BioNTech, DualityBio say ADC had ‘modest’ benefit in breast cancer study

An article from

An antibody-drug conjugate from BioNTech and DualityBio met its main goal in a Phase 3 study in breast cancer, but may only have a “limited” impact in people with the condition, the companies said Monday.

The treatment, known as trastuzumab pamirtecan, successfully delayed tumor progression in a trial of people whose breast tumors express low, but still detectable levels of the HER2 protein. The improvement on that measure was “modest,” though, and treatment was also associated with higher rates of interstitial lung disease — a potentially deadly kind of lung inflammation — than the companies had seen in earlier testing. 

The partners also revealed that “severe and fatal events” were observed in a “small proportion” of patients. They revealed, too, that the trial hadn’t been run long enough to detect a clear survival benefit.  

The combined findings “suggest that the potential benefit to patients would be limited” given the current treatment landscape for HER2-low metastatic breast cancer. The companies will “discuss the data and determine next steps,” they said. 

Trastuzumab pamirtecan is involved in two other ongoing trials. One is a late-stage study in HER2-positive endometrial cancer. The other is an early-stage study in advanced, metastatic solid tumors.

BioNTech obtained trastuzumab pamirtecan through a 2023 licensing deal with DualityBio that marked BioNTech’s first foray into antibody-drug conjugates, or ADCs. Potentially worth more than $1.6 billion overall, that pact was part of a broader effort by BioNTech to pursue oncology research and rely on more than its core messenger RNA technology.

That strategy has produced mixed results so far. Prior to Monday’s announcement, the company had reported two other clinical setbacks. 

ADCs have become a mainstay of cancer care and, in some tumor types, have been able to supplant traditional chemotherapy. One of those examples is in breast cancer, where AstraZeneca and Daiichi Sankyo’s Enhertu is deeply entrenched across multiple treatment lines. Enhertu gained the first-ever approval of a therapeutic for HER2-low disease in 2022 and followed that up with a clearance in tumors with “ultralow” HER2 expression three years later.

Like Enhertu, trastuzumab pamirtecan is an ADC aimed at the HER2 protein.