As efficacy and safety data emerge, differences between JAK inhibitor subclasses are appearing. JAK1 selective drugs, upadacitinib and filgotinib, have broadly come with the same overarching safety recommendations as other immunosuppressive drugs for RA: caution is needed regarding infection risk; monitoring for laboratory abnormalities, including lipids and muscle enzymes, is indicated. A distinguishing feature of JAK inhibitors is a risk for zoster reactivation. Numerically, overall rates of serious infection are similar among JAK inhibitor classes. There are currently no signals for diverticular perforation. VTE incidence rates were similar across comparator groups for the JAK1 selective agents. These observations are not yet conclusive evidence for different safety profiles between JAK1 selective agents and other JAK inhibitors. Differences in study population, design, and concomitant steroid use are examples of potential confounders. It is too early to draw conclusions on long-term outcomes such as malignancy and cardiovascular risk. Post-marketing pharmacovigilance studies will be essential.
Keywords: JAK inhibitor; pharmacovigilance; rheumatoid arthritis; safety; trials; zoster.
© The Author(s) 2021. Published by Oxford University Press on behalf of the British Society for Rheumatology.