Discovery of an Orally Bioavailable Benzimidazole Diacylglycerol Acyltransferase 1 (DGAT1) Inhibitor That Suppresses Body Weight Gain in Diet-Induced Obese Dogs and Postprandial Triglycerides in Humans.

Modification of a gut restricted class of benzimidazole DGAT1 inhibitor 1 led to 9 with good oral bioavailability. The key structural changes to 1 include bioisosteric replacement of the amide with oxadiazole and α,α-dimethylation of the carboxylic acid, improving DGAT1 potency and gut permeability. Since DGAT1 is expressed in the small intestine, both 1 and 9 can suppress postprandial triglycerides during acute oral lipid challenges in rats and dogs. Interestingly, only 9 was found to be effective in suppressing body weight gain relative to control in a diet-induced obese dog model, suggesting the importance of systemic inhibition of DGAT1 for body weight control. 9 has advanced to clinical investigation and successfully suppressed postprandial triglycerides during an acute meal challenge in humans.

Discovery of diamide compounds as diacylglycerol acyltransferase 1 (DGAT1) inhibitors.

Diamide compounds were identified as potent DGAT1 inhibitors in vitro, but their poor molecular properties resulted in low oral bioavailability, both systemically and to DGAT1 in the enterocytes of the small intestine, resulting in a lack of efficacy in vivo. Replacing an N-alkyl group on the diamide with an N-aryl group was found to be an effective strategy to confer oral bioavailability and oral efficacy in this lipophilic diamide class of inhibitors.

Discovery and synthesis of novel 4-aminopyrrolopyrimidine Tie-2 kinase inhibitors for the treatment of solid tumors.

The synthesis and biological evaluation of novel Tie-2 kinase inhibitors are presented. Based on the pyrrolopyrimidine chemotype, several new series are described, including the benzimidazole series by linking a benzimidazole to the C5-position of the 4-amino-pyrrolopyrimidine core and the ketophenyl series synthesized by incorporating a ketophenyl group to the C5-position. Medicinal chemistry efforts led to potent Tie-2 inhibitors. Compound 15, a ketophenyl pyrrolopyrimidine urea analog with improved physicochemical properties, demonstrated favorable in vitro attributes as well as dose responsive and robust oral tumor growth inhibition in animal models.

A new structural alert for benzimidazoles: 2,6-dimethylphenyl substituents increase mutagenic potential and time-dependent CYP3A4 inhibition risk.

A series of 2-[(2,6)-dimethylphenyl]benzimidazole analogs displayed strong potential for mutagenicity following metabolic activation in either TA98 or TA100 Salmonella typhimurium strains. The number of revertants was significantly reduced by replacing the 2,6-dimethylphenyl group with a 2,6-dichlorophenyl moiety. Time-dependent CYP3A4 inhibition was also observed with a compound containing a 2-[(2,6)-dimethylphenyl] benzimidazole ring, implying risk for this scaffold to generate reactive metabolites.

Efficient and convenient preparation of 3-aryl-2,2-dimethylpropanoates via Negishi coupling.

An efficient and convenient Negishi coupling protocol was developed for the preparation of 3-aryl-2,2-dimethylpropanoates providing easy access to key pharmaceutical intermediates that often require multi-step synthesis using conventional enolate chemistry.

Dihydrofolate reductase mutant with exceptional resistance to methotrexate but not to trimetrexate.

Two double (F31A/F34A, I60A/L67G) and one quadruple (F31A/F34A/I60A/L67G) mutant murine dihydrofolate reductases were constructed and evaluated for their ability to impart antifolate resistance. Both I60A/L67G and F31A/F34A/I60A/L67G were found to be unstable and devoid of catalytic activity. The K(i) values for F31A/F34A, methotrexate (MTX), bis-MTX, and PT-523 were found to be 10100-, 4410-, and 617-fold higher than the wild-type enzyme, respectively, but only 13.5-fold higher for trimetrexate (TMTX). These findings suggest that F31A/F34A could be used for gene therapy to render normal cells resistant to MTX but sensitive to TMTX.

Designing protein dimerizers: the importance of ligand conformational equilibria.

In an effort to elucidate the role of ligand conformation in induced protein dimerization, we synthesized a flexible methotrexate (MTX) dimer, demonstrated its ability to selectively dimerize Escherichia coli dihydrofolate reductase (DHFR), and evaluated the factors regulating its ability to induce cooperative dimerization. Despite known entropic barriers, bis-MTX proved to possess substantial conformational stability in aqueous solution (-3.8 kcal/mol >/= DeltaG(fold) >/= -4.9 kcal/mol), exerting a dominant influence on the thermodynamics of dimerization. To dimerize DHFR, bis-MTX must shift from a folded to an extended conformation. From this conclusion, the strength of favorable protein-protein interactions in bis-MTX-E. coli DHFR dimers (-3.1 kcal/mol >/= DeltaG(c) >/= -4.2 kcal/mol), and the selectivity of dimerization for E. coli DHFR relative to mouse DHFR (>10(7)) could be determined. The crystal structure of bis-MTX in complex with E. coli DHFR confirms the feasibility of a close-packed dimerization interface and suggests a possible solution conformation for the induced protein dimers. Consequently, the secondary structure of this minimal foldamer regulates its ability to dimerize dihydrofolate reductase in solution, providing insight into the complex energy landscape of induced dimerization.