Inclusion Criteria:  Participants at least 18 years of age Locally advanced not amenable to curative therapy, or metastatic disease Histologically documented non-squamous NSCLC with HER2 mutation in exons 19 or 20 by tissue NGS or ctDNA Treatment-naïve for palliative intent systemic therapy for locally advanced or metastatic disease Left ventricular ejection fraction (LVEF) ≥ 50% Measurable disease assessed by Investigator based on RECIST 1.1 Protocol-defined adequate organ function including cardiac, renal, hepatic function ECOG 0-1 Having tumour tissue available for central testing  Exclusion Criteria:  Tumors with targetable alterations to EGFR (or other targetable mutations including but not limited to ALK, if routinely tested as a targetable alteration with approved available therapy) Any clinically active brain metastases; previously treated brain metastases allowed Active autoimmune or inflammatory disorders Medical history of myocardial infarction within 6 months prior to randomization History of non-infectious pneumonitis/ILD, current or suspected ILD Lung-specific intercurrent clinical significant severe illness Contraindication to platinum-based doublet chemotherapy or pembrolizumab