This study is open to adults with fibrosing interstitial lung disease (ILD) other than idiopathic pulmonary fibrosis (IPF). People can join the study if they have been diagnosed with this condition within the last 3 years and are at risk of developing progressive pulmonary fibrosis (PPF). The purpose of this study is to find out whether a medicine called nerandomilast helps people with fibrosing interstitial lung disease who may be at risk for their disease getting worse.

Participants are put into 2 groups randomly, which means by chance. One group takes nerandomilast tablets, and the other group takes placebo tablets. Placebo tablets look like nerandomilast tablets but do not contain any medicine. Nerandomilast is a type of medicine that may help reduce lung function decline and slow disease progression.

Participants are in the study for up to about 2 years and 4 months. During this time, they visit the study site regularly. Doctors regularly test lung function using methods like spirometry to measure forced vital capacity (FVC, maximum amount of air a participant can blow out after taking a deep breath) and DLCO (diffusing capacity of the lungs for carbon monoxide; it estimates how well oxygen moves from the lungs into the blood). Additionally, high-resolution computed tomography (HRCT) is performed to monitor how the lung condition is changing over time. The results are compared between the groups to see whether the treatment works. The doctors also regularly check participants' health and take note of any unwanted effects.

Inclusion criteria :

1. Male and female individuals ≥18 years of age at the time of first signed informed consent at Visit 1a
2. Signed and dated written informed consent in accordance with International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) - Good Clinical Practice (GCP) and local legislation prior to admission to the trial
3. Diagnosis of fibrosing interstitial lung disease (ILD) other than idiopathic pulmonary fibrosis (IPF) as established by the investigator
4. Presence of fibrotic lung disease on high resolution computed tomography (HRCT), defined as reticulation with traction bronchiectasis/ bronchiolectasis and/or honeycombing, and extent of fibrosis ≥10%, as assessed by central review prior to randomization
5. Time since ILD diagnosis ≤3 years before randomization
6. FVC ≥45% of predicted normal at Visit 1
7. Diffusing capacity of the lungs for carbon monoxide (DLCO) ≥25% of predicted normal corrected for hemoglobin (Hb) at Visit 1
8. Patients treated with permitted immunosuppressive/immunomodulatory agents for an underlying systemic disease (e.g. methotrexate (MTX), azathioprine (AZA)) need to be on stable treatment for at least 12 weeks prior to Visit 1 and during screening period
9. Further inclusion criteria apply.

Exclusion criteria :

1. Known diagnosis of idiopathic pulmonary fibrosis (IPF) based on multidisciplinary discussion (MDD) and according to the American Thoracic Society (ATS)/European Respiratory Society (ERS) 2022 guidelines
2. Known diagnosis of autoimmune-ILDs other than rheumatoid arthritis-associated ILD (RA-ILD)
3. Known diagnosis of sarcoidosis
4. Patients with predominant features of organizing pneumonia on HRCT, as assessed by central review
5. Patients who developed ILD due to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection/Coronavirus Disease 2019 (COVID-19) (based on investigators judgement)
6. Meeting criteria for progressive pulmonary fibrosis (PPF), as assessed by investigator
7. Meeting criteria for treatment with currently approved therapies for the fibrosing ILD (e.g. PPF), as assessed by investigator
8. Prior or current use of nerandomilast, nintedanib, or pirfenidone
9. Further exclusion criteria apply.

Clinical studies sponsored by Boehringer Ingelheim, phases I to IV, interventional and non-interventional, are in scope for sharing of the raw clinical study data and clinical study documents. Exceptions might apply, e.g. studies in products where Boehringer Ingelheim is not the license holder; studies regarding pharmaceutical formulations and associated analytical methods, and studies pertinent to pharmacokinetics using human biomaterials; studies conducted in a single center or targeting rare diseases (in case of low number of patients and therefore limitations with anonymization). For more details refer to: https://www.clinicalstudies.boehringer-ingelheim.com/msw/datasharing

One year after the approval has been granted by major Regulatory Authorities and after the primary manuscript has been accepted for publication, or after termination of the development program.

For study documents -upon signing of a 'Document Sharing Agreement'. For study data -1. after the submission and approval of the research proposal (checks will be performed by the sponsor and/or the independent review panel, including checking that the planned analysis does not compete with sponsor's publication plan); 2. and upon signing of a legal agreement.