AstraZeneca (AZ) and Daiichi Sankyo have reported updated results from a phase II trial of Enhertu, which continued to demonstrate ‘impressive’ efficacy in patients with HER2-positive metastatic breast cancer.

The phase II DESTINY-Breast01 trial is evaluating Enhertu (trastuzumab deruxtecan) in HER2-positive metastatic breast cancer patients, who have previously received two or more prior HER2-based regimens.

The updated data, which represents a median duration of follow-up of 20.5 months, demonstrated that patients treated with Enhertu achieved an objective response rate (ORR) of 61.4% and a median duration of response (DoR) of 20.8 months.

In addition, the median progression-free survival (PFS) was 19.4 months, with an exploratory landmark analysis of overall survival (OS) also showing that an estimated 74% of patients remained alive at 18 months.

Prior analysis at 11.1 months of follow-up found an ORR of 60.9% and a median DoR of 14.8 months, as well as a median PFS of 16.4 months.

“These results reinforce the transformational potential of Enhertu in patients with previously treated HER2-positive metastatic breast cancer,” said José Baselga, executive vice president, Oncology R&D at AZ.

“With a median duration of response of greater than twenty months, the updated results of DESTINY-Breast01 are unprecedented. We look forward to further confirming the DESTINY-Breast01 findings with results from our phase III development programme for Enhertu,” he added.

Enhertu is approved in the US and Japan for the treatment of HER2-positive, unresectable or metastatic breast cancer following two or more prior anti-HER2 based regimens in the metastatic setting.

AZ and Daiichi are continuing to study Enhertu in a number of ongoing phase III trials in patients with HER2-expressing metastatic breast cancer.

This includes the DESTINY-Breast02 study, which is evaluating Enhertu as a third-line treatment for patients with HER2-positive metastatic breast cancer and the DESTINY-Breast03 which is testing Enhertu in the second-line setting.

Another study, DESTINY-Breast04, is investigating Enhertu in patients with metastatic breast cancer who have low expressions of HER2.