Ensuring Drug Product Safety Compliance Strategies Under USP 665 and 1665

This paper aims to open a discussion on the implications of these new rules and the challenges associated with evaluating the impact of plastic materials that may come into direct contact with the product or influence product quality of the drug product during processing. The analysis considers the entire equipment train involved in manufacturing. Packaging materials are not included in this discussion, as they are already addressed by dedicated ISO standards.

Introduction

Almost all process equipment used in the pharmaceutical industry contains some polymeric material that may come into direct contact with the drug product or any intermediate product. Furthermore, single-use systems (SUS) are becoming increasingly integrated into manufacturing processes in the biotech industry.

Guidance documents USP 665, “Plastic Components and Systems Used to Manufacture Pharmaceutical Drug Products and Biopharmaceutical Drug Substances and Products,” and USP 1665, “Characterization and Qualification of Plastic Components and Systems used to Manufacture Pharmaceutical Drug Products and Biopharmaceutical Drug Substances and Products,” have been issued to address a previously unmet need for standardized methods to evaluate the impact of polymeric materials on the quality of drug products. These chapters provide new guidance with a focus on risk-based assessments.

Background

Typical manufacturing workflows consist of multiple production steps necessary to convert raw materials into a pharmaceutical or biopharmaceutical drug substance (DS) or a drug product (DP). Manufacturing processes may expose the final product and its intermediates in possible direct contact with plastic materials, as the equipment may be partially or entirely constructed from polymers. In fact, polymeric materials are widely used in SUSs and piping, and they may contain additives such as antioxidants, stabilizers, lubricants, plasticizers, colorants, and any other component which, when coming in contact with the different materials used in different steps of a manufacturing process, these additives may be released during processing and potentially be present in the final DP impacting its quality and efficacy.

The DP may contain the cumulative sum of the molecules leached from all materials present in the process equipment used throughout manufacturing, unless mitigated by downstream steps such as purification or filtration.

This USP chapter focuses on Process Equipment-Related Leachables (PERLs), defined molecules with the potential to alter critical quality attributes (CQA) and impact the safety, quality, identity, potency and/or purity (SQuIPP) of the DP or DS.

Production intermediates, DS, or DP may come into contact with plastic components present in different manufacturing systems during the manufacturing process. For this reason, USP 1665 contains guidelines for characterizing plastic components used in manufacturing drug products in order to ensure that plastic materials and components do not adversely affect drug product quality or patient safety.

The aim of USP 665 is to evaluate throughout the entire production process―from raw materials to DS and ultimately to DP, any possible PERLs from plastic materials used somewhere along the process. Historically, manufacturers of single-use (SU) components conducted extractables studies and shared results with end users. However, the lack of standardized methods, solvents, and exposure durations made the component selection process challenging for users.

This chapter applies to all DPs, including pharmaceuticals (i.e. traditional small molecules product) and biopharmaceuticals (biologics, defined as products derived through biological processes such as antibody-drug conjugates (ADCs) or recombinant proteins). For biopharmaceuticals, the evaluation is intended to apply to both DS and DP.

Active pharmaceutical ingredients (API) produced via chemical processes, as well as precursors of non-biologic and non-biopharmaceutical DPs, are outside of the scope of this USP chapter.

The types of plastic material included in the evaluation of PERLs are both single-use systems (SUS), meaning manufacturing components designed for one-time use and disposal (such as bioreactors, media bags, tubing, samplers), and multiple-use systems (MUS), such as O-rings, gaskets, and filters. MUS components are intended for reuse following validated cleaning and sterilization procedures.

This chapter should be applied solely to process steps involving liquid or semisolid states, due the inherent tendency of plastic materials to have a greater interaction with materials in liquid or semisolid states compared to solids or gases.

Typical plastic materials that may be present in a pharmaceutical and biopharmaceutical processes are presented in Table 1 of the chapter, where they are divided into materials having different interaction timing:

• Short-time contact, simulated by a worst-case extraction time of –24 hours ± 1 hour
• Medium-time contact, requiring –168 hours (7 days) ± 4 hours

Long-time contact, requiring 504 hours (21 days) ± 8 hours. Among examples of components listed in the table for short-duration contact include chromatographic column housing, non-storage containers such as mixing bags, bioreactors, filters, filtration cassettes and other items commonly found in modern manufacturing facilities.

USP 1665 offers a detailed rationale for the scope and use of this chapter and provides additional information and guidance regarding the application and applicability of USP 665.

Among the materials considered to have short interaction times include small components such as O-rings, gaskets, and diaphragms. The evaluation of these components, however, is excluded in this chapter if they are constructed from rubber–based elastomers. In such cases, their evaluation, in terms of test method and specification, should follow the guidance provided in USP 381, “Elastomeric Components in Injectable Pharmaceutical Product Packaging/Delivery Systems.”

Additional exclusions apply to plastic auxiliary items such as scoops, funnels, pipettes, and other components whose limited contact with the product, or whose material state, poses minimal risk of contributing PERLs to the process stream. Therefore, these items are not covered by this chapter.

USP 1665 offers a detailed rationale for the scope and use of this chapter and provides additional information and guidance regarding the application and applicability of USP 665.

The testing described herein applies to components and systems that have not yet been qualified, as well as to previously qualified components whose usage conditions have changed.

Both USP c chapters clearly indicate the principle that the component user bears the responsibility to establish and justify how this c chapter should be applied to specific actions and to justify its relevance to the particular process stream used in pharmaceutical and/or biopharmaceutical manufacturing processes.

It is important to emphasize that USP General chapter 1665 is informational and does not constitute a statement of requirements. In contrast, USP 665 will become official on 1 May 2026, and will define requirements for products manufactured or marketed in the United States.

Figure 1: This decision-making flowchart outlines a structured three-step process to determine whether a component used in pharmaceutical or biopharmaceutical manufacturing requires testing. The evaluation considers the component’s isolation from the process stream, its contact with liquid or semi-solid materials, and its equivalence to previously qualified components. Components deemed in scope and lacking established equivalence must undergo a risk assessment to evaluate potential impacts on drug product quality and patient safety.

USP 665 qualification process

Qualification testing of a component or system is necessary to demonstrate its suitability to produce an acceptable DS or DP. When appropriate, system qualification may be augmented by DS or DP testing to directly assess the impact of the manufacturing system on the product’s key quality attributes.

The qualification process foresees a two-step approach:

1. Initial assessment of the plastic material
2. Risk assessment to determine the potential impact of PERLs that could adversely affect the quality of the DP, and to define the appropriate level of testing and evaluation for intermediates, DS, and DP.

The most effective way to ensure that a system is suitable for its intended use is to have well-characterized components constructed from rationally selected materials. This can be obtained by material and component characterization, which supports and justifies the selection process.

Qualification of plastic manufacturing components and systems involves:

• Component or system characterization by chemical testing (i.e., extractables profiling)
• Interpretation of test results to assess suitability for use, including toxicology evaluation

The initial assessment determines whether component testing is necessary. If so, a subsequent risk assessment should be conducted to define the appropriate level of testing based on the potential impact of PERLs on the quality of intermediates, DS, or DP.

Figure 2: Testing requirements based on the results of component risk assessment.

Figure 3: Testing solution selection based on the results of the risk assessment.

Initial Assessment of Manufacturing System

This assessment evaluates the system’s suitability for its intended use without chemical characterization. The approach is schematically represented in the following flowchart.

The final step of the assessment addresses the equivalence of a manufacturing system with a previously qualified component or system.

Such equivalence is established based on the following criteria:

• Materials of construction have the same composition and are manufactured using similar processes
• Vendor preparation for use is performed in the same manner
• Design equivalence is maintained
• Functional equivalence in the performance is demonstrated
• User preparation for use is conducted in the same manner
• Conditions of use within the manufacturing process are equivalent
• An equivalent DS or DP with same composition and clinical application is used in manufacturing

While it is ideal for all seven criteria of equivalence to be fulfilled, essential equivalence may still be established based on the strong similarities between the component under evaluation and comparator. In this last case, the minor differences should be addressed through a risk-assessment approach.

The responsibility establishing and justifying equivalence to a comparator lies in the hands of the component user.

If no suitable comparator is present, or if equivalence cannot be demonstrated, the component must be characterized using a risk-based approach.

Risk Assessment

Component testing is conducted to evaluate the suitability of the component for its intended use. This assessment is based on the chemical and/or biological effects attributed to PERLs. The greater the risk of component unsuitability, the more extensive the degree of required testing will be.

Risk assessment is conducted using a risk evaluation matrix, which defines the dimensions of risk and enables quantification of individual risk factors. This approach facilitates the calculation of total risk and links the outcome to the appropriate level of characterization testing.

• The risk assessment must consider a range of factors that influence the likelihood of leaching and the persistence of leachables. A robust evaluation of PERLs should address, at minimum, the following considerations:
• The chemical and physical nature of the contacted component, to establish its propensity for leaching
• The chemical nature of the process stream, to assess its potential to extract leachables
• The capability of downstream processing steps to eliminate, remove, or clear PERLs from the process stream, or to dilute the PERL to assess the unlikelihood of an adverse effect
• Inherent risk associated with the manufactured DP, considering route of administration, clinical dosage, and duration of standard clinical therapy

The outcome of the risk assessment is categorized as low, moderate, or high risk, and the extent of testing required for the component is determined accordingly. This correlation between risk level and testing requirements it outlined in Table 2 of USP 665 and schematically represented in Figure 2.

Standard Procedure and Extraction Solutions

USP 665 clearly defines conditions, solutions, and procedures to be followed for measuring potential leachables originating plastic components used in DS and/or DP manufacturing systems.

Standard Solutions

The three standard extraction solutions specified in chapter USP 665 are designed to simulate worst-case scenarios across a range of manufacturing conditions. These solutions are used for organic, acidic, and basic extraction studies during the evaluation of PERLs in plastic manufacturing components:

• Solution C1: Organic Extraction

A 50% ethanol/purified water solution used to simulate exposure to organic solvents, solubilizers, lipids, proteins, blood-derived components, and a broad range of organic and biological substances.

• Solution C2: Acidic Extraction
• A pH 3 salt solution) used to simulate low pH conditions, applicable to acidic process streams.
• Solution C3: Basic Extraction

A pH 10 buffer solution used to simulate high pH (alkaline) conditions. This solution is not interchangeable with more caustic solutions such as 0.5 N sodium hydroxide. Chapter 4.2.1 of USP 665 provides detailed instructions for the preparation of the above-mentioned standard solutions, or possible acceptable alternatives to be used in leachable studies.

For more effective testing of plastic components, pre-conditioning or processing is necessary in accordance with the manufacturer’s instructions and intended use. This may include, for example, irradiation or steam sterilization.

Extraction Process

The standard extraction process should be dynamic, simulating real manufacturing conditions.

The extraction process outlined in USP 665 is designed to establish a standard extraction protocol that balances completeness and practicality, in order to ensure that the extracts provide meaningful data for component qualification in manufacturing systems.

These protocols should be applied in components and systems used in diverse manufacturing environments and in many different and varying conditions, depending on the product and process in scope.

If the test conditions have open access, and therefore a loss in the standard solution is possible, a necessary remedy should be found in order to maintain and control the possible loss in extraction volume.

Extraction blanks—ions of the extraction solution not in contact with the test article―should be generated and tested to identify any chemical extracts from analytical artifacts.

When designing the extraction testing, it is essential to ensure that sufficient extract volume is available to support all required testing.

Some specific cases are provided describing procedures to be applied in different cases, such as extraction of aseptic connectors or disconnectors, bags, and other specific components.

In Section 4.2.2 of USP chapter 665 all details regarding the extraction process and specific case applications are reported and described.

Extract Testing

Extract testing is broadly divided into two categories depending on the aim of testing: chemical and biological testing.

Chemical testing can be supported in the following approaches:

• Extractables testing: identifies potential chemical substances that may leach from plastic components into the drug product under exaggerated conditions.
• Leachable testing: Detects and quantifies chemical substances that actually migrate into the drug product under normal storage and use conditions.

Biological testing, on the other hand, evaluates the potential health impact of leachables on the health of patients. They can be grouped as follows:

• Cytotoxicity testing: Conducted to determine if leachables from plastic components are toxic to cells or inhibit cell growth.
• Hemocompatibility testing: Performed to assess the interaction of leachables with blood products.

The most commonly employed chemical tests include:

• Non-Volatile Residue (NVR) testing: Utilizes extraction solution C1 associated with extraction blanks. Acceptance criteria for NVR result should comply with USP chapter 1665 .
• Ultraviolet (UV) absorbance: Also uses extraction solution C1 associated and extraction blanks. The differential UV absorbance must meet the acceptance criteria outlined in USP chapter 1665.
• Organic extractable profiling: Recommended when a moderate risk assessment outcome is identified. In such cases, both extracts and extraction blanks should be analytically tested.

For organic extractables, orthogonal chromatographic methods should be employed to estimate their presence and concentration. Extractables must be reported in accordance with USP chapter 1663 , considering the limits of detection (LoD) and quantitation (LoQ). Acceptance criteria should be defined based on safety and/or product quality risks, supported by toxicological assessments of individual extractables.

Alternative Extraction Approaches

USP chapter 665 provides flexibility for the qualification of plastic components used in pharmaceutical manufacturing. Alternative qualification procedures can be employed based on a thorough risk assessment and by providing a proper justification.

This flexibility allows for the adaptation of qualification procedures according to the specific risk profile of the component. It includes the use of existing data from previous qualifications or from similar components to support the qualification process, and requalification processes for components that undergo significant changes.

The following studies are permitted and recommended:

• Comparative studies: To demonstrate equivalence between a new or modified component and an already qualified comparator component.
• In silico models: To predict the behavior and interaction of leachables with the drug product using computational models.
• Bridging studies: To bridge data from existing studies to the new component, minimizing the need for extensive new testing.

It must be stressed that all the studies must be executed, reported, and archived by complying with Good Manufacturing Practice (GMP) requirements to ensure that alternative qualification procedures meet regulatory requirements and guidelines.

USP chapter 1665: Technical Guidance and Standard Procedures

USP 1665 provides foundational concepts and detailed guidance on the applicability and implementation of chapter <665>. It outlines qualification procedures for manufacturing components and systems within its scope.

The chapter aims to detail and document the technical procedures required to ensure that plastic components used in manufacturing systems do not release PERLs at concentrations that could pose risks to patient safety.

For non-metallic or non-glass materials, two other USP chapters should be considered: 338, concerning elastomeric materials, and 661.1, concerning a more general part related to plastic materials.

This chapter provides a detailed description of the procedures and considerations involved in the evaluation and initial assessment of plastic components used in pharmaceutical manufacturing. It offers guidance on the characteristics of extraction protocols and the type of studies to be performed, depending on the manufacturing system, process, and product in scope. It also gives guidance on analytical method techniques and acceptance criteria limits.

As an example, with respect to the extraction protocol, some limits are clearly stated:

• A maximum temperature of 40°C, which is considered the optimum in order to accelerate the extraction process without significantly altering the nature of the component.
• The duration, which is stated from a minimum of 1 day up to a maximum of 21 days to reflect both short-term and long-term contact conditions.

The level of details given should then be adapted to the specific case and used as a guideline in performing the assessment and the studies needed.

Conclusion

The requests and activities described in this article pose an important effort in all DP and/or DS manufacturing facilities, particularly considering that many new manufacturing facilities have been designed primarily around single-use systems (SUS).

USP chapter 665,which becomes a requirement on 1 May 2026, relies on the direction outlined in USP chapter 1665. Both chapters stress that the ultimate responsibility for assessing the potential impact of leachables from plastic materials present in manufacturing systems on the final product, is the responsibility of the final user (meaning the DP and/or DS manufacturer).

To meet these requirements , it will be necessary to first map the process, particularly the manufacturing systems in place and their association with specific process steps for the DP and/or DS in scope. Subsequently, an analysis of plastic components used manufacturing systems should be conducted based on available information from the provider or for use in other context. Consideration should also be given to the presence of identical systems operating under different conditions or in various parts of the facility, as this may influence the scope and prioritization of testing.

Once the test and parts are defined through a risk-based scientifically sound assessment, the parts involved should be considered as possible comparators for other manufacturing systems in the facilities, in case the process and product characteristics can be considered comparable.

Throughout this process, the primary importance should be the safety of the patient. The central challenge lies in understanding the types and concentrations of PERLs that may be present in the final product, and in correctly assessing the real toxicological impact on the patient.1^, 2