Further Studies with the 2-Amino-1,3-thiazol-4(5H)-one Class of 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitors: Reducing Pregnane X Receptor Activity and Exploring Activity in a Monkey Pharmacodynamic Model

A series of compounds containing the 2-amino-1,3-thiazol-4(5H)-one core were found to be potent inhibitors of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). One of our lead compounds from this series activated the human nuclear xenobiotic receptor, pregnane X receptor (PXR). To try and mitigate the PXR activity, we prepared analogues of our lead series that contained polar groups on the right-hand side of the thiazolone. Several analogues containing amides or alcohols appended to the C-5 position of the thiazolone showed a significant reduction in PXR activity. Through these structure−activity efforts, a compound containing a tert-alcohol group off the C-5 position, analogue (S)-33a, was found to have an 11β-HSD1 Ki = 35 nM and negligible PXR activity. Compound (S)-33a was advanced into a pharmacodynamic model in cynomolgus monkeys, where it inhibited adipose 11β-HSD1 activity after being orally administered.