Treatment of Dalpiciclib Combined With Pyrotinib for Trastuzumab-sensitive HER2+ Advanced Breast Cancer(DAP-Her-02)

Cyclin D-CDK4/6-RB-E2F signaling pathway regulates the transformation of breast cancer cells from stage G1 to S, and plays an important role in the proliferation of breast cancer cells. HER2 protein regulates proliferation of breast cancer cells through PI3K/AKT signaling pathway. HER2 positive breast cancer patients need anti HER2 therapy. Data indicate that HER2 positive breast cancer patients often express cyclin D1 and E1, suggesting that anti HER2 therapy can synergy with CDK4/6 inhibitors. A preclinical study shows that the combination of CDK4/6 inhibitor Dulcie and anti HER2 drug pyrrolidone can effectively reduce the phosphorylation of AKT and HER3, thereby promoting the apoptosis of HER2 positive breast cancer cells and achieving the purpose of inhibiting tumor. In the clinical study of na-phere 2, piperacillin combined with trastuzumab, patuzumab and fluvestrant can significantly inhibit the expression of Ki67. MonarcHER study shows that the treatment of patients with advanced HR+HER2+ breast cancer after the failure of anti HER2+ is better than conventional chemotherapy plus anti HER2 therapy. The successful challenge of traditional chemotherapy is the opening of a new chapter in the treatment of HR+/HER2+. In 2021, ESMO 276P reported the interim data of darcilil combined with pyrroltinib in the first-line / second-line treatment of MBC. HR -, HER2 + MBC ORR can reach 81.8%, and the safety is controllable. Based on different HR status, we explored the efficacy and safety of Pyrotinib and Dalpiciclib Isethionate Tablets based combination regimen in the first-line treatment of HER2 + MBC.