The term interstitial lung disease (ILD) includes an enormous amount of parenchymal pulmonary disorders (>200). The appropriate and strict categorization of the underlying process was always considered pivotal for the management, as well as the prediction of outcomes. The vast majority of the ILDs are categorized in some connective tissue disease associated ILD (such as Rheumatoid arthritis, Scleroderma, Sjogren’s). The most well studied and most devastating ILD is Idiopathic Pulmonary Fibrosis (IPF), with other well studied ILDs being chronic hypersensitivity pneumonitis (CHP), Non-specific Interstitial pneumonia (NSIP) and Sarcoidosis-ILD. When the accurate diagnosis cannot be pinpointed the patient may be “classified” as Unclassifiable. To highlight the unknowns around unclassifiable ILD and to allow further research into the condition, a research group established a new diagnostic entity termed interstitial pneumonia with autoimmune features (IPAF). All these different classifications has led to much clinical and translational research, but in fact, there are actually no advances in the pharmacological treatment of ILD patients, other than IPF, compared to 10 or 20 years ago, thus highlighting the major unmet need. ILD dominates the morbidity and mortality in all these individual categories and while in some cases the disease can be self-limited or controlled by immunosuppression and antigen removal in the case of CHP, in other cases the fibrosis can take its own course, become self-sustained, progressive and fatal. Until now, though these patients were not entitled to receive any additional therapy and the novel antifibrotics, Nintedanib and Pirfenidone, were only indicated for IPF. Pirfenidone aimed to evaluate its efficacy at treating patients with unclassifiable disease, including patients with IPAF. In a Randomized Placebo Controlled, phase 2 clinical trial the authors aimed to establish a new and innovative endpoint for ILD trials, using home-based FVC measurement as the primary endpoint. Unfortunately, there were obvious technical difficulties and the endpoint of the trial was not met. However, the exploratory data, including the classical endpoint in IPF trials (rate of FVC decline) were overwhelming. At 24 weeks, the Pirfenidone treated group showed almost stable FVC, as the decline was only 17.8 mL compared 113.0 mL in the placebo group. The study had several other limitations, regarding the diagnosis of Unclassifiable and the absence of central CT review. Collectively, the trial was a negative study with many limitations and the secondary endpoints, although positive, should be interpreted with caution. Nevertheless, the data are encouraging for patients with unclassifiable ILDs that no approved therapy exists to date.
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