Background: Biological therapy plays a major role in the management of patients with rheumatic disorders. Evidences generated at experimental settings have shown biosimilars as clinically effective, safe and cost effective. Nevertheless, real world data are lacking about cost effectiveness and causes of switching back to originator product among patients

Objectives: To describe the associated factors and cost evaluation of switching back to the originator etanercept from the biosimilar among patients with rheumatic disorders at The Robert Jones and Agnes Hunt Orthopaedic Hospital of United Kingdom

Methods: A descriptive cross-sectional study was undertaken with secondary data in a tertiary care hospital. All the patients who were switched from original etanercept (originator) to biosimilar Etanercept from October 2018 to June 2019 were included in the study. A pre-tested data extraction sheet was used in the data collection. Annual expenditure estimates for the treatment modalities were collected by consulting the experts. Descriptive analysis was done for the characteristics of the study sample and for the estimated annual costs. Associations of age and sex in the switching of treatment modalities were explored with chi-square test and Mann Whitney U test with 5% significance level.

Results: Records of 100 participants were extracted with a male to female ratio of 1: 1.4. The median [interquartile range (IQR)] of the participants was 54 (44 to 66) years. The leading three diagnoses were: rheumatoid arthritis (65%), Ankylosing Spondylitis (18%) and Psoriatic arthritis (14%). Out of the participants, 32 (32%) switched back to originator with a median (IQR) duration of 16.0 (10.5 to 19.5) weeks of commencing the biosimilar. The proportions of switching back were 28.1%, 34.4% and 37.5% among those who did, in the chronological 3- monthly intervals of the study. The main reasons for switching back included; side effects (21.9%), lack of efficacy (65.6%), both of these (9.4%) and other reasons (3.1%). Older age was observed among those who switched back (p<0.05) but gender did not show a statistically significant association (p=0.532). The annual estimated cost for biosimilar was 37.3% less than that for originator per patient.

Conclusion: In our cohort nearly one third switched back to the originator following the commencement of biosimilar incurring a financial and resource burden to the rheumatology department which in turn will have wider ramifications on the health care system. Exploring the reasons and factors associated with switching back to the originator in larger scale studies would help in planning cost-effective interventions and understanding the reasons why the patients revert back to the originator from the biosimilar therapy, especially among the older patients.

REFERENCES:

[1]Villamañan BE, Jiménez NI, Moreno RF, et al. AB1475-HPR Cost evolution of biological agents for the treatment of spondyloarthritis in a spanish tertiary hospital: influential factors in price development. Annals of the Rheumatic Diseases 2018, 77: p1867-1868. doi: 10.1136/annrheumdis-2018-eular.2681

[2]Brites L, Costa F, Freitas J, Luis M, Coutinho M, Santiago M, Duarte C, Salvador MJ, da Silva JAP. Impact of Block Switch to Biosimilar Etanercept in Practice, Accross Different Rheumatic Diseases [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). Available at <https://acrabstracts.org/abstract/impact-of-block-switch-to-biosimilar-etanercept-in-practice-accross-different-rheumatic-diseases>. Accessed [January 30, 2020].

Disclosure of Interests: None declared