Cytestrol acetate

Cytestrol acetate is a steroidal antiestrogen and a cytostatic antineoplastic agent (i.e., chemotherapeutic) which was developed for the treatment of breast cancer but was never marketed.^[1][2][3][4]

Cytestrol acetate

Clinical data
Other names	11α-Hydroxyethinylestradiol 3-(bis(2-chloroethyl)carbamate) 11α,17β-diacetate; 17α-Ethynylestra-1,3,5(10)-triene-3,11α,17β-triol 11α,17β-diacetate 3-(bis(2-chloroethyl)carbamate)
Identifiers
IUPAC name (1S,10S,11S,14R,15S,17R)-17-(Acetyloxy)-5-{[bis(2-chloroethyl)carbamoyl]oxy}-14-ethynyl-15-methyltetracyclo[8.7.0.02,7.011,15]heptadeca-2,4,6-trien-14-yl acetate
ChemSpider	58838619
Chemical and physical data
Formula	C29H35Cl2NO6
Molar mass	564.50 g·mol−1
3D model (JSmol)	Interactive image
SMILES [H][C@@]12CC[C@@](OC(C)=O)(C#C)[C@@]1(C)C[C@@H](OC(C)=O)[C@]1([H])C3=CC=C(OC(=O)N(CCCl)CCCl)C=C3CC[C@@]21[H]
InChI InChI=1S/C29H35Cl2NO6/c1-5-29(38-19(3)34)11-10-24-23-8-6-20-16-21(37-27(35)32(14-12-30)15-13-31)7-9-22(20)26(23)25(36-18(2)33)17-28(24,29)4/h1,7,9,16,23-26H,6,8,10-15,17H2,2-4H3/t23-,24-,25+,26+,28-,29-/m0/s1 Key:RRJRVDYYFLBGSE-UPRLNUCLSA-N

It is an 11α-hydroxylated derivative of ethinylestradiol in which a bis(2-chloroethyl)amine nitrogen mustard moiety has been attached as an ester at the C3 position and acetate esters have been attached at the C11α and C17β positions.^[1][2][3][4] The mechanism of action of cytestrol acetate in breast cancer is two-fold: (1) acting as an antiestrogen similarly to fulvestrant or ICI-164384; and (2) having cytostatic actions via the carbamate–nitrogen mustard moiety analogously to estramustine phosphate.^[1][2][3][4] The drug shows potent efficacy against breast cancer superior to that of tamoxifen in in vitro models.^[1][2][3]