BACKGROUND: Baricitinib is an oral, reversible, selective Janus kinase 1 and 2 
inhibitor.
METHODS: In this phase III, double-blind 24-week study, 684 biologic 
disease-modifying antirheumatic drug (DMARD)-naïve patients with rheumatoid 
arthritis and inadequate response or intolerance to ≥1 conventional synthetic 
DMARDs were randomly assigned 1:1:1 to placebo or baricitinib (2 or 4 mg) once 
daily, stratified by region and the presence of joint erosions. Endpoint 
measures included American College of Rheumatology 20% response (ACR20, primary 
endpoint), Disease Activity Score (DAS28) and Simplified Disease Activity Index 
(SDAI) score ≤3.3.
RESULTS: More patients achieved ACR20 response at week 12 with baricitinib 4 mg 
than with placebo (62% vs 39%, p≤0.001). Compared with placebo, statistically 
significant improvements in DAS28, SDAI remission, Health Assessment 
Questionnaire-Disability Index, morning joint stiffness, worst joint pain and 
worst tiredness were observed. In a supportive analysis, radiographic 
progression of structural joint damage at week 24 was reduced with baricitinib 
versus placebo. Rates of adverse events during the treatment period and serious 
adverse events (SAEs), including serious infections, were similar among groups 
(SAEs: 5% for baricitinib 4 mg and placebo). One patient had an adverse event of 
tuberculosis (baricitinib 4 mg); one patient had an adverse event of 
non-melanoma skin cancer (baricitinib 4 mg). Two deaths and three major adverse 
cardiovascular events occurred (placebo). Baricitinib was associated with a 
decrease in neutrophils and increases in low-density and high-density 
lipoprotein.
CONCLUSIONS: In patients with rheumatoid arthritis and an inadequate response or 
intolerance to conventional synthetic DMARDs, baricitinib was associated with 
clinical improvement and inhibition of progression of radiographic joint damage.
TRIAL REGISTRATION NUMBER: NCT01721057; Results.