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HER2-positive Breast CancerPhase 3NCT06265428

A Study to Compare DB-1303/BNT323 Versus T-DM1 in Breast Cancer

A Phase 3 study testing DB-1303/BNT323 and T-DM1 in people with HER2-positive Breast Cancer, run by DualityBio Inc. at 48 sites in China.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

This study is designed to compare efficacy and safety of DB-1303/BNT323 versus T-DM1 in HER2-positive, unresectable and/or metastatic breast cancer patients previously treated with trastuzumab and taxane. Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
HER2-positive Breast Cancer
What is being tested?
DB-1303/BNT323 and T-DM1
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
228 participants
Where
48 sitesChina
Study dates
29 Jan 2024to Feb 2026
Phase
Phase 3
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Male or female adults ≥ 18 years at the time of voluntary signing of informed consent.
  • Pathologically confirmed unresectable or metastatic HER2 positive breast cancer previously treated with trastuzumab and taxane
  • Eastern Cooperative Oncology Group (ECOG) performance status score is 0 or 1.
  • Presence of at least one measurable lesion according to RECIST v1.1
  • Expected survival time ≥ 12 weeks.
  • Patients must give informed consent to this study and voluntarily sign written informed consent form prior to the study.

Who cannot join

  • Prior anti-HER2 ADC therapy.
  • Previous history of interstitial lung disease/noninfectious pneumonitis/radiation pneumonitis requiring steroid therapy.
  • Known serious hypersensitivity to the active ingredients of the study drug, inactive ingredients in the formulation, or other antibody drugs.
  • Multiple primary malignancies within 3 years, except for adequately resected non-melanoma skin cancer, curatively treated in situ tumor, or contralateral breast cancer
  • Uncontrolled infection requiring intravenous antibiotics, antiviral or antifungal agents, autoimmune disease requiring treatment, uncontrolled diabetes, hypertension, or other systemic disease that makes compliance with study procedures difficult
  • Unrecovered toxicity from prior anticancer therapy, defined as toxicity (except for alopecia) not recovered to ≤Grade 1 (NCI-CTCAE v5.0) or baseline.
  • NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Trial locations and contacts

48 sites in 1 country.

48 sites in 1 country

China48 sites

  • 045

    Baoding, Hebei, 071000

  • 001

    Beijing, Beijing Municipality, 100039

  • 010

    Beijing, Beijing Municipality, 100142

  • 015

    Bengbu, Anhui, 233000

  • 040

    Binzhou, Shandong, 256603

  • 008

    Changchun, Jilin, 130021

  • 030

    Changsha, Hunan, 410005

  • 007

    Chengdu, Sichuan, 610041

  • 032

    Dalian, Liaoning, 116021

  • 036

    Fuzhou, Fujian, 350014

  • 023

    Guangzhou, Guangdong, 510060

  • 024

    Guangzhou, Guangdong, 510080

  • 026

    Guangzhou, Guangdong, 510120

  • 020

    Haerbin, Heilongjiang, 150081

  • 043

    Haikou, Hainan, 570102

  • 019

    Hangzhou, Zhejaing, 310022

  • 025

    Hangzhou, Zhejiang, 310003

  • 042

    Hangzhou, Zhejiang, 310016

  • 016

    Hefei, Anhui, 230001

  • 029

    Hefei, Anhui, 230601

  • 028

    Huizhou, Guangdong, 516001

  • 038

    Jilin City, Changchun, 130022

  • 031

    Jinan, Shandong, 250013

  • 047

    Jinan, Shandong, 250117

  • 033

    Kunming, Yunnan, 650118

  • 012

    Linyi, Shandong, 276003

  • 018

    Luoyang, Henan, 471003

  • 014

    Nanchang, Jiangxi, 330006

  • 027

    Nanjing, Jiangsu, 210009

  • 004

    Nanjing, Jiangsu, 210029

  • 017

    Nanning, Guangxi, 530021

  • 022

    Nanning, Guangxi, 530021

  • 041

    Neijiang, Sichuan, 641100

  • 002

    Shanghai, Shanghai Municipality, 200032

  • 046

    Shanghai, Shanghai Municipality, 200120

  • 048

    Shijiazhuang, Hebei, 050011

  • 035

    Taiyuan, Shanxi, 030013

  • 021

    Tianjin, Tianjin Municipality, 300060

  • 013

    Ürümqi, Xinjiang, 830011

  • 011

    Wuhan, Hubei, 430030

  • 009

    Wuhan, Hubei, 430079

  • 003

    Xi’an, Shanxi, 710061

  • 037

    Xiamen, Fujian, 361003

  • 044

    Xuzhou, Jiangsu, 221006

  • 039

    Yantai, Shandong, 264001

  • 034

    Yibin, Sichuan, 644000

  • 006

    Zhengzhou, Henan, 450003

  • 005

    Zhengzhou, Henan, 450052

Other trials in China

About this study

Official title: A Phase III, Multicenter, Open-label, Randomized Study to Compare DB-1303 Versus T-DM1 in Patients With HER2-positive Unresectable/Metastatic Breast Cancer Who Have Been Treated With Trastuzumab and a Taxane (Dynasty-Breast01)

This study is designed to compare efficacy and safety of DB-1303/BNT323 versus T-DM1 in HER2-positive, unresectable and/or metastatic breast cancer patients previously treated with trastuzumab and taxane.

Read the detailed description

This is a randomized controlled, 2-arm, open-label, multicenter phase III study to assess the efficacy and safety of DB-1303/BNT323 versus Trastuzumab Emtansine (T-DM1) in patients with human epidermal growth factor receptor 2 (HER2) -positive unresectable/metastatic breast cancer who have been treated with trastuzumab and taxanes. Approximately 224 patients with unresectable or metastatic HER2-positive breast cancer will be randomized 1:1 to receive DB-1303/BNT323 or T-DM1, respectively.

Being tested
DB-1303/BNT323, T-DM1
Keywords
HER2-positive, Breast Cancer, BC
Medical subject headings
Breast Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • DB-1303/BNT323Drug

    Administered I.V.

  • T-DM1Drug

    Administered I.V.

Study groups in NCT06265428
Study groupRoleWhat they receive
DB-1303/BNT323ExperimentalEnrolled patients will receive DB-1303/BNT323 by intravenous (I.V.) infusion
Receives: Drug: DB-1303/BNT323
T-DM1ExperimentalEnrolled patients will receive T-DM1 by I.V. infusion
Receives: Drug: T-DM1

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Progression Free Survival (PFS) by Blinded Independent Central Review (BICR) assessment per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1)

    Defined as the time from randomization to the first documented disease progression per RECIST 1.1 as assessed by BICR or death due to any cause, whichever occurs first

    Measured: Up to approximately 24 months.

Secondary outcomes (12)

  1. Overall Survival (OS)

    Defined as the time from randomization to death due to any cause.

    Measured: Up to approximately 24 months.

  2. Progression Free Survival (PFS) by Investigator assessment per RECIST 1.1

    Defined as the time from randomization to the first documented disease progression per RECIST 1.1 as assessed by investigator or death due to any cause, whichever occurs first.

    Measured: Up to approximately 24 months.

  3. Objective response rate (ORR) by BICR and investigator assessment per RECIST 1.1

    Defined as the percentage of patients who have a complete response (CR) or partial response (PR) per RECIST 1.1 as assessed by BICR and investigator assessment.

    Measured: Up to approximately 24 months.

  4. Duration of response (DoR) by BICR and investigator assessment per RECIST 1.1

    Defined as the time from first response (CR or PR) to subsequent disease progression per RECIST 1.1 as assessed by BICR and investigator assessment, or death from any cause, whichever occurs first.

    Measured: Up to approximately 24 months.

  5. PK parameters: maximum observed concentration (Cmax)

    Maximum observed concentration (Cmax) of DB-1303/BNT323 Antibody-drug conjugate (ADC) and free toxin P1003, etc. after DB-1303/BNT323 administration

    Measured: Up to approximately 24 months.

  6. PK parameters: time to maximum concentration (Tmax)

    Time to maximum concentration (Tmax) of DB-1303/BNT323 ADC and free toxin P1003, etc. after DB-1303/BNT323 administration

    Measured: Up to approximately 24 months.

  7. Adverse events (AEs)

    Number and percentage of patients who report serious adverse events (SAEs), treatment-emergent adverse events (TEAEs), TEAEs leading to study drug discontinuation, adverse events of special interest (AESIs) (graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0[NCI-CTCAE v5.0])

    Measured: Up to approximately 24 months.

  8. Patient reported outcomes (PROs): European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ) - C30

    Change from baseline in the functioning/symptom/global quality of life (QoL) subscales of EORTC QLQ-C30. Scale scores range from 0-100. For functioning and global QoL scales, higher scores indicate better functioning or global health status. For symptom scales, higher scores indicate greater symptom burden.

    Measured: Up to approximately 24 months.

  9. Patient reported outcomes (PROs): EORTC QLQ-BR45

    Change from baseline in the functioning/symptom subscales of EORTC QLQ-BR45. Scale scores range from 0-100. For functioning scales, higher scores indicate better functioning. For symptom scales, higher scores indicate greater symptom burden.

    Measured: Up to approximately 24 months.

  10. Patient reported outcomes (PROs): European Quality of Life Five Dimension Five Level Scale (EQ-5D-5L)

    Change from baseline in EQ-5D-5L health state utility index score and Visual Analogue Scale (VAS) score. VAS score range from 0-100, higher scores indicate better health status.

    Measured: Up to approximately 24 months.

  11. European Quality of Life Five Dimension Five Level Scale (EQ-5D-5L)

    EQ-5D-5L health state utility index score and Visual Analogue Scale (VAS) score. The change from baseline value will be reported.

    Measured: Up to approximately 24 months.

  12. Anti-drug antibodies (ADA)

    Number and percentage of patients who develop anti-drug antibody (ADA) for DB-1303/BNT323.

    Measured: Up to approximately 24 months.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted20 Feb 2024
  2. Study start29 Jan 2024
  3. Primary completionFeb 2026 (estimated)
  4. Study completionFeb 2026 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 3
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
None (open label)
Enrolment
228 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06265428
Sponsor's protocol ID
DB-1303-O-3001
Other IDs
CTR20233403
Status last verified
Oct 2025
First submitted
5 Jan 2024
Last updated
20 Oct 2025
Results posted
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing DB-1303/BNT323 and T-DM1 in people with HER2-positive Breast Cancer, run by DualityBio Inc. at 48 sites in China.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 6 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 20 Oct 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 48 sites in China. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Progression Free Survival (PFS) by Blinded Independent Central Review (BICR) assessment per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) (time frame: Up to approximately 24 months.). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06265428.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Oct 2025.

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