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 ethylderivative of segesterone acetate (SGA; 16-methylene-17α-acetoxy-19-norprogesterone), and shows 3 to 10 times the progestogenicpotency 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]
^ abcdefghijklmTuba 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. PMID10751638. S2CID37188669.
^ abSitruk-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. PMID14667982. S2CID34984413.