Discovery Of Highly Potent And Selective α4β2-Nicotinic Acetylcholine Receptor (Nachr) Partial Agonists Containing An Isoxazolylpyridine Ether Scaffold That Demonstrate Antidepressant-Like Activity. Part II

In our continued efforts to develop α4β2-nicotinic acetylcholine receptor (nAChR) partial agonists as novel antidepressants having a unique mechanism of action, structure-activity relationship (SAR) exploration of certain isoxazolylpyridine ethers is presented. In particular, modifications to both the azetidine ring present in the starting structure 4 and its metabolically liable hydroxyl side chain substituent have been explored to improve compound druggability. The pharmacological characterization of all new compounds has been carried out using [ 3 H]epibatidine binding studies together with functional assays based on 86 Rb + ion flux measurements. We found that the deletion of the metabolically liable hydroxyl group or its replacement by a fluoromethyl group not only maintained potency and selectivity but also resulted in compounds showing antidepressant-like properties in the mouse forced swim test. These isoxazolylpyridine ethers appear to represent promising lead candidates in the design of innovative chemical tools containing reporter groups for imaging purposes and of possible therapeutics. © 2012 American Chemical Society

Identification Of Novel α4β2-Nicotinic Acetylcholine Receptor (Nachr) Agonists Based On An Isoxazole Ether Scaffold That Demonstrate Antidepressant-Like Activity

There is considerable evidence to support the hypothesis that the blockade of nAChR is responsible for the antidepressant action of nicotinic ligands. The nicotinic acetylcholine receptor (nAChR) antagonist, mecamylamine, has been shown to be an effective add-on in patients that do not respond to selective serotonin reuptake inhibitors. This suggests that nAChR ligands may address an unmet clinical need by providing relief from depressive symptoms in refractory patients. In this study, a new series of nAChR ligands based on an isoxazole-ether scaffold have been designed and synthesized for binding and functional assays. Preliminary structure-activity relationship (SAR) efforts identified a lead compound 43, which possesses potent antidepressant-like activity (1 mg/kg, IP; 5 mg/kg, PO) in the classical mouse forced swim test. Early stage absorption, distribution, metabolism, excretion, and toxicity (ADME-Tox) studies also suggested favorable drug-like properties, and broad screening toward other common neurotransmitter receptors indicated that compound 43 is highly selective for nAChRs over the other 45 neurotransmitter receptors and transporters tested. © 2011 American Chemical Society

Discovery Of Isoxazole Analogues Of Sazetidine-A As Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists For The Treatment Of Depression

Depression, a common neurological condition, is one of the leading causes of disability and suicide worldwide. Standard treatment, targeting monoamine transporters selective for the neurotransmitters serotonin and noradrenaline, is not able to help many patients that are poor responders. This study advances the development of sazetidine-A analogues that interact with α4β2 nicotinic acetylcholine receptors (nAChRs) as partial agonists and that possess favorable antidepressant profiles. The resulting compounds that are highly selective for the α4β2 subtype of nAChR over α3β4-nAChRs are partial agonists at the α4β2 subtype and have excellent antidepressant behavioral profiles as measured by the mouse forced swim test. Preliminary absorption, distribution, metabolism, excretion, and toxicity (ADMET) studies for one promising ligand revealed an excellent plasma protein binding (PPB) profile, low CYP450-related metabolism, and low cardiovascular toxicity, suggesting it is a promising lead as well as a drug candidate to be advanced through the drug discovery pipeline. © 2011 American Chemical Society

Chemistry And Behavioral Studies Identify Chiral Cyclopropanes As Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists Exhibiting An Antidepressant Profile

Despite their discovery in the early 20th century and intensive study over the last 20 years, nicotinic acetylcholine receptors (nAChRs) are still far from being well understood. Only a few chemical entities targeting nAChRs are currently undergoing clinical trials, and even fewer have reached the marketplace. In our efforts to discover novel and truly selective nAChR ligands, we designed and synthesized a series of chiral cyclopropane-containing α4β2-specific ligands that display low nanomolar binding affinities and excellent subtype selectivity while acting as partial agonists at α4β2-nAChRs. Their favorable antidepressant-like properties were demonstrated in the classical mouse forced swim test. Preliminary ADMET studies and broad screening toward other common neurotransmitter receptors were also carried out to further evaluate their safety profile and eliminate their potential off-target activity. These highly potent cyclopropane ligands possess superior subtype selectivity compared to other α4β2-nAChR agonists reported to date, including the marketed drug varenicline, and therefore may fully satisfy the crucial prerequisite for avoiding adverse side effects. These novel chemical entities could potentially be advanced to the clinic as new drug candidates for treating depression. © 2011 American Chemical Society

Identification of Novel α4β2-Nicotinic Acetylcholine Receptor (nAChR) Agonists Based on an Isoxazole Ether Scaffold that Demonstrate Antidepressant-like Activity

There is considerable evidence to support the hypothesis that the blockade of nAChR is responsible for the antidepressant action of nicotinic ligands. The nicotinic acetylcholine receptor (nAChR) antagonist, mecamylamine, has been shown to be an effective add-on in patients that do not respond to selective serotonin reuptake inhibitors. This suggests that nAChR ligands may address an unmet clinical need by providing relief from depressive symptoms in refractory patients. In this study, a new series of nAChR ligands based on an isoxazole-ether scaffold have been designed and synthesized for binding and functional assays. Preliminary structure–activity relationship (SAR) efforts identified a lead compound <b>43</b>, which possesses potent antidepressant-like activity (1 mg/kg, IP; 5 mg/kg, PO) in the classical mouse forced swim test. Early stage absorption, distribution, metabolism, excretion, and toxicity (ADME-Tox) studies also suggested favorable drug-like properties, and broad screening toward other common neurotransmitter receptors indicated that compound <b>43</b> is highly selective for nAChRs over the other 45 neurotransmitter receptors and transporters tested

Synthesis and biological evaluation of novel hybrids of highly potent and selective a4ß2-Nicotinic acetylcholine receptor (nAChR) partial agonists

© 2016 Elsevier Masson SASWe previously reported the cyclopropylpyridine and isoxazolylpyridine ether scaffolds to be versatile building blocks for creating potent a4ß2 nicotinic acetylcholine receptor (nAChR) partial agonists with excellent selectivity over the a3ß4 subtype. In our continued efforts to develop therapeutic nicotinic ligands, seven novel hybrid compounds were rationally designed, synthesized, and evaluated in [3H]epibatidine binding competition studies. Incorporation of a cyclopropane- or isoxazole-containing side chain onto the 5-position of 1-(pyridin-3-yl)-1,4-diazepane or 2-(pyridin-3-yl)-2,5-diazabicyclo[2.2.1]heptane led to highly potent and selective a4ß2* nAChR partial agonists with Ki values of 0.5–51.4 nM for a4ß2 and negligible affinities for a3ß4 and a7. Moreover, compounds 21, 25, and 30 maintained the functional profiles (EC50 and IC50 values of 15–50 nM) of the parent azetidine-containing compounds 3 and 4 in the 86Rb+ ion flux assays. In vivo efficacy of the most promising compound 21 was confirmed in the mouse SmartCube® platform and classical forced swim tests, supporting the potential use of a4ß2 partial agonists for treatment of depression

Chemistry and Behavioral Studies Identify Chiral Cyclopropanes as Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists Exhibiting an Antidepressant Profile

Despite their discovery in the early 20th century and intensive study over the last 20 years, nicotinic acetylcholine receptors (nAChRs) are still far from being well understood. Only a few chemical entities targeting nAChRs are currently undergoing clinical trials, and even fewer have reached the marketplace. In our efforts to discover novel and truly selective nAChR ligands, we designed and synthesized a series of chiral cyclopropane-containing α4β2-specific ligands that display low nanomolar binding affinities and excellent subtype selectivity while acting as partial agonists at α4β2–nAChRs. Their favorable antidepressant-like properties were demonstrated in the classical mouse forced swim test. Preliminary ADMET studies and broad screening toward other common neurotransmitter receptors were also carried out to further evaluate their safety profile and eliminate their potential off-target activity. These highly potent cyclopropane ligands possess superior subtype selectivity compared to other α4β2-nAChR agonists reported to date, including the marketed drug varenicline, and therefore may fully satisfy the crucial prerequisite for avoiding adverse side effects. These novel chemical entities could potentially be advanced to the clinic as new drug candidates for treating depression

Chemistry and Behavioral Studies Identify Chiral Cyclopropanes as Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists Exhibiting an Antidepressant Profile

Despite their discovery in the early 20th century and intensive study over the last 20 years, nicotinic acetylcholine receptors (nAChRs) are still far from being well understood. Only a few chemical entities targeting nAChRs are currently undergoing clinical trials, and even fewer have reached the marketplace. In our efforts to discover novel and truly selective nAChR ligands, we designed and synthesized a series of chiral cyclopropane-containing α4β2-specific ligands that display low nanomolar binding affinities and excellent subtype selectivity while acting as partial agonists at α4β2–nAChRs. Their favorable antidepressant-like properties were demonstrated in the classical mouse forced swim test. Preliminary ADMET studies and broad screening toward other common neurotransmitter receptors were also carried out to further evaluate their safety profile and eliminate their potential off-target activity. These highly potent cyclopropane ligands possess superior subtype selectivity compared to other α4β2-nAChR agonists reported to date, including the marketed drug varenicline, and therefore may fully satisfy the crucial prerequisite for avoiding adverse side effects. These novel chemical entities could potentially be advanced to the clinic as new drug candidates for treating depression

Insights into the Structural Determinants Required for High-Affinity Binding of Chiral Cyclopropane-Containing Ligands to α4β2-Nicotinic Acetylcholine Receptors: An Integrated Approach to Behaviorally Active Nicotinic Ligands

Structure-based drug design can potentially accelerate the development of new therapeutics. In this study, a cocrystal structure of the acetylcholine binding protein (AChBP) from Capitella teleta (Ct) in complex with a cyclopropane-containing selective α4β2-nicotinic acetylcholine receptor (nAChR) partial agonist (compound <b>5</b>) was acquired. The structural determinants required for ligand binding obtained from this AChBP X-ray structure were used to refine a previous model of the human α4β2-nAChR, thus possibly providing a better understanding of the structure of the human receptor. To validate the potential application of the structure of the Ct-AChBP in the engineering of new α4β2-nAChR ligands, homology modeling methods, combined with in silico ADME calculations, were used to design analogues of compound <b>5</b>. The most promising compound, <b>12</b>, exhibited an improved metabolic stability in comparison to the parent compound <b>5</b> while retaining favorable pharmacological parameters together with appropriate behavioral end points in the rodent studies