Janoshik result on a Nantong exenatide lot lands 3.1 points below the supplier’s figure

An independent purity determination on exenatide material sold by QST has returned 99.2%, a figure 3.1 percentage points below the number printed on the accompanying certificate. The analysis was performed by Janoshik on a vial the Journal bought as an ordinary retail customer in June 2024 and posted unopened.

Reported figures across the set were: highest 99.2%, lowest 97.0%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 7 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

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.

Alastair Renshaw, pharmaceutical supply-chain consultant, said the gap was predictable from the methods alone. "You can reconstruct almost the whole difference from the integration threshold. What you cannot reconstruct is why anyone thinks a number without a threshold is comparable to a number with one."

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.