A First-in-Human Study of D-0502 Alone and in Combination With Palbociclib in Women With Advanced or Metastatic ER-Positive and HER2-Negative Breast Cancer

Inclusion criteria

• Histologically-proven, ER-positive, HER2-negative locally advanced, inoperable, and/or metastatic breast cancer.
• Female patients with menopausal status:

i. Postmenopausal status defined as meeting at least one of the following criteria:

• Have undergone a bilateral oophorectomy any time in life;
• Age ≥60 years, or
• Age <60 years but have cessation of regular menses ≥12 months with follicle stimulating hormone (FSH) value >40 milli-international units per milliliter (mIU/mL) and an estradiol value <40 picograms per milliliter (pg/mL) (140 picomoles per liter [pmol/L]).

ii. Premenopausal or perimenopausal concurrently given a luteinizing hormone-releasing hormone (LHRH) agonist starting at least 4 weeks before the start of trial therapy and is planned to continue LHRH agonist during the study.

• Patients meeting all the following criteria:

• Has had at least 6 months of endocrine therapy for metastatic ER+ breast cancer prior to disease progression;
• Limited number of prior chemotherapy, endocrine therapy, and targeted therapy for advanced or metastatic disease
• Radiological or objective evidence of disease progression on or after the last systemic therapy prior to starting current study treatment.
• For phase Ia: Not eligible for standard therapy that would confer clinical benefit to the patient.

Exclusion criteria

• Patients with prior anticancer or investigational drug treatment within the following windows are excluded:
• Participants with prior anticancer or investigational drug treatment within the following windows are excluded:

• Any anti-cancer therapy (including endocrine therapy, chemotherapy, targeted therapy, etc.) less than 30 days before first dose of study treatment.
• Any investigational drug therapy less than 28 days or 4 half-lives (whichever is shorter) prior to first dose of study treatment.
• Patients with untreated or symptomatic or progressive central nervous system (CNS) metastases.

• Other protocol defined inclusion/exclusion criteria could apply