Increased incidence of AF in ibrutinib-treated patients has been associated with not only with inhibition of C-terminal Src kinase (Xiao et al., 2020), but also with downregulation of phosphoinositide 3-kinase (PI3K)-Akt pathway (McMullen et al., 2014; Jiang et al., 2019). The gene discussed is CSK; the disease is atrial fibrillation.