This Phase 3 clinical study compares the efficacy and safety of elacestrant to the standard of care (SoC) options of fulvestrant or an aromatase inhibitor (AI) in women and men with breast cancer whose disease has advanced on at least one endocrine therapy including a CDK4/6 inhibitor in combination with fulvestrant or an aromatase inhibitor (AI) .



Eligible Ages
Over 18 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  1. Subjects with proven diagnosis of adenocarcinoma of the breast with evidence of either locally advanced disease not amenable to resection or radiation therapy with curative intent or metastatic disease not amenable to curative therapy. 2. Subjects must be appropriate candidates for endocrine monotherapy 3. Subjects must have measurable disease or, nonmeasurable (evaluable) bone-only disease 4. Female or male subjects age ≥ 18 years; female subjects must be postmenopausal women and male subjects must not allow pregnancy with their sperm (abstain, do not donate sperm, etc). 5. Subjects must have ER+/HER2-tumor status 6. Subjects must have previously received at least one and no more than two lines of endocrine therapy for advanced/metastatic breast cancer and meet additional previous treatment criteria. 7. Subjects must have received prior treatment with a CDK4/6 inhibitor in combination with either fulvestrant or an aromatase inhibitor (AI). 8. Subjects may have received no more than one line of chemotherapy in the advanced/metastatic setting. 9. Subjects must have ctDNA ESR1-mut or ESR1-WT status as determined by central testing before subject is randomized. Critical

Exclusion Criteria

  1. Prior treatment with elacestrant, GDC-0810, GDC-0927, GDC-9545, LSZ102, AZD9496, bazedoxifene, or other investigational SERD or investigational ER antagonist. 2. Prior anticancer or investigational drug treatment within the following windows: 1. Fulvestrant treatment < 28 days before first dose of study drug 2. Any endocrine therapy < 14 days before first dose of study drug (with the exception of GnRH agonist therapy in male subjects) 3. Chemotherapy < 21 days before first dose of study drug 4. Any investigational anti-cancer drug therapy < 28 days or five half-lives (whichever is shorter) before the first dose of study drug. Enrollment of subjects whose most recent therapy was an investigational agent should be discussed with the Sponsor 3. Presence of symptomatic visceral disease as defined in protocol.

Study Design

Phase 3
Study Type
Intervention Model
Parallel Assignment
Primary Purpose
None (Open Label)

Arm Groups

ArmDescriptionAssigned Intervention
Subjects in Arm 1 will receive elacestrant
  • Drug: Elacestrant
    400 mg/day once daily oral dosing
    Other names:
    • RAD1901
Active Comparator
Standard of Care (SoC)
Subjects in Arm 2 will receive Investigator's choice of one of the Standard of Care drugs (fulvestrant, anastrozole, letrozole, or exemestane)
  • Drug: Standard of Care
    Fulvestrant: 500 mg administered intramuscularly (IM) into the buttocks as two 5 mL injections on C1D1, C1D15 and C2D1 and Day 1 of every subsequent 28-day cycle Anastrozole 1 mg/day on a continuous dosing schedule Letrozole: 2.5 mg/day on a continuous dosing schedule Exemestane: 25 mg/day on a continuous dosing schedule
    Other names:
    • Faslodex, Arimidex, Femara, Aromasin

More Details

Active, not recruiting
Radius Pharmaceuticals, Inc.

Study Contact

Detailed Description

This is an international, multicenter, randomized, open-label, active-controlled, event-driven, Phase 3 clinical study comparing the efficacy and safety of elacestrant to the SoC options of fulvestrant or an aromatase inhibitor (AI) in postmenopausal women and in men with advanced or metastatic ER+/HER2- breast cancer, either in subjects with tumors that harbor mutations in the ligand binding domain (LBD) of the estrogen receptor 1 (ESR1) gene (ESR1-mut subjects) or in all subjects regardless of ESR1 status (ESR1-mut and ESR1 wild type [ESR1-WT]) and whose disease has relapsed or progressed on at least one and no more than two prior lines of endocrine therapy (with documented progression), which must have included prior CDK4/6 inhibitor therapy in combination with fulvestrant or an aromatase inhibitor (AI) and for whom hormonal monotherapy with one of the SoC drugs (fulvestrant, anastrozole, letrozole, exemestane) is an appropriate treatment option.


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.