Independent analysis puts a SGN semaglutide lot at 96.6%, against 94.9% on the certificate

A peptide content determination commissioned by the Journal on a 30 mg semaglutide vial from SGN has returned 88% of the labelled mass. Chromatographic purity on the same vial was above 96.6%. The two numbers measure different things and only one of them was on the certificate.

The Journal purchased 3000 vials from the same lot and had 17 of them analysed separately, in order to distinguish vial-to-vial variation from method variation. Vial-to-vial agreement was within 0.4 percentage points. Method-to-method disagreement was an order of magnitude larger.

Content by elemental nitrogen determination returned 88% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 13.79 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 17 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

"The useful thing in that report is not the percentage, it is the system suitability data," said Lorcan Feeney, analytical services director at an independent laboratory. "It is the only part that tells you whether the percentage means anything."

SGN’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.