AstraZeneca and Daiichi Sankyo Report Positive Phase 3 Results for Enhertu in Early Breast Cancer

AstraZeneca and Daiichi Sankyo have announced promising outcomes from a late-stage clinical trial of Enhertu (trastuzumab deruxtecan), their HER2-targeting antibody drug conjugate. This study, known as the phase 3 DESTINY-Breast11 trial, focused on a specific group of early-stage breast cancer patients deemed high-risk and locally advanced with HER2-positive tumors.

In the trial, Enhertu was tested alongside paclitaxel, trastuzumab, and pertuzumab (THP) and was compared to the standard treatment protocol. The conventional approach includes dose-dense doxorubicin and cyclophosphamide followed by THP. The key goal was to evaluate the effectiveness of the Enhertu regimen in achieving a pathologic complete response (pCR), which is characterized by the absence of invasive cancer cells in both the excised breast tissue and lymph nodes post-treatment.

The study results highlighted that Enhertu significantly improved the pCR rate compared to the standard of care. Achieving pCR in the context of early-stage HER2-positive breast cancer is crucial, as it is linked to better long-term patient outcomes. However, it is important to note that many patients who undergo neoadjuvant chemotherapy with standard treatments do not reach pCR.

Additionally, the research observed a favorable trend in event-free survival for patients receiving Enhertu, although the data was not yet mature at the time of analysis and requires further evaluation. Safety assessments revealed that the Enhertu regimen presented an improved safety profile compared to the standard treatment, with the side effect profiles of Enhertu and THP aligning with the known profiles of these medications.

Breast cancer ranks as the second most prevalent cancer globally, and about a third of patients with early-stage diagnoses are classified as high-risk. Enhertu, which is already approved for treating certain metastatic breast cancer patients, specifically targets HER2, a protein that promotes tumor growth found on the surface of various types of tumors.

Susan Galbraith, the executive vice president of oncology hematology research and development at AstraZeneca, expressed optimism regarding the findings, stating, "Enhertu is already an important treatment option in the metastatic setting, and this data has the potential to allow this medicine to move into early stages of disease where cure is possible."

Similarly, Ken Takeshita, global head of research and development at Daiichi Sankyo, emphasized the significance of the trial's outcomes by stating, "These top-line results from DESTINY-Breast11 demonstrate that Enhertu followed by THP could offer patients with HER2-positive breast cancer a promising new treatment approach prior to surgery, setting more patients on a path towards a potential cure."

The companies plan to present the detailed findings from the trial at a forthcoming medical conference. Additionally, they intend to communicate these results with regulatory authorities to potentially expand the usage of Enhertu to earlier stages of breast cancer treatment.