Inclusion criteria :

          -  18 years or older.

          -  Histological or cytological diagnosis of adenocarcinoma of the breast.

          -  Locally advanced not amenable to radiation therapy or surgery in a curative intent,
             and/or metastatic disease.

          -  ER positive status.

          -  HER2 negative status.

          -  Participants must have received no more than 1 prior chemotherapeutic or 1 targeted
             therapy regimen for advanced/metastatic disease.

          -  In the main study, a prior treatment with a CDK 4/6 inhibitor is mandatory if this
             treatment is approved and can be reimbursed for this participant. The percentage of
             participants without previous CDK 4/6 inhibitor will be capped to 20%. In the Chinese
             extension cohort, previous treatment with a CDK 4/6 inhibitor will not be mandatory,
             and there will be no limitation to the number of participants naïve to CDK4/6
             inhibitor.

          -  Participants must present a secondary endocrine resistance to endocrine therapy
             defined as: progression while on endocrine therapy after at least 6 months of
             treatment for advanced breast cancer, or relapse while on adjuvant endocrine therapy
             but after the first 2 years, or with a relapse within 12 months after completing
             adjuvant endocrine therapy.

          -  Male or Female.

        Exclusion criteria:

          -  Eastern Cooperative Oncology Group performance status ≥2.

          -  Medical history or ongoing gastrointestinal disorders potentially affecting the
             absorption of amcenestrant. Participants unable to swallow normally and to take
             capsules.

          -  Participant with any other cancer. Adequately treated basal cell or squamous cell skin
             cancer or in situ cervical cancer or any other cancer from which the participant has
             been disease free for >3 years are allowed.

          -  Severe uncontrolled systemic disease at screening .

          -  Participants with known brain metastases that are untreated, symptomatic or require
             therapy to control symptoms.

          -  Prior treatment with mammalian target of rapamycin inhibitors or any other selective
             estrogen receptor degrader (SERD) compound, except fulvestrant if stopped for at least
             3 months before randomization.

          -  Treatment with drugs that have the potential to inhibit UGT less than 2 weeks before
             randomization.

          -  Treatment with strong CYP3A inducers within 2 weeks before randomization.

          -  Ongoing treatment with drugs that are substrate of P-glycoprotein (P gp) (dabigatran,
             digoxin, fexofenadine), or of Breast Cancer Resistance Protein (BCRP) (rosuvastatin,
             sulfasalazine).

          -  Treatment with anticancer agents (including investigational drugs) less than 3 weeks
             before randomization.

          -  Inadequate hematological, coagulation, renal and liver functions.

        The above information is not intended to contain all considerations relevant to a patient's
        potential participation in a clinical trial.