ESR1 and neoplasm: Indeed, PF-9363, a potent and selective acetyl-CoA competitive inhibitor against KAT6A/B1, exhibits robust anti-tumor activity in estrogen receptor-positive (ER+) breast cancer models, including tumors resistant to endocrine therapy (6), and structurally related inhibitor shows clinical efficacy in a Phase 1 trial in advanced or metastatic solid tumors (10).