Bruce N. Rogers

Discovery of N-[(3R,5R)-1-azabicyclo[3.2.1]oct-3-yl]furo[2,3-c]pyridine-5-carboxamide as an agonist of the α7 nicotinic acetylcholine receptor: In vitro and in vivo activity

A novel alpha7 nAChR agonist, N-[(3R,5R)-1-azabicyclo[3.2.1]oct-3-yl]furo[2,3-c]pyridine-5-carboxamide (3a, PHA-709829), has been identified for the potential treatment of cognitive deficits in schizophrenia. The compound shows potent and selective alpha7 in vitro activity, excellent brain penetration, good rat oral bioavailability and robust in vivo efficacy in a rat auditory sensory gating model.

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.

3-Benzyl-1,3-oxazolidin-2-ones as mGluR2 positive allosteric modulators: Hit-to lead and lead optimization.

The discovery, synthesis and SAR of a novel series of 3-benzyl-1,3-oxazolidin-2-ones as positive allosteric modulators (PAMs) of mGluR2 is described. Expedient hit-to-lead work on a single HTS hit led to the identification of a ligand-efficient and structurally attractive series of mGluR2 PAMs. Human microsomal clearance and suboptimal physicochemical properties of the initial lead were improved to give potent, metabolically stable and orally available mGluR2 PAMs.

Discovery and preclinical characterization of 1-methyl-3-(4-methylpyridin-3-yl)-6-(pyridin-2-ylmethoxy)-1H-pyrazolo-[3,4-b]pyrazine (PF470): a highly potent, selective, and efficacious metabotropic glutamate receptor 5 (mGluR5) negative allosteric modulator.

A novel series of pyrazolopyrazines is herein disclosed as mGluR5 negative allosteric modulators (NAMs). Starting from a high-throughput screen (HTS) hit (1), a systematic structure-activity relationship (SAR) study was conducted with a specific focus on balancing pharmacological potency with physicochemical and pharmacokinetic (PK) properties. This effort led to the discovery of 1-methyl-3-(4-methylpyridin-3-yl)-6-(pyridin-2-ylmethoxy)-1H-pyrazolo[3,4-b]pyrazine (PF470, 14) as a highly potent, selective, and orally bioavailable mGluR5 NAM. Compound 14 demonstrated robust efficacy in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-rendered Parkinsonian nonhuman primate model of l-DOPA-induced dyskinesia (PD-LID). However, the progression of 14 to the clinic was terminated because of a potentially mechanism-mediated finding consistent with a delayed-type immune-mediated type IV hypersensitivity in a 90-day NHP regulatory toxicology study.

Utilizing Structures of CYP2D6 and BACE1 Complexes To Reduce Risk of Drug-Drug Interactions with a Novel Series of Centrally Efficacious BACE1 Inhibitors.

In recent years, the first generation of β-secretase (BACE1) inhibitors advanced into clinical development for the treatment of Alzheimer’s disease (AD). However, the alignment of drug-like properties and selectivity remains a major challenge. Herein, we describe the discovery of a novel class of potent, low clearance, CNS penetrant BACE1 inhibitors represented by thioamidine 5. Further profiling suggested that a high fraction of the metabolism (>95%) was due to CYP2D6, increasing the potential risk for victim-based drug–drug interactions (DDI) and variable exposure in the clinic due to the polymorphic nature of this enzyme. To guide future design, we solved crystal structures of CYP2D6 complexes with substrate 5 and its corresponding metabolic product pyrazole 6, which provided insight into the binding mode and movements between substrate/inhibitor complexes. Guided by the BACE1 and CYP2D6 crystal structures, we designed and synthesized analogues with reduced risk for DDI, central efficacy, and improved hERG therapeutic margins.

3-(Imidazolyl methyl)-3-aza-bicyclo[3.1.0]hexan-6-yl)methyl ethers: A novel series of mGluR2 positive allosteric modulators

The synthesis and structure-activity relationship (SAR) of a novel series of 3-(imidazolyl methyl)-3-aza-bicyclo[3.1.0]hexan-6-yl)methyl ethers, derived from a high throughput screening (HTS), are described. Subsequent optimization led to identification of potent, metabolically stable and orally available mGluR2 positive allosteric modulators (PAMs).

1-[(1-methyl-1H-imidazol-2-yl)methyl]-4-phenylpiperidines as mGluR2 positive allosteric modulators for the treatment of psychosis.

A novel series of mGluR2 positive allosteric modulators (PAMs), 1-[(1-methyl-1H-imidazol-2-yl)methyl]-4-phenylpiperidines, is herein disclosed. Structure-activity relationship studies led to potent, selective mGluR2 PAMs with excellent pharmacokinetic profiles. A representative lead compound (+)-17e demonstrated dose-dependent inhibition of methamphetamine-induced hyperactivity and mescaline-induced scratching in mice, providing support for potential efficacy in treating psychosis.

Discovery of a novel Kv7 channel opener as a treatment for epilepsy.

Facilitating activation, or delaying inactivation, of the native Kv7 channel reduces neuronal excitability, which may be beneficial in controlling spontaneous electrical activity during epileptic seizures. In an effort to identify a compound with such properties, the structure-activity relationship (SAR) and in vitro ADME for a series of heterocyclic Kv7.2-7.5 channel openers was explored. PF-05020182 (2) demonstrated suitable properties for further testing in vivo where it dose-dependently decreased the number of animals exhibiting full tonic extension convulsions in response to corneal stimulation in the maximal electroshock (MES) assay. In addition, PF-05020182 (2) significantly inhibited convulsions in the MES assay at doses tested, consistent with in vitro activity measure. The physiochemical properties, in vitro and in vivo activities of PF-05020182 (2) support further development as an adjunctive treatment of refractory epilepsy.

Systematic N-methylation of oxytocin: Impact on pharmacology and intramolecular hydrogen bonding network.

Oxytocin (OT) is a peptide hormone agonist of the OT receptor (OTR) that plays an important role in social behaviors such as pair bonding, maternal bonding and trust. The pharmaceutical development of OT as an oral peptide therapeutic has been hindered historically by its unfavorable physicochemical properties, including molecular weight, polarity and number of hydrogen bond donors, which determines poor cell permeability. Here we describe the first systematic study of single and multiple N-methylations of OT and their effect on physicochemical properties as well as potency at the OT receptor. The agonist EC50 and percent effect for OTR are reported and show that most N-methylations are tolerated but with some loss in potency compared to OT. The effect of N-methylation on exposed polarity is assessed through the EPSA chromatographic method and the results validated against NMR temperature coefficient experiments and the determination of NMR solution structures. We found that backbone methylation of residues not involved in IMHB and removal of the N-terminal amine can significantly reduce the exposed polarity of peptides, and yet retain a significant OTR agonist activity. The results of this study also expose the potential challenge of using the N-methylation strategy for the OT system; while exposed polarity is reduced, in some cases backbone methylation produces a significant conformational change that compromises agonist activity. The data presented provides useful insights on the SAR of OT and suggests future design strategies that can be used to develop more permeable OTR agonists based on the OT framework.

Chapter 15:Identification of α7 Nicotinic Acetylcholine Receptor Agonists for their Assessment in Improving Cognition in Schizophrenia

The α7 nicotinic acetylcholine receptor (nAChR) has been a target of interest to the neuroscience area for the treatment of cognitive deficits in schizophrenia for some time. The pentameric α7 nAChR is the most abundant nAChR in the brain and consist of five α7 subunits, each with an orthosteric low affinity binding site for the endogenous agonist, acetylcholine. This account describes the discovery efforts undertaken at Pharmacia and Pfizer to identify novel agonists of the α7 nAChR. It establishes the importance of a robust High Throughput Screen (HTS) to identify high quality chemical matter, and the critical nature of lead optimization strategies to deliver a series of compounds to enter the clinical setting. In addition to the medicinal chemistry efforts, the full screening strategy and path to the clinic are described for compounds emerging from the synergies of merging two independent programs into one. This target remains a challenge within the pharmaceutical industry, which is charged with delivering innovative medicines to patients with schizophrenia.