Abstract
<h3>Background</h3> The implementing Law 1015/2009 normalises the compassionate use of investigational drugs, access to off-label and unauthorised drugs in Spain. Rituximab is an anti-CD20 monoclonal antibody widely used in off-label conditions to treat autoimmune diseases.<sup>1,2,3,4</sup> <h3>Purpose</h3> The creation of an Autoimmune Diseases Unit (ADU) in our hospital caused an increase in the use of rituximab in off-label conditions. This study aims to identify rituximab off-label use and to describe the dosage prescribed in each indication. <h3>Material and methods</h3> Observational, retrospective study (June 2009 to March 2017). Patients who received off-label rituximab (at least one dose) prescribed by the ADU were included. Collected data, obtained from Farmatools<sup>®</sup> software and medical records, were: sex, age, rituximab off-label indication, dosage, number of cycles received. <h3>Results</h3> Forty-four patients (55±15 years’ old, 31/44 females) received off-label rituximab. Off-label indications identified (all of them of autoimmune aetiology) were: systemic lupus erythematosus (16/44), vasculitis (13/44), inflammatory myopathy (6/44), scleroderma (4/44), mixed cryoglobulinemia (3/44), others (2/44). The rituximab prescribed regimen was a cycle consisting of four doses of 375 mg/m<sup>2</sup> administered weekly, which is the dosage aprobed for the treatment of lymphoma. 23/44 patients received a single cycle of treatment with rituximab, 11/44 received two cycles, 2/44 received three cycles and 2/44 more than four cycles, which is partially consistent with the literature previously published<sup>1,2,3,4</sup> (most patients received one cycle). 6/44 patients did nott start rituximab treatment. <h3>Conclusion</h3> Systemic lupus erythematosus and vasculitis were the most frequently rituximab off-label prescribed indications and 375 mg/m<sup>2</sup> weekly for 4 weeks was the prescribed dosage. These results agree with the data published in the literature.<sup>1,2,3,4</sup> Considering the variety of off-label indications for which rituximab is prescribed in the ADU, it would be useful to develop protocols for the use of rituximab in these situations. <h3>References and/or Acknowledgements</h3> 1. Murray E, Perry M. Off-label use of rituximab in systemic lupus erythematosus: a systematic review. <i>Clin Reumathol</i>2010;29(7):707–716. 2. Hiemstra T, Jayne D. Newer therapies for vasculitis. Best Pract Res Clin Rheumatol2009;23(3):379–389. 3. Daoussis D, et al. Experience with rituximab in scleroderma: results from a 1-year, proof-of-principle study. Rheumatology2010;49:271–280. 4. Saunders P, et al. Rituximab versus cyclophosphamide for the treatment of connective tissue disease-associated intersticial luna disease (RECITAL): Study protocol for a randomised controlled trial. Trials2017;18(1):27. No conflict of interest
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