Etacstil

Etacstil, known as, GW-5638 is a discontinued selective estrogen receptor modulator drug that was developed by Glaxo Wellcome, and later, GlaxoSmithKline for the treatment of hormone receptor-positive breast cancer.^{[1] [2][3]} GW-5638 was shown to overcome tamoxifene-resistance in breast cancer by altering the shape of the estrogen receptor, thus exhibiting selective estrogen receptor degrader properties.^{[4] [5] [6] [7] [8]}