Many breast turnouts are hortrione-responsive and rely on estrogens for their sustained growth and development. The enzyme 17 beta-hydroxysteroid dehydrogenase type 1 (17 beta-HSD1) is primarily responsible for the conversion of estrone (EI) into the most potent of the human estrogens 17 beta-estradiol (E2). Here we report the syntheses, inhibitory activities and docking studies for a novel series of pyrazole amides which have been discovered with the aim of probing the structure activity relationships (SAR) for such a template and of using this template to mimic the potent inhibitor 1 (Fig. 1). Amides containing an aromatic pyridyl moiety have been found to give the best inhibition, indicating that the pyridyl group interacts beneficially in the active site. This work has shown that extension from this position on the pyrazole template is well tolerated and the optimization of such systems is under investigation. (c) 2005 Elsevier Ireland Ltd. All rights reserved.