Study of Camizestrant and Abemaciclib in Patients with ER‑positive HER2‑negative Metastatic Breast Cancer Who Show Rising ctDNA

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What is this study about?

The study focuses on patients with advanced ER+/HER2- metastatic breast cancer who are typically treated first with a CDK4/6i together with an aromatase inhibitor. It examines whether switching to the oral drugs camizestrant and abemaciclib after a rise in ctDNA can improve outcomes. The purpose is to demonstrate the efficacy of this treatment switch.

Participants have regular blood tests that check for ctDNA, which are small fragments of tumor DNA found in the bloodstream. If the level increases while imaging still shows no tumor growth, the patient is randomly assigned to receive the new drug combination. After the switch, the study follows patients for several months, recording the time until the cancer gets worse, called progression‑free survival, using standard imaging criteria known as RECIST. Additional observations include side‑effect grading according to CTCAE, overall health status measured by ECOG PS, and the length of time patients remain alive, referred to as OS. Patients also complete questionnaires that assess quality of life. The design involves periodic clinic visits, imaging assessments, and questionnaire completion until disease progression, start of chemotherapy, or death.

1 enrollment and baseline evaluation

after joining the study, a baseline visit is scheduled to confirm the rise in ctDNA and to collect blood samples and imaging scans that will be used as reference points for later comparison.

the study team will review the recent use of a first‑line cdK4/6 inhibitor and aromatase inhibitor to ensure eligibility.

2 randomization and start of study medication

participants are randomly assigned to receive the new combination therapy.

the first dose of camizestrant (75 mg oral film‑coated tablet) and abemaciclib (dose may be 100 mg, 200 mg, or 300 mg oral) is taken on the day of randomization.

3 daily medication intake

take camizestrant 75 mg by mouth once each day.

take the assigned dose of abemaciclib by mouth once each day, as instructed by the study doctor.

continue both medicines every day until disease progression, unacceptable side effects, or the end of the study period.

4 regular monitoring visits

visit the clinic approximately every 8 to 12 weeks for blood draws that measure ctDNA levels and for safety laboratory tests.

undergo scheduled imaging assessments (such as scans) no more than once per year, unless the doctor determines an earlier scan is needed.

the study collects information on tumor status to evaluate progression‑free survival.

5 reporting side effects

inform the study doctor of any new symptoms, such as fatigue, nausea, or changes in blood counts, as soon as they appear.

adverse events are recorded using a standard grading system (ctcae v5.0) to assess safety of the treatment.

6 continuation or discontinuation of therapy

if the disease shows progression, or if side effects become unacceptable, the study medication is stopped and the next line of cancer treatment is started according to the doctor’s recommendation.

if no progression occurs, continue taking the study drugs until the planned end of the trial (estimated 2031‑08‑01) or until the doctor advises otherwise.

7 final assessment and study closure

at the end of the study period or at early discontinuation, a final set of blood tests, imaging scans, and quality‑of‑life questionnaires (eortc qlq‑c30 and eortc br42) is completed.

the collected data are used to evaluate the overall effectiveness and safety of the combination therapy.

Who Can Join the Study?

Must be 18 years of age or older.
Must have advanced or metastatic ER+ HER2‑negative breast cancer (ER+ means the cancer cells grow in response to estrogen; HER2‑negative means they do not over‑produce the HER2 protein).
Must have received at least 6 months (about 22 weeks) of first‑line treatment with an aromatase inhibitor (AI) plus a CDK4/6 inhibitor (such as palbociclib or ribociclib) and must show no disease progression on scans since starting that therapy.
Must have rising circulating tumor DNA (ctDNA) detected during the first screening step (ctDNA are tiny fragments of cancer DNA found in the blood).
Must have an evaluable tumor that can be measured using RECIST v1.1 criteria (a standard way doctors assess tumor size on imaging).
Must have an archival tumor tissue sample that is less than 10 years old, contains at least 30 % cancer cells, and is suitable for genetic testing.
Must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 (fully active or able to carry out light work but still up and moving).
Must have adequate blood and organ function, including:
- Hemoglobin ≥ 9.0 g/dL (a measure of red blood cells).
- Absolute neutrophil count ≥ 1,000/mm³ (a type of white blood cell).
- Total bilirubin ≤ 1.5 times the upper limit of normal (or ≤ 3 times if you have Gilbert’s syndrome, a harmless liver condition).
- ALT and AST ≤ 3 times the upper limit (≤ 5 times if liver metastases are present) – these are liver enzymes.
- Alkaline phosphatase ≤ 2.5 times the upper limit (≤ 5 times if bone or liver metastases are present).
- Serum creatinine ≤ 1.5 times the upper limit or calculated creatinine clearance ≥ 30 mL/min (a measure of kidney function, calculated with the Cockcroft‑Gault formula).
Must have a life expectancy of at least 6 months.
Must be willing and able to attend scheduled study visits and follow the treatment plan.
Must be able to give written informed consent (or have an impartial witness sign if physically unable).
Must provide any additional written consents required for specific parts of the study.
Must be enrolled in a social security or equivalent health‑benefit scheme.
Women of child‑bearing potential must have a negative pregnancy test within 28 days before enrollment, agree to use effective contraception during the study and for a set period after the last dose, and must not donate eggs or breast‑feed during that time.
Men who could father a child must use effective contraception (condom + spermicide) during the study and for a set period after the last dose, and must not donate or bank sperm.
Male participants who are surgically sterile (e.g., vasectomy) are acceptable if they follow the contraception rules above.
Must have no history of serious blood clot (venous thrombo‑embolic event), interstitial lung disease, or other lung problems that could affect breathing.
Must not have any other condition that, in the investigator’s judgment, would make participation unsafe.

Who Cannot Join the Study?

Received any cancer‑killing (systemic antineoplastic) treatment before starting the required aromatase inhibitor and CDK4/6 inhibitor, except for standard post‑surgery (adjuvant) therapy.
Have cancer that has spread to the lining of the brain and spinal fluid (leptomeningeal metastasis) or to the brain itself.
Have a known reason not to take the study drugs camizestrant or abemaciclib, as judged by the doctor.
Have previously taken camizestrant, any other selective estrogen receptor degrader (SERD) or experimental hormone‑blocking medicines.
Have had another type of cancer, unless it was treated with the goal of cure, has been disease‑free for at least three years, or is a non‑melanoma skin cancer or early‑stage cervical cancer that was fully treated.
Are pregnant, are breastfeeding, or are not willing to use highly effective birth control as required by the study.
Cannot follow the study’s required medical visits because of distance, family responsibilities, social situation, or psychological reasons.
Are currently enrolled in another clinical trial that would interfere with this study (within 28 days before joining and during the study).
Are in prison, under protective custody, or have a legal guardian who makes medical decisions.
Have had a bone‑marrow transplant in the past.
Relapsed (cancer came back) while taking a CDK4/6 inhibitor or within one year after stopping an adjuvant CDK4/6 inhibitor.
Show disease progression on recent scans (taken within 28 days before the second step of the study) according to standard criteria (RECIST v1.1).
Have a known reason not to take abemaciclib, as judged by the doctor.
Have any serious heart or blood‑pressure problems, such as unexplained fainting, low blood pressure (systolic < 90 mmHg), serious heart rhythm blocks, left‑ventricular ejection fraction  160 mmHg or diastolic > 90 mmHg), very slow heart rate (  480 ms) or other arrhythmias.
Have taken, within two weeks before randomization, medicines that are strongly affected by liver enzymes CYP2C9, CYP2C19, or CYP3A4/5 (for example, warfarin, phenytoin, omeprazole, or St John’s Wort) without stopping them as required.
Have used drugs known to lengthen the QT interval (a heart‑electric measure) in the time frame specified by the study protocol.
Are currently taking medicines that can prolong the QT interval and increase the risk of a specific dangerous rhythm called Torsades de Pointes.
Have an active infection such as tuberculosis, hepatitis B (positive surface antigen), or hepatitis C (positive RNA test). Past hepatitis B infection with negative surface antigen and positive core antibody is allowed; hepatitis C antibody positive is allowed only if the virus is not detectable.
Have HIV infection unless all of the following are true: CD4+ cell count ≥ 350 cells/µL, no AIDS‑defining illnesses in the past year, on stable antiretroviral therapy for at least four weeks, and viral load < 400 copies/mL.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country
Centre Jean Perrin	Clermont Ferrand	France
Institut De Cancerologie De Lorraine	Vandoeuvre Les Nancy	France
Institut Gustave Roussy	Villejuif	France
Oncopole Claudius Regaud	Toulouse	France
Centr Georges Francois Leclerc	Dijon	France
Institut Curie – Site Paris	Paris	France

Other Sites

Site Name	City	Country
Centre Antoine Lacassagne	Nice	France
Centre Henri Becquerel	Rouen	France
Centre Francois Baclesse	Caen	France
L’Hopital Prive Du Confluent	Nantes	France
Centre De Lutte Contre Le Cancer Eugene Marquis	Rennes	France
Oncoradio Centre Oncogard	Nimes	France
Centre Hospitalier Le Mans	Le Mans	France
Groupe Hospitalier Bretagne Sud	Lorient	France
Hopital Prive Des Cotes D’armor	Plerin	France
Centre Hospitalier De Bourg-En-Bresse	Bourg En Bresse	France
Centre Hospitalier Lyon Sud	Pierre Benite	France
Clinique De La Sauvegarde	Lyon	France
Institut Sainte Catherine	Avignon	France
Institut Godinot	Reims	France
Clinique Tivoli Ducos	Bordeaux	France
Centre Hospitalier Intercommunal De Cornouaille	Quimper	France
Imrgheqq Pvtbgvmweqadpkh Cecnqp Cfiwip	Marseille	France
Ctrqfk Opwwn Lynkpqk	Lille	France
Iodjorpc dc Ckbdmlbhpopu Hsrvygbzdpe Uxvtfsmhsijvc dc Skggn Etnndlx (hnkvgzp	Saint Priest En Jarez	France
Caroev dk Rpqfatmfxoolq &eharkg Cvaixxbm Sxplyc Amwb	STRASBOURG, Alsace	France
Clm dbertdkvigtrtf	Epagny Metz Tessy	France
Cvqepm Hhnguntrkvm Ej Uudvtzwgqpajs Db Lxatlbb	Limoges	France
Cvrobs Hhowiwdhtqy Rvkoaycn Uyhwxxqnajgaq Dl Tiucu	Tours	France
Czrzdu Lysh Bbobsn	Lyon	France

Trial status

Country	Status	Recruitment Start
France	Not yet recruiting	01.08.2026

Trial locations

Investigated Drugs:

Camizestrant is a pill taken by mouth that works as a type of hormone therapy. It blocks the effect of estrogen on breast cancer cells, which can help slow the growth of tumors that need estrogen to grow. In this study, patients who showed signs that their cancer might be becoming more active were switched to camizestrant to see if it could keep the disease under control.

Abemaciclib is also an oral medication that belongs to a class of drugs called CDK4/6 inhibitors. It stops certain proteins (CDK4 and CDK6) from helping cancer cells divide and grow. By adding abemaciclib after the cancer showed early signals of activity, researchers wanted to test whether it could further slow or stop the spread of the disease.

CDK4/6 inhibitor (initial therapy) refers to a group of drugs that block the same CDK4 and CDK6 proteins, used together with hormone therapy as the first treatment for advanced estrogen‑positive breast cancer. In this trial, participants had already been receiving a CDK4/6 inhibitor before the switch to the new medicines.

Aromatase inhibitor (initial therapy) is a type of hormone therapy taken as a pill that reduces the amount of estrogen made by the body. Lower estrogen levels help slow the growth of estrogen‑dependent breast cancers. Patients in the study were on an aromatase inhibitor before being switched to camizestrant and abemaciclib.

Estrogen receptor‑positive, HER2‑negative metastatic breast cancer – It is a breast cancer that depends on estrogen to grow and does not have an excess of the HER2 protein. The disease has already spread from the original breast tumor to other parts of the body such as bone, liver, lung or brain. Cancer cells continue to multiply and form new tumors in these distant sites. As the disease advances, the number and size of tumors may increase, leading to worsening symptoms. The cancer can become more resistant to hormone‑based therapies over time.

Trial ID:

2025-524213-84-00

Protocol code:

UC-BCG-2520

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of Camizestrant and Abemaciclib in Patients with ER‑positive HER2‑negative Metastatic Breast Cancer Who Show Rising ctDNA

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?