A study to investigate camizestrant in combination with atirmociclib in participants with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer previously treated with a cyclin dependent kinase 4/6 (CDK4/6) inhibitor.
Participants with advanced adenocarcinoma of the breast and must have received prior adequate therapy in accordance with local practice for their tumor type and stage of disease.
Metastatic or locoregionally recurrent disease and radiological or objective evidence of progression on or after the last systemic therapy prior to starting investigational medicinal products.
Eastern cooperative oncology group (ECOG)/World Health Organization (WHO) performance status 0 to 1, and a minimum life expectancy of 12 weeks.
At least one lesion that is measurable and/or non-measurable, as per RECIST 1.1 and that can be accurately assessed at baseline and is suitable for repeated assessment by computed tomography (CT), magnetic resonance imaging (MRI), or plain X-ray, or clinical examination.
A participant who has received 2 or more lines of CDK4/6 inhibitors in the advanced disease setting.
A participant who has received prior camizestrant or atirmociclib treatment in the advanced disease setting.
Patients previously treated with other next generation selective estrogen receptor degrader (SERDs) or other experimental ETs in the advanced disease setting.
Patients previously treated with other experimental cyclin-dependent kinase (CDK) inhibitors are not eligible.