Stafford McLean

The substance P receptor antagonist CP-96,345 interacts with Ca2+ channels

The nonpeptide substance P receptor antagonist CP-96,345 was found to displace binding to Ca2+ channel binding sites labelled with either [3H]desmethoxyverapamil or [3H]diltiazem and to enhance [3H]nitrendipine binding. Unlike the substance P receptor antagonist activity of CP-96,345, these effects on Ca2+ channel binding sites were neither stereoselective nor species-dependent. It is concluded that CP-96,345 may act as an antagonist of L-type Ca2+ channels in addition to being a potent NK1 receptor (substance P) antagonist.

Preclinical pharmacology of the α4β2 nAChR partial agonist varenicline related to effects on reward, mood and cognition

The pharmacological properties and pharmacokinetic profile of the alpha4beta2 nicotinic acetylcholine receptor (nAChR) partial agonist varenicline provide an advantageous combination of free brain levels and functional potencies at the target receptor that for a large part explain its efficacy as a smoking cessation aid. Since alpha4beta2 and other nAChR subtypes play important roles in mediating central processes that control reward, mood, cognition and attention, there is interest in examining the effects of selective nAChR ligands such as varenicline in preclinical animal models that assess these behaviors. Here we describe results from studies on vareniclines effects in animal models of addiction, depression, cognition and attention and discuss these in the context of recently published preclinical and preliminary clinical studies that collected data on vareniclines effects on mood, cognition and alcohol abuse disorder. Taken together, the preclinical and the limited clinical data show beneficial effects of varenicline, but further clinical studies are needed to evaluate whether the preclinical effects observed in animal models are translatable to the clinic.

Respiratory syncytial virus upregulates expression of the substance P receptor in rat lungs

Respiratory syncytial virus (RSV) is a major respiratory pathogen in infants. The first goal of this study was to determine whether the infection following endotracheal inoculation of RSV in Fischer 344 rats results in increased inflammatory responses to substance P (SP) either released by capsaicin from sensory nerves or injected into the circulation. Five days after inoculation, the extravasation of Evans blue-labeled albumin after capsaicin or SP was significantly greater in RSV-infected airways than in pathogen-free controls. The peptide-degrading activity of the regulatory enzyme neutral endopeptidase was unaffected by RSV. However, SP(NK1) receptor mRNA levels increased fivefold in RSV-infected lungs, and the density of SP binding sites in the bronchial mucosa increased threefold. These data suggest that RSV makes the airways abnormally susceptible to the proinflammatory effects of SP by upregulating SP(NK1) receptor gene expression, thereby increasing the density of these receptors on target cells. This effect may contribute to the inflammatory reaction to the virus and could be a target for the therapy of RSV disease and its sequelae.Respiratory syncytial virus (RSV) is a major respiratory pathogen in infants. The first goal of this study was to determine whether the infection following endotracheal inoculation of RSV in Fischer 344 rats results in increased inflammatory responses to substance P (SP) either released by capsaicin from sensory nerves or injected into the circulation. Five days after inoculation, the extravasation of Evans blue-labeled albumin after capsaicin or SP was significantly greater in RSV-infected airways than in pathogen-free controls. The peptide-degrading activity of the regulatory enzyme neutral endopeptidase was unaffected by RSV. However, SP(NK(1)) receptor mRNA levels increased fivefold in RSV-infected lungs, and the density of SP binding sites in the bronchial mucosa increased threefold. These data suggest that RSV makes the airways abnormally susceptible to the proinflammatory effects of SP by upregulating SP(NK(1)) receptor gene expression, thereby increasing the density of these receptors on target cells. This effect may contribute to the inflammatory reaction to the virus and could be a target for the therapy of RSV disease and its sequelae.

Discovery of 4-(5-Methyloxazolo[4,5-b]pyridin-2-yl)-1,4-diazabicyclo[3.2.2]nonane (CP-810,123), a Novel α7 Nicotinic Acetylcholine Receptor Agonist for the Treatment of Cognitive Disorders in Schizophrenia: Synthesis, SAR Development, and in Vivo Efficacy in Cognition Models

A novel alpha 7 nAChR agonist, 4-(5-methyloxazolo[4,5-b]pyridin-2-yl)-1,4-diazabicyclo[3.2.2]nonane (24, CP-810,123), has been identified as a potential treatment for cognitive deficits associated with psychiatric or neurological conditions including schizophrenia and Alzheimers disease. Compound 24 is a potent and selective compound with excellent pharmaceutical properties. In rodent, the compound displays high oral bioavailability and excellent brain penetration affording high levels of receptor occupancy and in vivo efficacy in auditory sensory gating and novel object recognition. The structural diversity of this compound and its preclinical in vitro and in vivo package support the hypothesis that alpha 7 nAChR agonists may have potential as a pharmacotherapy for the treatment of cognitive deficits in schizophrenia.

Phosphodiesterase 9A regulates central cGMP and modulates responses to cholinergic and monoaminergic perturbation in vivo.

Cyclic nucleotides are critical regulators of synaptic plasticity and participate in requisite signaling cascades implicated across multiple neurotransmitter systems. Phosphodiesterase 9A (PDE9A) is a high-affinity, cGMP-specific enzyme widely expressed in the rodent central nervous system. In the current study, we observed neuronal staining with antibodies raised against PDE9A protein in human cortex, cerebellum, and subiculum. We have also developed several potent, selective, and brain-penetrant PDE9A inhibitors and used them to probe the function of PDE9A in vivo. Administration of these compounds to animals led to dose-dependent accumulation of cGMP in brain tissue and cerebrospinal fluid, producing a range of biological effects that implied functional significance for PDE9A-regulated cGMP in dopaminergic, cholinergic, and serotonergic neurotransmission and were consistent with the widespread distribution of PDE9A. In vivo effects of PDE9A inhibition included reversal of the respective disruptions of working memory by ketamine, episodic and spatial memory by scopolamine, and auditory gating by amphetamine, as well as potentiation of risperidone-induced improvements in sensorimotor gating and reversal of the stereotypic scratching response to the hallucinogenic 5-hydroxytryptamine 2A agonist mescaline. The results suggested a role for PDE9A in the regulation of monoaminergic circuitry associated with sensory processing and memory. Thus, PDE9A activity regulates neuronal cGMP signaling downstream of multiple neurotransmitter systems, and inhibition of PDE9A may provide therapeutic benefits in psychiatric and neurodegenerative diseases promoted by the dysfunction of these diverse neurotransmitter systems.

Synthesis and structure-activity relationships of CP-122,721, a second-generation NK-1 receptor antagonist.

The synthesis and SAR of benzylamine side chain analogs of the NK-1 receptor antagonist CP-99,994 are described. The 5-trifluoromethoxy analog, CP-122,721, shows superior in vivo blockade of NK-1 receptor mediated responses.

Pharmacological Characterization of 2-Methyl-N-((2′-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine (PF-04455242), a High-Affinity Antagonist Selective for κ-Opioid Receptors

2-Methyl-N-((2′-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine (PF-04455242) is a novel κ-opioid receptor (KOR) antagonist with high affinity for human (3 nM), rat (21 nM), and mouse (22 nM) KOR, a ∼20-fold reduced affinity for human μ-opioid receptors (MORs; Ki = 64 nM), and negligible affinity for δ-opioid receptors (Ki > 4 μM). PF-04455242 also showed selectivity for KORs in vivo. In rats, PF-04455242 blocked KOR and MOR agonist-induced analgesia with ID50 values of 1.5 and 9.8 mg/kg, respectively, and inhibited ex vivo [3H](2-(benzofuran-4-yl)-N-methyl-N-((5S,7R,8R)-7-(pyrrolidin-1-yl)-1-oxaspiro[4.5]decan-8-yl)acetamide ([3H]CI977) and [3H](2S)-2-[[2-[[(2R)-2-[[(2S)-2-amino-3-(4-hydroxyphenyl) propanoyl]amino]propanoyl]amino]acetyl]-methylamino]-N-(2-hydroxyethyl)-3-phenylpropanamide ([3H]DAMGO) binding to KOR and MOR receptors with ID50 values of 2.0 and 8.6 mg/kg, respectively. An in vivo binding assay was developed using (-)-4-[3H]methoxycarbonyl-2-[(1-pyrrolidinylmethyl]-1-[(3,4-dichlorophenyl)acetyl]-piperidine ([3H]PF-04767135), a tritiated version of the KOR positron emission tomography ligand (-)-4-[11C]methoxycarbonyl-2-[(1-pyrrolidinylmethyl]-1-[(3,4-dichlorophenyl)acetyl]-piperidine ([11C]GR103545) in which PF-04455242 had an ID50 of 5.2 mg/kg. PF-04455242 demonstrated antidepressant-like efficacy (mouse forced-swim test), attenuated the behavioral effects of stress (mouse social defeat stress assay), and showed therapeutic potential in treating reinstatement of extinguished cocaine-seeking behavior (mouse conditioned place preference). KOR agonist-induced plasma prolactin was investigated as a translatable mechanism biomarker. Spiradoline (0.32 mg/kg) significantly increased rat plasma prolactin levels from 1.9 ± 0.4 to 41.9 ± 4.9 ng/ml. PF-04455242 dose-dependently reduced the elevation of spiradoline-induced plasma prolactin with an ID50 of 2.3 ± 0.1 mg/kg, which aligned well with the ED50 values obtained from the rat in vivo binding and efficacy assays. These data provide further evidence that KOR antagonists have potential for the treatment of depression and addiction disorders.

A water soluble benzazepine cholecystokinin-B receptor antagonist

Abstract A series of 5-substituted-3-ureidobenzazepin-2-ones bearing ioizable functionality was synthesized as potential cholecystokinin-B (CCK-B) receptor antagonists. SAR of this series of compounds demonstrated the optimal combination of a carboxylic acid and 5-cyclohexyl group, providing the high affinity (CCK-B IC 50 = 0.10 nM), water soluble CCK-B antagonist 2 .

Agonist and Antagonist Receptor Binding

Substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) are members of the tachykinin family of peptides that share the carboxy terminal sequence Phe-X-Gly-Leu-Met-NH2. These mammalian tachykinins elicit their effects through three different receptors known as NK1NK2and NK3. Pharmacological and biochemical studies suggest that substance P is the preferred endogenous ligand for the NKI receptor, whereas neurokinin A and neurokinin B have highest affinity for NK2 and NK3 receptors, respectively (Buck and Burcher, 1986; Maggio, 1988; Quirion and Dam, 1988; Guard and Watson, 1991). The characterization of the NKINK2and NK3 receptors as distinct sites was confirmed with the cloning and sequencing of separate cDNAs encoding each of the receptors (Masu et al., 1987; Sasai and Nakanishi, 1989; Yokota et al., 1989; Gerard et al., 1990; Hershey and Krause, 1990; Shigemoto et al., 1990; Hershey et al., 1991). The deduced amino acid sequence and hydropathy analysis suggest that all three of the tachykinin receptors contain seven transmembrane spanning domains and sequence similarity with other members of the superfamily of G-proteincoupled receptors. Maximal sequence homology among NKINK2and NK3 receptors is found in the putative core transmembrane domains, whereas homology is lowest at the amino and carboxy terminal ends (Nakanishi, 1991).

Articulating a pharmacophore driven synthetic strategy: Discovery of a potent substance P antagonist

Abstract We now reveal (2β, 3β, 3αβ, 6αβ)-(±)-octahydro-N-[(2-methoxyphenyl)methyl]-2-phenylcyclopenta[b]pyrrol-3-amine (2) as potent SP antagonist; the discovery of 2 resulted from the pharmacophore driven synthetic strategy. Furthermore we find that for 1 and 2 the spatial disposition of the C-2 phenyl group and the two nitrogen atoms as indicated by molecular modeling are similar. The discovery and synthesis of 2 as a potent substance P antagonist is described; the synthesis was accomplished via a pharmacophore-driven synthetic strategy.