Introduction: We sought to identify and compare treatment response groups based on individual patient responses (rather than group mean response) over time on the Clinical Disease Activity Index (CDAI) for rheumatoid arthritis (RA), in patients treated with baricitinib 4-mg in 4 phase 3 studies.
Methods: Trajectory subgroups were identified within each study using growth mixture modeling. Following grouping, baseline characteristics and disease measures were summarized and compared.
Results: In each study, three response trajectories were identified. In the three studies of patients naïve to biological disease-modifying anti-rheumatic drugs (bDMARDs) patients had, on average, high disease activity, as measured by CDAI. In these studies, a group of rapid responders (65-71% of patients) had the lowest baseline CDAI scores and achieved mean CDAI ≤ 10 by week 16. Gradual responders (10-17%) had higher baseline CDAI, but generally achieved low disease activity (CDAI ≤ 10) by week 24. A group of partial responders (18-22%) had higher baseline CDAI and did not achieve mean CDAI ≤ 10. In bDMARD-experienced patients, the subgroups were rapid responders, who achieved mean CDAI ≤ 10 (42% of patients); partial responders, with mean CDAI decrease of ~ 15 points from baseline (42% of patients); and limited responders (15% of patients). Changes in modified total sharp score (mTSS; assessed only in biologic-naïve patients) were below the smallest detectable difference at 24/52 weeks for > 90% of patients in each group, excepting partial responders in RA-BEGIN (≥ 75% no detectable change).
Conclusion: In patients receiving baricitinib 4-mg, lower baseline CDAI was generally associated with rapid response, while higher baseline CDAI scores were generally seen for patients who either reached treatment targets more gradually, or who had a partial or limited response. Maintenance of response was observed with continued baricitinib treatment in all response groups and generally included maintenance of mTSS.
Keywords: Baricitinib; Growth mixture modeling; Rheumatoid arthritis; Trajectory.
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), 65–71% of patients had rapid responses to treatment, while smaller groups had gradual (10–17%) or partial (18–22%) 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.
© 2022. The Author(s).