Phase 1b Study of OP-1250 (Palazestrant) in Combination With Ribociclib, Alpelisib, Everolimus, or Atirmociclib in ER+, HER2- Breast Cancer

Inclusion Criteria

• •Female or male aged \>18 years.
• •Willing and able to participate and comply with all study requirements.
• •Histologically- or cytologically-confirmed advanced or metastatic Breast Cancer (mBC).
• •ER+/HER2- disease, as determined in the most recently obtained archival tumor tissue sample from a metastatic site, using locally accepted criteria by the local pathology report.
• •Evaluable disease with one of the following: Measurable disease, ie, at least 1 measurable lesion as per RECIST 1.1 (a lesion at a previously irradiated site may only be counted as a target lesion if there is clear sign of progression since the irradiation) OR patients with predominantly bone disease (with or without other non-measurable lesions) are allowed if it is possible to evaluate on radiological examinations (eg. bone scan, PET/CT, CT, MRI) even if lesions are non-measurable according to RECIST 1.1.
• •Life expectancy ≥6 months, as judged by the investigator.
• •Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1.
• •Has received no more than 1 prior hormonal regimen (Treatment Group 1). Has received no more than 2 prior hormonal regimens (Treatment Group 2 and Treatment Group 3) . Has received no more than 2 prior hormonal regimens for metastatic disease in Part 1 (Dose Escalation) and no more than 1 prior hormonal regimes in Part 2 (Dose Expansion) for metastatic disease, regardless of type of endocrine agent (Treatment Group 4) for advanced or metastatic disease. Prior hormonal regimens in combination with CDK4/6 inhibitors are allowed in all treatment groups. For subjects in Treatment Group 4, no prior chemotherapy for metastatic breast cancer is allowed.
• •Has received no more than 1 prior chemotherapy (which includes antibody drug conjugates) for locally advanced or metastatic breast cancer.