AstraZeneca and Daiichi Sankyo recently announced that its drug Enhertu was approved in the United States for patients diagnosed as HER2-low or ultralow breast cancer that had metastasized after disease progression followed by a minimum of one endocrine therapy.
The approval was based on results from DESTINY-Breast06 Phase III trial showing treatment with Enhertu brought about 13.2 months progression-free survival as opposed to chemotherapy’s 8.1 months.
Enhertu is an HER2-Directed antibody drug conjugate (ADC) using the technology of Daiichi Sankyo. It is Sanko’s lead ADC and has the highest ranking atop AstraZeneca’s scientific platform.
Results were presented at the ASCO 2024 meeting and published in the NEJM.
Worldwide Breast Cancer Rates
In 2022 over two million cases of breast cancer were diagnosed with a worldwide count of 665,000 deaths. Breast cancer rates second as a leading cause of deaths related to cancer. The United States accounts for over three hundred thousand cases diagnosed annually.
Although early diagnosis results in high survival rates, the prognosis for thirty percent of patients whose cancer progresses to metastatic stage is a life expectancy of five years.
HER2 cancer helps cells divide and grow. It is expressed on various types of tumors including those found in breast cancer.
A patient who has high HER2 levels, representing 15 to 20% of breast cancers, is classified as HR2-positive and would be treated with HER2-targeted therapy to prevent metastasizing.
The category of “HR-positive, Her2 negative” represents 70% of breast cancers.
Endocrine Therapy (hormone therapy)
Endocrine cancer therapy uses hormones or drugs to prevent the growth of specific cancers that depend upon hormones for growth.
Endocrine therapies are given early to treat HR-positive breast cancer that has spread (metastasized) but its efficacy is limited.
The current treatment to follow endocrine therapy is chemotherapy. However, it is known to produce insufficient response rates.
DESTINY-Breast 06
The Phase III DESTINY trial evaluates Enhertu versus the investigator’s option for chemotherapy to treat patients with HR-positive, HER2-low or HER2-ultralow breast cancer either metastatic or advanced.
Participants (n866) had not been treated for metastatic or advanced disease and were given a minimum of two lines of endocrine therapy.
Enhertu’s Approval
The US is among 70 countries that has approved Enhertu for patients who have been diagnosed with HER2-low metastatic breast cancer and have received systemic therapy or had their disease recur during a six-month period after receiving secondary chemotherapy.
Primary Endpoint Survival (PFS)
The PFS in HER2-low patients is determined by a group of radiologists independently reviewing imaging studies. Secondary endpoints involve PFS in trial participants, overall response and length of response as well as time to the first or second treatment or to death. Safety was one of the secondary considerations and was consistent with previous trials.
In conclusion, AstraZeneca has a bold ambition to one day eliminate cancer as a cause of death.
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AstraZeneca breast cancer Daiichi Sankyo DESTINY-Breast06 Phase III Trial Enhertu Her2-low Breast Cancer
Last modified: March 17, 2025
