Abstract 3117: Eribulin is a novel TERT-targeting inhibitor that penetrates into intracerebrally grown glioblastomas and suppresses their growth in mice

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Abstract [Introduction] No effective molecular targeting therapy has been clinically developed for patients with glioblastoma (GBM) despite of intense genome analysis. Approximately 60-80% of GBM harbor mutations in the promoter region of TERT that leads to its upregulation, making it the most common single genetic abnormalities in GBM. TERT, a reverse-transcriptase subunit of telomerase, has been an attractive candidate for therapy target because of their observed upregulation in a wide variety of cancers, including GBMs, a phenomenon that presumably helps maintain telomeres for their indefinite proliferation. It has been reported recently that TERT has an RNA-dependent RNA polymerase (RdRP) activity, with which TERT is involved in maintenance of stem cell phenotype and mitotic progression. We have previously identified eribulin as a specific inhibitor of RdRP activity of TERT through drug screening and shown that eribulin suppressed growth of ovarian cancers with high TERT expression. In order to investigate an efficacy of eribulin as a novel TERT-targeted therapy against GBM, we investigated the antitumor effect of eribulin in cultured cell and brain tumor model using GBM cell lines. [Methods] The TERT promoter status was examined in 20 glioma cell lines. Seven cell lines were subjected to in vitro cytotoxicity assay. U87MG was either subcutaneously or intracranially transplanted in athymic mice. Tissue or plasma concentration of eribulin was measured by LC-MS/MS. [Results] All GBM cell lines tested that harbored TERT promoter mutations including U87MG, U251MG, U118MG as well as several patient-derived glioblastoma sphere culture cells were highly sensitive to eribulin, IC50 below 1nM. Intraperitoneal administration of eribulin completely suppressed the growth of U87MG subcutaneous tumor in nude mice, and the RdRP activities in treated tumors were significantly decreased in a dose-dependent manner. In the brain tumor model, a high concentration of eribulin was detected in the brain tumor tissues as early as 15 minutes after intravenous injection of eribulin, which remained stable even 24 hours later when the plasma concentration of eribulin became undetectable. Finally, intraperitoneal administration of eribulin significantly prolonged the survival of mice with intracerebrally transplanted U87MG xenograft (p<0.001). [Conclusion] Our results showed that eribulin efficiently transfers into brain tumor tissues and has a strong antitumor effect against GBM cells through inhibition of RdRP activity. Eribulin thus appears to be a promising novel TERT-targeting therapeutic agent against GBM. A clinical trial is being scheduled. Citation Format: Masamichi Takahashi, Shunichiro Miki, Yuko Matsushita, Kohei Fukuoka, Yoshiko Maida, Mami Yasukawa, Mitsuhiro Hayashi, Akinobu Hamada, Akitake Mukasa, Ryo Nishikawa, Kenji Tamura, Yoshitaka Narita, Kenkichi Masutomi, Koichi Ichimura. Eribulin is a novel TERT-targeting inhibitor that penetrates into intracerebrally grown glioblastomas and suppresses their growth in mice [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 3117. doi:10.1158/1538-7445.AM2017-3117