Unresectable or Metastatic Breast Cancer

The primary purpose of the study is to assess the safety, tolerability, and anti-tumor activity of HER3-DXd and T-DXd in the combination dosing regimens in participants with hormone receptor positive, HER2-low or HER2-ultralow, unresectable, or metastatic breast cancer.

This is a multicenter, open phase Ib/II clinical study, which is divided into two phases: dose exploration and efficacy expansion. Participants entering the study will receive HRS-8080 combined with Dalpiciclib Isethionate Tablets therapy.