A Phase III Study of Dato-DXd With or Without Durvalumab Compared With Investigator's Choice of Chemotherapy in Combination With Pembrolizumab in Patients with PD-L1 Positive Locally Recurrent Inoperable or Metastatic Triple-negative Breast Cancer

Prior treatment

• As judged by the investigator, severe or uncontrolled systemic diseases, uncontrolled hypertension, serious gastrointestinal conditions associated with diarrhoea, chronic diverticulitis or previous complicated diverticulitis, history of allogeneic organ transplant, and active bleeding diseases, ongoing or active infection, significant cardiac conditions, substance abuse, psychiatric illness/social situation, or psychological conditions.
• Active or prior documented autoimmune or inflammatory disorders
• Prior exposure to any treatment including ADC containing a chemotherapeutic agent targeting topoisomerase I and TROP2-targeted therapy
• Any concurrent anti-cancer treatment
• History of another primary malignancy except for malignancy treated with curative intent with no known active disease within 2 years before Cycle 1 Day 1 and of low potential risk for recurrence.
• Neoplastic spinal cord compression or active brain metastases, leptomeningeal carcinomatosis or history of leptomeningeal carcinomatosis. Participants with a history of previously treated neoplastic spinal cord compression or treated, clinically inactive brain metastases that are no longer symptomatic, who require no treatment with corticosteroids or anticonvulsants, may be included in the study if they have recovered from acute toxic effects of radiotherapy.

Other illness

• Clinically significant corneal disease
• Participants with a known severe hypersensitivity to PD-1/PD-L1 inhibitors or Dato-DXd
• Uncontrolled infection requiring IV antibiotics, antivirals or antifungals
• Active or uncontrolled hepatitis B or C virus infection
• Known HIV infection that is not well controlled
• Uncontrolled or significant cardiac disease
• History of non-infectious ILD/pneumonitis (including radiation pneumonitis) that required steroids, current ILD/pneumonitis, or suspected ILD/pneumonitis that cannot be ruled out by imaging at screening

Other

• Currently pregnant (confirmed with positive pregnancy test), breastfeeding or planning to become pregnant
• Clinically severe pulmonary function compromise.

• Histologically or cytologically documented locally recurrent inoperable, which cannot be treated with curative intent, or metastatic TNBC, as defined by the the ASCO-CAP guidelines
• ECOG PS 0 or 1
• Participants are expected to provide a FFPE tumour sample collected from a locally recurrent inoperable or metastatic tumour (either de novo metastatic or recurrent metastatic, excluding bone metastases). Alternatively, an archival FFPE tumour sample can be submitted. This archival sample may come from early-stage TNBC; however, 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 inoperable local recurrence or distant 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