Study of AMXT 1501 and DFMO in Combination With Standard Therapies in Advanced Solid Tumors

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.