Robert H. Stoffel

Correlation of High-Throughput Pregnane X Receptor (PXR) Transactivation and Binding Assays

Pregnane X receptor (PXR) transactivation and binding assays have been developed into high-throughput assays, which are robust and reproducible (Z′ > 0.5). For most compounds, there was a good correlation between the results of the transactivation and binding assays. EC50 values of compounds in the transactivation assay correlated reasonably well with their IC50 values in the binding assay. However, there were discrepancies with some compounds showing high binding affinity in the binding assay translated into low transactivation. The most likely cause for these discrepancies was an agonist-dependent relationship between binding affinity and transactivation response. In general, compounds that bound to human PXR and transactivated PXR tended to be large hydrophobic molecules.

Eleven Amino Acid Glucagon-like Peptide-1 Receptor Agonists with Antidiabetic Activity

Glucagon-like peptide 1 (GLP-1) is a 30 or 31 amino acid peptide hormone that contributes to the physiological regulation of glucose homeostasis and food intake. Herein, we report the discovery of a novel class of 11 amino acid GLP-1 receptor agonists. These peptides consist of a structurally optimized 9-mer, which is closely related to the N-terminal 9 amino acids of GLP-1, linked to a substituted C-terminal biphenylalanine (BIP) dipeptide. SAR studies resulted in 11-mer GLP-1R agonists with similar in vitro potency to the native 30-mer. Peptides 21 and 22 acutely reduced plasma glucose excursions and increased plasma insulin concentrations in a mouse model of diabetes. These peptides also showed sustained exposures over several hours in mouse and dog models. The described 11-mer GLP-1 receptor agonists represent a new tool in further understanding GLP-1 receptor pharmacology that may lead to novel antidiabetic agents.

Discovery of small molecule benzimidazole antagonists of the chemokine receptor CXCR3

High-throughput screening identified a low molecular weight antagonist of CXCR3 displaying micromolar activity in a membrane filtration-binding assay. Systematic modification of the benzimidazole core and tethered acetophenone moiety established tractable SAR of analogs with improved physicochemical properties and sub-micromolar activity across both human and murine receptors.

Scalable Synthesis and Isolation of the Four Stereoisomers of Methyl 1-Amino-3-(4-bromophenyl)cyclopentanecarboxylate, Useful Intermediates for the Synthesis of S1P1 Receptor Agonists

The individual isomers of methyl 1-amino-3-(4-bromophenyl)cyclopentanecarboxylate are useful intermediates for the synthesis of S1P1 receptor agonists. Herein we describe a scalable synthesis and isolation of each of the four stereoisomers of this compound in gram quantities with >98% ee and de. The utility of this approach is demonstrated by the synthesis of ((1R,3R)-1-amino-3-(4-octylphenyl)cyclopentyl)methanol in 7 steps, 11% overall yield, and >98% ee and de.

Lead identification of 2-iminobenzimidazole antagonists of the chemokine receptor CXCR3.

Modification of a 2-iminobenzimidazole series derived from an HTS hit resulted in compounds with improved in-vitro species selectivity. Incorporation of an 8-quinoline amide and conformational rigidification of an aliphatic tether furnished potent compounds suitable for further lead optimization.

Discovery and optimization of (R)-prolinol-derived agonists of the Growth Hormone Secretagogue receptor (GHSR).

The discovery and optimization of a novel series of prolinol-derived GHSR agonists is described. This series emerged from a 11,520-member solid-phase library targeting the GPCR protein superfamily, and the rapid optimization of low micromolar hits into single-digit nanomolar leads can be attributed to the solid-phase synthesis of matrix libraries, which revealed multiple non-additive structure-activity relationships. In addition, the separation of potent diastereomers highlighted the influence of the alpha-methyl stereochemistry of the phenoxyacetamide sidechain on GHSR activity.