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

NCT ID NCT06265428

Ongoing 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.

Disclaimer Read more

This is a summary of the original study . Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.

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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

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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