Luxeptinib interferes with LYN-mediated activation of SYK and modulates BCR signaling in lymphoma

What is it about?

Are you investigating a Bruton’s tyrosine kinase (BTK) inhibitor and interested where in the B-cell receptor (BCR) signaling cascade the kinase inhibitor targets? The BCR signaling pathway is complex and inhibiting kinases upstream of BTK may lead to inhibition of the BTK activity without inhibiting BTK directly. This study may be helpful as it disclosed how luxeptinib (a potent inhibitor of recombinant wild type and C481S mutant BTK at 8.4–27 nM and 2.5–13.1 nM respectively) modulates the earliest steps downstream of the BCR following its activation by anti-IgM in lymphoma cells. Luxeptinib has a strong affinity for BTK but the ability to reduce phosphorylation of kinases further upstream suggests that BTK is not the primary target. This study also provides insights into the kinases of the BCR signaling pathway that are targeted by ibrutinib (a FDA-approved BTK inhibitor) following its activation by anti-IgM in lymphoma cells.

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Why is it important?

The BCR signaling pathway plays a key role in B-cell development and aberrant activation of BCR signaling drives proliferation of B-cell leukemias and lymphomas and is a target for therapy. The importance of the BCR pathway is demonstrated by the fact that BTK inhibitors are highly effective in the treatment of mantle cell lymphoma, chronic lymphocytic leukemia/small lymphocytic leukemia, Waldenström’s macroglobulinemia and graft-versus-host disease. Inhibition of the BCR signaling pathway is also a promising therapeutic approach for ameliorating autoimmune and inflammatory complications as evidenced by recent studies. Multiple kinase inhibitors of BTK and BCR-signaling receptors are in development and understanding how and where these kinase inhibitors target in the complex BCR signaling cascade is important for successful drug development.