Hit-to-Lead Optimization and Discovery of 5-((5-([1,1'-Biphenyl]-4-yl)-6-chloro-1H-benzo[d]imidazol-2-yl)oxy)-2-methylbenzoic Acid (MK-3903): A Novel Class of Benzimidazole-Based Activators of AMP-Activated Protein Kinase.

AMP-activated protein kinase (AMPK) plays an essential role as a cellular energy sensor and master regulator of metabolism in eukaryotes. Dysregulated lipid and carbohydrate metabolism resulting from insulin resistance leads to hyperglycemia, the hallmark of type 2 diabetes mellitus (T2DM). While pharmacological activation of AMPK is anticipated to improve these parameters, the discovery of selective, direct activators has proven challenging. We now describe a hit-to-lead effort resulting in the discovery of a potent and selective class of benzimidazole-based direct AMPK activators, exemplified by 5-((5-([1,1'-biphenyl]-4-yl)-6-chloro-1H-benzo[d]imidazol-2-yl)oxy)-2-methylbenzoic acid, 42 (MK-3903). Compound 42 exhibited robust target engagement in mouse liver following oral dosing, leading to improved lipid metabolism and insulin sensitization in mice.

Identification of diamino chromone-2-carboxamides as MCHr1 antagonists with minimal hERG channel activity.

A series of potent 2-carboxychromone-based melanin-concentrating hormone receptor 1 (MCHr1) antagonists were synthesized and evaluated for hERG (human Ether-a-go-go Related Gene) channel affinity and functional blockade. Basic dialkylamine-terminated analogs were found to weakly bind the hERG channel and provided marked improvement in a functional patch-clamp assay versus previously reported antagonists of the series.

An evaluation of 3,4-methylenedioxy phenyl replacements in the aminopiperidine chromone class of MCHr1 antagonists.

The optimization of potent MCHr1 antagonist 1 with respect to improving its in vitro profile by replacement of the 3,4-methylenedioxy phenyl (piperonyl) moiety led to the discovery of 19, a compound that showed excellent MCHr1 binding and functional potencies in addition to possessing superior hERG separation, CYP3A4 profile, and receptor cross-reactivity profiles.

Discovery and metabolic stabilization of potent and selective 2-amino-N-(adamant-2-yl) acetamide 11beta-hydroxysteroid dehydrogenase type 1 inhibitors.

Starting from a rapidly metabolized adamantane 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) inhibitor 22a, a series of E-5-hydroxy-2-adamantamine inhibitors, exemplified by 22d and (+/-)-22f, was discovered. Many of these compounds are potent inhibitors of 11beta-HSD1 and are selective over 11beta-HSD2 for multiple species (human, mouse, and rat), unlike other reported species-selective series. These compounds have good cellular potency and improved microsomal stability. Pharmacokinetic profiling in rodents indicated moderate to large volumes of distribution, short half-lives, and a pharmacokinetic species difference with the greatest exposure measured in rat with 22d. One hour postdose liver, adipose, and brain tissue 11beta-HSD1 inhibition was confirmed with (+/-)-22f in a murine ex vivo assay. Although 5,7-disubstitued-2-adamantamines provided greater stability, a single, E-5-position, polar functional group afforded inhibitors with the best combination of stability, potency, and selectivity. These results indicate that adamantane metabolic stabilization sufficient to obtain short-acting, potent, and selective 11beta-HSD1 inhibitors has been discovered.

Constrained 7-fluorocarboxychromone-4-aminopiperidine based Melanin-concentrating hormone receptor 1 antagonists: the effects of chirality on substituted indan-1-ylamines.

The incorporation of constrained tertiary amines into an existing class of N-benzyl-4-aminopiperidinyl chromone-based MCHr1 antagonists led to the identification of a series of chiral racemic compounds that displayed good to excellent functional potency, binding affinity, and selectivity over the hERG channel. Further separation of two distinct chiral racemic compounds into their corresponding pairs of enantiomers revealed a considerable selectivity for MCHr1 for one configuration, in addition to a striking difference in oral exposure between one pair of enantiomers in diet-induced obese mice. Oral administration of the most potent compound in this class in the same animal model led to significant reduction of fat mass in a semi-chronic model for weight loss.

Optimization of chromone-2-carboxamide melanin concentrating hormone receptor 1 antagonists: assessment of potency, efficacy, and cardiovascular safety.

Evaluation of multiple structurally distinct series of melanin concentrating hormone receptor 1 antagonists in an anesthetized rat cardiovascualar assay led to the identification of a chromone-2-carboxamide series as having excellent safety against the chosen cardiovascular endpoints at high drug concentrations in the plasma and brain. Optimization of this series led to considerable improvements in affinity, functional potency, and pharmacokinetic profile. This led to the identification of a 7-fluorochromone-2-carboxamide (22) that was orally efficacious in a diet-induced obese mouse model, retained a favorable cardiovascular profile in rat, and demonstrated dramatic improvement in effects on mean arterial pressure in our dog cardiovascular model compared to other series reported by our group. However, this analogue also led to prolongation of the QT interval in the dog that was linked to affinity for hERG channel and unexpectedly potent functional blockade of this ion channel.

Screening for cardiovascular safety: a structure-activity approach for guiding lead selection of melanin concentrating hormone receptor 1 antagonists.

An inactin-anesthetized rat cardiovascular (CV) assay was employed in a screening mode to triage multiple classes of melanin-concentrating hormone receptor 1 (MCHr1) antagonists. Lead identification was based on a compound profile producing high drug concentration in both plasma (>40 microM) and brain (>20 microg/g) with <15% change in cardiovascular endpoints. As a result of these stringent requirements, lead optimization activities on multiple classes of MCHr1 antagonists were terminated. After providing evidence that the cardiovascular liabilities were not a function of MCHr1 antagonism, continued screening identified the chromone-substituted aminopiperidine amides as a class of MCHr1 antagonists that demonstrated a safe cardiovascular profile at high drug concentrations in both plasma and brain. The high incidence of adverse cardiovascular effects associated with an array of MCHr1 antagonists of significant chemical diversity, combined with the stringent safety requirements for antiobesity drugs, highlight the importance of incorporating cardiovascular safety assessment early in the lead selection process.

Discovery and characterization of aminopiperidinecoumarin melanin concentrating hormone receptor 1 antagonists.

4-(1-Benzo[1,3]dioxol-5-ylmethylpiperidine-4-ylmethyl)-6-chlorochromen-2-one (7) is a potent, orally bioavailable melanin concentrating hormone receptor 1 (MCHr1) antagonist that causes dose-dependent weight loss in diet-induced obese mice. Further evaluation of 7 in an anesthetized dog model of cardiovascular safety revealed adverse hemodynamic effects at a plasma concentration comparable to the minimally effective therapeutic concentration. These results highlight the need for scrutiny of the cardiovascular safety profile of MCHr1 antagonists.

Synthesis and evaluation of urea-based indazoles as melanin-concentrating hormone receptor 1 antagonists for the treatment of obesity.

A series of urea-based N-1-(2-aminoethyl)-indazoles was synthesized and evaluated for melanin-concentrating hormone receptor 1 (MCHr1) antagonism in both binding and functional assays. Several compounds that acted as MCHr1 antagonists were identified, and optimization afforded a compound with excellent binding affinity, good functional potency, and oral efficacy in a chronic model for weight loss in diet-induced obese mice.

Identification of 2-(4-benzyloxyphenyl)-N- [1-(2-pyrrolidin-1-yl-ethyl)-1H-indazol-6-yl]acetamide, an orally efficacious melanin-concentrating hormone receptor 1 antagonist for the treatment of obesity.

Optimization of a high-throughput screening hit against melanin-concentrating hormone receptor 1 (MCHr1) led to the discovery of 2-(4-benzyloxy-phenyl)-N-[1-(2-pyrrolidin-1-yl-ethyl)-1H-indazol-6-yl]acetamide (7a). This compound was found to be a high-affinity ligand for MCHr1 and a potent inhibitor of MCH-mediated Ca(2+) release, showed good plasma and CNS exposure upon oral dosing in diet-induced obese mice, and is the first reported MCHr1 antagonist that is efficacious upon oral dosing in a chronic model of weight loss.

Synthesis and evaluation of 2-amino-8-alkoxy quinolines as MCHr1 antagonists. Part 1.

A high-throughput screen was performed in order to identify chemotypes that are bound by the melanin concentrating hormone receptor-1 (MCHr1). A novel 2-amino-8-alkoxyquinoline compound (1) was identified and subsequently optimized using a parallel and automated procedure for the rapid production of multiple analogs. The structure-activity relationships that emerged from this effort are described, along with selected pharmacokinetic parameters of compound (d)-61 when dosed orally in diet-induced obese mice.

Synthesis and evaluation of 2-amino-8-alkoxy quinolines as MCHr1 antagonists. Part 2.

The continued SAR investigation of 2-amino-8-alkoxy quinolines as melanin concentrating hormone receptor-1 (MCHr1) antagonists is reported. Prior hit-to-lead efforts resulted in the identification of 1 as a robust MCHr1 antagonist. Further delineation of the structural parameters essential for MCHr1-binding affinity of this class of nontraditional GPCR ligands resulted in the identification of compounds such as 33, 34 and 37, which demonstrate single digit nanomolar antagonism of MCHr1-mediated Ca(2+) release. The synthesis and biological evaluation of these compounds are reported.

Synthesis and evaluation of 2-amino-8-alkoxy quinolines as MCHr1 antagonists. Part 3.

Prior SAR studies on 2-amino-8-alkoxyquinoline MCHr1 antagonists demonstrated that compounds with acyclic amide-containing sidechains displayed exceptional binding and functional potency, but negligible CNS penetration. Related analogs with acyclic benzylamine-containing sidechains showed greatly improved CNS exposure, but suffered in functional potency. In this report, we demonstrate that cyclization of these benzylic amine sidechains affords compounds that combine the best elements of potency and CNS penetration among this class of antagonists. This is exemplified by compound 21, which has sub-nanomolar MCHr1 binding affinity, good functional potency, and excellent CNS exposure over 24h.

Standardization protocols and optimized precursor sets for the efficient application of automated parallel synthesis to lead optimization: a Mitsunobu example.

A strategy has been developed for the efficient application of automated parallel synthesis to specific aspects of the lead optimization processes employed in drug discovery. The method involves the synthesis of collections of compounds using sets of precursors designed to encompass established medicinal chemistry principles and that have been concurrently optimized with respect to a specific chemical transformation. The strategy is illustrated using an automated Mitsunobu protocol employing sets of aliphatic alcohols and phenols as precursors. The former has been formatted to perform simple alkyl homologation exercises, with the latter being designed for use in diversity-based studies.