Gary Tresadern

Discovery of 3-cyclopropylmethyl-7-(4-phenylpiperidin-1-yl)-8-trifluoromethyl[1,2,4]triazolo[4,3-a]pyridine (JNJ-42153605): a positive allosteric modulator of the metabotropic glutamate 2 receptor.

Advanced leads from a series of 1,2,4-triazolo[4,3-a]pyridines with mGlu2 receptor PAM activity are reported. By modification of the analogous imidazo[1,2-a]pyridine series, the newly reported leads have improved potency, in vitro ADMET, and hERG as well as good in vivo PK profile. The optimization of the series focused on improving metabolic stability while controlling lipophilicity by introducing small modifications to the scaffold substituents. Analysis of this series combined with our previously reported mGlu2 receptor PAMs showed how lipophilic ligand efficiency was improved during the course of the program. Among the best compounds, example 20 (JNJ-42153605) showed a central in vivo efficacy by inhibition of REM sleep state at a dose of 3 mg/kg po in the rat sleep-wake EEG paradigm, a phenomenon shown earlier to be mGlu2 mediated. In mice, compound 20 reversed PCP-induced hyperlocomotion with an ED₅₀ of 5.4 mg/kg sc, indicative of antipsychotic activity.

Molecular blueprint of allosteric binding sites in a homologue of the agonist-binding domain of the α7 nicotinic acetylcholine receptor

Significance In this study we take advantage of a recently described chimera of the α7 nicotinic acetylcholine receptor (nAChR) and acetylcholine binding protein (AChBP), termed α7-AChBP. To date, more than 70 crystal structures have been determined for AChBP in complex with ligands that occupy the orthosteric binding site. Here, we use an innovative screening strategy to discover molecular fragments that occupy allosteric binding sites. In combination with X-ray crystallography we determine a molecular blueprint of three different allosteric sites in α7-AChBP. Using electrophysiological recordings on the human α7 nAChR we demonstrate that each of the three sites is involved in allosteric modulation of the receptor. Our study contributes to understanding the sites of allosteric binding in ion channels. The α7 nicotinic acetylcholine receptor (nAChR) belongs to the family of pentameric ligand-gated ion channels and is involved in fast synaptic signaling. In this study, we take advantage of a recently identified chimera of the extracellular domain of the native α7 nicotinic acetylcholine receptor and acetylcholine binding protein, termed α7-AChBP. This chimeric receptor was used to conduct an innovative fragment-library screening in combination with X-ray crystallography to identify allosteric binding sites. One allosteric site is surface-exposed and is located near the N-terminal α-helix of the extracellular domain. Ligand binding at this site causes a conformational change of the α-helix as the fragment wedges between the α-helix and a loop homologous to the main immunogenic region of the muscle α1 subunit. A second site is located in the vestibule of the receptor, in a preexisting intrasubunit pocket opposite the agonist binding site and corresponds to a previously identified site involved in positive allosteric modulation of the bacterial homolog ELIC. A third site is located at a pocket right below the agonist binding site. Using electrophysiological recordings on the human α7 nAChR we demonstrate that the identified fragments, which bind at these sites, can modulate receptor activation. This work presents a structural framework for different allosteric binding sites in the α7 nAChR and paves the way for future development of novel allosteric modulators with therapeutic potential.

Imidazo[1,2-a]pyridines: Orally Active Positive Allosteric Modulators of the Metabotropic Glutamate 2 Receptor

Advanced leads of an imidazopyridine series of positive allosteric modulators of the metabotropic glutamate 2 (mGlu2) receptor are reported. The optimization of in vitro ADMET and in vivo pharmacokinetic properties led to the identification of 27o. With good potency and selectivity for the mGlu2 receptor, 27o affected sleep-wake architecture in rats after oral treatment, which we have previously shown to be indicative of mGlu2 receptor-mediated central activity.

Design and Synthesis of a Novel Series of Bicyclic Heterocycles As Potent γ-Secretase Modulators

The design and the synthesis of several chemical subclasses of imidazole containing γ-secretase modulators (GSMs) is described. Conformational restriction of pyridone 4 into bicyclic pyridone isosteres has led to compounds with high in vitro and in vivo potency. This has resulted in the identification of benzimidazole 44a as a GSM with low nanomolar potency in vitro. In mouse, rat, and dog, this compound displayed the typical γ-secretase modulatory profile by lowering Aβ42 and Aβ40 levels combined with an especially pronounced increase in Aβ38 and Aβ37 levels while leaving the total levels of amyloid peptides unchanged.

Product ion mobility as a promising tool for assignment of positional isomers of drug metabolites

Travelling wave ion mobility spectrometry - mass spectrometry (TWIMS-MS) was evaluated as a tool for structural identification of metabolites of small molecule drugs in cases where the exact position of the biotransformation could not be identified by conventional tandem mass spectrometry. Test sets of compounds containing biotransformations at aromatic positions were analyzed. These present a problem for traditional MS methods since an atomic level localization of the biotransformation cannot normally be determined from MS(n) spectra. In addition to ion mobility measurements of the intact metabolite ions, ion mobility measurements of product ions were also made and the results compared with calculated values. This approach reduces the complexity of the problem, making theoretical calculations easier and more predictable when a modeled collision cross section (CCS) is required. A good relative correspondence between theoretical and measured CCSs was obtained allowing the identification of the exact position of the biotransformation. It was also demonstrated that authentic standards with substructures identical to those in the unknown can be used to assign the exact position of the biotransformation. In this approach the identification was based on the comparison of the drift times or CCSs for product ions of the standard, with those of the same product ions in the unknown.

Rational design and synthesis of aminopiperazinones as β-secretase (BACE) inhibitors.

Aminopiperazinone inhibitors of BACE were identified by rational design. Structure based design guided idea prioritization and initial racemic hit 18a showed good activity. Modification in decoration and chiral separation resulted in the 40 nM inhibitor, (-)-37, which showed in vivo reduction of amyloid beta peptides. The crystal structure of 18a showed a binding mode driven by interaction with the catalytic aspartate dyad and distribution of the biaryl amide decoration towards S1 and S3 pockets.

Discovery of 1,5-disubstituted pyridones: a new class of positive allosteric modulators of the metabotropic glutamate 2 receptor.

A series of 1,5-disubstituted pyridones was identified as positive allosteric modulators (PAMs) of the metabotropic glutamate receptor 2 (mGluR2) via high throughput screening (HTS). Subsequent SAR exploration led to the identification of several compounds with improved in vitro activity. Lead compound 8 was further profiled and found to attenuate the increase in PCP induced locomotor activity in mice.

Discovery of 1-Butyl-3-chloro-4-(4-phenyl-1-piperidinyl)-(1H)-pyridone (JNJ-40411813): A Novel Positive Allosteric Modulator of the Metabotropic Glutamate 2 Receptor

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.

Discovery of 1,4-disubstituted 3-cyano-2-pyridones: a new class of positive allosteric modulators of the metabotropic glutamate 2 receptor.

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.

Extending kinome coverage by analysis of kinase inhibitor broad profiling data

The explored kinome was extended with broad profiling using the DiscoveRx and Millipore assay panels. The analysis of the profiling of 3368 selected inhibitors on 456 kinases in the DiscoveRx format delivered several insights. First, the coverage depended on the threshold of the selectivity parameter. Second, the relation between hit confirmation rates and inhibitor selectivity showed unexpectedly that higher selectivity can increase the likelihood of false positives. Third, comparing the coverage of a focused to that of a random library showed that the design based on a maximum number of scaffolds was superior to a limited number of scaffolds. Therefore, selective compounds can be used in target validation, enable the jumpstarting of new kinase drug discovery projects, and chart new biological space via phenotypic screening.