TL-895 (previously M7583) is an orally administered, second-generation, irreversible inhibitor of Bruton’s tyrosine kinase (BTK; ref. 1) undergoing preclinical and early-stage clinical development for B-cell malignancies (2, 3), myelofibrosis (4–7), and systemic lupus erythematosus (8). Here, BTK is linked to systemic lupus erythematosus.