Abstract 976: CUDC-101, a hybrid molecular targeted agent, reverses multiple mechanisms of drug resistance.

Abstract

Abstract CUDC-101, a hybrid molecular targeted agent, reverses multiple mechanisms of drug resistance CUDC-101 is a potent molecular targeted anticancer agent, rationally designed to simultaneously inhibit HDAC, EGFR and HER2. It exhibits potent antiproliferative and proapoptotic activities in both in vitro and in vivo assays and it is currently in Phase 1b clinical trial. Multidrug resistance (MDR) is a major unresolved obstacle to successful cancer chemotherapy. It is often associated with increased ABC transporters-mediated efflux of substrate anticancer drugs out of the cell. Platinum (Pt)-based anticancer drugs, exemplified by cisplatin and oxaliplatin, are the mainstay of treatment for most solid cancers. However, resistance to Pt anticancer drugs develops rapidly upon their administration, which can be caused by overexpression of MDR transporters and activated DNA repair mechanisms. We investigated the potentiation effect of CUDC-101 on the anticancer activity of conventional cytotoxic drugs in MDR cells with overexpression of various ABC transporters and in Pt-resistant cancer cells. CUDC-101 was found to increase the cytotoxicity and accumulation of substrate anticancer drugs in MPR-1 (doxorubicin) and MRP-2 (methotrexate) overexpressing cells, while no effect was observed in the parental sensitive cells. Mechanistically, CUDC-101 was found to inhibit MRP-1 and MRP-2 efflux function, probably by acting as an uncompetitive inhibitor and interfering with their ATPase activity. In Pt-resistant cancer cells, CUDC-101 appears to circumvent the resistance through inhibition of both MRP-2 and other DNA repair-mediated mechanisms. The combinations of CUDC-101 with cisplatin or oxaliplatin were found to display synergistic cytotoxic effect in cisplatin- or oxaliplatin-resistant cancer cell lines, respectively. Upon the concomitant administration of CUDC-101, cellular accumulation of Pt drugs and formation of DNA-Pt adducts were found to be increased whereas expression levels of DNA repair genes (e.g. ERCC1) was inhibited in Pt-resistant cells. The data advocates further development of CUDC-101 as a novel MDR reversal agent for use in combination cancer chemotherapeutic regimens. Citation Format: Kenneth K.W. To, Daniel C. Poon, XG Chen, Ge Lin, Li-wu Fu. CUDC-101, a hybrid molecular targeted agent, reverses multiple mechanisms of drug resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 976. doi:10.1158/1538-7445.AM2013-976