E7130 Derived From Total Synthesis Of Halichondrin As A Novel Tumor-Microenvironment Ameliorator

Background and objectives: Natural products have been a rich source of inspiration for drug discovery as demonstrated by the fact that over one-third of current therapeutic agents are natural products or compounds derived from them. Particularly, when the supply of a natural product from the natural source is limited, organic synthesis can offer a solution. However, with increasing structural complexity, this approach becomes exponentially more challenging, as a synthesis must meet various requirements, including high overall efficiency, scalability, cost-effectiveness, and product purity as well as conforming to good manufacturing practice (GMP) regulations. Despite the outstanding in vivo antitumor activity in mice, the limited supply from the natural sources has prevented drug development based on intact halichondrins. Methods: We successfully synthesized 19.5 g of C52-halichondrin-B alcohol with 99.84% purity via a total synthesis. From 15.0 g of this material, we obtained 11.5 g of C52-halichondrin-B amine (E7130) with 99.81% purity under GMP conditions. With totally synthetic E7130, a novel microtubule dynamics inhibitor, we studied the activities in both of in vitro and in vivo. The inhibitory activity of E7130 towards tubulin polymerization was analyzed in the cell-free system in which tubulin polymerization could be monitored by fluorescence enhancement due to the incorporation of a fluorescence reporter into the microtubules during polymerization. We analyzed in vivo antitumor activities using both a human cancer cell line orthotopic transplantation mouse model and subcutaneous xenograft models. The immunohistochemical analyses were performed with tumor tissues collected from mouse models to analyze histological changes after treatment with E7130. Results: E7130 is a novel microtubule dynamics inhibitor with exceedingly potent in vitro and in vivo anticancer activities. Significantly, E7130 not only is cytotoxic, but can also increase CD31-positive endothelial cells in tumors and reduce α-SMA-positive cancer-associated fibroblasts at pharmacologically relevant compound concentrations. Notably, this dual activity has been recognized for the first time through this study. According to these unique tumor microenvironment ameliorative effects, E7130 can augment the effect of other antitumor treatments in mouse models. In particular, a dose of 90 µg/kg, one-half of the maximum tolerated dose in mice, showed a prominent combinational effect with cetuximab, which suggests that E7130 has a different mechanism than other microtubule-targeted drugs. Conclusions: E7130 ameliorates the tumor microenvironment to improve cancer treatment when used in combination with other compounds. The data provide compelling evidence that E7130 is a promising molecular-targeting anticancer agent. Citation Format: Satoshi Kawano, Takanori Abe, Ken Ito, Kenzo Yahata, Kazunobu Kira, Tsuyoshi Akagi, Makoto Asano, Kentaro Iso, Yuki Sato, Fumiyoshi Matsuura, Isao Ohashi, Yasunobu Matsumoto, Minetaka Isomura, Takeo Sasaki, Takashi Fukuyama, Yusuke Miyashita, Yosuke Kaburagi, Akira Yokoi, Osamu Asano, Takashi Owa, Yoshito Kishi. E7130 derived from total synthesis of halichondrin as a novel tumor-microenvironment ameliorator [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4179.