Abstract A298: CHE202: A novel oral active microtubule depolymerizing vascular disrupting agent.
Authors: Högberg Marita , Rickardson Linda , Dahlstedt Emma , Gillner Mikael , Johansson Tommy , Romero Ivan , Smitt Olof 
Published: August 2014

Purpose: Microtubule targeting agents, represented by vinca alkaloids and taxanes, are extensively used in the clinic with good effects. However, these large molecules can only be administered by intravenous injections to the patient and they are also often substrates for Pgp efflux pumps which may lead to drug resistance and tumor progression. Thus, there is an unmet medical need for novel small molecule microtubule targeting agents with improved properties and less prone to development of tumor resistance than currently approved drugs.

Methods: Cell viability was measured with the fluorometric microculture cytotoxicity assay. Tubulin polymerization and colchicine displacement were performed in a cell free tubulin assay. For cell cycle experiments, apoptosis assays, and vascular disruption studies, a live cell imaging instrument were used. Human tumor xenografts of A2780 cells in NMRI nu/nu mice were used for in vivo efficacy studies.

Results: A series of small molecule compounds were synthesized and screened for cytotoxicity in a large panel of cancer cell lines as well as on normal cells. CHE202 was identified as one of the most potent compounds on a large number of cancer cell lines, with IC50-values in the low nM range (2 -12 nM), and significantly less cytotoxicity on normal cells. In the multidrug-resistant cell line A2780/Adr, CHE202 was shown to have similar IC50-values as in the parent cell line, indicating that CHE202 is not a substrate for P-glycoprotein-mediated drug efflux. Gene expression analysis in cells exposed to CHE compounds caused down regulation of tubulin genes and a similar gene-expression pattern as other tubulin-active compounds, indicating that CHE202 is a microtubule active compound. Further in vitro studies confirmed that CHE202 exert its cytotoxic activity through disruption of microtubule networks in living cells and inhibition of tubulin polymerization, causing G2/M arrest and cell death through apoptosis. Molecular modeling and a colchicine binding assay demonstrated that CHE202 binds to the colchicine-site of tubulin. In an angiogenesis assay, CHE202 was found to act as a vascular disrupting agent with activity in the sub-nM range on neo-angiogenesis and in the nM range on established blood vessels. In vivo efficacy studies, in an ovarian cancer xenograft model (A2780), showed that CHE202 administered by the oral route caused around 80% reduction of tumor volume, which was in the same range as the gold standard, paclitaxel.

Conclusions: CHE202 is an oral active novel microtubule targeting and vascular disrupting agent with nanomolar potency on several cancer cell lines, as well as on multidrug-resistant cancer cells. These results warrant further development of CHE202 towards the clinic.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A298.

Citation Format: Marita Högberg, Linda Rickardson, Emma Dahlstedt, Mikael Gillner, Tommy Johansson, Ivan Romero, Olof Smitt. CHE202: A novel oral active microtubule depolymerizing vascular disrupting agent. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A298.