Filgotinib in rheumatoid arthritis

IntroductionRheumatoid Arthritis (RA) remains a challenge for rheumatologists and patients despite implementation of intensive treat-to-target strategies in shared decision with patients and an increasing availability of drugs. Janus kinase inhibitors (JAKi) are a new generation of oral targeted drugs. Filgotinib preferentially inhibits JAK1 and is the latest JAKi to be approved for use in RA.Areas coveredThis narrative review focuses on drug characteristics, efficacy, and safety of filgotinib in patients with RA, summarizing available literature. Trial data are detailed, put into perspective for practice and discussed in regulatory perspective.Expert opinionPreclinical studies demonstrate preferential inhibition of JAK1 and a promising pharmacokinetic profile with few drug-drug interactions. Increase in hemoglobin in line with preferential inhibition of JAK1 over JAK2 is seen in early-phase clinical trials. A phase III program demonstrates efficacy in several disease stages, numerically higher with 200 mg versus 100 mg daily. In the overall RA population such dose-related effect is not observed for safety except for herpes zoster and increases in lipids and creatine phosphokinase. This reassuring safety profile is to be confirmed in future practice. It also needs to be unraveled if JAK1 preferential inhibition plays a key role in this safety profile.