A Phase-3, Open-Label, Randomized Study of Dato-DXd Versus Investigator's Choice of Chemotherapy (ICC) in Participants With Inoperable or Metastatic HR-Positive, HER2-Negative Breast Cancer Who Have Been Treated With One or Two Prior Lines of Systemic Chemotherapy (TROPION-Breast01)

Inclusion Criteria Age • Participant must be ≥ 18 years at the time of screening. Type of Participant and Disease Characteristics * Inoperable or metastatic HR+, HER2-negative breast cancer * Progressed on and not suitable for endocrine therapy per investigator assessment and treated with 1 to 2 lines of prior chemotherapy in the inoperable/metastatic setting. Participant must have documented progression on their most recent line of chemotherapy. * Eligible for one of the chemotherapy options listed as ICC (eribulin, capecitabine, vinorelbine, gemcitabine), per investigator assessment. * ECOG PS of 0 or 1, with no deterioration over the previous 2 weeks prior to day of first dosing. * At least 1 measurable lesion not previously irradiated that qualifies as a RECIST 1.1. Note: Participants with bone-only metastases are not permitted. * Participants with a history of previously treated neoplastic spinal cord compression, or clinically inactive brain metastases, who require no treatment with corticosteroids or anticonvulsants, may be included in the study, if they have recovered from the acute toxic effect of radiotherapy. A minimum of 2 weeks must have elapsed between the end of radiotherapy and study enrolment. * Adequate organ and bone marrow function within 7 days before day of first dosing as follows: * Hemoglobin: ≥ 9.0 g/L. * Absolute neutrophil count: 1500/mm3. * Platelet count: 100000/mm3. • Total bilirubin: ≤ 1.5 × ULN if no liver metastases; or ≤ 3 × ULN in …