Optimization of piperidin-4-yl-urea-containing melanin-concentrating hormone receptor 1 (MCH-R1) antagonists: Reducing hERG-associated liabilities

The discovery and optimization of piperidin-4-yl-urea derivatives as MCH-R1 antagonists is herein described. Previous work around the piperidin-4-yl-amides led to the discovery of potent MCH-R1 antagonists. However, high affinity towards the hERG potassium channel proved to be an issue. Different strategies to increase hERG selectivity were implemented and resulted in the identification of piperidin-4-yl-urea compounds as potent MCH-R1 antagonists with minimized hERG inhibition.     

Aminomethyl tetrahydronaphthalene ketopiperazine MCH-R1 antagonists--Increasing selectivity over hERG

A direct correlation between hERG binding and QTc prolongation was established for a series of aminomethyl tetrahydronaphthalene ketopiperazine MCH-R1 antagonists. Compounds within this class with greater selectivity over hERG were developed. Compound 4h proved to have the best profile, with MCH-R1 Ki = 16 nm and hERG IC50 = 25 microM.     

Aminomethyl tetrahydronaphthalene biphenyl carboxamide MCH-R1 antagonists--Increasing selectivity over hERG

Aminomethyl tetrahydronaphthalene biphenyl carboxamide MCH-R1 antagonists with greater selectivity over hERG were identified. SAR studies addressing two distinct alternatives for structural modifications leading to improve hERG selectivity are described.     

Synthesis and SAR investigations of novel 2-arylbenzimidazole derivatives as melanin-concentrating hormone receptor 1 (MCH-R1) antagonists

Compounds containing 2-arybenzimidazole ring systems linked to arylpiperidines were synthesized and evaluated as MCH-R1 antagonists. The results of structure-activity relationship studies led to the identification of compound 4c as a potent MCH-R1 antagonist (IC₅₀ = 1 nM). This compound also has good metabolic stability, and favorable pharmacokinetic and brain penetration properties. However 4c was found to be potent inhibitor of the hERG potassium channel.     

Synthesis and SAR study of pyrrolo[3,4-b]pyridin-7(6H)-one derivatives as melanin concentrating hormone receptor 1 (MCH-R1) antagonists

The discovery and optimization of novel pyrrolo[3,4-b]pyridin-7(6H)-one MCH-R1 antagonists are described. A systematic SAR study probing the effects of aryl-, benzyl- and arylthio-substituents at the 2-position of the pyrrolo[3,4-b]pyridin-7(6H)-ones led to identification of the 2-[(4-fluorophenyl)thio] derivative 7b as a highly potent MCH-R1 antagonist. This compound also has favorable pharmacokinetic properties along with a high metabolic stability and a minimal impact on CYP isoforms and hERG.     

The efficacy and cardiac evaluation of aminomethyl tetrahydronaphthalene ketopiperazines: a novel class of potent MCH-R1 antagonists

The design, synthesis, and biological studies of a novel class of MCH-R1 antagonists based on an aminotetrahydronaphthalene ketopiperazine scaffold is described. Compounds within this class promoted significant body weight reduction in mouse diet induced obesity studies. The potential for hERG blockage activity and QT interval studies in anesthetized dogs are discussed.     

Quinazolin-4-piperidin-4-methyl sulfamide PC-1 inhibitors: Alleviating hERG interactions through structure based design

PC-1 (NPP-1) inhibitors may be useful as therapeutics for the treatment of CDDP (calcium pyrophosphate dehydrate) deposition disease and osteoarthritis. We have identified a series of potent quinazolin-4-piperidin-4-ethyl sulfamide PC-1 inhibitors. The series, however, suffers from high affinity binding to hERG potassium channels, which can cause drug-induced QT prolongation. We used a hERG homology model to identify potential key interactions between our compounds and hERG, and the information gained was used to design and prepare a series of quinazolin-4-piperidin-4-methyl sulfamides that retain PC-1 activity but lack binding affinity for hERG.     

4-arylphthalazin-1(2H)-one derivatives as potent antagonists of the melanin concentrating hormone receptor 1 (MCH-R1)

A novel series of 4-arylphthalazin-1(2H)-one linked to arylpiperidines were synthesized and evaluated as MCH-R1 antagonists. The results of an extensive SAR study probing the effects of substituents on the 4-arylphthalazin-1(2H)-one C-4 aryl group led to the identification of the 4-(3,4-difluorophenyl) derivative as a highly potent MCH-R1 inhibitor with an IC(50)=1nM. However, further investigations showed that this substance has unacceptable pharmacokinetic properties including a high clearance and volume of distribution.     

Discovery of cyclopentane- and cyclohexane-trans-1,3-diamines as potent melanin-concentrating hormone receptor 1 antagonists

We herein report the optimization of cyclopentane- and cyclohexane-1,3-diamine derivatives as novel and potent MCH-R1 antagonists. Structural modifications of the 2-amino-quinoline and thiophene moieties found in the initial lead compound served to improve its metabolic stability profile and MCH-R1 affinity, and revealed unprecedented SAR when compared to other 2-amino-quinoline-containing MCH-R1 antagonists.     

Identification of a new small molecule chemotype of Melanin Concentrating Hormone Receptor-1 antagonists using pharmacophore-based virtual screening

MCH receptor is a G protein-coupled receptor with two subtypes R1 and R2. Many studies have demonstrated the role of MCH-R1 in feeding and energy homeostasis. It has been proven that oral administration of small molecule MCH-R1 antagonists significantly reduces food intake and causes a dose-dependent weight loss. In this study, two ligand-based pharmacophores were developed and validated based on recently published MCH-R1 antagonists with diverse structures. Successful pharmacophores had one hydrogen bond acceptor, one positive ionizable, one ring aromatic and two or three hydrophobic groups. These 3D-QSAR models were used for virtual screening of the ZINC chemical database resulting in the identification of nine compounds with more than 50% displacement of radiolabeled MCH at a 20 μM concentration. Moreover, four of these compounds showed antagonistic activities in Aequorin functional assay, including MH-3 which is the first MCH-R1 antagonist based on a diazaspiro[4.5]decane scaffold. The most active compounds were also docked into our previously published MCH-R1 homology model to gain insights into their binding determinants. These compounds could represent a viable starting scaffold for the design of potent MCH-R1 antagonists with improved pharmacokinetic properties as an effective treatment for obesity.     

Identification of 4-amino-2-cyclohexylaminoquinazolines as metabolically stable melanin-concentrating hormone receptor 1 antagonists

The optimization of the distance between two key pharmacophore features within our first hit compounds 1a and 2a led to the identification of a new class of potent non-peptidic antagonists for the MCH-R1, based around 4-amino-2-cyclohexylaminoquinazolines. In particular, ATC0065 (2c), N2-[cis-4-([2-[4-Bromo-2-(trifluoromethoxy)phenyl]ethyl]amino)cyclohexyl]-N4,N4-dimethylquinazoline-2,4-diamine dihydrochloride, bound with high affinity to the MCH-R1 (IC50 value of 16 nM) and showed good metabolic stability in liver microsomes from human and rat.     

Novel series of substituted biphenylmethyl urea derivatives as MCH-R1 antagonists for the treatment of obesity

We have designed and synthesized two novel series of MCH-R1 antagonists based on a substituted biphenylmethyl urea core. SAR was explored, suggesting that optimal binding with the receptor was achieved when the biphenylmethyl group and the linker were substituted on the same nitrogen of the urea moiety. Compound 1-(3'-cyano-4-biphenylmethyl)-3-(2-hydroxy-1,1-dimethylethyl)-1-{2-[1-(4-methylbenzyl)-4-piperidinyl]ethyl}urea 2t showed the best antagonist binding activity to the MCH-R1 with a 43 nM K(i).     

Hit-to-lead investigation of a series of novel combined dopamine D2 and muscarinic M1 receptor ligands with putative antipsychotic and pro-cognitive potential

We describe the discovery of a series of compounds based on 1-{3-[4-(2-oxo-2,3-dihydro-benzoimidazol-1-yl)-piperidin-1-yl]-propyl}-3,4-dihydro-1H-quinolin-2-one (3), showing combined D(2) receptor affinity and M(1) receptor agonism. Based on a strategy of controlling logP, we herein describe a hit-to-lead investigation with the aim of retaining the combined D(2)/M(1) profile, while removing the propensity of the compounds to inhibit the hERG channel, as well as at obtaining acceptable pharmacokinetic properties. Although a SAR was evident for all four parameters in question, it was not possible to separate hERG channel inhibition and D(2) receptor affinity by this effort; whilst it was feasible to obtain compounds with M(1) receptor agonism, acceptable clearance, and weak hERG inhibition.     

Lead optimization of 4-(dimethylamino)quinazolines, potent and selective antagonists for the melanin-concentrating hormone receptor 1

The optimization of a series of 4-(dimethylamino)quinazoline antagonists of the melanin-concentrating hormone receptor 1 (MCH-R1) is described. The combination of the elaboration of both the linker portion and the terminal phenyl ring provided N-(cis-4-{[4-(dimethylamino)quinazolin-2-yl]amino}cyclohexyl)-3,4-difluorobenzamide hydrochloride 28 (ATC0175), which showed excellent antagonist activity at the MCH-R1 (IC50 = 3.4 nM) as well as good selectivity over the Y5 and the alpha2A receptors.     

Synthesis and SAR of 5-aryl-furan-2-carboxamide derivatives as potent urotensin-II receptor antagonists

The synthesis and biological evaluation as potential urotensin-II receptor antagonists of a series of 5-arylfuran-2-carboxamide derivatives 1, bearing a 4-(3-chloro-4-(piperidin-4-yloxy)benzyl)piperazin-1-yl group, are described. The results of a systematic SAR investigation of furan-2-carboxamides with C-5 aryl groups possessing a variety of aryl ring substituents led to identification of the 3,4-difluorophenyl analog 1y as a highly potent UT antagonist with an IC₅₀ value of 6?nM. In addition, this substance was found to display high metabolic stability, and low hERG inhibition and cytotoxicity, and to have an acceptable PK profile.     

Discovery and SAR of potent, orally available and brain-penetrable 5,6-dihydro-4H-3-thia-1-aza-benzo[e]azulen- and 4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulen derivatives as neuropeptide Y Y5 receptor antagonists

Combination of structural elements from a potent Y5 antagonist (2) with thiazole fragments that exhibit weak Y5 affinities followed by lead optimisation led to the discovery of (5,6-dihydro-4H-3-thia-1-aza-benzo[e]azulen-2-yl)-piperidin-4-ylmethyl-amino and (4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulen-2-yl)-piperidin-4-ylmethyl-amino derivatives. Both classes of compounds are capable of delivering potent and selective orally and centrally bioavailable NPY Y5 receptor antagonists.     

Overcoming hERG activity in the discovery of a series of 4-azetidinyl-1-aryl-cyclohexanes as CCR2 antagonists

A series of 4-azetidinyl-1-aryl-cyclohexanes as potent CCR2 antagonists with high selectivity over activity for the hERG potassium channel is discovered through divergent SARs of CCR2 and hERG.     

Different structural requirements for melanin-concentrating hormone (MCH) interacting with rat MCH-R1 (SLC-1) and mouse B16 cell MCH-R

Melanin-concentrating hormone (MCH) is a neuropeptide occurring in all vertebrates and some invertebrates and is now known to stimulate pigment aggregation in teleost melanophores and food-intake in mammals. Whereas the two MCH receptor subtypes hitherto cloned, MCH-R1 and MCH-R2, are thought to mediate mainly the central effects of MCH, the MCH-R on pigment cells has not yet been identified, although in some studies MCH-R1 was reported to be expressed by human melanocytes and melanoma cells. Here we present data of a structure-activity study in which 12 MCH peptides were tested on rat MCH-R1 and mouse B16 melanoma cell MCH-R, by comparing receptor binding affinities and biological activities. For receptor binding analysis with HEK-293 cells expressing rat MCH-R1 (SLC-1), the radioligand was [125I]-[Tyr13]-MCH with the natural sequence. For B16 cells (F1 and G4F sublines) expressing B16 MCH-R, the analog [125I]-[D-Phe13, Tyr19]-MCH served as radioligand. The bioassay used for MCH-R1 was intracellular Ca2+ mobilization quantified with the FLIPR instrument, whereas for B16 MCH-R the signal determined was MAP kinase activation. Our data show that some of the peptides displayed a similar relative increase or decrease of potency in both cell types tested. For example, linear MCH with Ser residues at positions 7 and 16 was almost inactive whereas a slight increase in side-chain hydrophilicity at residues 4 and 8, or truncation of MCH at the N-terminus by two residues hardly changed binding affinity or bioactivity. On the other hand, salmonic MCH which also lacks the first two residues of the mammalian sequence but in addition has different residues at positions 4, 5, 9, and 18 exhibited a 5- to 10-fold lower binding activity than MCH in both cell systems. A striking difference in ligand recognition between MCH-R1 and B16 MCH-R was however observed with modifications at position 13 of MCH: whereas L-Phe13 in [Phe13, Tyr19]-MCH was well tolerated by both MCH-R1 and B16 MCH-R, change of configuration to D-Phe13 in [D-Phe13, Tyr19]-MCH or [D-Phe13]-MCH led to a complete loss of biological activity and to a 5- to 10-fold lower binding activity with MCH-R1. By contrast, the D-Phe13 residue increased the affinity of [D-Phe13, Tyr19]-MCH to B16 MCH-R about 10-fold and elicited MAP kinase activation as observed with [Phe13, Tyr19]-MCH or MCH. These data demonstrate that ligand recognition by B16 MCH-R differs from that of MCH-R1 in several respects, indicating that the B16 MCH-R represents an MCH-R subtype different from MCH-R1.     

Discovery of 1,3-disubstituted-1H-pyrrole derivatives as potent melanin-concentrating hormone receptor 1 (MCH-R1) antagonists

A series of 1,3-disubstituted-1H-pyrrole-based antagonists of the human Melanin-Concentrating Hormone Receptor 1 (h-MCH-R1) are reported. High-throughput screening of the AstraZeneca compound collection yielded 1, a hit with moderate affinity towards MCH-R1. Subsequent structural manipulations and SAR analysis served to rationalize potency requirements, and 12 was identified as a novel, functional MCH-R1 antagonist with favorable pharmacokinetic properties.     

1-(4-Amino-phenyl)-pyrrolidin-3-yl-amine and 6-(3-amino-pyrrolidin-1-yl)-pyridin-3-yl-amine derivatives as melanin-concentrating hormone receptor-1 antagonists

Derivatives of 1-(4-amino-phenyl)-pyrrolidin-3-yl-amine and 6-(3-amino-pyrrolidin-1-yl)-pyridin-3-yl-amine were identified as potent and functionally active MCH-R1 antagonists. One compound with Ki = 2.3 nM demonstrated good oral bioavailability (32%) and in vivo efficacy in rats.