Bevacizumab plus fosbretabulin in recurrent ovarian cancer: Overall survival and exploratory analyses of a randomized phase II NRG oncology/gynecologic oncology group study

Design, Synthesis and Biological Investigation of 2-Anilino Triazolopyrimidines as Tubulin Polymerization Inhibitors with Anticancer Activities

A further investigation aiming to generate new potential antitumor agents led us to synthesize a new series of twenty-two compounds characterized by the presence of the 7-(3',4',5'-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine pharmacophore modified at its 2-position. Among the synthesized compounds, three were significantly more active than the others. These bore the substituents p-toluidino (3d), p-ethylanilino (3h) and 3',4'-dimethylanilino (3f), and these compounds had IC50 values of 30-43, 160-240 and 67-160 nM, respectively, on HeLa, A549 and HT-29 cancer cells. The p-toluidino derivative 3d was the most potent inhibitor of tubulin polymerization (IC50: 0.45 µM) and strongly inhibited the binding of colchicine to tubulin (72% inhibition), with antiproliferative activity superior to CA-4 against A549 and HeLa cancer cell lines. In vitro investigation showed that compound 3d was able to block treated cells in the G2/M phase of the cell cycle and to induce apoptosis following the intrinsic pathway, further confirmed by mitochondrial depolarization and caspase-9 activation. In vivo experiments conducted on the zebrafish model showed good activity of 3d in reducing the mass of a HeLa cell xenograft. These effects occurred at nontoxic concentrations to the animal, indicating that 3d merits further developmental studies.

Synthesis and Biological Evaluation of Highly Active 7-Anilino Triazolopyrimidines as Potent Antimicrotubule Agents

Two different series of fifty-two compounds, based on 3',4',5'-trimethoxyaniline (7a-ad) and variably substituted anilines (8a-v) at the 7-position of the 2-substituted-[1,2,4]triazolo [1,5-a]pyrimidine nucleus, had moderate to potent antiproliferative activity against A549, MDA-MB-231, HeLa, HT-29 and Jurkat cancer cell lines. All derivatives with a common 3-phenylpropylamino moiety at the 2-position of the triazolopyrimidine scaffold and different halogen-substituted anilines at its 7-position, corresponding to 4'-fluoroaniline (8q), 4'-fluoro-3'-chloroaniline (8r), 4'-chloroaniline (8s) and 4'-bromoaniline (8u), displayed the greatest antiproliferative activity with mean IC50's of 83, 101, 91 and 83 nM, respectively. These four compounds inhibited tubulin polymerization about 2-fold more potently than combretastatin A-4 (CA-4), and their activities as inhibitors of [3H]colchicine binding to tubulin were similar to that of CA-4. These data underlined that the 3',4',5'-trimethoxyanilino moiety at the 7-position of the [1,2,4]triazolo [1,5-a]pyrimidine system, which characterized compounds 7a-ad, was not essential for maintaining potent antiproliferative and antitubulin activities. Compounds 8q and 8r had high selectivity against cancer cells, and their interaction with tubulin led to the accumulation of HeLa cells in the G2/M phase of the cell cycle and to apoptotic cell death through the mitochondrial pathway. Finally, compound 8q significantly inhibited HeLa cell growth in zebrafish embryos.

Design, synthesis and biological evaluation of indole-based [1,2,4]triazolo[4,3-a] pyridine derivatives as novel microtubule polymerization inhibitors

A series of indole-based [1,2,4]triazolo [4,3-a]pyridine derivatives was designed and synthesized as novel microtubulin polymerization inhibitors by using a conformational restriction strategy. These compounds exhibited moderate to potent anti-proliferative activities against a panel of cancer cell lines (HeLa, A549, MCF-7 and HCT116). Among them, compound 12d featuring a N-methyl-5-indolyl substituent at the C-6 position of the [1,2,4]triazolo [4,3-a]pyridine core exhibited the highest antiproliferative activity with the IC₅₀ values ranging from 15 to 69 nM, and remarkable inhibitory effect on tubulin polymerization with an IC₅₀ value of 1.64 μM. Mechanistic studies revealed that compound 12d induced cellular apoptosis and cell cycle arrest at the G₂/M phase in a dose-dependent fashion. Moreover, compound 12d significantly suppressed wound closure and disturbed microtubule networks.

Non-Invasive Evaluation of Acute Effects of Tubulin Binding Agents: A Review of Imaging Vascular Disruption in Tumors

Tumor vasculature proliferates rapidly, generally lacks pericyte coverage, and is uniquely fragile making it an attractive therapeutic target. A subset of small-molecule tubulin binding agents cause disaggregation of the endothelial cytoskeleton leading to enhanced vascular permeability generating increased interstitial pressure. The resulting vascular collapse and ischemia cause downstream hypoxia, ultimately leading to cell death and necrosis. Thus, local damage generates massive amplification and tumor destruction. The tumor vasculature is readily accessed and potentially a common target irrespective of disease site in the body. Development of a therapeutic approach and particularly next generation agents benefits from effective non-invasive assays. Imaging technologies offer varying degrees of sophistication and ease of implementation. This review considers technological strengths and weaknesses with examples from our own laboratory. Methods reveal vascular extent and patency, as well as insights into tissue viability, proliferation and necrosis. Spatiotemporal resolution ranges from cellular microscopy to single slice tomography and full three-dimensional views of whole tumors and measurements can be sufficiently rapid to reveal acute changes or long-term outcomes. Since imaging is non-invasive, each tumor may serve as its own control making investigations particularly efficient and rigorous. The concept of tumor vascular disruption was proposed over 30 years ago and it remains an active area of research.