GP369 is a humanized FGFR2-IIIb specific antibody that markedly inhibits tumor cell proliferation. It significantly reduces the phosphorylation of FGFR2 and its downstream signaling pathways, making GP369 useful for research in cancers such as gastric and breast cancers.

GP369, at concentrations of 0.001-1000 nM over 2-5 days, effectively inhibits the proliferation of various cell types, such as FDCP-1, SUM52PE, and MCF7 cells. At 0.001-100 nM for 2 days, it suppresses FGFR2-IIIb-driven proliferation in FDCP-1 cells (IC 50 = 1.4 nM) without affecting FGFR2-IIIIc. Additionally, GP369 at 30 μg/mL for 3 days inhibits FGF7 (25 ng/mL) induced proliferation in MCF7 cells. At 10 μg/mL for 1-48 hours, it hinders FGFR2 and ERK1/2 phosphorylation and downstream signaling in Ba/F3 and SNU-16 cells.

GP369, administered intraperitoneally at doses of 2-20 mg/kg twice weekly for 43 days, significantly inhibited tumor growth in C.B-17 SCID mice with SNU-16 xenografts, while reducing FGFR2 phosphorylation and protein levels. Additionally, GP369 at 20 mg/kg twice weekly for 27 days achieved tumor stasis and significantly lowered FGFR2 phosphorylation and protein levels in NCr nude mice bearing MFM-223 xenografts.