OncoMatch/Clinical Trials/NCT05696626
Evaluation of Lasofoxifene Combined With Abemaciclib Compared With Fulvestrant Combined With Abemaciclib in Locally Advanced or Metastatic ER+/HER2- Breast Cancer With an ESR1 Mutation
Is NCT05696626 recruiting? Yes, currently enrolling (Sep 2026). This Phase 3 trial studies multiple treatments including Lasofoxifene in combination with abemaciclib and Fulvestrant in combination with abemaciclib for metastatic breast cancer.
Treatment: Lasofoxifene in combination with abemaciclib · Fulvestrant in combination with abemaciclib — The goal of this clinical trial is to assess the efficacy, safety and tolerability of the combination of lasofoxifene and abemaciclib compared to fulvestrant and abemaciclib for the treatment of pre- and postmenopausal women and men who have previously received ribociclib or palbociclib-based treatment and have locally advanced or metastatic estrogen receptor positive (ER+)/human epidermal growth factor 2 negative (HER2-) breast cancer with an estrogen receptor 1 (ESR1) mutation. The main question the study aims to answer is: • To compare the efficacy of the combination of lasofoxifene and abemaciclib with that of fulvestrant and abemaciclib Participants will receive either receive 5 mg/d of oral lasofoxifene plus oral abemaciclib 150 mg twice a day or the combination of fulvestrant 500 mg intramuscular (IM) on Days 1, 15, and 29 and then once monthly thereafter plus oral abemaciclib 150 mg twice a day.
Check if I qualifyExtracted eligibility criteria
Treatments studied
Other
Cancer type
Breast Carcinoma
Biomarker criteria
Required: ESR1 point mutation in ligand binding domain
At least 1 or more ESR1 point mutations in the ESR1 ligand binding domain as assessed in cell-free ctDNA obtained from a blood or breast cancer tissue
Excluded: RB1 mutation
Known RB1 mutations or deletions that in the opinion of the investigator confer resistance to CDK4/6i. (Screening for RB1 mutation is not required for entry.)
Excluded: RB1 deletion
Known RB1 mutations or deletions that in the opinion of the investigator confer resistance to CDK4/6i. (Screening for RB1 mutation is not required for entry.)
Performance status
ECOG 0–1(Restricted strenuous activity)
Prior therapy
Must have received: aromatase inhibitor plus CDK4/6 inhibitor (palbociclib, ribociclib) — first hormonal treatment for metastatic disease
progression on an AI in combination with either palbociclib or ribociclib as their first hormonal treatment for metastatic disease
Cannot have received: abemaciclib (abemaciclib)
Prior progression of disease on abemaciclib
Cannot have received: fulvestrant (fulvestrant)
Prior progression of disease on fulvestrant
Cannot have received: selective estrogen receptor degrader
Prior progression of disease on other selective estrogen receptor degrader (SERD) therapy
Cannot have received: cytotoxic chemotherapy
Exception: subjects may have received 1 cytotoxic chemotherapy regimen in the metastatic disease setting prior to study entry, but must have recovered from chemotherapy acute toxicity excluding alopecia and Grade 2 peripheral neuropathy
Subjects may have received 1 cytotoxic chemotherapy regimen in the metastatic disease setting prior to study entry, but must have recovered from chemotherapy acute toxicity excluding alopecia and Grade 2 peripheral neuropathy
Lab requirements
Blood counts
Kidney function
Liver function
Structured fields extracted by AI. May contain errors — verify against the official protocol.
US trial sites
- Mayo Clinic - Scottsdale · Scottsdale, Arizona
- University of Arizona - Cancer Center · Tucson, Arizona
- Providence Medical Foundation - Santa Rosa, CA · Santa Rosa, California
- Mayo Clinic - Jacksonville · Jacksonville, Florida
- Miami Cancer Institute · Miami, Florida
Showing up to 5 US sites.
See all sites on ClinicalTrials.gov →Frequently asked questions
Is NCT05696626 currently recruiting?
Yes, this trial is currently recruiting patients.
Are there prior therapy exclusions?
Yes. Prior abemaciclib, fulvestrant, selective estrogen receptor degrader disqualifies patients from enrollment.
Does this trial require ESR1?
Yes, ESR1 point mutation in ligand binding domain is a required biomarker for enrollment.
Are patients with RB1 alterations eligible?
No. RB1 mutation is an exclusion criterion.
Are patients with RB1 alterations eligible?
No. RB1 deletion is an exclusion criterion.
Could you qualify for this trial?
Enter your biomarker results to see how this trial's eligibility criteria match your specific cancer profile.
Check if I qualifyRelated pages