LAUSR

One of the most significant challenges in creating more potent, less toxic treatments for patients is to identify new cancer therapeutic targets that distinguish the malignant from normal cells. EWS-FLI1 is a well-established Ewing sarcoma (ES) oncogene that has the potential to be an ideal therapeutic target by directly impacting malignant cells. We have previously reported the discovery and characterization of YK-4-279, an enantiomer-specific inhibitor of EWS-FLI1, which has been demonstrated to induce apoptosis, inhibit EWS-FLI1 transcription, block RNA helicase A co-immunoprecipitation with EWS-FLI1, and result in alternative splicing to mimic EWS-FLI1 knockdown. Continuous efforts in structure-guided medicinal chemistry has yielded TK-216, an analog of YK-4-279 inhibitor of EWS-FLI1, which is 3-4 fold more potent with excellent drug-like properties. TK-216 potently inhibits the proliferation of ES cells. Induces apoptosis in a dose -dependent manner as measured by caspase-3 activity in multiple ES cell lines with distinct translocation variants. The effects of TK-216 on alternative splicing (AS) were further validated using genes including ARID1A, CLK1, CASP3, PPFIBP1 and RUNX2. The splicing pattern was similar between TK-216 and YK-4-279. In addition to the in vitro activity of TK-216 , we show that TK-216 displays anti-tumor activity in a number of ES xenograft models. In summary, TK-216, a novel, first-in-class therapeutic which directly inhibits EWS-FLI1, offers a promising approach for the treatment of Ewing Sarcoma and is currently in Phase 1 clinical trials in patients with relapsed or refractory Ewing Sarcoma (clinicaltrials.gov - NCT02657005). Citation Format: Saravana P. Selvanathan, Eric Moseley, Garrett T. Graham, Katti Jessen, Brian Lannutti, Aykut Uren, Jeffrey A. Toretsky. TK-216: a novel, first-in-class, small molecule inhibitor of EWS-FLI1 in early clinical development, for the treatment of Ewing Sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 694. doi:10.1158/1538-7445.AM2017-694