A JAK Inhibitor for Treatment of Rheumatoid Arthritis: The Baricitinib Experience

Baricitinib, an oral selective Janus kinase (JAK)1/JAK2 inhibitor, is approved as monotherapy or in combination with methotrexate for treating adults with moderate-to-severe active rheumatoid arthritis (RA) and provides improvements in clinical signs, symptoms and patient-reported outcomes. Currently, baricitinib is approved for treating RA in more than 75 countries. In several pivotal Phase II and III RA trials (RA-BALANCE, RA-BEGIN, RA-BEAM, RA-BUILD, RA-BEACON, RA-BEYOND), up to seven years of baricitinib treatment was well tolerated and provided rapid and sustained efficacy, which was confirmed in real-world settings. Safety signals for another JAK inhibitor, tofacitinib, have emerged, as observed in the post-marketing Phase IIIb/IV trial Oral Rheumatoid Arthritis Trial (ORAL) Surveillance; safety signals were subsequently highlighted in a retrospective study of baricitinib and consequently new recommendations and warnings and precautions for all JAK inhibitors have been issued. Ongoing studies to further characterise and clarify the benefit:risk of JAK inhibitors include registries and controlled trials. This capstone review summarises clinical and real-world data outlining the benefit:risk profile of baricitinib, confirming that the improved disease activity and physical function of patients with RA treated with this JAK inhibitor observed in clinical trials is translated into effectiveness in clinical practice, with a low rate of discontinuations.