Championing In Vitro Biocompatibility/Biological Reactivity Testing for Plastics Used in Pharma Manufacturing

Championing In Vitro Biocompatibility/Biological Reactivity Testing for Plastics Used in Pharma Manufacturing

June 21, 2021PAO-06-21-CL-09

Animal testing became the standard for assessing the biocompatibility and bioreactivity of filters and single-use components, even though it has never been a regulatory requirement. In fact, in vitro cytotoxicity testing has been shown to be more reliable, but many companies remain entrenched in this old paradigm. It is time for the industry to update its procedures to avoid archaic and unnecessary animal testing in this context.

Why Animal Testing in the First Place?

As long ago as 1960, it was recognized that the use of plastic material in pharmaceuticals presents certain risk factors that could impact patient health. In 1965, the United States Pharmacopoeia published USP XVIII, which included biological tests (systemic injection, intra-cutaneous, and implantation) for plastic containers, with plastics assigned Classes I–VI according to the severity of in vivo testing required. When USP adopted the chapter numbering system in 1975, the chapter was renamed Biological Reactivity Tests, In Vivo <88>.

By 1988, USP had explored in vitro tests and concluded that such assays could serve as a decision point in determining whether samples would need to be tested in animals. In 1990, the chapter Biological Reactivity Tests, In Vitro <87> was added to the compendia (USP XX/I). The companion chapter The Biocompatibility of Materials Used in Drug Containers, Medical Devices and Implants (1031) provided guidance based on the route of administration and duration of exposure.

Class VI is the most stringent and was intended for fully implantable medical devices. The test was adopted as a worst-case solution by the filtration industry, even though the level of risk for patients was significantly lower than for implantable devices.

Although there are no regulations that require single-use components to be classified as USP <88> Class VI plastic, the biopharmaceutical industry elected to take the same approach as the filtration industry for single-use plastics, employing the most extreme, stringent testing conditions as the default testing performed for all polymeric materials —regardless of risk.

As a consequence, this industry practice has led to excessive and unnecessary animal testing. On a positive note, the recognition of this unwarranted practice is leading to reconsideration of the appropriateness of the tests in USP <87> and <88>.

Cytotoxicity Testing: A Proven Alternative

Cytotoxicity testing according to USP <87>, which is equivalent to ISO 10993-05, is a proven alternative to animal testing, and these in vitro tests can better assess the risk for polymers used in filtration and single-use system applications.

The tests are conducted in mammalian cells and provide more detail than is possible to obtain using animal testing, which involves subjective evaluation of the animal with respect to redness, irritation, swelling, and other factors. In vitro testing provides more quantitative results. For instance, the number of cells that die can be counted. There are other measurable effects, including measuring multiple cells lines. Overall, in vitro testing is a more reliable and much less judgmental approach.

Industry Alignment Is Essential

Many key opinion leaders within the pharmaceutical industry recognize that switching from animal to in vitro cytotoxicity testing for single-use plastics used in pharmaceutical manufacturing will not pose any safety risk for patients. Similar conclusions could be made about final containers for drug product, as well as packaging and delivery systems.

One of the challenges is who will take the first step, though the answer calls for solidarity. What we are hoping for is that the industry as a whole will be respectful of animal life and not play needless competitive games at their expense.

USP, we are happy to acknowledge, has made some initial moves. The organization recognizes these tests are not warranted for single-use plastics used in pharmaceutical manufacturing and have removed USP <88> animal testing from the relevant general chapters on pharmaceutical plastics. That is a pivotal action because UPS initially established the standard. This move is part of their overall strategy to reduce animal testing for in vitro testing wherever possible.

Equally important, the Bioprocess Systems Alliance (BPSA) Executive Board and the Biophorum Operations Group (BPOG) Drug Substance, Single-Use, and Regulatory Governance teams have responded positively when presented with the proposal to replace animal testing with in vitro testing. In addition, the initial discussions with standard-setting organizations indicate that they are open to removing USP <88> citations from voluntary standards.

End-User Education Is Important

There is more work to do, however, because many customers are likely not aware that animal testing is performed on single-use plastics employed in bioprocessing. They also probably do not know that the animals used in USP <88> Class VI testing suffer during the tests and are then put to death –– that is the reality.

Many also may be under the misconception that USP <88> Class VI testing is a regulatory requirement for filters and single-use systems. In addition, they may be unaware that more reliable in vitro testing alternatives exist.

Even those that are understand the full picture may still be resistant to change because the industry is very risk-averse. Quality systems are in place based on a known method that has been used for more than a decade. Quality SOPs and purchase specifications highlighting the need for USP <88> will need to be updated with alternative cytotoxicity standards. It is easier to tick the box that assures the worst-case scenario has been addressed, but not think about what those tests really involve.

The truth is that single-use plastics used in pharma processing have passed USP <88> testing for more than 20 years. Conducting these animal tests at this point really only serves to tick that box; it isn’t providing information of value. The question is: Where is the connection and what is the actual risk?

In addition, plastic materials employed in single-use systems have improved over the years and are extremely well characterized through a battery of chemical and in vitro tests, including extractables investigations. In Europe, pharmaceutical compendial standards for plastics do not include any biologic testing, not even in vitro testing.

Furthermore, these animal tests are not even used for IV bags. It doesn’t make sense that plastics used in applications much further removed from the patient would be subjected to more stringent tests than plastics used for the packaging and delivery of actual drug products.

Reasonable Approach

The ultimate goal is to replace USP <88> with USP <87> — at least by 2025. The actual date will be affected by when proposed changes by USP for <87> and <88> become effective and whether testing labs refuse to conduct USP 88 Class VI testing for anything except implantable medical devices. The idea is to change the testing checkbox from the specific USP <88> test to a checkbox for biocompatibility or biological reactivity that can be ticked using in vitro testing — or in vivo testing if warranted. 

At MilliporeSigma, as a first step, we have incorporated USP <87> in vitro testing into our Material Qualification SOP in addition to USP <88>. If the Biological Reactivity Tests, In Vitro <87> fail, the recommendation is to perform Biological Reactivity Tests, In Vivo <88>; for products where USP <88> Class VI test data already exists, re-testing to USP 87 would not be necessary, since USP 88 is the most stringent/worst case test.

The expectation is that MilliporeSigma will transition away from USP <88> in the not-too-distant future. In the meantime, we can be collecting additional data to substantiate the equivalent and even better performance of the in vitro versus in vivo tests.

The next step is to make USP <87> testing mandatory for components in new product development projects at MilliporeSigma. For new materials in the future, we are proposing to incorporate Biological Reactivity Tests, In Vitro <87> as part of the biocompatibility evaluation during material qualification of filters and single-use systems in lieu of Biological Reactivity Tests, In Vivo <88>. Doing so will demonstrate our commitment to the industry and provide an opportunity for others to take conservative steps in the right direction.

Our internal animal welfare group is also examining the overall organization’s use of animals and identifying use cases where such tests are not necessary. We are also reaching out to the various industry trade groups MilliporeSigma belongs to about the need to move away from animal testing and toward proven in vitro alternatives.

The industry also needs better guidelines for risk assessment so that companies do not continue to automatically select worst-case testing. Companies not only have a social responsibility to the animals, but also a responsibility to develop processes and products that address actual risk. From a risk assessment/management perspective, with the extensive chemical characterization and qualification done today, we have the necessary risk-appropriate tools to qualify single-use plastics without performing animal testing.

Now is the Time for Change

MilliporeSigma is not the only company in the pharmaceutical supply chain to establish an animal welfare initiative. Many firms across the value chain have such initiatives focused around the three Rs: reduce, refine, and replace, including efforts aimed at reducing animal testing and replacing in vivo testing with in vitro methods.

Some of MilliporeSigma’s customers are requesting both USP <87> and USP <88> testing, perhaps to establish data on the acceptability of the in vitro tests in advance of transitioning. At least one testing house in Europe is refusing to perform USP 88 Class VItesting for single-use components, citing its animal welfare policy, given that SU components are not implantable medical devices. Other testing companies have asked why they should be performing animal testing of single-use manufacturing components; they support a switch to in vitro testing for biocompatibility/bioreactivity.

While change is difficult, particularly in such a conservative industry, most people on the supplier side recognize that what is being done with animals to characterize the quality of plastics in terms of their biologic reactivity is wasteful. It is time to turn that recognition into action. We need the animal welfare officers at drug manufacturers to make that connection and realize that animal testing is performed — needlessly in many cases — across the supply chain and not just to demonstrate drug safety. Eliminating animal testing on single-use plastics used in bioprocessing is an obvious action that can move their animal welfare initiatives forward.

With our greater understanding of alternative technologies to animal testing, it is the time now to move forward with implementing the three Rs and eliminating animal testing for the determination of biocompatibility/bioreactivity of filters and single-use plastic components used in drug manufacturing.

Supporting Drug Manufacturers through the Emprove® Program

The complexity — and in some cases lack of clarity — of regulatory requirements for issues like this was a driver behind the establishment of the Emprove® Program at MilliporeSigma. Through the Emprove® Program, we provide comprehensive, up-to-date documentation on over 400 raw and starting materials, as well as filters and single-use components, selected chromatography resins, and cell culture media, to help manufacturers navigate both current and anticipated regulatory challenges, manage risks, and improve their manufacturing processes. Customers accessing the Emprove® Dossiers and the data and information provided are able to ensure that they stay on top of the latest regulatory requirements and can anticipate industry expectations not yet covered by regulation.

Taking the First Steps

Animal testing may still be necessary, but it really should only be performed if absolutely warranted, if there are no other alternatives, and if animal testing provides results that are needed to establish the safety of a drug product. If it isn’t warranted or doesn’t provide essential information and there are alternatives that have been demonstrated to generate reliable results, then animal testing has no place. 

We are gratified that, in our conversations with others in the industry, interest is growing in moving away from animal testing not only for assessing the biocompatibility/bioreactivity of filter and single-use components, but also other areas where animal testing may similarly not be necessary.

This response is very encouraging. At the outset, we anticipated that this project would take at least five years. Now, we are optimistic that it could take much less time. We are excited to collaborate with others to establish industry-wide consensus and address any questions that arise.

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