A concise synthesis of pyrazole analogues of combretastatin A1 as potent anti-tubulin agents

Our plain-English summary of A concise synthesis of pyrazole analogues of combretastatin A1 as potent anti-tubulin agents, by R. Zaninetti, S.V. Cortese, S. Aprile, et al (ChemMedChem, 2013).

The study

• Authors: R. Zaninetti, S.V. Cortese, S. Aprile, A. Massarotti, P.L. Canonico, G. Sorba, G. Grosa, A.A. Genazzani, T. Pirali
• Journal: ChemMedChem
• Published: 2013;8(4):633-43
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Combretastatin A1 (CA1) binds to the β-subunit at the colchicine binding site of tubulin and inhibits polymerization. As such, it is both an antitumor agent and a vascular disrupting agent. It has been shown to be at least tenfold more potent than combretastatin A4 (CA4) in terms of vascular shutdown, which correlates with its metabolism to reactive ortho-quinone species that are assumed to be directly cytotoxic in tumor cells. A series of 3,4-diarylpyrazoles were concisely synthesized, one of which, 3-methoxy-6-[4-(3,4,5-trimethoxyphenyl)-1H-pyrazol-3-yl]benzene-1,2-diol (27), proved to be a cytotoxic anti-tubulin agent with low nanomolar potency. We also report that combretastatins, including CA1, CA4, and 27, are effective against mesothelioma cell lines and therefore have significant clinical promise. Metabolism experiments demonstrate that 27 retains the ability to form ortho-quinone species, while the pyrazole ring shows high metabolic stability, suggesting that this compound might result in better pharmacokinetic profiles than CA1, with similar pharmacodynamic properties and clinical potential.

Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In plain English

This laboratory chemistry and cell-culture study did not involve people or asbestos exposure. The authors made new pyrazole and isoxazole versions of combretastatin A1 (CA1), a tubulin-blocking drug, and tested them on laboratory-grown cancer cells. IC50 measures potency in a cell-viability (MTT) test; lower means more potent. In human neuroblastoma cells, the IC50 was 2.6 nM for CA4 and 1.3 nM for CA1. The strongest new pyrazole compounds, 27 and 15, had IC50 values of 5.4 and 12.0 nM. CA4, CA1, 15 and 27 were also tested on two mesothelioma lines: REN (epithelioid malignant pleural mesothelioma) and MSTO-211H (biphasic). IC50 values ranged from 1.2 to 21.0 nM. In the MSTO-211H line, only about 40% of cells were sensitive, even at the higher concentrations tested. In rat and human liver fraction tests, compound 27 formed ortho-quinone species; its pyrazole ring was not metabolically changed. The authors concluded that combretastatins are active in mesothelioma cells and that their observations would support clinical trials in this tumor type. They added that compound 27 might have better pharmacokinetic profiles than CA1.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory chemistry study: new compounds were synthesized and tested on cancer cell lines in vitro. The authors also ran in vitro metabolism tests with rat and human liver fractions and computer docking (molecular modeling).
• Who was studied: Cell lines, not people: the human neuroblastoma line SH-SY5Y, and two mesothelioma lines. REN is an epithelioid malignant pleural mesothelioma line. MSTO-211H was established from the pleural effusion of a patient with biphasic mesothelioma.
• Exposure: No asbestos exposure was studied. Cells were treated with combretastatin A4 (CA4, compound 1), combretastatin A1 (CA1, compound 3), and newly synthesized pyrazole and isoxazole analogues of CA1 (including compounds 15, 27, 30 and 31).
• Main results:
  • IC50 values were derived from MTT cell-viability dose-response curves fitted with GraphPad Prism software.
  • In SH-SY5Y neuroblastoma cells, the IC50 for cytotoxicity was 2.6 plus or minus 1.1 nM for CA4 and 1.3 plus or minus 1.2 nM for CA1.
  • In SH-SY5Y neuroblastoma cells, the IC50 was 5.4 plus or minus 1.1 nM for new compound 27 and 12.0 plus or minus 1.0 nM for new compound 15.
  • In neuroblastoma cells, compounds 15 and 27 were as effective as CA1 at increasing the share of cells arrested in the G2/M phase of the cell cycle.
  • No activity was observed for the N-methylated analogue of 27 (compound 30).
  • IC50 values in REN mesothelioma cells were 3.1 nM for CA4, 1.4 nM for CA1, 19.3 nM for 15 and 10.5 nM for 27. In MSTO-211H mesothelioma cells they were 2.7, 1.2, 21.0 and 5.4 nM respectively (each with plus-or-minus values).
  • The authors reported that the epithelioid line (REN) was more sensitive. In the MSTO-211H line, only about 40% of cells were sensitive to the compounds, even at the higher concentrations tested.
  • In rat and human liver fraction incubations, compounds 27 and 31 formed ortho-quinone species, identified through their GSH adducts.
  • The pyrazole and isoxazole rings were not metabolically transformed.
• The authors' conclusion: The authors concluded that combretastatins are active in mesothelioma cells and that their observations would support a combretastatin analogue being tested in clinical trials for this tumor type. They also suggested that compound 27's metabolic stability might result in better pharmacokinetic profiles than CA1, with similar pharmacodynamic profiles.
• Limitations the authors state:
  • The docking scores from the computer modeling did not correlate with the measured IC50 values.
  • The main characterization of the compounds was carried out in neuroblastoma cells, with mesothelioma cells tested in addition.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma.

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