Directed screening of compounds selected from the Glaxo registry file for contractile activity on the isolated guinea pig gallbladder (GPGB) identified a series of 1,5-benzodiazepines with peripheral cholecystokinin (CCK) receptor agonist activity. Agonist efficacy within this series was modulated by variation of substituents on the N1-anilinoacetamide moiety. Remarkably, a single methyl group confers agonist activity, with an N-isopropyl substituent providing optimal efficacy. Hydrophilic substituents on the anilino nitrogen abolish agonist activity or produce antagonists of CCK. In contrast, hydrophilic electron-donating groups at the para-position of the anilino ring enhance or maintain in vitro and in vivo agonist activity. Despite decreased affinity for the human CCK-A receptor, relative to CCK-8, some of these compounds are equipotent to CCK as anorectic agents in rats following intraperitoneal administration.
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Avoiding cardiac liability associated with blockade of hERG (human ether a go-go) is key for successful drug discovery and development. This paper describes the work undertaken in the discovery of a potent CCR5 antagonist, maraviroc 34, for the treatment of HIV. In particular the use of a pharmacophore model of the hERG channel and a high throughput binding assay for the hERG channel are described that were critical to elucidate SAR to overcome hERG liabilities. The key SAR involves the introduction of polar substituents into regions of the molecule where it is postulated to undergo hydrophobic interactions with the ion channel. Within the CCR5 project there appeared to be no strong correlation between hERG affinity and physiochemical parameters such as pKa or lipophilicity. It is believed that chemists could apply these same strategies early in drug discovery to remove hERG interactions associated with lead compounds while retaining potency at the primary target.
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