Allen J. Duplantier

Discovery, SAR, and Pharmacokinetics of a Novel 3-Hydroxyquinolin-2(1H)-one Series of Potent d-Amino Acid Oxidase (DAAO) Inhibitors†

3-Hydroxyquinolin-2(1H)-one (2) was discovered by high throughput screening in a functional assay to be a potent inhibitor of human DAAO, and its binding affinity was confirmed in a Biacore assay. Cocrystallization of 2 with the human DAAO enzyme defined the binding site and guided the design of new analogues. The SAR, pharmacokinetics, brain exposure, and effects on cerebellum D-serine are described. Subsequent evaluation against the rat DAAO enzyme revealed a divergent SAR versus the human enzyme and may explain the high exposures of drug necessary to achieve significant changes in rat or mouse cerebellum D-serine.

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.

Optimization of the physicochemical and pharmacokinetic attributes in a 6-azauracil series of P2X7 receptor antagonists leading to the discovery of the clinical candidate CE-224,535

High throughput screening (HTS) of our compound file provided an attractive lead compound with modest P2X(7) receptor antagonist potency and high selectivity against a panel of receptors and channels, but also with high human plasma protein binding and a predicted short half-life in humans. Multi-parameter optimization was used to address the potency, physicochemical and pharmacokinetic properties which led to potent P2X(7)R antagonists with good disposition properties. Compound 33 (CE-224,535) was advanced to clinical studies for the treatment of rheumatoid arthritis.

Synthesis and in vitro profile of a novel series of catechol benzimidazoles. The discovery of potent, selective phosphodiesterase type IV inhibitors with greatly attenuated affinity for the [3H]rolipram binding site

Abstract The synthesis and biological properties of a novel series of potent and selective phosphodiesterase type IV (PDE IV) inhibitors are described. These catechol benzimidazoles were designed from rolipram and initial compounds reflected a similarly high affinity for the [ 3 H]rolipram b binding site (500 to 1000X greater affinity for the [ 3 H]rolipram binding site over the PDE IV inhibitory site). However, SAR studies on the 3-alkoxy position revealed that this [ 3 H]rolipram binding site affinity could be attenuated, while potentiating the PDE IV inhibitory activity. This resulted in the 2-indanyl analog 13 which is a potent, selective PDE IV inhibitor with a 15X differential in favor of PDE IV binding.

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.

Modulation of NMDA receptor function by inhibition of d-amino acid oxidase in rodent brain

Observations that N-Methyl-D-Aspartate (NMDA) antagonists produce symptoms in humans that are similar to those seen in schizophrenia have led to the current hypothesis that schizophrenia might result from NMDA receptor hypofunction. Inhibition of D-amino acid oxidase (DAAO), the enzyme responsible for degradation of D-serine, should lead to increased levels of this co-agonist at the NMDA receptor, and thereby provide a therapeutic approach to schizophrenia. We have profiled some of the preclinical biochemical, electrophysiological, and behavioral consequences of administering potent and selective inhibitors of DAAO to rodents to begin to test this hypothesis. Inhibition of DAAO activity resulted in a significant dose and time dependent increase in D-serine only in the cerebellum, although a time delay was observed between peak plasma or brain drug concentration and cerebellum D-serine response. Pharmacokinetic/pharmacodynamic (PK/PD) modeling employing a mechanism-based indirect response model was used to characterize the correlation between free brain drug concentration and D-serine accumulation. DAAO inhibitors had little or no activity in rodent models considered predictive for antipsychotic activity. The inhibitors did, however, affect cortical activity in the Mescaline-Induced Scratching model, produced a modest but significant increase in NMDA receptor-mediated synaptic currents in primary neuronal cultures from rat hippocampus, and resulted in a significant increase in evoked hippocampal theta rhythm, an in vivo electrophysiological model of hippocampal activity. These findings demonstrate that although DAAO inhibition did not cause a measurable increase in D-serine in forebrain, it did affect hippocampal and cortical activity, possibly through augmentation of NMDA receptor-mediated currents.

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).

Biarylcarboxamide inhibitors of phosphodiesterase IV and tumor necrosis factor-α

Abstract Tumor necrosis factor-α (TNF-α) has been implicated as a key mediator in the progression of rheumatoid arthritis. Inhibitors of phosphodiesterase IV (PDE IV) have been shown to inhibit the production of TNF-α by elevating intracellular levels of cyclic adenosine monophosphate (cAMP). Our efforts in a series of biarylcarboxamides have led to the identification of 8j (CP-353,164) as a potent inhibitor of PDE IV and TNF-α production.

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, synthesis and SAR of azinyl- and azolylbenzamides antagonists of the P2X7 receptor

The discovery, of a series of 2-Cl-5-heteroaryl-benzamide antagonists of the P2X(7) receptor via parallel medicinal chemistry is described. Initial analogs suffered from poor metabolic stability and low Vd(ss). Multi parametric optimization led to identification of pyrazole 39 as a viable lead with excellent potency and oral bioavailability. Further attempts to improve the low Vd(ss) of 39 via introduction of amines led to analogs 40 and 41 which maintained the favorable pharmacology profile of 39 and improved Vd(ss) after iv dosing. But these analogs suffered from poor oral absorption, probably driven by poor permeability.