For cell and gene therapies, potency is not something you check at the end and hope is still there.
That is not a control strategy.
It is a late discovery strategy.
On November 2, 2026, FDA issued final guidance for manufacturers of cellular and gene therapy products. The guidance recommends a science- and risk-based Potency Assurance Strategy that connects material control, manufacturing process design, process control, in-process testing, and potency lot-release assays.
The goal is straightforward: every released lot should have the specific ability to achieve its intended therapeutic effect.
That sounds obvious.
In practice, it is a much bigger operating challenge than adding one more assay to the release panel.
What FDA Actually Changed
FDA's final guidance replaces the agency's 2011 potency-testing guidance for cell and gene therapy products.
FDA describes potency assurance as a multifaceted and flexible approach. The agency's recommendations span early development, manufacturing, approval, and post-approval monitoring.
The guidance addresses:
variability in raw materials;
manufacturing process controls;
testing during manufacturing;
potency assays used for lot release;
products with short shelf lives;
viral vector gene therapies; and
patient-specific therapies.
Those are the source facts.
Here is the operating lesson:
Potency cannot be handed off to the laboratory at the end of the process.
The Release Assay Is the Last Checkpoint
A potency assay matters.
It is also late.
By the time a lot reaches release testing, the product has already experienced its raw materials, its process conditions, its hold times, its operators, its equipment, its sampling decisions, and its data review.
The final assay can tell you something important about the lot.
It cannot prove that the system was controlled all the way there.
That is why a potency strategy has to connect the controls before release. The question is not only whether the result passed. The question is whether the organization understands why the result should be trusted.
If the answer depends on one late test carrying the entire argument, the system is doing too much work at the very end.
Raw Materials Are Part of the Potency Story
Cell and gene therapy teams already know that raw materials can be variable.
The harder question is whether that variability is being managed as a potency risk or merely documented as a purchasing and receiving activity.
Material identity, qualification, supplier oversight, storage, handling, and lot-to-lot variability all influence the process that follows.
If the organization does not understand which material attributes affect the product's biological activity, it is not ready to explain potency with much confidence.
This does not mean every material needs the same level of testing.
It means the control strategy should be based on what the material can actually change.
That is the difference between a risk-based system and a very expensive filing cabinet.
Process Control Has to Protect the Biology
Cell and gene therapy manufacturing is not just a sequence of steps.
It is a sequence of biological conditions.
The process has to preserve the attributes that matter to the intended therapeutic effect. That can include inputs, culture conditions, handling, timing, equipment, hold periods, transport, and the points where the product is exposed to additional variability.
The quality system should make those links visible.
When a process parameter changes, what potency risk changes with it?
When a raw material lot changes, what evidence is required?
When a hold time stretches because the schedule slipped, who decides whether the product is still within a defensible control strategy?
These are not questions for a final release meeting. They belong in process design and day-to-day manufacturing oversight.
Short Shelf Life Makes Weak Handoffs Obvious
Short-lived products do not leave much room for confusion.
The team may have limited time for manufacturing, testing, review, release, shipment, and administration. A delay in one part of the system can put pressure on every other part.
That pressure tends to expose weak ownership quickly.
Who can stop the clock?
Who can make the release decision?
Who can challenge an incomplete result?
Who owns the risk when the product is moving between manufacturing, quality, testing, logistics, and the clinical site?
If those answers are not clear before the lot is in motion, the organization will improvise under pressure. Improvisation is not automatically wrong. Unnamed improvisation is where control starts to disappear.
Patient-Specific Manufacturing Makes Ownership Visible
For a patient-specific therapy, the product is not an abstract batch on a planning board.
The manufacturing decision is tied to a person, a time window, and a chain of custody that has to hold together.
That makes the quality system more human, not less technical.
There is no room for the familiar phrase, “That is how the other team handles it.”
The team has to know:
what was received;
what was changed;
what was tested;
what was reviewed;
what was accepted; and
who had the authority to make the call.
The records should tell that story without requiring three meetings and a detective novel.
Questions Leaders Should Ask Now
Before the next major milestone, leadership should be able to answer:
Which raw-material attributes can change potency, and how are they controlled?
Which process parameters and hold times have the strongest link to the intended therapeutic effect?
What evidence connects in-process testing to the final potency assay?
How does the release strategy work when the product has a short shelf life?
Can the team trace a potency decision from the lot-release result back to the material and process conditions that created it?
Who owns the escalation when the available data are incomplete but the delivery clock is running?
These are not questions designed to create more paperwork.
They are questions designed to reveal whether the system is actually connected.
Build the Strategy Before the Pressure Arrives
FDA's guidance gives cell and gene therapy manufacturers a clearer framework for potency assurance. The work now is making that framework real in the operation.
That means connecting development, manufacturing, quality, analytical, regulatory, supply chain, and clinical timelines early enough to change the process when the facts demand it.
It means treating potency as a lifecycle responsibility.
It means refusing to let one final assay carry the weight of a system that was never designed to support it.
The best release decision is not the one made fastest at the end.
It is the one the organization can explain from the beginning.
Clarity first.
Ownership next.
Then movement.
Sources: FDA final guidance: Potency Assurance for Cellular and Gene Therapy Products and FDA press announcement, November 2, 2026.