Dalpiciclib, Anti-HER2 Therapy, and Endocrine Therapy for Hormone-Receptor-Positive, HER2-Positive Metastatic Breast Cancer

Evaluating the Efficacy and Safety of Dalpiciclib Plus Anti-HER2 Therapy and Endocrine Therapy in Patients With Induction-Treated Hormone-Receptor-Positive, HER2-Positive Metastatic Breast Cancer

Efficacy and Safety of Dalpiciclib Combined with Anti-HER2 Targeted Therapy and Endocrine Therapy as First-line Maintenance Treatment for Patients with Recurrent or Metastatic Hormone-Receptor-Positive, HER2-positive Breast Cancer.

This is a multicenter, single-arm, open-label, phase II clinical trial evaluating the efficacy and safety of dalpiciclib (a novel oral CDK4/6 inhibitor) combined with anti-HER2 therapy and endocrine therapy as maintenance treatment in patients with hormone receptor-positive (HR+)/HER2-positive metastatic breast cancer who have completed induction systemic therapy without disease progression.

Triple-positive (HR+/HER2+) metastatic breast cancer represents a unique subtype requiring dual pathway inhibition. Current standard first-line induction therapy includes taxane-based chemotherapy combined with trastuzumab and pertuzumab (THP) or pyrotinib (THPy), followed by maintenance with anti-HER2 therapy plus endocrine therapy. However, approximately 50% of patients progress within 18 months during maintenance therapy.

This study explores the addition of dalpiciclib to standard anti-HER2 and endocrine maintenance therapy to prolong progression-free survival. Dalpiciclib, the first domestically developed CDK4/6 inhibitor in China, has demonstrated favorable efficacy and a manageable safety profile in HR+/HER2- advanced breast cancer, with a lower incidence of febrile neutropenia and no observed interstitial lung disease.

Inclusion Criteria:

1. Females aged 18 to 75 years with pathologically confirmed metastatic or locally advanced unresectable breast cancer.
2. Hormone receptor (HR)-positive and HER2-positive.
3. Patients with no evidence of disease progression (including CR, PR, or SD)after 4-8 cycles of first-line systemic anti-tumor therapy.
4. ECOG Performance Status: 0-1.

Exclusion Criteria:

1. Symptomatic active brain metastases or extensive leptomeningeal metastases.
2. History of Grade 3 or 4 allergic reaction related to the study drugs.
3. Currently receiving other anti-tumor therapies.