18-Methylsegesterone acetate

18-Methylsegesterone acetate
Clinical data
Synonyms 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
PubChem CID
Chemical and physical data
Formula C24H32O4
Molar mass 384.516 g/mol
3D model (JSmol)

18-Methylsegesterone acetate (18-methyl-SGA; also known as 18-methylnestorone) is a progestin medication of the 19-norprogesterone group which was never marketed.[1][2][3] It was first described in a patent in 1997 and then in a literature paper in 2003.[4][1] 18-Methyl-SGA is the C18 methyl or C13β ethyl derivative of segesterone acetate (SGA; 16-methylene-17α-acetoxy-19-norprogesterone), and shows 3 to 10 times the progestogenic potency of SGA in bioassays.[1] This is analogous to the case of the 19-nortestosterone progestin norethisterone and its 18-methyl derivative levonorgestrel, 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 of progesterone 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 highly selective progestogen.[1][5] Like SGA, 18-methyl-SGA shows negligible affinity for the androgen receptor.[1][3] While 18-methyl-SGA has not been assessed at the other steroid hormone receptors, it is expected to be highly selective for the progesterone receptor similarly to SGA.[1] 18-Methyl-SGA shows over 16 times the affinity of progesterone for the progesterone receptor expressed in rat uterus.[1] In terms of oral bioavailability, 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 from sustained release systems.[1] As such, 18-methyl-SGA should be ideally suited for use via routes of administration like subcutaneous implants and transdermal patches.[1]

Comparison of potencies of selected progestogens[1]
ProgestogenPR RBA
(rat uterus)
18-Methyl-SGA355%0.3 µg0.03 mg
Segesterone acetate107%1 µg0.3 mg
Levonorgestrel100%3 µg0.3 mg
Progesterone22%100 µg1.0 mg
a = Minimum effective dose.

See also


  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Tuba Z, Bardin CW, Dancsi A, Francsics-Czinege E, Molnár C, Csörgei J, Falkay G, Koide SS, Kumar N, Sundaram K, Dukát-Abrók V, Balogh G (May 2000). "Synthesis and biological activity of a new progestogen, 16-methylene-17alpha-hydroxy-18-methyl-19-norpregn-4-ene-3, 20-dione acetate". Steroids. 65 (5): 266–74. doi:10.1016/S0039-128X(99)00109-9. PMID 10751638.
  2. 1 2 Sitruk-Ware R, Small M, Kumar N, Tsong YY, Sundaram K, Jackanicz T (November 2003). "Nestorone: clinical applications for contraception and HRT". Steroids. 68 (10-13): 907–13. doi:10.1016/S0039-128X(03)00140-5. PMID 14667982.
  3. 1 2 Kumar N, Fagart J, Liere P, Mitchell SJ, Knibb AR, Petit-Topin I, Rame M, El-Etr M, Schumacher M, Lambert JJ, Rafestin-Oblin ME, Sitruk-Ware R (January 2017). "Nestorone® as a Novel Progestin for Nonoral Contraception: Structure-Activity Relationships and Brain Metabolism Studies". Endocrinology. 158 (1): 170–182. doi:10.1210/en.2016-1426. PMC 5412978. PMID 27824503.
  4. 18-methyl 16-methylene 19-nor pregnane derivatives as progestins, pharmaceutical compositions containing them and process for the preparation thereof. https://patents.google.com/patent/WO1997023498A1/en
  5. 1 2 Kumar N, Koide SS, Tsong Y, Sundaram K (2000). "Nestorone: a progestin with a unique pharmacological profile". Steroids. 65 (10-11): 629–36. doi:10.1016/S0039-128X(00)00119-7. PMID 11108869.

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