Neoadjuvant Dalpiciclib + AI → SHR-A1811 for HR+/HER2-Low Breast Cancer

This is a phase II, single-arm, prospective exploratory study to evaluate the efficacy and safety of neoadjuvant dalpiciclib (a CDK4/6 inhibitor) plus an aromatase inhibitor (AI) followed by SHR-A1811 (an anti-HER2 antibody-drug conjugate) in patients with intermediate-to-high risk, hormone receptor-positive (HR+), HER2-low breast cancer. Patients will receive dalpiciclib (125 mg orally once daily, days 1-21, every 4 weeks) plus AI (anastrozole 1 mg, letrozole 2.5 mg, or exemestane 25 mg once daily) for 4 cycles, followed by SHR-A1811 (4.8 mg/kg intravenously every 3 weeks) for 4 cycles. The primary endpoint is objective response rate (ORR) per RECIST 1.1. Secondary endpoints include pathological complete response (pCR), breast-conserving surgery rate, event-free survival (EFS), change in Ki-67 index, and safety. A total of 20 participants will be enrolled.