Comparison of treatment retention of originator vs biosimilar products in clinical rheumatology practice in Sweden.

Objectives: To compare treatment retention between biosimilars and their originator products among first starters (etanercept, infliximab, adalimumab and rituximab), as well as after non-medical switch.

Methods: Patients with rheumatic diseases starting, for the first time, an originator or biosimilar etanercept, infliximab, adalimumab or rituximab were identified in the national Swedish Rheumatology Quality Register. Moreover, patients switching from an originator to its biosimilar were identified and individually matched to patients continuing on the originator. One-year treatment retention was calculated and hazard ratios (HR) for discontinuation with 95% CIs were estimated, adjusting for comorbidities and socio-economic factors.

Results: In total, 21 443 first treatment courses were identified. The proportion of patients still on the drug at 1 year and the HR for discontinuation revealed no differences across adalimumab (Humira, Imraldi, Amgevita and Hyrimoz) nor across rituximab products (Mabthera, Ritemvia/Truxima and Rixathon). The proportions on the drug at 1 year were similar for Benepali (77%) and Enbrel (75%) and the adjusted HR for Benepali compared with Enbrel was 0.91 (95% CI 0.83, 0.99). For infliximab, the proportion still on the drug at 1 year was 67% for Remicade and 66% for Remsima/Inflectra and the HR compared with Remicade was 1.16 (95% CI 1.02, 1.33). Among 2925 patients switching from an originator drug to one of its biosimilars, we noted no statistically significant or clinically relevant differences in drug survival compared with those who remained on originator therapy.

Conclusion: This large observational study supports the equivalence of biologic DMARD biosimilar products and originators when used in routine rheumatology care.