An orally available, selective estrogen receptor degrader (SERD) and selective estrogen receptor modulator (SERM), with potential antineoplastic and estrogen-like activities. Upon oral administration of higher doses of RAD1901, this agent acts as a SERD, which binds to the estrogen receptor (ER) and induces a conformational change that results in the degradation of the receptor. This may inhibit the growth and survival of ER-expressing cancer cells. At lower doses of this agent, RAD1901 acts as a SERM and has estrogen-like effects in certain tissues, which can both reduce hot flashes and protect against bone loss. In addition, RAD1901 is able to cross the blood-brain barrier (BBB).