Lifirafenib (BGB-283, Beigene-283) potently inhibits RAF family kinases and EGFR activities in biochemical assays with IC50 values of 23, 29 and 495 nM for the recombinant BRAFV600E kinase domain, EGFR and EGFR T790M/L858R mutant.
In vitro, BGB-283 potently inhibits BRAFV600E-activated ERK phosphorylation and cell proliferation. It demonstrates selective cytotoxicity and preferentially inhibits proliferation of cancer cells harboring BRAFV600E and EGFR mutation/amplification. In BRAFV600E colorectal cancer cell lines, BGB-283 effectively inhibits the reactivation of EGFR and EGFR-mediated cell proliferation. It demonstrates selective cytotoxicity to cell lines harboring BRAFV600E or EGFR mutations. BGB-283 inhibits the EGF-induced EGFR autophosphorylation on Tyr1068 in A431 cells in a dose-dependent manner. In WiDr colorectal cancer cells, BGB-283 is shown to be able to inhibit the feedback activation of EGFR signaling and achieves sustained inhibition of pERK[1].
In vivo, BGB-283 treatment leads to dose-dependent tumor growth inhibition accompanied by partial and complete tumor regressions in both cell line-derived and primary human colorectal tumor xenografts bearing BRAFV600E mutation. BGB-283 is highly efficacious in BRAF(V600E) colorectal cancer xenograft models, including HT29, Colo205, and two primary tumor xenografts harboring BRAFV600E mutation. In addition, BGB-283 shows compelling efficacy in a WiDr xenograft model where EGFR reactivation is shown to be induced upon BRAF inhibition. BGB-283 induces tumor regression in HCC827 but not in A431 xenograft. BGB-283 inhibits phosphorylation of both ERK1/2 and EGFR and displays potent antitumor activity in WiDr tumor xenografts. BGB-283 does not induce EGFR feedback activation as reported for vemurafenib. BGB-283 potently inhibits MEK and ERK phosphorylation and DUSP6 expression in vivo when dosed repeatedly. There is no detectable difference on AKT phosphorylation[1].
[1] Tang Z, et al. Mol Cancer Ther. 2015, 14(10):2187-97.