What it is
Ganirelix is a ten-amino-acid peptide drug built from GnRH (gonadotropin-releasing hormone), the brain hormone that tells the pituitary gland to release the reproductive hormones LH and FSH. Native GnRH is the molecule this library records as gonadorelin. The ganirelix label lists the changes:
- amino acids replaced at six of the ten positions — 1, 2, 3, 6, 8 and 10;
- several of the replacements are mirror-image (D) amino acids and non-standard ones — a naphthylalanine, a chlorinated phenylalanine, a pyridylalanine and two diethylated homoarginines;
- an acetyl cap at the start and an amide at the end.
The result weighs 1,570.4 and does the opposite of the hormone it was built from.
How it works
GnRH normally arrives at the pituitary in pulses — LH pulses run at about one an hour in the mid and late follicular phase, the label notes — and a large mid-cycle burst produces the LH surge that triggers ovulation. Ganirelix sits in the GnRH receptor and blocks it. Per the label:
- suppression of LH and FSH is rapid and reversible, and stronger for LH than FSH;
- no initial release of gonadotropins was detected, "consistent with an antagonist effect";
- LH and FSH were fully recovered within 48 hours of stopping.
That missing first surge is the practical difference from the GnRH agonists in this library — leuprolide, triptorelin and goserelin — which switch the system on hard before it shuts down.
| Measure (label, healthy women, 250 mcg) | Single dose | Daily for 7 days |
|---|---|---|
| Time to peak | 1.1 h | 1.1 h |
| Half-life | 12.8 h | 16.2 h |
| Peak level | 14.8 ng/mL | 11.2 ng/mL |
| Absolute bioavailability | 91.1% | — |
What the trials showed
The label rests on two controlled trials in women undergoing stimulation for IVF:
| Trial | Design | Result on the label |
|---|---|---|
| Dose-finding (332 women) | Double-blind, randomised, six doses from 62.5 to 2,000 mcg a day | 250 mcg gave the highest vital-pregnancy rate: 35.7% per attempt (25 of 70), against 6.7% to 25.8% at the other doses. LH rises of 10 mIU/mL or more fell from 4 of 31 at the lowest dose to 0 at 500 mcg and above |
| Reference-controlled (463 women) | Open-label, randomised, against a luteal-phase GnRH agonist | Mean 5.4 days of treatment; 440 egg retrievals, 399 transfers; ongoing pregnancy 20.3% per attempt, 23.3% per transfer |
The dose-finding table is unusual: pregnancy rates fell at doses above 250 mcg, alongside lower oestradiol — more suppression was not better.
Safety
Across the label's controlled trials (794 women), events at 1% or more included gynaecological abdominal pain (4.8%), fetal death (3.7%), headache (3.0%), ovarian hyperstimulation syndrome (2.4%), vaginal bleeding (1.8%) and injection-site reaction (1.1%), counted without regard to cause. Rare allergic reactions, including anaphylaxis, have been reported after marketing, sometimes with the first dose. An observational study of more than 1,000 newborns found congenital-anomaly rates comparable with a GnRH-agonist cycle; the label states a causal link is unknown.
Where it stands
Drugs@FDA lists seven applications on 2026-10-02:
| Application | Holder | Type | Approved |
|---|---|---|---|
| NDA 021057 | Organon | Original | 1999-07-29 |
| ANDA 204246 — Fyremadel | Sun Pharma | Generic | 2018-11-30 |
| ANDA 212613 | Amphastar | Generic | 2022-04-07 |
| ANDA 214996 | Meitheal | Generic | 2022-06-06 |
| ANDA 215658 | Gland | Generic | 2023-02-28 |
| ANDA 216075 | Lupin | Generic | 2023-11-16 |
| ANDA 218855 | Qilu | Generic | 2025-04-23 |
PubMed returns 306 records for ganirelix, 76 tagged as randomised controlled trials (2026-10-02). It is given as a 250 mcg prefilled syringe under a fertility specialist's direction; the timing within a cycle is set by the treating clinic.
Related reading
Ganirelix is one of several GnRH-based molecules in this library: the native hormone gonadorelin, the agonists leuprolide and triptorelin, and the implant goserelin. The hormone given at the end of stimulation in the label's trials was hCG, and kisspeptin sits one step upstream of GnRH.