What is Tesamorelin?
Tesamorelin is recorded under CAS 218949-48-5, formula C221H366N72O67S, average molecular weight 5135.9, with the synonym GRF(1-44) analogue. No residue listing is carried for this entry, so the sequence is not reproduced. At just over five kilodaltons it is one of the larger molecules in the catalog.
The distinguishing point against the shorter analogue in this catalog is length. Where the 1-29 fragment keeps only the minimum receptor-activating span, this one retains the full 1-44 sequence and adds a modification at the amino terminus, which is why it resists the dipeptidyl peptidase 4 cleavage that limits the unmodified hormone. The single sulfur in the formula is consistent with one methionine, making oxidation a consideration alongside the aggregation typical of peptides this size.
The published literature uses it as a long-lived GHRH receptor agonist. Pituitary preparations show receptor-mediated growth hormone release, and animal work has examined the secretion pattern produced by an analogue that persists longer in circulation while acting through the same receptor. How far the preserved pulsatility seen in animal models depends on somatostatin feedback rather than the analogue itself is an active question.
Reconstitution & handling
Sterile or bacteriostatic water is the usual diluent, added slowly down the inside wall. Peptides of this size dissolve gradually, so let the vial stand and swirl at intervals rather than agitating, since shear and foaming both promote aggregation. Concentration is labelled mass over diluent volume, with net peptide content applied when a molar figure is needed.
Storage & stability
Hold the sealed dry vial at -20 °C, desiccated and protected from light. In solution the material belongs at 2 to 8 °C, divided into single-use aliquots. Freeze-thaw is the specific thing to avoid, because aggregation rather than hydrolysis is the dominant failure mode at this molecular weight. Visible haze or fine precipitate in a thawed stock indicates aggregation and should not be used for quantitative work.
How it's tested
Reversed-phase HPLC at 214 and 220 nm provides the purity figure, and size exclusion chromatography is the orthogonal method for detecting aggregate. Identity is confirmed by mass spectrometry against the theoretical average mass of 5135.9, deconvoluted from the multiply charged envelope. Net peptide content and water are reported separately from chromatographic purity, and a lot-matched certificate of analysis is available on request.