Independent analysis puts a WXT semaglutide lot at 98.8%, against 95.3% on the certificate

Janoshik has published a purity determination of 98.8% on a 15 mg vial of semaglutide supplied by WXT, against a figure of 95.3% on the certificate that accompanied the vial. The sample was submitted by the Journal in May 2024 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

The Journal purchased 8 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.

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 gap that matters is not between the two laboratories, it is between either of them and the certificate," said Havel Novotný, independent laboratory quality manager. "One of those documents states a method. Compare like with like and most of this disappears."

WXT’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.