Buchner reported that R408, a SYK inhibitor, also has preferential in vitro anti-tumor activity in UM-CLL.[17] In contrast to these studies, only one recent report did not find a correlation between the extent of BCR inhibition and IGVH mutation status in ibrutinib-treated CLL patients.[10] The reason for this discrepant finding is unclear at the present time and warrants further investigation. This evidence concerns the gene BCR and B-cell chronic lymphocytic leukemia.