T-DXd Plus Pertuzumab Type II Variation Application Acceptance Breakdown
- The EMA validated a Type II variation for T-DXd plus pertuzumab in first-line unresectable/metastatic HER2-positive breast cancer.
- T-DXd/pertuzumab improved median PFS vs THP (40.7 vs 26.9 months; HR, 0.56; 95% CI, 0.44-0.71; P < .00001) with consistent subgroup benefit.
- The company cited the EU validation as a step toward broader global access following a recent US approval in a first-line standard-of-care setting.
How was the DESTINY-Breast09 trial designed?
In the multicenter, open-label phase 3 DESTINY-Breast09 trial, adults with pathologically confirmed advanced or metastatic HER2-positive breast cancer were randomly assigned in a 1:1:1 fashion to 1 of 3 treatment arms.2,3 Patients received T-DXd at 5.4 mg/kg every 3 weeks plus placebo (n = 387), T-DXd plus pertuzumab (n = 383), or investigator’s choice of a taxane (paclitaxel or docetaxel) in combination with trastuzumab and pertuzumab (THP; n = 387).
The primary end point was PFS assessed by blinded independent central review. Overall survival (OS) served as a key secondary end point. Additional secondary end points included PFS per investigator assessment, objective response rate, duration of response, and safety/tolerability.
Eligible patients were 18 years or older with no prior chemotherapy or HER2-directed therapy for advanced/metastatic disease; patients could have received up to 1 prior line of endocrine therapy in the metastatic setting. Key inclusion criteria also required adequate organ and bone marrow function and an ECOG performance status of 0 or 1. Random assignment was stratified by de novo vs recurrent disease, hormone receptor status (positive vs negative), and the presence vs absence of detectable PIK3CA mutations.
What safety profile was observed with the combination in DESTINY-Breast09?
The safety findings for T-DXd plus pertuzumab in DESTINY-Breast09 were consistent with the established profiles of the individual agents.2 In the T-DXd and THP arms, respectively, the most common any-grade treatment-emergent adverse effects (TEAEs) were nausea (71.1% vs 28.8%), diarrhea (55.9% vs 54.2%), neutropenia (48.8% vs 44.5%), and fatigue (48.3% vs 34.6%). The most frequent grade 3 or higher TEAEs included neutropenia (23.9% vs 33.2%), hypokalemia (10.2% vs 1.6%), and anemia (8.4% vs 3.7%).
References
- Enhertu plus pertuzumab Type II variation application validated in the EU as first-line treatment of patients with HER2-positive metastatic breast cancer. News release. Daiichi Sankyo. January 19, 2026. Accessed January 19, 2026. https://www.daiichisankyo.com/files/news/pressrelease/pdf/202601/20260119_E2.pdf
- Tolaney S, Jiang Z, Zhang Q, et al. Trastuzumab deruxtecan (T-DXd) + pertuzumab (P) vs taxane + trastuzumab + pertuzumab (THP) for first-line (1L) treatment of patients (pts) with human epidermal growth factor receptor 2–positive (HER2+) advanced/metastatic breast cancer (a/mBC): interim results from DESTINY-Breast09. J Clin Oncol. 2025;43(suppl 17):LBA1008. doi:10.1200/JCO.2025.43.17_suppl.LBA1008
- Trastuzumab Deruxtecan (T-DXd) with or without pertuzumab versus taxane, trastuzumab and pertuzumab in HER2-positive metastatic breast cancer (DESTINY-Breast09). ClinicalTrials.gov. Updated May 6, 2025. Accessed May 31, 2025. https://clinicaltrials.gov/study/NCT04784715