T-DXd Based Therapy Followed by Endocrine Therapy Plus Dual HER2 Blockade in First-line HER2+/ HR+ Metastatic Breast Cancer and Retreatment With T-DXd

This study will evaluate a structured sequential treatment strategy starting with T-DXd + pertuzumab upfront therapy, followed by an optimized maintenance therapy with dual HER2+blockade + CDK4/6i + ET and the opportunity to retreat with T-DXd once patients progress under maintenance aimed to maximizing disease control, optimizing tolerability, and preserving T-DXd as a future therapeutic option, while ensuring participant safety and regulatory compliance in participants with HER2+/HR+ advanced/metastatic breast cancer.

NCT Number	NCT07683754
Lead Sponsor	Daiichi Sankyo Collaborators: AstraZeneca
Conditions	Advanced Breast Cancer, Metastatic Breast Cancer, HER2 Positive, HR Positive
Enrollment	200 participants
Start Date	2026-09-04
Primary Completion	2030-07-04 (estimated)
Study Completion	2030-08-28 (estimated)
Updated on ClinicalTrials.gov	2026-07-23