Background/Purpose: Joint swelling and tenderness are major symptoms of rheumatoid arthritis (RA). This post-hoc analysis evaluated the effect of ivarmacitinib (SHR0302), a selective Janus kinase 1 inhibitor, on joint swelling and tenderness in patients with moderate-to-severe RA, using data from a phase III clinical trial (NCT04333771, Liu J, Jiang Y, Zhang S, et al. Ivarmacitinib, a selective Janus kinase 1 inhibitor, in patients with moderate-to-severe active rheumatoid arthritis and inadequate response to conventional synthetic DMARDs: results from a phase III randomised clinical trial. Ann Rheum Dis. Published online November 27, 2024. doi:10.1136/ard-2024-226385).

Methods: Patients were randomized to receive ivarmacitinib 4 mg (n=189), ivarmacitinib 8 mg (n=189) or placebo (n=188) for 24 weeks. At week 24, patients in the placebo group switched to ivarmacitinib 4 mg, while others continued the initial regimen until 52 weeks. Changes in swollen joint count (SJC) and tender joint count (TJC) from baseline were compared between groups and between small (metacarpophalangeal joints, proximal interphalangeal joints, second through fifth metatarsophalangeal joints, thumb interphalangeal joints, and wrists) and large joints (shoulders, elbows, hips, knees, and ankles).

Results: During the initial 24 weeks, both ivarmacitinib groups demonstrated greater reductions in SJC and TJC of both small and large joints compared to placebo. From week 24 to 52, both ivarmacitinib 4 mg and 8 mg groups showed sustained benefits in improving SJC and TJC of small and large joints. (Figure 1 and Figure 2). In addition, ivarmacitinib 4 mg and placebo/placebo-ivarmacitinib 4 mg groups presented no difference in SJC or TJC reduction between small joints and large joints at most timepoints. However, ivarmacitinib 8 mg group demonstrated greater reduction of TJC in small joints compared with large joints from week 20 to week 52 (Figure 3).

Conclusion: Ivarmacitinib significantly improves joint swelling and tenderness in patients with moderate-to-severe RA. Moreover, ivarmacitinib 8 mg provides superior long-term benefits in improving tenderness of small joints than large joints.

Figure 1. Comparison of the change in SJC and TJC of small joints from baseline between groups. **, P < 0.01 between placebo vs. Ivarmacitinib 8 mg; ***, P < 0.001 between placebo vs. Ivarmacitinib 8 mg. #, P < 0.05 between placebo vs. Ivarmacitinib 4 mg; ##, P < 0.01 between placebo vs. Ivarmacitinib 4 mg; ###, P < 0.001 between placebo vs. Ivarmacitinib 4 mg.

Figure 2. Comparison of the change in SJC and TJC of large joints from baseline between groups. *, P < 0.05 between placebo vs. Ivarmacitinib 8 mg; **, P < 0.01 between placebo vs. Ivarmacitinib 8 mg; ***, P < 0.001 between placebo vs. Ivarmacitinib 8 mg. #, P < 0.05 between placebo vs. Ivarmacitinib 4 mg; ##, P < 0.01 between placebo vs. Ivarmacitinib 4 mg; ###, P < 0.001 between placebo vs. Ivarmacitinib 4 mg.

Figure 3. Comparison of the change in TJC from baseline between small joints and large joints in ivarmacitinib 8 mg group. *, P < 0.05; **, P < 0.01; ***, P < 0.001 between small joints and large joints.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effect-of-ivarmacitinib-on-joint-swelling-and-tenderness-in-patients-with-moderate-to-severe-rheumatoid-arthritis-a-post-hoc-study-of-a-phase-iii-clinical-trial/