Beside Btk, the direct inhibitory activity of IQS019 towards Syk and/or Lyn phosphorylation may also explain the capacity of the compound to activate apoptosis in vitro and in vivo, as pharmacological inhibition of Syk, has been reported to elicit the apoptotic cascade in preclinical models of DLBCL and CLL [35, 36]. Here, SYK is linked to B-cell chronic lymphocytic leukemia.