AstraZeneca Breast-Cancer Drug Shown to Slow Tumor Progression

A new study of an AstraZeneca PLC breast-cancer drug showed it cut the risk of tumor progression by half for people with the most advanced form of the disease, offering the prospect of a new treatment for one of the most widely diagnosed cancers. AstraZeneca and Japan’s Daiichi Sankyo Co. said Enhertu, which the drugmakers developed jointly, stopped disease progression in patients who took it in the study for an average of 9.9 months, compared with 5.1 months for those who were given chemotherapy. The drug also cut the risk of death by 36% compared with chemotherapy. The large, late-stage trial involved 557 patients with advanced metastatic breast cancer, meaning the tumors had spread to other organs.

Enhertu, which is already on the market for a subset of breast-cancer patients, works by targeting a type of receptor, called HER2, that can be found on the surface of cancer cells and delivering a discreet but powerful dose of chemotherapy at the site. By seeking out the HER2 receptor, it leaves healthy tissue alone, in contrast with traditional chemotherapy that can’t differentiate between tumor and normal cells.

Traditionally, drugs that target that receptor, such as Roche Holding AG’s Herceptin, are only used in the 15% to 20% of breast-cancer patients whose tumors have high levels of HER2. An earlier trial showed that Enhertu cut the risk of disease progression or death by 72% in patients whose cancers have high levels of HER2, compared with an older HER2 targeting therapy.

In the latest trial, AstraZeneca and Daiichi Sankyo recruited patients whose cancer had low levels of HER2. Enhertu’s success in treating these trial patients could substantially widen the pool of patients who could benefit from the drug. Around 40% to 50% of patients have breast cancer with low levels of HER2. The study represents the first time that patients with low levels of HER2 have been shown to benefit from the HER2-targeted therapy.

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The positive result has also opened up the possibility for Enhertu to be used in other cancer types that express low levels of HER2, said Sunil Verma, a senior oncology executive at AstraZeneca. Those include gastric, lung, colorectal, ovarian and prostate cancer, he said.

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https://www.wsj.com/articles/astrazeneca-breast-cancer-drug-shown-to-slow-tumor-progression-11654514136 (subscription)