INTRODUCTION: Rheumatoid arthritis (RA) is characterized by systemic synovitis 
causing joint destruction. With the development of biological disease-modifying 
anti-rheumatic drugs (bDMARDs) and combination of conventional DMARDs, clinical 
remission is perceived as an appropriate and realistic goal in many patients. 
However, bDMARDs require intravenous or subcutaneous injection and some patients 
fail to respond to bDMARDs or lose their primary response. Under the 
circumstances, targeted synthetic DMARDs (tsDMARDs), which are orally available 
low-molecular weight products, have been emerging. Five phase 3 trials of 
Baricitinib, a JAK1 and JAK2 inhibitor, have been performed and showed high 
clinical efficacy in patients with active RA and naïve to sDMARDs or an 
inadequate response to sDMARDs, MTX or bDMARDs. There was a favorable response 
for clinical and functional parameters in studies with placebo, MTX and 
adalimumab as comparator. It is also reported that safety was tolerable within 
the limited study period.
AREAS COVERED: We here review the recent progress in the development of 
baricitinib and its potential for the treatment of RA. Expert commentary: 
Although baricitinib is only one of the highly effective DMARDs that has a new 
mode of action, it will bring new concepts for rheumatology in the future.