Biosimilars of Rituximab in ANCA-associated Vasculitis Compared to the Originator

The goal of this multicentre observational study is to compare the safety and effectiveness of rituximab biosimilars to the originator in Canadian patients with Granulomatosis with Polyangiitis (GPA) and Microscopic Polyangiitis (MPA), two main forms of ANCA-associated vasculitis (AAV).The main questions it aims to answer are:Is there a difference in vasculitis control between originator and biosimilar rituximab?Is there a difference in adverse effects between originator and biosimilar rituximab?In the Canadian healthcare context, are wait times to receive approval (financial coverage) for rituximab shorter for biosimilars compared to originators?Investigators will perform study assessments (including recording disease activity, damage, and adverse events) at the time of participants' usual clinical care visits, at regular intervals for 2 years after starting rituximab (for induction or maintenance treatment) or switching from an originator to a biosimilar as part of their usual care.Researchers will compare outcomes among participants who have received rituximab originators (from 2018 onwards) or biosimilars as part of their usual care, to see if there are differences in relapses, remission rates, damage, serious infections, serious adverse events, and treatment approval wait times.

Inclusion Criteria:Prospective cohort:Initiated within the last 6 months:RTX biosimilar or originator for induction ORRTX biosimilar or originator for maintenance (with or without prior RTX induction) ORSwitched from RTX originator maintenance to biosimilar maintenance (4-12 months between infusions)Historical cohort:Followed in a prospective longitudinal cohort study/registry within the CanVasc network, and initiated the following after January 1, 2018 but >6 months prior to study enrollmentRTX biosimilar or originator for induction ORRTX biosimilar or originator for maintenance (with or without RTX induction)Exclusion Criteria:patients without a diagnosis of GPA or MPApatients who did not/are not receiving RTX induction or maintenance therapypatients who initiated most recent RTX treatment course prior to Jan 1, 2018patients receiving RTX for reasons other than GPA or MPA induction or maintenance (e.g. other concurrent disease)unable to provide informed consent