Biotransformation of a Novel Positive Allosteric Modulator of Metabotropic Glutamate Receptor Subtype 5 Contributes to Seizure-Like Adverse Events in Rats Involving a Receptor Agonism-Dependent Mechanism
作者:Thomas M. Bridges、Jerri M. Rook、Meredith J. Noetzel、Ryan D. Morrison、Ya Zhou、Rocco D. Gogliotti、Paige N. Vinson、Zixiu Xiang、Carrie K. Jones、Colleen M. Niswender、Craig W. Lindsley、Shaun R. Stauffer、P. Jeffrey Conn、J. Scott Daniels
DOI:10.1124/dmd.113.052084
日期:2013.9
Activation of metabotropic glutamate receptor subtype 5 (mGlu5) represents a novel strategy for therapeutic intervention into multiple central nervous system disorders, including schizophrenia. Recently, a number of positive allosteric modulators (PAMs) of mGlu5 were discovered to exhibit in vivo efficacy in rodent models of psychosis, including PAMs possessing varying degrees of agonist activity (ago-PAMs), as well as PAMs devoid of agonist activity. However, previous studies revealed that ago-PAMs can induce seizure activity and behavioral convulsions, whereas pure mGlu5 PAMs do not induce these adverse effects. We recently identified a potent and selective mGlu5 PAM, VU0403602, that was efficacious in reversing amphetamine-induced hyperlocomotion in rats. The compound also induced time-dependent seizure activity that was blocked by coadministration of the mGlu5 antagonist, 2-methyl-6-(phenylethynyl) pyridine. Consistent with potential adverse effects induced by ago-PAMs, we found that VU0403602 had significant allosteric agonist activity. Interestingly, inhibition of VU0403602 metabolism in vivo by a pan cytochrome P450 (P450) inactivator completely protected rats from induction of seizures. P450-mediated biotransformation of VU0403602 was discovered to produce another potent ago-PAM metabolite-ligand (M1) of mGlu5. Electrophysiological studies in rat hippocampal slices confirmed agonist activity of both M1 and VU0403602 and revealed that M1 can induce epileptiform activity in a manner consistent with its proconvulsant behavioral effects. Furthermore, unbound brain exposure of M1 was similar to that of the parent compound, VU0403602. These findings indicate that biotransformation of mGlu5 PAMs to active metabolite-ligands may contribute to the epileptogenesis observed after in vivo administration of this class of allosteric receptor modulators.
代谢型谷氨酸受体亚型 5 (mGlu5) 的激活代表了一种治疗干预多种中枢神经系统疾病(包括精神分裂症)的新策略。最近,发现许多 mGlu5 正变构调节剂 (PAM) 在啮齿动物精神病模型中表现出体内功效,包括具有不同程度激动剂活性的 PAM (ago-PAM) 以及缺乏激动剂活性的 PAM。然而,之前的研究表明,ago-PAM 可以诱发癫痫发作和行为惊厥,而纯 mGlu5 PAM 不会诱发这些不良反应。我们最近发现了一种有效且选择性的 mGlu5 PAM,VU0403602,它可以有效逆转安非他明诱导的大鼠过度运动。该化合物还诱导时间依赖性癫痫发作,但与 mGlu5 拮抗剂 2-甲基-6-(苯乙炔基)吡啶合用可阻断该癫痫发作。与 ago-PAM 引起的潜在不良反应一致,我们发现 VU0403602 具有显着的变构激动剂活性。有趣的是,通过泛细胞色素 P450 (P450) 灭活剂抑制 VU0403602 体内代谢,可以完全保护大鼠免于诱发癫痫发作。发现 P450 介导的 VU0403602 生物转化可产生 mGlu5 的另一种有效的 ago-PAM 代谢物配体 (M1)。对大鼠海马切片的电生理学研究证实了 M1 和 VU0403602 的激动剂活性,并揭示 M1 可以以其促惊厥行为效应一致的方式诱导癫痫样活动。此外,M1 的未结合脑暴露与母体化合物 VU0403602 相似。这些发现表明,mGlu5 PAM 生物转化为活性代谢物配体可能有助于体内施用此类变构受体调节剂后观察到的癫痫发生。