VendorInvestigate result on a Changsha liraglutide lot lands 3.2 points above the supplier’s stated figure

A peptide content determination commissioned by the Journal on a 10 mg liraglutide vial from SWB has returned 92% 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 97.6%. The two numbers measure different things, and this is one of the few certificates in the trade to print both.

Reported figures across the set were: highest 97.6%, lowest 94.5%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 20 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 14 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.

Purity became this trade’s single figure of merit because it is the cheapest measurement to obtain and the easiest to compare. Peptide content, which determines how much drug is actually in a vial, costs several times as much and is quoted as a priced addition by most of the twenty companies in the Journal’s dossier programme rather than carried as a standard release test. Sterility and endotoxin are separate disciplines again, and are neither tested nor claimed.

"The useful thing in that report is not the percentage, it is the system suitability data," said Dr Sirichai Boonmee, peptide chemist, Chulalongkorn University. "It is the only part that tells you whether the percentage means anything."

SWB’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.