Study of IEV407 as Single Agent or in Combination in Patients With Advanced HR+/HER2- Breast Cancer

This is a first-in-human, open-label, phase I/Ib, multi-center study consisting of a dose escalation part of IEV407 as a single agent (SA) and in combination with endocrine therapy (fulvestrant or letrozole) followed by a dose expansion part in patients with advanced breast cancer (aBC). The study will start with the evaluation of IEV407 as a SA. Following evaluation of IEV407 in combination with fulvestrant through dose escalation and establishment of a recommended dose and/or dose ranges for optimization (RD/DRO), the study may proceed to the Phase Ib expansion part to evaluate the combination treatment of IEV407 with fulvestrant. If more than one treatment arm is open concurrently in the dose expansion part, a randomization schedule will be employed for patient allocation.