Background/Purpose: Abatacept is a targeted disease-modifying antirheumatic drug (tDMARD) that has demonstrated a lower risk for infection in comparison with other tDMARDs among rheumatoid arthritis (RA) patients. The potential cost differences associated with the reduced risk of infection among RA patients treated with abatacept vs. other tDMARDs is not well understood. We therefore compared infection-related hospitalization risk and associated costs of RA patients experienced with a tumor necrosis factor-α inhibitor (TNFi) who subsequently received abatacept vs. other tDMARDs, including another TNFi or other non-TNF-α inhibitor (non-TNFi).

Methods: Patients initiating a tDMARD (index drug/date) who had ≥1 inpatient diagnosis or ≥2 outpatient diagnoses of RA in the 12 months prior to the index date were identified in MarketScan data (1/1/2010-3/31/2016). Patients were required to have been previously treated with a TNFi and have 12 months of insurance coverage prior to the index date (baseline period) and throughout the follow-up period (≥12 months; up to 36). Unadjusted and multivariable adjusted regression were used to evaluate the impact of the index drug on infection-related hospitalizations and the per-patient per-month (PPPM) associated costs. Log transformation and gamma distribution were used in the regression analysis of cost data where cost values plus $1 were used so that the after the log transformation the original cost data of $0 will have the value of log(1)=0.

Results: Of the study population, 308 patients (mean age: 55 years; 86% female) were treated with abatacept, 1,032 with a TNFi (mean age: 52 years; 82% female), and 321 with another non-TNFi (mean age: 55 years; 76% female). Compared to the baseline period, the proportion of patients with infection-related hospitalizations declined in the follow-up period, as did infection-related hospitalization cost among patients treated with abatacept, while increasing in the follow-up period for both the TNFi and non-TNFi cohorts (Table). After adjusting for differences in patient characteristics, Cox regression analysis showed that the risk for an infection-related hospitalization was significantly greater for RA patients treated with a TNFi vs. abatacept (HR: 2.6; 95% CI: 1.2-5.8, P=0.02) and numerically higher for those treated with another non-TNFi vs. abatacept (HR: 1.9; CI: 0.7-4.7, P=0.19). The change in infection-related hospitalization cost PPPM was significantly higher for RA patients treated with a TNFi vs. patients treated with abatacept ($73; 95% CI: $16-$201, P=0.006); and was numerically higher but not statistically significant for patients treated with another non-TNFi ($66; 95% CI: -$8-$211, P=0.08).

Conclusion: In the real-world setting in the US, patients treated with abatacept vs. a TNFi had a lower risk for infection-related hospitalization and lower associated hospitalization cost.