PF-6689840 is a potent and selective Type II PTK6/Brk inhibitor with IC50 of 54 nM in biochemical assays; inhibits PTK6 phosphorylation at Y342 in engineered HET293T cells overexpressing PTK6 WT with IC50 of 0.25 uM; demonstrates superior kinase selectivity compared to the Type I inhibitors; inhibits tumor cell growth, which is independent of PTK6 expression levels in cells.