Context: Two new low-molecular-weight LH agonists (Org 43553 and Org 43902) were shown to induce ovulation in preclinical experiments.
Objective: Our objective was to assess the safety, pharmacokinetics, and pharmacodynamics of Org 43553 and Org 43902 when administered to healthy females.
Design and setting: Org 43553 and 43902 studies were randomized, placebo-controlled, single-rising-dose first-in-human trials, which included 159 healthy female volunteers. Part 1 of the studies assessed the safety and pharmacokinetics. Part 2 evaluated the pharmacodynamics effect of a single oral dose of Org 43553 (25-900 mg) or Org 43902 (30-300 mg) to induce ovulation after the development of a large preovulatory follicle, whereas the endogenous LH surge was suppressed due to GnRH antagonist treatment while follicular development was supported with recombinant FSH.
Results: Org 43553 and 43902 were safe and well tolerated. Both compounds showed a fast absorption after oral intake, with peak concentrations reached within 0.5 to 1 hour. The elimination half-life of Org 43553 was 30 to 47 hours and that of Org 43902 was 17 to 22 hours. Ovulation induction confirmed by midluteal progesterone rise ≥15 nmol/L was proven in both studies, also when excluding subjects with an endogenous LH rise. The minimal effective dose for ovulation induction was 300 mg in both studies and resulted in an ovulation rate of 83% and 82%, respectively.
Conclusions: These first proof-of-concept studies both demonstrated that a single oral intake of an low-molecular-weight LH agonist induces ovulation of the preovulatory follicle in pituitary-suppressed female volunteers of reproductive age.