Bruton's tyrosine kinase is a possible therapeutic target in microscopic polyangiitis.

"Declarations Ethics approval and consent to participateExperiments using human materials were permitted by the Ethical Committee of the Faculty of Health Sciences, Hokkaido University (permission no. 20–40) and performed in accordance with the Declaration of Helsinki. After obtaining written informed consent, peripheral blood (10 ml) was drawn from healthy volunteers. Experiments using rats were permitted by the Animal Experiments Committee of Hokkaido University (permission no. 20–0032) and performed in accordance with the Guidelines for the Care and Use of Laboratory Animals at Hokkaido University. Consent for publicationNot applicable. Competing interestsY.A., S.H., and H.F. are employees of Ono Pharmaceutical Corp. Ltd. Y.N., S.M., and A.I. were given research funding by Ono Pharmaceutical Corp. Ltd. Competing interests Y.A., S.H., and H.F. are employees of Ono Pharmaceutical Corp. Ltd. Y.N., S.M., and A.I. were given research funding by Ono Pharmaceutical Corp. Ltd."

"Funding This work was supported by the Japanese Grant-in-Aid for Scientific Research (no. 21H0295802)."