Imlunestrant

Imlunestrant is a selective estrogen receptor degrader (SERD).{|Sherman2025|} It induces degradation of wild-type ERα and ERα containing an activating tyrosine-to-serine mutation at residue 537 (ERα^Y537S) when used at a concentration of 100 nM. Imlunestrant reduces growth of ER⁺ T47D and MCF-7 breast cancer cells (IC₅₀s = 0.34 and 5.2 nM, respectively) but not MDA-MB-231 triple-negative breast cancer cells. It also reduces growth of ERα^Y537S -expressing T47D and MCF-7 cells (IC₅₀s = 113 and 512 nM, respectively). Imlunestrant (15 mg/kg per day) induces tumor regression in an ERβ-independent, ERα-^Y537S -mutant-harboring liver metastasis patient-derived xenograft (PDX) model. Formulations containing imlunestrant have been used in the treatment of breast cancer.

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