17β-Methyl-17α-dihydroequilenin

17β-Methyl-17α-dihydroequilenin

Clinical data
Other names	NCI-122; 17β-Methyl-6,8-didehydro-17α-estradiol; 17β-Methylestra-1,3,5(10),6,8-pentaene-3,17α-diol
Drug class	Estrogen
Identifiers
IUPAC name (13S,14S,17R)-13,17-dimethyl-12,14,15,16-tetrahydro-11H-cyclopenta[a]phenanthrene-3,17-diol
CAS Number	1011733-40-6^Y
PubChem CID	9549180
ChemSpider	7828102
UNII	ZP488KVU9Q
CompTox Dashboard (EPA)	DTXSID201336494
Chemical and physical data
Formula	C19H22O2
Molar mass	282.383 g·mol^−1
3D model (JSmol)	Interactive image
SMILES C[C@]12CCC3=C([C@@H]1CC[C@@]2(C)O)C=CC4=C3C=CC(=C4)O
InChI InChI=1S/C19H22O2/c1-18-9-7-15-14-6-4-13(20)11-12(14)3-5-16(15)17(18)8-10-19(18,2)21/h3-6,11,17,20-21H,7-10H2,1-2H3/t17-,18-,19+/m0/s1 Key:FQMQOMRDADWGJJ-GBESFXJTSA-N

17β-Methyl-17α-dihydroequilenin (developmental code name NCI-122), also known as 17β-methyl-6,8-didehydro-17α-estradiol, is a synthetic steroidal estrogen which was never marketed.^[1][2] It is the C17β methylated derivative of 17α-dihydroequilenin, an equine estrogen and constituent of conjugated estrogens (Premarin).^[1][2] 17α-Dihydroequilenin itself is an analogue of 17α-estradiol, the C17 epimer of estradiol (or 17β-estradiol).^[1][2] NCI-122 has respective relative binding affinities of about 8.1% and 16% for the ERα and ERβ when compared to estradiol.^[2] It is far less potent as an estrogen in comparison to estradiol, with relative estrogenic potencies at the ERα and ERβ of 1.4% and 0.81%, respectively.^[1] Nonetheless, NCI-122 acts as a full agonist of the ERα (ERβ was not assessed) and has estrogenic activity similar to that of estradiol at sufficiently high concentrations.^[2] The mechanisms of the lower potency of NCI-122 and related estrogens (e.g., 17α-estradiol and equilenin) relative to estradiol have been studied.^[1]

References

1. Hsieh RW, Rajan SS, Sharma SK, Greene GL (January 2008). "Molecular characterization of a B-ring unsaturated estrogen: implications for conjugated equine estrogen components of premarin". Steroids. 73 (1): 59–68. doi:10.1016/j.steroids.2007.08.014. PMC 2225582. PMID 17949766.
2. Flores VA, Taylor HS (September 2015). "The Effect of Menopausal Hormone Therapies on Breast Cancer: Avoiding the Risk". Endocrinol. Metab. Clin. North Am. 44 (3): 587–602. doi:10.1016/j.ecl.2015.05.007. PMC 4555991. PMID 26316245.