Camizestrant (AZD9833) is a selective ER degrader and pure antagonist. A, Chemical structure of camizestrant. B, The indicated cell lines were treated with 100 nmol/L of the indicated compound for 48 hours. Levels of ERα were assessed by Western blotting and normalized to an untreated control and fulvestrant. Each point represents an independent experiment. C, MCF7 or CAMA-1 cells were treated with DMSO, 1 nmol/L estradiol, or 100 nmol/L of the indicated compound + 1 nmol/L estradiol for 24 hours. RNA expression was assessed by RNA sequencing. Data represent z-scores of normalized gene expression for genes in an ER activity signature. D, MCF7 and CAMA-1 cells were treated with the indicated concentration of the indicated compound for 7 days. Cell number was estimated with a Sytox Green assay normalized to an untreated control on the day of treatment (0.0) and an untreated control on day 7 after treatment (1.0). Data points represent the mean from three independent experiments performed in triplicate ± SD. E, Ishikawa cells were treated with the indicated concentration of fulvestrant or camizestrant, or 100 nmol/L AZD9496 for 24 hours, and ERα and PgR expressions were determined by Western blot. DMSO, dimethyl sulfoxide; PR, progesterone receptor.