Phase III
Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer
- Study IRB#:2000041648
- Last Updated:10/15/2026
This phase 3 clinical trial compares the efficacy and safety of palazestrant with ribociclib to letrozole and ribociclib in women and men who have not received prior systemic anti-cancer treatment for advanced breast cancer.
Contact Us
For more information about this study, including how to volunteer, contact:
Carl Brown
Help Us Discover!
You can help our team find trials you might be eligible for by creating a volunteer profile in MyChart. To get started, create a volunteer profile, or contact helpusdiscover@yale.edu, or call 877-978-8343 for more information.
Study Locations
- Smilow Cancer Hospital at Greenwich (CT112)
- Smilow Cancer Hospital Care Center - Derby (CT114)
- Smilow Cancer Hospital Care Center - Fairfield (CT127)
- Smilow Cancer Hospital Care Center - Guilford (CT078)
- Smilow Cancer Hospital Care Center - Long Ridge (CT134)
- Smilow Cancer Hospital Care Center - North Haven (CT125)
- Smilow Cancer Hospital Care Center - Torrington (CT043)
- Smilow Cancer Hospital Care Center - Trumbull (CT053)
- Smilow Cancer Hospital Care Center - Waterbury (CT079)
- Smilow Cancer Hospital Care Center - Waterford (CT126)
Eligibility Criteria
Inclusion Criteria
- Adult female or male participants.
- ER+, HER2- locally advanced or metastatic breast cancer that is not amenable to curative therapy.
- Evaluable disease (measurable disease per RECIST 1.1 or bone-only disease).
- De novo advanced breast cancer or with disease recurrence occurring after 12 months of completing adjuvant endocrine therapy (with or without CDK4/6 inhibitors)
- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
- Adequate hematologic, hepatic, and renal functions.
- Female participants can be pre-, peri- or postmenopausal.
- Male and pre- or peri-menopausal female participants must be willing to take a GnRH (or LHRH) agonist.
Exclusion Criteria
- Disease recurrence during adjuvant endocrine therapy
- Currently receiving or previously received systemic anti-cancer therapy for ER+, HER2- advanced breast cancer.
- Previously received treatment with fulvestrant, elacestrant or an investigational endocrine therapy in any setting.
- History of allergic reactions to study treatment.
- Any contraindications to letrozole and ribociclib.
- Symptomatic central nervous system metastases, carcinomatous meningitis, leptomeningeal disease, or a spinal cord compression that require immediate treatment.
