A New Milestone in the History of Antibody-Drug Conjugates (Background of EMA Approval)

Enhertu (ingredient: trastuzumab deruxtecan), co-developed by Daiichi Sankyo and AstraZeneca, has received final approval from the European Medicines Agency (EMA), marking its official entry into the European oncology market. This approval is based on the results of the DESTINY-Breast03 Phase 3 clinical trial, which involved patients with HER2-positive metastatic breast cancer. In the trial, Enhertu demonstrated overwhelming efficacy, reducing the risk of disease progression or death by 70% compared to the existing standard of care, Kadcyla (ingredient: trastuzumab emtansine) (hazard ratio of 0.30 for progression-free survival). This can be interpreted as regulatory recognition that goes beyond the limitations of existing antibody-drug conjugate (ADC) platform technologies.

Commercial Trajectory and Market Potential of a Blockbuster ADC Drug

This European approval is a commercial signal that solidifies the two companies' dominance in the global oncology market. Enhertu's global sales are expected to surge by approximately 26.3% from $3.754 billion in fiscal year 2024 to $4.982 billion in fiscal year 2025, placing it in the mega-blockbuster category. Global sales are projected to reach approximately $5.7 billion to $6.0 billion in fiscal year 2026, and the full-scale launch in the European market will undoubtedly be a major driver of this growth. With the HER2-targeted therapy market expected to exceed $22 billion by 2033, up from approximately $11.05 billion in 2025, Enhertu is poised to become a leading player in this vast market.

HER2-Low Paradigm Shift and Adaptive Expansion Strategy

Enhertu's true strength lies in its ability to expand the treatment scope beyond HER2-positive patients to include HER2-low patients, who were previously excluded from treatment. The DESTINY-Breast04 Phase 3 trial demonstrated that Enhertu nearly doubled the progression-free survival (PFS) of patients with HER2-low metastatic breast cancer, from 5.4 months with conventional chemotherapy to 10.1 months (hazard ratio of 0.51, p-value less than 0.001). This clinical evidence was a key factor in the EMA's decision to approve the expansion of indications to include not only breast cancer but also gastric cancer, non-small cell lung cancer (NSCLC), and solid tumors regardless of cancer type. This provides innovative treatment options for patients and dramatically extends the lifecycle of the pipeline, creating a win-win strategy.

Lessons from the Bio Ecosystem and Deal Structure from a Venture Capital Perspective

The birth of this innovative drug was underpinned by a massive global co-development agreement worth $6.9 billion, signed in March 2019. The $1.35 billion upfront payment and $5.5 billion in milestone payments made by AstraZeneca to Daiichi Sankyo have become a standard model for deals in the bio industry. From a venture capital (VC) and investor perspective, this is a prime example of how a biotech company with unique platform technology can maximize its corporate value through collaboration with a global pharmaceutical company. The approval of Enhertu will serve as a strong precedent for assigning valuation premiums to later-stage companies developing early-stage ADC assets.