A Phase 1/2 interventional study of BNT323 and BNT327 in Locally Advanced Breast Cancer, Unresectable Breast Carcinoma and Metastatic Breast Cancer, sponsored by BioNTech SE. Recruiting at 84 sites in 11 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-10.
Sponsored by BioNTech SE · Phase 1/2, Interventional, and Treatment
This is a Phase I/II, multi-site, open-label, two-part study designed to evaluate the efficacy, safety, optimized dose and contribution of components of BNT323 (also known as trastuzumab pamirtecan and DB-1303) in combination with BNT327 (also known as pumitamig and PM8002) in participants with hormone receptor-positive (HR+) or hormone receptor-negative (HR-), Human epidermal growth factor receptor (HER)2-positive, HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization -), HER2-ultralow (IHC 0, with membrane staining) or HER2-null breast cancer (BC), or triple-negative breast cancer (TNBC).
The study consists of two parts:
Randomization is planned for Cohort 1 in Part 2, i.e., participants will be randomized in 2:2:1:1 ratio into one of the four arms (Arms 1-4). No randomization is planned for any other cohort in Part 2.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 380 is above the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →BioNTech SE is the lead sponsor of 76 studies on the registry; 25 are open to participants now.
Of its 33 completed or terminated interventional studies of FDA-regulated products, 26 (79%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria (applicable to all participants and all parts unless otherwise specified):
Have documented BC that:
Key Exclusion Criteria:
Have received any of the following therapies or drugs prior to the initiation of the study:
NOTE: Other protocol defined Inclusion/Exclusion criteria 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.
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.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
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.
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.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
PD-1, PD-L1 and checkpoint inhibitors
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Escalating dose levels (DLs) of BNT323 and BNT327 to define RP2D. Six DLs are planned, i.e., DL0-1, DL1-1, DL2-1, DL0-0, DL1-0, DL2-0, a combination of three different DLs for BNT323 (DL0, DL1, and DL2) and two DLs for BNT327 (DL0 and DL1).
Drug: BNT323 · Drug: BNT327
Drug: BNT323 · Drug: BNT327
Drug: BNT323 · Drug: BNT327
BNT323 monotherapy at a fixed dose
Drug: BNT323
BNT327 monotherapy at a fixed dose
Drug: BNT327
Drug: BNT323 · Drug: BNT327
Drug: BNT323 · Drug: BNT327
Drug: BNT323 · Drug: BNT327
Part 1 - Occurrence of dose limiting toxicities (DLTs)
By dose level.
Time frame: During the DLT evaluation period (Cycle 1), i.e., the time of initiation of the first dose of investigational medicinal product (IMP) up to 21 days
Occurrence of Treatment-emergent adverse events (TEAEs), Grade ≥3 TEAEs, serious adverse events (SAEs), treatment-related TEAEs, treatment-related Grade ≥3 TEAEs, and treatment-related SAEs
In Part 1 by dose level. In Part 2 by cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to 90 days after the last IMP dose
Occurrence of dose interruption, reduction, and discontinuation due to TEAEs
In Part 1 by dose level. In Part 2 by cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to 90 days after the last IMP dose
Part 2 - Objective response rate (ORR)
ORR defined as the proportion of participants in whom a confirmed complete response (CR) or partial response (PR) (per Response Evaluation Criteria in Solid Tumors version 1.1 \[RECIST v1.1\] based on the investigator's assessment) is observed as best overall response. By cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Part 1 - ORR
ORR defined as the proportion of participants in whom a confirmed CR or PR (per RECIST v1.1 based on the investigator's assessment) is observed as best overall response. By dose level.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Part 2 - Duration of response (DoR)
DoR defined as the time from first objective response (CR or PR per RECIST v1.1 based on the investigator's assessment) to first occurrence of objective tumor progression (progressive disease \[PD\], per RECIST v1.1 based on the investigator's assessment) or death from any cause, whichever occurs first. By cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Part 2 - Disease control rate (DCR)
DCR defined as the proportion of participants with confirmed CR, PR, or stable disease (per RECIST v1.1 based on the investigator's assessment) as best overall response. By cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Part 2 - Time to response (TTR)
TTR defined as the time from first dose of IMP to first objective response (CR or PR per RECIST v1.1 based on the investigator's assessment). By cohort and arm.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Part 2 Cohort 1 only - Progression free survival (PFS)
PFS based on the investigator's assessment defined as the time from first dose of IMP to the first objective tumor progression (PD per RECIST v1.1) or death from any cause, whichever occurs first. By arm.
Time frame: From the time of initiation of the first dose of IMP to last tumor assessment scan, i.e., up to 36 months.
Plan to share: No
No publications or documents are linked to this record.
Started Apr 2025 (actual). Primary completion is estimated for Aug 2029, 52 months after the start.
Of 161 industry-sponsored phase 1/2 interventional studies under Breast Neoplasms, half reached primary completion within 59 months of starting (the median), counting those still running; a quarter within 44 and three quarters within 75. This study's planned 52 months is below that.
Counting every sponsor, half of 327 studies reached it within 61 months; a quarter within 45 and three quarters within 88.
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.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drugs tested here: Trastuzumab pamirtecan · Pumitamig