Which structural attributes of tesamorelin as a GHRH analogue define MS identity?
Tesamorelin is described in published evaluations as a synthetic analogue of human growth hormone-releasing factor (GRF), equivalently termed a GHRH analogue, and it has been identified under the development code TH9507 (PMID:17086939; PMID:19243281; PMID:21283099; PMID:20554713). Independent reviews classify the substance as a growth hormone-releasing factor analogue (PMID:22298602), and GRF-analogue reports use the same designation (PMID:27121785). Those sources fix the chemical class that a research specification should name on a certificate of analysis: a defined GHRH analogue rather than unmodified native GHRH. Mass spectrometry identity confirmation tests that class claim against spectra from the lot in hand.
Research specifications treat tesamorelin as a 44-residue GHRH(1–44) backbone bearing C-terminal amidation and an N-terminal trans-3-hexenoyl (hexenoyl) acyl group. The hexenoyl moiety is the principal mass increment relative to unmodified GHRH(1–44)-NH2 and is therefore a non-negotiable identity attribute. A laboratory checklist should list three mandatory features before any purity number is interpreted: the 44-residue sequence, the N-terminal hexenoyl group, and the C-terminal amide. Absence of any one feature means the substance is chemically different, even if reversed-phase HPLC displays a single major peak.
Literature nomenclature aligns CoA substance names with GRF-analogue evaluations, but a published classification is not lot identity. Amino-acid analysis, net peptide content and HPLC area-percent address composition and chromatographic purity. Only mass spectrometry locates the hexenoyl mass shift and the amide terminus. Specifications should therefore require a deconvoluted intact mass and, for complete confirmation, fragment-ion evidence for the N-terminal modification.
How does tesamorelin GHRH analogue mass spectrometry identity confirmation use intact ESI-MS?
Intact electrospray ionisation mass spectrometry is the first orthogonal measurement in tesamorelin GHRH analogue mass spectrometry identity confirmation. After desalting or reversed-phase liquid-chromatographic introduction, the peptide is ionised in positive mode from water–acetonitrile containing formic acid or dilute acetic acid. A long, highly basic GHRH analogue occupies a spread of charge states. Identity work uses that entire envelope: each assigned multiply charged line must be consistent with one intact mass.
Analysts should inspect every major charge state for three properties. First, the observed m/z must match the theoretical m/z calculated from the declared elemental composition and the assigned charge. Second, isotope spacing must equal approximately 1/z; incorrect spacing indicates a misassigned envelope. Third, a second unresolved envelope under the same chromatographic peak indicates a different intact mass and must be explained before identity is passed. Deconvolution converts the envelope to a zero-charge mass. The CoA should report a representative observed m/z, the assigned charge, the deconvoluted mass, the theoretical mass, and the mass error in daltons and in parts per million.
Acceptance windows belong in the method. Unit-resolution analysers often support average-mass matching within about 0.5–1.0 Da in this mass range when calibration is current. High-resolution time-of-flight or electrostatic-trap instruments can support monoisotopic matching at low-ppm error, which separates the hexenoyl analogue from unmodified GHRH amide more decisively. Reporting a pass without stating the window makes the result non-reproducible.
Confounders include sodium and potassium adducts, residual trifluoroacetate ion pairs, leftover protecting groups, and methionine oxidation (+16 Da). Adducts should be labelled as adducts. A deconvoluted mass that matches unmodified GHRH(1–44)-NH2, or a truncated chain, fails tesamorelin identity regardless of HPLC area-percent. Calibration should use a peptide standard in a comparable m/z region, with a recorded calibration date. Mass-scale suitability is evidence that the analyser was accurate when the lot was measured.
How should tandem MS and peptide mapping verify hexenoyl-GHRH sequence features?
Intact mass shows that elemental composition is consistent with tesamorelin; it does not prove residue order or the site of the acyl group. Tandem mass spectrometry supplies that localisation. Collision-induced dissociation of a selected intact charge state, or of enzymatic peptides, generates b- and y-type ions. Because the hexenoyl group is N-terminal, b ions and other N-terminal fragments should carry the acyl mass increment, whereas y ions from the amidated C terminus should match GHRH C-terminal masses with the amide hydrogen count. A spectrum in which y ions fit tesamorelin but b ions fit unmodified GHRH is evidence of a missing or different N-terminal modification and is an identity failure for the analogue.
For peptide mapping, trypsin is a rational first enzyme. The GHRH-derived sequence is rich in lysine and arginine, so digestion produces shorter peptides that can be measured at higher mass accuracy than the intact 44-mer. The N-terminal tryptic peptide is the critical identity reporter because it carries the hexenoyl-modified N terminus. Laboratories should tabulate expected precursor m/z values for that reporter peptide and require MS/MS sequence tags that include the modified residue. Residue-coverage targets, for example a stated percentage of the sequence represented by assigned fragments, belong in the method together with rules for unassigned peaks above a stated intensity threshold.
MS/MS identity confirmation should be filed as annotated spectra or fragment tables, not as an undocumented MS pass. The batch record should identify the precursor m/z, the charge state, the collision energy or normalised collision energy, and the fragment ions used to assign the N-terminal hexenoyl group and the C-terminal amide. If enzymatic mapping is used, the enzyme lot, digestion time, and quench conditions should be recorded so that missing reporter peptides can be interpreted as incomplete digestion rather than as a sequence variant.
How should LC-MS distinguish tesamorelin identity from related-substance ions?
Reversed-phase LC–MS is the practical means of ensuring that the mass assigned as tesamorelin belongs to the principal chromatographic peak and not to a co-eluting related substance. Identity and purity answer different questions. Purity is typically an HPLC area-percent at a stated wavelength and integration threshold. Identity is a mass and fragment match to the declared GHRH analogue. A lot can be chromatographically dominated by one peak and still be the wrong analogue, or it can be the correct analogue with measurable related substances that must be labelled as such rather than as tesamorelin.
Related substances that affect identity interpretation include N-terminal des-hexenoyl GHRH amide, whose mass decrement equals the acyl group; truncated sequences from incomplete coupling or cleavage; methionine oxidation; asparagine or glutamine deamidation (+1 Da); aspartimide or isoaspartate rearrangements that may be isobaric with the parent; and residual protecting groups. Isobaric species are not resolved by a single deconvoluted mass. They require chromatographic separation, fragment-ion differences, or both. Deamidation at unit-resolution intact mass is easily missed, so high-resolution deconvolution or peptide mapping should be specified when the CoA claims the native Asn/Gln composition.
The extracted-ion chromatogram of predicted tesamorelin charge states should coincide with the ultraviolet or charged-aerosol peak that is integrated for purity. If the main photometric peak’s mass is not tesamorelin, the lot fails identity irrespective of area-percent. If tesamorelin mass is present only as a minor peak, the material is a mixture and should not be labelled as identity-confirmed tesamorelin without a qualified major-component assignment and a related-substance list.
Ion-source artefacts such as in-source oxidation, water loss, or ammonia loss must be distinguished from genuine related substances by retention time: source artefacts share the parent retention time, whereas true impurities generally do not. Method records should state capillary voltage and source temperature so that in-source chemistry can be interpreted during review. An orthogonal HPLC condition—different ion-pair reagent, pH, or column chemistry—plus MS reduces the risk that an isobaric impurity remains hidden under the main peak. Identity confirmation is therefore a peak-assigned mass result, not a survey scan of an unfractionated vial.
What CoA fields and acceptance rules should Australian laboratories require?
For research lots supplied from local Australian stock with tracked dispatch, identity evidence lives in the batch documentation pack, not in a catalogue name on the vial. A tesamorelin CoA that supports mass spectrometric identity confirmation should include the substance name as tesamorelin, identified as a GHRH analogue and, where used, as TH9507; a lot or batch number identical to the vial label; the theoretical monoisotopic or average mass with the elemental formula and a free-peptide versus salt convention; observed m/z values with charge states; the deconvoluted mass and mass error; a statement of the MS method, including electrospray or MALDI, LC–MS or infusion, and analyser type; a calibration reference; and, where MS/MS was performed, the precursor m/z and the assigned diagnostic fragments for the hexenoyl N terminus and the C-terminal amide.
HPLC purity, retention time, column identity, gradient table and detection wavelength belong on the same CoA but must not replace the mass fields. Net peptide content, counter-ion identity (acetate or trifluoroacetate) and water content explain gravimetric composition; they do not confirm sequence or the N-terminal acyl group. Laboratories should reject CoAs that state only that mass spectrometry was consistent with tesamorelin without numerical masses, or that omit the lot number, method identifier or mass-error window. A purity chromatogram without an assigned intact mass is not identity confirmation.
Traceability requires that the spectrum or peak table can be retrieved against the lot. A batch report should record sample-preparation solvent, dilution and filtration, the sample position in the chromatographic sequence, blank and system-suitability outcomes, and the data-file name. Multi-vial orders drawn from one lot should share a single identity package so that every vial points to the same deconvoluted mass and the same MS/MS assignment. Where independent confirmation is required, a retained vial can be re-analysed by LC–MS and compared with the supplier’s observed mass within the documented window.
Identity criteria should be written before data review: deconvoluted mass within a stated window, isotope spacing that supports the charge assignment, no alternative intact mass as the major LC peak, and diagnostic hexenoyl-bearing N-terminal fragments when MS/MS is specified. A passing HPLC purity result does not override an identity failure. If the calibration standard lies outside its mass window, the tesamorelin result is not valid. All of this documentation is research-use only: the CoA is an analytical identity record for laboratory materials, and vial labels, CoA headers and dispatch paperwork must carry one lot number.
Order Tesamorelin with documentation
If this guide helped you evaluate Tesamorelin for laboratory work, the next step is documented supply: research-grade stock from Australian warehouses, Express tracked shipping, and batch documentation with every order.
Open the Tesamorelin card on the ClaraScience shop for current stock and add-to-cart, or request wholesale access when you need bulk restocks and tier pricing.
Frequently asked questions
Does HPLC purity confirm tesamorelin identity?
No. HPLC area-percent at a stated wavelength measures chromatographic purity of the integrated peak. Identity requires an intact mass and, preferably, fragment ions that match the declared GHRH analogue, including the N-terminal hexenoyl group and C-terminal amide. A single HPLC peak can be the wrong analogue or an isobaric related substance. Laboratories should treat purity and identity as separate CoA fields with separate acceptance rules.
Why must mass spectrometry confirm the hexenoyl group?
The trans-3-hexenoyl N-terminal acyl group is the covalent feature that distinguishes tesamorelin from unmodified GHRH(1–44)-NH2. Intact mass should show the corresponding mass increment, and MS/MS should place that increment on N-terminal fragments or on the N-terminal tryptic peptide. A lot whose mass matches des-hexenoyl GHRH amide fails tesamorelin identity even if HPLC purity is high.
Which CoA mass fields should Australian laboratories require?
Minimum fields are lot number matching the vial, theoretical mass with monoisotopic or average convention, observed m/z with charge, deconvoluted mass, mass error, analyser type, and calibration reference. Where tandem MS was performed, precursor m/z and diagnostic hexenoyl and amide fragments should be listed. Statements such as MS consistent without numbers are not sufficient for research-lot identity confirmation.
Can MALDI-TOF replace LC–ESI-MS/MS for tesamorelin identity?
Linear MALDI-TOF can support intact molecular-weight confirmation as an orthogonal check. It does not, by itself, localise the hexenoyl group or confirm that the measured mass belongs to the principal HPLC peak. LC–ESI-MS with charge-state deconvolution, and MS/MS or peptide mapping for the N-terminal modification, remain the more complete identity package.
How is tesamorelin distinguished from unmodified GHRH by MS?
Unmodified GHRH(1–44)-NH2 lacks the N-terminal hexenoyl mass increment. Intact deconvolution should separate the two compositions by tens of daltons, well beyond typical calibration error. Fragmentation should show hexenoyl-bearing b ions for tesamorelin and unmodified N-terminal fragments for GHRH amide. Matching the wrong intact mass is an identity failure, not a purity comment.
References
- PMID:17086939 — Drug evaluation: tesamorelin, a synthetic human growth hormone releasing factor — Curr Opin Investig Drugs — 2006
- PMID:19243281 — Tesamorelin, a human growth hormone releasing factor analogue — Expert Opin Investig Drugs — 2009
- PMID:21283099 — Tesamorelin — Nat Rev Drug Discov — 2011
- PMID:22298602 — Tesamorelin: a growth hormone-releasing factor analogue for HIV-associated lipodystrophy — Ann Pharmacother — 2012
- PMID:20554713 — Effects of tesamorelin (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data — J Clin Endocrinol Metab — 2010
- PMID:27121785 — Impact of Tesamorelin, a Growth Hormone-Releasing Factor (GRF) Analogue, on the Pharmacokinetics of Simvastatin and Ritonavir in Healthy Volunteers — Clin Pharmacol Drug Dev — 2013
Research use only
This article is provided for laboratory research and educational purposes only. Products referenced are not for human or veterinary use. ClaraScience makes no therapeutic, medical, or efficacy claims, and nothing here constitutes medical advice.
