Mycophenolate mofetil as a therapeutic agent for interstitial lung diseases in systemic sclerosis

Systemic sclerosis (SSc) is an intractable disease that causes fibrosis in all organs. Approximately 40% of patients with SSc have some degree of interstitial lung disease (ILD). One third of patients with SSc and ILD, approximately 15% of all patients, have pulmonary lesions, which slowly progress to respiratory failure resistant to corticosteroid and other treatments. A randomized controlled trial conducted in the United States indicated that one year of treatment with oral cyclophosphamide in patients with SSc-ILD had a significant but modest beneficial effect on lung function, dyspnea, thickening of the skin, and health-related quality of life. However, all the effects, except for a sustained impact on dyspnea, disappeared approximately one year after stopping oral administration of cyclophosphamide. A randomized controlled trial using cyclophosphamide and mycophenolate mofetil (MMF) was then held in the United States for 142 patients with SSc-ILD. Treatment of SSc-ILD with MMF for two years or cyclophosphamide for one year both resulted in significant improvements in lung function over the 2-year course of the study. Leukopenia and thrombocytopenia occurred less often in patients administered MMF than in those administered cyclophosphamide. MMF is currently not approved for the treatment of SSc-ILD in Japan. Both MMF and cyclophosphamide were effective against ILD associated with SSc and, in particular, MMF was useful in terms of tolerability. When MMF is approved, it should be positioned as one of the first treatment options for SSc-ILD, which will further enhance the treatment of this disease in Japan.