The primary objective of the study is to measure efficacy of saruparib (AZD5305) plus camizestrant compared with physician's choice CDK4/6i plus ET in patients with BRCA1, BRCA2, or PALB2m, HR-positive, HER2-negative (defined as IHC 0, 1+, 2+/ ISH non-amplified) advanced breast cancer
Adult females, pre/peri-menopausal and/or post-menopausal, and adult males
Histologically or cytologically documented diagnosis of HR-positive, HER2-negative breast cancer
Advanced breast cancer with either locally advanced disease not amenable to curative treatment or metastatic disease
ECOG performance status of 0 or 1 with no deterioration over the previous 2 weeks
Participants with history of MDS/AML or with features suggestive of MDS/AML
Participants with any known predisposition to bleeding
Any history of persisting severe cytopenia
Any evidence of severe or uncontrolled systemic diseases or active uncontrolled infections