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| Clinical data | |
|---|---|
| Other names | 18-Methyl-SGA; 13β-Ethyl-SGA; 18-Methylnestorone; 18-Methyl-NES; 13β-Ethylnestorone; 13β-Ethyl-NES; 18-Methylelcometrine; 16-Methylene-17α-acetoxy-18-methyl-19-norprogesterone; 16-Methylene-17α-hydroxy-18-methyl-19-norpregn-4-ene-3,20-dione acetate |
| Drug class | Progestin;Progestogen;Progestogen ester |
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| CAS Number | |
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| Chemical and physical data | |
| Formula | C24H32O4 |
| Molar mass | 384.516 g·mol−1 |
| 3D model (JSmol) | |
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18-Methylsegesterone acetate (18-methyl-SGA; also known as18-methylnestorone) is aprogestin medication of the19-norprogesterone group which was never marketed.[1][2][3] It was first described in apatent in 1997 and then in a literature paper in 2003.[4][1] 18-Methyl-SGA is the C18methyl or C13βethylderivative ofsegesterone acetate (SGA; 16-methylene-17α-acetoxy-19-norprogesterone), and shows 3 to 10 times theprogestogenicpotency of SGA inbioassays.[1] This is analogous to the case of the19-nortestosterone progestinnorethisterone and its 18-methyl derivativelevonorgestrel, the latter showing substantially increased potency relative to the former similarly.[1] As SGA is already one of the most potent progestins to have been developed, with 100-fold the potency ofprogesterone and 10-fold the potency of levonorgestrel in bioassays, 18-methyl-SGA is an extremely potent progestogen, among if not the most potent known.[2][5][1]
SGA is a highlyselective progestogen.[1][5] Like SGA, 18-methyl-SGA shows negligibleaffinity for theandrogen receptor.[1][3] While 18-methyl-SGA has not been assessed at the othersteroid hormone receptors, it is expected to be highly selective for the progesterone receptor similarly to SGA.[1] 18-Methyl-SGA shows over 16 times theaffinity of progesterone for theprogesterone receptor expressed in ratuterus.[1] In terms oforalbioavailability, it is known that SGA is not active orally, while the oral activity of 18-methyl-SGA is unknown.[1] The addition of an 18-methyl group to SGA is unlikely to affect its rate of delivery fromsustained release systems.[1] As such, 18-methyl-SGA should be ideally suited for use viaroutes of administration likesubcutaneous implants andtransdermal patches.[1]
| Progestogen | PRTooltip Progesterone receptorRBATooltip Relative binding affinity (ratuterus) | Clauberg assaya | Pregnancy maintenance |
|---|---|---|---|
| 18-Methyl-SGA | 355% | 0.3 μg | 0.03 mg |
| Segesterone acetate | 107% | 1 μg | 0.3 mg |
| Levonorgestrel | 100% | 3 μg | 0.3 mg |
| Progesterone | 22% | 100 μg | 1.0 mg |
| Footnotes:a = Minimum effective dose.Sources:[1] | |||
