Emerging treatments

Antifibrotic therapy

Pulmonary hypertension is a documented comorbidity in patients with fibrotic hypersensitivity pneumonitis (HP).[69] Nintedanib, a small molecule inhibitor of multiple receptor tyrosine kinases, is approved in the US and Europe to treat patients with chronic fibrosing interstitial lung diseases (ILD) which are progressive, including HP. A randomised controlled trial found that nintedanib reduced the rate of ILD progression (as measured by forced vital capacity decline) in patients who have a chronic fibrosing ILD with a progressive phenotype; however, the trial was not designed or powered to provide evidence of benefit for specific diagnostic sub-groups.[70][71]​​ Pirfenidone is a synthetic pyridone with anti-inflammatory, antioxidative, and antifibrotic effects. It is approved in the US and Europe for use in patients with idiopathic pulmonary fibrosis (IPF). An open-label trial in 22 patients with fibrotic HP compared combination treatment with prednisolone plus azathioprine, with or without pirfenidone. At 1 year of treatment, inclusion of pirfenidone was found to be safe. However, there was no significant difference between the groups in forced vital capacity, diffusion capacity of the lung for carbon monoxide, or findings on high-resolution computed tomography chest.[72] One randomised, double-blinded clinical trial of pirfenidone was carried out in patients with fibrotic HP, but enrolment was stopped early.[73]​ There were no treatment-urgent adverse events during the study. Further research is needed to establish whether pirfenidone could be useful in the treatment of non-IPF progressive pulmonary fibrosis, including fibrotic HP.[74]

Rituximab

There is some evidence that rituximab, a monoclonal antibody that binds to the antigen CD20, may be associated with stabilisation or improvement of lung function in selected patients with refractory fibrotic HP.[75][76]​​​ However, rituximab has also been reported to be a rare cause of HP.[77]

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