Abatacept for IIM
Trial question
What is the effect of abatacept in patients with active, refractory idiopathic inflammatory myopathy?
Study design
Multi-center
Double blinded
RCT
Population
Characteristics of study participants
72.0% female
28.0% male
N = 148
148 patients (106 female, 42 male).
Inclusion criteria: patients with active, refractory idiopathic inflammatory myopathy.
Key exclusion criteria: inclusion body myositis or myositis other than idiopathic inflammatory myopathy; use of penicillamine or zidovudine in the past 3 months; use of rituximab in the past 6 months; uncontrolled or rapidly progressive ILD; severe muscle damage, permanent weakness due to a non-idiopathic inflammatory myopathy cause, or myositis with cardiac involvement; cancer-associated myositis.
Interventions
N=75 abatacept (subcutaneous dose of 125 mg weekly plus standard of care).
N=73 placebo (matching placebo plus standard or care).
Primary outcome
International Myositis Assessment and Clinical Studies definition of improvement at week 24
56%
42.5%
56.0 %
42.0 %
28.0 %
14.0 %
0.0 %
Abatacept
Placebo
No significant
difference ↔
No significant difference in International Myositis Assessment and Clinical Studies definition of improvement at week 24 (56% vs. 42.5%; OR 1.8, 95% CI 0.9 to 3.5).
Secondary outcomes
Borderline significantly greater improvement in mean Myositis Functional Index-2 at week 24 (4.1 points vs. 1.2 points; MD 2.9, 95% CI 0 to 5.8).
No significant difference in mean improvement in Myositis Response Criteria at 24 weeks (40.8 points vs. 37.2 points; MD 3.6, 95% CI -2.9 to 10.1).
No significant difference in mean decline in extramuscular global activity (1.6 points vs. 1.4 points; MD 0.2, 95% CI -0.3 to 0.6).
Safety outcomes
No significant differences in serious adverse events, death.
Conclusion
In patients with active, refractory idiopathic inflammatory myopathy, abatacept was not superior to placebo with respect to International Myositis Assessment and Clinical Studies definition of improvement at week 24.
Reference
Rohit Aggarwal, Ingrid E Lundberg, Yeong-Wook Song et al. Efficacy and Safety of Subcutaneous Abatacept Plus Standard Treatment for Active Idiopathic Inflammatory Myopathy: Phase 3 Randomized Controlled Trial. Arthritis Rheumatol. 2025 Jun;77(6):765-776.
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