Choriogonadotropin alpha is produced by recombinant DNA techniques. It shares the amino acid sequence with urinary hCG. Chorionic gonadotropin binds on the ovarian theca (and granulosa) cells to a transmembrane receptor shared with the luteinising hormone, the LH/CG receptor.
The principal pharmacodynamic activity in women is oocyte meiosis resumption, follicular rupture (ovulation), corpus luteum formation and production of progesterone and estradiol by the corpus luteum.
In women, chorionic gonadotropin acts as a surrogate luteinising hormone surge that triggers ovulation.
Choriogonadotropin alpha is used to trigger final follicular maturation and early luteinisation after use of medicinal products for stimulation of follicular growth.
In comparative clinical trials, administration of a dose of 250 micrograms of choriogonadotropin alpha was as effective as 5,000 IU and 10,000 IU of urinary hCG in inducing final follicular maturation and early luteinisation in assisted reproductive techniques, and as effective as 5,000 IU of urinary hCG in ovulation induction.
So far, there are no signs of antibody development in humans to choriogonadotropin alpha. Repeated exposure to choriogonadotropin alpha was investigated in male patients only. Clinical investigation in women for the indication of ART and anovulation was limited to one treatment cycle.
Following intravenous administration, choriogonadotropin alfa is distributed to the extracellular fluid space with a distribution half-life of around 4.5 hours. The steady-state volume of distribution and the total clearance are 6 l and 0.2 L/h, respectively. There are no indications that choriogonadotropin alfa is metabolised and excreted differently than endogenous hCG.
Following subcutaneous administration, choriogonadotropin alfa is eliminated from the body with a terminal half-life of about 30 hours, and the absolute bioavailability is about 40%.
A comparative study between the freeze-dried and the liquid formulation showed bioequivalence between the two formulations.
Nonclinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity and genotoxicity. Studies on carcinogenic potential were not performed. This is justified, given the proteinous nature of the active substance and the negative outcome of the genotoxicity testing.
Studies on reproduction were not performed in animals.
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