Abstract 2607: Antitumor activity of the selective RAF inhibitor HM95573 in solid tumors and hematologic malignancies

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA The mitogen-activated protein kinase (MAPK) pathway is particularly important for the survival and proliferation of tumor cells. Activation of the MAPK pathway due to mutations in BRAF, NRAS and KRAS is considered one of the causes of solid tumors (NSCLC, CRC,HCC, andthyroid cancers) and hematologic malignancies. HM95573 is a novel, highly potent RAF kinase inhibitor. Biochemically assayed for over 120 kinases, HM95573 showed the high selectivity toward BRAF mutant and CRAF kinases. The half maximal inhibition concentrations (IC50) of HM95573 against BRAFWT, BRAFV600E and CRAF kinases were 41nM, 7nM and 2nM, respectively. The strongly inhibited kinases subsequent to RAF kinases appeared to be CSF1R (44nM), DDR1 (77nM) and DDR2 (182 nM). HM95573 potently inhibited the growth of BRAFmutation CRC cell lines (e.g. IC50: 118nM for Colo-205) and thyroid cancer cell lines (43nM for B-CPAP); KRAS mutation NSCLC cell lines(297nM for Calu-6),CRC cell lines(65nM for HCT-116) and thyroid cancer cell lines(479nM for CAL-62); and NRAS mutation HCC cell lines(28nM for HepG2) andleukemia cell lines (39nM for HL-60). HM95573 effectively inhibited the phosphorylations of MEK and ERK, downstream kinases associated with cell proliferation in tumor cell lines mutated in BRAF, KRAS and NRAS. In addition, the phosphorylation of downstream kinases of RAF such as MEK and ERK was effectively inhibited with treatment of HM95573 in mutant KRAS NSCLC and CRC cells. HM95573 showed the excellent antitumor activity in mouse models xenografted with BRAF mutation cell line (Colo-205), KRAS mutation cell lines (Calu-6 and HCT-116)and NRAS mutation cell line (HepG2)two RAF inhibitors approved in melanoma which were effective to only BRAF mutation cell lines under conditions tested. The in vivo antitumor activity of HM95573 was potentiated with MEK inhibitors. Now, HM95573 is currently in phase I development in patients with advanced solid tumors including KRAS mutation NSCLC in Korea. Citation Format: Young-Mi Lee, InHwan Bae, Namgoong Gwang Mo, Jae Ho Lee, Suhyeon Kim, Ji Yeon Song, Kyu Hang Lee, Tae Hun Song, Young Gil Ahn, Young Hoon Kim, Kwee Hyun Suh. Antitumor activity of the selective RAF inhibitor HM95573 in solid tumors and hematologic malignancies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2607. doi:10.1158/1538-7445.AM2015-2607