A Phase 1 interventional study of BGB-43395 and Fulvestrant in Advanced Solid Tumor, Advanced Breast Cancer and Metastatic Breast Cancer, sponsored by BeOne Medicines. Recruiting at 61 sites in 11 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by BeOne Medicines · Phase 1, Interventional, and Treatment
This is a dose escalation and dose expansion study to compare how well BGB-43395, a selective cyclin-dependent kinase 4 (CDK4) inhibitor, works as monotherapy or in combination with fulvestrant, letrozole, or elacestrant in participants with hormone receptor positive (HR+) and human epidermal growth factor 2 negative (HER2-) breast cancer (BC) and other advanced solid tumors. The main purpose of this study is to explore the recommended dosing for BGB-43395.
Our company, previously known as BeiGene, is now officially BeOne Medicines. Because some of our older studies were sponsored under the name BeiGene, you may see both names used for this study on this website.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 433 is above the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →BeOne Medicines is the lead sponsor of 68 studies on the registry; 48 are open to participants now.
Of its 6 completed or terminated interventional studies of FDA-regulated products, 0 (0%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Note: Other protocol defined Inclusion/Exclusion criteria may apply.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Allogeneic and autologous transplant
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Phase 1a: Sequential cohorts of increasing dose levels of BGB-43395 will be evaluated as monotherapy and in combination with either fulvestrant, letrozole, or elacestrant to assess for safety and tolerability.
Drug: BGB-43395 · Drug: Fulvestrant · Drug: Letrozole · Drug: Elacestrant
Phase 1a: Cohorts of selected dose levels of BGB-43395 in combination with fulvestrant or letrozole in HR+/HER2 breast cancer.
Drug: BGB-43395 · Drug: Fulvestrant · Drug: Letrozole
Phase 1b: The recommended dose for expansion (RFDE) for BGB-43395 (in combination with fulvestrant) from Phase 1a will be evaluated in HR+ breast cancer.
Drug: BGB-43395 · Drug: Fulvestrant
Phase 1b: The recommended dose for expansion (RFDE) for BGB-43395 in combination with letrozole from Phase 1a will be evaluated in HR+ breast cancer.
Drug: BGB-43395 · Drug: Letrozole
Phase 1b: The recommended dose for expansion (RFDE) for BGB-43395 in combination with letrozole from Phase 1a will be evaluated in HR+ breast cancer. Participants will also receive an anti-diarrheal agent for prophylaxis.
Drug: BGB-43395 · Drug: Letrozole · Drug: Anti-Diarrheal Agent
Planned doses administered orally.
Standard dose administered via intramuscular injection.
Standard dose administered orally as a tablet.
Standard dose administered orally as a tablet.
Administered orally as a tablet.
Phase 1a: Number of Participants with Adverse Events (AEs) and Serious Adverse Events (SAEs)
Number of participants with AEs and SAEs, including findings from physical examinations, electrocardiograms (ECGs), laboratory assessments, and that meet protocol-defined dose-limiting toxicity (DLT) criteria.
Time frame: Up to approximately 60 months
Phase 1a: Maximum Tolerated Dose (MTD) or Maximum Administered Dose (MAD) of BGB-43395
MTD is defined as the highest dose evaluated for which estimated toxicity rate is the closest to the target toxicity rate of 28%. MAD is defined as the highest dose administered if MTD is not reached.
Time frame: Up to approximately 60 months
Phase 1a: Recommended Dose for Expansion (RDFE) of BGB-43395
RDFE of BGB-43395 alone or in combination with fulvestrant, letrozole, or elacestrant will be determined based upon the MTD or MAD.
Time frame: Up to approximately 60 months
Phase 1b: Objective Response Rate (ORR)
ORR is defined as the percentage of participants who have confirmed complete response (CR) or partial response (PR) assessed by the investigator using Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.
Time frame: Up to approximately 60 months
Phase 1a: ORR
ORR is defined as the percentage of participants who have confirmed CR or PR assessed by the investigator using RECIST v1.1.
Time frame: Up to approximately 60 months
Phase 1a and 1b: Duration of Response (DOR)
DOR is defined as the time from the first determination of an overall response per RECIST v1.1 until the first documentation of disease progression or death, whichever occurs first as assessed by the investigator.
Time frame: Up to approximately 60 months
Phase 1a and 1b: Time to Response (TTR)
TTR is defined as the time from the date of the first dose of study drugs to the date of the first determination of objective response by the investigator using RECIST v1.1.
Time frame: Up to approximately 60 months
Phase 1b: Disease Control Rate (DCR)
DCR is defined as the percentage of participants with best overall response of CR, PR, or stable disease assessed by the investigator using RECIST v1.1.
Time frame: Up to approximately 60 months
Phase 1b: Clinical Benefit Rate (CBR)
CBR is defined as the percentage of participants with best overall response of confirmed CR, PR, or stable disease lasting ≥ 24 weeks.
Time frame: Up to approximately 60 months
Phase 1b: Progression-Free Survival (PFS)
PFS is defined as the time from the date of the first dose of study drug(s) to the date of the first documentation of progressive disease assessed by the investigator using RECIST v1.1 or death, whichever occurs first.
Time frame: Up to approximately 60 months
Phase 1b: Number of Participants with Adverse Events (AEs) and Serious Adverse Events (SAEs)
Number of participants with AEs and SAEs, including findings from physical examinations, electrocardiograms (ECGs), and laboratory assessments.
Time frame: Up to approximately 60 months
Phase 1a: Observed Plasma Maximum Concentration (Cmax) of BGB-43395 and its metabolite
Time frame: From Cycle 1 Day 1 up to Cycle 7 Day 1 (each cycle is 28 days)
Phase 1a: Observed Plasma Trough Concentration (Ctrough) of BGB-43395 and its metabolite
Time frame: From Cycle 1 Day 1 up to Cycle 7 Day 1 (each cycle is 28 days)
Phase 1a: Area under the concentration-time curve (AUC) of BGB-43395 and its metabolite
Time frame: From Cycle 1 Day 1 up to Cycle 7 Day 1 (each cycle is 28 days)
Phase 1a: Half-life (t1/2) of BGB-43395 and its metabolite
Time frame: From Cycle 1 Day 1 up to Cycle 7 Day 1 (each cycle is 28 days)
Phase 1b: Plasma concentrations of BGB-43395 and its metabolite
Time frame: From Cycle 1 Day 1 up to Cycle 5 Day 1 (each cycle is 28 days)
Not enrolling at this site — choose another above.
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Plan to share: Yes — BeOne shares data on completed studies responsibly and provides qualified scientific and medical researchers access to data and supporting documentation for clinical trials in dossiers for medicines and indications after submission and approval in the United States, China, and Europe. Clinical trials supporting subsequent local approvals, new indications, or combination products are eligible for sharing once corresponding regulatory approvals are achieved. BeOne shares data only when permitted by applicable data privacy and security laws and regulations, when it is feasible to do so without compromising the privacy of study participants, and other considerations. Qualified researchers with appropriate competencies who are engaged in novel scientific research may submit a request for participant-level data with a research proposal for BeOne review. Research teams must include a biostatistician and sign a Data Sharing Agreement prior to receiving access to clinical trial data.
Supporting information: Study protocol, Statistical analysis plan, Clinical study report
Time frame: See plan description
Access criteria: See plan description
Data sharing details ↗ · beonemedicines.com
No publications or documents are linked to this record.
Started Dec 2023 (actual). Primary completion is estimated for Dec 2029, 72 months after the start.
Of 388 industry-sponsored phase 1 interventional studies under Breast Neoplasms, half reached primary completion within 39 months of starting (the median), counting those still running; a quarter within 22 and three quarters within 56. This study's planned 72 months is above that.
Counting every sponsor, half of 759 studies reached it within 44 months; a quarter within 25 and three quarters within 66.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
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