Alarelin

Alarelin is a synthetic GnRH agonist analog, structurally related to native Gonadorelin and to other GnRH agonist analogs profiled on this site (Triptorelin, and others built elsewhere in this catalog). Alarelin's specific modifications are a D-alanine substitution at position 6 (replacing native GnRH's glycine) and a des-glycine-10 ethylamide C-terminal modification, in which the native C-terminal glycinamide is replaced by direct ethylamide attachment to proline-9. Together, these modifications confer enhanced GnRH receptor binding affinity and resistance to enzymatic degradation, extending duration of action similarly to (though via a chemically distinct substitution pattern from) Triptorelin's D-tryptophan-6 modification.

At Verified Peptides, we want to directly flag a naming-vigilance point relevant to this entire GnRH-analog family: Alarelin's D-Ala6 substitution should not be confused with Leuprolide's D-Leu6 substitution or Triptorelin's/Deslorelin's D-Trp6 substitution — three chemically distinct single-amino-acid modifications at the same sequence position, each defining a separate, distinctly named compound, despite all sharing the same general 'GnRH agonist' mechanism and near-identical backbone.

We also want to be transparent about a vendor data inconsistency we identified during this research process: multiple chemical suppliers list different CAS numbers for material described as 'Alarelin acetate' (we found 79561-22-1, 148029-26-9, and 52435-06-0 all used across different vendor listings), which likely reflects different salt, hydrate, or purity-grade forms being labeled inconsistently rather than a single settled registration — we are using CAS 79561-22-1, the most consistently cross-referenced number across independent chemical databases, while flagging this inconsistency directly rather than presenting false certainty. Chemically, Alarelin's free base peptide has molecular formula C56H78N16O12, molecular weight approximately 1167.3 g/mol (independently derived atom-by-atom from the known amino acid sequence); the commonly sold diacetate salt form has formula C60H86N16O16, molecular weight approximately 1287.4 g/mol. We want to note directly that we found at least one vendor source pairing the free-base molecular weight (1167.3) with the diacetate salt's molecular formula (C60H86N16O16) — an internally inconsistent pairing, since these two figures correspond to different forms of the compound, and a discrepancy our independent atom-by-atom derivation allowed us to catch and correct.

To derive the free-base formula, we summed the constituent free amino acid formulas for the nine residues (glutamic acid, histidine, tryptophan, serine, tyrosine, D-alanine, leucine, arginine, and proline), subtracted eight water molecules for the eight peptide-bond condensations joining them into a linear chain, then applied two further modifications: intramolecular cyclization of the N-terminal glutamate into pyroglutamate (removing one additional water molecule), and replacement of the C-terminal carboxylic acid with an ethylamide group (net addition of one nitrogen, two carbons, and five hydrogens, with removal of one oxygen and one hydrogen from the original hydroxyl group). This derivation produced C56H78N16O12, and adding two acetic acid equivalents (accounting for the commercially standard diacetate salt form) reproduced C60H86N16O16 exactly, matching the formula reported by several independent vendor sources for 'Alarelin acetate.'

At Verified Peptides, we think Alarelin sits at a distinctly different evidence tier than Triptorelin, despite both being real, regulatory-approved GnRH agonist analogs: Alarelin's approval and predominant use is specific to China, and its independently published literature, while real, is comparatively smaller in volume and skews toward Chinese-language clinical journals and animal/veterinary research rather than the large multinational Phase III trial literature supporting Triptorelin's FDA approval.

The most directly relevant human clinical citation we identified is Duan et al. (2010, Zhonghua Nan Ke Xue, PMID 20873594), a real study from the Center of Reproductive Medicine at the 181st Hospital of the People's Liberation Army in Guilin, China, comparing Alarelin (78 patients) against Triptorelin (44 patients) in the long-protocol ovulation induction approach for IVF-embryo transfer in 122 women aged 24-39 with secondary infertility. The study found no significant differences between groups in gonadotropin dose/duration, oocyte counts, embryo quality, fertilization, implantation, clinical pregnancy, or early miscarriage rates, though the cycle cancellation rate was significantly higher in the Triptorelin group. We want to note this was a real comparative clinical study, though we could not confirm from available English-language summaries whether it was randomized or a non-randomized comparative cohort, a methodological detail relevant to how confidently its findings should be weighted. We also identified additional real, peer-reviewed Alarelin research in animal and veterinary contexts, including a pharmacokinetic study using triple-stage mass spectrometry fragmentation in rat plasma, a study on Alarelin active immunization effects on ovarian receptor expression in ewes, and a study on sustained-release Alarelin delivery via PLGA microparticles for inducing spermiation in sterlet, a sturgeon species — genuine published research, though these preclinical and veterinary/aquaculture studies do not by themselves establish human clinical efficacy or safety.

We also want to directly flag a real, recent safety-relevant finding: Alarelin acetate-induced hepatotoxicity has been documented in a peer-reviewed case report and literature review (2025, Frontiers in Medicine, PMID 41090118), a genuine adverse-event signal worth noting for researchers, distinct from the more general and well-characterized bone-density and flare-related safety considerations shared across the entire GnRH agonist drug class. No FDA or EMA approval exists for Alarelin in Western markets; it is an approved drug specifically in China. At Verified Peptides, we sell research-grade Alarelin exclusively for laboratory research.

Alarelin was originally developed by Ma'anshan Fengyuan Pharmaceutical Co., a Chinese pharmaceutical manufacturer, illustrating a broader pattern in the GnRH agonist drug class: while the foundational GnRH structure and initial agonist analogs (Triptorelin, Leuprolide) emerged largely from Western and Japanese pharmaceutical research in the 1970s-1980s, subsequent GnRH agonist analogs have continued to be independently developed by pharmaceutical companies in other countries, including China, each with their own specific substitution chemistry and their own region-specific regulatory approval and clinical evidence base.

The three-way naming distinction between Alarelin (D-Ala6), Leuprolide (D-Leu6), and Triptorelin/Deslorelin (D-Trp6) reflects a broader structure-activity exploration pattern common across GnRH agonist analog development: researchers systematically tested different D-amino acid substitutions at the same sequence position (position 6, immediately following the receptor-recognition-critical Tyr5 residue) to identify which substitution provided the best combination of receptor affinity, metabolic stability, and manufacturability, with several different substitutions ultimately proving commercially viable rather than a single winner emerging.

The reported hepatotoxicity case (PMID 41090118) specifically examined pharmacogenomic factors, suggesting individual genetic variation in drug metabolism may influence risk for this adverse effect — a research direction relevant to personalized-medicine approaches for GnRH agonist therapy broadly, not necessarily unique to Alarelin's specific chemistry.

China's pharmaceutical regulatory pathway for domestically developed drugs like Alarelin operates under the National Medical Products Administration (NMPA), a separate regulatory body from the FDA or EMA with its own approval standards and evidentiary requirements — a distinction relevant to interpreting what 'approved' means for compounds like Alarelin that are legitimately regulatory-approved in one major jurisdiction but have not undergone or received approval through the separate regulatory pathways used in the United States or European Union.

At Verified Peptides, we require independent third-party HPLC purity testing and mass spectrometry identity confirmation for every batch of research-grade Alarelin we offer, with a Certificate of Analysis (COA) available for each lot. Given the vendor CAS-number and formula inconsistencies we identified during this research process, researchers should independently confirm the exact molecular formula and salt form represented by any specific lot's COA rather than assuming consistency across different suppliers' documentation.

We source exclusively from manufacturers operating under Good Manufacturing Practice (GMP)-aligned quality systems, and every lot is independently verified rather than accepted solely on a supplier's internal documentation. Researchers should always request and review the specific COA for the lot they receive, confirming purity percentage and molecular identity before use in any experimental protocol, and specifically noting whether the material is the free base or diacetate salt form.

Lyophilized Alarelin is stable when stored at -20°C, protected from light and moisture. At Verified Peptides, we ship lyophilized peptide with appropriate cold-chain packaging to preserve stability in transit.

Once reconstituted, solution should be stored refrigerated at 2–8°C and used within the timeframe indicated on the product's documentation, avoiding repeated freeze-thaw cycles, consistent with standard handling practices for the other GnRH agonist peptides in this catalog.