OBJECTIVES: Seven FDA-approved adalimumab biosimilars are anticipated to launch in the US in 2023, potentially yielding reductions in treatment cost –a known factor driving disparities in healthcare. Here we identify and characterize patients with RA who persist on low-cost csDMARDs without evidence of improved disease control, as a surrogate for the population who may benefit from availability of lower-cost biosimilars.

METHODS: Data: PIONEER-Rheumatology, an open text-enhanced EMR database specific to care given by the American Rheumatology Network. Study populations: Adult (18+y) patients with RA, first csDMARD in 2018-2021 (index), >18m follow up from index, disease assessments (CDAI, RAPID3, and/or DAS28) within -180d to +30d (baseline) and within +120d to +365d of index, remaining on csDMARDs ≥365d. Minimally important difference (MID) between baseline and during csDMARD treatment defined as: CDAI >12 when starting >22, >6 when starting 10–22, and >1 when starting <10; DAS28 >1.2; RAPID3 >1.27 (10 point scale). Analyses: T-test, Pearson’s chi-square, proportions comparisons by z-test, Bonferroni correction.

RESULTS: 2342 study patients: white (56.8%), female (72.6%), commercial coverage (56.0%), and median age of 61 (IQR 51-70) with 42.3% ≥65y. Most patients had moderate/severe disease at index (70.7%) by at least 1 measure. 1360/2342 (58%) patients persisted on csDMARDs ≥365d without achieving MID. In the subset with moderate/severe activity at baseline, MID was not achieved by 761/1656 (46%) patients. In contrast to those achieving MID, the population not benefiting from csDMARD had higher proportions of female gender (78.4% v 68.7% achieved MID, p<0.01), black race (11.4% v 6.6% achieved MID; p<0.01), and Medicaid coverage (7.1% v 3.6% achieved MID; p<0.01).

CONCLUSIONS: More than half of study patients – disproportionately of female gender, black race and/or Medicaid coverage – had no observed improvement in disease despite persisting on csDMARDs for ≥365d. These patients may benefit from availability of lower-cost biosimilars.