Background 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.^1,2,3,4

Purpose 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.

Material and methods 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^® software and medical records, were: sex, age, rituximab off-label indication, dosage, number of cycles received.

Results 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/m² 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^1,2,3,4 (most patients received one cycle). 6/44 patients did nott start rituximab treatment.

Conclusion Systemic lupus erythematosus and vasculitis were the most frequently rituximab off-label prescribed indications and 375 mg/m² weekly for 4 weeks was the prescribed dosage. These results agree with the data published in the literature.^1,2,3,4

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.

References and/or Acknowledgements 1. Murray E, Perry M. Off-label use of rituximab in systemic lupus erythematosus: a systematic review. Clin Reumathol2010;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