Experience with low-dose rituximab in off-label indications at two tertiary hospitals

Background: Rituximab is a monoclonal antibody directed against B cells and is increasingly used to treat a variety of autoimmune conditions. Most published evidence reporting the successful use of rituximab in off-label indications has empirically used a high-dose regimen (either 375 mg/m(2) weekly for 4 weeks, or 1000 mg x 2), which is the approved course of treatment for lymphoma and rheumatoid arthritis patients. Aims: The aims of this report are to review the indications, outcomes and adverse events of low-dose (500 mg twice, given 1-2 weeks apart), off-label use of rituximab in our institutions, and to review the available evidence. Methods: We performed a retrospective audit of the off-label use of low-dose rituximab at two university teaching, tertiary referral hospitals, from mid-2008 until the end of 2011. Results: Off-label rituximab was given to 52 patients (53 indications) across a heterogeneous group of autoimmune conditions. Outcomes were known for 46 conditions (affecting 45 patients), and of these, complete responses were observed in 16 (35%) conditions and a further 19 (41%) had a partial response. There was no response to rituximab in 11 (24%) patients. There were eight significant adverse events, mostly related to infectious complications. Conclusion: This case series suggests that low-dose courses of rituximab can be used off-label to treat several severe and/or refractory immunological disorders with a reasonable safety profile; however, further trials are required in many off-label indications.