In short
BGB-43395 is an investigational oral medicine being studied for advanced or metastatic hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer. One authorised Phase 3 trial (NCT07492641) is comparing BGB-43395 plus letrozole against three approved CDK4/6 inhibitors plus letrozole in 1,056 patients who have not received prior systemic treatment for advanced disease. The trial's primary measure is progression-free survival (PFS), the time until the cancer grows or the patient dies.
Key points
- BGB-43395 is an investigational oral medicine for advanced or metastatic HR+/HER2- breast cancer.
- The single registered trial is a Phase 3 study with 1,056 planned participants.
- It compares BGB-43395 plus letrozole against CDK4/6 inhibitors (abemaciclib, palbociclib, or ribociclib) plus letrozole.
- The trial is authorised but not yet recruiting, according to registry data.
- The main outcome is progression-free survival, measured by blinded independent central review.
- Participants must have previously untreated advanced or metastatic HR+/HER2- breast cancer.
What is BGB-43395?
BGB-43395 is an investigational oral medicine being developed for the treatment of advanced or metastatic hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer. The substance has no marketing authorisation in the registry records and is not yet approved as a medicine. It is being studied in combination with letrozole, an aromatase inhibitor used to lower oestrogen levels in the body, in patients who have not received prior systemic treatment for advanced or metastatic disease.
The name BGB-43395 is the development code; no trade name or other name appears in the available sources. The trial record lists it only as an oral drug, with the dose reported as "000 mg" in the registry, meaning the exact dose was not disclosed in the public record.
How does BGB-43395 work?
The available sources do not describe the mechanism of action of BGB-43395 in detail. The trial compares it against cyclin-dependent kinase 4/6 inhibitors (CDK4/6 inhibitors), which block proteins that help cancer cells divide. However, the registry record does not state whether BGB-43395 itself is a CDK4/6 inhibitor or works through a different target. The trial is designed to test whether BGB-43395 plus letrozole can delay cancer progression as well as or better than approved CDK4/6 inhibitors plus letrozole.
Which conditions is BGB-43395 studied for?
- Advanced or metastatic HR+/HER2- breast cancer — breast cancer that has spread beyond the breast and nearby lymph nodes, is driven by oestrogen or progesterone (hormone receptor-positive), and does not overexpress the HER2 protein (HER2-negative). The trial focuses on patients who have not yet received systemic treatment for advanced disease.
How is BGB-43395 given?
BGB-43395 is given by mouth as an oral medicine. The exact dose is not reported in the public registry record. In the trial, it is taken in combination with letrozole 2.5 mg, also given orally. The comparator medicines — abemaciclib 300 mg, palbociclib 125 mg, and ribociclib 600 mg — are also oral medicines.
What do the clinical trials show?
One Phase 3 trial is registered for BGB-43395. The study, NCT07492641, is authorised but not yet recruiting according to the registry data. It plans to enrol 1,056 participants with previously untreated advanced or metastatic HR+/HER2- breast cancer.
The trial has two arms. Arm A receives BGB-43395 plus letrozole. Arm B receives the investigator's choice of a CDK4/6 inhibitor — abemaciclib, palbociclib, or ribociclib — plus letrozole. The primary outcome is progression-free survival (PFS), defined as the time from randomisation to the first documentation of disease progression or death from any cause, assessed by blinded independent central review using RECIST v1.1 criteria.
Because the trial has not yet reported results, no efficacy data are available. The registry records describe the study design and objectives only.
Who can take part in this trial?
The trial is open to adults aged 18 years and older with advanced or metastatic HR+/HER2- breast cancer who have not received prior systemic treatment for advanced or metastatic disease. The registry record does not list additional inclusion or exclusion criteria in the public summary. Patients interested in taking part can contact the study team using the details provided by the Be Part of Research service.
What side effects are known?
The available sources do not report side effects for BGB-43395. As an investigational medicine in a trial that has not yet reported results, its safety profile is not yet established in the public record.