Abstract LB-266: Identification of novel checkpoint kinase inhibitor ASR352 with selective activity against 5-FU resistant colorectal cancer cells

Colorectal cancer (CRC) remains the third most common cancer in the United States, with a high mortality rate. More than 1.2 million new cases of CRC are diagnosed every year. Approximately 25% of these patients have metastatic lesions at diagnosis and almost 50% of these patients will eventually develop metastases. 5-Fluorouracil (5-FU) based cytotoxic chemotherapeutics such as FOLFOX and FOLFIRI have demonstrated improved response rates. 5-FU treatment induces DNA damage and stalling of DNA replication forks towards one sided double-strand breaks thus leading to apoptosis. However, these tumors quickly develop resistance to FOLFOX and FOLFIRI by stopping DNA damage process, and at the same time, this treatment regime leads to significant toxicity, cost, and patient inconvenience. To overcome the drug resistance developed in 5-FU based CRC chemotherapy, we looked for critical role of checkpoint kinase 1 (Chk1) that promotes DNA replication forks. Therefore, Chk1 kinase has been a target for developing mono or combination therapeutic agents. Recently, we demonstrated that an orphan azaadamantane molecule NSC30049 (NSC49L) is effective alone, and in combination potentiates 5-FU-mediated growth inhibition of CRC heterogeneous bulk and FOLFOX-resistant cell lines in culture with minimal effect on normal colonic epithelial cells. The pharmacokinetic analysis showed a higher bioavailability of this compound, however, with a short plasma half-life apparently due to reactive alkyl chloride group. To overcome this problem, we designed and synthesized several novel azaadamantane NSC49L analogs, and their cytotoxic efficacy against HCT116 and HT29 colorectal cancer cell lines was evaluated either alone or in combination with 5-FU with different concentrations for 48 h by MTT essay. ASR352 was identified as the best of all synthesized analogs. ASR352 was equally effective as NSC49L in (i) reducing the viability of 5-FU treated HCT116 and HT29 cell lines in a dose-dependent manner, (ii) inhibiting the FOLFOX-resistant HCT116 and HT29 cell lines, (iii) reducing the sphere formation capacity of CA2 cells, a CRC stem cell line, and (iv) causing the abrogation of 5-Fu induced G2/M and S phase arrests in HT29 cells. In addition,ASR352 inhibited the hydroxyurea (HU)-induced phosphorylation of Chk1 (P-Ser317), Chk1 (P-Ser345) and Chk1 (P-Ser296) in HT29 cell lines. In conclusion, a new clinical relevant drug-like molecule ASR352, that targets Chk1 pathway to reduce viability of particularly the 5-FU resistant CRC cells, has been identified. Citation Format: Srinivasa Ramisetti, Sangyub Kim, Deepkamal Karelia, Junxuan Lu, Shantu Amin, Satya Narayan, Arun K. Sharma. Identification of novel checkpoint kinase inhibitor ASR352 with selective activity against 5-FU resistant colorectal cancer cells [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 LB-266.