Alarelin

1 Identity

Synthetic GnRH nonapeptide analog containing a D-residue

Sequence

PGlu-His-Trp-Ser-Tyr-D-Ala-Leu-Arg-Pro-NHEt. A synthetic nonapeptide GnRH analog, [D-Ala6, des-Gly10]-LHRH ethylamide, normally supplied as the acetate salt. Three structural features carry the identity and each is a separate release attribute: the N-terminus is a cyclized pyroglutamate and not a free amine; position 6 is the D-enantiomer of alanine, a deliberate non-natural stereocenter; and the C-terminus is an N-ethylamide, which is a different functional group from both a free acid and a simple primary amide.

Molecular formula

C56H78N16O12 (free base); C56H78N16O12 . 2C2H4O2 = C60H86N16O16 (diacetate salt as supplied). The free-base formula also follows residue by residue from the sequence, independently of any supplier statement.

Average mass

1167.340 Da (C56H78N16O12, free base); 1287.444 Da (C60H86N16O16, diacetate salt).

Monoisotopic mass

1166.59851 Da free base; 1286.64077 Da diacetate. [M+H]+ 1167.6058 for the free base.

Salt / variant note

The densest confusable field in this set, because the entire GnRH analog class is A family of nonapeptide ethylamides differing only at position 6. Every formula below agrees with its published molecular weight. (1) Leuprolide, [D-Leu6], otherwise the identical construct: C59H84N16O12, 1209.42 average / 1208.6455 monoisotopic — exactly 42.08 Da heavier, and that number is the trap. A careless reading calls plus 42 an acetylation, but acetyl is C2H2O at 42.0106 Da and the Leu-for-Ala substitution is C3H6 at 42.0470 Da. The two differ by 0.0364 Da, about 30 ppm at this mass: an LC-HRMS method at plus or minus 5 ppm separates them without difficulty, a unit-resolution instrument cannot, and leuprolide is an approved product in wide circulation. (2) Deslorelin, [D-Trp6] ethylamide: C64H83N17O12, 1282.48 / 1281.6407. (3) Buserelin, [D-Ser(tBu)6] ethylamide: C60H86N16O13, 1239.45 / 1238.6560. (4) Fertirelin, the [Gly6] veterinary ethylamide: C55H76N16O12, 1153.31 / 1152.5829 — only 14.03 Da lighter, a single methylene, and sold into the same buyer population. (5) Native gonadorelin (LHRH), the decapeptide amide: C55H75N17O13, 1182.31 / 1181.5730, 14.97 Da heavier than alarelin and therefore within about one dalton of an alarelin tryptophan-oxidation product. (6) Triptorelin: C64H82N18O13, 1311.47 / 1310.6309. (7) terminal-chemistry substitutions on alarelin itself, all built from the confirmed structure: the C-terminal free acid, C54H73N15O13, 1140.27 / 1139.5512, 27.07 Da lighter; the simple primary amide, C54H74N16O12, 1139.29 / 1138.5672, 28.05 Da lighter — a supplier who makes the ordinary amide instead of the ethylamide lands here. (8) degradation species that must be on the related-substances table: tryptophan oxidation, C56H78N16O13, 1183.34 / 1182.5934, plus 16.00 — note this sits 1.03 Da from gonadorelin at 1182.31, so a nominal-mass certificate reading 1182 or 1183 cannot say whether it is looking at an oxidized lot or at the wrong peptide entirely; and the ring-opened glutamyl form from hydrolysis of the pyroglutamate, C56H80N16O13, 1185.36 / 1184.6091, plus 18.02. (9) the substitution no mass resolves: epimerization at position 6 converts the article into the all-L nonapeptide, which is isobaric to every decimal place and co-elutes on any achiral column. (10) salt form against itself: free base 1167.34 against diacetate 1287.44 is a 10.3 percent weight difference for the same number of molecules, and both forms circulate under the one name. (11) A note on the class that mass will never settle: lecirelin, the veterinary [D-Tle6] analog, is isomeric with leuprolide rather than merely isobaric, so even exact mass cannot separate those two from each other.

2 Class & testing panel

Form

Single article

Testing panel

P3 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Predominantly veterinary reproductive-physiology literature — cattle, swine, rabbits and farmed fish — published largely in Chinese and Eastern European journals, together with scattered Chinese clinical reports. There is no FDA-reviewed human dataset, no marketing authorization in the United States for human or animal use, and no United States Pharmacopeia monograph. Much of the accessible literature is not indexed in English-language databases, which the citation index page states directly, because an evidence library whose gaps are invisible is not a library. No specific PMID or trial registration is asserted, because none is in the file, and this catalog does not manufacture references.

4 Storage & specification

Storage

Supplied as the acetate salt, lyophilized, in a Type I amber glass vial under nitrogen, stoppered, crimped and placed in a secondary opaque carton. Labeled: store at -20 degrees C plus or minus 5 degrees C, protect from light strictly, protect from moisture, equilibrate the sealed vial to room temperature before opening. The light protection is specific rather than boilerplate — tryptophan at position 3 is both photolabile and oxidation-labile, and the secondary carton exists for that residue. Retained reference samples are held at -80 degrees C. Ships with gel packs at 2-8 degrees C and a single-use temperature logger in every carton.

Shelf life

Provisional 12 months at -20 degrees C plus or minus 5 degrees C protected from light, stated as provisional pending the company's own data, with tryptophan oxidation products, the ring-opened glutamyl impurity and total related substances as the stability-indicating attributes, plus a single ICH Q1B photostability study run once on the first released lot to justify the packaging rather than assert it. Extension only on real-time data at 12, 18 and 24 months.