Efficacy and Safety of Trastuzumab Rezetecan Followed by CDK4/6 Inhibitors and Endocrine Therapy in HR+/HER2-Low/Ultra-Low Advanced Breast Cancer

This multicenter, prospective phase II clinical trial evaluates the efficacy and safety of sequential Trastuzumab rezetecan followed by dalpiciclib plus endocrine therapy (fulvestrant or aromatase inhibitors) in 45 patients with HR+/HER2-low/ultra-low advanced breast cancer. Enrolled patients will receive Trastuzumab rezetecan monotherapy for 6-8 cycles until clinical benefit, then transition to CDK4/6 inhibitors with endocrine therapy until disease progression or unacceptable toxicity. The primary endpoint is progression-free survival (PFS), with secondary endpoints including objective response rate (ORR), overall survival (OS), and treatment-related adverse events (TRAEs). The study will be conducted at Sun Yat-sen Memorial Hospital and collaborating centers.

NCT Number	NCT07037199
Lead Sponsor	Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University
Conditions	Advanced Breast Cancer
Enrollment	45 participants
Start Date	2025-08-18
Primary Completion	2028-06-30 (estimated)
Study Completion	2030-06-30 (estimated)
Updated on ClinicalTrials.gov	2025-12-31