Melanin-Concentrating Hormone Receptor 1 Antagonists Lacking an Aliphatic Amine: Synthesis and Structure–Activity Relationships of Novel 1-(Imidazo[1,2-a]pyridin-6-yl)pyridin-2(1H)-one Derivatives

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• 作者：Hideyuki Igawa ; Masashi Takahashi ; Keiko Kakegawa ; Asato Kina ; Minoru Ikoma ; Jumpei Aida ; Tsuneo Yasuma ; Yayoi Kawata ; Shuntaro Ashina ; Syunsuke Yamamoto ; Mrinalkanti Kundu ; Uttam Khamrai ; Hideki Hirabayashi ; Masaharu Nakayama ; Yasutaka Nagisa ; Shizuo Kasai ; Tsuyoshi Maekawa
• 刊名：Journal of Medicinal Chemistry
• 出版年：2016
• 出版时间：February 11, 2016
• 年：2016
• 卷：59
• 期：3
• 页码：1116-1139
• 全文大小：1007K
• ISSN：1520-4804

文摘

Aiming to discover melanin-concentrating hormone receptor 1 (MCHR1) antagonists with improved safety profiles, we hypothesized that the aliphatic amine employed in most antagonists reported to date could be removed if the bicyclic motif of the compound scaffold interacted with Asp123 and/or Tyr272 of MCHR1. We excluded aliphatic amines from our compound designs, with a cutoff value of pK_a < 8, and explored aliphatic amine-free MCHR1 antagonists in a CNS-oriented chemical space limited by four descriptors (TPSA, ClogP, MW, and HBD count). Screening of novel bicyclic motifs with high intrinsic binding affinity for MCHR1 identified the imidazo[1,2-a]pyridine ring (represented in compounds 6a and 6b), and subsequent cyclization of the central aliphatic amide linkage led to the discovery of a potent, orally bioavailable MCHR1 antagonist 4-[(4-chlorobenzyl)oxy]-1-(2-cyclopropyl-3-methylimidazo[1,2-a]pyridin-6-yl)pyridin-2(1H)-one 10a. It exhibited low potential for hERG inhibition and phospholipidosis induction as well as sufficient brain concentration to exert antiobesity effects in diet-induced obese rats.