Abstract DDT02-05: eFT226: A selective and highly potent inhibitor of eukaryotic initiation factor 4A (eIF4A), a novel approach for the treatment of cancer

Abstract eFT226: A Selective and Highly Potent Inhibitor of Eukaryotic Initiation Factor 4A (eIF4A), a Novel Approach for the Treatment of Cancer Siegfried H Reich, Peggy A Thompson, Justin T Ernst, Boreth Eam, Nathan P Young, Sarah Fish, Joan Chen, Maria Barrera, Haleigh Howard, Ana Parra, Eric Sung, Jocelyn Staunton, Ivy NJ Hung, Gregory S Parker, Gary G Chiang, Christopher J Wegerski, Andres Nevarez, Jeff Clarine, Samuel Sperry, Alan Xiang, Chinh Tran, Christian Nilewski, Garrick K Packard, Theodore Michels, Paul A Sprengeler, and Kevin R Webster Effector Therapeutics, San Diego, CA Oncoprotein expression is tightly controlled at the level of RNA translation which is largely regulated by the eukaryotic translation initiation factor 4F (eIF4F). eIF4A1, a component of the eIF4F complex, catalyzes the ATP dependent unwinding of RNA duplexes and facilitates 43S ribosome complex scanning within the 5'-untranslated region (UTR). eIF4A1 is required for efficient translation of key oncogenes that contain complex secondary structures within the 5'-UTR. eFT226 is a novel, potent and selective eIF4A small molecule inhibitor with excellent physicochemical and pharmaceutical properties. The design of eFT226 involved ab initio ligand-based methods coupled with small molecule crystal structure analysis. eFT226 inhibits eIF4A1 through a reversible sequence-selective enhancement of eIF4A1 binding to mRNA with specific polypurine motifs within the 5'-UTR. The formation of a stable ternary complex [eIF4A1/eFT226/mRNA] with specific sequence recognition motifs leads to a block in ribosome scanning of select mRNAs. Treatment of lymphoma, AML, breast, colorectal, lung and hepatocellular tumor cell lines with eFT226 led to a dose dependent translational down regulation (IC50 of ~5-20 nM) of key oncogenes that drive tumor cell survival and proliferation (i.e., c-MYC, CCND1, BCL2 and MCL-1). Oncogene down regulation results in potent inhibition of cellular proliferation (GI50 of ~2-30 nM) across a panel of tumor cell lines. Enhanced anti-tumor sensitivity and a rapid induction of apoptosis was observed in hematological cell lines including lymphoma and AML. Inhibition of tumor cell proliferation and survival with eFT226 treatment results in significant antitumor activity in vivo in multiple human tumor models of DLBCL, Burkitt's lymphoma, acute myeloid leukemia (AML), and solid tumors following ≤ 1 mg/kg/week IV administration. eFT226 regulates the protein expression of multiple metabolic markers (i.e. c-MYC, HK2, TXNIP and GLUT1) that result in inhibition of tumor glucose uptake supporting the use of 18F-FDG-PET imaging as a measure of eFT226 target engagement in the clinic. These data demonstrate that eFT226 is a sequence-selective translational repressor of key oncogenic drivers that are essential for tumor cell proliferation and survival and support the clinical development of eFT226 in cancer patients. Citation Format: Siegfried H. Reich, Peggy A. Thompson, Justin T. Ernst, Boreth Eam, Nathan P. Young, Sarah Fish, Joan Chen, Maria Barrera, Haleigh Howard, Ana Parra, Eric Sung, Jocelyn Staunton, Ivy Nj Hung, Gregory S. Parker, Gary G. Chiang, Christopher J. Wegerski, Andres Nevarez, Jeff Clarine, Samuel Sperry, Alan Xiang, Chinh Tran, Christian Nilewski, Garrick K. Packard, Theodore Michels, Paul A. Sprengeler, Kevin R. Webster. eFT226: A selective and highly potent inhibitor of eukaryotic initiation factor 4A (eIF4A), a novel approach for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr DDT02-05.