Identifying Critical Quality Attributes in Drug Products: Your Key to Ensuring Safe and Effective Therapeutics

In drug manufacturing, there is no room for error. Every decision, from early formulation to final release, must ensure a product is safe, effective, and consistent.

At the center of this process are critical quality attributes (CQAs), the measurable properties that define whether a drug meets its required standards.

In this blog, we break down the role of CQAs in biologics development and how advanced particle analysis is enabling deeper insight, earlier decisions, and continuity from development through QC.

What are critical quality attributes?

A CQA is any physical, chemical, biological, or microbiological property that must remain within a defined range to ensure product quality.

CQAs typically fall into three categories: 

• Physical characteristics: these include aspects such as the size and shape of the pharmaceutical product 
• Chemical properties: these encompass elements like the pH level and concentration of the drug 
• Biological attributes: these involve factors such as sterility and bioburden levels in the product 

The process of identifying CQAs is an essential step in the drug development process as it ensures that the final drug product is consistent, effective, and safe for patient use.² Any deviation can influence the efficacy of a drug, potentially leading to harmful effects on the patient. 

Moreover, the recognition of CQAs is not just a best practice; it’s a regulatory mandate. Regulatory authorities, including the FDA and the European Medicines Agency (EMA), require the identification of CQAsas part of the drug development process.³ This ensures that drug products meet the necessary quality standards and are safe for consumption.⁴ 

CQAs and Quality by Design

CQAs are foundational to Quality by Design (QbD), a framework that emphasizes building quality into a product from the start, rather than testing for it at the end.

QbD relies on deep process understanding, identification of risk factors, and control strategies tied directly to CQAs. In practice, this means CQAs must be measured accurately, consistently, and across every stage of development, not just at release.

The Challenge: Subvisible Particles as a Critical CQA

One of the most challenging CQAs in biologics is subvisible particles.

These particles often fall in the ≥10-µm range and can:

• Reduce stability and shorten shelf life
• Trigger immune responses or adverse events

Because of this, they are closely monitored throughout development and in QC environments. Subvisible particle analysis is also central to meeting compendial requirements, such as USP <788> and USP <789>, which define limits for particulate matter in injectable drug products and set expectations for particle counting and size classification.

Despite their importance, traditional methods have struggled to provide actionable insight, especially in early-stage, low-volume conditions. This creates a gap across the workflow, with limited insight into development, different methods required in QC, and disconnected datasets across the product lifecycle.

Closing the Gap with Advanced Particle Analysis

The Aura Particle Analysis System addresses this gap by enabling high-resolution particle characterization from development to QC across various therapies – including biologics, AAVs, LNPs, and cell therapies.

Using Backgrounded Membrane Imaging (BMI) and Fluorescence Membrane Microscopy (FMM), Aura delivers precise particle count, size distribution, morphology, and particle identification.

Importantly, Aura supports both:

• Small-volume analysis with as little as 5 µL for early-stage work
• Large-volume workflows supporting over 500 µL per sample to align with QC expectations

This allows teams to generate meaningful CQA data earlier, maintain one method across stages, and build a continuous dataset from formulation through release.

A More Complete View of CQAs

By providing deeper visibility into subvisible particles, one of the most complex CQAs, the Aura System enables earlier detection of instability or aggregation, better differentiation between particle types, and more informed decision-making throughout development.

Instead of reacting to CQA failures late, teams can design around them from the start.

Conclusion

CQAs are the foundation of drug quality, but their value depends on how well they are understood and controlled.

As biologics grow more complex, the need for technologies that can deliver accurate, consistent, and stage-spanning insight continues to increase.

With advanced particle analysis, it is now possible to move from fragmented workflows to a single, continuous understanding of CQAs across the development process.

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4070262/#CR3 

2. https://www.linkedin.com/pulse/benefits-identifying-critical-quality-attributes-cqas-mo-heidaran-2e/ 

3. S. Department of Health and Human Services, Food and Drug Administration, Center for Drug Evaluation and Research (CDER). Guidance for Industry: Q8(R2) Pharmaceutical Development. November 2009. 

4. https://www.roosterbio.com/blog/critical-quality-attributes-cqas-know-their-importance-limitations-in-product-process-development/