LAUSR

TRK receptor tyrosine kinases are expressed as fusion proteins encoded by various fusion genes across a wide variety of cancer types, including lung and colorectal cancer. These fusion proteins have potent oncogenic activity and are thought to be an attractive therapeutic target. In a kinase inhibitor screening we identified CH7057288, a potent and selective TRK inhibitor belonging to a novel chemical class. Our inhibitor showed selective inhibitory activity against TRKA, TRKB, and TRKC in cell-free kinase assays and suppressed proliferation of TRK fusion-positive cell lines, but not that of TRK-negative cell lines. In subcutaneously implanted xenograft models of TRK fusion-positive cells, strong tumor growth inhibition was observed. Furthermore, CH7057288 induced regression of intracranial tumors and greatly improved event-free survival in an intracranial implantation model mimicking brain metastasis. Recently, resistant mutations in TRK have been reported in patients showing disease progression after treatment with a TRK inhibitor under clinical development. Our compound maintained similar levels of in vitro and in vivo activity against some of the resistant mutants as it did to wild-type TRK. In summary, CH7057288 could be a promising therapeutic agent for TRK fusion-positive cancer. Citation Format: Hiroshi Tanaka, Hitoshi Sase, Toshiyuki Tsukaguchi, Hiromi Tanimura, Masami Hasegawa, Kiyoshi Hasegawa, Yoshiyuki Ono, Nobuhiro Oikawa, Hiroshi Sakamoto, Toshiyuki Mio. Potent and selective TRK inhibitor CH7057288 [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 4179. doi:10.1158/1538-7445.AM2017-4179