The U.S. FDA has approved the first targeted therapy for patients with HER2-low breast cancer, AstraZeneca and Daiichi Sankyo’s Enhertu.

Enhertu is now available as a third third-line treatment for women with advanced HER2-positive breast cancer. HER2-low breast cancer is a newly defined subset of HER2-negative breast cancer, which means the tumours do not over-express the HER2 protein.

Out of the nearly 300,000 breast cancer cases diagnosed each year, between 80-85% of them can be categorized as HER2-negative subtype (including hormone receptor-positive and triple-negative breast cancer).

The approval was granted under the FDA’s Real-Time Oncology Review program after Enhertu secured Priority Review and Breakthrough Therapy designations. The FDA nod hinged on results from the DESTINY-Breast04 trial, a randomized study that included 557 adult patients in unresectable — or difficult to remove — or metastatic cancer. Results showed significant improvement in progression-free survival and overall survival.

Richard Pazdur, director of the FDA’s Oncology Center of Excellence and acting director of the Office of Oncologic Diseases in the FDA’s Center for Drug Evaluation and Research reiterated the importance of the approval, stating that “Having therapies that are specially tailored to each patient’s cancer subtype is a priority to ensure access to safe and innovative treatments.”