PeptideMeter result on a Zhuhai cagrilintide lot lands 1.5 points above the supplier’s stated 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 15 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.

"The useful thing in that report is not the percentage, it is the system suitability data," said Dr Beatriz Sarmiento, clinical pharmacologist, Universidad de Navarra. "It is the only part that tells you whether the percentage means anything."

MKM’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.