BioNTech, DualityBio Move ADC into Phase III for HER2-Low Breast Cancer

3D Rendering of ADC

Pictured: 3D rendering of antibody-drug conjugate/iStock, Love Employee

BioNTech’s licensed antibody-drug conjugate is moving on to Phase III testing in a potential effort to challenge AstraZeneca and Daiichi Sankyo’s blockbuster Enhertu in a heavily treated breast cancer subpopulation. DualityBio, BioNTech’s partner and the ADC’s creator, posted the trial plans Wednesday. 

BioNTech added the ADC, DB-1303, to its portfolio in April 2023 when it paid China’s DualityBio $170 million upfront for rights to it plus a second preclinical asset. Another $1.5 billion is on the line in milestone payments, plus tiered royalties. 

DB-1303 will be pitted against chemotherapy in the open-label Phase III for patients with HER2-low, HR+ metastatic breast cancer patients whose disease has progressed despite endocrine therapy.  

ADC therapy is like a targeted missile for cancer, with an antibody targeted to deliver the cancer killing payload. DB-1303 is a topoisomerase-1 inhibitor. Phase I/II trial results showed the treatment to be well tolerated with encouraging antitumor activity in the already heavily pretreated patient population. 

If approved, BioNTech and DualityBio’s drug could be a strong competitor for AstraZeneca and Daiichi Sankyo’s HER2-directed antibody and topoisomerase inhibitor conjugate. Enhertu has already reached blockbuster status and is projected by to reach annual sales of $2.4 billion for the fiscal year ending March 2024. 

The ADC market continues to be hot. BioNTech’s pandemic partner Pfizer closed the biggest M&A deal of the year with its $43 billion buy of Seagen and its four already-approved cancer ADCs in March 2023. 

In August, BioNTech and DualityBio added another ADC to their collaboration to include a Trop2 antibody-drug conjugate. The third-generation ADC has demonstrated efficacy in non-small cell lung cancer (NSCLC) and other solid tumors. The deals grant BioNTech rights to market the three drugs globally except in mainland China, Hong Kong and Macau, where DualityBio retains commercial rights. 

Gilead’s Trodelvy is currently the only Trop-2 directed ADC approved by the FDA across multiple indications. Sales of the drug, primarily driven by breast cancer, were up to $260 million for the second quarter of 2023, with analysts projecting sales of $2.8 billion by 2028. 

BioNTech has been looking for new revenue streams, returning to its initial focus of cancer therapeutics in the face of sharp COVID-related product sales declines. Revenue for the first half of 2023 fell to $1.5 billion, compared to $10.4 billion during the same time period last year. 

DB-1303 is slated for primary completion of its Phase III by August 2025. 

Kate Goodwin is a freelance life science writer based in Des Moines, Iowa. She can be reached at and on LinkedIn.

Back to news