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 (ELAINEIII)

April 16, 2026 updated by: LeonaBio

An Open Label, Randomized, Multicenter Study Comparing the Efficacy and Safety of the Combination of Lasofoxifene and Abemaciclib to the Combination of Fulvestrant and Abemaciclib for the Treatment of Pre- and Postmenopausal Women and Men With Locally Advanced or Metastatic ER+/HER2- Breast Cancer With an ESR1 Mutation

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

500

Phase

  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Simon Daggett - Senior Vice President, Clinical Operations
  • Phone Number: (425) 620-8772 (909) 374-3793
  • Email: clinicaltrials@leonabio.com

Study Locations

  • Australia
  • Belgium
  • Canada
    • Ontario
      • Ottawa, Ontario, Canada
        • Recruiting
        • The Ottawa General Hospital
        • Contact:
      • Toronto, Ontario, Canada
        • Recruiting
        • Sunnybrook Health Sciences Centre -Bayview Campus
        • Contact:
    • Quebec
      • Montreal, Quebec, Canada
      • Montreal, Quebec, Canada
      • Saguenay, Quebec, Canada
        • Withdrawn
        • CIUSSS du Saguenay-Lac-Saint-Jean
  • China
      • Anhui, China
        • Recruiting
        • Anhui Provincial Cancer Hospital
        • Contact:
      • Anyang, China
      • Beijing, China
        • Recruiting
        • Peking Union Medical College Hospital
        • Contact:
      • Beijing, China
      • Bengbu, China
        • Recruiting
        • The First Affiliated Hospital of Bengbu Medical University
        • Contact:
      • Changchun, China
        • Recruiting
        • The First Hospital of Jilin University
        • Contact:
      • Changsha, China
        • Recruiting
        • The second Xiangya Hospital of Central South University
        • Contact:
      • Chengdu, China
        • Recruiting
        • Sichuan Provincial People's Hospital
        • Contact:
      • Chengdu, China
        • Recruiting
        • West China Hospital, Sichuan University
        • Contact:
      • Chongqicun, China
        • Recruiting
        • The First Affiliated Hospital, Chongqing Medical University
        • Contact:
      • Dalian, China
        • Recruiting
        • The Second Hospital of Dalian Medical University
        • Contact:
      • Deyang, China
        • Recruiting
        • Deyang People's Hospital
        • Contact:
      • Fuyang, China
        • Recruiting
        • Fuyang Cancer Hosptial
        • Contact:
      • Fuzhou, China
        • Recruiting
        • Fujian Cancer Hospital
        • Contact:
      • Fuzhou, China
        • Recruiting
        • Fujian Medical University Union Hospital
        • Contact:
      • Guandong, China
        • Recruiting
        • Zhujiang Hospital of Nanfang Medical University
        • Contact:
      • Guangdong, China
        • Recruiting
        • Guangdong Provincial People's Hospital
        • Contact:
      • Guangdong, China
        • Recruiting
        • Meizhou People's hospital
        • Contact:
      • Guangdong, China
        • Recruiting
        • Peking University Shenzhen Hospital
        • Contact:
          • Xiaoling Liu
      • Guangdong, China
        • Recruiting
        • Sun Yat-Sen University- Cancer Center
        • Contact:
      • Guangzhou, China
        • Recruiting
        • Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University
        • Contact:
      • Haikou, China
        • Recruiting
        • The First Affiliated Hospital of Hainan Medical University
        • Contact:
      • Hangzhou, China
        • Recruiting
        • The First Affiliated Hospital, College of Medicine, Zhejiang University
        • Contact:
      • Hangzhou, China
        • Recruiting
        • Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University
        • Contact:
      • Hangzhou, China
        • Recruiting
        • Zhejiang Provincial Hospital of Chinese Medicine
        • Contact:
      • Hebei, China
        • Recruiting
        • Hebei Medical University - The Fourth Hospital - Hebei Provincial Tumor Hospital
        • Contact:
      • Hubei, China
        • Recruiting
        • Xiangyang Central Hospital
        • Contact:
      • Hunan, China
        • Recruiting
        • Xiangya Hospital Central South University
        • Contact:
      • Jieyang, China
        • Recruiting
        • Jieyang People's Hospital
        • Contact:
      • Jinan, China
        • Recruiting
        • Shandong Province Tumor Hospital
        • Contact:
      • Kunming, China
      • Lanzhou, China
        • Recruiting
        • The First Hospital of Lanzhou University
        • Contact:
      • Lanzhou, China
        • Recruiting
        • Gansu Provincial Hospital
        • Contact:
      • Linyi, China
        • Recruiting
        • Linyi Cancer Hospital
        • Contact:
      • Luoyang, China
        • Recruiting
        • The first affiliated hospital of Henan University of science and technology
        • Contact:
      • Luoyang, China
        • Recruiting
        • Luoyang Central Hospital
        • Contact:
      • Luzhou, China
        • Recruiting
        • The Affiliated Hospital of Southwest Medical University (Luzhou Medical College)
        • Contact:
      • Nanchang, China
        • Recruiting
        • Jiangxi Cancer Hospital
        • Contact:
      • Nanchang, China
        • Recruiting
        • Nanchang People's Hospital
        • Contact:
      • Nanjing, China
        • Recruiting
        • Nanjing Drum Tower Hospital
        • Contact:
      • Nanjing, China
        • Recruiting
        • Jiangsu Province Hospital - The First Affiliated Hospital with Nanjing Medical University
        • Contact:
      • Nanning, China
        • Recruiting
        • Guangxi Medical University Cancer Hospital
        • Contact:
      • Nanyang, China
        • Recruiting
        • Nanyang Central Hospital
        • Contact:
      • Neijiang, China
        • Recruiting
        • The Second People's Hospital of Neijiang
        • Contact:
      • Ningbo, China
        • Recruiting
        • Ningbo Medical Center Li Huili Hospital
        • Contact:
      • Pingdingshan, China
        • Recruiting
        • The First People'S Hospital of Ping Ding Shan
        • Contact:
      • Qingdao, China
        • Recruiting
        • The Affiliated Hospital of Qingdao University
        • Contact:
      • Qingdao, China
        • Recruiting
        • Qingdao Central Hospital, University of Health and Rehabilitation Sciences
        • Contact:
      • Quanzhou, China
        • Recruiting
        • Quanzhou First Hospital
        • Contact:
      • Shanghai, China
        • Recruiting
        • Huashan Hospital, Fudan University
        • Contact:
      • Shanghai, China
        • Recruiting
        • Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine
        • Contact:
      • Shang’ai, China
        • Recruiting
        • Fudan University Cancer Center
        • Contact:
      • Shanxi, China
        • Recruiting
        • First Affiliated Hospital of Xi'an JiaoTong University
        • Contact:
      • Shaoyang, China
        • Recruiting
        • The Central Hospital of Shaoyang
        • Contact:
      • Shenyang, China
        • Recruiting
        • Liaoning Cancer Hospital & Institute
        • Contact:
      • Shouguang, China
        • Recruiting
        • Yuebei People's Hospital
        • Contact:
      • Sichuan, China
        • Recruiting
        • University of Electonic Science & Technology (UESTC) - Sichuan Cancer Hospital & Institute
        • Contact:
      • Tianjin, China
        • Recruiting
        • Tianjin Medical University Cancer Institute & Hospital
        • Contact:
      • Tianjin, China
        • Recruiting
        • Tianjin Cancer hospital Airport hospital
        • Contact:
      • Wenzhou, China
        • Recruiting
        • The First Affiliated Hospital of Wenzhou Medical University
        • Contact:
      • Wuhan, China
        • Recruiting
        • Hubei Cancer Hospital
        • Contact:
      • Wuhan, China
        • Recruiting
        • Union Hospital Tongji Medical College Huazhong University of Science and Technolog
        • Contact:
      • Wuhu, China
        • Recruiting
        • The Second People's Hospital of WuHu
        • Contact:
      • Xi Ail, China
        • Recruiting
        • The First Affiliated Hospital of Air Force Medical University
        • Contact:
      • Xiamen, China
        • Recruiting
        • The First Affiliated Hospital of Xiamen University
        • Contact:
      • Xiamen, China
        • Recruiting
        • Zhongshang Hospital Xiamen University
        • Contact:
      • Xinzheng, China
        • Recruiting
        • The Second Affiliated Hospital of Xi'an Jiaotong University
        • Contact:
      • Xuzhou, China
        • Recruiting
        • The Affiliated Hospital of Xuzhou Medical University
        • Contact:
      • Xuzhou, China
        • Recruiting
        • Xuzhou Central Hospital
        • Contact:
      • Yuncheng, China
        • Recruiting
        • Yuncheng Central Hospital
        • Contact:
      • Zhejiang, China
        • Recruiting
        • Zhejiang Cancer Hospital
        • Contact:
      • Zhejiang, China
        • Recruiting
        • Zhejiang Provincial People's Hospital
        • Contact:
      • Zhengzhou, China
        • Recruiting
        • Henan Cancer Hospital
        • Contact:
      • Zhengzhou, China
        • Recruiting
        • The First Affiliated Hospital of Zhengzhou University
        • Contact:
      • Zhongshan, China
        • Recruiting
        • Zhongshan City People's Hospital
        • Contact:
      • Zhumadian, China
        • Recruiting
        • Zhumadian Central Hospital
        • Contact:
      • Ürümqi, China
        • Recruiting
        • The Affiliated Cancer Hospital of Xinjiang Medical University
        • Contact:
  • France
  • Germany
      • Dresden, Germany
      • München, Germany
        • Recruiting
        • Klinikum rechts der Isar der Technischen Universitaet Muenchen
        • Contact:
  • Israel
  • Italy
  • Poland
      • Biała Podlaska, Poland
        • Withdrawn
        • KO - MED Centra Kliniczne Sp. z o.o., Wojewodzki Szpital Specjalistyczny w Bialej Podlaskiej
      • Gliwice, Poland
        • Not yet recruiting
        • Narodowy Instytut Onkologii im. Marii Sklodowskiej-Curie - Panstwowy Instytut Badawczy, Oddzial w Gliwicach, I Klinika Radioterapii i Chemioterapii
        • Contact:
      • Krakow, Poland
        • Recruiting
        • Szpital Specjalistyczny im. Ludwika Rydygiera w Krakowie - Oddzial Onkologii Klinicznej z Pododdzialem Dziennym
        • Contact:
      • Krakow, Poland
      • Lodz, Poland
        • Completed
        • Instytut Centrum Zdrowia Matki Polki - Klinika Onkologii
      • Poznan, Poland
        • Not yet recruiting
        • Wielkopolskie Centrum Onkologii (WCO) / The Greater Poland Cancer Center
        • Contact:
      • Poznan, Poland
        • Recruiting
        • Uniwersytecki Szpital Kliniczny w Poznaniu, Oddzial Chemioterapii
        • Contact:
      • Wieliszew, Poland
  • Romania
      • Bucharest, Romania
        • Withdrawn
        • Centrul Medical Focus
      • Bucharest, Romania
        • Not yet recruiting
        • Memorial Healthcare International SRL
        • Contact:
      • Cluj-Napoca, Romania
      • Craiova, Romania
        • Recruiting
        • Oncology Center Sfantul Nectarie
        • Contact:
      • Craiova, Romania
        • Completed
        • Onco Clinic Consult SA
      • Piteşti, Romania
      • Timișoara, Romania
        • Recruiting
        • OncoMed Oncology Center
        • Contact:
  • Singapore
  • South Korea
      • Gyeonggi-do, South Korea
        • Recruiting
        • National Cancer Center
        • Contact:
      • Jeollanam-do, South Korea, 58128
        • Recruiting
        • Chonnam National University Hwasun Hospital
        • Contact:
      • Seoul, South Korea
        • Recruiting
        • Korea University Anam Hospital
        • Contact:
      • Seoul, South Korea
        • Not yet recruiting
        • Severance Hospital, Yonsei University Health System
        • Contact:
      • Seoul, South Korea
        • Not yet recruiting
        • Asan Medical Center
        • Contact:
  • Spain
      • Barcelona, Spain
        • Recruiting
        • Hospital Universitario Vall d'Hebron
        • Contact:
      • Barcelona, Spain
      • Córdoba, Spain
        • Recruiting
        • Hospital Universitario Reina Sofia
        • Contact:
      • Madrid, Spain, 28034
        • Recruiting
        • Hospital Universitario Ramon y Cajal
        • Contact:
      • Madrid, Spain
        • Recruiting
        • Hospital Universitario 12 de Octubre
        • Contact:
      • Madrid, Spain
        • Recruiting
        • Hospital General Universitario Gregorio Marañon
        • Contact:
      • Madrid, Spain
      • Madrid, Spain
        • Recruiting
        • Clinica Universidad de Navarra - Madrid
        • Contact:
      • Madrid, Spain
        • Recruiting
        • Hospital Beata Maria Ana
        • Contact:
      • Madrid, Spain, 28040
      • Málaga, Spain
      • Pamplona, Spain
        • Recruiting
        • Clinica Universidad de Navarra - Pamplona
        • Contact:
      • Valencia, Spain
        • Recruiting
        • Instituto Valenciano de Oncologia
        • Contact:
  • Taiwan
      • Changhua, Taiwan
        • Recruiting
        • Changhua Christian Hospital (CCH)
        • Contact:
      • Kaohsiung City, Taiwan
        • Recruiting
        • Kaohsiung Medical University Chung-Ho Memorial Hospital (KMUH)
        • Contact:
      • Tainan, Taiwan
        • Recruiting
        • National Cheng Kung University Hospital
        • Contact:
      • Taipei, Taiwan
        • Recruiting
        • National Taiwan University Hospital
        • Contact:
      • Taipei, Taiwan
        • Recruiting
        • Tri-Service General Hospital
        • Contact:
      • Taipei, Taiwan
        • Recruiting
        • Koo Foundation Sun Yat-Sen Cancer Center
        • Contact:
      • Taoyuan, Taiwan
  • Turkey (Türkiye)
      • Ankara, Turkey (Türkiye)
        • Not yet recruiting
        • Ankara University Medical Faculty Medical Oncology Department
        • Contact:
      • Bursa, Turkey (Türkiye)
        • Not yet recruiting
        • Uludag University Faculty of Medicine Hospital
        • Contact:
      • Edirne, Turkey (Türkiye)
      • Izmir, Turkey (Türkiye)
    • Ankara
      • Çankaya, Ankara, Turkey (Türkiye)
    • Istanbul
      • Kadiköy, Istanbul, Turkey (Türkiye)
        • Recruiting
        • Goztepe Prof. Dr. Suleyman Yalcin City Hospital
        • Contact:
      • Çapa, Istanbul, Turkey (Türkiye)
        • Not yet recruiting
        • Istanbul University CAPA Medical Faculty
        • Contact:
    • Kocaeli
    • İzmir
      • Bornova, İzmir, Turkey (Türkiye)
        • Not yet recruiting
        • Ege University Medical Faculty Hospital
        • Contact:
      • Konak, İzmir, Turkey (Türkiye)
        • Not yet recruiting
        • Suat Seren Training and Research Hospital
        • Contact:
  • United Kingdom
      • Cardiff, United Kingdom, CF14 2TL
        • Not yet recruiting
        • Velindre Cancer Center
        • Contact:
          • Simon Waters
      • Harlow, United Kingdom, CM20 1QX
        • Recruiting
        • Princess Alexandra Hospital - Harlow
        • Contact:
      • Leeds, United Kingdom
      • London, United Kingdom
        • Recruiting
        • Charing Cross Hospital
        • Contact:
      • London, United Kingdom, NW3 2
        • Not yet recruiting
        • Royal Free London NHS Foundation Trust
        • Contact:
      • Manchester, United Kingdom
      • Milton Keynes, United Kingdom, MK6 5LD
      • Nottingham, United Kingdom
      • Stockton-on-Tees, United Kingdom, TS198PE
        • Withdrawn
        • University Hospital of North Tees
  • United States
    • Arizona
      • Scottsdale, Arizona, United States, 85259
        • Recruiting
        • Mayo Clinic - Scottsdale
        • Contact:
          • Clinical Trials Office - All Mayo Clinic Locations
          • Phone Number: 855-776-0015
      • Tucson, Arizona, United States, 85719
    • California
      • Santa Rosa, California, United States, 95403
    • Florida
      • Jacksonville, Florida, United States, 32224
        • Recruiting
        • Mayo Clinic - Jacksonville
        • Contact:
          • Clinical Trials Office - All Mayo Clinic Locations
          • Phone Number: 855-776-0015
      • Miami, Florida, United States, 33143
      • Plantation, Florida, United States, 33324
    • Georgia
      • Atlanta, Georgia, United States, 30322
    • Kentucky
    • Maryland
      • Baltimore, Maryland, United States, 21231
        • Recruiting
        • Johns Hopkins Kimmel Cancer Center
        • Contact:
    • Massachusetts
      • Boston, Massachusetts, United States, 02114
      • Boston, Massachusetts, United States, 02215
      • Boston, Massachusetts, United States, 02115
    • Michigan
      • Grand Rapids, Michigan, United States, 49503
        • Recruiting
        • Cancer and Hematology Centers of Western Michigan
        • Contact:
    • Minnesota
      • Minneapolis, Minnesota, United States, 55407
        • Recruiting
        • Allina Health System DBA Virginia Piper Cancer Institute
        • Contact:
      • Rochester, Minnesota, United States, 55905
        • Recruiting
        • Mayo Clinic - Rochester
        • Contact:
          • Clinical Trials Office - All Mayo Clinic Locations
          • Phone Number: 855-776-0015
    • Missouri
      • Kansas City, Missouri, United States, 64111
        • Recruiting
        • Saint Luke's Cancer Institute
        • Contact:
      • St Louis, Missouri, United States, 63110
        • Recruiting
        • Washington University School of Medicine
        • Contact:
    • Nevada
      • Reno, Nevada, United States, 89502
      • Reno, Nevada, United States, 89511-2250
    • New Jersey
      • Belleville, New Jersey, United States, 07109
        • Withdrawn
        • New Jersey Cancer Care, PA
      • New Brunswick, New Jersey, United States, 08901
    • New Mexico
      • Albuquerque, New Mexico, United States, 87110
        • Not yet recruiting
        • Presbyterian Kaseman Hospital
        • Contact:
      • Rio Rancho, New Mexico, United States, 87124
        • Recruiting
        • Presbyterian Rust Cancer Center
        • Contact:
    • New York
      • New York, New York, United States, 10029
      • New York, New York, United States, 10065
        • Recruiting
        • David H. Koch Center for Cancer Care at Memorial Sloan Kettering Cancer Center
        • Contact:
      • New York, New York, United States, 10011
        • Recruiting
        • The Blavatnik Family - Chelsea Medical Center at Mount Sinai
        • Contact:
    • North Carolina
      • Durham, North Carolina, United States, 27705
    • North Dakota
      • Grand Forks, North Dakota, United States, 58201
        • Completed
        • Altru Health Systems
    • Ohio
      • Cleveland, Ohio, United States, 44106
      • Cleveland, Ohio, United States, 44119
        • Withdrawn
        • Cleveland Clinic
      • Columbus, Ohio, United States, 42112
        • Recruiting
        • The Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solovev Research Institute (OSUCCC - James)
        • Contact:
    • Pennsylvania
      • Pittsburgh, Pennsylvania, United States, 15232
        • Completed
        • University of Pittsburgh Medical Center
    • Texas
      • Houston, Texas, United States, 77030
      • Houston, Texas, United States, 77030
      • Houston, Texas, United States, 77054
        • Recruiting
        • Harris Health System - Smith Clinic
        • Principal Investigator:
          • Ahmed Elkhanany
        • Contact:
    • Washington
      • Seattle, Washington, United States, 98104
        • Withdrawn
        • Swedish Cancer Institute (SCI)

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Pre- or postmenopausal women or men.
  2. Locally advanced and/or metastatic ER+ breast cancer with radiological or clinical evidence of progression on an AI in combination with either palbociclib or ribociclib as their first hormonal treatment for metastatic disease.
  3. Histological or cytological confirmation of ER+/HER2 - disease
  4. No evidence of progression for at least 6 months on an AI/CDKi combination for advanced breast cancer.
  5. 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.
  6. Locally advanced or metastatic breast cancer with either measurable (according to RECIST 1.1) or non-measurable lesions.
  7. 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.
  8. Eastern Cooperative Oncology Group (ECOG) performance score of 0 or 1
  9. Adequate organ function
  10. Able to swallow tablets

  11. Brain metastases are allowed only if the following 4 parameters hold:

    1. Asymptomatic,
    2. Definitively treated (e.g., radiotherapy, surgery),
    3. Not requiring steroids up to 4 weeks before study treatment initiation, AND
    4. Central nervous system disease stable for >3 months prior to registration as documented by magnetic resonance imagining (MRI).
  12. Able to understand and voluntarily sign a written informed consent before any screening procedures.
  13. Every attempt should be made to obtain a biopsy of metastatic breast cancer tissue, when safe and feasible, to provide histological or cytological confirmation of ER+/HER2- disease as assessed by a local laboratory, according to American Society of Clinical Oncology/College of American Pathologists guidelines, using slides, paraffin blocks, or paraffin samples. If a biopsy is done, it may undergo genomic testing at some point to assess for ESR1 mutations and correlation with ctDNA results. If a biopsy is not possible or inappropriate from a clinical standpoint, the ER and HER2 status from the subject's most recent biopsy must confirm that the subject is ER+ and HER2

Exclusion Criteria:

  1. Lymphangitic carcinomatosis involving the lung.
  2. History of Grade 3 or Grade 4 interstitial lung disease (ILD) on previous therapy.
  3. Visceral crisis in need of cytotoxic chemotherapy as assessed by the investigator.
  4. Prior progression of disease on abemaciclib, fulvestrant, or other selective estrogen receptor degrader (SERD) therapy.
  5. Subjects with a known hypersensitivity to fulvestrant or to any of the excipients
  6. Radiotherapy within 30 days prior to Visit 0 (Day 1) except in case of localized radiotherapy for analgesic purposes or for lytic lesions at risk of fracture, which can then be completed within 7 days prior to Visit 0 (Day 1). Subjects must have recovered from radiotherapy toxicities prior to Visit 0 (Day 1).
  7. 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.)
  8. History of long QTc (Q-T interval corrected for heart rate) syndrome or a QTc of >480 msec.
  9. History of a pulmonary embolus (PE), deep vein thrombosis (DVT), or any known thrombophilia, unless the event occurred greater than 6 months prior to screening and the subject is treated with chronic anticoagulant therapy such as apixaban (Eliquis) or rivaroxaban (Xarelto).
  10. Lasofoxifene is not recommended for use in subjects with conditions that place them at increased risk for VTEs (such as severe congestive heart failure [CHF] or prolonged immobilization).
  11. On concomitant strong CYP3A4 inhibitors.
  12. On strong and moderate CYP3A4 inducers.
  13. Any significant co-morbidity that would impact the study or the subject's safety, including subjects with significant malabsorption.
  14. Active systemic bacterial or fungal infection (requiring intravenous [IV] antibiotics or antifungals at the time of initiating study treatment).
  15. Known infection with human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV).
  16. History of malignancy within the past 5 years (excluding breast cancer), except basal cell or squamous cell carcinoma of the skin curatively treated by surgery.
  17. Positive serum pregnancy test (only if premenopausal).
  18. Sexually active premenopausal women and men unwilling to use double-barrier contraception.
  19. Women who are breast feeding
  20. History of non-compliance to medical regimens.
  21. Unwilling or unable to comply with the protocol.
  22. Current participation in any clinical research trial involving an investigational drug or device within the last 30 days.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Treatment
Pre- and Postmenopausal Women and Men with locally advanced or metastatic ER+/HER2- breast cancer who have disease progression on an AI in combination with either palbociclib or ribociclib as their first hormonal treatment for metastatic disease and who have an ESR1 mutation.
Drug: Lasofoxifene in combination with abemaciclib
5 mg/d of oral lasofoxifene plus oral abemaciclib 150 mg twice a day
Active Comparator: Reference Therapy
Pre- and Postmenopausal Women and Men with locally advanced or metastatic ER+/HER2- breast cancer who have disease progression on an AI in combination with either palbociclib or ribociclib as their first hormonal treatment for metastatic disease and who have an ESR1 mutation.
Drug: Fulvestrant in combination with abemaciclib
Fulvestrant 500 mg intramuscular (IM) on Days 1, 15, and 29 and then once monthly thereafter plus oral abemaciclib 150 mg twice a day

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Progression free survival (PFS)
Time Frame: Within approximately 3 years
PFS is defined as the time from the date of randomization [Visit 0 (Day 1)] to the earliest date of first documented progression per RECIST 1.1 or death due to any cause.
Within approximately 3 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Objective response rate (ORR)
Time Frame: Within approximately 3 years
ORR is defined as the percentage of subjects with measurable disease at baseline whose best overall response is either a confirmed CR or a confirmed PR according to RECIST 1.1.
Within approximately 3 years
Overall survival (OS)
Time Frame: Within approximately 3 years
Overall survival is defined as time from the date of Visit 0 (Day 1) to death due to any cause.
Within approximately 3 years
Duration of response (DoR) in subjects with an objective response
Time Frame: Within approximately 3 years
DoR is from the date of first documented confirmed response (CR or PR) to the date of first documented progression of disease or death due to any cause, whichever is earlier.
Within approximately 3 years
Time to response (TTR) in subjects with an objective response
Time Frame: Within approximately 3 years
TTR is from the date of randomization to the date of first documented confirmed response (CR or PR).
Within approximately 3 years
Time to cytotoxic chemotherapy
Time Frame: Within approximately 3 years
From the date of randomization to the date of first documented use of cytotoxic chemotherapy.
Within approximately 3 years
Incidence of Adverse Events (AEs) and Serious AEs
Time Frame: Within approximately 3 years
The type, severity (graded by Common Terminology Criteria for Adverse Events [CTCAE version 5.0]), course, duration, seriousness, and relationship to study treatment will be assessed at each visit
Within approximately 3 years
Quality of Life (QoL) evaluated using the Functional Assessment of Cancer Therapy-Breast Cancer-Endocrine Subscale (FACT B-ES)
Time Frame: Within approximately 3 years
Scale ranges from 'Not at all' to 'Very much'
Within approximately 3 years
Clinical benefit rate (CBR)
Time Frame: Within approximately 3 years
CBR is defined as the percentage of subjects with best overall response of confirmed CR, confirmed PR, or stable disease (SD) with a duration of 24 weeks or longer according to RECIST 1.1. As used in this calculation, stable disease is defined as stable disease in those subjects with measurable disease plus nonPR/non progressive disease (PD) in subjects with non-measurable disease.
Within approximately 3 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

LeonaBio

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 31, 2023

Primary Completion (Estimated)

April 1, 2027

Study Completion (Estimated)

April 1, 2028

Study Registration Dates

First Submitted

January 13, 2023

First Submitted That Met QC Criteria

January 13, 2023

First Posted (Actual)

January 25, 2023

Study Record Updates

Last Update Posted (Actual)

April 21, 2026

Last Update Submitted That Met QC Criteria

April 16, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • SMX 22-002

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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