PeptideMeter result on a Qingdao cagrilintide lot lands 1.4 points below the supplier’s 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 86% 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 2300 vials from the same lot and had 18 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.

Sinéad Corrigan, patient advocate and former trial participant, 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."

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.