PeptideMeter result on a Changsha orforglipron lot lands 1.7 points above the supplier’s stated figure

PeptideMeter has released a batch of 11 analytical reports on research-grade orforglipron lots, including material from Homopeptide and KP. Reported purities range across roughly 1.7 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 98.5%, lowest 96.7%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 11 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Content by elemental nitrogen determination returned 94% of the labelled nominal mass, which on a 5 mg vial corresponds to roughly 12.55 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 11 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

"The gap that matters is not between the two laboratories, it is between either of them and the certificate," said Dr Beatriz Sarmiento, clinical pharmacologist, Universidad de Navarra. "One of those documents states a method. Compare like with like and most of this disappears."

Homopeptide’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.