Discovery and Metabolic Stabilization of Potent and Selective 2-Amino-N-(adamant-2-yl) Acetamide 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitors

Starting from a rapidly metabolized adamantane 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitor 22a, a series of E-5-hydroxy-2-adamantamine inhibitors, exemplified by 22d and (±)-22f, was discovered. Many of these compounds are potent inhibitors of 11β-HSD1 and are selective over 11β-HSD2 for multiple species (human, mouse, and rat), unlike other reported species-selective series. These compounds have good cellular potency and improved microsomal stability. Pharmacokinetic profiling in rodents indicated moderate to large volumes of distribution, short half-lives, and a pharmacokinetic species difference with the greatest exposure measured in rat with 22d. One hour postdose liver, adipose, and brain tissue 11β-HSD1 inhibition was confirmed with (±)-22f in a murine ex vivo assay. Although 5,7-disubstitued-2-adamantamines provided greater stability, a single, E-5-position, polar functional group afforded inhibitors with the best combination of stability, potency, and selectivity. These results indicate that adamantane metabolic stabilization sufficient to obtain short-acting, potent, and selective 11β-HSD1 inhibitors has been discovered.