PeptideMeter result on a Qingdao cagrilintide lot lands 1.4 points above the supplier’s stated figure

PeptideMeter has published a purity determination of 96.1% on a 2 mg vial of cagrilintide supplied by SGN, against a figure of 91.9% on the certificate that accompanied the vial. The sample was submitted by the Journal in July 2025 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

Content by elemental nitrogen determination returned 93% of the labelled nominal mass, which on a 2 mg vial corresponds to roughly 4.18 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 17 vials from the same lot at retail and had four 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 Dr Beatriz Sarmiento, clinical pharmacologist, Universidad de Navarra. "Purity is what you can afford. Content is what you need."

SGN’s dossier has been updated with this determination and with the company’s response to it. The dossier’s ordering box records the lead times, the minimum quantities and what a buyer should ask for at the point of order.