Trends in Initiation of Disease-Modifying Antirheumatic Drugs for Rheumatoid Arthritis Among Commercially Insured Adults in the United States, 2001-2021.

To evaluate patterns in disease-modifying antirheumatic drugs (DMARDs) initiations between 2001 and 2021 among adults with Rheumatoid Arthritis (RA) in the United States METHODS: This retrospective cohort study used a US commercial claims database (2001-2021) to identify patients (≥ 18 years) with RA newly initiating a DMARD. We calculated the annual proportion of initiations for 22 DMARDs, categorized as conventional synthetic (csDMARDs), biologic (bDMARDs), and targeted synthetic (tsDMARDs). Secondary analyses examined trends in first-line non-csDMARD initiation and biosimilar uptake. We identified 407,728 DMARD initiation episodes among 229,365 unique patients with RA (median age: 50 years IQR, 44-58 years; 79.4% female). There were shifts in DMARD initiations, with csDMARD initiation declining from 79.9% of initiations in 2001 to 54.7% by 2021 (p 40%). Biosimilar uptake stayed below 1%. Expanded DMARD options over the last two decades have led to decreased csDMARD initiations and increased b/tsDMARD initiations, reflecting patient- and system-level factors.