Rheumatoid arthritis (RA) is the most common inflammatory joint disease worldwide. T-cell inhibitors, tumor necrosis factor inhibitors, interleukin inhibitors (ILIs), Janus kinase inhibitors, and B-cell depletion therapy are indicated as second-line therapy and are prescribed for other inflammatory autoimmune conditions (ankylosing spondylitis, psoriatic arthritis, psoriasis, Crohn disease, ulcerative colitis) co-occurring in an estimated 7% to 20% of patients with RA but are routinely excluded from RA studies. There is a lack of real-world evidence documenting treatment patterns in the large segment of patients with RA with inflammatory autoimmune comorbidities. To describe RA medication utilization patterns among biologic-naive patients, with and without similarly treated comorbidities. This retrospective cohort study uses administrative health claims from a large national health insurer between 2016 and 2022. Persistence, medication possession ratio (MPR), and utilization patterns were measured for patients with and without similarly treated comorbidities. Differences in means were calculated using a t-test, and Cox proportional hazards regression modeling was used to estimate persistence and hazard ratio (HR). A total of 22,946 patients with RA persisted on the index therapy for an average of 368.2 days (SD, 436). MPR varied across drug classes, with ILIs having the highest MPR at 0.95 (SD, 0.10) and B-cell depletion class having the lowest at 0.82 (SD, 0.19). Patients with RA with psoriatic arthritis were more likely to end the episode with therapy gap restart (HR, 1.1; CI, 1.02-1.22), yet patients with RA with psoriasis were less likely to experience a therapy gap restart (HR, 0.91; CI, 0.83-0.99). Among patients with RA initiated on ILIs, those with psoriasis are more likely to stop or switch compared with those without psoriasis (HR, 1.19; CI, 1.02-1.39). Among patients with RA initiated on Janus kinase inhibitors, those with psoriatic arthritis were more likely to stop or switch therapy compared with patients with RA without psoriatic arthritis (HR, 1.27; CI, 1.02-1.59). RA medication utilization varied significantly and may be influenced by comorbidities differently across RA drug classes. More research is needed to understand why therapies like tumor necrosis factor inhibitors persist longer in patients with RA with ulcerative colitis yet are discontinued earlier in patients with psoriatic arthritis.
