Efficacy and safety of pirfenidone for idiopathic pulmonary fibrosis.
Idiopathic pulmonary fibrosis (IPF) is a devastating chronic fibrotic lung disease. Although the precise cause of the disease is still unknown, recent studies have shown that the pathogenesis of pulmonary fibrosis involves multiple mechanisms, with abnormal behavior of alveolar epithelial cells considered a primary event.
Pirfenidone is a multifunctional, orally available small molecule with anti-fibrotic, anti-inflammatory, and antioxidative activities, and has been shown to be a modulator of cytokines and growth factors, including TGF-β1, TNF-α, bFGF, IFN-γ, IL-1β, and IL-18 in animal models. Although its precise mechanism of action is not currently clear, pirfenidone is considered to exert inhibitory effects on multiple pathways involved in the pathogenesis of IPF. Two randomized placebo-controlled clinical trials in Japan demonstrated that pirfenidone significantly reduced the rate of decline of vital capacity in IPF patients. A Phase III study showed a significant increase in progression-free survival of patients in pirfenidone-treated groups compared to the placebo group. These results paved the way for the approval of pirfenidone for the treatment of IPF patients in Japan in 2008. The promising results of the Phase II study in Japan led to a larger international Phase III trial (CAPACITY). Subsequently, pirfenidone has also been approved in the European Union, South Korea, and Canada to date. Pirfenidone treatment is generally tolerated. Major adverse events are gastrointestinal symptoms, including decreased appetite, abdominal discomfort and nausea, photosensitivity, and fatigue, but many of these are mild and manageable. Clinical experience has shown that reduction in pirfenidone dose and the supportive use of gastrointestinal drugs are effective ways to manage these symptoms. Thus, pirfenidone treatment provides a means of intervention in the clinical course of IPF, and is a promising candidate for improving patient prognosis. For future development, it is important to establish the appropriate modality of treatment with pirfenidone and/or novel potential drugs.