Identification of potent, nonabsorbable agonists of the calcium-sensing receptor for GI-specific administration.

Modulation of gastrointestinal nutrient sensing pathways provides a promising a new approach for the treatment of metabolic diseases including diabetes and obesity. The calcium-sensing receptor has been identified as a key receptor involved in mineral and amino acid nutrient sensing and thus is an attractive target for modulation in the intestine. Herein we describe the optimization of gastrointestinally restricted calcium-sensing receptor agonists starting from a 3-aminopyrrolidine-containing template leading to the identification of GI-restricted agonist 19 (GSK3004774).

Discovery of a highly potent, nonabsorbable apical sodium-dependent bile acid transporter inhibitor (GSK2330672) for treatment of type 2 diabetes.

The apical sodium-dependent bile acid transporter (ASBT) transports bile salts from the lumen of the gastrointestinal (GI) tract to the liver via the portal vein. Multiple pharmaceutical companies have exploited the physiological link between ASBT and hepatic cholesterol metabolism, which led to the clinical investigation of ASBT inhibitors as lipid-lowering agents. While modest lipid effects were demonstrated, the potential utility of ASBT inhibitors for treatment of type 2 diabetes has been relatively unexplored. We initiated a lead optimization effort that focused on the identification of a potent, nonabsorbable ASBT inhibitor starting from the first-generation inhibitor 264W94 (1). Extensive SAR studies culminated in the discovery of GSK2330672 (56) as a highly potent, nonabsorbable ASBT inhibitor which lowers glucose in an animal model of type 2 diabetes and shows excellent developability properties for evaluating the potential therapeutic utility of a nonabsorbable ASBT inhibitor for treatment of patients with type 2 diabetes.

Discovery of 6,7-dihydro-5H-pyrrolo[2,3-a]pyrimidines as orally available G protein-coupled receptor 119 agonists.

GPR119 is a 7-transmembrane receptor that is expressed in the enteroendocrine cells in the intestine and in the islets of Langerhans in the pancreas. Indolines and 6,7-dihydro-5H-pyrrolo[2,3-a]pyrimidines were discovered as G protein-coupled receptor 119 (GPR119) agonists, and lead optimization efforts led to the identification of 1-methylethyl 4-({7-[2-fluoro-4-(methylsulfonyl)phenyl]-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidin-4-yl}oxy)-1-piperidinecarboxylate (GSK1104252A) (3), a potent and selective GPR119 agonist. Compound 3 showed excellent pharmacokinetic properties and sufficient selectivity with in vivo studies supporting a role for GPR119 in glucose homeostasis in the rodent. Thus, 3 appeared to modulate the enteroinsular axis, improve glycemic control, and strengthen previous suggestions that GPR119 agonists may have utility in the treatment of type 2 diabetes.

Synthesis and SAR of Benzisothiazole- and Indolizine-ß-d-glucopyranoside Inhibitors of SGLT2.

A series of benzisothiazole- and indolizine-ß-d-glucopyranoside inhibitors of human SGLT2 are described. The synthesis of the C-linked heterocyclic glucosides took advantage of a palladium-catalyzed cross-coupling reaction between a glucal boronate and the corresponding bromo heterocycle. The compounds have been evaluated for their human SGLT2 inhibition potential using cell-based functional transporter assays, and their structure-activity relationships have been described. Benzisothiazole-C-glucoside 16d was found to be an inhibitor of SGLT2 with an IC50 of 10 nM.

Mechanisms of idiosyncratic drug reactions: the case of felbamate.

Idiosyncratic drug reactions (IDR) are a specific type of drug toxicity characterized by their delayed onset, low incidence and reactive metabolite formation with little, if any, correlation between pharmacokinetics or pharmacodynamics and the toxicological outcome. As the name implies, IDR are unpredictable and often result in the post marketing failure of otherwise useful therapies. Examples of drugs, which have failed as a result of IDR in recent years, include trovafloxacin, zileuton, troglitazone, tolcapone and felbamate. To date there exists no pre-clinical model to predict these adverse drug reactions and a mechanistic understanding of these toxicities remains limited. In an attempt to better understand this class of drug toxicities and gain mechanistic insight, we have studied the IDR associated with a model compound, felbamate. Our studies with felbamate are consistent with the theory that compounds which cause IDR undergo bioactivation to a highly reactive electrophilic metabolite that is capable of forming covalent protein adducts in vivo. In additon, our data suggest that under normal physiological conditions glutathione plays a protective role in preventing IDR during felbamate therapy, further emphasizing a correlation between reactive metabolite formation and a toxic outcome. Clinical studies with felbamate have been able to demonstrate an association between reactive metabolite formation and a clinically relevant toxicity; however, additional research is required to more fully understand the link between reactive metabolite formation and the events which elicit toxicity. Going forward, it seems reasonable that screening for reactive metabolite formation in early drug discovery may be an important tool in eliminating the post-marketing failure of otherwise useful therapies.

Interaction between human serum albumin and the felbamate metabolites 4-Hydroxy-5-phenyl-[1,3]oxazinan-2-one and 2-phenylpropenal.

Felbamate is an anti-epileptic drug associated with hepatotoxicity and aplastic anemia. These toxicities are believed to be mediated by the formation of the reactive species 2-phenylpropenal. 4-Hydroxy-5-phenyl-[1,3]oxazinan-2-one is a metabolic precursor for 2-phenylpropenal. 4-Hydroxy-5-phenyl-[1,3]oxazinan-2-one exists in equilibrium with 3-oxo-2-phenylpropyl carbamate, which can undergo beta-elimination to form 2-phenylpropenal. The work presented here investigates the interaction between 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one and human serum albumin (HSA). HSA (40 mg/mL) was found to decrease the half-life of 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one from 4.57 +/- 0.44 h to 1.07 +/- 0.10 h at pH 7.4. This decrease in the half-life of 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one was due to increased beta-elimination of 3-oxo-2-phenylpropyl carbamate, presumably through HSA-mediated general base catalysis. The k(cat) for HSA-catalyzed decomposition of 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one was determined to be 12.04 min(-)(1) M(-)(1). Competitive binding assays using warfarin and ibuprofen showed that HSA-catalyzed decomposition of 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one is dependent on the subdomain IIA binding site of HSA. LC/MS/MS analyses of trypsin digests of HSA incubations with either 4-hydroxy-5-phenyl-[1,3]oxazinan-2-one or 2-phenylpropenal identified HSA-2-phenylpropenal adducts formed specifically at residues His-242 and His-247. These HSA-2-phenylpropenal adducts were found to be slowly reversible, with a decrease in alkylation of 74.0 +/- 0.6% after extensive dialysis. Interestingly, only the bis-adduct (His-242 and His-247) could be identified after dialysis. These results demonstrate the first direct example of 2-phenylpropenal conjugation to a human protein in vitro and suggest the possibility that HSA may be involved in the development of felbamate toxicity either by antigen formation or as a route of detoxification of 2-phenylpropenal.