Enhertu Sharply Improves Survival In Breast Cancer Patients: Report

A drug from AstraZeneca Plc and Daiichi Sankyo Co. extended the lives of patients with an advanced form of breast cancer by about six months in a late-stage trial that may widen the population of people who can benefit from the treatment.

The drug, Enhertu, doubled the amount of time patients lived without their cancer worsening and significantly improved overall survival when compared with standard chemotherapy, according to data released at the American Society of Clinical Oncology meeting in Chicago.

Shares in AstraZeneca dropped 1% in early trading in London Monday. Daiichi Sankyo rose 3.7% in Tokyo on Monday, their biggest rise in three weeks.

Researchers are optimistic that the effectiveness of Enhertu -- the latest generation of therapies that attack tumors bearing a protein called HER2 -- will expand treatment options for the most common cancer in women. The findings, initially released in February with less detail, marked the first time such a therapy reduced deaths among patients with lower levels of the protein.

HER2 is a growth-related molecule that sometimes becomes 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 targeted therapies currently available haven't proven effective for patients with HER2-low breast cancer, according to Shanu Modi, medical oncologist at Memorial Sloan Kettering Cancer Center in New York. Enhertu is set to become a new standard of care for that group of patients, she said in an interview.

"The technology has really improved," said Modi, who has 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 HER2 levels.

The study looked specifically at patients whose tumors had proteins that bind to hormones -- estrogen or progesterone -- that are also linked to cell growth. Enhertu kept breast cancers from worsening 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 rose to 23.9 months compared with 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 lung toxicity, which affected 12% of those who got the new drug, compared to less than 1% among those who got standard treatment. Researchers reported three deaths from trial patients on Enhertu from lung toxicity, Modi said in an interview.

AstraZeneca, led by Chief Executive Officer Pascal Soriot, has made a big push in the cancer field in recent years. In 2019, the UK drugmaker entered a deal with Japan's Daiichi Sankyo worth as much as $6.9 billion to jointly develop Enhertu. The treatment is also being evaluating in gastric, lung, colorectal and other cancers.

AstraZeneca last year released data showing that Enhertu had a significant edge over Roche Holding AG's Kadcyla in keeping breast cancer patients alive without their tumors worsening.

Enhertu could redefine the treatment of HER2-targetable cancers, said Susan Galbraith, executive vice president of oncology research and development at AstraZeneca. "We must now evolve the way we classify and treat metastatic breast cancer to ensure these patients are effectively diagnosed and treated," she said in a statement Monday.

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