Substituting In Vitro for In Vivo Potency and Safety Assays: Science Versus the Fear Factor*

Transcription

1 Substituting In Vitro for In Vivo Potency and Safety Assays: Science Versus the Fear Factor* Dean Smith Ph.D. Centre for Biologics Evaluation, Health Canada Implementing non-animal approaches to human and veterinary vaccine testing: Achieving scientific and regulatory success for rabies and beyond. Bethesda, Maryland, October 2018

2 Acknowledgments European Directorate for the Quality of Medicines (EDQM) Vaccines Working Group (Groups 15 and 15V) for In Vitro Substitution (Eur. Ph ); initiated Sept 2012, Chapter implemented Jan 2018 (6 years!!) Arnoud Akkermans (Netherlands)* Thea Sesardic (UK) Kaare Hasløv (Denmark) Lukas Bruckner (Switzerland) Eva Vitkova (EDQM) Laurent Mallet (France) Paul Stickings (UK) Svein Andersen (Norway) Emmanuelle Charton (EDQM)** Gwenaël Cirefice (EDQM) Health Canada Maria Baca-Estrada, Richard Isbrucker, Tong Wu, Richard Siggers Center for Biologics Evaluation and Research (CBER), US/FDA Robin Levis 2

3 How industry feels about regulations VACCINE 3

4 Objectives Understanding the nature and time scale of the apparent in vivo assay Catch 22¹ for several key public heath vaccines, including rabies vaccine. Identifying the barriers to development and authorization of alternative in vitro assays. Defining a more science-based, less fear-based, risk-aware path forward. ¹Catch 22: A dilemma or difficult circumstance from which there is no escape because of mutually conflicting or dependent conditions. Key message: The in vivo assay dilemma is resolvable!! 4

5 What the goal is where is the Catch 22? Quality Safety Efficacy Manufactured Vaccine Availability Requires: Innovation (Regulatory Authorities and Industry)* Science-based decision making Science-based manufacturing and testing Science-based regulatory standards Regulatory Harmonization/Convergence 5

6 Vaccine QC Without In Vivo Testing Many non-live* vaccines are controlled through production, lot release & stability testing without the use of in vivo assays e.g., Human Papilloma Virus (HPV) Vaccines; recombinant viral-like particles (VLP) plus adjuvant(s), controlled with physical, chemical methods and ELISA Meningococcal and Pneumococcal Bacterial Conjugate Vaccines; defined polysaccharides conjugated to carrier proteins, controlled with physical and chemical methods** Key message: Modern QC control strategies for the above vaccines involve a combination in vitro methods to monitor the key quality attributes necessary to maintain the efficacy and safety profile of the product established at licensure, which is also monitored over product s shelf-life. 6

7 Quality is built into the process Design, development, in-process controls, cgmp Consistency monitoring; a vaccine may be tested > 300 times before release Starting materials Purification Formulation Fermentation Inactivation Release Approved rabies vaccines in North American and Europe have been manufacture and formulated using in vitro assays for decades, and then potency tested* Typically conjugate bacterial vaccine label claims are in µg/mg of defined components (i.e., specific polysaccharides or adjuvant respectively)** 7

8 Yet the Apparent Catch 22 with In Vivo Testing for Vaccines* Persists When the project was initiated in 2012, the NIH rabies vaccine potency test was just one example of an in vivo test where alternative methods either existed, could be developed or, in some cases, could be deleted due to their lack of scientific/regulatory relevance (e.g., General Safety Test (GST)). 3R regulations in the EU did not prevent the delays with in vitro assay implementation or, when justified, the deletion of in vivo tests, which included**: Rabies NIH test 35 yrs. of in vitro assays development (SRID, in vitro neutralization & stability indicating GP ELISA) yet no implementation GST for vaccines 20 yrs. of effort in EU (PEI) resulted the GST deletion for Vet. vaccines & reductions with Hu. in Eur. Ph., but the GST was still in Hu. vaccine licences in EU, NA & in WHO / national vaccine guidance worldwide Pertussis vaccine HIST¹ 20 yrs. of effort had little impact on implementation of alternative in vitro assays for the HIST for Eur. Ph., WHO or national guidance Toxoid irreversibility testing in spite of decades of toxoid stability data supporting licenced vaccine toxoid stability, in vivo irreversibility testing still generally required Rabbit pyrogenicity preferred by most authorities over a monocyte activation test (MAT) DPT² potency & safety tests due lack of progress via conventional pathways, VAC2VAC conceived Key message: A scientific, less animal-centric** mindset is necessary at an international level to implement alternative in vitro assays, given the current world market for vaccine manufacturers. ¹Histamine Sensitization Test: to demonstrate absence of pertussis toxin in human pertussis toxoid vaccines ²Diphtheria (D), Pertussis (P) and Tetanus (T) combination vaccines 8

9 Key Limitations of In Vivo Assays & Considerations with In Vitro Alternatives Decades of failed efforts, prompted EDQM Group 15 to better understand the limitations of, and deconstruct the myths perpetuating in vivo assay use: The inherent variability of in vivo assays has resulted in multiple failures of multi-centre international collaborative studies that required one-to-one comparison with more-consistent in vitro methods (e.g., for alternatives to NIH rabies test) Most in vivo assays predate ICH Q2 (R1) or VICH GL2 guidelines, yet are considered validated since they are compendial. Hence, one-one comparisons are challenging or not possible in some cases because precision, reproducibility, limits of detectability, etc., may not be established and would be unethical or against EU conventions to do so retrospectively While properly established in vivo methods have the potential* to measure complex functional responses for demonstrating proof of concept, they do not predict the responses in the target population. They are merely, highly variably bioassays. Since an in vitro alternative assay QC strategy, using one or more new methods, will likely assess the same quality attribute differently, the expectation of a one-one agreement between in vitro and in vivo assays may not be scientifically justified. Yet, the in vitro test strategy must provide at least the same confidence regarding the control of the key quality attributes. Case studies support this expectation. 9

10 A New Approach for both Human and Veterinary Vaccines Substitution as a alternative approach for in vitro assay implementation: Replacement: Involves a one-to-one comparison and establishment of a correlation between the two methods (e.g., in vitro to in vivo)*. Substitution: To facilitate the implementation of in vitro methods as substitutes for existing in vivo methods, in cases where a typical one-to-one assay comparison is not appropriate for reasons unrelated to the suitability of one or more in vitro methods (Eur. Ph ). Stability Indicating: Quality parameters (direct or indirect indicators of vaccine efficacy or safety) that are sensitive to storage conditions. These parameters are used in stability studies to assure product quality throughout the shelf-life. Determination of these parameters should result in quantitative values with a detectable rate of change (WHO TRS 999, Annex 5, Vaccine Stability Guidance Definition). 10

11 September 2015 EPAA Workshop Impact on Group 15 Deliberations on Eur. Ph Modern science for better quality control of medicinal products Towards global harmonization of 3Rs in biologicals : The report of an EPAA Workshop. Biologicals, 48 (2017), pp Expectations for the workshop were heightened by the deletion of the GST from the US FDA Code of Federal Regulations (21 CFR ) in June of 2015 Industry stressed the resource drain with multiple versions of in vivo potency and safety assays for several DPT vaccines. Additionally, needless lot release delays due to in vivo testing with month long assays and invalid tests requiring repeat testing were impacting otherwise compliant lots and causing vaccine shortages. PEI presented the clear case that the there has long been no scientific rationale to retain the so called General Safety Test (GST). Originally designed as a phenol and tetanus toxin assay in the early 1900s but had lost a useful role in QC for vaccines decades ago. NIBSC presented results with in vitro (ELISA) and in vivo potency assays for diphtheria (D) and tetanus (T) products. Analysis of the results demonstrated the higher sensitively and improved stability indicating potential of the in vitro methods. The key GST and PT in vitro potency conclusions from the EPAA Workshop were presented to Group 15 and greatly helped drive the development and GST deletion efforts to completion. Key message: Workshops can have a major impact, but this requires follow up. 11

12 What Eur. Ph States Concerning In Vivo and In Vitro Assays for Vaccine QC All QC methods should ensure comparability of the quality attributes between commercial batches and those batches originally found to be safe and efficacious in clinical studies or, for veterinary vaccines, in the target species. However, the inherent variability of in vivo assays can make them less suitable* than appropriately designed in vitro assays for monitoring consistency of production and for assessing the potential impact of manufacturing changes. As a result, it is essential [to] continually [to] challenge the scientific value and relevance of these in vivo test methods. The use of appropriate in vitro methods enhances the predictability of the release of safe and effective vaccine lots for use. Key message: Group 15 moved past the fear of loss of, and attachment to, animal assays. This was the result of an evidence-based discussion, where long standing beliefs were challenged and put aside. 12

13 Key Elements of Alternate Approach The primary focus for the implantation of any proposed in vitro method within a QC system should be the scientific relevance of the in vitro assays for control of the key quality attributes While in the Eur. Ph., in vivo assay replacement with in vitro assays is typically achieved following multicentre collaborative studies, this should not be a prerequisite for individual products. While it may be desirable to have assays that are widely applicable to a class of products, this should be a requirement. In some cases an existing in vivo method may need to be substituted by more than 1 in vitro method to characterise the key qualitative and quantitative attributes measured by the existing test. 13

14 Alternate Approach Cont d Considerations regarding key principles and approaches with specific types of assay are presented in Eur. Ph Potency assays: Design of stability indicating assays, or combinations of alternate methods to capture key quality attributes related to potency is discussed General fit for purpose principles are also discussed Safety assays: Considerations for different types of assay are presented for: Specific Toxicity Molecular consistency by deep sequencing versus the neurovirulence test Detection of viral extraneous agents by novel molecular methods 14

15 Progress During and Post Adventitious Agent Testing* Eur. Ph Tests for extraneous agents in viral vaccines for human use Eur. Ph Cell substrates for the production of vaccines for human use GST for vaccines removed from Eur. Ph. and consultations with WHO have begun Pertussis (PT) HIST proposed for deletion in Eur. Ph.: control at DS & stability of toxoid PT Irreversibility proposed for deletion in Eur. Ph.: toxoid stability & test relevance Rabbit Pyrogenicity new MAT monograph proposed for inherently pyrogenic vaccines** DT Potency & Safety Tests in vitro assays in development through the VAC2VAC consortium & are in consultation with EDQM and EMA Rabies NIH Test GP ELISA suggested as model assay for substitution in Eur. Ph What prevents authorisation in EU and North America? Key message: Rigorous scientific debate and questioning of beliefs can lead to remarkable changes. Group 15 now amends the rules to fit the science, which supports innovation. 15

16 Next steps As per Eur. Ph , Group 15 will continue to examine the scientific rationale for existing in vivo potency and safety assays with a less fear-driven, more risk aware and science-based approach. The European-based VAC2VAC consortium is actively working to develop in vitro methods for vaccine characterization, in process controls and QC release assays as substitutes for existing in vivo methods. A less fear-driven and more science-driven assessment approach from all agencies regarding the eventual proposals, would be a more innovative regulatory response to this initiative. This workshop has the potential to impact the NIH rabies potency assay, as did the Group and the 2015 EPAA discussions regarding the GST and HIST. What can we collectively do to make that a reality? 16

17 Questions? 17