ABSTRACT
Molecular modeling in combination with X-ray crystallographic information was employed to identify a region of the kinesin spindle protein (KSP) binding site not fully utilized by our first generation inhibitors. We discovered that by appending a propylamine substituent at the C5 carbon of a dihydropyrazole core, we could effectively fill this unoccupied region of space and engage in a hydrogen-bonding interaction with the enzyme backbone. This change led to a second generation compound with increased potency, a 400-fold enhancement in aqueous solubility at pH 4, and improved dog pharmacokinetics relative to the first generation compound.
Subject(s)
Drug Design , Kinesins/antagonists & inhibitors , Pyrazoles/chemistry , Pyrazoles/pharmacology , Alkylation , Allosteric Site , Amination , Animals , Crystallography, X-Ray , Dogs , Hydroxylation , Kinesins/chemistry , Kinesins/metabolism , Mitosis , Models, Molecular , Molecular Structure , Pyrazoles/chemical synthesis , Pyrazoles/pharmacokinetics , Solubility , Structure-Activity Relationship , WaterABSTRACT
Optimization of high-throughput screening (HTS) hits resulted in the discovery of 3,5-diaryl-4,5-dihydropyrazoles as potent and selective inhibitors of KSP. Dihydropyrazole 15 is a potent, cell-active KSP inhibitor that induces apoptosis and generates aberrant mitotic spindles in human ovarian carcinoma cells at low nanomolar concentrations. X-ray crystallographic evidence is presented which demonstrates that these inhibitors bind in an allosteric pocket of KSP distant from the nucleotide and microtubule binding sites.
