This study is open to adults 18 years and older with advanced or metastatic non-small cell lung cancer. People can join the study if they have tumours with HER2 mutations and have not yet received any systemic therapy including chemotherapy for advanced or metastatic lung cancer. The purpose of this study is to find out whether a medicine called zongertinib (BI 1810631) can slow down the worsening of advanced non-small cell lung cancer better than the standard treatment available. Zongertinib may slow cancer cell growth by inhibiting HER2. This would prolong cancer re-occurrence and increase survival. Current standard treatment is pembrolizumab plus platinum-pemetrexed chemotherapy.

Participants are put into 2 groups by chance. One group receives zongertinib at regular times throughout the study and the other group receives infusions of pembrolizumab, pemetrexed and cisplatin or carboplatin (pembrolizumab plus platinum-pemetrexed chemotherapy) into a vein.

Participants may be in the study up to a maximum of 70 months. During this time, they visit the study site about every 3 weeks for study procedures. The doctors regularly check the size of the tumour with a CT or MRI scan, at the beginning of the study and every 6 weeks. After 18 months they check the tumour size every 12 weeks. Doctors regularly check whether the cancer has spread to other parts of the body. The doctors also regularly check participants' health and take note of any unwanted effects. The time it takes for the cancer to worsen is compared between the 2 groups to see whether the treatment works. The participants also fill in questionnaires about their symptoms and quality of life.

Inclusion criteria:

1. Signed and dated written informed consent form (ICF) in accordance with International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use - Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial.
2. Patients ≥18 years of age or over the legal age of consent in countries where that is greater than 18 years at the time of signature of the ICF.
3. Histologically or cytologically confirmed diagnosis of an advanced and/or metastatic non-squamous Non-small cell lung cancer (NSCLC).
4. Documented Human epidermal growth factor receptor 2 (HER2) mutation in the Tyrosine kinase domain (TKD) as per local lab results.
5. An archival tumor tissue sample must be submitted to the central laboratory after inclusion of the patient to retrospectively confirm the HER2 status. If no archival tissue is available, this may be acceptable in exceptional cases after written agreement with the sponsor.
6. Patients who have not received any systemic treatment for unresectable, locally advanced or metastatic disease and are not eligible for curative therapy.
7. Presence of at least one measurable lesion according to Response evaluation criteria in solid tumors (RECIST) 1.1, as determined by the local site investigator/radiology assessment.
8. Eligible to receive treatment with the selected platinum-based doublet-chemotherapy (i.e. cisplatin/pemetrexed or carboplatin/pemetrexed) and pembrolizumab in accordance with the Summaries of Product Characteristics (SmPC)/Product Information.

Further inclusion criteria apply.

Exclusion criteria:

1. Previous or concomitant malignancies other than the one treated in this trial within the last 5 years, except;

   • effectively treated non-melanoma skin cancers
   • effectively treated carcinoma in situ of the cervix
   • effectively treated ductal carcinoma in situ
   • other effectively treated malignancy that is considered cured by local treatment

2. Tumors with targetable alterations with approved available therapy.

3. Lung-specific intercurrent clinically significant severe illness based on investigators assessment.

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

5. Major surgery (major according to the investigator's assessment) performed within 4 weeks prior to randomization or planned within 6 months after screening, e.g. hip replacement.

6. Any history of or concomitant condition that, in the opinion of the investigator, would compromise the patient's ability to comply with the trial or interfere with the evaluation of the safety and efficacy of the test drug.

7. History or presence of cardiovascular abnormalities such as uncontrolled hypertension, congestive heart failure New York Heart Association (NYHA) classification of ≥ III or IV, unstable angina or poorly controlled arrhythmia which are considered as clinically relevant by the investigator. Myocardial infarction, stroke, or pulmonary embolism within 6 months prior to randomization.

8. Any clinically important abnormalities (as assessed by the investigator) in rhythm, conduction, or morphology of resting electrocardiograms, e.g. complete left bundle branch block, third degree heart block.

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.