The design, synthesis and biological evaluation of novel steroidal inhibitors of 17 β-Hydroxysteroid dehydrogenase type 1 which converts estrone into the highly potent estrogen, estradiol, is described. This isozyme has been implicated as a new drug target against hormone-dependent tumours which are stimulated by increased levels of estradiol.Initial targets were planned, around modifications of the steroidal estrone / estradiol core, utilising Mannich, Friedel-Crafts and amide coupling chemistry. When the biological activity of these compounds was evaluated in a cell-based 17β-HSD1 assay, significant inhibitory action was observed. The most potent compound was (13S)-3-hydroxy-13-methyl 2-(morpholinomethyl)-7,8,9,11,12,13,15,16-octahydro 6H-cyclopenta[a]-phenan-thren-17(14H)-one 128 with an IC50 of 723 nM, 128 was also shown to be selective for 17βSHD1 over 17β-HSD2 and does not display any cytotoxicity at 50 μM over a 96 hour period in estrogen receptor positive and estrogen receptor negative cells.A C16 extended linked and reverse amide series were synthesised, for which design was based upon STX1040 1 the most potent inhibitor in the literature. The most biologically active compound was N-(((13S,16R,17S)-2-ethyl 3,17-dihydroxy-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro 6H-cyclopenta[a]-phenan-thren-16-yl)methyl)-2-(pyridin-3-yl)acetamide 186 with a percentage inhibition of 81% at 10 μM. Similar biological activities were observed for the rest of this series, however these values are approximately 20% lower than those observed for STX1040 1.Quantities of H6-17β-HSD1 were successfully synthesised and purified for use in development of a novel MTS/PES recombinant protein assay, to assess the inhibitory potential of the novel steroidal compounds described and their modes of binding with the active site of 17β-HSD1. For these experiments it can be tentatively concluded that STX1040 1 acts a mixed site inhibitor for both the E2 and co-factor binding sites and the 2-substituted Mannich compound 127 acts as a competitive inhibitor for the E2 binding site and a non-competitive inhibitor for the co-factor binding site, however further experimentation is required to confirm these preliminary results.
|Date of Award||27 Jun 2012|
|Supervisor||Barry Potter (Supervisor)|