Background/Purpose: In March 2015 the first infliximab biosimilars CT-P13 (Remsima™; Inflectra™), entered the Swedish market. The aim of this study was to evaluate the uptake and factors associated with use of the originator product (Remicade®) and its biosimilars.

Methods: Data from the Swedish Rheumatology Quality register (SRQ) was used to identify all patients with a rheumatic disease who started a treatment with the originator product or with its biosimilars between 1^st March 2015 and 29^th February 2016. Demographic and disease characteristics were collected and tabulated; and differences were assessed using linear and logistic regression models adjusted for age, gender and residential region. Kaplan-Meier curves were used to visualize survival on drug.

Results: During the study period, 1044 patients started treatment with infliximab; 318 started Remicade, 118 started Inflectra and 608 started Remsima (Table 1). Most patients (68%) who started a biosimilar did so following a switch from the originator product. There were large geographical variations in the relative use of originator vs. the biosimilars. Comparing the relative use across indications, the odds of being treated with a biosimilar was higher among patients with RA (OR: 1.54 (1.09-2.17)) as compared to all the other rheumatic diagnosis. There was no statistically significant difference between patients treated with originator vs.  biosimilar regarding age, gender, DAS28 at start of treatment, and duration between start of symptoms and disease diagnosis. By contrast, there was a 35% decreased odds of receiving biosimilar for each unit increase in HAQ (OR: 0.64 (0.44-0.94)), that was not statistically significant after stratification by line of treatment. Biosimilars were preferred over the originator product as second or third line of treatment (OR: 1.69 (1.18-2.41)) compared to other lines of treatment and they were more likely to be prescribed among patients whose most recent biologic was Remicade as compared to other biologic drugs (OR: 4.96 (2.98-8.39)). The Kaplan-Meier curve did not show any difference in survival on drug between the originator product and the biosimilars.

Conclusion: In Sweden, during the 1^st year of marketing, most prescriptions of infliximab were made up by the biosimilars products than by the originator product. The choice to prescribe a biosimilar instead of the originator product varied more with contextual factors than with the disease.