• Histologically or cytologically documented locally recurrent inoperable, which cannot be treated with curative intent, or metastatic TNBC, as defined by the ASCO-CAP guidelines.

• ECOG PS 0 or 1.

• Participants are expected to provide an FFPE tumour sample collected from a locally recurrent inoperable or metastatic tumour. If no such sample is available, an archival FFPE tumour sample can be submitted; it must have been collected ≤ 3 years prior to the participant signing informed consent (screening start).

• PD-L1 positive TNBC based on results from an appropriately validated investigational PD-L1 (22C3) assay (CPS ≥ 10) from a sponsor designated central laboratory.

• No prior chemotherapy or other systemic anti-cancer therapy for metastatic or locally recurrent inoperable breast cancer.

• \- Patients with recurrent disease will be eligible if they have completed treatment for Stage I-III breast cancer, if indicated, and ≥6 months have elapsed between completion of treatment with curative intent and the first documented recurrence.

• Eligible for one of the chemotherapy options listed as ICC (paclitaxel, nab-paclitaxel, or gemcitabine + carboplatin).

• Measurable disease as per RECIST 1.1.

• Adequate bone marrow reserve and organ function.

• Male and female participants of childbearing potential must agree to use protocol-specified method(s) of contraception.