Independent analysis puts a SGN exenatide lot at 96.4%, against 94.7% on the certificate

Medutest has released a batch of 15 analytical reports on research-grade exenatide lots, including material from SGN and TFC. Reported purities range across roughly 0.9 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

The Journal purchased 18 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 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.