Rituximab therapy in patients with refractory dermatomyositis or polymyositis: differential effects in a real-life population

Abstract

Objectives: While a double-blind trial has not met its endpoint, rituximab (RTX) is still seen as useful in refractory DM and PM. In this study we analysed the charts of all patients receiving RTX for myositis in our institutions for objective outcome parameters.

Methods: In a retrospective way, the charts of all patients with PM or DM who received RTX were analysed for glucocorticoid dose, creatine phosphokinase (CPK) and lung function tests, as well as for serious adverse events.

Results: A total of 19 patients were identified, 1 of whom died from aspiration pneumonia 3 weeks after the first RTX infusion. The charts of 18 patients (13 PM, 5 DM) could be further analysed. In addition to the fatal pneumonia, six more severe infections were seen. One patient developed hypogammaglobulinaemia. Two patients had mild infusion reactions. Under RTX, both CPK and daily prednisolone dose were reduced by week 18. Six of eight patients with alveolitis improved under RTX. Overall, 9 of 13 PM patients responded. Six of the responders and two patients without documented response, all anti-synthetase syndrome patients, were re-treated. In contrast, all five DM patients responded and none required re-treatment.

Conclusion: In a real-life population of patients with severe, refractory PM or DM, objective improvement was seen in the majority of patients with regard to CPK and lung function tests, and glucocorticoids could be reduced. In contrast to the subgroup with DM, where one cycle of RTX appeared sufficient, patients with anti-synthetase syndromes commonly experienced flares necessitating RTX re-treatment. Infections are of concern.

Keywords: B cell depletion; dermatomyositis; idiopathic inflammatory myositis; interstitial lung disease; polymyositis; relapse; rituximab; safety.