Single-use systems (SUS) have become an integral part of modern biopharmaceutical manufacturing. Polymer-based components offer flexibility, reduced cleaning requirements, and faster process changeovers, and are used in many scenarios such as upstream bioreactors, downstream filtration or filling assemblies.
Simultaneously, their extensive use has reinforced the importance of its extractables and leachables (E&L) evaluation. To guarantee product quality, patient safety, and regulatory compliance, it is crucial to understand and manage any chemical interactions between single-use products and production processes.
With the introduction of the new general USP chapters <665> and <1665>, expectations around E&L studies for single-use systems are becoming clearer and more structured. For biologics manufacturers, this represents both a regulatory milestone and an opportunity to strengthen risk-based CMC strategies.
Single-Use Systems in Biopharma: Benefits and E&L Challenges
Single-use technologies are now widely established in biologics manufacturing, supporting flexible facility design, reducing cleaning and cross-contamination risks, and enabling rapid scale-up or multiproduct operations. Across upstream and downstream processing, components such as bags, tubing, connectors, filters, and disposable bioreactors are routinely integrated into manufacturing workflows.
However, unlike traditional stainless steel or glass equipment, single-use components are typically made of complex polymeric materials that can contain additives such as antioxidants, plasticizers, stabilizers, pigments, or processing aids. Depending on the conditions of use, certain substances may migrate from the material into the process stream, with the potential to affect product quality or safety if not properly assessed.
This potential migration is the basis of extractables and leachables concerns:
- Extractables are compounds that can be released from materials under exaggerated or forced conditions.
- Leachables are compounds that actually migrate into the drug substance or drug product under actual process or storage conditions.
In the context of biologics, even low-level impurities can impact critical quality attributes, including stability, safety, and efficacy, making E&L evaluation a key part of process understanding and control.
What are USP <665> and <1665>?
USP chapters <665> and <1665> were developed to address E&L risks associated with plastic components and systems used in pharmaceutical and biopharmaceutical manufacturing.
- USP <665> is a mandatory general chapter that defines standardized approaches for evaluating extractables from plastic components and systems. Its official effective date is 1st of May 2026.
- USP <1665> is a guidance chapter that describes the principles of risk assessment and study design supporting E&L evaluations under <665>.
In practice, <665> defines what must be done, while <1665> explains how to apply these requirements in a scientifically sound and risk-based approach.
Scope of USP <665> and <1665>
USP <665> applies to plastic components and systems that come into direct contact with process streams, intermediates, drug substances, or drug products. Typical examples include:
- Single-use bags and liners
- Filters and filtration assemblies
- Tubing and connectors
- Filling needles and fluid transfer components
- Mixing systems and disposable bioreactors
Items without fluid contact or with negligible exposure are generally outside the scope, reinforcing the importance of process-specific evaluation rather than general or “blanket” testing.
Why This Matters Now
The official effective date is near, and manufacturers are already preparing for inspections and audits aligned with the new chapters. In parallel, global harmonization efforts such as ICH Q3E are shaping future regulatory expectations around E&L. You can read more about the new guideline in our past article on the analysis, study design and ICH Q3E guideline.
These parallel developments point in the same direction: E&L evaluation for single-use systems is moving beyond an optional or case-by-case exercise and is increasingly being integrated as a standard element of biologics CMC strategies.
The Risk-Based Approach in Extractables & Leachables Studies
Extractables studies are designed to generate a chemical profile of potential migrants by exposing materials to selected solvents under controlled, and often exaggerated, conditions. These studies help identify compounds that could become leachables.
Leachables, on the other hand, are evaluated under realistic process or product conditions and represent compounds that actually migrate into the product. As such, they provide direct information on patient-relevant exposure.
USP <665> and <1665> emphasize that extractables data are a tool for risk assessment, not an end in themselves.
Risk Classification Under USP <665>/<1665>
A central element of the USP framework is risk classification, which considers:
- Nature of the material and additives
- Composition of the process stream
- Stage of use (upstream, downstream, filling)
- Contact time and temperature
- Ability of downstream purification steps to remove potential leachables
Based on this assessment, components may be classified as low, medium, or high risk, which directly influences the extent and complexity of analytical testing required.
Rather than applying worst-case testing to every component, the USP approach encourages targeted, science-based studies. This allows manufacturers to focus resources where the potential impact on product quality or patient safety is highest, a particularly important consideration in complex biologics manufacturing processes.
E&L Study Design for Single-Use Systems
A robust E&L program for SUS typically follows a stepwise approach:
- Material and process assessment
Understanding polymer composition, manufacturing processes, and conditions of use, in light of information provided by the manufacturer. - Extractables testing
Using selected solvents and conditions aligned with USP <665> to create representative chemical profiles. - Analytical screening
Applying orthogonal techniques such as GC-MS, LC-MS, and ICP-MS to identify volatile, semi-volatile, non-volatile, and elemental impurities. - Data interpretation and risk evaluation
Assessing findings in the context of process exposure, purification capability, and toxicological relevance.
Where necessary, extractables data may support simulation or leachables studies under process-specific conditions.
Analytical Evaluation Threshold (AET)
Analytical evaluation threshold (AET) is not a fixed value but is based on factors such as process exposure, dose, route of administration and patient safety considerations. As a result, AETs must be interpreted within the context of the specific manufacturing process and product under development.
This reinforces the importance of designing E&L studies that are adapted to the intended use of the single-use system, rather than relying solely on generic acceptance criteria that may not adequately reflect real process conditions.
What This Means for Biologics Manufacturers
For biologics developers and manufacturers, E&L evaluation of single-use systems has direct implications for:
- Process robustness and consistency
- Supplier qualification and material selection
- Regulatory submissions and audit readiness
- Long-term product lifecycle management
Integrating E&L considerations early in development helps reduce the risk of late-stage findings, supports more informed decision-making, and facilitates smoother interactions with regulatory authorities as processes evolve.
How Kymos Approaches E&L for Single-Use Systems
At Kymos, E&L studies for single-use systems are designed with a science-first, risk-based mindset. Each program is personalized to the specific process, material, and regulatory context, rather than following a general approach.
Our capabilities include comprehensive extractables profiling using advanced analytical techniques, combined with structured data interpretation aligned with current regulatory expectations. By integrating E&L studies within broader CMC strategies, we support biologics manufacturers in generating reliable, actionable data that matches regulatory expectations.
Conclusion
As single-use systems play a bigger role in biologics manufacturing, evaluating extractables and leachables is now a key part of quality and compliance. USP <665> and <1665> offer a clear guide for managing these risks with structured, risk-based methods.
By knowing what regulators expect and using science-based E&L strategies, manufacturers can improve process control, aid regulatory submissions, and ultimately guarantee the safety and quality of their products.
If you require assistance with your extractables and leachables studies, or any of your CMC or bioanalytical studies, please do contact us or send us an email to commercial@kymos.com
