Positive results from the DESTINY-Breast05 Phase III trial showed Enhertu (trastuzumab deruxtecan) demonstrated a highly statistically significant and clinically meaningful improvement in invasive disease-free survival (IDFS) in patients with a high risk of disease recurrence. The trial compared Enhertu with trastuzumab emtansine (T-DM1) as a post-neoadjuvant treatment (after surgery) in patients with HER2-positive early breast cancer with residual invasive disease in the breast and/or axillary lymph nodes after neoadjuvant treatment.

Results showed Enhertu significantly reduced the risk of invasive disease recurrence or death by 53% compared with T-DM1 as a post-neoadjuvant treatment (based on an IDFS hazard ratio [HR] of 0.47, 95% confidence interval [CI] 0.34-0.66, p<0.0001). At three years, 92.4% of patients in the Enhertu arm were alive and free of invasive disease, compared with 83.7% of those in the T-DM1 arm. The IDFS results were consistent across all prespecified subgroups.

Enhertu also significantly reduced the risk of disease recurrence or death (disease-free survival [DFS]), a key secondary endpoint, by 53% (HR 0.47; 95% CI 0.34-0.66; p<0.0001).  Further, Enhertu lowered the risk of distant disease recurrence (distant recurrence-free interval [DRFI]) by 51% and the risk of brain metastases (brain metastasis-free interval [BMFI]) by 36% versus T-DM1.

Overall survival (OS) was not mature at the time of this planned interim analysis (2.9% maturity at data cut-off) and will be assessed in future analyses (HR 0.61; 95% CI 0.34-1.10).

Charles Geyer, MD, Chief Scientific Officer of the National Surgical Adjuvant Breast and Bowel Project Foundation (NSABP) Foundation, Professor of Medicine at the UPMC Hillman Cancer Center and principal investigator for the trial, said: "For patients with residual disease after neoadjuvant treatment, the post-neoadjuvant setting represents a critical second opportunity to reduce recurrence risk, and in DESTINY-Breast05 Enhertu reduced the risk of early recurrence or death by 53 per cent compared to the current standard of T-DM1. These results, coupled with the safety data from the trial, are likely to transform clinical practice in the post-neoadjuvant setting for patients with high-risk disease, with the potential for Enhertu to set a new standard of care."

Susan Galbraith, Executive Vice President, Oncology Haematology R&D, AstraZeneca, said: "Progress in treating HER2-positive early breast cancer has been significant, yet managing patients at a higher-risk of recurrence remains challenging. These landmark data, alongside those from DESTINY-Breast11, underscore the potential of Enhertu to become a foundational treatment in early-stage breast cancer, increasing the likelihood that more patients could be cured in this setting."

Ken Takeshita, Global Head, R&D, Daiichi Sankyo, said: "The results of DESTINY-Breast05 demonstrate a clear benefit of Enhertu over the current standard of care in patients with high-risk HER2-positive early breast cancer following surgery, improving their chance for sustained long-term outcomes. These results, coupled with the results of DESTINY-Breast11, illustrate the continued promise of Enhertu to move earlier in the breast cancer treatment paradigm where it can have the greatest impact on the lives of patients."

Summary of Results: DESTINY-Breast05ⁱ

TDM-1, trastuzumab emtansine; CI, confidence interval; HR, hazard ratio; IDFS, invasive disease-free survival; DFS, disease-free survival; DRFI, distant recurrence-free interval; BMFI, brain-metastasis-free interval; OS, overall survival

ⁱ Data cut-off 2 July 2025

ⁱⁱ IDFS is defined as the time from randomisation until the date of first occurrence of one of the following events: recurrence of ipsilateral invasive breast tumour, recurrence of ipsilateral locoregional invasive breast cancer, contralateral invasive breast cancer, a distant disease recurrence or death from any cause; based on investigator assessment; statistically evaluated using the pre-specified hierarchical testing procedure

ⁱⁱⁱ DFS is defined as the time between randomisation and the date of the first occurrence of an IDFS event per STEEP criteria, including second primary non-breast cancer event, or contralateral or ipsilateral ductal carcinoma in situ (DCIS); based on investigator assessment; statistically evaluated using the pre-specified hierarchical testing procedure

^iv DRFI is defined as the time between randomisation and the date of distant breast cancer recurrence; based on investigator assessment

^v BMFI is defined as the time between randomisation and the date of documentation of brain metastases or leptomeningeal disease; based on investigator assessment

^vi 2.9% maturity

The safety profile of Enhertu observed in DESTINY-Breast05 was consistent with its known profile with no new safety concerns identified. Grade 3 or higher treatment emergent adverse events (AEs) rates were comparable between Enhertu and T-DM1 (50.6% versus 51.9%). Rates of interstitial lung disease (ILD) were low in both arms with ILD events occurring in 9.6% of the Enhertu arm and 1.6% of the T-DM1 arm. The majority of ILD events were low Grade (Grade 1 or 2). There were no Grade 3 or higher ILD events for T-DMI. There were seven Grade 3 events and no Grade 4 events in the Enhertu arm. There were two Grade 5 events in the Enhertu arm as determined by an independent adjudication committee.

The DESTINY-Breast05 results (abstract #LBA1) will be presented today during Presidential Symposium I alongside the results of the DESTINY-Breast11 Phase III trial (abstract #291O) at the European Society for Medical Oncology (ESMO) 2025 Congress in Berlin, Germany.

DESTINY-Breast05 was conducted in collaboration with the NSABP, the German Breast Group (GBG), Arbeitsgemeinschaft Gynäkologische Onkologie (AGO-B) and SOLTI Breast Cancer Research Group.

Enhertu is a specifically engineered HER2-directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo and being jointly developed and commercialised by AstraZeneca and Daiichi Sankyo.

Notes

Post neoadjuvant treatment for HER2-positive early breast cancer

Breast cancer is the second most common cancer and one of the leading causes of cancer-related deaths worldwide.¹ More than two million breast cancer cases were diagnosed in 2022, with more than 665,000 deaths globally.¹

HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumours including breast cancer.² HER2 protein overexpression may occur as a result of HER2 gene amplification and is often associated with aggressive disease and poor prognosis in breast cancer.² Approximately one in five cases of breast cancer are considered HER2-positive.³

For patients with HER2-positive early breast cancer, achieving pCR with neoadjuvant treatment is the earliest indicator of improved long-term survival.⁴ However, approximately half of patients who receive neoadjuvant treatment do not reach pCR and have poorer long-term outcomes, putting them at increased risk of disease recurrence.^5-9

Post-neoadjuvant therapy represents a key opportunity to minimise the risk of recurrence and prevent progression to metastatic disease for patients with residual disease. Despite receiving additional treatment with T-DMI in the post-neoadjuvant setting, approximately 20% of patients still experience invasive disease or death and no reduction in the risk of CNS recurrence.^10,11 Once patients are diagnosed with metastatic disease, the five-year survival rate drops from nearly 90% to approximately 30%.¹²

New treatment options are needed in the early breast cancer setting to help reduce the likelihood of disease progression and improve long-term outcomes for more patients.

DESTINY-Breast05

DESTINY-Breast05 is a global, multicentre, randomised, open-label, Phase III trial evaluating the efficacy and safety of Enhertu (5.4 mg/kg) versus T-DM1 in patients with HER2-positive early breast cancer with residual invasive disease in breast and/or axillary lymph nodes following neoadjuvant therapy and a high risk of recurrence. High risk of recurrence was defined as presentation with inoperable cancer (prior to neoadjuvant therapy) or pathologically positive axillary lymph nodes following neoadjuvant therapy.

The primary endpoint of DESTINY-Breast05 is investigator-assessed IDFS. IDFS is defined as the time from randomisation until first recurrence, distant recurrence or death from any cause. The key secondary endpoint is investigator-assessed disease-free survival. Other secondary endpoints include OS, distant recurrence-free interval, brain metastases-free interval and safety.

DESTINY-Breast05 enrolled 1,635 patients in Asia, Europe, North America, Oceania and South America. For more information about the trial, visit ClinicalTrials.gov.

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 number of topoisomerase I inhibitor payloads (an exatecan derivative, DXd) via tetrapeptide-based cleavable linkers.

Enhertu (5.4 mg/kg) is approved in more than 85 countries/regions worldwide for the treatment of adult patients with unresectable or metastatic HER2-positive (immunohistochemistry [IHC] 3+ or in-situ hybridisation (ISH)+) breast cancer who have received a prior anti-HER2-based regimen, either in the metastatic setting or in the neoadjuvant or adjuvant setting, and have developed disease recurrence during or within six months of completing therapy based on the results from the DESTINY-Breast03 trial.

Enhertu (5.4 mg/kg) is approved in more than 85 countries/regions worldwide for the treatment of adult patients with unresectable or metastatic HER2-low (IHC 1+ or IHC 2+/ISH-) breast cancer who have received a prior systemic therapy in the metastatic setting or developed disease recurrence during or within six months of completing adjuvant chemotherapy based on the results from the DESTINY-Breast04 trial.

Enhertu (5.4 mg/kg) is approved in more than 45 countries/regions worldwide for the treatment of adult patients with unresectable or metastatic HR-positive, HER2-low (IHC 1+ or IHC 2+/ ISH-) or HER2-ultralow (IHC 0 with membrane staining) breast cancer, as determined by a locally or regionally approved test, that have progressed on one or more endocrine therapies in the metastatic setting based on the results from the DESTINY-Breast06 trial.

Enhertu (5.4 mg/kg) is approved in more than 60 countries/regions worldwide for the treatment of adult patients with unresectable or metastatic non-small cell lung cancer (NSCLC) whose tumours have activating HER2 (ERBB2) mutations, as detected by a locally or regionally approved test, and who have received a prior systemic therapy based on the results from the DESTINY-Lung02 and/or DESTINY-Lung05 trials. Continued approval in China and the U.S. for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

Enhertu (6.4 mg/kg) is approved in more than 70 countries/regions worldwide for the treatment of adult patients with locally advanced or metastatic HER2-positive (IHC 3+ or IHC 2+/ISH+) gastric or gastroesophageal junction (GEJ) adenocarcinoma who have received a prior trastuzumab-based regimen based on the results from the DESTINY-Gastric01, DESTINY-Gastric02 and/or DESTINY-Gastric06 trials. Continued approval in China for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

Enhertu (5.4 mg/kg) is approved in more than 10 countries/regions worldwide for the treatment of adult patients with unresectable or metastatic HER2-positive (IHC 3+) solid tumours who have received prior systemic treatment and have no satisfactory alternative treatment options based on efficacy results from the DESTINY-PanTumor02, DESTINY-Lung01 and DESTINY-CRC02 trials. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

Enhertu development programme

A comprehensive global clinical development programme is underway evaluating the efficacy and safety of Enhertu as a monotherapy or in combination or sequentially with other cancer medicines across multiple HER2-targetable cancers.

Daiichi Sankyo collaboration

AstraZeneca and Daiichi Sankyo entered into a global collaboration to jointly develop and commercialise Enhertu in March 2019 and Datroway (datopotamab deruxtecan) in July 2020, except in Japan where Daiichi Sankyo maintains exclusive rights for each ADC. Daiichi Sankyo is responsible for the manufacturing and supply of Enhertu and Datroway.

AstraZeneca in breast cancer
Driven by a growing understanding of breast cancer biology, AstraZeneca is challenging, and redefining, 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.

With Enhertu, AstraZeneca and Daiichi Sankyo are aiming to improve outcomes in previously treated HER2-positive, HER2-low and HER2-ultralow metastatic breast cancer, and are exploring its potential in earlier lines of treatment and in new breast cancer settings.

In HR-positive breast cancer, AstraZeneca continues to improve outcomes with foundational medicines Faslodex (fulvestrant) and Zoladex (goserelin) and aims to reshape the HR-positive space with first-in-class AKT inhibitor, Truqap (capivasertib), the TROP2-directed ADC, Datroway (datopotamab deruxtecan), and next-generation oral SERD and potential new medicine camizestrant.

PARP inhibitor Lynparza (olaparib) is a targeted treatment option that has been studied in early and 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 these settings. AstraZeneca is also exploring the potential of saruparib, a potent and selective inhibitor of PARP1, in combination with camizestrant in BRCA-mutated, HR-positive, HER2-negative advanced breast cancer.

To bring much-needed treatment options to patients with triple-negative breast cancer, an aggressive form of breast cancer, AstraZeneca is collaborating with Daiichi Sankyo to evaluate the potential of Datroway alone and in combination with immunotherapy Imfinzi (durvalumab).

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's innovative medicines are sold in more than 125 countries and used by millions of patients worldwide. Please visit astrazeneca.com and follow the Company on Social Media @AstraZeneca.

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