PeptideMeter result on a Xianning semaglutide lot lands 4.4 points below the supplier’s figure

A peptide content determination commissioned by the Journal on a 2 mg semaglutide vial from WXT has returned 94% of the labelled mass. Chromatographic purity on the same vial was above 98.8%. The two numbers measure different things and only one of them was on the certificate.

Reported figures across the set were: highest 98.8%, lowest 95.6%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 14 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

The wider context is that material sold for research use carries no regulatory release specification in any jurisdiction the Journal has examined. A certificate is a commercial document, not a compliance one, and its content is whatever the issuer chooses to put on it. That is the gap independent testing fills, and it fills it imperfectly.

Alastair Renshaw, pharmaceutical supply-chain consultant, 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."

WXT’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.