New hope for advanced breast cancer: DB-1303 takes on T-DM1 in major trial

NCT ID NCT06265428

Disease control Sponsor: DualityBio Inc. Source: ClinicalTrials.gov ↗

First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time

Summary

This Phase 3 trial compares a new drug called DB-1303 (also known as BNT323) to the current standard treatment T-DM1 in 228 people with HER2-positive breast cancer that cannot be removed by surgery or has spread to other parts of the body. All participants have already been treated with trastuzumab and a taxane. The main goal is to see if DB-1303 delays cancer growth longer than T-DM1, with secondary goals including overall survival and safety.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance: DB-1303 (also called BNT323)
What this could lead to: If DB-1303 works better than T-DM1, it could become a new treatment option for people with HER2-positive breast cancer that has spread and stopped responding to earlier therapies.
What could go wrong: This is a Phase 3 trial, but results are not yet available. DB-1303 may not prove superior to T-DM1, and side effects could be similar or worse. The study is also limited to a specific patient group.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

228 people

The number who actually took part.

Started

Jan 2024

Expected to finish

Feb 2026

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Anyone

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * 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. Exclusion Criteria: * 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.

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Conditions

The condition(s) this trial relates to.

breast neoplasm HER2 positive breast carcinoma

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

HER2-positive breast cancer

Contacts and locations

Locations

001

Beijing, Beijing Municipality, 100039, China
002

Shanghai, Shanghai Municipality, 200032, China
003

Xi’an, Shanxi, 710061, China
004

Nanjing, Jiangsu, 210029, China
005

Zhengzhou, Henan, 450052, China
006

Zhengzhou, Henan, 450003, China
007

Chengdu, Sichuan, 610041, China
008

Changchun, Jilin, 130021, China
009

Wuhan, Hubei, 430079, China
010

Beijing, Beijing Municipality, 100142, China
011

Wuhan, Hubei, 430030, China
012

Linyi, Shandong, 276003, China
013

Ürümqi, Xinjiang, 830011, China
014

Nanchang, Jiangxi, 330006, China
015

Bengbu, Anhui, 233000, China
016

Hefei, Anhui, 230001, China
017

Nanning, Guangxi, 530021, China
018

Luoyang, Henan, 471003, China
019

Hangzhou, Zhejaing, 310022, China
020

Haerbin, Heilongjiang, 150081, China
021

Tianjin, Tianjin Municipality, 300060, China
022

Nanning, Guangxi, 530021, China
023

Guangzhou, Guangdong, 510060, China
024

Guangzhou, Guangdong, 510080, China
025

Hangzhou, Zhejiang, 310003, China
026

Guangzhou, Guangdong, 510120, China
027

Nanjing, Jiangsu, 210009, China
028

Huizhou, Guangdong, 516001, China
029

Hefei, Anhui, 230601, China
030

Changsha, Hunan, 410005, China
031

Jinan, Shandong, 250013, China
032

Dalian, Liaoning, 116021, China
033

Kunming, Yunnan, 650118, China
034

Yibin, Sichuan, 644000, China
035

Taiyuan, Shanxi, 030013, China
036

Fuzhou, Fujian, 350014, China
037

Xiamen, Fujian, 361003, China
038

Jilin City, Changchun, 130022, China
039

Yantai, Shandong, 264001, China
040

Binzhou, Shandong, 256603, China
041

Neijiang, Sichuan, 641100, China
042

Hangzhou, Zhejiang, 310016, China
043

Haikou, Hainan, 570102, China
044

Xuzhou, Jiangsu, 221006, China
045

Baoding, Hebei, 071000, China
046

Shanghai, Shanghai Municipality, 200120, China
047

Jinan, Shandong, 250117, China
048

Shijiazhuang, Hebei, 050011, China

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