Current Therapy Options for Interstitial Lung Diseases
Interstitial lung diseases (ILDs) represent a heterogeneous group of disorders characterized by inflammatory or fibrotic changes in the lung parenchyma. Simply put, they can be divided into inflammatory and fibrotic, with inflammatory ILDs often progressing to a fibrotic stage. Interstitial lung diseases are also associated with high morbidity and early mortality. The following text briefly summarizes the current recommendations regarding the therapy for these diseases.
Immunosuppressive Therapy
Immunosuppressive therapy is primarily used to treat inflammatory interstitial lung diseases.
Corticosteroids (CS) are often the first choice of medication (not only) for their relatively rapid onset of action. However, there are few randomized double-blind studies proving their efficacy in patients with ILDs. The most commonly used CS is undoubtedly prednisone. According to retrospective studies, the use of CS is associated with an improvement in lung functions and prolongation of survival in patients with nonspecific interstitial pneumonia and cryptogenic organizing pneumonia.
There are no randomized studies evaluating the efficacy of azathioprine in the treatment of ILDs. However, its use could improve lung functions in patients with systemic sclerosis (SSc), hypersensitivity pneumonitis (HP), and dermatomyositis.
Cyclophosphamide can be administered either intravenously or orally – with a higher risk of urothelial toxicity. In a prospective placebo-controlled study, a slowdown in the decline of lung functions was observed in patients with SSc when cyclophosphamide was administered. However, its effect on long-term survival has not been proven. The benefit of cyclophosphamide has also been found in ILDs associated with inflammatory myopathies. On the contrary, there is insufficient evidence of its efficacy in patients with HP or interstitial lung involvement in rheumatoid arthritis.
Mycophenolate mofetil showed similar effects to cyclophosphamide in clinical studies on patients with SSc. Its use was associated with fewer reported adverse effects. According to retrospective studies, mycophenolate can stabilize or improve lung functions in patients with HP or systemic connective tissue disease.
According to uncontrolled studies, rituximab (anti-CD20 humanized monoclonal antibody) improves lung functions in patients with SSc, inflammatory myopathies, and HP. However, randomized studies are needed in the future.
Based on positive results from randomized double-blind placebo-controlled studies with tocilizumab (humanized monoclonal antibody against interleukin IL-6), this drug was approved in the USA for the treatment of interstitial lung disease associated with scleroderma.
The efficacy of other treatments, including leflunomide, abatacept, tacrolimus, intravenous immunoglobulins, and methotrexate, is also being tested.
Antifibrotic Therapy
To slow the progression of fibrosis defined by the decline in lung functions in patients with idiopathic pulmonary fibrosis, two drugs are currently indicated: pirfenidone and nintedanib. They reduce mortality and delay the first acute exacerbation in patients even in advanced stages of lung interstitial involvement. However, the additive effect of these two drugs has not yet been proven.
They may also be useful in treating patients with progressive fibrotic ILD phenotype, where lung functions deteriorate even with adequate treatment of the inflammatory ILD.
Treatment of Comorbidities
Treatment options for comorbidities in patients with ILDs remain open. The results of studies on the use of antacids as prevention for gastroesophageal reflux and recurrent microaspirations vary. Non-pharmacological treatment, specifically stomach fundoplication, has proven to be more effective.
Medications used to treat pulmonary hypertension (riociguat and sildenafil) also do not show convincing results.
Non-Pharmacological Treatment
Non-pharmacological modalities of therapy are also important for patients with ILDs. These include home oxygen therapy for severe partial respiratory insufficiency. Additionally, breathing rehabilitation can alleviate disease symptoms and improve quality of life. Prevention and early treatment of respiratory infections, including vaccination against influenza virus, pneumococci, and SARS-CoV-2, are also crucial.
Interstitial lung diseases also remain one of the main indications for lung transplantation.
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Source: Johannson K. A., Chaudhuri N., Adegunsoye A. et al. Treatment of fibrotic interstitial lung disease: current approaches and future directions. Lancet 2021; 398 (10309): 1450–1460, doi: 10.1016/S0140-6736(21)01826-2.
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