HER2-low Hormone Receptor Positive Breast Cancer

This study will evaluate the safety, tolerability, and preliminary effectiveness of AMXT 1501 and DFMO when combined with standard treatments for advanced solid tumors. The trial includes two groups: * Cohort 1: Patients with ER+ / HER2- breast cancer receiving fulvestrant and capivasertib * Cohort 2: Patients with unresectable or metastatic cutaneous melanoma receiving pembrolizumab The Phase 1b portion will find the recommended Phase 2 dose (RP2D). The Phase 2 portion will further evaluate clinical activity at the RP2D using response criteria for solid tumors (RECIST 1.1). The study will also evaluate pharmacokinetics, pharmacodynamics, disease control, and overall safety.

This is a Phase II Study of HLX22 in Combination with Trastuzumab Deruxtecan (T-DXd) in HER2-low, Hormone Receptor Positive Locally Advanced or Metastatic Breast Cancer Patients with Disease Progression or Intolerable Adverse Reaction on Standard of Care. Eligible subjects will be treated with the study drug until the loss of clinical benefit, death, intolerable toxicity, withdrawal of informed consent, or other reasons specified by the protocol (whichever occurs first).