Treatment of polymyositis and dermatomyositis with conventional and biological agents

Abstract

    The new therapeutic guideline just published from the Japanese government-funded study team recommends use of glucocorticoids (GC), small-molecule immune suppressants and immunoglobulins for treatment of polymyositis (PM) and dermatomyositis (DM). While some patients do not respond to these drugs, others suffer from relapses during tapering of GC. Anecdotal reports suggest benefits of biological agents that have been proven effective in treatment of rheumatoid arthritis. However, an open-label clinical trial to block tumor necrosis factor (TNF) alpha with infliximab did not improve the muscle power of the affected patients. Similarly, an open-label clinical trial to block interleukin (IL)-1 with anakinra did not improve the muscle pathology. In the United States, a clinical trial with IL-6 receptor antibody, tocilizumab will be carried out to confirm its efficacy shown in the anecdotal case. Rituximab is an antibody against CD20 on B cells and deplete B cells. Since many reports on the cases treated successfully with this agent had been accumulated, a double blind control study was carried out in the States. However, the results were negative, leaving the possibility that subsets of the patients responded. Abatacept is CTLA-4Ig that suppress CD28-mediated T cell activation. It was used in an open-label small scale clinical trial in Europe. Since the results were positive, larger double blind studies should be performed. We have to note that no biological agents were developed specifically for treatment of PM/DM. Hopefully, discerning the pathological processes involved in PM/DM will lead to development of more specific and effective agents.