A selective androgen receptor modulator for hormonal male contraception

J Pharmacol Exp Ther. 2005 Feb;312(2):546-53. doi: 10.1124/jpet.104.075424. Epub 2004 Sep 3.


The recent discovery of nonsteroidal selective androgen receptor modulators (SARMs) provides a promising alternative for testosterone replacement therapies, including hormonal male contraception. The identification of an orally bioavailable SARM with the ability to mimic the central and peripheral androgenic and anabolic effects of testosterone would represent an important step toward the "male pill". We characterized the in vitro and in vivo pharmacologic activity of (S)-3-(4-chloro-3-fluorophenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethylphenyl)propionamide (C-6), a novel SARM developed in our laboratories. C-6 was identified as an androgen receptor (AR) agonist with high AR binding affinity (K(i) = 4.9 nM). C-6 showed tissue-selective pharmacologic activity with higher anabolic activity than androgenic activity in male rats. The doses required to maintain the weight of the prostate, seminal vesicles, and levator ani muscle to half the size of the maximum effects (i.e., ED(50)) were 0.78 +/- 0.06, 0.88 +/- 0.1, and 0.17 +/- 0.04 mg/day, respectively. As opposed to other SARMs, gonadotropin levels in C-6-treated groups were significantly lower than control values. C-6 also significantly decreased serum testosterone concentration in intact rats after 2 weeks of treatment. Marked suppression of spermatogenesis was observed after 10 weeks of treatment with C-6 in intact male rats. Pharmacokinetic studies of C-6 in male rats revealed that C-6 was well absorbed after oral administration (bioavailability 76%), with a long (6.3 h) half-life at a dose of 10 mg/kg. These studies show that C-6 mimicked the in vivo pharmacologic and endocrine effects of testosterone while maintaining the oral bioavailability and tissue-selective actions of nonsteroidal SARMs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Androgen Receptor Antagonists
  • Androgens
  • Aniline Compounds / pharmacology*
  • Animals
  • Area Under Curve
  • Chromatography, High Pressure Liquid
  • Contraceptive Agents, Male / pharmacokinetics
  • Contraceptive Agents, Male / pharmacology*
  • Epididymis / drug effects
  • Epididymis / growth & development
  • Follicle Stimulating Hormone / blood
  • Isomerism
  • Luteinizing Hormone / blood
  • Male
  • Orchiectomy
  • Organ Size / drug effects
  • Phenyl Ethers / pharmacology*
  • Prostate / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Androgen / drug effects*
  • Reproduction / drug effects
  • Seminal Vesicles / drug effects
  • Seminal Vesicles / growth & development
  • Testis / drug effects
  • Testis / growth & development


  • 3-(4-chloro-3-fluorophenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethylphenyl)propionamide
  • Androgen Receptor Antagonists
  • Androgens
  • Aniline Compounds
  • Contraceptive Agents, Male
  • Phenyl Ethers
  • Receptors, Androgen
  • Luteinizing Hormone
  • Follicle Stimulating Hormone