17β-Methyl-17α-dihydroequilenin
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]
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| 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 |
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| Formula | C19H22O2 |
| Molar mass | 282.383 g·mol−1 |
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References
- 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.
- 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.