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Breast CancerPhase 3AMEERA-6NCT05128773

Study of Amcenestrant (SAR439859) Versus Tamoxifen for Patients With Hormone Receptor-positive (HR+) Early Breast Cancer, Who Have Discontinued Adjuvant Aromatase Inhibitor Therapy Due to Treatment-related Toxicity

A Phase 3 study testing Amcenestrant and Tamoxifen in people with Breast Cancer, run by Sanofi at 2 sites in 2 countries.

Terminated

Stopped early. The study ended before it was planned to and will not resume.

Official record
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Trial summary

This was a phase III, randomized, double blind, multicenter, 2-arm study evaluating the efficacy and safety of amcenestrant compared with tamoxifen in participants with hormone receptor-positive early breast cancer who discontinued adjuvant aromatase inhibitor (AI) therapy due to treatment related toxicity. Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
Breast Cancer
What is being tested?
Amcenestrant and Tamoxifen
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
3 participants
Where
2 sitesin 2 countries
Study dates
17 Feb 2022to 13 Oct 2022
Phase
Phase 3
Are there results?
Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Adult participants with histologically confirmed diagnosis of adenocarcinoma of the breast with documentation of hormone receptor-positive status, irrespective of human epidermal growth factor receptor 2 (HER2) status NOTE: Participants with HER2-positive breast cancer were eligible only if they had completed their adjuvant anti-HER2 treatment and chemotherapy.
  • With Stage IIB or Stage III (invasive breast cancer) who had undergone breast surgery and adjuvant radiation (if indicated) for the current malignancy.
  • Who had received prior aromatase inhibitors (AIs) (letrozole, anastrozole or exemestane or any sequence thereof) per the following:
  • Adjuvant AI therapy was discontinued due to AI treatment-related toxicity; Minimum of 6 months duration and maximum of 30 months duration (from initiation of first AI if there was a switch between AIs) of AI therapy was required.
  • Absence of locoregional and/or advanced/metastatic disease
  • Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1
  • Capable of giving signed informed consent.

Who cannot join

  • Medical history or ongoing gastrointestinal disorders potentially affecting the absorption of amcenestrant and/or tamoxifen. Participants unable to swallow normally or unable to take tablets and capsules. Predictable poor compliance to oral treatment. Active inflammatory bowel disease or chronic diarrhea, active hepatitis A/B/C, hepatic cirrhosis, short bowel syndrome, or any upper gastrointestinal surgery including gastric resection or banding procedures.
  • History of prior breast cancer treated with AI.
  • Any other solid tumor or lymphoma diagnosis was not allowed except if the participant had been free from disease for equal to greater than (=>5) years.
  • Pregnant or nursing women, or women of child-bearing potential without a negative pregnancy test prior to randomization.
  • Participants with unrecovered acute toxic effects of prior AI therapy or surgical procedures.
  • Uncontrolled intercurrent illness, including psychiatric conditions that would have limited compliance with study requirements.
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  • Treatment with any selective estrogen receptor degrader (SERD), tamoxifen or toremifene were not allowed as prior adjuvant therapy but could have been used as neoadjuvant therapy for a total duration of 3 months. Participants who were treated with a SERD, tamoxifen or toremifene in the neoadjuvant setting and who experienced disease progression were not allowed. Prior treatment with raloxifene or tamoxifen for bone health, risk reduction, or a prior breast cancer was allowed provided this was discontinued at least 3 years before diagnosis of current breast cancer.
  • Ongoing treatment with HER2 directed therapy. Appropriate wash out between the last dose of HER2 directed therapy and randomization should have been at least 4 weeks.
  • The above information was not intended to contain all considerations relevant to a potential participation in a clinical trial.

Trial locations and contacts

2 sites in 2 countries.

2 sites in 2 countries

Chile1 site

  • Investigational Site Number :1521622

    Santiago, Reg Metropolitana de Santiago

Other trials in Chile

China1 site

  • Investigational Site Number :1561599

    Haikou, 570311

Other trials in China

About this study

Official title: A Randomized, Multicenter, Double-blind, Phase 3 Study of Amcenestrant (SAR439859) Versus Tamoxifen for the Treatment of Patients With Hormone Receptor-positive, Human Epidermal Growth Factor Receptor 2-negative or Positive, Stage IIB-III Breast Cancer Who Have Discontinued Adjuvant Aromatase Inhibitor Therapy Due to Treatment-related Toxicity

This was a phase III, randomized, double blind, multicenter, 2-arm study evaluating the efficacy and safety of amcenestrant compared with tamoxifen in participants with hormone receptor-positive early breast cancer who discontinued adjuvant aromatase inhibitor (AI) therapy due to treatment related toxicity. The primary objective was to demonstrate the superiority of amcenestrant versus tamoxifen on invasive breast cancer-free survival.

The treatment duration per participant was to be 5 years, followed with a subsequent 5-years follow-up period. For the treatment period, visits were scheduled at the start of treatment, then at 4 weeks and 12 weeks after treatment start, and then every 12 weeks for the first 2 years and every 24 weeks for year 3 to 5. For the follow-up period, visits were scheduled 30 days after last treatment and then every 12 months. Three periods were planned:

  • A screening period of up to 28 days,
  • A treatment period of up to 5 years,
  • A follow-up period of up to 5 years.
Read the detailed description

Study duration per participant was to be approximately 10 years.

Conditions
Breast Cancer
Being tested
Amcenestrant, Tamoxifen, Amcenestrant-matching placebo, Tamoxifen-matching placebo
Medical subject headings
Breast Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • AmcenestrantDrug

    tablet, oral

  • TamoxifenDrug

    tablet, oral

  • Amcenestrant-matching placeboDrug

    tablet, oral

  • Tamoxifen-matching placeboDrug

    tablet, oral

Study groups in NCT05128773
Study groupRoleWhat they receive
Amcenestrant with tamoxifen-matching placebo armExperimentalAmcenestrant dose, once daily, continuously. Tamoxifen-matching placebo, once daily, continuously.
Receives: Drug: Amcenestrant; Drug: Tamoxifen-matching placebo
Tamoxifen with amcenestrant-matching placeboActive comparatorTamoxifen dose, once daily, continuously. Amcenestrant-matching placebo, once daily, continuously.
Receives: Drug: Tamoxifen; Drug: Amcenestrant-matching placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Invasive Breast Cancer-free Survival (IBCFS)

    IBCFS was defined according to standardized definitions for efficacy outcome measure in adjuvant breast cancer trials (STEEP) criteria version 2.0 as the time interval from the date of randomization to the date of the first occurrence of one of the following events: ipsilateral invasive breast tumor recurrence (IIBTR): invasive breast cancer involving the same breast parenchyma as the original primary; local-regional invasive breast cancer recurrence: invasive breast cancer in the axilla, regional lymph nodes, chest wall, and skin of the ipsilateral breast; distant recurrence: metastatic disease-breast cancer that has either been biopsy confirmed or clinically diagnosed as recurrent invasive breast cancer, invasive contralateral breast cancer; death attributable to any cause, including breast cancer, non-breast cancer, or unknown cause.

    Measured: From randomization to the date of first occurrence of IBCFS event (maximum exposure duration: 155 days)

Secondary outcomes (9)

  1. Invasive Disease-Free Survival (IDFS)

    IDFS according to STEEP criteria version 2.0 was defined as the time interval from the date of randomization to the date of the first occurrence of one of the following events: IIBTR: invasive breast cancer involving the same breast parenchyma as the original primary; local-regional invasive breast cancer recurrence: invasive breast cancer in the axilla, regional lymph nodes, chest wall, and skin of the ipsilateral breast; distant recurrence: metastatic disease-breast cancer that has either been biopsy confirmed or clinically diagnosed as recurrent invasive breast cancer; invasive contralateral breast cancer; second non-breast primary invasive cancer; death attributable to any cause, including breast cancer, non-breast cancer, or unknown cause.

    Measured: From randomization to the date of first occurrence of IDFS event (maximum exposure duration: 155 days)

  2. Distant Recurrence-free Survival (DRFS)

    DRFS according to STEEP criteria version 2.0 was defined as the time interval from the date of randomization to the date of the first occurrence of one of the following events: distant recurrence or death attributable to any cause (including breast cancer, non-breast cancer, or unknown cause).

    Measured: From randomization to the date of the first occurrence of distant recurrence or death due to any cause, whichever occurs first (maximum exposure duration: 155 days)

  3. Locoregional Recurrences-free Survival (LRRFS)

    LRRFS was defined as the time interval from the date of randomization to the date of the first occurrence of one of the following events: local/regional ipsilateral recurrence, invasive contralateral breast cancer or death attributable to any cause (including breast cancer, non-breast cancer, or unknown cause).

    Measured: From randomization to the date of the first occurrence of local/regional ipsilateral recurrence or breast cancer or death due to any cause, whichever occurs first (maximum exposure duration: 155 days)

  4. Overall Survival (OS)

    Overall survival was defined as the time interval from the date of randomization to the date of documented death (due to any cause).

    Measured: From randomization to the date of death due to any cause (maximum exposure duration: 155 days)

  5. Breast Cancer-specific Survival (BCSS)

    BCSS was defined as the time interval from the date of randomization to the date of documented death attributable to breast cancer cause.

    Measured: From randomization to the date of death due to breast cancer (maximum exposure duration: 155 days)

  6. Change From Baseline in Overall Side Effect Bother As Measured By Functional Assessment of Cancer Therapy Item GP-5 (FACT-GP5) Scale Scores

    FACT-GP5 is a single-item from the Functional Assessment of Cancer Therapy-General (FACT-G) scale in which participants report their bother by side effects of treatment response. Responses were given on a 5- point Likert-type scale with score range from 0 (not at all bothered by side effect) to 4 (very much bothered by side effects). Higher scores indicate a higher degree of side effect bother. End of treatment (EOT) visit was 30 days after the last IMP administration.

    Measured: Baseline, Cycle 3, 4, 5, 6, 7, 10, 13, 16, 19, 22, 25, 28, 34, 40, 46, 52, & 58 and at end of treatment (maximum exposure: any day up to 155 days)

  7. Change From Baseline in European Organization for Research and Treatment of Cancer Quality of Life Breast Cancer Specific Module (EORTC-QLQ-BR23): Systemic Therapy Side Effects Scale Score

    QLQ-BR23: 23-item disease-specific participant reported outcome measure of disease-related symptoms, treatment-related symptoms, and functioning relevant to participants with breast cancer. It consisted of 4 functional scales (body image, sexual enjoyment, sexual functioning, future perspective) and 4 symptoms scales (systemic therapy side effects, upset by hair loss, arm symptoms, breast symptom). Systemic therapy side effects scale consisted of 7 items \& each item was rated on a 4-point scale with responses as: 1= not at all, 2= a little, 3= quite a bit, 4= very much. A linear transformation was applied to raw scores so that all transformed scores are within 0 to 100. A higher score denotes worse symptoms for the systemic therapy side effects symptom scale. Negative change from baseline= improvement of side effects, positive change = deterioration. EOT visit was 30 days after last IMP administration.

    Measured: Baseline, Cycle 2, 4, 7, 10, 13, 16, 19, 22, 25, 28, 34, 40, 46, 52, & 58 and at end of treatment (maximum exposure: any day up to 155 days)

  8. Change From Baseline in European Organization for Research and Treatment of Cancer Core Quality of Life Questionnaire (EORTC-QLQ-C30): Global Health Status/Quality of Life (GHQ) Scale Score

    EORTC-QLQ-C30: cancer-specific instrument with 30 questions for evaluation of new chemotherapy \& assessment of participant reported outcome. EORTC QLQ-C30 included global health status/quality of life (GHS/QOL), functional scales (physical, role, cognitive, emotional, social), symptom scales (fatigue, pain, nausea/vomiting), and 6 single items (dyspnea, appetite loss, insomnia, constipation, diarrhea, financial difficulties). Most questions from QLQ-C30 were rated on a 4-point scale (1/Not at All to 4/Very Much), except Items 29-30, which comprise GHS scale and were rated on a 7-point scale (1/Very Poor to 7/Excellent). All scales were transformed from raw scores to linear scales ranging 0 to 100. A high score represented a favorable outcome with a best quality of life for participant. EOT visit was 30 days after last IMP administration.

    Measured: Baseline, Cycle 2, 4, 7, 10, 13, 16, 19, 22, 25, 28, 34, 40, 46, 52, & 58 and at end of treatment (maximum exposure: any day up to 155 days)

  9. Plasma Concentration of Amcenestrant

    Measured: Pre-dose on Cycle 2 Day 1, Cycle 7 Day 1, Cycle 13 Day 1 and Cycle 25 Day 1

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted22 Nov 2021
  2. Study start17 Feb 2022
  3. Primary completion13 Oct 2022
  4. Study completion13 Oct 2022

Why it stopped: Sponsor decision to prematurely stop the study, not linked to any safety concern

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 3
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
3 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05128773
Sponsor's protocol ID
EFC16133
Other IDs
U1111-1244-1767, BIG 20-01, AFT-55, EORTC-2033, 2021-000398-10
Acronym
AMEERA-6
Status last verified
Sep 2025
First submitted
10 Nov 2021
Last updated
16 Sep 2025
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing Amcenestrant and Tamoxifen in people with Breast Cancer, run by Sanofi at 2 sites in 2 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 7 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: stopped early, as of the sponsor's last update on 16 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 2 sites in Chile, China. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 22 Jun 2023). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Invasive Breast Cancer-free Survival (IBCFS) (time frame: From randomization to the date of first occurrence of IBCFS event (maximum exposure duration: 155 days)). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05128773.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Sep 2025.

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