Combretazet-3 a novel synthetic cis-stable combretastatin-A4-azetidinone hybrid with enhanced stabilityand therapeutic efficacy in colon cancer

In recent years an extensive series of synthetic combretastatin A-4 (CA-4)-azetidinone (β-lactam) hybrids were designed and synthesised with a view to improve the stability, therapeutic efficacy and aqueous solubility of CA-4. Lead compounds containing a 3,4,5-trimethoxy aromatic ring at position 1 and a variety of substitution patterns at positions 3 and 4 of the β-lactam ring were screened in three adenocarcinoma-derived colon cancer cell lines (CT-26, Caco-2 and the CA-4 resistant cell line, HT-29). In both CT-26 and Caco-2 cells all β-lactam analogues analysed displayed potent therapeutic efficacy within the nanomolar range. Substitution of the ethylene bridge of CA-4 with the β-lactam ring together with the aforementioned aryl substitutions improved the therapeutic efficacy of CA-4 up to 300‑fold in the combretastatin refractory HT-29 cells. The lead compound combretazet-3 (CAZ-3); chemical name [4-(3-hydroxy-4-methoxyphenyl)-3-(4-hydroxyphenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one] demonstrated improved chemical stability together with enhanced therapeutic efficacy as compared with CA-4 whilst maintaining the natural biological properties of CA-4. Furthermore, CAZ-3 demonstrated significant tumour inhibition in a murine model of colon cancer. Our results suggest that combretastatin-azetidinone hybrids represent an effective novel therapy for the treatment of combretastatin resistant carcinomas

Synthesis, Evaluation and Structural Studies of Antiproliferative Tubulin-targeting Azetidin-2-ones

A series of azetidin-2-ones substituted at positions 2, 3 and 4 of the azetidinone ring scaffold were synthesised and evaluated for antiproliferative, cytotoxic and tubulin binding activity. In these compounds, the cis double bond of the vascular targeting agent combretastatin A-4 is replaced with the azetidinone ring in order to enhance the antiproliferative effects displayed by combretastatin A-4 and prevent the cis/trans isomerization that is associated with inactivation of combretastatin A-4. The series of azetidinones was synthetically accessible via the Staudinger and Reformatsky reactions. Of a diverse range of heterocyclic derivatives, 3-(2-thienyl) analogue 28 and 3-(3-thienyl) analogue 29 displayed the highest potency in human MCF-7 breast cancer cells with IC50 values of 7nM and 10nM respectively, comparable to combretastatin A-4. Compounds from this series also exhibited potent activity in MDA-MB-231 breast cancer cells and in the NCI60 cell line panel. No significant toxicity was observed in normal murine breast epithelial cells. The presence of larger, bulkier groups at the 3-position, for example 3-naphthyl derivative 21 and 3-benzothienyl derivative 26, resulted in relatively lower antiproliferative activity in the micromolar range. Tubulin-binding studies of 28 (IC50=1.37μM) confirmed that the molecular target of this series of compounds is tubulin. These novel 3-(thienyl) β-lactam antiproliferative agents are useful scaffolds for the development of tubulin-targeting drugs

Optimisation of estrogen receptor subtype-selectivity of a 4-Aryl-4H-chromene scaffold previously identified by virtual screening

4-Aryl-4H-Chromene derivatives have been previously shown to exhibit anti-proliferative, apoptotic and anti-angiogenic activity in a variety of tumor models in vitro and in vivo generally via activation of caspases through inhibition of tubulin polymerisation. We have previously identified by Virtual Screening (VS) a 4-aryl-4H-chromene scaffold, of which two examples were shown to bind Estrogen Receptor α and β with low nanomolar affinity and \u3c20-fold selectivity for α over β and low micromolar anti-proliferative activity in the MCF-7 cell line. Thus, using the 4-aryl-4H-chromene scaffold as a starting point, a series of compounds with a range of basic arylethers at C-4 and modifications at the C3-ester substituent of the benzopyran ring were synthesised, producing some potent ER antagonists in the MCF-7 cell line which were highly selective for ERα (compound 35; 350-fold selectivity) or ERβ (compound 42; 170-fold selectivity)

Synthesis and Evaluation of Azetidinone Analogues of Combretastatin A-4 as Tubulin Targeting Agents

The synthesis and antiproliferative activity of a new series of rigid analogues of combretastatin A-4 are described which contain the 1,4-diaryl-2-azetidinone (β-lactam) ring system in place of the usual ethylene bridge present in the natural combretastatin stilbene products. These novel compounds are also substituted at position 3 of the β-lactam ring with an aryl ring. A number of analogues showed potent nanomolar activity in human MCF-7 and MDA-MB-231 breast cancer cell lines, displayed in vitro inhibition of tubulin polymerization and did not cause significant cytotoxicity in normal murine breast epithelial cells. 4-(4-Methoxyaryl)-substituted compound 32, 4-(3-hydroxy-4-methoxyaryl)-substituted compounds 35 and 41 and the 3-(4-aminoaryl)-substituted compounds 46 and 47 displayed the most potent anti-proliferative activity of the series. β-Lactam 41 in particular showed sub-nanomolar activity in MCF-7 breast cancer cells (IC50 = 0.8 nM) together with significant in vitro inhibition of tubulin polymerization and has been selected for further biochemical assessment. These novel β-lactam compounds are identified as potentially useful scaffolds for the further development of antitumour agents which target tubulin

Occupational and Environmental Exposure of the Skin to Chemicals

Epoxy resin systems (ERS) are commercial thermosetting products used in many diverse applications due to their outstanding performance and resistance. The global epoxy resins market accounted for $7.9 billion in 2016 and is expected to reach$11.5 billion by 2022. Their usage is increasing despite widespread contact allergy to ERS. Epoxy chemicals are implicated in both occupational and non-occupational allergic contact dermatitis (ACD), with higher prevalence (11.7 ? 12.5%) in occupational settings. Workplace studies found exceptionally high rates of ACD from ERS in aircraft manufacturing workers, marble workers, painters, metalworkers and construction workers. Educational and protective measures are not always effective. We have taken an alternative, complimentary approach to reduce ACD to epoxy resins by modifying their chemical structures to control reactivity. It is a challenging task to reduce the adverse skin sensitizing effects of ERS while maintaining their excellent ability to form thermosetting polymers, as both of these properties are dependent on the inherent reactivity of the terminal epoxy groups. Focusing on the epoxy resin monomers DGEBA and DGEBF, we have designed compounds containing terminal epoxy groups with reduced reactivity by alteration of the total chemical structure. We have designed technically effective, less reactive epoxy resin monomers. Our alternative monomers were less sensitizing than DGEBA and DGEBF in vivo, as assessed by the LLNA, and showed little or no cross reactivity with DGEBA in a clinical study. We will present results from chemical design to in vitro and in vivo reactivity studies and clinical assessment

26th Annual GP2A Medicinal Chemistry Conference & 32nd Journ?es Franco-Belges de Pharmacochimie

The two nuclear estrogen receptors (ER? and ER?) mediate the biological effects of the estrogen hormones and ER? is an attractive therapeutic target for diseases including breast cancer and osteoporosis. Estrogens are known to have tissue selective effects, and there is considerable interest in the therapeutic use of selective estrogen receptor modulators (SERMs). ER? is an important target for drugs such as tamoxifen and fulvestrant. There is ongoing debate about the role of ER? in cancer. Three series of ER-ligands based on the benzoxepin scaffold structure were synthesized?series I containing an acrylic acid, series II with an acrylamide and series III with a saturated carboxylic acid substituent. These compounds were shown to be high affinity ligands for the ER with nanomolar IC50 binding values. Series I acrylic acid ligands were generally ER? selective. In particular, compound 13e featuring a phenylpenta-2,4-dienoic acid substituent was shown to be antiproliferative and downregulated ER? and ER? expression in MCF-7 breast cancer cells. Interestingly, from series III, the phenoxybutyric acid derivative compound 22 was not antiproliferative and selectively downregulated ER?. A docking study of the benzoxepin ligands was undertaken. Compound 13e is a promising lead for development as a clinically relevant SERD, whilst compound 22 will be a useful experimental probe for helping to elucidate the role of ER? in cancer cells

Synthesis, biochemical evaluation and structural studies of novel antiproliferative ?eta-lactams

THESIS 9398The synthesis and antiproliferative evaluation of anti-cancer ?-lactams targeting tubulin, heat shock protein 90 and the estrogen receptor is described. Compounds were planned to include relevant substituents known to confer target selectivity and included a diverse range in order to discern meaningful structure-activity relationships. The core ?-lactam heterocycle was formed using established chemistry - the Staudinger and Reformatsky reactions. The Staudinger reaction was employed for the majority of analogues as the necessary synthetic precursors were readily available. All products were fully characterised. A library of over 100 combretastatin A-4 analogues containing the ?-lactam core scaffold were prepared and evaluated for antiproliferative activity. Phenolic compound 181 was particularly potent, with activity in the picomolar range for a variety of cell types. Combretastatin A-4 is a known tubulin-targeting agent that binds at the colchicine-binding site, and selected ?-lactam analogues including 181 inhibited the polymerisation of tubulin at low micromolar concentrations