HP-568

Phase I primary objective: To evaluate the safety and tolerability of HP568 in patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ER+/HER2-advanced breast cancer) and determine the recommended dose RP2D for Phase II. Phase I secondary objectives: (1) To evaluate the pharmacokinetic (PK) characteristics of HP568 in patients with ER+/HER2-advanced breast cancer. (2) To evaluate the preliminary efficacy of HP568 in the treatment of patients with ER+/HER2-advanced breast cancer. Phase I exploratory objectives: (1) To explore potential predictors of efficacy. (2) To identify the metabolites of HP568. Phase II primary objective: To evaluate the clinical benefit rate (CBR) of HP568 in patients with ER+/HER2-advanced breast cancer after 24 weeks of treatment. Phase II secondary objectives: (1) To evaluate the efficacy of HP568 in patients with ER+/HER2-advanced breast cancer. (2) To evaluate the safety of HP568 in patients with ER+/HER2-advanced breast cancer. (3) Evaluate the pharmacokinetic (PK) characteristics of HP568 in patients with ER+/HER2- advanced breast cancer. Phase II exploratory objective: To explore potential predictors of efficacy.