In vivo metabolism and final disposition of a novel nonsteroidal androgen in rats and dogs

Minoli A. Perera, Donghua Yin, Di Wu, Kenneth K. Chan, Duane D. Miller, James Dalton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Compound S-4 (S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3- trifluoromethyl-phenyl)-propionamide) is a novel nonsteroidal androgen agonist that mimics many of the beneficial pharmacologic effects of testosterone with lesser effects on the prostate. S-4 demonstrated high androgen receptor binding affinity as well as anabolic specificity during in vivo pharmacologic studies in rats, identifying it as the first member of a new class of selective androgen receptor modulators. The purpose of these studies was to determine the pharmacokinetics and metabolism of S-4 in dogs. S-4 showed linear pharmacokinetics after both intravenous (i.v.) and oral (p.o.) administrations at pharmacologically relevant doses, with a mean clearance of 4.6 ml/min/kg and a mean half-life of about 200 min. It is interesting that dose-dependent oral bioavailability was seen. However, at pharmacologically relevant doses, the oral bioavailability of S-4 was 91%. Species differences were observed in S-4 metabolism; the major metabolic pathway for S-4 in dogs was deacetylation of the B-ring acetamide group and reduction of the A-ring nitro group, whereas the major metabolic pathway for S-4 in rats was hydrolysis on the amide bond and reduction of the A-ring nitro group. In addition, oxidative metabolites and phase II metabolites were identified in both rats and dogs. These studies demonstrate that S-4 maintains its promising pharmacokinetic properties in dogs (i.e., high oral bioavailability and linear kinetics) and is largely eliminated via hepatic metabolism by both phase I and phase II enzymes.

Original languageEnglish (US)
Pages (from-to)1713-1721
Number of pages9
JournalDrug Metabolism and Disposition
Issue number10
StatePublished - 2006

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science


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