Rapid development of analytical methods for evaluating pandemic vaccines: a COVID-19 perspective

Clinical development of SpikoGen®, an Advax-CpG55.2 adjuvanted recombinant spike protein vaccine

Recombinant protein vaccines represent a well-established, reliable and safe approach for pandemic vaccination. SpikoGen® is a recombinant spike protein trimer manufactured in insect cells and formulated with Advax-CpG55.2 adjuvant. In murine, hamster, ferret and non-human primate studies, SpikoGen® consistently provided protection against a range of SARS-CoV-2 variants. A pivotal Phase 3 placebo-controlled efficacy trial involving 16,876 participants confirmed the ability of SpikoGen® to prevent infection and severe disease caused by the virulent Delta strain. SpikoGen® subsequently received a marketing authorization from the Iranian FDA in early October 2021 for prevention of COVID-19 in adults. Following a successful pediatric study, its approval was extended to children 5 years and older. Eight million doses of SpikoGen® have been delivered, and a next-generation booster version is currently in development. This highlights the benefits of adjuvanted protein-based approaches which should not overlook when vaccine platforms are being selected for future pandemics.

The Platform Technology Approach to mRNA Product Development and Regulation

mRNA-lipid nanoparticle (LNP) medicinal products can be considered a platform technology because the development process is similar for different diseases and conditions, with similar noncoding mRNA sequences and lipid nanoparticles and essentially unchanged manufacturing and analytical methods often utilised for different products. It is critical not to lose the momentum built using the platform approach during the development, regulatory approval and rollout of vaccines for SARS-CoV-2 and its variants. This review proposes a set of modifications to existing regulatory requirements for mRNA products, based on a platform perspective for quality, manufacturing, preclinical, and clinical data. For the first time, we address development and potential regulatory requirements when the mRNA sequences and LNP composition vary in different products as well. In addition, we propose considerations for self-amplifying mRNA, individualised oncology mRNA products, and mRNA therapeutics. Providing a predictable development pathway for academic and commercial groups so that they can know in detail what product characterisation and data are required to develop a dossier for regulatory submission has many potential benefits. These include: reduced development and regulatory costs; faster consumer/patient access and more agile development of products in the face of pandemics; and for rare diseases where alternatives may not exist or to increase survival and the quality of life in cancer patients. Therefore, achieving consensus around platform approaches is both urgent and important. This approach with mRNA can be a template for similar platform frameworks for other therapeutics and vaccines to enable more efficient development and regulatory review.

Electrophoretic characterization of LNP/AAV-encapsulated nucleic acids: Strengths and weaknesses

The use of nucleic acids (NAs) has revolutionized medical approaches and ushered in a new era of combating various diseases. Accordingly, there is an increasing demand for accurate identification, localization, quantification, and characterization of NAs encapsulated in nonviral or viral vectors. The vast spectrum of molecular dimensions and intra- and intermolecular interactions presents a formidable obstacle for NA analytical development. Typically, the comprehensive analysis of encapsulated NAs, free NAs, and their spatial distribution poses a challenge that is seldom tackled in its complete complexity. The identification of appropriate physicochemical methodologies for large nonencapsulated or encapsulated NAs is particularly intricate and necessitates an evaluation of the analytical outcomes and their appropriateness in addressing critical quality attributes. In this work, we examine the analytics of non-encapsulated or encapsulated large NAs (>500 nucleotides) utilizing capillary electrophoresis (CE) and liquid chromatography (LC) methodologies such as free zone CE, gel CE, affinity CE, and ion pair high-performance liquid chromatography (HPLC). These methodologies create a complete picture of the NA's critical quality attributes, including quantity, identity, purity, and content ratio.

Updated Considerations for the Immunopharmacological Aspects of the "Talented mRNA Vaccines"

Messenger RNA (mRNA) vaccines belong to a new class of medications, RNA therapeutics, including both coding and non-coding RNAs. The use of mRNA as a therapy is based on the biological role of mRNA itself, namely its translation into a functional protein. The goal of mRNA vaccines is to produce a specific antigen in cells to elicit an immune response that might be prophylactic or therapeutic. The potential of mRNA as vaccine has been envisaged for years but its efficacy has been clearly demonstrated with the approval of COVID-19 vaccines in 2021. Since then, mRNA vaccines have been in the pipeline for diseases that are still untreatable. There are many advantages of mRNA vaccines over traditional vaccines, including easy and cost-effective production, high safety, and high-level antigen expression. However, the nature of mRNA itself and some technical issues pose challenges associated with the vaccines' development and use. Here we review the immunological and pharmacological features of mRNA vaccines by discussing their pharmacokinetics, mechanisms of action, and safety, with a particular attention on the advantages and challenges related to their administration. Furthermore, we present an overview of the areas of application and the clinical trials that utilize a mRNA vaccine as a treatment.

Using Peptide Nucleic Acid Hybridization Probes for Qualitative and Quantitative Analysis of Nucleic Acid Therapeutics by Capillary Electrophoresis

The space of advanced therapeutic modalities is currently evolving in rapid pace necessitating continuous improvement of analytical quality control methods. In order to evaluate the identity of nucleic acid species in gene therapy products, we propose a capillary electrophoresis-based gel free hybridization assay in which fluorescently labeled peptide nucleic acids (PNAs) are applied as affinity probes. PNAs are engineered organic polymers that share the base pairing properties with DNA and RNA but have an uncharged peptide backbone. In the present study, we conduct various proof-of-concept studies to identify the potential of PNA probes for advanced analytical characterization of novel therapeutic modalities like oligonucleotides, plasmids, mRNA, and DNA released by recombinant adeno-associated virus. For single-stranded nucleic acids up to 1000 nucleotides, the method is an excellent choice that proved to be highly specific by detecting DNA traces in complex samples, while having a limit of quantification in the picomolar range when multiple probes are used. For double-stranded samples, only fragments that are similar in size to the probe could be quantified. This limitation can be circumvented when target DNA is digested and multiple probes are used opening an alternative to quantitative PCR.

Evaluating the efficacy and safety of SpikoGen®, an Advax-CpG55.2-adjuvanted severe acute respiratory syndrome coronavirus 2 spike protein vaccine: a phase 3 randomized placebo-controlled trial

OBJECTIVES

We sought to investigate the efficacy and safety of SpikoGen®, a subunit coronavirus disease 2019 (COVID-19) vaccine composed of a recombinant severe acute respiratory syndrome coronavirus 2 spike protein with Advax-CpG55.2™ adjuvant.

METHODS

This randomized, placebo-controlled, double-blind, phase 3 trial was conducted on 16 876 participants randomized (3:1) to receive two intramuscular doses of SpikoGen® or a saline placebo 21 days apart. The primary outcome was to assess the efficacy of SpikoGen® in preventing symptomatic COVID-19. Secondary outcomes included safety assessments and evaluation of SpikoGen® vaccine's efficacy in preventing severe COVID-19. The study aimed for 147 COVID-19 symptomatic cases.

RESULTS

Overall, 12 657 and 4219 participants were randomized to the SpikoGen® and placebo group and followed for a median of 55 days (interquartile range, 48-60 days) and 51 days (interquartile range, 46-58 days) after 14 days of the second dose, respectively. In the final per-protocol analysis, the number of COVID-19 cases was 247 of 9998 (2.4%) in the SpikoGen® group and 119 of 3069 (3.8%) in the placebo group. This equated to a vaccine efficacy of 43.99% (95% CI, 30.3-55.0%). The efficacy was calculated to be 44.22% (95% CI, 31.13-54.82%) among all participants who received both doses. From 2 weeks after the second dose, 5 of 9998 (0.05%) participants in the SpikoGen® group and 6 of 3069 (0.19%) participants in the placebo group developed severe COVID-19, equating to a vaccine efficacy against severe disease of 77.51% (95% CI, 26.3-93.1%). The SpikoGen® vaccine was well tolerated.

DISCUSSION

A 2-dose regimen of SpikoGen® reduced the rate of COVID-19 and severe disease in the wave of the Delta variant.

Rapid Identity and Quantity CQA Test for Multivalent mRNA Drug Product Formulations

The COVID-19 pandemic highlighted mRNA as a promising platform for vaccines and therapeutics. Many of the analytical tools used to characterize the critical quality attributes of mRNA are inherently singleplex and are not necessarily optimal from a labor and cost perspective. Here, we demonstrate the feasibility of a multiplexed platform (VaxArray) for efficient identity verification and concentration determination for both monovalent and multivalent mRNA formulations. A model system comprising mRNA constructs for influenza hemagglutinin and neuraminidase was used to characterize the analytical performance metrics for a VaxArray mRNA assay. The assay presented herein had a time to result of less than 2 h, required no PCR-based amplification nor extraction of mRNA from lipid nanoparticles, and exhibited high construct specificity that enabled application to the bivalent mixture. The sensitivity for influenza hemagglutinin and neuraminidase mRNA was sub-µg/mL, which is vaccine-relevant, and the average accuracy (%recovery of a check standard) and precision were 104 ± 2% and 9 ± 2%, respectively.

Toll-like receptor (TLR) agonists as a driving force behind next-generation vaccine adjuvants and cancer therapeutics

Until recently, the development of new human adjuvants was held back by a poor understanding of their mechanisms of action. The field was revolutionized by the discovery of the toll-like receptors (TLRs), innate immune receptors that directly or indirectly are responsible for detecting pathogen-associated molecular patterns (PAMPs) and respond to them by activating innate and adaptive immune pathways. Hundreds of ligands targeting various TLRs have since been identified and characterized as vaccine adjuvants. This work has important implications not only for the development of vaccines against infectious diseases but also for immuno-therapies against cancer, allergy, Alzheimer's disease, drug addiction and other diseases. Each TLR has its own specific tissue localization and downstream gene signalling pathways, providing researchers the opportunity to precisely tailor adjuvants with specific immune effects. TLR agonists can be combined with other TLR or alternative adjuvants to create combination adjuvants with synergistic or modulatory effects. This review provides an introduction to the various classes of TLR adjuvants and their respective signalling pathways. It provides an overview of recent advancements in the TLR field in the past 2-3 years and discusses criteria for selecting specific TLR adjuvants based on considerations, such as disease mechanisms and correlates of protection, TLR immune biasing capabilities, route of administration, antigen compatibility, new vaccine technology platforms, and age- and species-specific effects.

Covax-19/Spikogen® vaccine based on recombinant spike protein extracellular domain with Advax-CpG55.2 adjuvant provides single dose protection against SARS-CoV-2 infection in hamsters

COVID-19 presents an ongoing global health crisis. Protein-based COVID-19 vaccines that are well-tolerated, safe, highly-protective and convenient to manufacture remain of major interest. We therefore sought to compare the immunogenicity and protective efficacy of a number of recombinant SARS-CoV-2 spike protein candidates expressed in insect cells. By comparison to a full length (FL) spike protein detergent-extracted nanoparticle antigen, the soluble secreted spike protein extracellular domain (ECD) generated higher protein yields per liter of culture and when formulated with either Alum-CpG55.2 or Advax-CpG55.2 combination adjuvants elicited robust antigen-specific humoral and cellular immunity in mice. In hamsters, the spike ECD when formulated with either adjuvant induced high serum neutralizing antibody titers even after a single dose. When challenged with the homologous SARS-CoV-2 virus, hamsters immunized with the adjuvanted spike ECD exhibited reduced viral load in day 1-3 oropharyngeal swabs and day 3 nasal turbinate tissue and had no recoverable infectious virus in day 3 lung tissue. The reduction in lung viral load correlated with less weight loss and lower lung pathology scores. The formulations of spike ECD with Alum-CpG55.2 or Advax-CpG55.2 were protective even after just a single dose, although the 2-dose regimen performed better overall and required only half the total amount of antigen. Pre-challenge serum neutralizing antibody levels showed a strong correlation with lung protection, with a weaker correlation seen with nasal or oropharyngeal protection. This suggests that serum neutralizing antibody levels may correlate more closely with systemic, rather than mucosal, protection. The spike protein ECD with Advax-CpG55.2 formulation (Covax-19® vaccine) was selected for human clinical development.

Biophysical Characterization of Viral and Lipid-Based Vectors for Vaccines and Therapeutics with Light Scattering and Calorimetric Techniques

Novel vaccine platforms for delivery of nucleic acids based on viral and non-viral vectors, such as recombinant adeno associated viruses (rAAV) and lipid-based nanoparticles (LNPs), hold great promise. However, they pose significant manufacturing and analytical challenges due to their intrinsic structural complexity. During product development and process control, their design, characterization, and quality control require the combination of fit-for-purpose complementary analytical tools. Moreover, an in-depth methodological expertise and holistic approach to data analysis are required for robust measurements and to enable an adequate interpretation of experimental findings. Here the combination of complementary label-free biophysical techniques, including dynamic light scattering (DLS), multiangle-DLS (MADLS), Electrophoretic Light Scattering (ELS), nanoparticle tracking analysis (NTA), multiple detection SEC and differential scanning calorimetry (DSC), have been successfully used for the characterization of physical and chemical attributes of rAAV and LNPs encapsulating mRNA. Methods' performance, applicability, dynamic range of detection and method optimization are discussed for the measurements of multiple critical physical-chemical quality attributes, including particle size distribution, aggregation propensity, polydispersity, particle concentration, particle structural properties and nucleic acid payload.