Use of nintedanib in interstitial lung disease other than idiopathic pulmonary fibrosis: much caution is warranted.

Interstitial lung disease (ILD) other than idiopathic pulmonary fibrosis (IPF) is currently treated with immunosuppressive therapy, with a dynamic algorithm based on continued clinical surveillance. Published results on mycophenolate mofetil, cyclophosphamide and azathioprine showed either stabilization or improvement of lung function with these therapies. However, despite treatment optimization, progression of disease in ILD other than IPF is often observed, and a role for antifibrotic drug nintedanib has been hypothesized. The present article first reviews relevant aspects when considering anti-fibrotic therapy in progressing ILD other than IPF, including accuracy of the diagnosis, optimization of disease-modifying, immunosuppressive therapy and optimal timing. Next, a critical appraisal of published results on nintedanib in ILD other than IPF considers the design of the studies, inclusion criteria, used definition of "progression" of disease, frequency and severity of side effects observed and cost of the therapy. There currently is a strong and legitimate interest in additional therapies that can help controlling progressing ILD other than IPF. When the studies on the use of nintedanib are carefully considered, however, caution should be exercised before prematurely endorsing and applying this therapy. The conduction of studies that will clarify and justify its potential role as switch vs. add-on therapy and, at the same time, a more rigorous definition of disease progression are both strongly encouraged.