Jayanthi J. Wolf

Nonclinical Safety Assessment of Vaccines and Adjuvants

To ensure the safe administration of vaccines to humans, vaccines (just like any new chemical entity) are evaluated in a series of nonclinical safety assessment studies that aim at identifying the potential toxicities associated with their administration. The nonclinical safety assessment of vaccines, however, is only part of a testing battery performed prior to human administration, which includes (1) the evaluation of the vaccine in efficacy and immunogenicity studies in animal models, (2) a quality control testing program, and (3) toxicology (nonclinical safety assessment) testing in relevant animal models. Although each of these evaluations plays a critical role in ensuring vaccine safety, the nonclinical safety assessment is the most relevant to the evaluation in human clinical trials, as it allows the identification of potential toxicities to be monitored in human trials, and in some cases, eliminates candidates that have unacceptable risks for human testing. This review summarizes the requirements for the nonclinical testing of vaccines and adjuvants needed in support of all phases of human clinical trials.

Application of PCR technology in vaccine product development

The complex process of vaccine product development needs to be tightly controlled and closely monitored to ensure vaccine quality and consistency. Since its inception, PCR has been widely used in all stages of vaccine product development as a tool to assist in the evaluation of vaccine quality, safety and efficacy. In this review, the general principles of conventional and real-time quantitative PCR (Q-PCR) technology and its application in vaccine product development for quantitation of vaccine dose (genome quantitation assay), infectivity (Q-PCR-based potency assay), process residuals, stability, adventitious agents, safety assessment and clinical studies are described. The future outlook and the advantages and disadvantages of this technology are also discussed.

Clinical development of a recombinant Ebola vaccine in the midst of an unprecedented epidemic

The 2014-2016 Ebola outbreak caused over 28,000 cases and 11,000 deaths. Merck & Co. Inc., Kenilworth, NJ USA and NewLink Genetics are working with private and public partners to develop and license an Ebola vaccine that was evaluated extensively during the outbreak. The vaccine referred to as V920 is a recombinant vesicular stomatitis virus (rVSV) in which the VSV-G envelope glycoprotein (GP) is completely replaced by the Zaire ebolavirus GP (rVSVΔG-ZEBOV-GP). Eight Phase I and four Phase II/III clinical trials enrolling approximately 17,000 subjects were conducted in parallel to the outbreak to assess the safety, immunogenicity, and/or efficacy of V920. Immunogenicity data demonstrate that anti-GP antibodies are generally detectable by ELISA by 14days postvaccination with up to 100% seroconversion observed by 28days post dose. In addition, the results of a ring vaccination trial conducted by the WHO and their partners in Guinea suggest robust vaccine efficacy within 10days of receipt of a single dose of vaccine. The vaccine is generally well-tolerated when administered to healthy, non-pregnant adults. The development of this vaccine candidate in the context of this unprecedented epidemic has involved the close cooperation of large number of international partners and highlights what we as a public health community can accomplish when working together towards a common goal. Study identification: V920-001 to V920-012. CLINICALTRIALS.GOV identifiers: NCT02269423; NCT02280408; NCT02374385; NCT02314923; NCT02287480; NCT02283099; NCT02296983; NCT02344407; NCT02378753; NCT02503202.

Strategies for the Nonclinical Safety Assessment of Vaccines

Over the past century, vaccines have made a large impact on public health. Prophylactic vaccines prevent disability and disease, saving millions of dollars in potential health-care spending. Since prophylactic vaccines are administered to healthy individuals, including infants and children, it is important to demonstrate the safety of vaccines preclinically prior to testing the vaccine in clinical studies. A benefit-to-risk profile is considered for each individual vaccine and depends on many factors including preclinical and clinical toxicities that are observed, frequency of administration and intended target population. For prophylactic vaccines, in particular, the concerns about potential risks often outweigh the perception of benefit [1]. Therefore, over the past decade, there has been an increased focus on nonclinical safety assessment of vaccines, including toxicity testing.

Special Considerations for the Nonclinical Safety Assessment of Vaccines

Abstract There are numerous prophylactic and therapeutic vaccines currently in development, covering a plethora of mechanisms, often including novel adjuvants and innovative delivery systems. Since prophylactic vaccines are generally administered to healthy individuals, it is critical to ensure vaccine safety prior to clinical evaluation. This chapter will discuss special considerations for thorough nonclinical safety evaluation of vaccines. De-risking strategies for vaccines will be reviewed. Assays to evaluate vaccine pharmacodynamics will be described and compared with assays to evaluate pharmacokinetics of novel biopharmaceuticals. Finally, an overall comparison between the nonclinical safety evaluation of vaccines and other biopharmaceutical products will be provided.

A multi-species assay for siRNA-mediated mRNA knockdown analysis without the need for RNA purification

INTRODUCTION Various animal models are routinely used to evaluate the efficacy and toxicity of small interfering RNA (siRNA) therapeutics. Given that the most common measure of efficacy with siRNA therapeutics is mRNA knockdown, the development of a single assay for quantification of siRNA-mediated mRNA knockdown in multiple species would provide significant time and cost-savings during preclinical development. METHODS AND RESULTS We have developed an assay targeting short consensus sequences of a particular mRNA in multiple species using the principles of a recently-reported stem-loop RT-qPCR method (Chen et al., 2005). The multi-species RT-qPCR assay is highly sensitive, reproducible, has a dynamic range of seven orders of magnitude, and it can be used to quantify a specific mRNA in crude tissue homogenates without the need for RNA purification. Compared to the limitations of conventional RT-qPCR assays, this assay provides a simple and robust tool for mRNA quantification to evaluate siRNA-mediated mRNA knockdown. DISCUSSION This assay can potentially become a routine method for mRNA quantification to evaluate siRNA-mediated mRNA knockdown.

Current strategies in the non-clinical safety assessment of biologics: New targets, new molecules, new challenges

Nonclinical safety testing of biopharmaceuticals can present significant challenges to human risk assessment with these innovative and often complex drugs. Emerging topics in this field were discussed recently at the 2016 Annual US BioSafe General Membership meeting. The presentations and subsequent discussions from the main sessions are summarized. The topics covered included: (i) specialty biologics (oncolytic virus, gene therapy, and gene editing-based technologies), (ii) the value of non-human primates (NHPs) for safety assessment, (iii) challenges in the safety assessment of immuno-oncology drugs (T cell-dependent bispecifics, checkpoint inhibitors, and costimulatory agonists), (iv) emerging therapeutic approaches and modalities focused on microbiome, oligonucleotide, messenger ribonucleic acid (mRNA) therapeutics, (v) first in human (FIH) dose selection and the minimum anticipated biological effect level (MABEL), (vi) an update on current regulatory guidelines, International Council for Harmonization (ICH) S1, S3a, S5, S9 and S11 and (vii) breakout sessions that focused on bioanalytical and PK/PD challenges with bispecific antibodies, cytokine release in nonclinical studies, determining adversity and NOAEL for biologics, the value of second species for toxicology assessment and what to do if there is no relevant toxicology species.

Reliable quantification of mRNA in archived formalin-fixed tissue with or without paraffin embedding

INTRODUCTION Formalin fixation and paraffin embedding (FFPE) is a standard method for tissue sample storage and preservation in pathology archives. The Reverse Transcriptase Quantitative Polymerase Chain Reaction (RT-qPCR) is a useful method for gene expression analysis, but its sensitivity is significantly decreased in FFPE tissue due to the fixation process. This process results in chemical modifications of RNA, cross-links proteins to RNA, and degrades RNA in these archived samples, hindering the reverse transcription step of the conventional RT-pPCR method and preventing generation of a cDNA that is long enough for the subsequent quantitative PCR step. METHODS In this study, we used a multi-species RT-qPCR method originally developed to detect mRNA in tissue homogenate samples (Wang et al., 2011) and applied it to effectively detect a specific mRNA in formalin-fixed tissues with or without paraffin-embedding by targeting mRNA sequences as short as 24 nucleotides. RESULTS Target sizes ranging from 24 to 91 nucleotides were evaluated using this multi-species RT-qPCR assay. Data generated with FFPE tissues demonstrated that use of short target sequences relieved the dependence on RNA quality and could reliably quantify mRNA. This method was highly sensitive, reproducible, and had a dynamic range of five orders of magnitude. Importantly, this method could quantify mRNA in prolonged formalin-fixed and FFPE tissue, where conventional RT-qPCR assays failed. Moreover, a similar result for small interfering RNA (siRNA)-mediated Apob mRNA knockdown was obtained from tissues fixed in formalin solution for 3months to 4years, and was found to be comparable to results obtained with frozen liver tissues. DISCUSSION Therefore, the method presented here allows for preclinical and clinical retrospective and prospective studies on mRNA derived from archived FFPE and prolonged formalin-fixed tissue.

Quantifying the Titer and Quality of Adenovirus Stocks

The broad application of recombinant adenoviruses to the development of vaccines and gene therapy vectors has encouraged the development of molecular assays for the facile quantitation of adenoviral particles and the assignment of their infectious potency. The Genome Quantitation Assay (GQA) and the QPCR-Based Potency Assay (QPA) developed for adenoviruses offer the attributes of precision, rapidity, and high throughput either performed manually or facilitated by simple automated liquid handling systems. These assay attributes allow for accelerated process development support and product characterization and release. The assays for adenovirus could offer the additional advantage in that their quantitation is based on viral replication independent of cytopathology permitting quantitation of serotypes that cause minimal cytopathic effect (CPE) in 293 cells and specificity that allows the components of multivalent vaccines to be discriminated and quantitated for release.

893. Using QPCR and Automation to Assign Infectious Potencies to Adenovirus Based Vaccines and Vectors for Gene Therapy

The potencies of test articles generated during bioprocess development supporting the manufacture of Ad5 based HIV vaccine have been assigned since 1999 using a QPCR-based Potency Assay (QPA). We report here the simplification of the Ad5 QPA through (1) the introduction of a facile method for the harvest of DNA for QPCR quantitation and (2) the integration of automated liquid handling systems for performing semi-automated or completely automated QPA assays. We demonstrate semi-automated QPA operation using the Beckman Coulter Multimek for the addition of reagents, preparation of dilutions, and set-up of PCR reactions in 384 well formats, which greatly reduce reagent cost and analyst time involved with QPA assays. We show preliminary results indicating that a fully automated assay is possible using a more versatile liquid handling system such as the Tecan Freedom Evo. We also present the results of a PreValidation Exercise (PreVEx) for the semi-automated QPA assay we designate Triton Lysis with the Multimek (TLM) Ad5 QPA, which exhibits a remarkable precision. The PreVEx demonstrated that the TLM Ad5 QPA has a root variability of approximately 16.8% and a format dependent variability (1|[times]|3 assay format, with 4 infection replicates per assay) of approximately 5.8%, allowing samples differing in potency by 17.4% to be discriminated with 95% confidence. This precision equals or exceeds the precision associated with the previous Ad5 QPA.