Quality control and batch release

📍 Where we are: Part 20 of the journey — the medicine is made, but no one can use it yet. First, we have to prove it is good.

We have a finished batch of medicine sitting in vials. But "finished" does not mean "approved." Before a single vial reaches a patient, the batch must pass a battery of tests and a careful human review. This chapter is about that final gate.

The simple version

Imagine a brand-new car rolling off the assembly line. Before it can leave the factory, inspectors check the brakes, the lights, the engine, the paint. Then a manager reads the whole inspection report and signs a release form. Only then does the car ship. Our medicine goes through the exact same thing: a multi-point inspection, then a signature.

What actually happens

Two different teams guard the gate, and it is important not to mix them up.

• Quality Control (QC) is the lab that tests the medicine. They take samples and run experiments to measure quality.
• Quality Assurance (QA) is the system and the people who make sure everything was done correctly, and who approve the batch. QC measures; QA decides.

Long before the end, QC has already been watching. Tests taken during manufacturing are called in-process controls (IPCs) — checks at each step, like measuring temperature while you cook, not just tasting the final dish. They catch problems early, while there is still time to react.

At the end, QC runs the release tests on the finished batch. Each one answers a simple question:

1. Identity — is this actually the right antibody, and not something else?
2. Purity and impurities — how much unwanted material is left? They look for aggregates (antibodies clumped together, which can be unsafe), host cell protein (HCP) (leftover protein from the factory cells), and stray DNA.
3. Potency — does the medicine actually work? A bioassay (a test using living cells or molecules) proves the antibody still does its job in the body.
4. Sterility — are there any living microbes? There must be none.
5. Endotoxin — are there toxins shed by bacteria? These cause fevers, so the limit is tiny.
6. Appearance, concentration, and pH — is it clear and the right strength and acidity?

These tests are not random. Each one maps back to a critical quality attribute (CQA) — a property defined during development as something that must be right for the medicine to be safe and effective. The release tests are how we confirm every CQA landed inside its target.

Every result, plus the complete batch record (the full diary of how the batch was made), is compiled into one document: the Certificate of Analysis (CoA). Then QA, or a legally responsible Qualified Person, reviews all of it and makes the disposition decision — the verdict.

Only a batch that is released is allowed to ship. A rejected batch never reaches a patient.

Why it matters

This is the last line of defense. Everything upstream — the cells, the bioreactor, the polishing, the fill-finish — exists to produce a medicine that passes here. If a batch is wrong and slips through, a real person gets a dose that may be too weak, contaminated, or unsafe. So the gate is deliberately strict, and the decision is made by humans who sign their names to it.

One failed test can scrap everything

These tests are pass or fail. A single failed critical test — say, sterility — can condemn an entire batch that took weeks to grow and purify and is worth millions of dollars. There is no patching it. This is why getting every earlier step right, the first time, matters so much.

In the real world

Classic release testing happens at the very end, after the whole batch is made — which means you wait weeks to learn whether it passed. The modern direction is process analytical technology (PAT): sensors that measure quality continuously, during manufacturing. In continuous and intensified processes — the approach the U.S. NIIMBL institute and its SABRE pilot facility are pioneering — the dream is real-time release, where the data proving quality is gathered as the medicine is made, not after. Fewer surprises at the final gate.

Key terms

• Quality Control (QC) — the lab that tests samples to measure a batch's quality.
• Quality Assurance (QA) — the system and people who verify everything was done right and approve the batch.
• In-process control (IPC) — a quality test taken during manufacturing, not only at the end.
• Release test — a final test the finished batch must pass before shipping.
• Potency / bioassay — a test proving the medicine actually works in a biological system.
• Sterility — the requirement that there are no living microbes in the product.
• Endotoxin — a fever-causing toxin from bacteria, kept far below a strict limit.
• Critical quality attribute (CQA) — a property that must be right for the medicine to be safe and effective.
• Certificate of Analysis (CoA) — the document listing all test results for a batch.
• Batch record — the complete written history of how a batch was made.
• Disposition — the final decision to release or reject a batch.
• Qualified Person — the legally responsible individual who can release a batch.