Improved synthesis of EM-1745, preparation of its C17-ketone analogue and comparison of their inhibitory potency on 17β-hydroxysteroid dehydrogenase type 1

Abstract

Endocrine therapies are widely used for the treatment of estrogen-sensitive diseases. 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) is involved in the last step of the biosynthesis of potent estrogen estradiol (E₂). This enzyme catalyzes the reduction of the C17-ketosteroid estrone (E₁) into the C17β-hydroxy steroid E₂ using the cofactor NAD(P)H. The X-ray analysis of E₂/adenosine bisubstrate inhibitor EM-1745 proven that this compound interacts with both the substrate- and the cofactor-binding sites. However, E₁ is a better substrate of 17β-HSD1 than E₂. Thus, in order to improve the inhibitory potency of EM-1745, the C17-ketone analogue was prepared. During this work, a new and more efficient method for synthesizing EM-1745 was developed using an esterification and a cross-metathesis as key steps. Contrary to what was expected, the C17-ketone analogue of EM-1745 is a less potent inhibitor (IC₅₀ = 12 nM) than the C17-alcohol (IC₅₀ = 4 nM) in homogenated HEK-293 cells overexpressing 17β-HSD1. Our results contribute to the knowledge of an unexpected observation: the C17-ketone steroidal inhibitors of 17β-HSD1 are less potent than their corresponding C17-alcohol derivatives.

Keywords::

• 17β-Hydroxysteroid dehydrogenase
• enzyme
• inhibitor
• steroid
• chemical synthesis
• cross-metathesis

Acknowledgements

We thank the Canadian Institutes of Health Research for financial support (DP) and a scholarship (MB). We are also grateful to Dr. Van Luu-The for providing HEK-293 cells everexpressing 17β-HSD1 and Fatima Kamal for chemical synthesis of intermediate compound 6. Careful reading of the manuscript by Sylvie Méthot is also greatly appreciated.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.