AstraZeneca's Enhertu wins keenly anticipated U.S. breast cancer nod

In the small group of patients with hormone-insensitive tumours, patients on Enhertu lived 6.3 months longer. Enhertu originally won U.S. approval in late 2019 as a third-line treatment for the 15% of breast cancer patients with HER2-positive disease.

AstraZeneca and Daiichi Sankyo have secured faster-than-expected U.S. approval for their drug, Enhertu, in patients with a particular form of breast cancer. This is the first-ever U.S. Food and Drug Administration (FDA) approval for a medicine specifically targeting patients with so-called HER2-low breast cancer.

Breast cancer can express, at varying levels, a protein called HER2 that contributes to its growth and spread. HER2-low tumours are defined as those whose cells contain lower levels of the HER2 protein on their surface. The U.S. approval is based on a data from a late-stage trial involving over 550 patients with HER2-low breast cancer - most with tumours that were hormone-sensitive - whose disease had spread and who had undergone at least one round of chemotherapy.

An interim analysis in June showed Enhertu prolonged survival by an additional 6.4 months in patients with hormone-sensitive tumours. Patients in the group lived for a median of 23.9 months versus 17.5 months for chemotherapy. In the small group of patients with hormone-insensitive tumours, patients on Enhertu lived 6.3 months longer.

Enhertu originally won U.S. approval in late 2019 as a third-line treatment for the 15% of breast cancer patients with HER2-positive disease. This fresh approval opens up a large new patient population and the prospect of billions in additional revenue for its makers. A host of targeted therapies has greatly improved the prognosis for patients with advanced HER2-positive breast cancer. But more than half of women whose breast cancer has spread to other organs and express little or no HER2 - referred to as HER2-low status - have limited treatment options.