Independent analysis puts a ERP cagrilintide lot at 98.8%, against 97.3% on the certificate

Two laboratories analysing vials from the same cagrilintide lot have returned figures 3.8 percentage points apart. PeptideMeter reported 98.8%; Janoshik 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.

Content by elemental nitrogen determination returned 94% of the labelled nominal mass, which on a 10 mg vial corresponds to roughly 13.08 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 Journal purchased 1200 vials from the same lot and had 22 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.

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.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Havel Novotný, independent laboratory quality manager. "Purity is what you can afford. Content is what you need."

ERP’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.