The U.S. Food and Drug Administration has approved AstraZeneca (AZN) and Daiichi Sankyo’s breast cancer drug Enhertu for use as a first-line treatment, the agency said on Monday.

The approval covers the use of Enhertu in combination with Roche’s drug Perjeta for adults with advanced HER2-positive breast cancer identified by an FDA-approved test.

Enhertu was first approved in the United States in late 2019 as a third-line treatment for patients with HER2-positive breast cancer. The new decision expands its use to patients who have not previously received chemotherapy for metastatic disease.

Enhertu is an antibody-drug conjugate designed to deliver chemotherapy directly to HER2-positive cancer cells. The approach aims to limit damage to healthy tissue. The drug is already approved for use in certain breast, gastric, and lung cancers.

Perjeta, developed by Roche’s Genentech unit, was originally approved in June 2012. It was cleared for use with trastuzumab and chemotherapy in previously untreated HER2-positive metastatic breast cancer.

The FDA also approved two companion diagnostic tests to identify patients with HER2-positive breast cancer who may be eligible for treatment with the Enhertu and Perjeta combination.

The approval was based on results from a clinical study involving 1,157 patients with advanced HER2-positive breast cancer. All participants had not received prior chemotherapy for metastatic disease at the time of enrollment.

In the study, patients treated with the Enhertu and Perjeta combination achieved a median progression-free survival of 40.7 months. This compared with 26.9 months for patients receiving the standard treatment.

Tumors shrank or disappeared in 87% of patients who received the new combination therapy. In the standard treatment group, the response rate was 81%.

Overall survival data from the study were not mature at the time of the analysis. Across both study groups, 16% of patients had died.

AstraZeneca and Daiichi Sankyo have jointly developed and commercialized Enhertu. Roche is not a partner in the drug but markets Perjeta as part of its oncology portfolio.

The FDA decision marks a significant expansion of treatment options for patients with advanced HER2-positive breast cancer in the first-line setting.