Improving the oral efficacy of CNS drug candidates: discovery of highly orally efficacious piperidinyl piperidine M2 muscarinic receptor antagonists

Structural modifications to tetrahydropyridine-3-carboxylate esters en route to the discovery of M5-preferring muscarinic receptor orthosteric antagonists

The M5 muscarinic acetylcholine receptor is suggested to be a potential pharmacotherapeutic target for the treatment of drug abuse. We describe herein the discovery of a series of M5-preferring orthosteric antagonists based on the scaffold of 1,2,5,6-tetrahydropyridine-3-carboxylic acid. Compound 56, the most selective compound in this series, possesses an 11-fold selectivity for the M5 over M1 receptor and shows little activity at M2-M4. This compound, although exhibiting modest affinity (K(i) = 2.24 μM) for the [(3)H]N-methylscopolamine binding site on the M5 receptor, is potent (IC50 = 0.45 nM) in inhibiting oxotremorine-evoked [(3)H]DA release from rat striatal slices. Further, a homology model of human M5 receptor based on the crystal structure of the rat M3 receptor was constructed, and docking studies of compounds 28 and 56 were performed in an attempt to understand the possible binding mode of these novel analogues to the receptor.

Muscarinic agonists and antagonists in schizophrenia: recent therapeutic advances and future directions

Existing therapies for schizophrenia have limited efficacy, and significant residual positive, negative, and cognitive symptoms remain in many individuals with the disorder even after treatment with the current arsenal of antipsychotic drugs. Preclinical and clinical data suggest that selective activation of the muscarinic cholinergic system may represent novel therapeutic mechanisms for the treatment of schizophrenia. The therapeutic relevance of earlier muscarinic agonists was limited by their lack of receptor selectivity and adverse event profile arising from activation of nontarget muscarinic receptors. Recent advances in developing compounds that are selective to muscarinic receptor subtypes or activate allosteric receptor sites offer tremendous promise for therapeutic targeting of specific muscarinic receptor subtypes in schizophrenia.

In vivo brain microdialysis: advances in neuropsychopharmacology and drug discovery

INTRODUCTION: Microdialysis is an important in vivo sampling technique, useful in the assay of extracellular tissue fluid. The technique has both pre-clinical and clinical applications but is most widely used in neuroscience. The in vivo microdialysis technique allows measurement of neurotransmitters such as acetycholine (ACh), the biogenic amines including dopamine (DA), norepinephrine (NE) and serotonin (5-HT), amino acids such as glutamate (Glu) and gamma aminobutyric acid (GABA), as well as the metabolites of the aforementioned neurotransmitters, and neuropeptides in neuronal extracellular fluid in discrete brain regions of laboratory animals such as rodents and non-human primates. AREAS COVERED: In this review we present a brief overview of the principles and procedures related to in vivo microdialysis and detail the use of this technique in the pre-clinical measurement of drugs designed to be used in the treatment of chemical addiction, neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and as well as psychiatric disorders such as attention-deficit/hyperactivity disorder (ADHD) and schizophrenia. This review offers insight into the tremendous utility and versatility of this technique in pursuing neuropharmacological investigations as well its significant potential in rational drug discovery. EXPERT OPINION: In vivo microdialysis is an extremely versatile technique, routinely used in the neuropharmacological investigation of drugs used for the treatment of neurological disorders. This technique has been a boon in the elucidation of the neurochemical profile and mechanism of action of several classes of drugs especially their effects on neurotransmitter systems. The exploitation and development of this technique for drug discovery in the near future will enable investigational new drug candidates to be rapidly moved into the clinical trial stages and to market thus providing new successful therapies for neurological diseases that are currently in demand.

Synthesis and evaluation of N-3 substituted phenoxypropyl piperidine benzimidazol-2-one analogues as NOP receptor agonists with analgesic and sedative properties

A series of 3-phenoxypropyl piperidine benzimidazol-2-one analogues have been discovered as novel NOP receptor agonists. Structure-activity relationships have been explored via N-3 substitution of the benzimidazol-2-one with a range of functionality. The N-methyl acetamide derivative (+)-7f was found to be a high-affinity, potent NOP agonist with greater than 100-fold selectivity over the MOP receptor. Furthermore (+)-7f was shown to be both antinociceptive and sedative when administered iv to rodents.

C(8)-substituted 1-azabicyclo[3.3.1]non-3-enes: a novel scaffold for muscarinic receptor ligands

The [3.3.1]-bicyclic amine, exo-8-benzyloxymethyl-3-ethoxycarbonyl-4-hydroxy-1-azabicyclo[3.3.1]non-3-ene (1), has been shown to be a potent competitive antagonist against the hM(1)-hM(5) muscarinic receptors. This heterocyclic system has not been extensively evaluated despite the notable activities reported for other bicyclic amines. Synthetic strategies permitted the selective alteration of five structural sites in 1. Pharmacological evaluation demonstrated that modification of either the C(3) alkoxycarbonyl or the C(4) enol units in 1 gave compounds with high affinity for the hM(1)-hM(5) muscarinic receptors with selectivity for the hM(2) receptor.

Isopropyl amide derivatives of potent and selective muscarinic M2 receptor antagonists

Low molecular weight amide derivatives were synthesized and evaluated as M(2) receptor antagonists for the treatment of Alzheimer's disease. Isopropyl amides 19 and 31 are highly potent, selective and low molecular weight M(2) receptor antagonists with structural features different from our clinical candidate 1.

Muscarinic M2 antagonists: anthranilamide derivatives with exceptional selectivity and in vivo activity

Anthranilamide analogues such as 23 are potent and highly selective muscarinic M2 antagonists that also show good oral bioavailability and in vivo activity.