In vitro activity: ELR-510444 is a novel and potent inhibitor of microtubule polymeirzation (also called microtubule disruptor or mitotic inhibitor) with potential antivascular effects and in vivo antitumor efficacy, it can cause a loss of cellular microtubules and the formation of aberrant mitotic spindles which lead to mitotic arrest and apoptosis of cancer cells. ELR510444 also shows potent antitumor activity in the MDA-MB-231 xenograft model with at least a 2-fold therapeutic window. Studies in tumor endothelial cells show that a low concentration of ELR510444 (30 nM) rapidly alters endothelial cell shape, similar to the effect of the vascular disrupting agent combretastatin A4.

Kinase Assay: ELR510444 has potent microtubule-disrupting activity, causing a loss of cellular microtubules and the formation of aberrant mitotic spindles and leading to mitotic arrest and apoptosis of cancer cells.

Cell Assay: ELR510444 potently inhibits cell proliferation with an IC(50) value of 30.9 nM in MDA-MB-231 cells, inhibits the rate and extent of purified tubulin assembly, and displaces colchicine from tubulin, indicating that the drug directly interacts with tubulin at the colchicine-binding site. ELR510444 is not a substrate for the P-glycoprotein drug transporter and retains activity in βIII-tubulin-overexpressing cell lines, suggesting that it circumvents both clinically relevant mechanisms of drug resistance to this class of agents.