Patient Disease Trajectories in Rheumatoid Arthritis Patients Treated with Baricitinib 4-mg in Four Phase 3 Clinical Studies.

Baricitinib is an oral agent widely approved for the treatment of moderately to severely active rheumatoid arthritis). Although baricitinib (and other agents) have demonstrated efficacy at the population level, treatment responses vary considerably between individual patients. This study assessed four baricitinib phase 3 clinical studies and categorized patient responses into response groups based on the Clinical Disease Activity Index (CDAI) using a growth mixture model. We then evaluated baseline characteristics and corresponding disease measures within the response groups. In patients with no prior treatment with biological disease-modifying anti-rheumatic drugs (bDMARDs), 65­71% of patients had rapid responses to treatment, while smaller groups had gradual (10­17%) or partial (18­22%) responses. In patients with prior bDMARD experience, rapid and partial responders each comprised 42% of patients while 15% had limited response. Gradual responders generally had higher baseline CDAI versus rapid responders, but achieved low disease activity (LDA) by 24, versus 12 weeks for rapid responders. Across response groups, patients who continued treatment generally maintained their response up to 52 weeks, and where joint erosion was assessed (in bDMARD-naïve patients), generally saw maintenance of joints during continued therapy. The identification of a gradual responder group, which demonstrated good response but required more time to achieve LDA, is relatively novel and should be considered when setting treatment expectations, particularly in patients with high baseline disease activity. In addition, in bDMARD-experienced patients, many patients did not achieve LDA but maintained a substantial partial response with continued therapy.