RecruitingDrug trialStudy of ECI830 Single Agent or in Combination in Patients With Advanced HR+/HER2- Breast Cancer and Other Advanced Solid TumorsPhase I: Characterize safety and tolerability of ECI830 as a single agent and in combination with ribociclib and fulvestrant. Identify dose range for optimization/recommended dose for future studies. Phase II: Assess the anti-tumor activity of ECI830 in combination with ribociclib and fulvestrant in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer.