[GnRH antagonists: present and future]

Antagonists act by competitive inhibition of pituitary GnRH receptors for which they have a high affinity with a dose-dependent activity. The inhibition concerns LH but also FSH by inhibiting their secretion for 24 hours. At this time, only three molecules are available. Cetrorelix is mainly used for in vitro fertilization protocols, but research is currently being carried out in benign prostatic hypertrophy. Ganirelix is only used in medically assisted procreation. Abarelix is used in the United States as a monthly "depot" injection for the treatment of prostate cancer resistant to other therapies. Other molecules including orally active antagonists are in the course of clinical evaluation or in preclinical phases. The development of this therapeutic class is hampered by conflicting industrial interests and also by problems of tolerability in particular because of the side effects due to induced histamine release. The current indications in France are therefore limited to Assisted Reproductive Technology, and, recently, prostate cancer pending comparative studies versus agonists. The indications under development are endometriosis, myoma and precocious puberty, fields in which agonists have already been found to be effective. Male contraception seems to have a future however this therapeutic regimen remains very expensive. Finally, in benign prostatic hypertrophy, the antagonists administrated intermittently may be used to rapidly improve urinary flow.