RESUMO
Multiple therapeutic opportunities have been suggested for compounds capable of selective activation of metabotropic glutamate 3 (mGlu3) receptors, but small molecule tools are lacking. As part of our ongoing efforts to identify potent, selective, and systemically bioavailable agonists for mGlu2 and mGlu3 receptor subtypes, a series of C4ß-N-linked variants of (1 S,2 S,5 R,6 S)-2-amino-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 1 (LY354740) were prepared and evaluated for both mGlu2 and mGlu3 receptor binding affinity and functional cellular responses. From this investigation we identified (1 S,2 S,4 S,5 R,6 S)-2-amino-4-[(3-methoxybenzoyl)amino]bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 8p (LY2794193), a molecule that demonstrates remarkable mGlu3 receptor selectivity. Crystallization of 8p with the amino terminal domain of hmGlu3 revealed critical binding interactions for this ligand with residues adjacent to the glutamate binding site, while pharmacokinetic assessment of 8p combined with its effect in an mGlu2 receptor-dependent behavioral model provides estimates for doses of this compound that would be expected to selectively engage and activate central mGlu3 receptors in vivo.
Assuntos
Compostos Bicíclicos com Pontes/síntese química , Compostos Bicíclicos com Pontes/farmacologia , Agonistas de Aminoácidos Excitatórios/síntese química , Agonistas de Aminoácidos Excitatórios/farmacologia , Receptores de Glutamato Metabotrópico/agonistas , Animais , Compostos Bicíclicos com Pontes/farmacocinética , Cristalografia por Raios X , AMP Cíclico/farmacologia , Agonistas de Aminoácidos Excitatórios/farmacocinética , Antagonistas de Aminoácidos Excitatórios/farmacologia , Humanos , Masculino , Modelos Moleculares , Simulação de Acoplamento Molecular , Estrutura Molecular , Atividade Motora/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fenciclidina/antagonistas & inibidores , Fenciclidina/farmacologia , Ligação Proteica , Ratos , Ratos Sprague-DawleyRESUMO
Identification of orthosteric mGlu(2/3) receptor agonists capable of discriminating between individual mGlu2 and mGlu3 subtypes has been highly challenging owing to the glutamate-site sequence homology between these proteins. Herein we detail the preparation and characterization of a series of molecules related to (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate 1 (LY354740) bearing C4-thiotriazole substituents. On the basis of second messenger responses in cells expressing other recombinant human mGlu2/3 subtypes, a number of high potency and efficacy mGlu2 receptor agonists exhibiting low potency mGlu3 partial agonist/antagonist activity were identified. From this, (1R,2S,4R,5R,6R)-2-amino-4-(1H-1,2,4-triazol-3-ylsulfanyl)bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 14a (LY2812223) was further characterized. Cocrystallization of 14a with the amino terminal domains of hmGlu2 and hmGlu3 combined with site-directed mutation studies has clarified the underlying molecular basis of this unique pharmacology. Evaluation of 14a in a rat model responsive to mGlu2 receptor activation coupled with a measure of central drug disposition provides evidence that this molecule engages and activates central mGlu2 receptors in vivo.
Assuntos
Compostos Bicíclicos com Pontes/química , Receptores de Glutamato Metabotrópico/agonistas , Triazóis/química , Regulação Alostérica , Animais , Ligação Competitiva , Compostos Bicíclicos com Pontes/farmacocinética , Compostos Bicíclicos com Pontes/farmacologia , Cálcio/metabolismo , AMP Cíclico/metabolismo , Cães , Agonismo Parcial de Drogas , Humanos , Masculino , Camundongos , Modelos Moleculares , Atividade Motora/efeitos dos fármacos , Mutagênese Sítio-Dirigida , Estrutura Terciária de Proteína , Ratos Sprague-Dawley , Receptores de Glutamato Metabotrópico/antagonistas & inibidores , Receptores de Glutamato Metabotrópico/genética , Receptores de Glutamato Metabotrópico/metabolismo , Estereoisomerismo , Triazóis/farmacocinética , Triazóis/farmacologiaRESUMO
Kappa opioid receptors and their endogenous neuropeptide ligand, dynorphin A, are densely localized in limbic and cortical areas comprising the brain reward system, and appear to play a key role in modulating stress and mood. Growing literature indicates that kappa receptor antagonists may be beneficial in the treatment of mood and addictive disorders. However, existing literature on kappa receptor antagonists has used extensively JDTic and nor-BNI which exhibit long-lasting pharmacokinetic properties that complicate experimental design and interpretation of results. Herein, we report for the first time the in vitro and in vivo pharmacological profile of a novel, potent kappa opioid receptor antagonist with excellent selectivity over other receptors and markedly improved drug-like properties over existing research tools. LY2456302 exhibits canonical pharmacokinetic properties that are favorable for clinical development, with rapid absorption (t(max): 1-2 h) and good oral bioavailability (F = 25%). Oral LY2456302 administration selectively and potently occupied central kappa opioid receptors in vivo (ED50 = 0.33 mg/kg), without evidence of mu or delta receptor occupancy at doses up to 30 mg/kg. LY2456302 potently blocked kappa-agonist-mediated analgesia and disruption of prepulse inhibition, without affecting mu-agonist-mediated effects at doses >30-fold higher. Importantly, LY2456302 did not block kappa-agonist-induced analgesia one week after administration, indicating lack of long-lasting pharmacodynamic effects. In contrast to the nonselective opioid antagonist naltrexone, LY2456302 produced antidepressant-like effects in the mouse forced swim test and enhanced the effects of imipramine and citalopram. LY2456302 reduced ethanol self-administration in alcohol-preferring (P) rats and, unlike naltrexone, did not exhibit significant tolerance upon 4 days of repeated dosing. LY2456302 is a centrally-penetrant, potent, kappa-selective antagonist with pharmacokinetic properties favorable for clinical development and activity in animal models predictive of efficacy in mood and addictive disorders.