FDA Approves First New Frontline HER2-Positive Breast Cancer Therapy in Over a Decade

December 16, 2025

The U.S. Food and Drug Administration (FDA) has approved the combination of Enhertu (fam-trastuzumab deruxtecan-nxki) and Perjeta (pertuzumab) for the initial treatment of adult patients with unresectable or metastatic HER2-positive breast cancer. The decision, announced Monday, marks a pivotal shift in the standard of care for this aggressive form of cancer, replacing a treatment regimen that has been the global benchmark for more than 12 years.

The approval is based on results from the landmark Phase 3 DESTINY-Breast09 trial, which demonstrated that the new combination significantly extended the time patients lived without their disease worsening compared to the previous standard therapy.

A New Standard for “First-Line” Care

For over a decade, the standard first-line treatment for patients diagnosed with metastatic HER2-positive breast cancer has been the “THP” regimen—a combination of a taxane chemotherapy drug plus two antibody therapies, trastuzumab and pertuzumab. While effective, patients eventually develop resistance to this regimen.

The newly approved therapy replaces the traditional chemotherapy component with Enhertu, an antibody-drug conjugate (ADC) developed by Daiichi Sankyo and AstraZeneca. Enhertu works like a “smart bomb,” delivering a potent chemotherapy payload directly to cancer cells that express the HER2 protein, minimizing damage to healthy cells.

“Trastuzumab deruxtecan [Enhertu] plus pertuzumab is the only first-line treatment approved in more than a decade to demonstrate a statistically significant improvement in progression-free survival over the current standard regimen,” said Dr. Sara Tolaney, Chief of the Division of Breast Oncology at Dana-Farber Cancer Institute and principal investigator for the trial. “With a median progression-free survival exceeding three years, this combination should become a new first-line standard of care.”

Unprecedented Clinical Results

The FDA’s decision was driven by data from the DESTINY-Breast09 trial, which enrolled 1,157 patients globally. The study compared the new Enhertu-based combination against the standard THP regimen.

Key findings included:

• Extended Survival Without Progression: Patients receiving Enhertu plus pertuzumab achieved a median progression-free survival (PFS) of 40.7 months, compared to 26.9 months for those on the standard THP regimen.

• Risk Reduction: The new therapy reduced the risk of disease progression or death by 44% (Hazard Ratio: 0.56).

• Tumor Response: The objective response rate (the percentage of patients whose tumors shrank) was 87% with the new combination, versus 81% with the standard treatment.

Expert Perspectives and Clinical Impact

Oncologists not involved in the study have greeted the news with optimism, noting that the data represents a major leap forward for patient outcomes.

“The outcomes from this trial were impressive,” said Dr. Laura Huppert, an assistant professor of medicine at the University of California, San Francisco (UCSF), in an interview with OncLive regarding the trial data presented earlier this year. She noted that the nearly 14-month improvement in progression-free survival is “statistically significant” and likely “practice changing.”

However, the shift also prompts new considerations for clinicians regarding long-term treatment planning. “Major questions for me are, how do we sequence therapies?” noted Dr. Claudine Isaacs, a specialist at Georgetown Lombardi Comprehensive Cancer Center, in commentary for the American Society of Clinical Oncology (ASCO). Because Enhertu is now being used in the first line, doctors will need to determine the best options for patients if the cancer eventually progresses, as Enhertu was previously the go-to “second-line” option.

Safety and Important Warnings

While the efficacy data is robust, the safety profile of Enhertu requires careful management. The FDA approval includes a Boxed Warning for Interstitial Lung Disease (ILD) and Embryo-Fetal Toxicity.

In the clinical trial, adjudicated drug-related ILD (lung inflammation) occurred in 12.1% of patients receiving the Enhertu combination, compared to only 1% in the standard arm. While most cases were mild (Grade 1 or 2), severe cases can be fatal, and patients require monitoring for symptoms such as cough or difficulty breathing.

Common adverse reactions included nausea, fatigue, alopecia (hair loss), and stomatitis (mouth sores).

Implications for Public Health

Breast cancer remains the second most common cancer worldwide. Approximately 15-20% of breast cancers are HER2-positive, a subtype that tends to grow and spread faster than others but responds well to targeted therapies.

“Since its initial approval six years ago, Enhertu has transformed the treatment of HER2-positive metastatic breast cancer,” said Ken Keller, Global Head of Oncology Business at Daiichi Sankyo. “With this approval… Enhertu once again offers significant improvements and has practice-changing potential.”

This approval emphasizes the growing dominance of antibody-drug conjugates (ADCs) in oncology, moving potent targeted therapies earlier in the treatment timeline to prevent disease progression for as long as possible.

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.

References

1. FDA Approval Notification: U.S. Food and Drug Administration. “FDA approves fam-trastuzumab deruxtecan-nxki with pertuzumab for unresectable or metastatic HER2-positive breast cancer.” December 15, 2025. [FDA.gov]