HR Positive/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.

This study is a prospective, multi-cohort, multicenter, open-label exploratory clinical trial. The primary study objective is to evaluate the pathologic complete response (PCR) of treatment of HR+/HER2-low breast cancer with neoadjuvant therapy combined with Trastuzumab Rezetecan and Toripalimab , including the incidences and types of adverse events. The secondary endpoints include event-free survival (EFS), residual cancer burden (RCB), and objective response rate (ORR).

The goal of this clinical trial is to learn if add SHR-A1811 and/or Adebrelimab on standard chemotherapy could further improve the pCR rate in HR+/HER2 low early stage breast cancer patients. It will also learn about the safety of these combination regimen. The main questions it aims to answer are: Is Adebrelimab plus chemotherapy better than T-EC chemotherapy alone in neoadjuvant setting of HR+/HER2-low early stage population? Is SHR-A1811-EC plus Adebrelimab better than T-EC chemotherapy and/or Adebrelimab plus chemotherapy Participants will: Take 8 cycles of standard chemotherapy at day1, every 3 weeks cycle(standard care), or take 8 cycles of adebrelimab plus standard chemotherapy at day 1, every 3 weeks cycle(experimental 2), or take 4 cycles of SHR-A1811 and Adebrelimab at day 1, every 3 weeks cycle, then 4 cycles of adebrelimab plus EC chemotherapy at day 1, every 3 weeks cycke(experimental 1). Visit the clinic once every 6 weeks at neoadjuvant period for tumor assessment. Take surgery after completion of 8 cycles of neoadjuvant therapy and assess the pathological response. Then, visit the clinic once every 12 weeks at first year and then every 6 months for tumor assessment.

This is an open-label, phase II study evaluating the efficacy and safety of SHR-A1811 alone or in combination with Adebrelimab in Stage II-III HR Positive/HER2 Low Breast Cancer. Subjects will receive the neoadjuvant therapy of SHR-A1811 alone or in combination with Adebrelimab for six cycles, and then undergo surgery within 4 weeks after neoadjuvant therapy. Efficacy will be assessed every 2 cycles.