PeptideMeter result on a Hangzhou exenatide lot lands 3.5 points below the supplier’s figure

PeptideMeter has released a batch of 8 analytical reports on research-grade exenatide lots, including material from HJ and Homopeptide. Reported purities range across roughly 3.5 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

Content by elemental nitrogen determination returned 95% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 7.70 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.

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.

"The figure is not wrong and neither is theirs," said Alastair Renshaw, pharmaceutical supply-chain consultant. "They are answers to two different questions and the trade has decided to pretend there is only one question. Print the gradient and the argument disappears."

HJ’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.