Phase 1 / 2 Study of SAR439859 Single Agent and in Combination With Palbociclib in Postmenopausal Women With Estrogen Receptor Positive Advanced Breast Cancer

Duration of the study, per patient, will include eligibility period (screening period) of up
to 4 weeks (28 days), treatment period (at least 1 cycle [28 days] of study treatment), and
end of treatment (EOT) visit after the last study treatment administration (i.e. at least 30
days post last treatment or until the patient receives another anticancer therapy, whichever
is earlier). The expected enrollment period is approximately 26 months.

Inclusion criteria:

Parts A, B, C and D:

- Patients must be postmenopausal women

- Histological diagnosis of breast adenocarcinoma

- Locally advanced or metastatic disease

- Measurable disease

- Previously treated for advanced disease

- Either primary tumor or any metastatic site to be positive for Estrogen Receptors
(ER+) and negative for human epidermal growth factor receptor 2 (HER2-) by
immunohistochemistry (IHC)

Exclusion criteria:

- Medical history or ongoing gastrointestinal disorders that could affect absorption of
SAR439859 and/or palbociclib (including difficulties with swallowing capsules)

- Patient with any other cancer (except for adequately treated basal cell or squamous
cell skin cancer, in situ cervical cancer or any other cancer from which the patient
has been disease free for >3 years)

- Patients with known brain metastases and endometrial disorders

- Treatment with anticancer agents (including investigational drugs) less than 2 weeks
before first study treatment starts (less than 4 weeks if the anticancer agents were
antibodies)

- Prior treatment with another selective ER down-regulator (SERD) (except fulvestrant)

- Inadequate hematological and biochemical lab tests

- Patients with Gilbert disease

- Treatment with human immunodeficiency virus (HIV)-antiviral, antifungal and
antioxidant agents less than 2 weeks before study treatment starts

- Treatment with strong and moderate CYP3A inducers/inhibitors within 2 weeks before
first study treatment

Part A only:

- Patients with liver metastases only

Parts C and D only:

- Prior therapy with any selective cyclin-dependent kinase (CDK) 4/6 inhibitor

- Treatment with strong and moderate CYP3A inducers or strong CYP3A inhibitors within 2
weeks before first study treatment starts

- Medical conditions requiring concomitant medications that are metabolized by CYP3A

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