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| Other names | BR-906; 11β,17β-Dihydroxy-17α-methyl-3-oxoandrosta-1,4-diene-2-carboxylic acid |
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| Chemical and physical data | |
| Formula | C21H28O5 |
| Molar mass | 360.450 g·mol−1 |
| 3D model (JSmol) | |
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Roxibolone (INN; development code BR-906; also known as 11β,17β-dihydroxy-17α-methyl-3-oxoandrosta-1,4-diene-2-carboxylic acid) is a steroidal antiglucocorticoid described as an anticholesterolemic (cholesterol-lowering) and anabolic drug which was never marketed.[1][2] Roxibolone is closely related to formebolone, which shows antiglucocorticoid activity similarly and, with the exception of having a carboxaldehyde group at the C2 position instead of a carboxylic acid group, roxibolone is structurally almost identical to.[2] The 2-decyl ester of roxibolone, decylroxibolone (development code BR-917), is a long-acting prodrug of roxibolone with similar activity.[1][2]
In rats, roxibolone counteracts the catabolic effects (control of nitrogen balance) and increased alkaline phosphatase levels induced by the potent glucocorticoid dexamethasone phosphate.[2] It does not bind to the glucocorticoid receptor however, and its antiglucocorticoid activity may instead be mediated by enzyme inhibition.[3] In accordance, 11α- and 11β-hydroxyprogesterone are known to be potent inhibitors of 11β-hydroxysteroid dehydrogenase (11β-HSD), which is responsible for the biosynthesis of the potent endogenous glucocorticoids cortisol and corticosterone (from the precursors deoxycortisol and deoxycorticosterone, respectively).[4][5] As roxibolone is 11β-hydroxylated similarly, it may act in a likewise fashion. However, formebolone was found to be a very weak inhibitor of 11β-HSD type 2, although this specific isoenzyme is responsible for the inactivation of glucocorticoids rather than their production.[6]
Unlike formebolone, which is additionally an anabolic-androgenic steroid (AAS), roxibolone is devoid of affinity for the androgen receptor and possesses no androgenic or myotrophic activity in animal assays.[2] For this reason, it has been said that roxibolone may be much better tolerated in comparison.[2]
