A Narrative Review of Acthar Gel for the Treatment of Myositis.

Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders characterized by symmetric proximal muscle weakness and chronic inflammation, with an increased risk of morbidity and mortality. The current standard of care includes traditional immunosuppressive pharmacotherapies; however, some patients cannot tolerate or do not adequately respond to these therapies, highlighting the need for alternative treatments for refractory disease. Acthar Gel (repository corticotropin injection) is a naturally sourced mixture of adrenocorticotropic hormone analogs and other pituitary peptides that has been approved by the US Food and Drug Administration since 1952 for use in patients with two subgroups of IIMs, dermatomyositis (DM) and polymyositis (PM). However, it has not been routinely used in the treatment of IIMs. While Acthar may induce steroidogenesis, it also has a steroid-independent mechanism of action by exerting immunomodulatory effects through the activation of melanocortin receptors on immune cells, such as macrophages, B cells, and T cells. Recent clinical trials, retrospective analyses, and case reports add to the growing evidence suggesting that Acthar may be effective in patients with DM and PM. Here we review the current evidence supporting the safety and efficacy of Acthar for the treatment of refractory DM and PM.