Dive Brief:
- AstraZeneca and Daiichi Sankyo’s drug Enhertu met the goal of a Phase 3 trial in people whose breast cancer had ultralow levels of an important protein called HER2, a finding that could again expand its use.
- The companies said Monday that Enhertu treatment was associated with a “statistically significant and clinically meaningful” slowing of tumor progression compared to standard chemotherapy in study participants with a common type of breast cancer that expresses either low or ultralow levels of HER2. The drug’s benefits were consistent between groups, they said.
- According to the companies, investigators reported an “early trend” toward a survival benefit among those receiving Enhertu, but the data weren’t yet complete enough make a definitive conclusion. The study will continue to assess survival as well as other secondary study measures. AstraZeneca and Daiichi plan to share the results with drug regulators.
Dive Insight:
Since arriving on the market in 2019, Enhertu has won a series of approvals in several tumor types and, in the process, changed how some breast cancers are treated.
A type of targeted medicine known as an antibody-drug conjugate, Enhertu was initially cleared for third-line treatment of HER2-positive breast cancer. It later became the first medicine approved for people with low, but still detectable, levels of the HER2 protein.
That finding shifted how breast cancer is categorized, making it important to know not only whether tumors are HER2 positive, but how much protein they express. The approval was a main reason why Enhertu sales surpassed $1 billion in 2022 and continue to climb, with Daiichi recently reporting more than $2.5 billion for the 2023 fiscal year.
Monday’s results could extend use earlier and to a broader group of people with breast cancer. The drug was tested in 866 breast cancer patients who had already received two prior hormone therapies or whose disease progressed soon after one hormone therapy and a type of drug called a CDK 4/6 inhibitor. Participants had metastatic disease and tumors classified as either HER2-low or ultralow.
The companies didn’t disclose details, leaving the magnitude of the drug’s effect unclear. They also noted that the trial wasn’t powered to demonstrate statistical significance in the subgroup of 153 people with HER2-ultralow disease.
Jefferies analyst Michael Yee noted the finding was “expected” given the similarities between the study population and the people in the trial that led to Enhertu’s approval in HER2-low disease. Feedback from surveys of breast cancer specialists also suggests there is “likely already broader use of Enhertu,” which may limit the study’s real-world sales impact, wrote RBC Capital Markets analyst Brian Abrahams in a client note.
Nonetheless, the data should support use of Enhertu earlier, where it may supplant chemotherapy in the second-line setting, Abrahams wrote. Enhertu may further pressure Gilead Sciences’ breast cancer drug Trodelvy, as a broader approval would shrink the number of people who could uniquely benefit from Gilead’s medicine, he added.
An antibody-drug conjugate as well, Trodelvy is approved for use in HER2-negative breast cancers.