Single-use products have been used in pharmaceutical manufacturing since the 1990s when plastic filters and tubing were integrated with stainless steel bioreactors. Back then, cleaning and preparing steel containers for reuse was inefficient, time-consuming and costly. But a shift to disposable, single-use systems (SUSs) has revolutionized biomanufacturing.

Today, most drugs are developed using plastic bags, tubing, bottles, connectors, pumps, sensors, filters, valves, etc. With the advent of plastic SUSs, product quality has improved, operations have become more streamlined, and production costs have decreased. Using SUSs also alleviates the extra steps to validate contact materials’ cleaning processes, significantly minimizes downtime and allows for easier scale-ups. Single-use manufacturing plants require less time to achieve full production capacity than their stainless-steel counterparts.

All of this is not to say that SUSs are perfect systems. While they are cost-effective and produce high-quality pharmaceuticals, they come with challenges inherent in using plastic materials.

Begin with extractable/leachable testing

Chemicals within plastic components can leach out and inhibit cell growth, have mutagenic or carcinogenic impacts, interact with pharmaceutical ingredients, and block a biologic’s desired effect. Even commonly used materials or those with a long history of clinical use can contain uncommon levels of residual chemicals and chemicals of concern. One example of a “common” material that contains potentially dangerous chemicals is polypropylene.

Polypropylene is approved by the U.S. FDA and used in more than 170 health care products including, sutures, mesh, cardiovascular patches, packaging and SUSs. The list of extractables associated with polypropylene materials contains around 35 chemicals and, at elevated levels, some of them can be very dangerous.¹ For example, benzopyrene features heavily in polypropylene but is known to cause cell mutations (i.e., tumors) and various forms of cancer. Extractables/leachables studies are conducted to identify these risks.

Extractables are determined through the interaction of the SUS and aggressive solvents under exaggerated conditions to generate “worst-case” data. Leachables, on the other hand, come from direct contact between drugs (or a surrogate drug product) and the SUS under more clinically relevant or “normal” conditions. To identify risk, drug manufacturers must fully understand the materials and manufacturing process for each SUS. When it comes to SUSs, not all plastic is created equal. Drug manufacturers should consider the type of plastics used, the contact duration and temperature, and proximity to the final drug product to assess risk. Components with the highest risk of leaching chemicals during the manufacturing process should be tested to confirm the potential hazards. 

Analytical chemistry for E/L

The materials and manufacturing process can also help scientists identify the appropriate analytical equipment to choose and provide information to assist in the proper identification of extractables/leachables detected. 

A SUS supplier may provide extractables information, but leachables data is still needed to fully support safety. The revised BPOG protocol encourages manufacturers to provide available data on their materials and, in doing so, effectively vets vendors whose materials contain objectionable extractable data. But manufacturers are still responsible for ensuring the absence of any chemicals of concern that may leach out and affect patient safety, as a result of manufacturing their product. 

Generally, multiple analytical techniques are used to uncover the full range of extracted chemicals associated with a SUS, including inorganic and organic compounds. Commonly used analytical methods include:

• Inductively Coupled Plasma (ICP). Used to detect and identify elements/metals. The analysis of ICP-MS is relatively straightforward as it consists of a relatively small number of well-characterized elements on the periodic table.
• Headspace Gas Chromatography-Mass Spectrometry (HSGC-MS). Used to detect volatile compounds; analysis is aided by the availability of commercial databases.
• Gas Chromatography-Mass Spectrometry (GC-MS). Used to detect semi-volatile compounds, which also leverage the same commercial databases, but this can provide a false sense of security if the scientist doesn’t take the time to ensure the most probable identification given by the database makes sense for the material.
• Liquid Chromatography-Mass Spectrometry (LC-MS). Used to detect semi to non-volatile compounds and is very challenging and resource-intensive given that there are no commercial databases available for these compounds. Laboratories must develop their internal databases and commit significant time and resources to have internal experts knowledgeable in compound elucidation.

Common shortcuts could mean trouble for manufacturers

While many laboratories promote their extractables/leachables capabilities, reporting from labs can differ significantly. A commitment to identifying all compounds is not part of an E/L program for some laboratories. If identification is an additional service, it is essential to understand the extent of identifying compounds. Will identification be made using commercial databases? What about LC-MS, and how will identification be accomplished? And how often are unknowns reported?

Unknowns are unacceptable when your goal is to identify all the potential patient hazards. Complete identification is possible, but it takes a laboratory partner who is committed and willing to invest the resources needed. Thoroughly vetting your laboratory partner before your program commences is the best way to avoid surprises and delays in your timelines.

Follow up with a safety assessment/toxicological risk assessment

A SUS’s safety and effectiveness—not to mention its regulatory success—will depend on collaboration with biomanufacturers, chemists and toxicologists to mitigate overall risk.

A thorough safety assessment/toxicological risk assessment will evaluate all of the compounds detected in your chemistry report. Compounds that cannot be identified, reported as unknown, must be assessed at the most conservative level of risk, often leading to a margin of safety (MOS) less than 1 (i.e., estimated exposure exceeds a tolerable intake) and could require additional measures to mitigate the potential safety risk. If unknowns cannot be identified or if compounds with potential risk cannot be mitigated, an alternative SUS may be a last resort. 

The regulatory expectation

Thus far, most regulatory bodies are asking to see E/L data and may ask for a safety assessment/toxicological risk assessment to accompany that data. China already requires E/L testing for SUSs. In the EU, the European Medicines Agency (EMA) and International Council on Harmonization (ICH) have alluded to the importance of—and have begun to expect—E/L testing on SUSs. The ICH Q7 guidance on good manufacturing practices (GMP) for active pharmaceutical ingredients clarifies the EMA’s stance on E/L testing.

In the absence of formal regulations, the BioPhorum Operations Group (BPOG) sought to provide some guidance in 2014 when it published the first standardized extractable protocol, commonly referred to as “the BPOG protocol.” BPOG’s protocol is based on the extraction capabilities of various solvents over recommended time points. The protocol suggests methods for extractables studies, including sample preparation, extraction conditions, recording test article sample conditions, and reporting data from the analysis of extracts. Its goal is to prepare biomanufacturers’ products for regulatory submission. In 2020, the group published a revised extractables testing protocol based on what it learned from data generated under the original protocol. 

Back in 2010, the U.S. Code of Federal Regulations (CRF 211.65) decreed that all equipment with surfaces that contact components, in-process materials or drug products “shall not be reactive, additive or absorptive so as to alter the safety, identity, strength, quality or purity of the drug product beyond official or established requirements.” And more recently, the U.S. Pharmacopeia (USP) issued two new chapters (665/1665) on production equipment and patient safety for polymeric components and systems used in biomanufacturing. The new USP chapters provide information to assess risk and a standardized testing procedure.

• USP discusses the characterization of plastic components and systems used to manufacture biopharmaceutical drug substances and biopharmaceutical and pharmaceutical drug products. This chapter became official on May 1, 2022, but is only applicable when supporting accepted standards by recognized regulatory bodies.
• USP discusses the selection and qualifications of plastic components and systems used to manufacture active pharmaceutical ingredients, biopharmaceutical drug substances, and biopharmaceutical and pharmaceutical drug products.

USP is considered harmonized with BPOG’s 2020 revised guidance, meaning manufacturers that have collected data using the BPOG protocol have likely met the requirements of USP . Manufacturers who are preparing to conduct testing can meet the requirements of the 2020 BPOG protocol as well as USP . The USP chapters are a step forward in finalizing and clarifying regulators’ expectations around fluid-contact equipment in biomanufacturing. The risk-based approach also helps manufacturers prioritize which data they need to present to achieve regulatory success.

With the new USP general chapters, regulatory bodies have the prerogative to ask manufacturers to provide whatever data they would like to see. But neither the new USP chapters nor BPOG protocol are enforceable. As it is currently published, USP is solely informational—it simply signals the importance of E/L data.

According to USP, the chapter will not become compendially applicable (i.e., a required standard) until it is referenced in a USP monograph, referenced in another applicable general chapter below 1000, or referenced in the General Notices. If the applicability of changes, USP will monitor harmonization efforts (ICH Q3) and engage stakeholders to develop and define implementation strategies. 

The bottom line is that biomanufacturers should expect to show extractable/leachable data and potentially safety assessment for high-risk SUSs used during pharmaceutical manufacturing.

A final word

Given the rapid, industry-wide shift toward SUSs and the potential risks of leachable contamination, everyone involved is working quickly to refine processes and align expectations. Advanced chemical and toxicological capabilities combined with open communication between biomanufacturers and regulators are the cornerstones of building a safe and effective SUS.

Biomanufacturers interested in using SUSs must be aware that they need to assess the risk of using SUS and be able to mitigate these risks with analytical chemistry to identify real hazards and a gap analysis to identify what is needed to assess risk accurately. These are the foundational pieces of the risk-based approach and may eventually be regulators’ expectations worldwide. Manufacturers will benefit significantly from collaboration with a laboratory testing partner who can design studies and conduct testing to achieve these goals. 

References

1. Jenke, D. Compatibility of Pharmaceutical Products and Contact Materials: Safety Considerations Associated with Extractables & Leachables, October 2008. Print ISBN: 9780470281765 | Online ISBN: 9780470459416

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Sandi Schaible is the senior director of analytical chemistry and regulatory toxicology at WuXi AppTec Medical Device Testing, located in St. Paul, MN, specializing in extractables and leachables studies. She is a U.S. delegate and international delegate for ISO 10993 part 18 in chemical characterization, and also a U.S. delegate for ISO 10993 part 13 and the particulates committee (TIR42).