Ibrutinib inhibits BLK phosphorylation. CLL cells were treated with 1 μM ibrutinib or acalabrutinib for 1 hour before lysing, and BLK, phosphorylated BLK, and GAPDH levels were measured by western blotting. Numbers below each band indicate fold change vs the vehicle control, normalized by GAPDH. Figure shows 2 representative patient samples of 3 studied.