2 The technology
2.1 Rituximab (MabThera, Roche Products) is a genetically engineered chimeric (mouse/human) monoclonal antibody that depletes B cells by targeting cells bearing the CD20 surface marker. Within its marketing authorisation, rituximab in combination with glucocorticoids is indicated for 'the induction of remission in adult patients with severely active granulomatosis with polyangiitis (Wegener's) (GPA) and microscopic polyangiitis (MPA)'. The summary of product characteristics states that limited data preclude any conclusions about the efficacy of subsequent courses of rituximab in people with granulomatosis with polyangiitis and microscopic polyangiitis. The summary of product characteristics also states that continued immunosuppressive therapy may be considered to prevent relapse, and may be especially appropriate in people at risk of relapse (for example, in people who have had previous relapses), but that the efficacy and safety of rituximab in maintenance therapy has not been established.
2.2 The summary of product characteristics lists the following adverse events occurring at an incidence of 10% or greater in patients receiving rituximab to treat granulomatosis with polyangiitis and microscopic polyangiitis: diarrhoea, peripheral oedema, muscle spasms, arthralgia, back pain, dizziness, tremor, insomnia, cough, dyspnoea, epistaxis and hypertension. For full details of adverse reactions and contraindications, see the summary of product characteristics.
2.3 Rituximab is priced at £174.63 per 10 ml vial and £873.15 per 50 ml vial (excluding VAT; British national formulary [BNF] edition 66). The recommended dosage for treating granulomatosis with polyangiitis and microscopic polyangiitis (2 types of anti-neutrophil cytoplasmic antibody [ANCA]-associated vasculitis) is 375 mg/m2 body surface area, administered intravenously once weekly for 4 weeks (4 infusions in total). The manufacturer's estimate of the average cost of a course of treatment is £4889.64 (based on 1.79 m2 body surface area and no vial sharing). Costs may vary in different settings because of negotiated procurement discounts.