Abstract 1670: Discovery of novel water-soluble derivatives of mebendazole as selective CLK1/4 kinase inhibitors and their anticancer cancer activity

Abstract

Abstract Metastatic cancers remain clinically challenging and account for more than 90% of all cancer deaths. Drugs used to treat advanced metastatic cancers often generate drug resistance and relapse. Therefore, there is a critical need for novel therapeutic approaches for patients with advanced stage cancers that do not respond to any currently available anticancer therapies. Mebendazole and structurally related benzimidazole analogues, which are FDA approved compounds used to treat helminthic infections in the gastrointestinal track, are effective in inhibiting in vitro cancer cell proliferation. Unfortunately, their therapeutic applications in metastatic cancer are limited by their extremely low solubility and poor bioavailability. Further, the mechanism of the anticancer activities of this class of compounds is poorly defined. Here, we report the design and synthesis of water-soluble benzimidazoles as novel anticancer agents. Among them, the novel oxetanyl substituted compound, OBD9 (Methyl (5-(4-(methyl(oxetan-3-yl)amino)benzoyl)-1H-benzo[d]imidazol-2-yl)carbamate), demonstrated potent cytotoxicity towards a variety of highly aggressive cancer lines including prostate, lung, and ovarian cancers (IC50: 0.9-3.8 μM). In the NCI60 cancer cell panel screen, OBD9 broadly inhibited the proliferation of leukemia, melanoma, and breast and colon cancers. The aqueous solubility of OBD9 achieved 361 μM vs <1μM for mebendazole. In a mouse xenograft model of the highly metastatic human prostate cancer PC3MLN4, OBD9 (30 mg/kg/day, three times/week for two weeks) significantly inhibited the growth of established tumors (treatment-to-control ratio: 0.36) without noticeable toxicity. We performed broad kinase screening (KINOMEscan, DiscoverX) to explore the mechanism of action and discovered OBD9 as a potent and highly selective inhibitor of Cdc-like kinase 1 and 4 (CLK1 and 4). The Selectivity Score of OBD9 at 10 μM concentration in the 403 non-mutant kinases is 0.002; and its IC50 is 1.5 and 1.2 μM for CLK1 and CLK4, respectively. CLKs are nuclear serine/threonine (S/T) kinases that regulate gene splicing and are frequently over activated in cancers. Our results suggest that OBD9 impedes cancer growth at least in part by inhibiting CLK1/4. Citation Format: Lijun Sun, Jae Eun Cheong, Michela Zaffagni, Kun Zhou, Bruce Zetter. Discovery of novel water-soluble derivatives of mebendazole as selective CLK1/4 kinase inhibitors and their anticancer cancer activity [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 1670.