Luc Peeters

Characterization of 2-[[4-Fluoro-3-(trifluoromethyl)phenyl]amino]-4-(4-pyridinyl)-5-thiazolemethanol (JNJ-1930942), a Novel Positive Allosteric Modulator of the α7 Nicotinic Acetylcholine Receptor

The α7 nicotinic acetylcholine receptor (nAChR) is a potential therapeutic target for the treatment of cognitive deficits associated with schizophrenia, Alzheimers disease, Parkinsons disease, and attention-deficit/hyperactivity disorder. Activation of α7 nAChRs improved sensory gating and cognitive function in animal models and in early clinical trials. Here we describe the novel highly selective α7 nAChR positive allosteric modulator, 2-[[4-fluoro-3-(trifluoromethyl)phenyl]amino]-4-(4-pyridinyl)-5-thiazolemethanol (JNJ-1930942). This compound enhances the choline-evoked rise in intracellular Ca2+ levels in the GH4C1 cell line expressing the cloned human α7 nAChR. JNJ-1930942 does not act on α4β2, α3β4 nAChRs or on the related 5-HT3A channel. Electrophysiological assessment in the GH4C1 cell line shows that JNJ-1930942 increases the peak and net charge response to choline, acetylcholine, and N-[(3R)-1-azabicyclo[2.2.2]oct-3-yl]-4-chlorobenzamide (PNU-282987). The potentiation is obtained mainly by affecting the receptor desensitization characteristics, leaving activation and deactivation kinetics as well as recovery from desensitization relatively unchanged. Choline efficacy is increased over its full concentration response range, and choline potency is increased more than 10-fold. The potentiating effect is α7 channel-dependent, because it is blocked by the α7 antagonist methyllycaconitine. Moreover, in hippocampal slices, JNJ-1930942 enhances neurotransmission at hippocampal dentate gyrus synapses and facilitates the induction of long-term potentiation of electrically evoked synaptic responses in the dentate gyrus. In vivo, JNJ-1930942 reverses a genetically based auditory gating deficit in DBA/2 mice. JNJ-1930942 will be a useful tool to study the therapeutic potential of α7 nAChR potentiation in central nervous system disorders in which a deficit in α7 nAChR neurotransmission is hypothesized to be involved.

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.

Pharmacology of JNJ-37822681, a Specific and Fast-Dissociating D2 Antagonist for the Treatment of Schizophrenia.

All marketed antipsychotics act by blocking dopamine D2 receptors. Fast dissociation from D2 receptors may be one of the elements contributing to the lower incidence of extrapyramidal symptoms (EPS) exhibited by newer antipsychotics. Therefore, we screened for specific D2 receptor blockers with a fast rate of dissociation. Radioligand binding experiments identified N- [1-(3,4-difluorobenzyl)piperidin-4-yl]-6-(trifluoromethyl)pyridazin-3-amine (JNJ-37822681) as a fast-dissociating D2 ligand. Its D2 receptor specificity was high compared with atypical antipsychotics, with little activity at receptors associated with unwanted effects [α1, α2, H1, muscarinic, and 5-hydroxytryptamine (5-HT) type 2C] and for receptors that may interfere with the effects of D2 antagonism (D1, D3, and 5-HT2A). JNJ-37822681 occupied D2 receptors in rat brain at relatively low doses (ED50 0.39 mg/kg) and was effective in animal models of psychosis (e.g., inhibition of apomorphine-induced stereotypy or d-amphetamine/phencyclidine-induced hyperlocomotion). Prolactin levels increased from an ED50 (0.17 mg/kg, peripheral D2 receptors) close to the ED50 required for apomorphine antagonism (0.19 mg/kg, central D2 receptors), suggesting excellent brain disposition and minimal prolactin release at therapeutic doses. JNJ-37822681 induced catalepsy and inhibited avoidance behavior, but with a specificity margin relative to apomorphine antagonism that was larger than that obtained for haloperidol and similar to that obtained for olanzapine. This larger specificity margin (compared with haloperidol) may reflect lower EPS liability and less behavioral suppression after JNJ-37822681. JNJ-37822681 is a novel, potent, specific, centrally active, fast-dissociating D2 antagonist with optimal brain disposition, and it is the first compound that allows the evaluation of the potential value of fast D2 antagonism for the treatment of schizophrenia and bipolar disorder.

Discovery of 8-Trifluoromethyl-3-cyclopropylmethyl-7-[(4-(2,4-difluorophenyl)-1-piperazinyl)methyl]-1,2,4-triazolo[4,3-a]pyridine (JNJ-46356479), a Selective and Orally Bioavailable mGlu2 Receptor Positive Allosteric Modulator (PAM)

Positive allosteric modulators of the metabotropic glutamate 2 receptor have generated great interest in the past decade. There is mounting evidence of their potential as therapeutic agents in the treatment of multiple central nervous system disorders. We have previously reported substantial efforts leading to potent and selective mGlu2 PAMs. However, finding compounds with the optimal combination of in vitro potency and good druglike properties has remained elusive, in part because of the hydrophobic nature of the allosteric binding site. Herein, we report on the lead optimization process to overcome the poor solubility inherent to the advanced lead 6. Initial prototypes already showed significant improvements in solubility while retaining good functional activity but displayed new liabilities associated with metabolism and hERG inhibition. Subsequent subtle modifications efficiently addressed those issues leading to the identification of compound 27 (JNJ-46356479). This new lead represents a more balanced profile that offers a significant improvement on the druglike attributes compared to previously reported leads.

Neurotoxic action of veratridine in rat brain neuronal cultures: mechanism of neuroprotection by Ca++-antagonists non-selective for slow Ca++-channels

The effect of various Ca++ antagonists and local anesthetics on neuronal cell degeneration induced by veratridine was studied in primary rat brain neuronal cultures. Cell death was quantified by measuring lactate dehydrogenase (LDH) released in the culture medium. The neuronal cell degeneration was Ca+(+)-dependent because, in the absence of extracellular Ca++, 16 hr of exposure to 30 microM veratridine failed to produce release of LDH. Ca++ antagonists, nonselective for slow Ca++ channels (flunarizine, cinnarizine, lidoflazine, prenylamine and bepridil) inhibited veratridine-induced release of LDH with IC50 values between 0.11 and 0.47 microM. Ca++ antagonists selective for slow Ca++ channels were less potent and inhibited veratridine-induced release of LDH at concentrations in the following order of potency: nicardipine greater than gallopamil and verapamil greater than niludipine greater than nitrendipine greater than nifedipine greater than nimodipine greater than diltiazem. Tested local anesthetics were incomplete inhibitors of veratridine-induced release of LDH. A good correlation was found between the potency of the drugs to inhibit released LDH induced by 30 microM veratridine in neuronal cultures and their binding affinity for the batrachotoxin binding site of Na+ channels in rat cortex synaptosomal preparation. It is concluded that protection against veratridine-induced neurotoxicity can be mediated by blocking a veratridine-sensitive Na+ channel. It is a property of certain nonselective Ca++ antagonists. There is apparently no direct relationship with Ca++ antagonistic activity. The effect is unrelated to local anesthetic activity.

Covalent Allosteric Probe for the Metabotropic Glutamate Receptor 2: Design, Synthesis, and Pharmacological Characterization

Covalent labeling of G protein-coupled receptors (GPCRs) by small molecules is a powerful approach to understand binding modes, mechanism of action, pharmacology, and even facilitate structure elucidation. We report the first covalent positive allosteric modulator (PAM) for a class C GPCR, the mGlu2 receptor. Three putatively covalent mGlu2 PAMs were designed and synthesized. Pharmacological characterization identified 2 to bind the receptor covalently. Computational modeling combined with receptor mutagenesis revealed T7917.29×30 as the likely position of covalent interaction. We show how this covalent ligand can be used to characterize the PAM binding mode and that it is a valuable tool compound in studying receptor function and binding kinetics. Our findings advance the understanding of the mGlu2 PAM interaction and suggest that 2 is a valuable probe for further structural and chemical biology approaches.