Abstract 3782: Development of a dual inhibitor of pan-RAF and VEGFR2 for the treatment of metastatic colorectal cancer with mutant K-RAS
Authors: Hong Sungpyo , Choi Young-Il , Choi Jihye , Kim Wonyoung , Kwon Ho-Seok , Park Yong Bin , Ki Min-Hyo , Shin Hee Jong , Lee Michael , Ahn Soon Kil 
Published: July 2016

Signal transduction in the RAS-RAF-MEK-ERK (MAPK) pathway plays a key role in cell survival, growth and proliferation. The pathway is controlled by extracellular signals through receptor tyrosine kinases (RTK) and is activated by oncogenic mutations in many types of cancer. K-RAS mutation has been reported in 40% of colorectal cancer patients. These patients have acquired resistance to EGFR tyrosine kinase inhibitors. Therefore, there is a need for the development of new therapeutic approaches for the treatment of these cancers. The B-RAF selective inhibitors have been approved for the treatment of human melanoma with a B-RAF V600E mutation. However, B-RAF specific inhibitor activates C-RAF in RAS mutant cells by inducing RAF dimer formation and paradoxical activation of C-RAF. These observations require the development of pan-RAF inhibitors without inducing paradoxical activation. In addition, as VEGFR2 represents one crucial promoter of tumor angiogenesis in colorectal cancer, the inhibition of VEGFR2 has been expected to be synergistic for the treatment of colorectal cancer.

Therefore, we tried to find dual inhibitors of pan-RAF and VEGFR2 using structure based molecular modeling and identified a selective inhibitor, C1005, which binds to the DFG-out inactive conformation of B-RAF. In addition, C1005 potentially inhibited B-RAF, C-RAF, B-RAF V600E and VEGFR2 with IC50 value of 2.7 nM, 0.7 nM, 5.2 nM and 11nM, respectively. C1005 completely inhibited the phosphorylation of MEK-ERK without paradoxical activation in K-RAS mutant cells compared with Vemurafenib and Regorafenib. We examined the effects of C1005 on cell proliferation of colorectal cancer cells with K-RAS or B-RAF mutation. C1005 displayed potent anti-proliferative activities not only in K-RAS mutant colorectal cancer cells but also in B-RAF mutant colorectal cancer cells. C1005 effectively blocked cell proliferation of HCT-116, LS-513 and WiDr at EC50 of 145 nM, 79 nM and 636 nM, respectively. In addition, growth inhibition of VEGF-stimulated HUVEC indicates that C1005 is a potent inhibitor of the angiogenesis. To study in vivo effect, we tested C1005 in colorectal cancer xenografts with mutant K-RAS. Oral treatment of animals bearing xenograft tumors by 30 and 60 mg/kg, twice daily (BID) of C1005, induced a dose-dependent tumor growth inhibition. We observed 77% and 89% reduction of tumor volume, respectively.

In this study, we discovered an orally active dual inhibitor of pan-RAF and VEGFR2. C1005 has been shown to suppress mutant K-RAS colorectal cancer cells without activating the MAPK pathway. Our findings suggest that C1005 could be an excellent preclinical candidate to treat mutant K-RAS driven colorectal cancer.

Citation Format: Sungpyo Hong, Young-Il Choi, Jihye Choi, Wonyoung Kim, Ho-Seok Kwon, Yong Bin Park, Min-Hyo Ki, Hee Jong Shin, Michael Lee, Soon Kil Ahn. Development of a dual inhibitor of pan-RAF and VEGFR2 for the treatment of metastatic colorectal cancer with mutant K-RAS. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3782.