Inhibitors of Bruton’s tyrosine kinase interfere with neutrophil functions in vitro

Abstract Multiple sclerosis (MS) is a neurodegenerative, autoimmune disease that is still incurable. Nowadays, a variety of new drugs are being developed to prevent excessive inflammation and halt neurodegeneration. Among these are the inhibitors of Bruton’s tyrosine kinase (BTK). As this enzyme is indispensable for B cells, it is an appealing therapeutic target for autoimmune diseases. Recognizing the emerging importance of BTK in myeloid cells, we investigated the impact of upcoming BTK inhibitors on neutrophil functions. Although adaptive immunity in MS has been thoroughly studied, unanswered questions about the pathogenesis can be addressed by studying the effects of candidate MS drugs on innate immune cells such as neutrophils, previously overlooked in the MS landscape. In this study, we used three BTK inhibitors (evobrutinib, fenebrutinib and tolebrutinib), currently in phase III clinical trials for MS, and found that they reduce neutrophil activation by the bacterial peptide N-formylmethionyl-leucyl-phenylalanine and the chemokine interleukin 8/CXCL8. Furthermore, they diminished the production of reactive oxygen species and release of neutrophil extracellular traps. Additionally, the production of CXCL8 and interleukin-1β by neutrophils in response to inflammatory stimuli decreased. Inhibitory effects were not related to toxicity. In fact, BTK inhibitors prolonged neutrophil survival in an inflammatory environment. Finally, migration of neutrophils treated with BTK inhibitors towards CXCL8 was decreased in a Boyden chamber assay, whereas transendothelial migration was unaffected. Collectively, this study provides novel insights into the impact of BTK inhibitors on neutrophil functions, thereby holding important implications for autoimmune or hematological diseases where BTK is crucial.