Lifirafenib (BGB-283)

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].

The number of cells seeded per well of a 96-well plate is optimized for each cell line to ensure logarithmic growth over the 3 days treatment period. Cells are left to attach for 16 hours and then treated with a 10-point dilution series in duplicate. Following a 3-day exposure to the compound, a volume of CellTiter-Glo reagent equal to the volume of cell culture medium present in each well is added. Mixture is mixed on an orbital shaker for 2 minutes to allow cell lysing, followed by 10 minutes incubation at room temperature to allow development and stabilization of luminescent signal. Luminescent signal is measured

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 potently inhibits MEK and ERK phosphorylation and DUSP6 expression in vivo when dosed repeatedly. There is no detectable difference on AKT phosphorylation^[1].