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| Other names | Isotibolone; ORG-OM-38; Delta-4-Tibolone; 7α-Methylnorethisterone; 7α-Methyl-17α-ethynyl-19-nortestosterone; 17α-Ethynyl-17β-hydroxy-7α-methyl-4-estren-3-one |
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| Formula | C21H28O2 |
| Molar mass | 312.453 g·mol−1 |
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δ4-Tibolone (developmental codeORG-OM-38; also known asisotibolone,7α-methylnorethisterone, or7α-methyl-17α-ethynyl-19-nortestosterone) is asyntheticandrogen andprogestin which was never marketed.[1][2] The compound is a majoractive metabolite oftibolone, which itself is aprodrug of δ4-tibolone along with3α-hydroxytibolone and3β-hydroxytibolone (which, in contrast to δ4-tibolone, areestrogens).[1] Tibolone and δ4-tibolone are thought to be responsible for the androgenic and progestogenic activity of tibolone, while 3α-hydroxytibolone and 3β-hydroxytibolone are thought to be responsible for itsestrogenic activity.[1]
Isotibolone exhibited both estrogenic and progestogenic properties in several biological test systems and was found to be 10 to 40 times as potent as norethindrone in comparative assays. Tested for androgenic activity, it stimulated growth of seminal vesicles and the levator ani but was relatively inactive in stimulating prostate gland growth.[3]
