GDC-0152-acetamide is a pan-antagonist of apoptosis inhibiting proteins (IAPs). It induces the autoubiquitination and subsequent degradation of cIAP1/2, activates the non-canonical NF-κB pathway, and promotes the secretion of TNF-α, leading to apoptosis in tumor cells. GDC-0152-acetamide holds potential for research in ERα-positive breast cancer.