• Histologically or cytologically documented squamous NSCLC.

• Stage IV mNSCLC (based on the American Joint Committee on Cancer Edition 8) not amenable to curative treatment.

• Absence of documented tumor genomic mutation results from tests conducted as part of standard local practice in any actionable driver oncogenes for which there are locally approved targeted 1L therapies.

• Provision of acceptable tumor sample to confirm tumor PD-L1 expression TC ≥ 1%.

• At least one lesion not previously irradiated that qualifies as a RECIST 1.1 TL at baseline and can be accurately measured at baseline as ≥ 10 mm in the longest diameter (except lymph nodes, which must have short axis ≥ 15 mm) with CT or MRI and is suitable for accurate repeated measurements.

• Adequate organ and bone marrow function.