Title: Epristeride
CAS Registry Number: 119169-78-7
CAS Name: (17b)-17-[[(1,1-Dimethylethyl)amino]carbonyl]androsta-3,5-diene-3-carboxylic acid
Additional Names: 17b-(N-tert-butylcarboxamido)androsta-3,5-diene-3-carboxylic acid
Manufacturers' Codes: SKF-105657
Molecular Formula: C25H37NO3
Molecular Weight: 399.57
Percent Composition: C 75.15%, H 9.33%, N 3.51%, O 12.01%
Literature References: 5a-Reductase inhibitor. Prepn and in vitro activity: D. A. Holt et al., EP 289327; eidem, US 4910226 and US 5017568 (1988, 1990, 1991 all to SmithKline Beecham); D. A. Holt et al., J. Med. Chem. 33, 943 (1990). Pharmacology: J. C. Lamb et al., Endocrinology 130, 685 (1992). Antitumor effects in rats: J. C. Lamb et al., Prostate 21, 15 (1992). Mechanism of action study: M. A. Levy et al., Biochemistry 29, 2815 (1990). HPLC determn in human plasma: V. K. Boppana et al., J. Chromatogr. 631, 251 (1993).
Properties: White crystals from ethyl acetate, mp 242-249°. pK 4.8.
Melting point: mp 242-249°
pKa: pK 4.8
Therap-Cat: Treatment of benign prostatic hypertrophy.
Keywords: Antiprostatic Hypertrophy; 5a-Reductase Inhibitor.
Eprosartan Eprozinol epsilon-Acetamidocaproic Acid epsilon-Aminocaproic Acid Epsiprantel

Systematic (IUPAC) name
17-(tert-butylcarbamoyl)androsta-3,5-diene-3-carboxylic acid
Clinical data
Legal status Non-regulated
Routes Oral
Pharmacokinetic data
Bioavailability 93%[1]
Half-life 26 hours[1]
CAS number 119169-78-7
ATC code None
PubChem CID 68741
ChemSpider 10625794
UNII 39517A04PS
Chemical data
Formula C25H37NO3 
Mol. mass 399.566 g/mol

Epristeride (SKF-105,657, ONO-9302) is a selective, transition state, non-competitive inhibitor of the type II isoform of the enzyme 5α-reductase,[2][3] similarly to finasteride and turosteride. It was under development for the treatment of benign prostatic hyperplasia and acne vulgaris by SmithKline Beecham (now GlaxoSmithKline), and reached phase III clinical trials in the United States, United Kingdom, and Japan,[2] but ultimately was never marketed.