In patients who experienced interruption of baricitinib during these studies, the most frequent AEs that occurred during the first 4 weeks on treatment included upper respiratory tract infection (URTI) (4.7% of patients who experienced an interruption), headache (4.1%), blood creatine phosphokinase (CPK) increased (3.1%), diarrhea (2.8%), nausea (2.5%), and bronchitis (2.5%) (Table 3). This evidence concerns the gene PIK3C2A and bronchitis.