Why did two WXT lots of cagrilintide differ on content assay?

Stated plainly: WXT · cagrilintide.

This is not behaving the way I expected and I want to understand the discrepancy before I act on it.

I have photographed the current state and recorded the conditions, so I can answer follow-up questions precisely.

Should I be treating this as a failure or as noise?

A certificate that reports one test result on one vial extrapolates to claim that all two hundred vials in the lot are identical, which is an assumption worth questioning.

Under AQL sampling plans, testing two vials from a fifty-vial lot gives you an operating characteristic curve that tells you what risks you are accepting.

To be exact about it, if the entire lot failed qualification, a retest on a different vial is sometimes done, but reporting a retest result under the same lot number is misleading.

Lyophilised peptide homogeneity studies show that vial-to-vial variation is usually small but occasionally large, depending on the distribution in the freeze-dryer.

Assume segregation is possible, and design your sampling to catch it if it exists.

The single most misleading statement on a research-grade certificate is a lot number with no statement of how many vials from that lot were tested.

Acceptance Sampling by Attributes defines the number of samples you need from a lot to claim a specified quality level at a specified risk — it is in ANSI standard Z1.4.

Stratified sampling — testing one vial from the top, one from the middle, and one from the bottom of a shipment — is cheap insurance against segregation.

I would treat a "complies with" statement without sampling details as a claim rather than as evidence.

The practical summary: a lot number without a sampling statement is a lot number without meaning.

The practical consequence is that spot-testing one vial from a new supplier is better than assuming they are all the same.

For a quantitative result like content, the acceptable range determines how many vials you need to test to establish the lot complies.

The caveat is that sampling is a trade-off between cost and confidence, and neither test nor assumption is cost-free.

If testing multiple vials, state how many you tested and why you chose those vials.

More usefully, batch testing establishes what can be claimed about the lot as a whole, and the sample size determines how much you can actually claim.

Published segregation failures show that even modern automated processes sometimes produce lots with measurable vial-to-vial variation.

Sampling plans for pharmaceutical manufacturing are defined in ISO 2859 and ANSI Z1.4, and they are based on statistical sampling theory.

Assume segregation is possible, and design your sampling to catch it if it exists.