BRK/PTK6-IN-1 (Compound 51) is a potent and selective BRK inhibitor with an IC50 of 3.37 nM and Kd of 44 nM. It reduces MMP-9 protein expression and inhibits IGF-1-induced AKT phosphorylation in MDA-MB-231 cells. This compound significantly hinders migration, invasion, and colony formation without affecting cell proliferation and is commonly used in breast cancer and other cancer research.