Off-label use of rituximab in autoimmune disease in the Top End of the Northern Territory, 2008-2016

Abstract

Rituximab, an anti-CD20 B-cell depleting monoclonal antibody, is increasingly prescribed off-label for a range of autoimmune diseases. There has not previously been an audit of off-label rituximab use in the Northern Territory, where the majority of patients are Aboriginal. To evaluate retrospectively off-label rituximab use in autoimmune diseases in the Top End of the Northern Territory. We performed a retrospective audit of 8 years of off-label rituximab use at the Royal Darwin Hospital, the sole tertiary referral centre for the Darwin, Katherine and East Arnhem regions. Electronic and paper records were reviewed for demographic information, diagnosis/indication for rituximab, doses, previous/concomitant immunosuppression, clinical outcomes and specific adverse events. Rituximab was prescribed off-label to 66 patients for 24 autoimmune diseases. The majority of patients (62.1%) were Aboriginal and 60.6% female. The most common indications were refractory/relapsing disease despite standard therapies (68.7%) or severe disease with rituximab incorporated into an induction immunosuppressive regimen (19.4%). Systemic lupus erythematosus was the underlying diagnosis in 28.8% of cases. A clinically significant response was demonstrated in 74.2% of cases overall. There were 18 clinically significant infections; however, 13 were in patients receiving concurrent immunosuppressive therapy. There was a total of nine deaths from any cause. Rituximab has been used off-label for a range of autoimmune diseases in this population with a high proportion of Aboriginal patients successfully and safely in the majority of cases.