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New pill shows promise in shrinking breast tumors, but study halted early

NCT ID NCT04191382

Disease control Sponsor: Sanofi Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed
The trial has finished. Results may not be published yet.
Stopped early This study
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 26, 2026 · Last updated Jun 26, 2026

Summary

This Phase 2 study tested two doses of amcenestrant, a new oral drug that blocks estrogen receptors, against letrozole, a standard hormone therapy, in 105 postmenopausal women with ER-positive, HER2-negative breast cancer. The goal was to see if amcenestrant could better reduce tumor cell growth (measured by Ki67 levels) before surgery. The trial was terminated early, so the full results are not available.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
Amcenestrant (a drug that blocks estrogen receptors) and letrozole (a drug that lowers estrogen levels)
What this could lead to
If successful, amcenestrant could offer a new oral option to shrink hormone-sensitive breast tumors before surgery.
What could go wrong
This trial was terminated early, so results are limited. It is a small Phase 2 study, and the drug may not prove better than existing treatments.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 2

Tests whether the treatment actually works, and watches for side effects, in a larger group.

Participants

105 people

The number who actually took part.

Started

Feb 2020

Finished

May 2021

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Female participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion criteria : * Histological or cytological proven diagnosis of invasive breast adenocarcinoma. * Localized breast cancer eligible for upfront breast conservative surgery or upfront mastectomy: Stage I, Stage II or operable Stage III (excluded T4) as defined in American Joint Committee on Cancer (AJCC) Cancer Staging Manual 8th edition 2017. * Postmenopausal women as defined by one of the following: * Spontaneous cessation of menses greater than (\>) 12 months. * or who had received hormonal replacement therapy but had discontinued the treatment and had follicle stimulating hormone (FSH) level in the postmenopausal range. * or with status post bilateral surgical oophorectomy. * or post bilateral ovarian ablation through pelvic radiotherapy. * Breast tumor size of at least 10 millimeters (mm) in greatest dimension measured by ultrasound. * Primary tumor had to be positive for Estrogen Receptors (ER+) and negative for HER2 (HER2-) receptor by immunohistochemistry. * Ki67 level of at least 15% at diagnosis from immunohistochemistry of the tumor. * Eastern Cooperative Oncology Group (ECOG) performance status 0-1. Exclusion criteria: * Medical history or ongoing gastrointestinal disorders potentially affecting the absorption of SAR439859 or letrozole. * Participants unable to swallow normally and to take capsules or tablets. * Participants with known active hepatitis A, B, C infection; or hepatic cirrhosis. * Participant with any other cancer; adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer or any other cancer from which the participant had been disease free for \>3 years were allowed. * Evidence of metastatic spread by standard assessment according to local practice. * Treatment with strong Cytochrome P450 3A (CYP3A) inducers or drugs that had the potential to inhibit uridine diphosphate glucuronosyltransferase (UGT) within 2 weeks before first study treatment administration or 5 elimination half-lives whichever was longest. * Treatment with drugs that were sensitive substrates of P-glycoprotein (P-gp) or of breast cancer resistance protein (BCRP) within 2 weeks before first study treatment administration or 5 elimination half-lives whichever was longer. * Use of any investigational agent within 4 weeks prior to randomization. * Recent use of hormone replacement therapy (last dose less than or equal to \[\<=\] 30 days prior to randomization). * Prior anti-cancer treatment was not allowed unless it was then completed at least 1 year prior to inclusion into this trial. * Previous systemic or local treatment for the new primary breast cancer currently under investigation (including surgery, radiotherapy, cytotoxic and endocrine treatments). * Inadequate hematological or renal function. * Prothrombin time/international normalized ratio (INR) \>1.5 \* upper limit of normal (ULN) or outside therapeutic range if received anticoagulation that would have had affected the prothrombin time/INR. * Any of the following abnormal liver function test results: Aspartate aminotransferase \>1.5 \* ULN; Alanine aminotransferase \>1.5 \* ULN; Total bilirubin \>1.5 \* ULN. * Participants were employees of the clinical study site or other individuals directly involved in the conduct of the study, or immediate family members of such individuals. * Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the Investigator, contraindicates participation in the study. The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

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Conditions

The condition(s) this trial relates to.

breast cancer breast neoplasm estrogen-receptor positive breast cancer

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Breast cancer

Contacts and locations

Locations

  • Investigational Site Number 0560001

    Leuven, 3000, Belgium

  • Investigational Site Number 0560002

    Namur, 5000, Belgium

  • Investigational Site Number 2500001

    Nantes, 44093, France

  • Investigational Site Number 2500002

    Saint-Cloud, 92210, France

  • Investigational Site Number 2500003

    Toulouse, 31059, France

  • Investigational Site Number 2500004

    Paris, 75010, France

  • Investigational Site Number 3800001

    Milan, 20141, Italy

  • Investigational Site Number 3800002

    Milan, 20132, Italy

  • Investigational Site Number 3800004

    Meldola, 47014, Italy

  • Investigational Site Number 3920001

    Yokohama, Japan

  • Investigational Site Number 3920002

    Osaka, Japan

  • Investigational Site Number 3920003

    Sapporo, Japan

  • Investigational Site Number 6430002

    Saint Petersburg, 197758, Russia

  • Investigational Site Number 6430003

    Saint Petersburg, 194156, Russia

  • Investigational Site Number 6430004

    Moscow, 119991, Russia

  • Investigational Site Number 6430006

    Moscow, 117186, Russia

  • Investigational Site Number 6430007

    Saint Petersburg, 195271, Russia

  • Investigational Site Number 7240001

    Madrid, 28041, Spain

  • Investigational Site Number 7240002

    Valencia, 46010, Spain

  • Investigational Site Number 7240003

    Córdoba, 14004, Spain

  • Investigational Site Number 7240005

    Barcelona, 08003, Spain

  • Investigational Site Number 8040001

    Uzhhorod, 88000, Ukraine

  • Investigational Site Number 8040002

    Vinnytsia, 21029, Ukraine

  • Investigational Site Number 8040004

    Kharkiv, 61166, Ukraine

  • Investigational Site Number 8040005

    Zaporizhzhya, 69040, Ukraine

  • Investigational Site Number 8400005

    Lincoln, Nebraska, 68506, United States

  • Investigational Site Number 8400007

    Hato Rey, 00917, Puerto Rico

  • Investigational Site Number 8400010

    Los Angeles, California, 90095, United States

  • Investigational Site Number 8400012

    Tacoma, Washington, 98405, United States

  • Investigational Site Number 8400014

    Tucson, Arizona, 85724, United States

  • Investigational Site Number 8400016

    Winston-Salem, North Carolina, 27157, United States

  • Investigational Site Number 8400018

    Fort Wayne, Indiana, 46804, United States

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