Etacstil
Etacstil (developmental code names GW-5638, DPC974) is an orally active, nonsteroidal, combined selective estrogen receptor modulator (SERM) and selective estrogen receptor degrader (SERD) that was developed for the treatment of estrogen receptor-positive breast cancer.[1][2][3] It was shown to overcome antiestrogen (tamoxifen, aromatase inhibitor, fulvestrant) resistance in breast cancer by altering the shape of the estrogen receptor, thus exhibiting SERD properties.[11] Etacstil was developed in the early 1990s by Duke University, Glaxo Wellcome, and later, Dupont.[12][13] In 2001, Bristol Myers-Squibb (BMS) acquired Dupont, and for non-scientific, corporate reasons, closed the trial and abandoned the release of etacstil and its metabolite GW-7604.[6][9][12] After many dormant years, a recent resurgence of interest in SERDs has led to the development of brilanestrant, a structural analogue of etacstil.