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We previously reported the discovery of 4-aryl-substituted pyridones with mGlu2 PAM activity starting from the HTS hit 5. In this article, we describe a different exploration from 5 that led to the discovery of a novel subseries of phenylpiperidine-substituted pyridones. The optimization strategy involved the introduction of different spacers between the pyridone core and the phenyl ring of 5. The fine tuning of metabolism and hERG followed by differentiation of advanced leads that were identified on the basis of PK profiles and in vivo potency converged on lead compound 36 (JNJ-40411813). Full in vitro and in vivo profiles indicate that 36 displayed an optimal interplay between potency, selectivity, favorable ADMET/PK and cardiovascular safety profile, and central EEG activity. Compound 36 has been investigated in the clinic for schizophrenia and anxious depression disorders.

ADX71943 is a potent and selective GABA(b) receptor positive allosteric modulator (PAM) which exhibits poor aqueous solubility at all physiologically relevant pHs. The aim of this study was to identify an adequate formulation to improve the solubility of ADX71943 to achieve a sufficiently high plasma exposure after oral administration to support the toxicology program. Considering the overall physicochemical properties and the low solubility of ADX71943 in a variety of solvents, solid dispersion, and particle size reduction have been successfully chosen as potential strategies to improve its oral bioavailability. Both technologies have proven useful in improving the in vitro dissolution profile and as a result of the solubility enhancement, higher bioavailability was obtained in vivo. As the solid dispersion gave better bioavailability (30-fold compared with the neat active pharmaceutical ingredient (API)), this formulation was selected for the toxicology study. Changing the crystalline form of ADX71943 into amorphous state by preparing a solid dispersion has greatly improved its oral bioavailability and has allowed achieving the required plasma concentration needed in toxicology studies.

The discovery and characterization of compound 48, a selective and in vivo active mGlu2 receptor positive allosteric modulator (PAM), are described. A key to the discovery was the rational exploration of the initial HTS hit 13 guided by an overlay model built with reported mGlu2 receptor PAM chemotypes. The initial weak in vitro activity of the hit 13 was quickly improved, although compounds still had suboptimal druglike properties. Subsequent modulation of the physicochemical properties resulted in compounds having a more balanced profile, combining good potency and in vivo pharmacokinetic properties. Final refinement by addressing cardiovascular safety liabilities led to the discovery of compound 48. Besides good potency, selectivity, and ADME properties, compound 48 displayed robust in vivo activity in a sleep-wake electroencephalogram (sw-EEG) assay consistent with mGlu2 receptor activation, in accordance with previous work from our laboratories.

Allosteric modulators of metabotropic glutamate receptors (mGluR) subtypes 1-8 have been shown to offer a valid way to develop small molecule non aminoacid-like therapeutics that can be administered orally and that readily cross the blood-brain barrier. Allosteric modulators of glutamatergic receptors and in particular mGluR5 have emerged as a novel and highly desirable class of compounds for the treatment of central nervous system (CNS) disorders and peripheral disorders. This article provides medicinal chemistry highlights around the chemical classes of potent and highly selective mGluR5 negative allosteric modulators (NAMs) and their therapeutic potential. In addition, it describes the medicinal chemistry approach from the discovery to the clinical candidate selection of a new series of heteroaryl-butynylpyridines targeting mGluR5. The multiparametric optimization of the initial starting point which ended in the selection of potential clinical candidates combining the best pharmacophoric features is presented. The pharmacological properties are reported and support the interest of these agents for new therapeutic approaches. Furthermore, a summary of the diverse mGluR5 Positron Emission Tomography (PET) radioligands is reported.

A series of N-propyl-5-substituted isoquinolones was identified as positive allosteric modulators (PAM) of metabotropic glutamate receptor 2 (mGluR2) via high-throughput screening (HTS). The subsequent synthesis and preliminary SAR exploration that led to the identification of compound 20 are described.

During a program directed at selective NK(1) receptor antagonists, we serendipitously discovered an NK(1) receptor ligand with additional affinity for the NK(3) receptor. Recognising an opportunity for a drug discovery program aiming for dual NK(1)/NK(3) receptor antagonists, we prepared a series of analogues from a novel, versatile building block. From this series emerged compounds with high and balanced affinities for the NK(1) and the NK(3) receptors. Typical representatives of this series were active in the gerbil foot tapping assay after oral administration.

The inhibition of human cytochrome P450s (CYPs) is one of the most common mechanisms which can lead to drug-drug interactions. The inhibition of CYPs can be reversible (competitive or non-competitive) or irreversible. Irreversible inhibition usually derives from activation of a drug by CYPs into a reactive metabolite, which tightly binds to the enzyme active site, leading to a long lasting inactivation. This process is called "mechanism based inhibition" or "suicide inhibition". The irreversible inactivation usually implies the formation of a covalent bond between the metabolite and the enzyme, which can lead to hapten formation and can in some cases trigger an auto immune-response. For these reasons it is of utmost importance to study the mechanism of the CYP inhibition of new potential drugs as early as possible during the drug discovery process. The literature on CYPs is vast and covers numerous aspects of their biology and biochemistry, however to our knowledge there is no general and systematic review focusing on mechanism-based inhibitors; we have reviewed the literature and compiled all the available data on chemical entities, which are known to be CYP suicide inhibitors. Each compound is reported together with its chemical structure, the CYP isoform and the parameters describing the inactivation. Literature references are reported together with their PMID (PubMed ID number) to allow a fast retrieval of the papers. This review offers a quick reference to help predict liabilities of new chemical entities without carrying out extensive in vitro work, and will hopefully help in designing safer drugs.

A series of potent non-acetylinic negative allosteric modulators of the metabotropic glutamate receptor 5 (mGlu5 NAMs) was developed starting from HTS screening hit 1. Potency was improved via iterative SAR, and physicochemical properties were optimized to deliver orally bioavailable compounds acceptable for in vivo testing. A lead molecule from the series demonstrated dose-dependent activity in the second phase of the rat formalin test from 30 mg/kg, and a preliminary PK/PD relationship was established.

A series of N-propyl-8-chloro-6-substituted isoquinolones was identified as positive allosteric modulators of metabotropic glutamate receptor 2 (mGluR2 PAM) via high throughput screening (HTS). The subsequent synthesis and initial SAR exploration that led to the identification of compound 28 is described.

The discovery of a novel, achiral pyridine class of potent and orally active neurokinin-1 (NK 1 ) receptor antagonists is described. The evaluation of this class is briefly outlined, leading to the identification of netupitant 21 and befetupitant 29 , two new proprietary chemical entities with high affinity and excellent CNS penetration.

A recently identified DPP-IV inhibitor (1) was found to induce phospholipidosis and to inhibit CYP3A4. A small series of less lipophilic and less amphiphilic analogues was synthesized in an effort to overcome these issues. One compound from this series was equipotent to 1, did not induce phospholipidosis and showed a reduced CYP3A4 inhibition.

The ATP-dependent drug efflux pump P-glycoprotein (P-gp) affects the absorption and disposition of many compounds. P-gp may also play role in clinically significant drug-drug interactions. Therefore, it is important to find potential substrates or inhibitors of P-gp early in the drug discovery process. To identify compounds that interact with this transporter, several P-gp assays were validated and compared by testing a set of 28 reference compounds, including inhibitors of cytochrome P450 3A4 (CYP3A4). The assays included in silico predictions, inhibition assays (based on cellular uptake of rhodamine-123 or calcein AM), and functional assays (ATPase activity assay and transcellular transport assay, the latter for a subset of compounds). In addition, species differences were studied in an indirect fluorescence indicator screening assay and test systems expressing porcine, mouse, or human P-gp. Our results suggest that several P-gp assays should be used in combination to classify compounds as substrates or inhibitors of P-gp. Recommendations are given on screening strategies which can be applied to different phases of the drug discovery and development process.

A small series of aryl pyridyl sulfones has been prepared and investigated for its 5-HT(6) receptor binding properties. Thereof, pyrrolidinyl derivative 11 proved to be a very potent (pK(i) 9) and selective 5-HT(6) receptor antagonist. By means of in vivo microdialysis in the frontal cortex and a passive avoidance paradigm, where 11 reversed a scopolamine induced retention deficit, a functional correlation between 5-HT(6) receptors and cholinergic neurotransmission could be shown, supporting the therapeutic potential of 5-HT(6) receptors in the treatment of cognitive deficits.

Novel hexahydrospiro[piperidine-4,1'-pyrrolo[3,4-c]pyrroles that act as potent and selective orphanin FQ/nociceptin (N/OFQ) receptor (NOP) agonists were identified. The best compound, (+)-5a, potently inhibited 3H-N/OFQ binding to the NOP receptor (K(i) = 0.49 nM) but was1000-fold less potent in binding to MOP, KOP, and DOP opiate receptors. Further, (+)-5a potently stimulated GTP gamma S binding to NOP membranes (EC50 = 65 nM) and inhibited forskolin-mediated cAMP accumulation in NOP-expressing cells (EC50 = 9.1 nM) with a potency comparable to that of the natural peptide agonist N/OFQ. These results indicate that (+)-5a is a highly selective and potent small-molecule full agonist of the NOP receptor.