The Uncoupling of Disease Activity from Joint Structural Progression in Patients with Rheumatoid Arthritis Treated with Filgotinib

Introduction: While modern treatments can prevent progressive bone destruction in patients with rheumatoid arthritis (RA) achieving clinical remission, it is unclear whether residual clinical activity may cause or be associated with progressive joint damage. This post hoc analysis evaluated the association between clinical disease activity and structural progression in patients with RA treated with filgotinib (FIL) in FINCH 1 (NCT02889796).

Methods: Patients with RA and inadequate response to methotrexate (MTX) use were randomized 3:3:2:3 to FIL 200 mg (FIL200) or FIL 100 mg (FIL100) once daily, adalimumab 40 mg biweekly, or placebo, all with background MTX. We evaluated the change from baseline (CFB) in modified total Sharp score (mTSS), erosion score, and joint space narrowing score among patients achieving Clinical Disease Activity Index (CDAI) remission (CDAI ≤ 2.8), low disease activity (LDA; 2.8 < CDAI ≤ 10), medium disease activity (MDA; 10 < CDAI ≤ 22), and high disease activity (HDA; CDAI > 22) at 24 weeks.

Results: At week 24, the least squares (LS) mean CFB in mTSS was similarly low across treatments among patients who achieved CDAI remission (range 0.00-0.11) or LDA (n = 285 and 575, respectively). In patients with MDA and HDA (n = 471 and 157, respectively), smaller LS mean CFB in mTSS was seen in the FIL200 group vs. the placebo group (P < 0.05 for both).

Conclusions: RA clinical remission and LDA achievement were associated with suppressed progression of joint destruction over 24 weeks in all treatment groups. Only FIL200 significantly inhibited joint damage compared with placebo in patients with MDA or HDA, indicating an uncoupling of clinical disease activity and structural progression in patients receiving FIL200.

Trial registration: NCT02889796.