Patients with rheumatoid arthritis (RA) who switch to a rituximab (RTX) biosimilar (RTX-B) for nonmedical reasons have similar disease activity compared with patients with RA who continue on their original rituximab (RTX-O) therapy, study results published in Rheumatology suggest.
Researchers also found that comorbidities, previous use of disease-modifying antirheumatic drugs (DMARDs), and fewer previous RTX-O cycles were predictors of RTX-B discontinuation in patients with RA.
This observational, retrospective study included 337 patients with RA (mean age, 63.7±12.3 years) who had received 1 or more cycles of RTX since 2002 and had required re-treatment from 2017 to 2019. Through shared decision making, a total of 255 patients switched to RTX-B for nonmedical reasons whereas 82 patients stayed on RTX-O. The investigators of the study evaluated switch strategy efficacy using disease activity score in 28 joints for rheumatoid arthritis with C-reactive protein (DAS28-CRP) and RTX retention and compared these assessments between RTX-B and RTX-O.
The investigators found no significant difference at 4 months between the RTX-B switch vs the same point after the last RTX-O cycle in terms of the mean DAS28-CRP (2.77±1.01 vs 2.86±1.14, respectively; mean difference, -0.09 [95% CI, -0.29 to 0.11); P =.367. The 18-month retention estimates were also similar between the RTX-B group and the RTX-O group (75.6% [95% CI, 69.4-80.7] vs 82.3% [95% CI, 70.4-89.8], respectively).
There was no difference between the 2 groups with regard to discontinuation risk for any reason (aHR 1.52 (95% CI, 0.85-2.73); P =.157; 16.5% of patients reported discontinuation because of loss of effectiveness (LOE) whereas 2% of patients discontinued for LOE because of adverse events (AEs).
A multivariable analysis found that variables associated with RTX-B discontinuation included an increased number of comorbidities (odds ratio [OR] 2.03 [95% CI, 1.39-2.95]; P <.001) and receipt of 2 or more previous biologic DMARDs (OR 5.23 [95% CI, 2.19-12.48]; P <.001).
In the RTX-B group, 30 patients reverted to RTX-O because of LOE vs 4 who switched back because of AEs. Another 13 patients started another biologic agent or targeted synthetic DMARDs. A total of 28 of the 30 patients who returned to RTX-O for LOE were still on this therapy at a mean follow-up period of 7.7±5.2 months.
Limitations of this study included its retrospective nature as well as the evaluation of patients from a single center.
In spite of these limitations, the investigators concluded that the “data support the overall effectiveness and safety of a shared decision-making biosimilar switch strategy approach” and suggested the identified patient characteristics predictive of RTX-B discontinuation “may have utility in guiding patient selection in order to minimize treatment disruption.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Melville AR, Md Yusof MY, Fitton J, et al. Real-world experience of effectiveness of non-medical switch from originator to biosimilar rituximab in rheumatoid arthritis. Rheumatology (Oxford). Published online January 12, 2021. Doi: 10.1093/rheumatology/keaa834