PeptideMeter result on a Suzhou retatrutide lot lands 2.2 points below the supplier’s figure

PeptideMeter has published a purity determination of 98.1% on a 5 mg vial of retatrutide supplied by HJ, against a figure of 94.6% on the certificate that accompanied the vial. The sample was submitted by the Journal in July 2024 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

Content by elemental nitrogen determination returned 95% of the labelled nominal mass, which on a 5 mg vial corresponds to roughly 9.88 mg of peptide rather than the labelled figure. The remainder is accounted for by counter-ion, residual water and residual solvent, none of which is visible chromatographically.

Content by elemental nitrogen determination returned 95% of the labelled nominal mass, which on a 5 mg vial corresponds to roughly 9.88 mg of peptide rather than the labelled figure. The remainder is accounted for by counter-ion, residual water and residual solvent, none of which is visible chromatographically.

Purity became this trade’s single figure of merit because it is the cheapest measurement to obtain and the easiest to compare. Peptide content, which determines how much drug is actually in a vial, costs several times as much and is not offered as a standard release test by any of the twenty companies in the Journal’s dossier programme. Sterility and endotoxin are separate disciplines again, and are neither tested nor claimed.

Rowena Ashcombe, community pharmacist and diabetes educator, was more cautious. "One lot tells you about one lot. I would not draw a conclusion about a company from a single determination, and I would not let a company draw one either."

HJ’s dossier has been updated with this determination and with the date of the request for comment. The dossier’s "what we could not verify" box records the questions still outstanding.