AAK1 and rheumatoid arthritis: Baricitinib activity demonstrated affinity against AAK1 (8.2 nM), BIKE (20 nM), and GAK (120 nM; Fig 2A and B); these values are within the exposure range of the approved 2 mg (US, EU) and 4 mg (EU) once‐daily doses of baricitinib for the treatment of RA (Shi et al, 2014).