(254) Trends in New Use of Disease-Modifying Antirheumatic Drugs Among Children with Juvenile Idiopathic Arthritis in the United States, 2001-2022

Background: Juvenile idiopathic arthritis (JIA) is the most common childhood rheumatic disorder. An increasing array of disease-modifying antirheumatic drugs (DMARDs) have become available to treat JIA. However, few population-based data exist on recent DMARD trends for JIA.

Objectives: To describe trends in DMARD use for JIA among commercially insured children in the US from 2001 to 2022.

Methods: We performed a serial cross-sectional drug utilization study using MarketScan data (2000-2022). We included children ages 1-18 years old with 12-month continuous baseline eligibility and >1 JIA diagnosis code who initiated a DMARD. Children with prior cancer, inflammatory bowel disease, or non-JIA rheumatic diseases were excluded. DMARDs were categorized as conventional synthetic (csDMARD), biologic (bDMARD), or targeted synthetic (tsDMARD). Usage was expressed as a percentage of new DMARD initiations per calendar year, by drug type and individual agent. In secondary analyses, we examined the first b/tsDMARD used after csDMARDs.

Results: A total of 20,282 new DMARD use episodes were identified among 13,719 individuals (median age 14 years [interquartile range 10, 16]; 67.5% female). csDMARDs were the most common DMARD type across all years, but their use declined from 89.5% of all initiations in 2001 to 42.9% in 2022. In contrast, bDMARD use increased from 10.5% in 2001 to 35.2% in 2022, most commonly tumor necrosis factor inhibitors (TNFi). Among TNFi, etanercept (first in class) peaked at 28.3% in 2006 and declined to 4.4% by 2022. Meanwhile, use of adalimumab (another TNFi) doubled from 7.0% in 2007 to 14.0% in 2008 after approval for JIA, increasing further to 20.2% in 2022 following a new, less painful formulative release. However, overall use of TNFi has declined with increasing use of other b/tsDMARDs, particularly ustekinumab (rising after approval for pediatric psoriasis in 2017; 10.5% in 2022), secukinumab (rising after approval for JIA in 2021; 4.8% in 2022), and tofacitinib (first targeted oral agent approved for JIA, 2020; 3.7% in 2022). Adalimumab was the most common b/tsDMARD initiated first after csDMARDs (75.9% in 2022).

Conclusions: Among children with JIA in the US, use of b/tsDMARDs is rising with increasing availability, with accompanying declines in use of csDMARDs, which are less targeted and often less well-tolerated. Among b/tsDMARDs, adalimumab is most commonly used and the predominant b/tsDMARD initiated first after csDMARDs for JIA in the US. Patterns in DMARD use for JIA continue to evolve in relation to multiple factors, including regulatory approvals for JIA and other pediatric indications as well as the tolerability of available formulations.