Extractables & Leachables: What's the Difference? How to Deal with It?

With the integration of single-use systems (SUS) into downstream processing, which brings them closer to the final drug product, consideration of extractables and leachables (E&L) has become a key issue within the industry. However, the lack of relevant standardization has resulted in incomplete E&L studies that do not cover the conditions encountered throughout the process. This makes it difficult for end users to choose suitable single-use components.

The challenges faced by the pharmaceutical industry are:

● Prevent misunderstandings of regulatory requirements for E&L, as they are also used for finished containers, applying them to processing contact materials

● Bridging the gap between end-user expectations and supplier capabilities by defining the limits of responsibility and scope of operation for both

This article is to clarify and emphasize the importance of distinguishing extractables and leachables when evaluating SUS using risk management and quality by design (QBD) methods, and to support one-time development and market promotion.

This article introduces a risk-based approach to evaluating E&L for SUS. In fact, although the foundation of such regulations already exists, regulations for single-use technology (SUT) do not yet exist. For example, in the United States, 21 CFR 211.65 stipulates that "the construction of the device should be such that the surfaces that come into contact with components, processing materials, or drugs should not have reactivity, additives, or absorptivity that could alter the safety, identity, strength, quality, or purity of the drug beyond official or other established requirements.

Two terms, two perspectives

SUT has been part of the biopharmaceutical industry for about a decade. Since terminology is a key element in preparing for and understanding any new field, it is crucial to define commonly used terms and use them correctly.

Many people use the term "extractables and leachables" as a single term, but these concepts reflect two distinct chemical substances, although both are migrating from components.

Extractables are compounds that migrate from SUS to model solvent solutions under controlled and exaggerated conditions, depending on temperature, pH, polarity, and time. SUS is typically not exposed to these conditions during biopharmaceutical processes.

Leachables are compounds that migrate from SUS to the process solution under normal biopharmaceutical process conditions; they may ultimately appear in the final drug formulation. In most cases, leachables are a subset of extractables, although interactions with product components may result in leachables that are not considered extractables.

The purpose of extractables and leachables research is different: extractables research aims to obtain fingerprint profiles of chemical components that can be extracted under exaggerated conditions. A toxicological review of these fingerprint profiles, together with risk assessment of potential problematic components, can help to select suitable SUS. Extractables research can also serve as a baseline to ensure the consistency of SUS over time.

Leachables research identifies compounds that migrate from SUS into the process solution and characterizes possible adsorption and/or absorption of process fluids under normal process conditions. These data enable toxicologists to determine whether there are components in the drug product that may pose a risk to patient safety. Additionally, leachables data can indicate the presence of chemical components that may interact with the drug itself, and help assess the potential for changes in drug potency and/or stability. As leaching can continue over time, posing risks to patient safety and drug efficacy, leachables may also be present in stability studies.

These definitions, especially for extractables, are not entirely balanced. It is essential to categorize different applications and conditions within the biomanufacturing process to highlight the weight and criticality of the E&L profile in product contact materials.

Regulatory agencies expect that the final dosage form will have defined degradation characteristics, including leachables from process contact materials, even if they do not pose any significant health risk to patients. As part of this profile, there must be targeted evaluation and mitigation of E&L. Due to the number of parameters that can affect E&L assessment and the need for trace level analysis, this is challenging.

Collaboration and clear role definition among SUS manufacturers, suppliers and end-users (drug manufacturers) are crucial to ensure patient safety and product efficacy, even for transportation and storage of single-use components prior to their use in pharmaceutical production.

The simplest way to determine responsibility is through establishing clear communication and transparent document exchange (certificates, reports, conclusions, minutes of decision-making meetings, and any legal agreements). Tools like the RACI (Responsible, Accountable, Consulted, Informed) responsibility allocation matrix can be used to identify stakeholder responsibilities.

*Pre-sterilized products, equipment, and packaging are designed for use once or a few times, depending on the specific situation, and then discarded.

Risk-based Approach

It is necessary to establish a risk assessment for extractables and leachables at different stages of SUS production and drug development to balance business risks and patient safety. Business risks must be considered, but at no point should patient safety be compromised. There is a considerable correlation between the extractables analysis costs of suppliers and the user requirements specifications (URS) of end-users, as well as the feasibility of conducting more complex extractables research.

Both end-users and suppliers have a stake in business impact analysis. Ultimately, the main consideration must be on product quality and safety, which should be assessed through appropriate risk assessment and mitigation strategies such as quality risk management. The amount (and location) of leachables per unit of the final drug dosage form is the ultimate regulatory expectation. End-users must comply with this patient risk management method as required by regulatory agencies.

 QBD Approach

The E&L plan should be based on QBD (Quality by Design) principles and a thorough understanding of the biomanufacturing process. Using this approach, suppliers should conduct E&L studies on SUS based on baseline safety assessments and chemical research, covering the process from raw material procurement to disposal, including critical process points such as sterilization. End-users should first assess the importance of SUS components in terms of process flow based on the documentation provided by the supplier.

Chemical fingerprint analysis ensures that no toxic substances are found (or are well below limit values) and that the product is unlikely to interact with the final drug. Informed material selection needs to be made with reference to extraction studies, meeting regulatory expectations, evaluating material safety, and controlling the absorbed leachables in the final dosage form to guarantee drug safety and purity requirements.

Many people use "extractables and leachables" as a single term, but these two concepts reflect two distinct types of chemical substances, albeit both migrating from components.

Assessment Method for Extractables

Prior to conducting extractables studies on SUS in processing, end-users should assess single-use material attributes in their risk assessment approach, including dosage form, formulation components, intended use, and stability, while considering the intended use and process conditions of SUS    components. Experimental design should consider several factors that may affect the quality of extraction and result analysis (Figure 1):

● Selection of model solvents

● Surface area to volume ratio

● Mass of each extractable or leachable per volume of model solvent

● Extraction time points

● Types of materials tested

● Relevant structural and physical characteristics: SUT resins, films, components, assemblies, and systems

Various extraction techniques and solvents of various polarities should be used to test components based on various target species and formulations. Because "maximum" does not mean "better", during the extraction process of contact materials, the maximum quantity of compounds (contact time, solvent concentration, extraction kinetics) should not be expected, but appropriate extraction conditions and analytical methods should be selected to predict the leachables produced in specific applications. Then, the extracts should be evaluated using analytical techniques based on sensitivity, detection limits, and target substance characteristics (considering first volatiles, semi-volatiles, or non-volatiles).

After toxicology analysis, the potential toxicity and safe threshold of extractables can be identified and evaluated. If potential toxicity is detected, the end-user should report the results to the supplier and stop using the tested SUS components until a risk mitigation strategy is developed. Suppliers should follow common extraction methods based on all industry-accepted standards, and communication with end-users must be based on mutually agreed reporting methods.

Figure 1: Accurate, efficient, and appropriate extraction of Ishikawa diagrams

Figure 2: E&L's SUS qualification requirements based on risk level

Assessment Method for Extractables:

The evaluation of SUS leachables should be based on a risk- and science-based approach to ensure the safety and purity of the final drug product. Process knowledge, experience gained during development, and comprehensive process understanding should be used to evaluate and implement risk management related to SUS. Risk management principles can identify, assess, communicate, and mitigate leachables that may affect product quality and patient safety. Leachable curves should be used to determine the residual chemical properties of SUS under normal process conditions and the toxicological impact on drug and patient safety. If leachable materials have adverse effects on key quality attributes, such as the purity, safety, efficacy, characteristics, strength, or successful production of final and/or intermediate products, then the use of such materials is not recommended.

The risk may be based on the severity of the harm caused by the SUS leachate, the likelihood of leaching occurring, and the possibility of detecting leached substances through manufacturing control and testing during the process. Once the final risk rating (low, medium, or high) is determined for the single-use component of interest, qualification requirements should be established to confirm the intended use of the single-use component (Figure 2).

It is recommended to adopt a case-by-case approach to determine which extractables should be analyzed in the leachable study. For medium and higher-rated risks, the evaluation of specific products should be based on extractable data and conducted under the supervision of toxicologists. Given the high-quality data applicable to the end-user biological process, the extractable data can guide and define the depth of the leachable study. In addition, the end-user should consider that leachables can also originate from interactions between extractables and drug formulation compounds.

Conclusion

One key advantage of implementing this approach for process contact materials is that it allows for the identification of locations where leachable studies are required and focuses efforts based on leaching tendencies. Quality by Design (QbD) risk assessments and collaborative efforts between suppliers and end-users are key principles that should facilitate the implementation of SUS through a better understanding of industry expectations from suppliers. This drives consistency in study design, allows for the integration of data from multiple suppliers, and facilitates evaluation and comparison between components.

The manufacturing of single-use supplies for biopharmaceutical production requires rigorous design, with functions and appearance adapted to their intended uses. After the design is completed, strict material selection is conducted, and the selection of materials is crucial in the biopharmaceutical industry. Material selection must consider the E&L of the materials, which determines whether the final product can be used normally. If the manufacturing material affects the progress of the biopharmaceutical manufacturing process, then this material is not suitable. After selecting the corresponding manufacturing materials, the manufactured products also need to undergo various correlation validations, risk assessments, and confirmation that the relevant products meet the requirements and can be normally applied in biopharmaceutical production processes.

BioLink's products cover a wide range of biopharmaceutical production processes and meet the needs of each process. This time, we will introduce the consumables required in the upstream of cell culture.

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Quoting

• 1 U.S. Food and Drug Administration. Title 21, Code of Federal Regulations, Subchapter C, Part 211, Subpart D, Section 211.65, "Manufacture of Devices."

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A variety of BioLink single-use consumables

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