Medutest result on a Wuxi dulaglutide lot lands 2.0 points below the supplier’s figure

A peptide content determination commissioned by the Journal on a 10 mg dulaglutide vial from WXT has returned 94% of the labelled mass. Chromatographic purity on the same vial was above 95.8%. The two numbers measure different things and only one of them was on the certificate.

Content by elemental nitrogen determination returned 94% of the labelled nominal mass, which on a 10 mg vial corresponds to roughly 14.82 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.

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, said the gap was predictable from the methods alone. "You can reconstruct almost the whole difference from the integration threshold. What you cannot reconstruct is why anyone thinks a number without a threshold is comparable to a number with one."

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.