Growing evidence of the safety of JAK inhibitors in patients with rheumatoid arthritis.

To facitinib and baricitinib are two of the currently available Janus kinase (JAK) inhibitors for the treatment of patients with RA. Randomized controlled trials have shown that these JAK inhibitors are as efficacious as biological DMARDs. Safety profiles of these JAK inhibitors in randomized controlled trials and their long-term extension studies have been demonstrated; however, real world evidence remains to be established to bridge the gap between randomized controlled trials and rheumatology clinics. Fundamentally, no difference in the screening, prevention, and monitoring of infections between JAK inhibitors and biological DMARDs exists. However, increased risk of herpes zoster is probably common to all JAK inhibitors. No indication of increased risk for malignancy in patients with RA treated with JAK inhibitors has been reported. To evaluate risks of relatively rare serious adverse events such as thromboembolic events, gastrointestinal perforation, and interstitial lung disease in clinical settings, accumulation of cases with these events are needed. Continuous pharmacovigilance activity is absolutely warranted to establish the safety of JAK inhibitors in patients with RA and other rheumatic diseases.