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

NCT ID NCT04191382

Terminated Disease control Sponsor: Sanofi Source: ClinicalTrials.gov ↗

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.

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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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