PeptideMeter result on a Zhuhai cagrilintide lot lands 1.5 points below the supplier’s figure

PeptideMeter has released a batch of 24 analytical reports on research-grade cagrilintide lots, including material from MKM and CPC. Reported purities range across roughly 1.5 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

Reported figures across the set were: highest 96.9%, lowest 95.6%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 24 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

The Journal purchased 1900 vials from the same lot and had 24 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.

Rowena Ashcombe, community pharmacist and diabetes educator, 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."

MKM’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.