B cell signalling pathways—New targets for precision medicine in chronic lymphocytic leukaemia

The B cell receptor (BCR) is a master regulator of B cells, controlling cellular processes such as proliferation, migration and survival. Cell signalling downstream of the BCR is aberrantly activated in the B cell malignancy chronic lymphocytic leukaemia (CLL), supporting the pathophysiology of the disease. This insight has led to development and approval of small molecule inhibitors that target components of the BCR pathway. These advances have greatly improved the management of CLL, but the disease remains incurable. This may partly be explained by the inter‐patient heterogeneity of the disease, also when it comes to treatment responses. Precision medicine is therefore required to optimize treatment and move towards a cure. Here, we discuss how the introduction of BCR signalling inhibitors has facilitated the development of functional in vitro assays to guide clinical treatment decisions on use of the same therapeutic agents in individual patients. The cellular responses to these agents can be analysed in high‐throughput assays such as dynamic BH3 profiling, phospho flow experiments and drug sensitivity screens to identify predictive biomarkers. This progress exemplifies the positive synergy between basal and translational research needed to optimize patient care.