Background: Rituximab is a monoclonal antibody directed against CD20, a pan B lymphocyte marker. It is approved in Australia for treatment of CD20-positive B cell non-Hodgkin lymphoma and rheumatoid arthritis. There is increasing off-label use of rituximab in conditions where B cells and autoantibodies play a role in the pathophysiology. Rituximab is not only expensive, but its safety in unregistered indications is uncertain.
Methods: We performed a retrospective review of the off-label use of rituximab approved by the High Cost Drug Subcommittee at the Princess Alexandra Hospital between 2005 and 2008. Cases of post transplant lymphoproliferative disorder were excluded.
Results: A total of 28 patients received rituximab for a variety of off-label indications. There were no reported cases of serious infusion reactions or other notable adverse events. The most favourable outcomes were seen in myasthenia gravis, shrinking lung syndrome, thrombotic thrombocytopenic purpura, prevention and treatment of renal transplant rejection and lupus nephritis. No benefit was observed in cases of focal segmental glomerulosclerosis (primary or post-transplant recurrence) and post-transplant recurrence of haemolytic uremic syndrome. There was limited benefit in cryoglobulinaemic vasculitis. The cost of off-label use was in excess of $210 000.
Conclusion: In the absence of formal clinical trials, decisions regarding off-label use of rituximab are difficult. Our cases contribute to the published literature and should help provide clinicians with greater insights into which conditions are likely to respond. As can be seen in our series, rituximab benefits people with certain conditions; longevity and cost-effectiveness are currently unknown.