Erosion regression in patients with rheumatoid arthritis after upadacitinib-a pilot study using high resolution peripheral quantitative computed tomography.

Objectives: To evaluate whether inhibition of Janus kinases (JAK) 1 could lead to erosion repair on high-resolution peripheral quantitative computer tomography (HR-pQCT) in patients with active rheumatoid arthritis (RA).

Methods: This was a prospective, non-randomized pilot study. We enrolled 20 adult patients with active RA with ≥1 bone erosion on HR-pQCT. They were given upadacitinib 15 mg once daily for 24 weeks. HR-pQCT of the metacarpophalangeal joint was performed at baseline and 24-week. The serum bone biomarkers level was evaluated before and after treatment. Twenty age-and-sex matched RA patients from another study treated with conventional synthetic disease modifying anti-rheumatic drugs (csDMARDs) were included as active controls.

Results: Nineteen patients in the upadacitinib group completed the study procedures. After 24 weeks, despite similar improvement in disease activity, a reversed trend in the mean erosion volume change on HR-pQCT was observed comparing the upadacitinib and active control group (upadacitinib group: -0.23 ± 3.26mm3 vs control group: 1.32 ± 6.05mm3, p= 0.131). A greater proportion of erosions in the upadacitinib group demonstrated regression (27% vs 12%, p= 0.085). Using general estimating equation (GEE), the use of upadacitinib was significantly associated with erosion regression (OR: 3.61, 95% CI: 1.00-13.00, p= 0.049) after adjusting for the difference in disease duration. The serum levels of bone resorption markers reduced after upadacitinib treatment. No new safety signal was noted.

Conclusion: Despite a similar improvement in RA disease activity after upadacitinib compared with csDMARDs, a differential regression of erosion on HR-pQCT was observed in patients received upadacitinib. The potential role of JAK1 inhibition in erosion repair should be investigated.