A BTK-activatable targeted covalent NIR fluorescent probe for kinase monitoring and B-cell lymphoma imaging

B-cell lymphoma is one of the most aggressive malignancies worldwide. Bruton's tyrosine kinase (BTK), a crucial mediator of B-cell receptor (BCR) signaling pathway, has emerged as a pivotal therapeutic target for B-cell lymphoma, so developing a molecular probe capable of quantitatively monitoring BTK expression and activity in live cells would be highly desirable for the early diagnosis and therapy of B-cell lymphoma. Here, we have constructed a BTK-activatable NIR fluorescent (NIRF) probe (Ibt-CyOH), which features a targeting ligand of ibrutinib as a recognition unit, a NIRF reporter, and an α-methylated acrylamide as a cleavable linker, triggered by nucleophilic addition-elimination reactions. Ibt-CyOH demonstrates high selectivity and inhibitory potency against BTK. A significant "turn-on" NIR fluorescence is generated upon the covalent binding of Ibt-CyOH to BTK, enabling real-time imaging of B-cell lymphoma cells as well as BTK inhibition in living mice. Our work establishes a promising targeted covalent activation strategy and provides a novel targeted covalent NIR probe for imaging of BTK in vivo, which will be beneficial to the diagnosis and treatment of B cell malignancies and will inspire the development of new NIRF probe in the future by redesigning the numerous targeted covalent drugs approved by FDA.