In recent clinical trials of metastatic ER+ BC, next-generation SERDs demonstrated clinical activity, and elacestrant received an approval for advanced ESR1-mutant disease. NR tumors instead up-regulate multiple ERα-independent proliferative pathways, such as EGFR/MAPK and Hippo/TEAD, which may represent targetable dependencies in NR disease. Modeling resistance and lineage plasticity in vitro, we find that giredestrant-resistant ER+ BC cell lines exhibit profound shifts in chromatin accessibility, with the transcription factors, FOXA1 and FOXM1, implicated in gene expression of NR-upregulated proliferative pathways.
These findings may facilitate the development of traditional medicinebased therapeutic strategies and provide insights for potential lead optimization in breast cancer drug discovery.