Gonadotropins regulate the development of ovarian follicles and stimulate the production of sperm, making them essential for reproduction. They are used therapeutically for assisted reproduction in humans and to induce ovulation and superovulation in various mammals. The potency of gonadotropins is required to be evaluated accurately to ensure there is consistency between batches to allow for subsequent reproducible treatments. These assays are typically performed in immature rats and may be influenced by the strain selected in addition to numerous environmental conditions.
The basis for hormone potency assays is typically a parallel line analysis in which the biological activity of the given hormone is estimated by comparing its effect on reproductive organs. The relative potency of the unknown test sample is determined by comparison to a qualified reference standard material. Rats are assigned to a minimum of 3 dose groups per test sample/reference standard and are injected typically via subcutaneous route of administration on multiple occasions with graded concentrations of each preparation. The readout for the assay is typically ovarian or seminal vesicle weight depending on the hormone being evaluated.
While regulatory guidelines including the European Pharmacopoeia describe basic potency assays to estimate the biological activity of each hormone, the bioassay typically requires optimization for different preparations. Charles River Ireland offers method development, reference standard qualification, comparability studies for biosimilars, validation, and batch release testing for a range of hormones. Method development services include but are not limited to dose response/range finder studies to determine the linear range of the assay and to select geometrically progressing doses to be used in the routine test. Validation of modified methods (e.g., single injection rather than the classical multiple injection FSH protocol of Steelman & Pohley) to ICH or VICH guidelines (depending on whether the product is for medicinal or veterinary purposes) may be performed to demonstrate that the assay is specific, accurate, precise, and robust in addition to evaluation of the stability-indicating properties of the assay.
Table 1 below outlines some of the in vivo hormone potency assays that are routinely carried out at our site in Ireland for recombinant and extracted preparations.
|Follicle Stimulating Hormone (FSH)||Luteinizing Hormone (LH)||Human Chorionic Gonadotropin (hCG)||Pregnant Mare Serum Gonadotropin / Equine Chorionic Gonadotropin (PMSG/eCG)|
|Biological Effect||Controls follicular maturation in the ovary and stimulates the development of spermatozoa||Regulates synthesis of androgens in males and triggers ovulation and development of the corpus luteum in females||Produced during pregnancy by the placenta||Dual FSH/LH activity|
|Uses||Treats infertility in women who cannot ovulate. It is often used with hCG||Stimulates ovulation and treats infertility in women and stimulates sperm production in men||Stimulates ovulation and treats infertility in women and increases sperm count in men||Often used with progestogen prior to artificial insemination to induce ovulation in livestock|
|Potency Assay Target Organ||Ovaries||Seminal vesicles||Seminal vesicles||Ovaries|
|Injections (No. & Times)||3 in total @ 2, 4 & 48 hours||4 in total @ 0, 24, 48 & 72 hours||4 in total @ 0, 24, 48 & 72 hours||6 in total @ 0, 18, 21, 24, 42 & 48 hours|
|Duration of Test||3 days||4 days||5 days||5 days|