Cindy Wintmolders

Characterization of an orphan G protein-coupled receptor localized in the dorsal root ganglia reveals adenine as a signaling molecule

The cloning of novel G protein-coupled receptors and the search for their natural ligands, a process called reverse pharmacology, is an excellent opportunity to discover novel hormones and neurotransmitters. Based on a degenerate primer approach we have cloned a G protein-coupled receptor whose mRNA expression profile indicates highest expression in the dorsal root ganglia, specifically in the subset of small neurons, suggesting a role in nociception. In addition, moderate expression was found in lung, hypothalamus, peripheral blood leukocytes, and ovaries. Guided by a receptor-activation bioassay, we identified adenine as the endogenous ligand, which activated the receptor potently and with high structural stringency. Therefore, we propose to name this receptor as the adenine receptor. Hormonal functions have already been demonstrated for adenine derivatives like 6-benzylaminopurine in plants and 1-methyladenine in lower animals. Here, we demonstrate that adenine functions as a signaling molecule in mammals. This finding adds a third family besides P1 and P2 receptors to the class of purinergic receptors.

Detailed distribution of Neurokinin 3 receptors in the rat, guinea pig and gerbil brain: a comparative autoradiographic study

The neurokinin 3 (NK3) receptor is predominantly expressed in the central nervous system (CNS). Species differences in neurokinin 3 (NK3) receptor pharmacology have led to the preferential use of guinea pigs and gerbils in the characterization of non-peptide NK3 antagonists. Little is known about the central localization of NK3 receptors in the CNS of these species. To study this, [(3)H]senktide and [(3)H]SR 142801 were used in autoradiography experiments to visualize the NK3 receptors in the guinea pig and gerbil brain and compared to with the distribution of [(3)H]senktide binding sites in the rat brain. In the three species, the NK3 receptor was similarly distributed within the cerebral cortex, the zona incerta, the medial habenula, the amygdaloid complex, the superior colliculus and the interpeduncular nucleus. Outside of these structures, our study has revealed that each species displayed a specific distribution pattern of central NK3 receptors. The rat was the only species where NK3 receptors could be visualized in the striatum, the supraoptic nucleus and the paraventricular nucleus of the hypothalamus. The guinea pig differed mainly from the two other species by the absence of detectable binding sites in the substantia nigra pars compacta and the ventral tegmental area. A specific localization of NK3 receptors in the anterodorsal and anteroventral thalamic nuclei characterized the gerbil. This last species is also unique by in the higher level of NK3 receptors in the dorsal and median raphe nuclei. All these differences suggest that the NK3 receptor mediates different functions in different species.

Pharmacological Characterization of JNJ-40068782, a New Potent, Selective, and Systemically Active Positive Allosteric Modulator of the mGlu2 Receptor and Its Radioligand [3H]JNJ-40068782

Modulation of the metabotropic glutamate type 2 (mGlu2) receptor is considered a promising target for the treatment of central nervous system diseases such as schizophrenia. Here, we describe the pharmacological properties of the novel mGlu2 receptor positive allosteric modulator (PAM) 3-cyano-1-cyclopropylmethyl-4-(4-phenyl-piperidin-1-yl)-pyridine-2(1H)-one (JNJ-40068782) and its radioligand [3H]JNJ-40068782. In guanosine 5′-O-(3-[35S]thio)triphosphate binding, JNJ-40068782 produced a leftward and upward shift in the glutamate concentration-effect curve at human recombinant mGlu2 receptors. The EC50 of JNJ-40068782 for potentiation of an EC20-equivalent concentration of glutamate was 143 nM. Although JNJ-40068782 did not affect binding of the orthosteric antagonist [3H]2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid (LY-341495), it did potentiate the binding of the agonist [3H](2S,2′R,3′R)-2-(2′,3′-dicarboxylcyclopropyl)glycine (DCG-IV), demonstrating that it can allosterically affect binding at the agonist recognition site. The binding of [3H]JNJ-40068782 to human recombinant mGlu2 receptors in Chinese hamster ovary cells and rat brain receptors was saturable with a KD of ∼10 nM. In rat brain, the anatomic distribution of [3H]JNJ-40068782 was consistent with mGlu2 expression previously described and was most abundant in cortex and hippocampus. The ability of structurally unrelated PAMs to displace [3H]JNJ-40068782 suggests that PAMs may bind to common determinants within the same site. It is noteworthy that agonists also increased the binding affinity of [3H]JNJ-40068782. JNJ-40068782 influenced rat sleep-wake organization by decreasing rapid eye movement sleep with a lowest active dose of 3 mg/kg PO. In mice, JNJ-40068782 reversed phencyclidine-induced hyperlocomotion with an ED50 of 5.7 mg/kg s.c. Collectively, the present data demonstrate that JNJ-40068782 has utility in investigating the potential of mGlu2 modulation for the treatment of diseases characterized by disturbed glutamatergic signaling and highlight the value of [3H]JNJ-40068782 in exploring allosteric binding.

Patterns of brain glucose metabolism induced by phosphodiesterase-10A inhibitors in the mouse: a potential translational biomarker

Phosphodiesterase 10A (PDE10A) inhibitors have recently been proposed as a new therapy for schizophrenia. The aim of this study was to enhance our understanding of the role of PDE10A inhibitors and potentially identify a clinically useful mechanistic/functional biomarker by using 2-deoxyglucose (2-DG) autoradiography. PDE10A inhibitors papaverine (10 and 40 mg/kg), 6,7-dimethoxy-4-[(3R)-3-(2-quinoxalinyloxy)-1-pyrrolidinyl]quinazoline (PQ-10), (0.16–10 mg/kg), and 2-[{4-(1-methyl-4-pyridin-4-yl-1H-pyrazol-3-yl)phenoxy}methyl]quinoline (MP-10) (0.16–40 mg/kg) induced region-specific hypermetabolism in the globus pallidus and lateral habenula of C57BL/6 mice. Studies with MP-10 revealed a dose-dependent relative increase in globus pallidus activation, whereas a bell-shaped curve was observed for the lateral habenula. Although the relative increase in 2-DG uptake in the lateral habenula was also characteristic of the D2 antagonist haloperidol (0.01–0.63 mg/kg), relative 2-DG changes were absent in the globus pallidus. This observation probably is explained by the interaction of PDE10A inhibitors with the D1 direct pathway as suggested by experiments in combination with the D1 agonist (±)-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF-82958) (0.16 mg/kg). The absence of an effect of MP-10 (2.5 mg/kg) on relative glucose metabolism in the globus pallidus and lateral habenula of PDE10A knockout mice confirmed the specificity of the signal induced by PDE10A inhibitors. These studies substantiate the regulatory role of PDE10A in the basal ganglia circuit and as such support the potential of PDE10A inhibitors for treating psychiatric disorders. Moreover, we could differentiate PDE10A inhibitors from haloperidol based on specific patterns of hypermetabolism probably caused by its combined action at both direct and indirect dopaminergic pathways. Finally, these specific changes in brain glucose metabolism may act as a translational biomarker for target engagement in future clinical studies.

Comparison of the ex vivo receptor occupancy profile of ketamine to several NMDA receptor antagonists in mouse hippocampus.

NMDA receptor antagonists, particularly these targeting the GluN2B subunit are of therapeutic interest for the treatment of severe mood disorders. The receptor occupancy profiles of several NMDA receptor antagonists (30 mg/kg, s.c.) were compared in mouse hippocampus by ex vivo autoradiography using [(3)H]MK-801, a non-selective NMDA channel blocker, and [(3)H]ifenprodil a selective GluN2B antagonist. Subcutaneous administration of ketamine ((RS)-2-(2-Chlorophenyl)-2-(methylamino)cyclohexanone) and memantine (3,5-dimethyladamantan-1-amine) inhibited [(3)H]MK-801 but not [(3)H]ifenprodil binding in mouse hippocampus. Ketamine reached maximal occupancy of [(3)H]MK-801 binding sites after 15 min and rapidly cleared from the brain with no significant level of occupancy measured at the 1h time point. Memantine significantly occupied [(3)H]MK-801 binding sites throughout the 6h time course. The selective GluN2B antagonist CP101,606 ((1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol) and Ro 25-6981 ((αR,βS)-α-(4-Hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidinepropanol maleate) inhibited [(3)H]ifenprodil but not [(3)H]MK-801 binding and significant levels of occupancy (above 50%) were measured throughout the 6h time course. These data highlight the unique quick pulse target engagement profile of ketamine compared to other NMDA receptor antagonists.

Systemic immune‐checkpoint blockade with anti‐PD1 antibodies does not alter cerebral amyloid‐β burden in several amyloid transgenic mouse models

Chronic inflammation represents a central component in the pathogenesis of Alzheimers disease (AD). Recent work suggests that breaking immune tolerance by Programmed cell Death‐1 (PD1) checkpoint inhibition produces an IFN‐γ‐dependent systemic immune response, with infiltration of the brain by peripheral myeloid cells and neuropathological as well as functional improvements even in mice with advanced amyloid pathology (Baruch et al., ( ): Nature Medicine, 22:135–137). Immune checkpoint inhibition was therefore suggested as potential treatment for neurodegenerative disorders when activation of the immune system is appropriate. Because a xenogeneic rat antibody (mAb) was used in the study, whether the effect was specific to PD1 target engagement was uncertain. In the present study we examined whether PD1 immunotherapy can lower amyloid‐β pathology in a range of different amyloid transgenic models performed at three pharmaceutical companies with the exact same anti‐PD1 isotype and two mouse chimeric variants. Although PD1 immunotherapy stimulated systemic activation of the peripheral immune system, monocyte‐derived macrophage infiltration into the brain was not detected, and progression of brain amyloid pathology was not altered. Similar negative results of the effect of PD1 immunotherapy on amyloid brain pathology were obtained in two additional models in two separate institutions. These results show that inhibition of PD1 checkpoint signaling by itself is not sufficient to reduce amyloid pathology and that additional factors might have contributed to previously published results (Baruch et al., ( ): Nature Medicine, 22:135–137). Until such factors are elucidated, animal model data do not support further evaluation of PD1 checkpoint inhibition as a therapeutic modality for Alzheimers disease.

Discovery of N-(Pyridin-4-yl)-1,5-naphthyridin-2-amines as Potential Tau Pathology PET Tracers for Alzheimer’s Disease

A mini-HTS on 4000 compounds selected using 2D fragment-based similarity and 3D pharmacophoric and shape similarity to known selective tau aggregate binders identified N-(6-methylpyridin-2-yl)quinolin-2-amine 10 as a novel potent binder to human AD aggregated tau with modest selectivity versus aggregated β-amyloid (Aβ). Initial medicinal chemistry efforts identified key elements for potency and selectivity, as well as suitable positions for radiofluorination, leading to a first generation of fluoroalkyl-substituted quinoline tau binding ligands with suboptimal physicochemical properties. Further optimization toward a more optimal pharmacokinetic profile led to the discovery of 1,5-naphthyridine 75, a potent and selective tau aggregate binder with potential as a tau PET tracer.

A systematic evaluation of the preclinical pharmacokinetic/pharmacodynamic relationship of Alzheimer's disease gold standard drugs in the rat: An in vitro, ex vivo and in vivo comparison

P4-301 A SYSTEMATIC EVALUATION OF THE PRECLINICAL PHARMACOKINETIC/ PHARMACODYNAMIC RELATIONSHIP OF ALZHEIMER’S DISEASE GOLD STANDARD DRUGS INTHERAT: AN IN VITRO,EXVIVOAND IN VIVO COMPARISON Caitlin Jones, Ineke Fonteyn, Nikhil Garewal, Cindy Wintmolders, Massimo Cella, Koen Wuyts, Roland Willems, Hilde Duytschaever, Emily Calderbanck, Luc Ver Donck, Xavier Langlois, Jill Richardson, Esther Schenker, John Atack, Janssen R&D, Beerse, Belgium; Janssen Pharmaceutica, Beerse, Belgium; R&D GlaxoSmithKline, Middlesex, United Kingdom; GlaxoSmithKline R&D China Group, Stevenage, United Kingdom; Institut de Recherches Servier, Croissy s/Seine, France; Translational Drug Discovery Group, Brighton, United Kingdom. Contact e-mail: cjones34@its.jnj.com