BLA Is Accepted in China for Trastuzumab Pamirtecan in HER2+ Metastatic Breast Cancer

China’s National Medical Products Administration (NMPA) has accepted a biologics license application (BLA) seeking the approval of trastuzumab pamirtecan (T-Pam; DB-1303; BNT323) for the second-line treatment of adult patients with unresectable or metastatic HER2-positive breast cancer.¹

This BLA submission was backed by positive interim data from the pivotal phase 3 Study DB-1303-O-3001 (NCT06265428). Per an independent data monitoring committee, the trial met its primary end point of a statistically significant progression-free survival (PFS) improvement by blinded independent central review with T-Pam compared with ado-trastuzumab emtansine (Kadcyla; T-DM1).

“China has over 350,000 new breast cancer cases annually, representing a high incidence rate and ranking as the second most common cancer among Chinese women,” Hua Mu, MD, global chief medical officer of DualityBio, stated in a news release. “We are delighted to see that T-Pam has achieved a milestone in its commercialization progress, demonstrating its potential to provide an effective new treatment option for [patients with HER2-positive] breast cancer.”

What is the mechanism of action of T-Pam? How has T-Pam performed in early-stage research?

T-Pam is a third-generation topoisomerase-1 inhibitor–based antibody-drug conjugate (ADC) targeting HER2. This agent has demonstrated antitumor activity in HER2-positive and HER2-low tumor models. It has also shown efficacy in patients with advanced solid tumors, including breast and endometrial cancers.

The preclinical and preliminary clinical data with T-Pam show its ability to target HER2 receptors on solid tumors regardless of HER2 expression level. The agent also has a manageable safety profile.

What was the design of Study DB-1303-O-3001 in breast cancer?

This randomized, controlled, open-label, multicenter trial conducted in China assessed T-Pam compared with T-DM1 in patients with HER2-positive unresectable or metastatic breast cancer who have previously been treated with trastuzumab and a taxane. The trial enrolled male and female patients at least 18 years of age with an ECOG performance status of 0 or 1, at least 1 measurable lesion per RECIST 1.1 criteria, and an expected survival time of at least 12 weeks.²

Secondary end points included overall survival, investigator-assessed PFS, overall response rate, duration of response, pharmacokinetics, adverse effects, patient-reported outcomes, other quality of life measures, and the proportion of patients who develop anti-drug antibodies for T-Pam.

What is the regulatory status of T-Pam in the US?

In 2023, the FDA granted breakthrough therapy designation to T-Pam for use as a potential therapeutic option for patients with advanced endometrial cancer who have progressed during or after treatment with immune checkpoint inhibitors.³

What’s next for researching T-Pam in breast cancer and beyond?

T-Pam is under investigation as monotherapy and in combination with other agents in several other clinical trials across tumor types.

• The global phase 3 DYNASTY-Breast02 trial (NCT06018337) is evaluating the ADC compared with investigator’s choice of single-agent chemotherapy in the first-line setting in patients with HER2-low, hormone receptor (HR)–positive metastatic breast cancer.⁴
• The global, randomized, multi-site, open-label phase 3 Fern-EC-01 study (NCT06340568) is investigating the agent in the second-line setting in patients with endometrial cancer and varying levels of HER2 expression. Patients in the comparator arm are receiving investigator’s choice of doxorubicin, paclitaxel, or docetaxel.⁵
• The phase 1/2 BNT323-03 trial (NCT06827236) is assessing the agent in combination with or without pumitamig (BNT327; BMS-986545) in patients with HR-positive or -negative, HER2-low, -ultralow, or -null advanced or metastatic breast cancer.⁶

References

1. DualityBio announces China NMPA acceptance of biologics license application seeking approval for trastuzumab pamirtecan for the treatment of unresectable or metastatic HER2-positive adult breast cancer. News release. DualityBio. April 9, 2026. Accessed April 9, 2026. http://en.dualitybiologics.com/news/605.html
2. A study to compare DB-1303/​BNT323 versus T-DM1 in breast cancer. ClinicalTrials.gov. Updated October 20, 2025. Accessed April 9, 2026. https://clinicaltrials.gov/study/NCT06265428
3. BioNTech and DualityBio receive FDA breakthrough therapy designation for antibody-drug conjugate candidate BNT323/DB-1303 in endometrial cancer. News Release. BioNTech. December 21, 2023. Accessed April 9, 2026. https://investors.biontech.de/news-releases/news-release-details/biontech-and-dualitybio-receive-fda-breakthrough-therapy/
4. A study of DB-1303/​BNT323 vs investigator’s choice chemotherapy in HER2-low, hormone receptor positive metastatic breast cancer (DYNASTY-Breast02). ClinicalTrials.gov. Updated March 5, 2026. Accessed April 9, 2026. https://clinicaltrials.gov/study/NCT06018337
5. A clinical study of the anti-cancer effects of an investigational therapy or chemotherapy in patients with recurring uterine cancer (Fern-EC-01). ClinicalTrials.gov. Updated March 31, 2026. Accessed April 9, 2026. https://clinicaltrials.gov/study/NCT06340568
6. A clinical study to find the optimal dose of an investigational treatment called BNT323 when used in combination with another investigational treatment, BNT327, and to test if that combination treatment is safe and beneficial for patients with advanced breast cancer. ClinicalTrials.gov. Updated March 20, 2026. Accessed April 9, 2026. https://clinicaltrials.gov/study/NCT06827236