Dianne K. Bryce

Negative Allosteric Modulation of the mGluR5 Receptor Reduces Repetitive Behaviors and Rescues Social Deficits in Mouse Models of Autism

Autism-like behaviors in mice were reversed by a negative modulator of a metabotropic glutamate receptor, suggesting a treatment for symptoms of autism spectrum disorders. Treatment of Autism Symptoms in Mice When they are 2 to 5 years old, children with autism start to show unusual social interactions and impaired communication. They may fail to develop relationships with their peers and be unable to interpret nuances of speech and body language. Most show repetitive motor behaviors and restricted interests and can have associated seizures, anxiety, or intellectual impairment. A large number of genes can put people at risk for this disorder, each in a small number of cases, and these genes point to connections between neurons as a vulnerable point in autism. Now, Silverman and colleagues have used two inbred strains of mice that display well-replicated behavioral abnormalities relevant to the diagnostic symptoms of autism and shown that some of these symptoms can be improved with a drug directed at a central glutamate receptor of the brain, mGluR5. The authors used two inbred strains of mice that display robust behaviors relevant to the diagnostic symptoms of autism. BTBR mice show deficits in many types of social interactions and high levels of repetitive self-grooming. C58 repetitively jumps. They used GRN-529, a compound developed by Pfizer that reduces the actions of glutamate, the main excitatory neurotransmitter in the brain. Other mGluR antagonists are showing promise in clinical trials for people with the fragile X mutation, who have both intellectual impairments and autism, so the authors reasoned that an mGluR5 compound might help autistic symptoms. GRN-529 reduced both the repetitive self-grooming in BTBR and the repetitive jumping in C58. Most intriguingly, GRN-529 also improved social behaviors in BTBR in two assays, one for social approach to an unfamiliar mouse and one for social interactions between freely moving pairs of mice. A particular strength of this study is that the authors replicated these beneficial actions of the mGluR5 compound in several separate groups of mice, in two laboratories. Although the path from target identification to effective human treatment is a long and winding road, the discovery of therapeutic efficacy for an mGluR5 negative allosteric modulator in both the repetitive and the social domains in two distinct mouse models is a promising beginning. This single biological target may offer a useful entry point to develop a pharmacological therapy that alleviates many symptoms of autism spectrum disorders. Neurodevelopmental disorders such as autism and fragile X syndrome were long thought to be medically untreatable, on the assumption that brain dysfunctions were immutably hardwired before diagnosis. Recent revelations that many cases of autism are caused by mutations in genes that control the ongoing formation and maturation of synapses have challenged this dogma. Antagonists of metabotropic glutamate receptor subtype 5 (mGluR5), which modulate excitatory neurotransmission, are in clinical trials for fragile X syndrome, a major genetic cause of intellectual disabilities. About 30% of patients with fragile X syndrome meet the diagnostic criteria for autism. Reasoning by analogy, we considered the mGluR5 receptor as a potential target for intervention in autism. We used BTBR T+tf/J (BTBR) mice, an established model with robust behavioral phenotypes relevant to the three diagnostic behavioral symptoms of autism—unusual social interactions, impaired communication, and repetitive behaviors—to probe the efficacy of a selective negative allosteric modulator of the mGluR5 receptor, GRN-529. GRN-529 reduced repetitive behaviors in three cohorts of BTBR mice at doses that did not induce sedation in control assays of open field locomotion. In addition, the same nonsedating doses reduced the spontaneous stereotyped jumping that characterizes a second inbred strain of mice, C58/J. Further, GRN-529 partially reversed the striking lack of sociability in BTBR mice on some parameters of social approach and reciprocal social interactions. These findings raise the possibility that a single targeted pharmacological intervention may alleviate multiple diagnostic behavioral symptoms of autism.

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.

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.

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 .

Positive Allosteric Modulation of AMPA Receptors from Efficacy to Toxicity: The Interspecies Exposure-Response Continuum of the Novel Potentiator PF-4778574

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) positive allosteric modulation (i.e., “potentiation”) has been proposed to overcome cognitive impairments in schizophrenia, but AMPAR overstimulation can be excitotoxic. Thus, it is critical to define carefully a potentiator’s mechanism-based therapeutic index (TI) and to determine confidently its translatability from rodents to higher-order species. Accordingly, the novel AMPAR potentiator N-{(3R,4S)-3-[4-(5-cyano-2-thienyl)phenyl]tetrahydro-2H-pyran-4-yl}propane-2-sulfonamide (PF-4778574) was characterized in a series of in vitro assays and single-dose animal studies evaluating AMPAR-mediated activities related to cognition and safety to afford an unbound brain compound concentration (Cb,u)–normalized interspecies exposure-response relationship. Because it is unknown which AMPAR subtype(s) may be selectively potentiated for an optimal TI, PF-4778574 binding affinity and functional potency were determined in rodent tissues expected to express a native mixture of AMPAR subunits and their associated proteins to afford composite pharmacological values. Functional activity was also quantified in recombinant cell lines stably expressing human GluA2 flip or flop homotetramers. Procognitive effects of PF-4778574 were evaluated in both rat electrophysiological and nonhuman primate (nhp) behavioral models of pharmacologically induced N-methyl-d-aspartate receptor hypofunction. Safety studies assessed cerebellum-based AMPAR activation (mouse) and motor coordination disruptions (mouse, dog, and nhp), as well as convulsion (mouse, rat, and dog). The resulting empirically derived exposure-response continuum for PF-4778574 defines a single-dose-based TI of 8- to 16-fold for self-limiting tremor, a readily monitorable clinical adverse event. Importantly, the Cb,u mediating each physiological effect were highly consistent across species, with efficacy and convulsion occurring at just fractions of the in vitro–derived pharmacological values.

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.

Biaryl piperidines as potent and selective delta opioid receptor ligands

The design and synthesis of novel opiates are reported. Based on the message-address principle a novel class of 4,4- and 3,3-biaryl piperidines was designed and synthesized. Biological evaluation confirmed that these compounds exhibit high affinity and selectivity for the delta opioid receptor. Key structure-activity relationships that influence affinity, selectivity, functional activity and clearance are reported.

Discovery of CP-96,345 and its characterization in disease models involving substance P.

Studies with CP-96,345, a potent, selective, orally active, nonpeptide NK1 receptor antagonist, have provided considerable insight into SP pharmacology. Rather than being a primary neurotransmitter, SP prolongs the nociception produced by other neurotransmitters. By controlling endothelial permeability, SP plays a major role in inflammation and inflammatory aspects of asthma, possibly by regulating the access of neutrophils to an inflammatory site. These results indicate potential therapeutic applications for SP antagonists in the treatment of chronic pain, inflammation, and inflammatory aspects of asthma, and signal a new era in the clinical management of these important diseases.

Synthesis of conformationally restricted substance P antagonists

Reaction of CP-99,994 (1) with benzyl chloromethyl ether under basic conditions produced the novel 1,6-diazabicyclo[3.2.1]octane system in good yield; analogs containing this nucleus display high binding affinity for substance P receptors. The ethylene homologue of 1a, diamine 7, shows enhanced inhibitory activity and may more closely approximate the binding conformation of 1a at the NK1 receptor.

N-alkyl quinuclidinium substance P antagonists

Abstract The synthesis and SAR of bridgehead N-alkylated analogues of the nonpeptide substance P antagonist CP-96,345 are described. The results indicate that the bridgehead nitrogen may provide more of an anchoring function rather than being in intimate contact with the receptor.