AXL and breast cancer: On the other hand, R428 had proven to be a selective Axl kinase inhibitor (Holland et al., 2010), with the inhibition constant in the nanomolar (nM) range (Myers et al., 2016), as well as the blocker of other Axl-associated events such as autophosphorylation, metastasis development in breast cancer and proinflammatory cytokine production (Holland et al., 2010).