P010 Real world experience of switching to an adalimumab biosimilar; different outcomes for axial spondylitis, psoriatic and rheumatoid arthritis

Abstract

Abstract Background/Aims Adalimumab is licenced to treat a variety of autoimmune conditions including inflammatory arthropathies. Switching stable patients from the bio-originator Humira to biosimilars has been strongly promoted on economic grounds and presumed equitable interchangeability regarding efficacy and tolerance across all disease indications. Our aims were to assess adalimumab biosimilar retention rates up to 1 year in patients with axial spondylitis (AS), psoriatic (PsA) and rheumatoid arthritis (RA) in a routine care setting and to determine by disease subtype reasons for switching back to Humira. Methods Retrospective observational study, utilising data from the St. George’s Hospital Rheumatology Biologics Database. Demographic details, retention duration and reasons for discontinuation for all patients switched from Humira to an adalimumab biosimilar were recorded up to 1 year. Results 238 patients (female 54.5%) were switched from Humira to an adalimumab biosimilar: AS n = 95, PsA n = 82, RA n = 61. Overall, 53% patients switched back to Humira over a 1-year period, female 57%. By disease subtype, the biosimilar retention rate at 1 year was AS 36%, PsA 61%, RA 46%. Overall, the reason for switching back to Humira was an adverse effect or device specific problem (AE) in 59% and loss of efficacy (IR) in 41%. AEs in 98% were pain and other injection site reactions. By disease subtype, the reason for switching back was: AS 59% IR, 41% AE, PsA 22% IR, 78% AE, RA 27% IR, 73% AE. Conclusion Projected cost savings from the adalimumab biosimilar switch programme were not achieved, with 53% returning to Humira up to 1 year later. By disease indication patients with AS had the lowest retention on the biosimilar, in whom loss of efficacy was more likely than an AE to trigger the switch, and over twice as prevalent than in patients with RA and PsA. AEs were the most prevalent reason for PsA and RA patients to switch back, and citrate in the biosimilar buffer solution was the likely reason for this. The loss of efficacy, particularly prevalent in AS patients, implies that equitable interchangeability between Humira and biosimilar products cannot be assumed, and projected cost saving advantages may be overestimated. Disclosure F.A.A. Holden: None. D. Hill: None. P. Kiely: None.