Dose-related suppression of serum luteinizing hormone in women by a potent new gonadotropin-releasing hormone antagonist (Ganirelix) administered by intranasal spray

Abstract

To determine if the GnRH antagonist (GnRH-a) Ganirelix (Syntex Research, Palo Alto, CA), administered by intranasal (IN) spray to normal women, is absorbed into the systemic circulation and suppresses LH secretion. A single center, open label, nonrandomized, dose-escalation study. Academic research environment. Normal female volunteers ages 23 to 43 years. Ganirelix was administered as a single dose by IN spray. The administered doses and the number of women receiving each of them were 0.1 mg (n = 1), 0.3 mg (n = 1), 1 mg (n = 2), 3 mg (n = 5), and 6 mg (n = 5). Blood samples were collected from -15 minutes to 24 hours after dosing. Serum concentrations of Ganirelix and LH. Ganirelix was absorbed rapidly. The mean time to maximal serum levels in the 3- and 6-mg groups was 0.67 and 0.53 hour, respectively. Mean serum LH levels were suppressed by > or = 35% relative to baseline from 2 to 12 hours after dosing in both groups. The mean maximal percent decrease in serum LH was -62% (at 8 hours after dosing) and -74% (at 6 hours after dosing) in the 3- and 6-mg groups, respectively. Single dose IN administration of 3 or 6 mg of Ganirelix suppressed serum LH levels in women, further enhancing the potential clinical utility of this potent GnRH-a. This is the first clinical report of a GnRH-a reducing the secretion of a pituitary gonadotropin when administered by an IN delivery system. Based on the duration and extent of LH suppression observed in this study, Ganirelix, administered by twice daily IN spray, may be effective for the treatment of gonadal hormone-dependent disorders in women.