Background/Purpose:   Rheumatoid arthritis (RA) is a chronic disease that requires long-term treatment to improve or maintain disease activity.  Tumor necrosis factor inhibitors (TNFi), a class of biologic disease-modifying antirheumatic drugs (bDMARDs), are effective at treating symptoms and inhibiting joint progression.  Although treatment changes are not recommended in patients with stable disease, health plans have recently enacted formulary changes with higher copayments that could disrupt patient access to TNFis.  Our purpose was to describe impacts of formulary copayment changes on TNFi use among patients with RA using the TNFi etanercept (ETN).

Methods:   This retrospective observational cohort analysis used the IBM Watson Health MarketScan Commercial database.  The study population included adults (aged 18–64 years) with RA, with 6 months continuous ETN use (no gap ≥45 days) during 1/1/2013–12/31/2015 (defined as stable use period), and continuous plan enrollment ≥6 months before and ≥12 months after index date (first date after a patient’s 6-month stable-use period).  ETN persistence, bDMARD switching, refill gaps, and treatment effectiveness (using a validated effectiveness algorithm) were described for patients with or without formulary change during 12 months after index.  Average ETN copayment was calculated at the drug plan-level.  Formulary change was defined as a monthly increase of >$40 to account for copay changes attributable to ETN wholesale acquisition costs between 2014–2015. This amount also corresponded to the 90^th percentile of average plan-level changes in ETN copayments in the database, representing an average change in copay by a payer.

Results:   A total of 1,970 patients met study inclusion criteria (mean age 50.3 years, standard deviation 9.5; 77.8% female).  Of these, 133 (6.8%) patients had a formulary change during follow-up.  Overall, most patients (60.3%) persisted on ETN for the 12-month follow-up period; 13.0% switched from a bDMARD, and 26.7% discontinued (gap of ≥45 days).  Nearly half (48.0%) of all patients were considered effectively treated according to the validated algorithm.  Compared to patients without a formulary change, those with a formulary change more likely to switch biologics (19.5% vs 12.6%, P = 0.021) and tended to be less likely to be persistent (54.1% vs 60.7%, P = 0.135), and less likely to be effectively treated (42.1% vs 48.4%, P = 0.161) (Table).  Patients with a formulary change also tended to be more likely to discontinue bDMARDs for at least 12 months (10.5% vs 7.9%; P = 0.293).

Conclusion:   Using a combination of health plan- and patient-level data, this retrospective administrative claims database analysis identified a cohort of stable ETN patients and found a significant association between changing formulary status and switching bDMARD therapy for RA and negative trends for persistence and treatment effectiveness.