Abstract
Objective The market entry of biosimilars is expected to bring budgetary relief. Our objective was to determine how the introduction of biosimilars influences medication cost in patients with rheumatoid arthritis and which patients gain access to biologicals due to the availability of biosimilars.
Methods Using hospital data of patients with rheumatoid arthritis between 2014 and 2018, an interrupted time series was performed. The interruption in the time series was placed at June 2016, i.e., the introduction of the etanercept biosimilar. The changes in trends for rheumatic medication cost before and after the interruption were measured. Secondary analyses focused on explaining these trends.
Results In the first quarter after the interruption, there was a decrease in total cost for biologic users of €-63020 (CI=[€-96487;-€-29553]; P=0.001). The post-interruption trend did not differ from the pre-interruption trend (CI=[-€6695;€6715]; P=0.998) and after three quarters the medication cost were back at the interruption level. After the interruption, the average cost per biologic user decreased by €-370 (CI=[€-602;€-138]; P=0.005), followed by a quarterly decrease (relative to the pre-interruption trend) (CI=[€-86;€-14] P=0.010), bending the average cost curve. The percentage of patients being treated with biologics increased in post-interruption by 0.50 percentage points quarterly (CI=[0.38-0.62]; P<0.001). Also the average age at the start of the first biologic increased after the interruption (p=0.057).
Conclusion The average cost per patient treated with biologicals decreased after the introduction of biosimilars with a persistent trend. However, the budgetary relief due to market entry of biosimilars vanished quickly due to an increase in patients treated with biologics.