Can a Fallen Breast Rise Again? Enhertu's FDA Approval Brings New Hope to First-Line Treatment

AstraZeneca and Daiichi Sankyo’s Breakthrough in HER2-Positive Breast Cancer

AstraZeneca PLC (AZN) partnered with Japan-based Daiichi Sankyo to achieve a major milestone: FDA approval of Enhertu (trastuzumab deruxtecan) as a first-line treatment for patients with unresectable or metastatic HER2-positive breast cancer. The antibody-drug conjugate (ADC) is now authorized for use alongside Roche’s Perjeta (pertuzumab) in the United States, marking a significant shift in how doctors approach advanced breast cancer treatment. This approval received FDA priority review and Breakthrough Therapy designation, demonstrating the regulatory agency’s confidence in the drug’s potential.

The approval was facilitated through the FDA’s real-time oncology review (RTOR) program, which expedites the evaluation process for promising cancer therapies. Notably, Enhertu was already approved for second-line treatment in over 85 countries and holds approvals for HER2-targeted indications in lung and gastric cancers. However, this first-line breast cancer indication represents a transformative expansion—addressing patients at an earlier stage of disease progression.

Clinical Evidence: DESTINY-Breast09 Demonstrates Clear Superiority

The regulatory decision hinges on compelling data from the phase III DESTINY-Breast09 trial. Patients receiving Enhertu combined with Perjeta achieved a median progression-free survival (PFS) of 40.7 months, substantially outperforming the current standard chemotherapy regimen (taxane combined with cancer drugs Herceptin and Perjeta). Those treated with the traditional “THP” combination experienced a median PFS of just 26.7 months.

This translates to a 44% reduction in progression risk for the Enhertu-Perjeta arm—a clinically meaningful improvement that addresses a critical question for cancer patients: can a fallen breast rise again? For many HER2-positive patients, this data suggests the answer is increasingly affirmative, with extended survival periods offering both quality-of-life benefits and additional time for emerging therapies.

Financial Implications and Market Response

The approval triggers a $150 million milestone payment from AstraZeneca to Daiichi Sankyo, reflecting the commercial significance of this expanded indication. AZN shares have demonstrated robust performance, gaining 36.3% over the past year—outpacing the broader industry’s 12.1% rise. This stock performance reflects investor optimism about AstraZeneca’s oncology pipeline and the blockbuster potential of Enhertu in first-line breast cancer treatment.

Partnership Framework

The AstraZeneca-Daiichi Sankyo collaboration, formalized in March 2019, was subsequently expanded in July 2020 to encompass additional ADCs including Datroway (datopotamab deruxtecan). Under this arrangement, Daiichi Sankyo handles manufacturing and supply logistics, while recording U.S. sales of Enhertu—a structure that underscores the complementary strengths each partner brings to the oncology space.

This approval reinforces why advanced cancer therapeutics represent a compelling investment thesis for the biotech sector, as breakthrough treatments like Enhertu continue redefining treatment paradigms for HER2-positive patients globally.