Triptorelin

1 Identity

Synthetic decapeptide of the GnRH/LHRH structural family, supplied as a salt. Ten residues, no cysteine, no disulfide, no acylation, no metal. Three structural features the residue count hides and the panel is built around: a non-proteinogenic N-terminal pyroglutamate; a single D-residue, D-tryptophan at position 6, set against L-tryptophan at position 3, so one molecule carries both enantiomers of the same amino acid; and a C-terminal glycinamide in place of a free acid. Supplied as the acetate, the trifluoroacetate or the pamoate (embonate) salt, and the counterion is part of the article rather than a packaging detail.

Sequence

PGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2. One-letter with lower case marking the D-residue: <Glu>-H-W-S-Y-w-L-R-P-G-NH2. Ten residues, no disulfide. Position 1 is 5-oxo-L-proline (pyroglutamate), a cyclized non-proteinogenic N-terminus with no free alpha-amino group, so Edman degradation returns nothing without prior pyroglutamate aminopeptidase treatment and a certificate reporting a blocked N-terminus is reporting the expected result. Position 6 is D-Trp against L-Trp at position 3. Position 10 is glycinamide, not glycine acid. The salt must be named on the record and on the label — acetate, trifluoroacetate or pamoate — because the counterion changes solubility, the assay basis and net peptide content materially, and because the approved depot products use the pamoate.

Molecular formula

C64H82N18O13 (free base). Salt forms carried as separate formula units and not folded into the identity: mono-acetate C66H86N18O15; mono-trifluoroacetate C66H83F3N18O15; pamoate (embonate) C64H82N18O13 . C23H16O6, written as the formula unit C87H98N18O19. The formula is identical for the L-Trp6 epimer and for every other stereoisomer, which is exactly why it is not an identity statement on its own.

Average mass

Average mass 1311.473 Da (C64H82N18O13, free base), computed from the formula and independently reconstructed residue-by-residue from pGlu-His-Trp-Ser-Tyr-Trp-Leu-Arg-Pro-Gly with a C-terminal amide; the two routes return C64H82N18O13 and the same number. Salt forms: mono-acetate 1371.525; mono-trifluoroacetate 1425.495; pamoate formula unit 1699.848, against the 1699.9 printed on the Trelstar labeling, and the pamoate arithmetic closes because free base 1311.473 plus pamoic acid 388.375 equals 1699.848. The free base is 77.2% of the pamoate by mass and 95.6% of the acetate; a labeled milligram figure that does not say which basis it uses is out by up to 23%.

Monoisotopic mass

1310.63087 Da neutral (C64H82N18O13). Working ions: [M+H]+ m/z 1311.63815, [M+2H]2+ m/z 656.32271, [M+3H]3+ m/z 437.88423. A plus or minus 5 ppm window on the neutral is plus or minus 0.0066 Da. Des-amido free acid (Gly10-OH) C64H81N17O14, 1312.457 average / 1311.61489 monoisotopic, exactly plus 0.98402 Da. Mono-trifluoroacetate 1424.62374; mono-acetate 1370.65200; pamoate formula unit 1698.72556. The multiply charged states are given because a 1.3 kDa peptide is normally measured at 2+ or 3+, where the 0.98 Da des-amido gap becomes 0.49 and 0.33 m/z and is easily lost in an unresolved isotope envelope.

Salt / variant note

Salt form is the dominant commercial variable and it is not cosmetic. Free base C64H82N18O13, 1311.473 / 1310.63087. Mono-acetate 1371.525, the form commonly shipped as "triptorelin acetate". Mono-trifluoroacetate 1425.495, a form research suppliers ship. Pamoate (embonate) formula unit C87H98N18O19, 1699.848 / 1698.72556, the form used in the approved depot products. One supplier lists the pamoate at 100 mg and an acetate at 50 mg — two articles both invoiced as "triptorelin", and the only thing that separates them on the invoice is the counterion. Des-amido free acid (Gly10-OH), C64H81N17O14, 1312.457 / 1311.61489, exactly plus 0.98402 Da: the characteristic defect of an amide-terminating synthesis, partially co-eluting, and a substantially different article. The GnRH-analogue family, which shares the pGlu-His-Trp-Ser-Tyr N-terminus and differs only at position 6 and the C-terminus, so the whole set elutes in one window on a generic reversed-phase gradient and is separated in practice by mass alone. All computed from formula on the 2021 table: deslorelin C64H83N17O12, 1282.475 / 1281.64071 — the most dangerous of the set, because it carries the same D-Trp6 and differs only by des-Gly10 and an ethylamide, a gap of 28.998 Da; nafarelin C66H83N17O13, 1322.496 / 1321.63563, 11.02 Da away; histrelin C66H86N18O12, 1323.528 / 1322.66726, 12.06 Da from triptorelin and 1.03 Da from nafarelin; goserelin C59H84N18O14, 1269.433 / 1268.64144; buserelin C60H86N16O13, 1239.447 / 1238.65603; leuprolide C59H84N16O12, 1209.421 / 1208.64546; gonadorelin C55H75N17O13, 1182.311 / 1181.57303, exactly 129.16 Da lighter, which is Trp minus Gly. And the one no mass detects: L-Trp6 triptorelin, the C6 epimer — identical formula, identical average mass, identical monoisotopic mass, co-eluting on achiral reversed phase, and the direct product of using the cheaper L-Trp building block at position 6. Degradants with their own numbers: tryptophan mono-oxidation plus 15.995 at either Trp, di-oxidation plus 31.990, kynurenine-type plus 3.995; tyrosine oxidation plus 15.995; deamidation at the C-terminal amide is the des-amido species above.

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.

Literature exists and is recorded by kind, with no statement of any effect. There is approved-product labeling in the United States for two products whose active moiety this is — Trelstar (NDA 020715, with the later NDA 022437) and Triptodur (NDA 208956) — and behind that labeling sits a large registrational and post-marketing clinical literature under those product names, spanning randomized controlled trials, long-term extension studies and pharmacokinetic studies of depot formulations. None of it is restated here, no outcome is quoted, and no indication, population or route is named. The volume of published work is recorded as a fact about the field and is presented on the research page as counts by study type with identifiers, not as claims. Separately and as a channel screen rather than a scientific statement: triptorelin is named on the WADA Prohibited List at S2, peptide hormones, growth factors and related substances, which makes it an adverse signal for content and advertising decisions on any platform that applies anti-doping policy.

4 Storage & specification

Storage

White to off-white lyophilized powder in amber glass or foil-overwrapped vials with a nitrogen headspace and in-pack desiccant, minus 20 degrees C plus or minus 5 degrees C, desiccated, protected from light. Light protection is A specification input on this molecule and not housekeeping: both tryptophan residues photo-oxidize, the oxidation species carry numeric release limits, and a clear vial on a bench under fluorescent light is a stability excursion that no thermometer records. Sampling under yellow light with cumulative light exposure captured on the sampling record. Shipped frozen with a validated shipper and a temperature logger, and the logger record is filed against the order number. Vials equilibrated to room temperature sealed before opening.

Shelf life

Provisional retest interval 24 months at minus 20 degrees C plus or minus 5 degrees C in the sealed original container protected from light, pending this company's own ICH Q1A-format study on three production lots, with an ICH Q1B photostability arm because the identified labile centers are the two tryptophan indoles. The two stability-indicating attributes are tryptophan oxidation and des-amido growth, and the decision rule is written in advance: if either exceeds half its release limit at the month-12 point, the interval drops to 12 months and the lot is re-tested annually thereafter. An area-percent purity figure alone does not date this molecule, because the des-amido species partially co-elutes. Chiral purity at position 6 is trended on stability and not only at release.