Abstract 3563: A highly selective Erk1/2 Inhibitor with in-vivo anti tumor potency

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Mutations in receptor tyrosine kinases, Ras or B-Raf frequently manifest constitutive activation of the Ras/Raf/Mek/Erk pathway in a variety of human cancers. The mitogen activated protein kinase Erk1/2 is an important regulator of cell proliferation and was shown to be over-activated by these dysregulated or mutated upstream signals. AEZS-131 selectively inhibits Erk1/2 with an IC50 of 4 nM, blocks cellular Rsk-1 phosphorylation, modulates downstream cellular substrate activation, arrests tumor cells in G1 and inhibits the growth of multiple human tumor cell lines in the nanomolar range. We have studied the response of human cancer cells (Hct116) in in-vivo mouse xenograft experiments. AEZS-131 significantly inhibited tumor growth at daily doses of 30mg/kg. Currently, AEZS-131 is undergoing in-vivo combination experiments with PI3K inhibitors. Since pharmacological inhibition of Erk1/2 reverses Ras and Raf activation also in cells demonstrating resistancy to common Raf inhibitors like GDC-0879 and PLX4720, it appears likely to put more attention on the downstream kinase Erk1/2 as therapeutic target. Furthermore, in instances of coincident activation of the Raf and PI3K pathways, combinations of AEZS-131 and PI3K inhibitors may prove efficacious. Here we present the in-vitro and in-vivo characterisation of the first in-class Erk1/2 inhibitor showing in-vivo efficacy as single therapy agent. Early development of the Erk1/2 inhibitor AEZS-131 by AEterna Zentaris is integral part of our in-house kinase research program comprising the investigation of different compounds for single Erk1/2 inhibition, single PI3K inhibition and dual kinase inhibitions. All compounds are exclusively synthesized by our Drug Discovery Department. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3563. doi:10.1158/1538-7445.AM2011-3563