The tetrahydroisoquinoline (THIQ) core structure is explored as a steroidomimetic nucleus with attractive pharmaceutical properties. A library was synthesised employing Pomeranz-Fritsch, Pictet-Spengler, Bischler-Napieralski strategies yielding 77 final targets, substituted at every position, for biological evaluation. Complementary strategies overcame synthetic difficulties, sometimes yielding two products in a single cyclisation. Three compounds were initially tested against a panel of 19 nuclear receptors (NRs) and exhibited broad substitution-dependent activity. 2-(4-Chlorophenyl)-1-isopropyl-1,2,3,4-tetrahydroisoquinolin-6-ol fully inhibited every NR at 100 µM, confirming the THIQ as a lead for optimisation. Compounds were evaluated for cytotoxicity against 60 cell lines by the NCI (USA), exhibiting moderate to insignificant cytotoxicity. Three compounds showed ca. 30-90% of average growth inhibition and were selected for a five dose test. Off-target evaluation highlighted compounds with activity against glucagon-like peptide 1 secretion, calcitonin gene-related peptide receptor antagonism and with >100% inhibition against the metabotropic glutamate receptor 2. Estrogen receptor-related receptor α (ERRα), a constitutively active orphan NR, is a hormone-dependent cancer target and diethylstilboestrol (DES), a known inverse agonist, possesses similarities to THIQs. THIQs tested against ERRα revealed no general SAR rules, but showed a lower degree of efficacy in a commercial TR-FRET assay, with 1-benzyl-2-(4-chlorophenyl)-4-methyl-1,2,3,4-tetrahydroisoquinolin-6-ol showing 79% efficacy at 100 µM as an inverse agonist, being more active than DES (64% at 100 µM). Inhibition of steroidogenic enzymes like 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) is an emerging approach for the treatment of HDBC, compared to other current clinical strategies. THIQs evaluated against 17β-HSD1 showed good activity in both whole cell and cell lysate assays, with the best inhibitor, 2-(4-chlorophenyl)-4-isopropyl-1,2,3,4-tetrahydroisoquinolin-6-ol, possessing an IC50 value of 336 nM. The value of THIQ as a drug-like steroidomimetic scaffold is thus established and this work reveals straightforward strategies to optimise potency and selectivity for a range of potential targets by structural and stereochemical iteration.
|Date of Award||5 Feb 2014|
|Supervisor||Barry Potter (Supervisor) & Mathew Leese (Supervisor)|
- 17 beta-HSD1
- estrogen receptor related receptor alpha