THE ECONOMIC IMPACT OF THE INTRODUCTION OF INFLIXIMAB-BIOSIMILAR: AN EMPIRICAL ANALYSIS USING THE TUSCANY HEALTHCARE ADMINISTRATIVE DATABASES

Objectives: To understand economic implications following the recommendation set in 2015 by Tuscan Health Authority to use infliximab-biosimilar (IFX-BI) using data from regional administrative databases. Methods: Using the Tuscan healthcare administrative databases we identified prevalent users of IFX on January 1st, 2013 (only infliximab-originator available, IFX-OR) and on January 1st, 2016 (infliximabbiosimilar recommended, IFX-BIorOR) for any indication. For each group, resources utilization related to IFX, other biologic disease modifying antirheumatic drugs (DMARDs), hospital admissions, emergency department (ED) and specialist visits were retrospectively collected over 2 years. Groups were matched by propensity score (PS) method using age, gender, diagnoses and treatment history as matching variables. Direct costs were then compared between groups using generalized linear regression model adjusting for covariates and considering robust standard error. Results: Out of 454 IFX-OR and 434 IFX-BIorOR users retrieved, after the PS matching the study cohort was composed by 303 cases in each group and patients were well matched. Over 2 years median per-patients overall costs were significantly lower in the IFX-BIorOR group (16,186V [10,230-23,334V] vs 17,900[12,101- 25,925V], p=0.011), in particular IFX costs were also significantly lower in that group (10,210V [2,792-16,333V] vs 13,155V [4,872-20,463V], p,0.001). At multivariable analysis the IFX-BIorOR group showed borderline similar costs (p=0.05); indeed in this group IFX costs were significantly lower (p,0.001), costs for ED and specialist visits were higher (p.0.001 for both) while hospitalization costs were similar between groups (p=0.472). Conclusions: Results showed that the introduction of BI significantly reduced costs associated to drug consumption. The impact on the overall costs was borderline significant because treatment savings were compensated by higher costs for specialist and ED visits. These higher costs likely reflect a precautionary approach to the use of IFX-BI from both clinicians and patients. Further studies are needed to clarify mechanisms underlining the economic impact highlighted in this preliminary evaluation.