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.

Disclaimer Read more

This is a summary of the original study . Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.

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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

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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