ARQ 531 shows strong target inhibition in TMD8 cell line. The IC50 values are 0.85 nM and 0.39 nM for WT-BTK and C481S-BTK, respectively, in biochemical assay. Additionally, ARQ 531 also shows strong inhibition of TEK kinases with IC50s of 5.23 nM (BMX), 5.80 nM (TEC), 36.4 nM (TXK). The IC50s of ARQ 531 for SRC kinases are 3.86 nM (LCK), 4.22 nM (YES), 9.71 nM (BLK), 18.3 nM (HCK), 18.8 nM (LYNa), 25.9 nM (FGR), 32.2 nM (FYN), 48.0 nM (FRK) and for TRK kinases are 11.7 nM (TrkB), 13.1 nM (TrkA), 19.1 nM (TrkC). ARQ 531 inhibits proliferation of diverse types of cell lines (TMD8: GI50=0.13 μM, REC1: GI50=0.18 nM) and shows potency in cell lines that are addict to BCR, Src-family kinase and PI3K/AKT pathways.