Just 11 days after AstraZeneca and Daiichi Sankyo gained FDA approval for their second antibody-drug conjugate (ADC) cancer treatment, Datroway, the partners have secured a seventh nod for their original ADC, Enhertu.
The U.S. regulator has cleared Enhertu as the first HER2-directed treatment for patients with HER2-low or HER2-ultralow metastatic breast cancer following disease progression after one or more endocrine therapies.
After breaking through in 2022, with an endorsement for Enhertu to become the first treatment for HER2-low metastatic breast cancer, the question became: How low could Enhertu go?
The FDA’s answer came on Tuesday. In addition to becoming the first treatment for those whose tumors show a lower level of the HER2 protein biomarker, the nod moves Enhertu up a notch in the treatment line for patients with HER2-low metastatic breast cancer. It can now be used following one or more failed endocrine therapies.
The endorsement is based on results from the DESTINY-Breast06 trial in which Enhertu showed a 36% reduction in the risk of disease progression or death versus chemotherapy. Progression-free survival came in at a median of 13.2 months for those on Enhertu compared to 8.1 for chemotherapy patients. Of those on Enhertu, 63% had a complete or partial response to treatment versus 34% for the chemotherapy group.
“Endocrine therapy is typically used in the initial treatment of HR-positive metastatic breast cancer and following progression, subsequent chemotherapy is associated with poor outcomes,” Aditya Bardia, M.D., trial investigator and UCLA Health Jonsson Comprehensive Cancer Center, said in a release. “[Enhertu] offers a potential new standard of care for patients with HR-positive, HER2-low or HER2-ultralow metastatic breast cancer following endocrine therapy.”
Enhertu was first approved in 2019 for patients with inoperable or metastatic HER2-positive breast cancer who have already failed on at least two other treatments. Earlier in 2019, AZ made a $6.9 billion bet on Enhertu, paying $1.35 billion up front to develop and commercialize the treatment outside of Japan. With Tuesday’s nod, AZ owes Daiichi a $175 million milestone payment, the companies said.
Enhertu achieved blockbuster status in 2022 and in the first three quarters of 2024 it generated $2.7 billion, which was up from $1.8 billion in the first three quarters of 2023.
Earlier this month, the companies scored FDA approval for Datroway to treat HR-positive, HER2-negative breast cancer in patients who have tried prior endocrine-based therapy and chemotherapy. In a $5 billion deal, with $1 billion paid up front, AZ signed on as a partner for the TROP-2 directed ADC.