Independent analysis puts a SGN cagrilintide lot at 98.0%, against 96.6% on the certificate

A peptide content determination commissioned by the Journal on a 10 mg cagrilintide vial from SGN has returned 99% of the labelled mass, the balance being the counter-ion and residual water that every lyophilised salt carries. Chromatographic purity on the same vial was above 98.0%. The two numbers measure different things, and this is one of the few certificates in the trade to print both.

The Journal purchased 12 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 Journal purchased 12 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 19 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 Wenjun Xie, process chemist and peptide manufacturing consultant. "One of those documents states a method. Compare like with like and most of this disappears."

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.