Positive high-level results from the head-to-head DESTINY-Breast03 Phase III trial showed that Enhertu (trastuzumab deruxtecan), the AstraZeneca and Daiichi Sankyo Company, Limited (Daiichi Sankyo) HER2-directed antibody drug conjugate (ADC), demonstrated superiority over trastuzumab emtansine (T-DM1).

At a planned interim analysis, the Independent Data Monitoring Committee (IDMC) concluded that DESTINY-Breast03 met the primary endpoint of progression-free survival (PFS) showing a highly statistically significant and clinically meaningful improvement for patients with HER2-positive, unresectable and/or metastatic breast cancer previously treated with trastuzumab and a taxane.

In DESTINY-Breast03, Enhertu also showed a strong trend toward improved overall survival (OS) compared to T-DM1 in a key secondary endpoint, although the OS data are still immature. The safety profile of Enhertu was consistent with previous clinical trials, with no new safety concerns identified and no Grade 4 or 5 treatment-related interstitial lung disease events.

Susan Galbraith, Executive Vice President, Oncology R&D, said: "There is a continued need for new options and better outcomes for patients with HER2-positive metastatic breast cancer who often experience disease progression after initial treatment with available standards of care. These transformative progression-free survival results demonstrate the superiority of Enhertu compared to T-DM1, and the encouraging safety data may open future opportunities to bring this benefit to patients in earlier treatment settings."

Ken Takeshita, Global Head, Research and Development, Daiichi Sankyo, said: "DESTINY-Breast03 is the first global Phase III head-to-head trial of Enhertu against an active control and supports the potential of this medicine to become the new standard of care for patients with HER2-positive metastatic breast cancer following initial treatment with trastuzumab and a taxane. We believe this highly sophisticated and specifically engineered ADC is fulfilling its promise to reshape the treatment of HER2-positive metastatic breast cancer, with the goal to move into earlier lines of treatment for HER2-positive breast cancer and many other HER2-expressing tumour types across our broad clinical trial programme."

The data will be presented at an upcoming medical meeting and shared with health authorities.

Enhertu is approved 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 in the US, Japan, the EU and several other countries based on the results from the DESTINY-Breast01 trial.

Enhertu is being further assessed in a comprehensive clinical development programme evaluating efficacy and safety across multiple HER2-targetable cancers, including breast, gastric, lung and colorectal cancers.

HER2-positive breast cancer

Breast cancer remains the most common cancer and is one of the leading causes of cancer-related deaths in women worldwide.[1] More than two million patients with breast cancer were diagnosed in 2020, resulting in nearly 685,000 deaths globally.[1 ]Approximately one in five patients with breast cancer are considered HER2-positive.[2]

HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumours, including breast, gastric, lung and colorectal cancers.[3] HER2 protein overexpression may occur as a result of HER2 gene amplification and is often associated with aggressive disease and a poor prognosis in breast cancer.[4 ]

Despite initial treatment with trastuzumab and a taxane, patients with HER2-positive metastatic breast cancer will often experience disease progression.[5] More effective options are needed to further delay progression and extend survival.[5-7]

DESTINY-Breast03

DESTINY-Breast03 is a global head-to-head, randomised, open-label, registrational Phase III trial evaluating the safety and efficacy of Enhertu (5.4mg/kg) versus T-DM1 in patients with HER2-positive unresectable and/or metastatic breast cancer previously treated with trastuzumab and a taxane. The primary efficacy endpoint of DESTINY-Breast03 is PFS based on blinded independent central review. Secondary efficacy endpoints include OS, objective response rate, duration of response, clinical benefit rate, PFS based on investigator assessment and safety.

DESTINY-Breast03 enrolled approximately 500 patients at multiple sites in Asia, Europe, North America, Oceania and South America. For more information about the trial, visit ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT03529110).

Enhertu

Enhertu is a HER2-directed ADC. Designed using Daiichi Sankyo's proprietary DXd ADC technology, Enhertu is the lead ADC in the oncology portfolio of Daiichi Sankyo and the most advanced programme in AstraZeneca's ADC scientific platform. Enhertu consists of a HER2 monoclonal antibody attached to a topoisomerase I inhibitor payload, an exatecan derivative, via a stable tetrapeptide-based cleavable linker.

Enhertu (5.4mg/kg) is approved in Canada, the EU, Israel, Japan, the UK and the US 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 based on the results from the DESTINY-Breast01 trial.

Enhertu (6.4mg/kg) is also approved in Israel, Japan and the US for the treatment of adult patients with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who have received a prior trastuzumab-based regimen based on the results from the DESTINY-Gastric01 trial.

Enhertu development programme

A comprehensive development programme is underway globally, evaluating the efficacy and safety of Enhertu monotherapy across multiple HER2-targetable cancers, including breast, gastric, lung and colorectal cancers. Trials in combination with other anticancer treatments, such as immunotherapy, are also underway.

Enhertu was highlighted in the Clinical Cancer Advances 2021 report as one of two significant advancements in the "ASCO Clinical Advance of the Year: Molecular Profiling Driving Progress in GI Cancers," based on data from both the DESTINY-CRC01 and DESTINY-Gastric01 trials, as well as one of the targeted therapy advances of the year in non-small cell lung cancer (NSCLC), based on the interim results of the HER2-mutated cohort of the DESTINY-Lung01 trial.

In May 2020, Enhertu also received Breakthrough Therapy Designation for the treatment of patients with metastatic NSCLC whose tumours have a HER2-mutation and with disease progression on or after platinum-based therapy.

Daiichi Sankyo collaboration

Daiichi Sankyo and AstraZeneca entered into a global collaboration to jointly develop and commercialise Enhertu (a HER2-directed ADC) in March 2019, and datopotamab deruxtecan (DS-1062; a TROP2-directed ADC) in July 2020, except in Japan where Daiichi Sankyo maintains exclusive rights. Daiichi Sankyo is responsible for manufacturing and supply of Enhertu and datopotamab deruxtecan.

AstraZeneca in breast cancer

Driven by a growing understanding of breast cancer biology, AstraZeneca is starting to challenge, and redefine, the current clinical paradigm for how breast cancer is classified and treated to deliver even more effective treatments to patients in need - with the bold ambition to one day eliminate breast cancer as a cause of death.

AstraZeneca has a comprehensive portfolio of approved and promising compounds in development that leverage different mechanisms of action to address the biologically diverse breast cancer tumour environment. AstraZeneca aims to continue to transform outcomes for HR-positive breast cancer with foundational medicines Faslodex (fulvestrant) and Zoladex (goserelin) and the next-generation oral SERD and potential new medicine AZD9833.

PARP inhibitor, Lynparza (olaparib) is a targeted treatment option for metastatic breast cancer patients with an inherited BRCA mutation. AstraZeneca with MSD (Merck & Co., Inc. in the US and Canada) continue to research Lynparza in metastatic breast cancer patients with an inherited BRCA mutation and are exploring new opportunities to treat these patients earlier in their disease.

Building on the first approval of Enhertu, a HER2-directed ADC, in previously treated HER2-positive metastatic breast cancer, AstraZeneca and Daiichi Sankyo are exploring its potential in earlier lines of treatment and in new breast cancer settings. To bring much needed treatment options to patients with triple-negative breast cancer, an aggressive form of breast cancer, AstraZeneca is testing immunotherapy Imfinzi (durvalumab) in combination with other oncology medicines, including Lynparza and Enhertu, investigating the potential of AKT kinase inhibitor, capivasertib, in combination with chemotherapy, and collaborating with Daiichi Sankyo to explore the potential of TROP2-directed ADC, datopotamab deruxtecan.

AstraZeneca in oncology

AstraZeneca is leading a revolution in oncology with the ambition to provide cures for cancer in every form, following the science to understand cancer and all its complexities to discover, develop and deliver life-changing medicines to patients.

The Company's focus is on some of the most challenging cancers. It is through persistent innovation that AstraZeneca has built one of the most diverse portfolios and pipelines in the industry, with the potential to catalyse changes in the practice of medicine and transform the patient experience.

AstraZeneca has the vision to redefine cancer care and, one day, eliminate cancer as a cause of death.

AstraZeneca

AstraZeneca (LSE/STO/Nasdaq: AZN) is a global, science-led biopharmaceutical company that focuses on the discovery, development, and commercialisation of prescription medicines in Oncology, Rare Diseases, and BioPharmaceuticals, including Cardiovascular, Renal & Metabolism, and Respiratory & Immunology. Based in Cambridge, UK, AstraZeneca operates in over 100 countries and its innovative medicines are used by millions of patients worldwide. Please visit astrazeneca.com (http://www.astrazeneca.com/) and follow the Company on Twitter @AstraZeneca (https://twitter.com/AstraZeneca).

Contacts

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References

1. Sung H, et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin. 2021; 10.3322/caac.21660.

2. Ahn S, et al. HER2 status in breast cancer: changes in guidelines and complicating factors for interpretation. J Pathol Transl Med. 2020; 54(1): 34-44.

3. Iqbal N, et al. Human Epidermal Growth Factor Receptor 2 (HER2) in Cancers: Overexpression and Therapeutic Implications. Mol Biol Int. 2014;852748.

4. Pillai R, et al. HER2 mutations in lung adenocarcinomas: A report from the Lung Cancer Mutation Consortium. Cancer. 2017;1;123(21):4099-4105.

5. Barok M, et al. Trastuzumab emtansine: mechanism of action and drug resistance. Breast Cancer Res. 2014; 16(2):209.

6. Mounsey L, et al. Changing Natural History of HER2-Positive Breast Cancer Metastatic to the Brain in the Era of New Targeted Therapies. Clin Breast Cancer. 2018; 18(1):29-37.

7. Martinez-S Sáez O, et al. Current and Future Management of HER2-Positive Metastatic Breast Cancer. JCO Oncol Pract. 2021. 10.1200/OP.21.00172.