Twenty-eight days is a number from somebody else’s product
Every degradation pathway accelerates by orders of magnitude on reconstitution, because the solvent that lyophilisation removed is the reagent most of them need.
Testing Dispatch
Independent analysis puts a HJ exenatide lot at 98.4%, against 97.3% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Two laboratories analysing vials from the same exenatide lot have returned figures 3.3 percentage points apart. PeptideMeter reported 98.4%; VendorInvestigate reported a lower number on a shallower gradient with a tighter integration threshold. Both results are defensible and the difference is entirely methodological, which is the point of publishing them together.
The Journal purchased 3200 vials from the same lot and had 3 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.
Discrepancies of one to two percentage points between a supplier’s figure and an independent determination are common and usually explicable: a faster gradient resolves fewer impurities, a higher integration threshold discards more small peaks, and a wider solvent-front exclusion window removes early-eluting fragments from the calculation altogether. None of that is misconduct. All of it is invisible unless the method is disclosed.
"The useful thing in that report is not the percentage, it is the system suitability data," said Lorcan Feeney, analytical services director at an independent laboratory. "It is the only part that tells you whether the percentage means anything."
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.
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The report states the gradient, the wavelength and the integration threshold, which is more than most.