This study is open to people with idiopathic pulmonary fibrosis (IPF) or progressive pulmonary fibrosis (PPF). They can only take part if they have completed treatment in a previous study with a medicine called nerandomilast or BI 1015550.

The goal of this study is to find out how well people with pulmonary fibrosis tolerate long- term treatment with nerandomilast. The study also tests whether nerandomilast improves lung function and prolongs the time until symptoms get worse, participants need to go to the hospital, or die.

Every participant takes nerandomilast as tablets for up to 1 year and 10 months. The participants may also continue their regular treatment for pulmonary fibrosis during the study.

Participants visit their doctors regularly. During these visits, the doctors collect information on any health problems of the participants. Participants also regularly do lung function tests.

Inclusion Criteria:

1. Patients who completed treatment in the parent trials (1305-0014, 1305-0023, or 1305-0035) without prematurely discontinuing treatment permanently according to protocol (i.e. completed treatment with or without temporary treatment interruption)
2. Signed and dated written informed consent in accordance with ICH-GCP and local legislation prior to admission to the trial
3. Women of childbearing potential (WOCBP) must be ready and able to use highly effective methods of birth control per ICH M3 (R2) that result in a low failure rate of less than 1% per year when used consistently and correctly. WOCBP taking oral contraceptives (OCs) also have to ensure the use of one barrier method during sexual intercourse with their partner, e.g., condom to account for the risk of potentially reduced efficacy of the OCs in the event of severe vomiting and diarrhoea. For France, fertile males must be ready and able to use acceptable methods of birth control

Exclusion Criteria:

1. Any disease that may put the patient at risk when participating in this trial at investigator's discretion.

2. Patient exhibits suicidality, in the clinical judgment of the investigator or according to the following criteria at Visit 1:

   • any suicidal behaviour (i.e. actual attempt, interrupted attempt, aborted attempt, or preparatory acts or behaviour)
   • any suicidal ideation of type 4 or 5 in the Columbia-Suicide Severity Rating Scale (C-SSRS) (i.e. active suicidal thought with intent but without specific plan, or active suicidal thought with plan and intent)

3. Patients with clinically relevant severe depression at investigator's discretion or a Hospital Anxiety and Depression Scale (HADS) subscore >14 at Visit 1.

4. An occurrence of malignant neoplasm other than appropriately treated basal cell carcinoma or in situ squamous cell carcinoma of the skin or in situ carcinoma of uterine cervix at Visit 1.

5. Patient will undergo lung transplantation, with an assigned date of surgery.

6. Patients with a Body Mass index (BMI) <18.5 kg/m² that experienced an additional, unexplained and clinically significant (>10%) weight loss during the parent trial

7. At Visit 1, patients with ongoing Adverse Event of Special Interest (AESI), except for latent tuberculosis (suspected vasculitis, Drug Induced Liver Injury (DILI), severe infections) that led to temporary treatment interruption in the parent trial

8. Patients who must or wish to take restricted medications or any drug considered likely to interfere with the safe conduct of the trial.

Further exclusion criteria apply.

Once the criteria in section "Time Frame" are fulfilled, researchers can use the following link https://www.clinicalstudies.boehringer-ingelheim.com/msw/datasharing to request access to the clinical study documents regarding this study, and upon a signed "Document Sharing Agreement".

Furthermore, researchers can request access to the clinical study data, for this and other listed studies, after the submission of a research proposal and according to the terms outlined in the website.

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.