Six-month remission rates with biosimilar versions of rituximab are comparable to those seen with the original therapy in adults with granulomatosis with polyangiitis and microscopic polyangiitis, according to a real-world multicenter cohort study published in ACR Open Rheumatology.
Real-World Canadian Study Tracks Outcomes Across Treatment Groups
The study, titled “Biosimilar Rituximab in ANCA-Associated Vasculitis Compared to the Originator: A Multicenter Cohort Study,” evaluated 144 adults with granulomatosis with polyangiitis (GPA) and 63 adults with microscopic polyangiitis (MPA) treated between 2018 and 2023 across nine Canadian centers, as part of the BRAVO research initiative (NCT05716334). ANCA-associated vasculitis (AAV) is a group of rare autoimmune disorders characterized by inflammation and damage in small blood vessels. This damage is driven by ANCAs, which are self-reactive antibodies that abnormally activate immune cells to attack blood vessel walls, frequently affecting the kidneys, lungs, and upper airways.
Rituximab is administered directly into the bloodstream to deplete B-cells—immune cells involved in antibody production—thereby inducing remission or preventing relapses. While biosimilars of rituximab are approved and widely used for blood cancers and other autoimmune conditions, researchers noted that no clinical trials had previously been conducted specifically in AAV populations, which exhibit different disease mechanisms and adverse event patterns. Provincial public payors in Canada began requiring biosimilars for new patients starting in 2020, and mandated that some existing patients switch from the originator therapy starting in 2021.
Did you know? More than 85% of study participants who received a biosimilar were treated with Ruxience (rituximab-pvvr), making it the most commonly utilized biosimilar in the Canadian cohort.
Six-Month Remission Rates and Adverse Event Comparisons
Researchers focused on a prespecified six-month remission outcome defined as a Birmingham Vasculitis Activity Score of zero. Among 197 analyzed participants, six-month induction remission rates reached 96% for the original medication and 90% for biosimilars. When two participants in the biosimilar group who died within one month of starting treatment—prior to achieving remission—were excluded, the biosimilar remission rate adjusted to 93%. One minor relapse occurred in each induction group among participants with GPA, and changes in organ damage assessed via the Vasculitis Damage Index showed no significant differences between cohorts.
An exploratory analysis did reveal a significantly higher three-month remission rate for the original rituximab compared to biosimilars at 94% versus 79%, raising questions about whether remission might occur more slowly with biosimilars. However, the study authors cautioned that further research is necessary. Maintenance data showed that all 22 evaluable participants on the original therapy and all 33 on biosimilars remained in remission at six months. Furthermore, all 16 participants who were mandated by payors to switch from the originator to a biosimilar maintained remission at the six-month mark.
Safety Profiles and Mortality Outcomes in AAV Patients
Serious adverse events, including infections, occurred in 21 participants, with no statistically significant difference in rates between the original and biosimilar groups. Three deaths occurred across the study cohorts during the tracking period. Two patients in the biosimilar induction group died within the first month—one due to active AAV with pulmonary hemorrhage and another from COVID-19 pneumonia. Additionally, one participant in the switch group died from pneumonia.
Study authors acknowledged several limitations, including an observational design, relatively small maintenance and switch groups, and a follow-up period limited to six months. Despite these constraints, the researchers concluded that their real-world data support continued biosimilar rituximab use in AAV and should reassure patients, healthcare providers, and policymakers alike.
Frequently Asked Questions
What is a biosimilar version of rituximab?
A biosimilar is a biologic therapy that is highly similar to an original FDA- or health agency-approved medication, possessing no clinically meaningful differences in safety or effectiveness, typically offered at a lower cost.
How does rituximab treat ANCA-associated vasculitis?
Rituximab is infused into the bloodstream to deplete B-cells, which are immune cells that produce the self-reactive antibodies responsible for attacking small blood vessels in organs like the kidneys and lungs.
Did patients who switched from the original drug to a biosimilar experience relapse?
No. According to the study data, all 16 participants who transitioned from the original therapy to a biosimilar remained in remission at the six-month evaluation.
Explore More: Subscribe to our newsletter for the latest updates in rheumatology research, clinical trials, and real-world medical data. Share your thoughts or questions about biosimilar treatments in the comments below.
Worth a look