Cetrorelix

Cetrorelix (SB-75) is a competitive gonadotropin-releasing hormone receptor (GnRHR) antagonist with a K_d of 0.19 nM. Cetrorelix inhibits the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), thereby suppressing the secretion of downstream sex steroids. Cetrorelix prevents ovulation, induces reversible reproductive shutdown and azoospermia, reduces ovarian fibrosis, improves superovulation outcomes, and inhibits chemotherapy-induced mitochondria-dependent apoptosis. Cetrorelix is applicable for fertility assistance research^[1][2][3]. In Vitro:Cetrorelix induces minimal histamine release from rat mast cells, with an ED₅₀ far above pharmacologically relevant plasma concentrations^[3].
Cetrorelix does not inhibit EGF-stimulated proliferation of human granulosa cells at pharmacologically relevant concentrations, with inhibitory effects only seen at ~100-fold higher concentrations^[3]. In Vivo:Cetrorelix (5 μg/day; i.p.; daily; 20 days total) pretreatment inhibits alkylating antineoplastic agent-induced ovarian granulosa cell apoptosis via suppression of mitochondria-dependent apoptotic pathways, and restoring normal serum estradiol levels and mitochondrial function^[1].
Cetrorelix (5 μg/day; i.p.; daily; 20 days) alone has no detectable effect on ovarian granulosa cell apoptosis, hormone levels, or mitochondrial function in healthy female Sprague-Dawley rats^[1].
Cetrorelix (5 µg/kg; i.p.; once every 3 days or daily; 1 week) significantly increases the number of normal superovulated oocytes in aged female C57BL/6J mice (to 9.8 and 8.7 oocytes, respectively), reduces ovarian fibrosis, and maintains normal oocyte fertilization and fetal development rates^[2].
Cetrorelix (~10 μg/kg; s.c.; single dose) immediately suppresses plasma LH by >80% in male castrated rats, with full recovery within 24 hours^[3].
Cetrorelix (250-1250 μg/kg; s.c.; single dose) immediately suppresses LH in male castrated cynomolgus monkeys, with suppression lasting for at least 96 hours^[3].