How In-Process Testing Helps Prevent Cell Therapy

Cell therapy manufacturing leaves little room for error. A small change in cell health, contamination levels, nutrient use, or process conditions can affect an entire batch. By the time a problem appears in final testing, teams may have already spent days or weeks on the run.

In-process testing helps teams spot these problems much earlier. It gives operators regular data on cell health, contamination, growth, and key process conditions. While in-process testing monitors the manufacturing run, Release testing evaluates the finished product before it moves toward use or distribution.

Why Batch Monitoring Matters

Cell therapy batches can change quickly. Cells grow, consume nutrients, release metabolites, and respond to changes in their surroundings. Genetic modification steps can also create process variations that affect the final product.

Release testing provides the final quality checks needed to determine whether a cell therapy product meets its predefined specifications. In-process testing fills that gap by checking important quality attributes at different stages. This approach helps manufacturing teams answer practical questions such as:

Are the cells growing at the expected rate?
Are the cells still viable and healthy?
Has contamination entered the process?
Are nutrients being consumed normally?
Is the genetic modification step working as planned?
Are process conditions staying within the required range?

Early answers can make a major difference to batch success.

Detecting Contamination Early

Contamination remains one of the biggest concerns in cell therapy manufacturing. Bacteria, fungi, and mycoplasma can damage cell cultures and make a batch unsuitable for further processing.

Traditional sterility methods can take a long time. Rapid testing methods, including qPCR-based approaches, can provide useful contamination data much sooner.

Rapid Sterility Screening

Rapid microbial testing can check samples for signs of bacterial or fungal contamination without waiting for lengthy culture results. This gives manufacturing teams more time to make decisions.

Mycoplasma testing also deserves close attention. Mycoplasma can remain difficult to see during routine culture checks, yet it can affect cell growth and product quality.

Early testing helps teams:

Identify possible contamination sooner.
Isolate affected material.
Stop unsuitable batches from moving ahead.
Reduce wasted media, reagents, labor, and production time.

The value goes beyond saving one batch. Early detection can also help protect equipment, materials, and other manufacturing runs from contamination risks.

Tracking Cell Growth And Viability

Healthy cell growth provides another important signal during manufacturing. Cells need the right environment to maintain their expected growth and function. In-process testing can monitor factors such as pH, nutrient use, metabolites, cell count, and viability. Changes in these measurements may show that the culture is moving away from its expected pattern.

For example, unusual nutrient consumption may indicate that cells are not growing as planned. A change in metabolite levels can also point to stress or altered cell activity.

Watching Cell Health

Cell viability gives teams a direct view of how many cells remain alive and suitable for further processing. Tracking viability over time can reveal a problem before it affects the final cell dose.

Teams can also monitor phenotypic changes. These changes may signal that cells are responding differently to the culture conditions.

When the data shows an issue, operators may review factors such as:

Media composition
Temperature
Feeding schedules
Growth factor levels
Culture conditions

The right response depends on the process and approved manufacturing procedures, but the key advantage remains the same: teams have data early enough to make an informed decision.

Controlling Key Process Parameters

Cell therapy manufacturing involves several steps where process control matters. Genetic modification is one example.

During transduction, teams may monitor indicators such as transduction efficiency and vector copy number. These measurements help show whether the modification step is performing within its expected range.

Real-time or near-real-time data can also support automated process control. When systems receive reliable measurements, they can help operators identify deviations and respond according to established procedures.

This reduces dependence on guesswork. It also creates a clearer record of what happened during the batch.

In-process check	What it can show	Why it matters
Sterility screening	Signs of microbial contamination	Helps stop affected batches early
Mycoplasma testing	Hidden microbial contamination	Protects cell health and product safety
Cell viability	Percentage of living cells	Shows overall cell health
Cell count	Growth and expansion	Helps assess expected yield
pH and metabolites	Changes in culture conditions	Can indicate cell stress
Transduction efficiency	Success of genetic modification	Supports process consistency
Vector copy number	Genetic modification levels	Helps monitor process performance

Reducing Batch-to-Batch Variation

Manufacturing teams want each batch to follow a controlled and repeatable process. In reality, biological systems can vary. In-process testing helps teams understand where that variation occurs. Instead of looking only at the final result, manufacturers can compare data from different stages of production.

This creates a more complete picture of the process. Over time, those records can help teams identify recurring patterns. They may find that certain process conditions often lead to slower growth or lower viability. They can then investigate the cause and make controlled improvements to the process.

Standardized measurements also reduce reliance on subjective observations. Numerical data gives operators clear benchmarks for comparison.

Making Better Decisions During Production

One of the biggest benefits of in-process testing comes down to timing. A problem found at the end of production can mean a major loss of time and materials. A problem found earlier may give the team a chance to respond.

Not every deviation can be corrected. Some batches may need to stop. That decision can still protect resources by preventing more work on a run that cannot meet its requirements. The data can also support decisions around process adjustments, investigation, and batch disposition. Teams can use documented results rather than relying only on observations made during routine operations.

Building A Stronger Testing Strategy

In-process testing works best when it forms part of a wider quality strategy. Testing should match the risks and requirements of the specific cell therapy process.

A practical strategy can include:

Defining critical quality attributes early.
Setting suitable sampling points.
Choosing validated testing methods.
Establishing acceptable ranges for key parameters.
Reviewing results during the manufacturing run.
Documenting deviations and corrective actions.
Using process data to support ongoing improvement.

This approach turns testing into an active part of manufacturing control rather than a final checkpoint.

Prevent Problems Before They Grow

Cell therapy manufacturing depends on healthy cells, controlled conditions, and consistent processes. Problems can develop long before the final product reaches quality control. In-process testing gives manufacturing teams a closer view of what happens throughout the run. It can help identify contamination, changes in viability, unusual growth patterns, and process deviations while there is still an opportunity to respond.

A cell and gene therapy CDMO can help manufacturers build stronger analytical monitoring and make quality decisions faster and more informed.

Strengthen Cell Therapy Manufacturing With Xellera Therapeutics

Reliable cell therapy production starts with knowing what is happening inside the process. Xellera Therapeutics supports the development of advanced solutions for cell and gene therapy manufacturing, with a focus on analytical insight, process control, and product quality.

A stronger in-process testing strategy can help teams detect problems earlier, reduce avoidable batch losses, and build greater consistency into manufacturing operations.

Connect with Xellera Therapeutics to discuss how better in-process monitoring can support your cell therapy manufacturing goals.