Ipamorelin

1 Identity

A synthetic C-terminally amidated pentapeptide. Three of its five positions are outside the proteinogenic set: one achiral non-proteinogenic residue and two D-residues. The ordering name is written Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) to preserve the non-proteinogenic positions on the face of the order. It is distinct from GHRP-2 (pralmorelin), GHRP-6 and hexarelin, each of which is a separate record with a separate mass.

Sequence

Aib-His-D-2-Nal-D-Phe-Lys-NH2; in full, 2-aminoisobutyryl-L-histidyl-D-3-(2-naphthyl)alanyl-D-phenylalanyl-L-lysinamide. Position by position: residue 1 is Aib (2-aminoisobutyric acid), which is non-proteinogenic and achiral and therefore carries no chiral limit but must be shown present by MS/MS; residue 2 is L-histidine; residue 3 is D-3-(2-naphthyl)alanine; residue 4 is D-phenylalanine; residue 5 is L-lysine. The N-terminus is a free alpha-amine on the achiral Aib residue; the C-terminus is a primary carboxamide, not a free acid. There is no cysteine and no disulfide, and no acylation, lipidation, PEGylation, metal center or glycosylation. It has no sequence relationship to somatropin or to growth-hormone-releasing hormone; it is a structurally unrelated five-residue peptide sharing no residue stretch with somatropin. Worth showing because it makes the three non-standard positions visible in the arithmetic: Ala-His-Phe-Phe-Lys-NH2 as an all-proteinogenic scaffold is C33H45N9O5 at 647.78 average; adding CH2 for Aib in place of Ala and C4H2 for 2-naphthylalanine in place of phenylalanine gives C38H49N9O5.

Molecular formula

Free base C38H49N9O5; mono-acetate C40H53N9O7; bis-acetate C42H57N9O9; mono-trifluoroacetate C40H50F3N9O7; bis-trifluoroacetate C42H51F6N9O9.

Average mass

Free base 711.868 Da (C38H49N9O5) on IUPAC 2021 abridged conventional atomic weights; listings commonly print 711.87. On the older pre-2021 conventional set the same formula gives 711.85, which is the figure one chemical database publishes for CAS 170851-70-4 and which one institutional catalog rounds to 711.9. Salts: mono-acetate 771.92; bis-acetate 831.97; mono-trifluoroacetate 825.89; bis-trifluoroacetate 939.91, of which 24.3 percent of the gross weight is counterion.

Monoisotopic mass

Monoisotopic mass 711.3857 Da neutral. [M+H]+ 712.3930, which is the number a high-resolution identity test reports against the plus or minus 10 ppm limit — a window of plus or minus 0.0071 Da. [M+2H]2+ 356.7001; [M-H]- 710.3784. All of these follow from the stated formula.

Salt / variant note

Supplied as a salt — acetate where the manufacturer performed a salt exchange, trifluoroacetate where it did not — and with up to three protonatable sites (the N-terminal amine, the histidine imidazole and the lysine side chain), so mono-, bis- and tris-salt stoichiometries all occur and the counterion accounts for a material share of gross vial weight. A single peptide backbone, but at least six distinct articles ship under the one name, and one class of substitution is invisible to mass spectrometry. Free base: C38H49N9O5, 711.87 average / 711.3857 monoisotopic. Des-amido free acid impurity: C38H48N8O6, 712.85 / 712.3697 — +0.98 Da, a routine synthesis and storage impurity, not resolved by ordinary reversed-phase retention and inside any tolerance stated in whole daltons. Mono-acetate: C40H53N9O7, 771.92 / 771.4068. Bis-acetate: C42H57N9O9, 831.97 / 831.4279. Mono-trifluoroacetate: C40H50F3N9O7, 825.89 / 825.3785. Bis-trifluoroacetate: C42H51F6N9O9, 939.91 / 939.3714 — 24.3 percent of the gross vial weight is counterion, so a 5 mg gross fill of the bis-TFA salt is 3.8 mg of peptide. The invisible class is stereochemical: L-epimers at position 3 and position 4 are exactly isobaric with the D-residues and co-elute on achiral columns — a fully L-configured pentapeptide has formula C38H49N9O5 and mass 711.87 and will pass both an RP-HPLC area-percent test and an accurate-mass test to any precision. A second invisible variant is constitutional: beta-(1-naphthyl)alanine at position 3 is an exact constitutional isomer of the 2-naphthyl building block and gives the identical formula and identical mass to every decimal place, so ring regiochemistry is controlled by retention against a qualified building-block standard, not by mass. The detectable synthesis error is [Ala1]-ipamorelin, the Aib-to-Ala substitution, C37H47N9O5, 697.84 / 697.3700 — exactly 14.03 Da lighter. The family substitutions that are separate peptides rather than ipamorelin are GHRP-2 (C45H55N9O6, 817.99 / 817.4275, +106.1), GHRP-6 (C46H56N12O6, 873.03 / 872.4446, +161.2) and hexarelin (C47H58N12O6, 887.06 / 886.4602, +175.2).

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.

Published literature exists and is preclinical in substance: several dozen primary rodent and in-vitro pharmacology reports, the bulk of them originator work from the mid-1990s onward, with a comparatively thin independent replication record. A small number of company-sponsored Phase 1 and Phase 2 studies were registered and completed in the 2000s for post-operative gastrointestinal indications; the sponsor discontinued the program and no product has been approved in any jurisdiction. No Phase 3 dataset exists. The citation index for this record carries the originator pharmacology papers, the registered trial identifiers and their posted status, and an explicit statement that no approved product and no Phase 3 evidence exist.

4 Storage & specification

Storage

Supplied as a white lyophilized powder, acetate salt, in a screw-cap amber borosilicate vial with a PTFE-lined closure. This is A laboratory-chemical presentation: it is not a stoppered and crimped injection vial, it is not sterile, and it carries no sterility claim. Store at -20 degrees C plus or minus 5 degrees C, desiccated, protected from light — the naphthalene ring makes the solid photosensitive, and the imidazole makes the reconstituted solution pH-sensitive. The salt is hygroscopic, with up to three protonatable sites; the vial is equilibrated to room temperature before opening so that atmospheric moisture does not condense onto the cake, and subdivision is performed quickly with the container closed immediately after weighing. Reconstituted solution is aliquoted single-use and held at -80 degrees C; repeated freeze-thaw is prohibited on the label rather than merely discouraged. The article is segregated at the weighing bench from GHRP-2, GHRP-6 and hexarelin, which sit on adjacent shelves in every catalog in this market and are the three substitutions to expect. It ships ambient with a labeled cumulative excursion allowance and a single-use temperature logger in every export carton.

Shelf life

Provisional retest interval 24 months from release at -20 degrees C plus or minus 5 degrees C, desiccated and protected from light. Provisional pending company stability data: the interval is confirmed or shortened on the strength of an ICH Q1A(R2)-style protocol run on the first three commercial lots — 12 months real time at the labeled condition with pulls at 0, 3, 6, 9 and 12 months, plus 6 months accelerated at 40 degrees C / 75 percent relative humidity — assayed by the stability-indicating RP-HPLC method specified in the release panel, with the des-amido free acid and total related substances as the stability-indicating attributes and an ICH Q1B photostability arm run once on the launch lot in the final container. Material passing retest is re-dated for a further 12 months; material failing is destroyed and the destruction is published. A retest date is printed on every vial, and first-expiry-first-out is enforced against that date rather than against receipt date.