Improving Viral Safety: Highlights Of ICH Q5A(R2), USP, Ph. Eur. Recommendations

By Tim Sandle, Ph.D.

Since 1997, the primary guidance for virus testing, viral clearance, and viral safety for the manufacture of impacted pharmaceuticals has been ICH Q5A.¹ The latest version of ICH Q5A (revision 2) was released on Nov. 1, 2023, and adopted by the U.S. FDA in January 2024 and by the European Medicines Agency in June 2024. This followed a lengthy consultation process for the revision, which commenced in October 2022.

As with similar guidances, the primary drivers for the update were advancements in scientific knowledge relating to test methods and process controls,² together with the expansion of the range of biotechnological products that require virus clearance and virus control (including genetically engineered viral vectors and viral-vector-derived products).³ The revised guideline also extends to include continuous manufacturing.

Consequently, ICH Q5A(R2) brings the test methods for virus screening up to date with the inclusion of polymerase chain reaction (PCR) and next-generation sequencing (NGS). Both methods facilitate the rapid and sensitive detection of endogenous viruses and adventitious contaminants. The inclusion of these methods presents a distinction with conventional virus detection assays (in vivo, in vitro, and retrovirus).

While ICH Q5A(R2) brings the science of viral control up to date, practical considerations require a fuller and more detailed assessment. For this, compendia like the USP provide additional guidance. This article considers where sources of additional guidance will prove most useful.

Method Selection And Qualification Considerations

Both PCR and NGS provide highly sensitive and reliable virus detection technologies and as described in ICH Q5A(R2), PCR detects known sequences, whereas NGS is a hypothesis-free approach that does not require prior knowledge of sequence information. While using PCR and NGS provides significant advantages, as with any analytical procedure a series of steps need to be followed for the method to be deemed suitable.

Both USP and the European Pharmacopeia provide additional recommendations that complement ICH Q5A(R2). Based on the compendia, it is good practice to consider:

• Whether a comparability test with a conventional method is required (especially where the conventional method is considered to be inferior)
• Design of the validation to include sufficient robustness and system suitability tests
• Selecting the appropriate validation parameters, including specificity and limit of detection (and also “breadth of detection” as applicable to high-throughput sequencing for adventitious virus detection)⁴
• Vulnerability of the method in terms of environmental viral contaminants (such as arising from the laboratory environment)
• Understanding the limitations of validation and method suitability studies
• Taking care to use representative model viruses in validation experiments
• Determining whether end-to-end or step-by-step validation studies are most appropriate. End-to-end testing is a comprehensive validation method that assesses an application's workflow from start to finish instead of breaking down the validation process into discrete steps.
• The life cycle management of the adopted method, including responsiveness to future viral genome database updates and subsequent impact on the need for any revalidation

In addition, while ICH Q5A(R2) provides a general overview of introducing technologies, it does not detail the practical application in a sufficient level of detail. To address this gap, the USP provides case study application examples and the European Pharmacopeia provides suggestions for performing risk assessments.

Design Space

The primary chapter in the USP is “Viral Safety Evaluation of Biotechnology Products Derived from Cell Lines of Human or Animal Origin” 〈1050〉. This is supported by chapter 〈1050.1〉 “Design, Evaluation, and Characterization of Viral Clearance Procedures.” The advantage offered by chapter 〈1050.1〉 is a series of practical points for the facility to consider when setting out the design, evaluation, and characterization of viral clearance procedures. This includes how modern technologies can be applied to a viral clearance study and the type of data that needs to be generated and presented to demonstrate the suitability of the manufacturing and purification processes to remove or inactivate a sufficiently broad spectrum of viral types.

The more practically based USP approach can help guide the facility with the application of ICH Q5A(R2) by:

• Reviewing downstream processing steps and identifying which steps present the greatest risk and therefore need to be evaluated. This requires the application of a risk assessment.
• Defining critical process parameters
• Defining a rationale for worst-case conditions
• Developing appropriate controls for each step
• Considering the nature of viruses of concern and whether to have two independent mechanisms of virus clearance (such as one aimed at virus removal, and another aimed at virus inactivation or different methods that target enveloped and non-enveloped viruses)⁵
• Constructing a sampling plan
• Considering sample handling and storage
• Providing a framework for new product development (from scale-up to commercial realization). Many novel processes are subject to unknown or unpredictable capacity for viral clearance.
• Understanding process capacity and capability
• Developing suitable sampling points and sampling time points

The above need to be captured in a detailed validation protocol prior to execution.

For guidance on conducting risk assessments, European Pharmacopeia chapter 5.1.7 provides guidance on the identification of the various factors that may influence the potential level of infectious particles in the medicinal product together with the factors related to the use of the medicinal product that determine or influence the viral risk to the recipients.

Establishing The Log Reduction Factor

A distinction between the ICH guidance and the compendia is the acceptable virus reduction factor. ICH Q5A(R2) presents between 1 and 3 logs₁₀ as being suitable for the reduction of the viral load (depending on the challenge titer). For the USP, a log reduction factor of 4 for viral clearance needs to be demonstrated for each virus clearance. Where a reduction factor of 1 to 3 log₁₀ is achieved, the USP regards this as having the status of a “supportive step.”

While both ICH Q5A(R2) and the USP state that at least two independent experiments (or studies) must be performed to demonstrate the reproducibility of an effective viral clearance step, the USP also advises that reproducibility needs to be supported by the process development history.

Steps To Lower Virus Risks

ICH Q5A(R2) places considerable emphasis on virus clearance and supporting testing; less attention is paid to constructing a risk framework. However, several risk factors need to be evaluated:

• The control of incoming materials and potentially contaminated excipients, including animal-derived additives such as bovine serum albumin. Many incidents of viral contamination stem from using poorly characterized materials. Two European documents offer practical solutions to lower viral risks from the outset and these are useful for supporting the intent of the ICH guidance. These are:
  • CPMP/ICH/294/95⁶
  • CPMP/ICH/295/95⁷

These documents provide criteria for the assessment of biological activity, the purity-impurity profile, the risk of adventitious viral agents, and stability.

• Safeguarding the contamination of cell lines
• Performing adequate purification and formulation reagents
• Characterizing the presence of any impurities that could lead to viral stability occurring within the process

A topic not sufficiently developed within ICH Q5A(R2) is how to suitably contain and segregate zones within a manufacturing plant that are at greatest risk from viruses. The objective is to prevent re-contamination of products by other products and materials that have not been subject to virus elimination methods. A virus-free zone can be developed by using a segregated space, separate air filtration (which can be supported by viral-inactivating ionization),⁸ separate personnel changing areas and dedicated clothing, dedicated equipment, and ensuring that consumables have not been exposed to other areas of the facility. Regarding the latter point, single-use disposable technologies present an advantage.⁹ A risk framework is necessary to consider the potential for control failures within a viral secure area and the types of remediation actions necessary to recover the zoned area.

A practical assessment of the virus security measures can be demonstrated through special bioaerosol samplers and electrostatic precipitators, with assaying using plaque assays (for bacteriophages) and for viral nucleic acids using quantitative PCR assays.

Regulatory Acceptance

When adopting any innovative technology, planning the regulatory pathway is a major step. To ensure regulatory acceptance for a technology like NGS, a clear strategy is required based on the validation, intended practical use (including process flowcharts and product life cycle stage), and registration requirements. The existence of ICH Q5A(R2) makes the process of acceptance easier; however, each facility will need to develop a strategy applicable to their product and to their own national regulator. One useful source of regulatory pathway guidance is provided by the Australian TGA.¹⁰

The issues discussed in this article indicate that while ICH Q5A(R2) is a very useful document, and the current version a significant advance on its forerunner, there are other documents that enhance the guidelines and offer additional practical solutions.

References

1. ICH Q5A(R2) Guideline on viral safety evaluation of biotechnology products derived from cell lines of human or animal origin - Scientific guideline, International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use: Geneva, Switzerland https://database.ich.org/sites/default/files/ICH_Q5A%28R2%29_Guideline_2023_1101.pdf
2. Barone PW, et al. Viral Contamination in Biologic Manufacture and Implications for Emerging Therapies. Nature Biotechnol. 38, 2020: 563–572; https://doi.org/10.1038/s41587-020-0507-2
3. Perez-Caballero, D., Murray, D., Niederlaender, C. and Brorson, K. Viral Safety for Biotechnology Products, Including Viral Vectors: ICH Q5A Revision 2 Brings Updated and More Comprehensive Guidance, BioProcess International, May 2023: https://www.bioprocessintl.com/viral-clearance/viral-safety-for-biotechnology-products-including-viral-vectors-ich-q5a-revision-2-brings-updated-and-more-comprehensive-guidance
4. Charlebois, R.L., Sathiamoorthy, S., Logvinoff, C. et al. Sensitivity and breadth of detection of high-throughput sequencing for adventitious virus detection. npj Vaccines 5, 61 (2020). https://doi.org/10.1038/s41541-020-0207-4
5. Sandle, T. (2015) Current Methods and Approaches for Viral Clearance, American Pharmaceutical Review: https://www.americanpharmaceuticalreview.com/Featured-Articles/179320-Current-Methods-and-Approaches-for-Viral-Clearance /
6. EMA. Note for guidance on quality of biotechnological products: derivation and characterisation of cell substrates used for production of biotechnological/biological products - external site (CPMP/ICH/294/95)
7. EMA. Note for guidance on quality of biotechnological products: viral safety evaluation of biotechnology products derived from cell lines of human or animal origin - external site (CPMP/ICH/295/95).
8. Malaithao K, Kalambaheti T, Worakhunpiset S, Ramasoota P. (2009) Evaluation of an electronic air filter for filtrating bacteria and viruses from indoor air, Southeast Asian J Trop Med Public Health. 40(5):1113-20
9. Sandle, T. and Saghee, M. R. (2011): Some considerations for the implementation of disposable technology and single-use systems in biopharmaceuticals, Journal of Commercial Biotechnology, 17 (4): 319–329
10. Therapeutics Products Administration. Guidance 10: Adventitious agent safety of medicines. Australian government: https://www.tga.gov.au/resources/resource/guidance/guidance-10-adventitious-agent-safety-medicines

About The Author:

Tim Sandle, Ph.D., is a pharmaceutical professional with wide experience in microbiology and quality assurance. He is the author of more than 30 books relating to pharmaceuticals, healthcare, and life sciences, as well as over 170 peer-reviewed papers and some 500 technical articles. Sandle has presented at over 200 events and he currently works at Bio Products Laboratory Ltd. (BPL), and he is a visiting professor at the University of Manchester and University College London, as well as a consultant to the pharmaceutical industry. Visit his microbiology website at https://www.pharmamicroresources.com.