PeptideMeter result on a Wuhan dulaglutide lot lands 1.8 points below the supplier’s figure

Two laboratories analysing vials from the same dulaglutide lot have returned figures 1.8 percentage points apart. PeptideMeter reported 99.2%; VendorInvestigate reported a lower number on a shallower gradient with a tighter integration threshold. Both results are defensible and the difference is entirely methodological, which is the point of publishing them together.

Reported figures across the set were: highest 99.2%, lowest 97.7%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 9 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Content by elemental nitrogen determination returned 93% of the labelled nominal mass, which on a 5 mg vial corresponds to roughly 11.88 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.

"The figure is not wrong and neither is theirs," said Rowena Ashcombe, community pharmacist and diabetes educator. "They are answers to two different questions and the trade has decided to pretend there is only one question. Print the gradient and the argument disappears."

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.