Alarelin Acetate
Also known as: Alarelin, Avorelin, Alarelin GnRH agonist, Alarelin acetate injection
Synthetic GnRH agonist (gonadotropin-releasing hormone analogue / LHRH agonist)
What it is
Alarelin acetate is used by women in fertility clinics — mainly in China — to prevent premature egg release during IVF cycles. It works by first briefly spiking, then completely shutting down, the brain's hormonal signal to the ovaries. China has approved it for this use, but the US FDA has not; its status in Canada and under anti-doping rules is unconfirmed.
The scientific side
Alarelin acetate is a synthetic decapeptide analogue of endogenous gonadotropin-releasing hormone (GnRH). Like native GnRH, it binds to GnRH receptors (GnRHR) on pituitary gonadotroph cells. However, because native GnRH is released in discrete pulses, sustained administration of alarelin delivers continuous, non-pulsatile receptor stimulation. This paradoxically causes receptor downregulation and pituitary desensitization: after an initial brief surge in luteinizing hormone (LH) and follicle-stimulating hormone (FSH), gonadotropin secretion falls to castrate levels. In ovarian granulosa cells and follicular tissue, alarelin modulates FSHR and LHR protein expression and influences follicular development, as demonstrated in ewe models (PMID 23607296). Beyond the reproductive axis, GnRH receptors are expressed in gastric parietal cells; alarelin inhibits gastric acid secretion and stimulates IP3 second-messenger signalling in these cells (PMIDs 15670615, 19174006). In smooth muscle cell cultures, alarelin exerts dose-dependent antiproliferative effects via G1 cell-cycle arrest (PMID 15188505). In zebrafish, GnRH3 (a homologue of human GnRH) acting through an alarelin-responsive ERK1/2-MAPK pathway regulates primordial germ cell proliferation and sex differentiation (PMID 31758175). The peptide also suppresses angiogenic VEGF expression in endometriotic implants in rat models (PMID 16909610), supporting a role in managing hormone-sensitive tissue growth. Pharmacokinetic characterisation in rats after 13.5 µg/kg intramuscular administration yielded a plasma linear range of 0.3–10 ng/mL, establishing the basis for clinical dose selection (PMID 31257725).
Class: Synthetic GnRH agonist (gonadotropin-releasing hormone analogue / LHRH agonist)
Administration & storage
- Administration
- Subcutaneous injection (human clinical trial: 150 µg/day; ewe studies: 200–400 µg)Intramuscular injection (ewe estrous synchronisation: 7.5 µg; rat pharmacokinetics: 13.5 µg/kg)Intranasal administration (referenced in fertility medicine context as alternative route; not specifically dosed in reviewed abstracts)Sustained-release PLGA microparticle injection (fish aquaculture research: 35–200 µg/kg)
- Storage
- Storage conditions were not described in the reviewed abstracts. Standard practice for peptide GnRH analogues: refrigerate at 2–8°C; protect from light; do not freeze reconstituted solution; use within manufacturer-specified window after reconstitution.
- Cautions
- Drug-induced liver injury (DILI): One case of acute hepatocellular injury (RUCAM score 6 = highly probable) in a 37-year-old woman receiving 150 µg/day SC; resolved within 18 days after discontinuation (PMID 41090118),Pharmacogenomic risk: NUDT15 *3/*3 diplotype and HLA risk alleles HLA-DRB1*15:01 and HLA-DQB1*06:01 were identified in the DILI case — individuals with these variants may be at elevated risk (PMID 41090118),Endometrial receptivity: GnRHa+PMSG superovulation protocols in mice reduced endometrial ER, PR, and LIF mRNA expression compared to natural cycles, raising theoretical concern about implantation success (PMID 18546535),Initial flare effect: As a GnRH agonist, alarelin will cause a transient initial surge in LH/FSH before pituitary desensitisation; this is pharmacologically expected and managed in clinical fertility protocols,Hypoestrogenic symptoms: Sustained pituitary suppression produces oestrogen deficiency symptoms (hot flushes, bone mineral density loss with prolonged use) consistent with the GnRH agonist class effect
Legal & regulatory status
Not approved. Alarelin acetate does not hold FDA approval for any indication in the United States. It has been used as an internal standard in US pharmacokinetic analytical studies (PMIDs 25038408, 19726244) but has no…
Not stated in reviewed literature — requires manual verification
Not stated in reviewed literature — requires manual verification
What it's studied for
- Controlled ovarian stimulation / pituitary downregulation for IVF-ET Human observational
- Ovulation triggering and estrous synchronisation Animal studies only
- Endometriosis treatment (pituitary suppression / medical pseudomenopause) Animal studies only
- Hormone-sensitive malignancy (investigational) Mechanistic only
- Gastric acid secretion modulation (preclinical / mechanistic) Mechanistic only
- Antiproliferative effects on smooth muscle and gastric cells (preclinical) Mechanistic only
Safety signals
- Drug-induced liver injury (DILI) / acute hepatocellular injury
- Pharmacogenomic susceptibility — HLA alleles and NUDT15 variants
- Reduced endometrial receptivity markers with GnRHa-containing superovulation protocols
- Class-effect hypoestrogenic symptoms (GnRH agonist flare, then suppression)
Contraindications
About these dose ranges
Dose ranges below reflect commonly reported community protocols. Where published research cites a specific dose, the PMID is linked. Doses without citations are not clinical recommendations — they reflect what practitioners and researchers commonly report using.
Community-reported dosing
| Route | Dose | Frequency / Duration | Population / context | Source tier |
|---|---|---|---|---|
| Subcutaneous injection | 150 µg/day | — | Study | Research |
| Subcutaneous injection | 200–400 µg (two or four doses total) | — | Study | Research |
| Intramuscular injection | 7.5 µg IM (single injection) | — | Study | Research |
| PLGA microparticle sustained-release injection | 35 µg/kg or 200 µg/kg body weight | — | Study | Research |
| Intramuscular injection | 13.5 µg/kg | — | Study | Research |
| In vitro (cell culture) | 10⁻⁹ to 10⁻⁵ mol/L | — | Study | Research |
| In vitro (cell culture) | 0.001–1 µmol/L | — | Study | Research |
| subcutaneous or intranasal | Dose not specified in reviewed abstracts; 150 µg/day SC documented in phase I trial (PMID 41090118); IVF comparison study (PMID 20873594) does not report the specific alarelin dose used | Daily subcutaneous injection during downregulation phase (typical long-protocol fertility clinic use) | women undergoing controlled ovarian stimulation in IVF long-protocol cycles |