The drug, Enhertu, doubled the amount of time patients lived without their cancer getting worse and significantly improved overall survival compared with standard chemotherapy, according to data released today at the American Society of Clinical Oncology meeting in Chicago.
The researchers are optimistic that the efficacy of Enhertu, the latest generation of therapies that target tumors that contain a protein called HER2, will expand treatment options for the most common cancer in women. The findings, initially published in February with less detail, marked the first time such a therapy had reduced deaths among patients with lower levels of the protein.
HER2 is a growth-related molecule that is sometimes involved in cancer. In cases where levels are high, blocking it with an antibody can stop or slow tumor growth. About 55% of patients classified as HER2 negative or lacking the protein actually have low levels.
HER2-low cancer
Other currently available targeted therapies have not been shown to be effective for patients with low-HER2 breast cancer, according to Shanu Modi, a medical oncologist at Memorial Sloan Kettering Cancer Center in New York. Enhertu will become a new standard of care for that group of patients, she said in an interview.
“The technology has really improved,” said Modi, who received consulting fees from AstraZeneca and Daiichi Sankyo. “These drugs are getting better and better.”
The drug is already approved for US patients with high levels of HER2.
The study specifically looked at patients whose tumors had hormone-binding proteins (estrogen or progesterone) that are also involved in cell growth. Enhertu prevented breast cancers from getting worse in these patients with low HER2 levels for an average of 10.1 months, almost double the 5.4 months seen in patients treated with standard chemotherapy. Overall survival increased to 23.9 months compared to 17.5 months in the standard treatment group.
The findings were also published in the New England Journal of Medicine.
One side effect of the drug is pulmonary toxicity, which affected 12% of those given the new drug, compared with less than 1% among those given standard treatment. Investigators reported three deaths of trial patients at Enhertu from lung toxicity, Modi said in an interview.
AstraZeneca, led by Chief Executive Officer Pascal Soriot, has made a big step forward in the field of cancer in recent years. In 2019, the UK drugmaker signed a deal with Japan’s Daiichi Sankyo worth up to $6.9 billion to co-develop Enhertu. The treatment is also being evaluated in gastric, lung, colorectal and other cancers.
Last year, AstraZeneca published data showing Enhertu had a significant advantage over Roche Holding AG’s Kadcyla in keeping breast cancer patients alive without their tumors getting worse.
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