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Clinical data
Other namesZK-136295; Cycloestriol; 14α,17α-Ethanoestriol; 14α,17α-Ethanoestra-1,3,5(10)-triene-3,16α,17β-triol; 14,21-Cyclo-19-norpregna-1,3,5(10)-triene-3,16α,17α-triol
Routes of
By mouth[1]
Drug classEstrogen
Pharmacokinetic data
Elimination half-life12.3 hours[1]
  • (8R,9S,13S,14S,16R,17R)-13-Methyl-7,8,9,11,12,13,15,16-octahydro-14,17-ethanocyclopenta[a]phenanthrene-3,16,17(6H)-triol
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass314.425 g·mol−1
3D model (JSmol)
  • C[C@]12CC[C@H]3[C@H]([C@@]14CC[C@@]2([C@@H](C4)O)O)CCC5=C3C=CC(=C5)O
  • InChI=1S/C20H26O3/c1-18-7-6-15-14-4-3-13(21)10-12(14)2-5-16(15)19(18)8-9-20(18,23)17(22)11-19/h3-4,10,15-17,21-23H,2,5-9,11H2,1H3/t15-,16-,17-,18+,19+,20+/m1/s1

Cyclotriol (developmental code name ZK-136295; also known as 14α,17α-ethanoestriol) is a synthetic estrogen which was studied in the 1990s and was never marketed.[2][1][3][4] It is a derivative of estriol with a bridge between the C14α and C17α positions.[2][1][3][5] The drug has 40% of the relative binding affinity of estradiol for the human ERα.[2] It showed an absolute bioavailability of 40% with high interindividual variability and an elimination half-life of 12.3 hours in pharmacokinetic studies in women.[1]

See also[edit]


  1. ^ a b c d e f Baumann A, Fuhrmeister A, Brudny-Klöppel M, Draeger C, Bunte T, Kuhnz W (October 1996). "Comparative pharmacokinetics of two new steroidal estrogens and ethinylestradiol in postmenopausal women". Contraception. 54 (4): 235–42. doi:10.1016/S0010-7824(96)00194-1. PMID 8922877.
  2. ^ a b c Michael Oettel; Ekkehard Schillinger (6 December 2012). Estrogens and Antiestrogens II: Pharmacology and Clinical Application of Estrogens and Antiestrogen. Springer Science & Business Media. pp. 10, 15, 76, 331–332. ISBN 978-3-642-60107-1.
  3. ^ a b Lang, Rainer; Reimann, Roland (1993). "Studies for a genotoxic potential of some endogenous and exogenous sex steroids. I. Communication: Examination for the induction of gene mutations using the ames salmonella/microsome test and the HGPRT test in V79 cells". Environmental and Molecular Mutagenesis. 21 (3): 272–304. doi:10.1002/em.2850210311. ISSN 0893-6692. PMID 8462531. S2CID 39049586.
  4. ^ Reimann R, Kalweit S, Lang R (1996). "Studies for a genotoxic potential of some endogenous and exogenous sex steroids. II. Communication: examination for the induction of cytogenetic damage using the chromosomal aberration assay on human lymphocytes in vitro and the mouse bone marrow micronucleus test in vivo". Environ. Mol. Mutagen. 28 (2): 133–44. doi:10.1002/(SICI)1098-2280(1996)28:2<133::AID-EM10>3.0.CO;2-G. PMID 8844995. S2CID 10326219.
  5. ^ Hundal BS, Dhillon VS, Sidhu IS (March 1997). "Genotoxic potential of estrogens". Mutat. Res. 389 (2–3): 173–81. doi:10.1016/S1383-5718(96)00144-1. PMID 9093381.