Antifibrotic therapy
Pulmonary hypertension is a documented comorbidity in patients with fibrotic HP.[50]Wälscher J, Gross B, Morisset J, et al. Comorbidities and survival in patients with chronic hypersensitivity pneumonitis. Respir Res. 2020 Jan 9;21(1):12.
https://www.doi.org/10.1186/s12931-020-1283-8
http://www.ncbi.nlm.nih.gov/pubmed/31918716?tool=bestpractice.com
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.[51]Wells AU, Flaherty KR, Brown KK, et al. Nintedanib in patients with progressive fibrosing interstitial lung diseases-subgroup analyses by interstitial lung disease diagnosis in the INBUILD trial: a randomised, double-blind, placebo-controlled, parallel-group trial. Lancet Respir Med. 2020 May;8(5):453-60.
http://www.ncbi.nlm.nih.gov/pubmed/32145830?tool=bestpractice.com
Pirfenidone is a synthetic pyridone with anti-inflammatory, antioxidative, and antifibrotic effects. It is licensed 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.[52]Mateos-Toledo H, Mejía-Ávila M, Rodríguez-Barreto Ó, et al. An open-label study with pirfenidone on chronic hypersensitivity pneumonitis. [in spa]. Arch Bronconeumol (Engl Ed). 2020 Mar;56(3):163-69.
https://www.archbronconeumol.org/en-an-open-label-study-with-pirfenidone-articulo-S157921292030029X
http://www.ncbi.nlm.nih.gov/pubmed/31784348?tool=bestpractice.com
Further research is needed to establish whether pirfenidone could be useful in the treatment of non-IPF progressive pulmonary fibrosis, including fibrotic HP.[53]Raghu G, Remy-Jardin M, Richeldi L, et al. Idiopathic pulmonary fibrosis (an update) and progressive pulmonary fibrosis in adults: an official ATS/ERS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2022 May 1;205(9):e18-47.
https://www.atsjournals.org/doi/10.1164/rccm.202202-0399ST?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
http://www.ncbi.nlm.nih.gov/pubmed/35486072?tool=bestpractice.com
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.[54]Lota HK, Keir GJ, Hansell DM, et al. Novel use of rituximab in hypersensitivity pneumonitis refractory to conventional treatment. Thorax. 2013 Aug;68(8):780-1.
https://thorax.bmj.com/content/68/8/780.long
http://www.ncbi.nlm.nih.gov/pubmed/23515438?tool=bestpractice.com
[55]Keir GJ, Maher TM, Ming D, et al. Rituximab in severe, treatment-refractory interstitial lung disease. Respirology. 2014 Apr;19(3):353-9.
http://www.ncbi.nlm.nih.gov/pubmed/24286447?tool=bestpractice.com