Rapid Onset of Efficacy of Baricitinib in Chinese Patients with Moderate to Severe Rheumatoid Arthritis: Results from Study RA-BALANCE

Introduction Baricitinib is an oral, selective inhibitor of Janus kinase which demonstrates clinical efficacy in patients with rheumatoid arthritis (RA). This report aims to analyze the onset time of baricitinib in Chinese patients with moderately to severely active RA who had an inadequate response to methotrexate. Methods This post hoc analysis evaluated clinical improvements of Chinese patients treated with baricitinib 4 mg once daily compared with placebo, based on data from a phase 3 study RA-BALANCE. Efficacy measures including American College of Rheumatology 20% (ACR20) response, ACR core set values, Disease Activity Score modified to include the 28 diarthrodial joint count (DAS28) using high-sensitivity C-reactive protein (hsCRP), DAS28-erythrocyte sedimentation rate, Simplified Disease Activity Index, Clinical Disease Activity Index, DAS28-hsCRP ≤ 3.2 response (low disease activity), and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) were evaluated at weeks 1, 2, 4, 8, 12, 14, 16, 20, and 24 (except for FACIT-F evaluated every 4 weeks). A logistic regression model and an analysis of covariance model were used to analyze treatment comparisons of categorical and continuous measures, respectively. Results Statistically significant ( p ≤ 0.05) improvements were observed as early as week 1 or 2 for the baricitinib group compared to placebo in almost all main efficacy measures. For other outcomes including 66 swollen joint count, 68 tender joint count, FACIT-F, and DAS28-hsCRP ≤ 3.2 response rate, differences were evident ( p ≤ 0.05) by week 4 in the baricitinib group compared with placebo. Significant improvements in all efficacy measures were sustained through 24 weeks. Conclusions Baricitinib demonstrated a rapid onset of efficacy on ACR20 response, ACR core set values, disease activity, and patient-reported outcome improvements in Chinese patients from RA-BALANCE. Trial Registration ClinicalTrials.gov identifier, NCT02265705.