Fabrice Jourdan

Structure-activity relationships of C-17 cyano-substituted estratrienes as anticancer agents

The synthesis, SAR, and preclinical evaluation of 17-cyanated 2-substituted estra-1,3,5(10)-trienes as anticancer agents are discussed. 2-Methoxy-17beta-cyanomethylestra-1,3,5(10)-trien-3-ol ( 14), but not the related 2-ethyl derivative 7, and the related 3- O-sulfamates 8 and 15 display potent antiproliferative effects (MCF-7 GI 50 300, 60 and 70 nM, respectively) against human cancer cells in vitro. Investigation of the SAR reveals that a sterically unhindered hydrogen bond acceptor attached to C-17 is most likely key to the enhanced activity. Compound 8 displayed significant in vitro antiangiogenic activity, and its ability to act as a microtubule disruptor was confirmed. Inhibitory activity of the sulfamate derivatives against steroid sulfatase and carbonic anhydrase II (hCAII) was also observed, and the interaction between 15 and hCAII was investigated by protein crystallography. The potential of these multimechanism anticancer agents was confirmed in vivo, with promising activity observed for both 14 and 15 in an athymic nude mouse MDA-MB-231 human breast cancer xenograft model.

Synthesis, Antitubulin, and Antiproliferative SAR of Analogues of 2-Methoxyestradiol-3,17-O,O-bis-sulfamate

The synthesis and antiproliferative activity of analogues of estradiol 3,17-O,O-bis-sulfamates (E2bisMATEs) are discussed. Modifications of the C-17 substituent reveal that an H-bond acceptor is essential for high antiproliferative activity. The local environment in which this H-bond acceptor lies can be varied to an extent. The C-17-oxygen linker can be deleted or substituted with an electronically neutral methylene group, and replacement of the terminal NH(2) with a methyl group is also acceptable. Mesylates 10 and 14 prove equipotent to the E2bisMATEs 2 and 3, while sulfones 20 and 35 display enhanced in vitro antiproliferative activity. In addition, the SAR of 2-substituted estradiol-3-O-sulfamate derivatives as inhibitors of tubulin polymerization has been established for the first time. These agents inhibit the binding of radiolabeled colchicine to tubulin.

Effects of C-17 heterocyclic substituents on the anticancer activity of 2-ethylestra-1,3,5(10)-triene-3-O-sulfamates: synthesis, in vitro evaluation and computational modelling.

The potent activity of 2-substituted estra-1,3,5(10)-triene-3-O-sulfamates against the proliferation of cancer cells in vitro and tumours in vivo highlights the therapeutic potential of such compounds. Optimal activity is derived from a combination of a 2-XMe group (where X = CH(2), O or S), a 3-O-sulfamate group in the steroidal A-ring and a H-bond acceptor around C-17 of the D-ring. Herein, we describe the synthesis and anti-proliferative activities of a series of novel 2-substituted estra-1,3,5(10)-triene-3-O-sulfamates bearing heterocyclic substituents (oxazole, tetrazole, triazole) tethered to C-17. In vitro evaluation of these molecules revealed that high anti-proliferative activity in breast and prostate cancer cells lines (GI(50) of 340-850 nM) could be retained when the heterocyclic substituent possesses H-bond acceptor properties. A good correlation between the calculated electron density of the heterocyclic ring and anti-proliferative activity was observed. Docking of the most active compounds into their putative site of action, the colchicine binding site of tubulin, suggests that they bind through a different mode to the previously described bis-sulfamate derivatives and 1 and 2, which possess similar in vitro activity.

Chimeric microtubule disruptors

A chimeric approach is used to discover microtubule disruptors with excellent in vitro activity and oral bioavailability; a ligand-protein interaction with carbonic anhydrase that enhances bioavailability is characterised by protein X-ray crystallography. Dosing of a representative chimera in a tumour xenograft model confirms the excellent therapeutic potential of the class.

Structure–Activity Relationships of C-17-Substituted Estratriene-3-O-sulfamates as Anticancer Agents

The synthesis and antiproliferative activities of analogues of 2-substituted estradiol-3,17-O,O-bis-sulfamates (E2bisMATEs) are discussed. Modifications of the C-17 substituent confirm that an H-bond acceptor is essential for high activity; its optimal linkage to C-17 and the local environment in which it resides are defined. In the non-sulfamoylated series 17β-acyl substitution delivers 48b, the most potent compound identified to date. In the sulfamate series a number of permutations of linker and H-bond acceptor deliver excellent activity, with 55, 61, 65, 49a, and 49b proving especially promising. The in vivo potential of these compounds was explored in the NCI hollow fiber assay and also in a mouse Matrigel model of antiangiogenesis in which 49 and 55 show significant inhibitory activity.

Quinazolinone-Based Anticancer Agents: Synthesis, Antiproliferative SAR, Antitubulin Activity, and Tubulin Co-crystal Structure

Quinazolinone-based anticancer agents were designed, decorated with functional groups from a 2-methoxyestradiol-based microtubule disruptor series, incorporating the aryl sulfamate motif of steroid sulfatase (STS) inhibitors. The steroidal AB-ring system was mimicked, favoring conformations with an N-2 substituent occupying D-ring space. Evaluation against breast and prostate tumor cell lines identified 7b with DU-145 antiproliferative activity (GI50 300 nM). A preliminary structure-activity relationship afforded compounds (e.g., 7j GI50 50 nM) with activity exceeding that of the parent. Both 7b and 7j inhibit tubulin assembly in vitro and colchicine binding, and 7j was successfully co-crystallized with the αβ-tubulin heterodimer as the first of its class, its sulfamate group interacting positively at the colchicine binding site. Microtubule destabilization by 7j is likely achieved by preventing the curved-to-straight conformational transition in αβ-tubulin. Quinazolinone sulfamates surprisingly showed weak STS inhibition. Preliminary in vivo studies in a multiple myeloma xenograft model for 7b showed oral activity, confirming the promise of this template.

Synthesis, antitubulin, and antiproliferative SAR of C3/C1-substituted tetrahydroisoquinolines.

The syntheses and antiproliferative activities of novel substituted tetrahydroisoquinoline derivatives and their sulfamates are discussed. Biasing of conformational populations through substitution on the tetrahydroisoquinoline core at C1 and C3 has a profound effect on the antiproliferative activity against various cancer cell lines. The C3 methyl‐substituted sulfamate (±)‐7‐methoxy‐2‐(3‐methoxybenzyl)‐3‐methyl‐6‐sulfamoyloxy‐1,2,3,4‐tetrahydroisoquinoline (6 b), for example, was found to be ∼10‐fold more potent than the corresponding non‐methylated compound 7‐methoxy‐2‐(3‐methoxybenzyl)‐6‐sulfamoyloxy‐1,2,3,4‐tetrahydroisoquinoline (4 b) against DU‐145 prostate cancer cells (GI50 values: 220 nM and 2.1 μM, respectively). Such compounds were also found to be active against a drug‐resistant MCF breast cancer cell line. The position and nature of substitution of the N‐benzyl group in the C3‐substituted series was found to have a significant effect on activity. Whereas C1 methylation has little effect on activity, introduction of C1 phenyl and C3‐gem‐dimethyl substituents greatly decreases antiproliferative activity. The ability of these compounds to inhibit microtubule polymerisation and to bind tubulin in a competitive manner versus colchicine confirms the mechanism of action. The therapeutic potential of a representative compound was confirmed in an in vivo multiple myeloma xenograft study.

In vivo and in vitro properties of STX2484: a novel non-steroidal anti-cancer compound active in taxane-resistant breast cancer.

Background:STX2484 is a novel non-steroidal compound with potent anti-proliferative activity. These studies aimed to identify STX2484’s mechanism of action, in vivo efficacy and activity in taxane-resistant breast cancer models.Methods:Effects of STX2484 and paclitaxel on proliferation, cell cycle and apoptosis were assessed in vitro in drug-resistant (MCF-7DOX) and non-resistant cells (MCF-7WT). STX2484 efficacy in βIII tubulin overexpression in MCF-7 cells was also determined. Anti-angiogenic activity was quantified in vitro by a co-culture model and in vivo using a Matrigel plug assay. An MDA-MB-231 xenograft model was used to determine STX2484 efficacy in vivo.Results:STX2484 is a tubulin disruptor, which induces p53 expression, Bcl2 phosphorylation, caspase-3 cleavage, cell cycle arrest and apoptosis. In addition, STX2484 is a potent anti-angiogenic agent in vitro and in vivo. In breast cancer xenografts, STX2484 (20 mg kg−1 p.o.) suppressed tumour growth by 84% after 35 days of daily dosing, with limited toxicity. In contrast to paclitaxel, STX2484 efficacy was unchanged in two clinically relevant drug-resistant models.Conclusions:STX2484 is an orally bioavailable microtubule-disrupting agent with in vivo anti-angiogenic activity and excellent in vivo efficacy with no apparent toxicity. Crucially, STX2484 has superior efficacy to paclitaxel in models of clinical drug resistance.

Optimisation of tetrahydroisoquinoline-based chimeric microtubule disruptors.

Tetrahydroisoquinoline (THIQ)‐based “chimeric” microtubule disruptors were optimised through modification of the N‐benzyl motif, in concert with changes at C3 and C7, resulting in the identification of compounds with improved in vitro antiproliferative activities (e.g. 15: GI50 20 nM in DU‐145). The broad anticancer activity of these novel structures was confirmed in the NCI 60‐cell line assay, with 12 e,f displaying MGM values in the 40 nM region. In addition, their profiles as inhibitors of tubulin polymerisation and colchicine binding to tubulin were confirmed. Compound 15, for example, inhibited tubulin polymerisation with an IC50 of 1.8 μM, close to that of the clinical drug combretastatin A‐4, and also proved effective at blocking colchicine binding. Additionally, compound 20 b was identified as the only phenol in the series to date showing both better in vitro antiproliferative properties than its corresponding sulfamate and excellent antitubulin data (IC50=1.6 μM). Compound 12 f was selected for in vivo evaluation at the NCI in the hollow fibre assay and showed very good activity and wide tissue distribution, illustrating the value of this template for further development.

Tetrahydroisoquinolinone-Based Steroidomimetic and Chimeric Microtubule Disruptors

A structure–activity relationship (SAR) translation strategy was used for the discovery of tetrahydroisoquinoline (THIQ)‐based steroidomimetic and chimeric microtubule disruptors based upon a steroidal starting point. A steroid A,B‐ring‐mimicking THIQ core was connected to methoxyaryl D‐ring ring mimics through methylene, carbonyl and sulfonyl linkers to afford a number of steroidomimetic hits (e.g., 7‐methoxy‐2‐(3‐ methoxybenzyl)‐6‐sulfamoyloxy‐1,2,3,4‐tetrahydroisoquinoline (20 c) GI50=2.1 μM). Optimisation and control experiments demonstrate the complementary SAR of this series and the steroid derivatives that inspired its design. Linkage of the THIQ‐based A,B‐mimic with the trimethoxyaryl motif prevalent in colchicine site binding microtubule disruptors delivered a series of chimeric molecules whose activity (GI50=40 nM) surpasses that of the parent steroid derivatives. Validation of this strategy was obtained from the excellent oral activity of 7‐methoxy‐6‐sulfamoyloxy‐2‐(3,4,5‐trimethoxybenzyl)‐1,2,3,4‐tetrahydroisoquinoline (20 z) relative to a benchmark steroidal bis‐ sulfamate in an in vivo model of multiple myeloma.