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Evaluating GB491 with Letrozole for Advanced Breast Cancer

A Randomized, Double-Blind, Placebo-Controlled Phase III Trial of GB491 in Combination With Letrozole in Subjects With HR Positive and HER2 Negative Locally Advanced or Metastatic Breast Cancer Who Have Not Previously Received Systemic Therapy in This Disease Setting

Phase 3 Interventional Genor Biopharma Co., Ltd. · NCT05851014

This study is testing if a new treatment called GB491, when combined with Letrozole, can help people with advanced breast cancer feel better compared to just using Letrozole alone.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment350 (estimated)
Ages18 Years to 75 Years
SexAll
SponsorGenor Biopharma Co., Ltd. Industry-sponsored
Drugs / interventionschemotherapy, radiation
Locations52 sites (Bengbu, Anhui and 51 other locations)
Trial IDNCT05851014 on ClinicalTrials.gov

What this trial studies

This study aims to assess the effectiveness and safety of GB491 when used in combination with Letrozole compared to a placebo with Letrozole in patients suffering from hormone receptor-positive and HER2-negative locally advanced or metastatic breast cancer. Participants must not have received any prior systemic antitumor therapy for their condition. The study will involve monitoring patient responses and side effects to determine the potential benefits of this treatment combination.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18-75 with confirmed HR+/HER2- breast cancer who have not undergone prior systemic antitumor therapy.

Not a fit: Patients with HER2 positive disease or those who have previously received chemotherapy for their breast cancer may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new effective option for patients with advanced breast cancer.

How similar studies have performed: Other studies have shown promise in using similar combinations for treating advanced breast cancer, suggesting potential for success.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* 1\. Age: 18-75 years old;
* Have a pathologically-confirmed diagnosis of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer;
* No previous systematic antitumor therapy for locally advanced or metastatic breast cancer;
* Eastern Cooperative Oncology Group \[ECOG\] 0-1;
* Have adequate organ and marrow function;
* Agree to sign the informed consent;

Exclusion Criteria:

* Systematic treatment with any other CDK4/6 inhibitor；
* Subjects with known allergy to GB491 or any component of Letrozole；
* Confirmed diagnosis of HER2 positive disease;
* Known uncontrolled, or symptomatic central nervous system metastases;
* Had major surgery (or is expected to require major surgery during the study period), chemotherapy, radiation, any investigational drug, or other antitumor therapy within 4 weeks prior to randomization;
* Have previously received chemotherapy for locoregionally recurrent or metastatic breast cancer;
* Clinically significant cardiovascular and cerebrovascular diseases, including but not limited to severe acute myocardial infarction within 6 months before enrollment, unstable or severe angina, Congestive heart failure, or ventricular arrhythmia which need medical intervention；
* Known history of HIV infection or HIV seropositivity (including HIV antibody positive at the time of screening)

Where this trial is running

Bengbu, Anhui and 51 other locations

+2 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Breast CancerHR+/HER2-locally advanced or metastatic breast cancerGB491
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.