AstraZeneca (LON:AZN) and Daiichi Sankyo Company, have today announced that the US Food and Drug Administration has approved Enhertu for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 based regimens in the metastatic setting.
This indication is approved under Accelerated Approval based on tumour response rate and duration of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.
Enhertu is a HER2-directed antibody-drug conjugate (ADC) and the FDA approval is based on the results of the registrational Phase II trial DESTINY-Breast01 of Enhertu (5.4mg/kg) monotherapy in patients with HER2-positive metastatic breast cancer. All patients received prior trastuzumab, trastuzumab emtansine and 66% had prior pertuzumab.
The Phase II trial results showed a confirmed objective response rate of 60.3% (n=111, 95% CI 52.9-67.4) including a 4.3% complete response rate (n=8) and a 56.0% partial response rate (n=103). A median duration of response of 14.8 months (95% CI 13.8-16.9) was demonstrated as of 1 August 2019.1 In addition, a median progression-free survival of 16.4 months (95% CI 12.7-not estimable), based upon a median duration of follow up of 11.1 months, was recently presented at the San Antonio Breast Cancer Symposium and published online in The New England Journal of Medicine.2
José Baselga, Executive Vice President, Oncology R&D, said: “Enhertu has shown impressive results in women with HER2-positive metastatic breast cancer, with the majority of women benefiting from treatment and the median duration of the response exceeding 14 months. With this first approval, we are proud to bring Enhertu to patients with high unmet need and we look forward to further exploring its potential in additional settings.”
Antoine Yver, Executive Vice President and Global Head, Oncology R&D, Daiichi Sankyo said: “The approval of Enhertu underscores that this specifically engineered HER2-directed antibody-drug conjugate is delivering on its intent to establish an important new treatment for patients with HER2-positive metastatic breast cancer. Since the beginning of our clinical trial programme four years ago, we have focused on the opportunity to transform the treatment landscape for patients with HER2-positive metastatic breast cancer, and we are extremely proud of how quickly we delivered Enhertu to patients in the US, as Enhertu represents one of the fastest-developed biologics in oncology.”
The safety of Enhertu has been evaluated in a pooled analysis from both the Phase II trial DESTINY-Breast01 and the earlier Phase I trial among a total of 234 patients with unresectable or metastatic HER2-positive breast cancer who received at least one dose of Enhertu (5.4mg/kg).
The most common adverse reactions (greater than or equal to 20% of patients) were nausea, fatigue, vomiting, alopecia and constipation. Interstitial lung disease (ILD)/pneumonitis occurred in 9% of patients. Fatal outcomes due to ILD/pneumonitis occurred in six patients (2.6%) – two deaths previously reported in the Phase I trial and four deaths previously reported in the Phase II trial DESTINY-Breast01. Following an initial ILD management programme already in place, a further monitoring, management and educational campaign on ILD/pneumonitis was launched in 2019. Patients and physicians should be aware of ILD/pneumonitis and patients should be actively screened and monitored for potential signs and symptoms. If ILD/pneumonitis is identified, it should be managed with dose modification and steroid treatment according to management guidelines.2
A regulatory submission for the treatment of patients with HER2-positive metastatic breast cancer has also been made to Japan’s Ministry of Health, Labour and Welfare based on the DESTINY-Breast01 and Phase I trials.
AstraZeneca and Daiichi Sankyo are exploring the further potential of Enhertu in HER2-breast cancer with three ongoing Phase III trials.
Financial considerations
Following US approval, an amount of $125m is due from AstraZeneca to Daiichi Sankyo as the first milestone payment in HER2-positive breast cancer. Upon approval, this will be capitalised together with the upfront payment already made earlier in the year 2019.
Future sales of Enhertu in the US will be recognised by Daiichi Sankyo. AstraZeneca will report its share of gross profit margin from the sales in the US as collaboration revenue in the Company’s financial statements. For further details on the financial arrangements, please consult the announcement of the collaboration agreement from March 2019.
