OP0311 RETROSPECTIVE ANALYSIS OF PRESCRIPTION DYNAMICS OF ETANERCEPT AFTER INTRODUCTION OF BIOSIMILARS BASED ON NORWEGIAN PRESCRIPTION DATABASE. AN INTERIM ANALYSIS
Authors: Milada Cvancarova Småstuen, Randeep Madla, Oddvar Solli, Erik Hjelvin
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> In Norway, several high quality data registries are available that can be used to generate "real life" data. All individuals living in Norway are given a unique ID number which makes it possible to trace individuals. The Norwegian Prescription Database (NorPD) is one of the central public registers that are available for research purposes. All prescriptions being collected by individuals are recorded, including reimbursement code, dispensing date, name and dose of the prescribed drug. Following loss of exclusivity of some biologics, biosimilars are competing in the Norwegian tender. <h3>Objectives</h3> Both efficacy, bio-chemical features and patient satisfaction with biosimilars have been debated since they were introduced to replace originator. However, there is only sparse evidence as to how many patients were switched and how many are switched back to the originator so large, registry based studies are warranted. Therefore, our aim was to follow all patients on originator receiving maintenance treatment (drug prescription being collected and registered in NorPD) after biosimilar entry (BE) in order to retrospectively describe the pattern of switch and monitor dynamics, assumed to be economically motivated from patients stable on originator to biosimilars or other preferred drug. <h3>Methods</h3> We included all patients on etanercept maintenance treatment for 9 months prior to BE with maximum gap of 4 months from previous prescription retrieval. Switch was defined as discontinuation of use for at least 4 consecutive months. Prescription data scans from NorPD started March 2016 (BE) and data scans were performed every 3 months during the first 6 months of this project and every 6 months for 2 years. Final data extraction will be performed within July 2019. This abstract covers the interim analysis and the time period from 9 months prior to BE and 18 months thereafter. <h3>Results</h3> We have identified 8149 individuals on biologics prescribed in Norway. Of those, 4799 collected at least two prescriptions of etanercept before BE and are included in further analyses. The proportion of originator etanercept users declined sharply after biosimilar entry as expected for the first three months after BE and kept decreasing for the consecutive 9 months, however it changed little thereafter. A great majority of former etanercept users was switched to SB4 (70.5%) and continued with this medication, however some switched back to etanercept or other medication. A small proportion of individuals switched shortly to SB4 and then later to other medication. 5.7% of former etanercept users switched to other medication at the time of Switch date. For details, see Figure 1. Many patients switched back and forth several times, also using other medication at short time intervals. The method of distribution (pen versus injection) was associated with higher odds for being switched. Patients using etanercept pen were more likely to switch to biosimilar etanercept after BE (Figure 2). For patients who switched to SB4 the 18 months cumulative incidence of drug survival was 72%; 95%CI [65-79]%. At 2 years follow-up the drug survival in switchers will be matched with historic drug survival rate of etanercept estimated using data from NorPD. <h3>Conclusion</h3> The Norwegian Prescription Database is a useful tool that enables to monitor use, changes and trends in use of selected drugs. A longer follow-up is warranted in order to describe drug survival after switch from etanercept to biosimilar etanercept. However, close collaboration between pharmacists, clinicians and statisticians is warranted. <h3>Disclosure of Interests</h3> Milada Cvancarova Småstuen Grant/research support from: I have received a Research grant from Pfizer, Randeep Madla Employee of: Pfizer, still employed, Oddvar Solli Employee of: Pfizer, still employed by Pfizer, Erik Hjelvin Employee of: Pfizer, still employed by Pfizer