Human GnRH receptor knock-in mice (testosterone reduction) and castrated monkeys (LH decrease)
“In vivo, administration of relugolix suppressed the pituitary-gonadal axis, causing a decrease in plasma luteinizing hormone in castrated monkeys after a single dose and reduction of serum testosterone levels in human GnRH receptor knock-in male mice after repeat dosing.”
✓ VerifiedFDA multi-discipline review, p. 32Source ↗
Why that model
~19,000-24,000x lower binding affinity for rat GnRH receptor than monkey/human
“In contrast, a 19,000x and 24,000x reduction in binding affinity was noted to rat GnRH receptor (IC50 = 2900 nM) compared to monkey and human receptors, respectively.”
✓ VerifiedFDA multi-discipline review, p. 32Source ↗
Reviewer's view of the efficacy data
EMA: knock-in mouse studies did not address LH and FSH decreases
“Unexpectedly, two of the primary effects of antagonism of the GnRH receptor, i.e. decreases in LH and FSH, were not addressed in these studies.”