Independent analysis puts a QST exenatide lot at 98.4%, against 95.6% on the certificate

A peptide content determination commissioned by the Journal on a 15 mg exenatide vial from QST has returned 86% of the labelled mass. Chromatographic purity on the same vial was above 98.4%. The two numbers measure different things and only one of them was on the certificate.

The Journal purchased 3300 vials from the same lot and had 15 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 3300 vials from the same lot and had 15 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 not offered as a standard release test by any of the twenty companies in the Journal’s dossier programme. Sterility and endotoxin are separate disciplines again, and are neither tested nor claimed.

Lorcan Feeney, analytical services director at an independent laboratory, was more cautious. "One lot tells you about one lot. I would not draw a conclusion about a company from a single determination, and I would not let a company draw one either."

QST’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.