Individuals who are rituximab-naïve remained stable after 2 years of follow-up, the analysis shows.
Mandatory non-medical switch to biosimilar rituximab in individuals with rheumatoid arthritis (RA) is effective, with no deterioration in disease activity outcomes, according to real-life data published in Rheumatology International.
Individuals who are rituximab-naïve remained stable after 2 years of follow-up, investigators said.
The drug survival rates were similar to data for rituximab, the reference drug.
Investigators included individuals who had RA and switched from biosimilar rituximab, MabThera (Roche) to biosimilar rituximab, GP2013 (Rixathon; Sandoz). They also started therapy naïve to rituximab with GP2013.
Individuals were from an ordinary outpatient clinic in Norway between June 2018 and November 2021, with 1 individual from 2018, 84 individuals in 2019. Because of the COVID-19 pandemic, the number of individuals recruited dropped, and 20 individuals were included from 2020 and 5 from 2021.
There was a statistically significant difference between biosimilar rituximab-naïve and biosimilar rituximab-switched individuals for disease duration at 3 years and 14.2 years and steroid use 68.2% and 35.2%, respectively.
Additionally, 90.9% of biosimilar rituximab-naïve individuals received 2000 mg and 85.3% of biosimilar rituximab-switchers received either 500 or 1000 mg.
All disease activity measures were higher for those who were naïve.
The treatment effect for individuals who switched was maintained during the follow-up for all disease activity except patient-reported outcomes (PROs). Clinical disease activity index (CDAI) and patient global assessment (PGA) increased after 2 years and were higher than the baseline value from 2.65 to 3.80 and 20 to 30, respectively.
For those who were naïve, the improvement in all disease activity measures and PROs was observed after year 1 and statistically significant erythrocyte sedimentation rates (ESR) at 0.004, 28 swollen joint counts at 0.043, 28 tender joint counts at 0.001, DAS28-ESR at 0.014, disease activity score with 28 joint counts (DAS28)-C-reactive protein (CRP) at 0.002, CDAI at 0.010, PGA at 0.007, and investigator global assessment at 0.019, but not for CRP. The improvement was also maintained after year 2 of follow-up.
The overall drug survival for biosimilar rituximab was 80% at 1 year and 57.7% at 2 years. For the switched group, the drug survival was 84.1% and 60.2%, respectively. For the naïve group, the drug survival was 63.6% and 49%, respectively.
In the total cohort and switched group, the most frequent reason for drug discontinuation was remission at 38.6% and 40.3%, respectively, followed by doctor’s decision at 27.1% and 27.4%, and adverse effects at 14.3% and 12.9%, respectively.
Patient’s decision, death, and other for discontinuation was 5.7% and 6.5%, respectively, for all 3 reasons, investigators reported.
Limitations of the study included that the study was an observational study, so there were levels of missing data, confounding factors, and attrition bias.
Additionally, because data were pulled from a single center, a relatively low number of individuals enrolled, and lack of safety data were also important limitations of the study to note, according to investigators.
Łosińska K, Korkosz M, Pripp AH, Haugeberg G. Real-world experience of rituximab biosimilar GP2013 in rheumatoid arthritis patients naïve to or switched from reference rituximab. Rheumatol Int. 2023;1-8. doi:10.1007/s00296-023-05307-4