acute oral administration of (S)-55 at 100 mg/kg resulted in a 69% reduction of plasma Aβ40 at 8 h in a Tg2576 mouse (p < 0.001).
MK-0674 is a potent and selective cathepsin K inhibitor from the same structural class as odanacatib with a comparable inhibitory potency profile against Cat K. It is orally bioavailable and exhibits long half-life in pre-clinical species. In vivo studies using deuterated MK-0674 show stereoselective epimerization of the alcohol stereocenter via an oxidation/reduction cycle. From in vitro incubations, two metabolites could be identified: the hydroxyleucine and the glucuronide conjugate which were confirmed using authentic synthetic standards.