Hydroxychloroquine and COVID-19: can we learn from the use of rituximab in systemic lupus erythematosus?

Rituximab (RTX), a chimeric monoclonal anti-CD20 antibody has become part of the standard therapy for patients with CD20-expressing B-cell lymphoma and rheumatoid arthritis. After encouraging results with open studies in systemic lupus erythematosus (SLE), RTX has not shown its effectiveness in randomized controlled trials. However, its efficacy has been validated in renal, hematological, and neuropsychiatric disorders. Understanding the history of RTX in SLE would be instructive in the hydroxychloroquine (HCQ) saga in COVID-19. Three steps would be necessary and sufficient before definitively closing the debate: 1) determine the effective and safe dose of HCQ, as well as the minimum duration of treatment in COVID-19; 2) define the profile of patients in whom HCQ would be more likely to be effective (especially in asymptomatic patients and/or at the onset of the first signs of the disease) and 3) conduct one or more multicentre RCT to evaluate the efficacy and safety of HCQ in COVID-19 in SSA.