Arcturus Therapeutics Publications

Early T cell and binding antibody responses are associated with COVID-19 RNA vaccine efficacy onset

RNA vaccines have shown efficacy in preventing coronavirus disease 2019 (COVID-19) as early as 12 days after the first dose. Vaccine efficacy onset presents a unique opportunity to define the necessary elements of immunity against COVID-19. Kalimuddin et al. tracked the serological and T cell responses longitudinally in 20 healthcare workers after the first Pfizer/BioNTech BNT162b2 vaccine dose. Anti-spike immunoglobulin G (IgG) and IgA antibodies and spike-specific T cells were detectable at day 10 after the first dose; neutralizing and receptor-blocking antibodies remained mostly undetectable at this time point. These results suggest that binding antibodies and T cell responses are responsible for early protection against COVID-19 and call for circumspection on the prevailing notion that neutralizing antibodies are absolutely required for protection.

A single dose of self-transcribing and replicating RNA-based SARS-CoV-2 vaccine produces adaptive immunity in mice

A self-transcribing and replicating RNA (STARR)-based vaccine (LUNAR-COV19) has been developed to prevent SARS-CoV-2 infection. The vaccine encodes an alphavirus-based replicon and the SARS-CoV-2 full-length spike glycoprotein. Translation of the replicon produces a replicase complex that amplifies and prolongs SARS-CoV-2 spike glycoprotein expression. A single prime vaccination in mice led to robust antibody responses, with neutralizing antibody titers increasing up to day 60. Activation of cell-mediated immunity produced a strong viral antigen-specific CD8+ T lymphocyte response. Assaying for intracellular cytokine staining for interferon (IFN)g and interleukin-4 (IL-4)-positive CD4+ T helper (Th) lymphocytes as well as anti-spike glycoprotein immunoglobulin G (IgG)2a/IgG1 ratios supported a strong Th1-dominant immune response. Finally, single LUNAR-COV19 vaccination at both 2 µg and 10 µg doses completely protected human ACE2 transgenic mice from both mortality and even measurable infection following wild-type SARS-CoV-2 challenge. Our findings collectively suggest the potential of LUNAR-COV19 as a single-dose vaccine.

A Single Dose of Self-Transcribing and Replicating RNA Based SARS-CoV-2 Vaccine Produces Protective Adaptive Immunity In Mice

A self-transcribing and replicating RNA (STARR™) based vaccine (LUNAR® 36 -COV19) has been developed to prevent SARS-CoV-2 infection. The vaccine encodes an alphavirus-based replicon and the SARS-CoV-2 full length spike glycoprotein.

mRNA Therapy For Ornithine Transcarbamylase Deficiency

LUNAR®-OTC treats patients suffering from ornithine transcarbamylse deficiency (OTCD) using mRNA to replace the wild-type human enzyme. OTCD is a rare metabolic disease in which the urea cycle cannot efficiently convert ammonia into urea. The efficacy of LUNAR®-OTC was evaluated in an animal model of OTCD ameliorating certain OTCD disease phenotypes in mice.

LUNAR®-CF, an aerosolized mRNA replacement Therapy for Cystic Fibrosis Lung Disease

LUNAR®-CF is an aerosolized mRNA replacement therapy to treat Cystic Fibrosis (CF) Lung Disease, a therapeutic approach agnostic to a patient’s genotype. A healthy copy of the human CFTR mRNA is encapsulated into lipid nanoparticles (LUNAR®-hCFTR), aerosolized to patient’s airways using a vibrating mesh nebulizer to directly deliver a de novo human CFTR mRNA into epithelial cells. This human CFTR mRNA encodes a fully functional human CFTR protein that will be beneficial to facilitate mucociliary clearance and improve CF lung disease.

LUNAR® selective delivery of nebulized mRNA into murine lung epithelial cells

LUNAR® lipid nanoparticles carrying the mRNA payload reaches the target cell, where it fuses with the plasma membrane forming an intracellular endosome. This endosomic particle undergoes a pH-mediated disruption that causes the breakdown of the biodegradable nanoparticle and the delivery of the mRNA into the cytoplasm.

LUNAR-CF a mRNA Replacement Therapy for Cystic Fibrosis

Arcturus Therapeutics is a nucleic acid medicines company focused on developing RNA therapeutics to treat rare diseases. Our proprietary LUNAR® lipid-mediated delivery technology enables the efficient delivery of any mRNA into a variety of cell types and tissues, and can be optimized for multiple routes of administration.

Selective suppression of polyglutamine-expanded protein by lipid nanoparticle-delivered siRNA targeting CAG expansions in the mouse CNS

Polyglutamine (polyQ) diseases are inherited neurodegenerative disorders caused by expansion of cytosine-adenine-guanine (CAG)-trinucleotide repeats in causative genes. These diseases include spinal and bulbar muscular atrophy (SBMA), Huntington’s disease, dentatorubral-pallidoluysian atrophy, and spinocerebellar ataxias. Targeting expanded CAG repeats is a common therapeutic approach to polyQ diseases, but concomitant silencing of genes with normal CAG repeats may lead to toxicity. Previous studies have shown that CAG repeat-targeting small interfering RNA duplexes (CAG-siRNAs) have the potential to selectively suppress mutant proteins in in vitro cell models of polyQ diseases. However, in vivo application of these siRNAs has not yet been investigated. In this study, we demonstrate that an unlocked nucleic acid (UNA)- modified CAG-siRNA shows high selectivity for polyQ expanded androgen receptor (AR) inhibition in in vitro cell models and that lipid nanoparticle (LNP)-mediated delivery of the CAG-siRNA selectively suppresses mutant AR in the central nervous system of an SBMA mouse model. In addition, a subcutaneous injection of the LNP-delivered CAG-siRNA efficiently suppresses mutant AR in the skeletal muscle of the SBMA mouse model. These results support the therapeutic potential of LNP-delivered UNA-modified CAG-siRNAs for selective suppression of mutant proteins in SBMA and other polyQ diseases.

CD8+ T cells mediate protection against Zika virus induced by an NS3-based vaccine

Zika virus (ZIKV) is associated with congenital malformations in infants born to infected mothers, and with Guillain-Barré syndrome in infected adults. Development of ZIKV vaccines has focused predominantly on the induction of neutralizing antibodies, although a suboptimal antibody response may theoretically enhance disease severity through antibody-dependent enhancement (ADE). Here, we report induction of a protective anti-ZIKV CD8+ T cell response in the HLA-B*0702 Ifnar1-/- transgenic mice using an alphavirus-based replicon RNA vaccine expressing ZIKV nonstructural protein NS3, a potent T cell antigen. The NS3 vaccine did not induce a neutralizing antibody response but elicited polyfunctional CD8+ T cells that were necessary and sufficient for preventing death in lethally infected adult mice and fetal growth restriction in infected pregnant mice. These data identify CD8+ T cells as the major mediators of ZIKV NS3 vaccine-induced protection and suggest a new strategy to develop safe and effective anti-flavivirus vaccines.

Property Driven Design and Development of Lipids for Efficient Delivery of siRNA

Ionizable cationic lipids are critical components involved in nanoparticle formulations, which are utilized in delivery platforms for RNA therapeutics. While general criteria regarding lipophilicity and measured pKa in formulation are understood to have impacts on utility in vivo, greater granularity with respect to the impacts of the structure on calculated and measured physicochemical parameters and the subsequent performance of those ionizable cationic lipids in in vivo studies would be beneficial.

Lipid Nanoparticle Formulation Increases Efficiency of DNA-Vectored Vaccines/Immunoprophylaxis in Animals Including Transchromosomic Bovines

The use of nucleic acid as a drug substance for vaccines and other gene-based medicines continues to evolve. Here, we have used a technology originally developed for mRNA in vivo delivery to enhance the immunogenicity of DNA vaccines. We demonstrate that neutralizing antibodies produced in rabbits and nonhuman primates injected with lipid nanoparticle (LNP)-formulated Andes virus or Zika virus DNA vaccines are elevated over unformulated vaccine.

Anti-HFRS Human IgG Produced in Transchromosomic Bovines Has Potent Hantavirus Neutralizing Activity and Is Protective in Animal Models

We explored an emerging technology to produce anti-Hantaan virus (HTNV) and anti-Puumala virus (PUUV) neutralizing antibodies for use as pre- or post-exposure prophylactics.

Challenges and Potential Solutions for Development of Successful Potency Assay in mRNA Therapeutics

mRNA Therapeutics require development of potency assays early during the pre-clinical stage. Conventional potency methods for protein biologic may not apply directly to mRNA therapeutic drug substance. Cell-based potency assays have to be carefully evaluated to make sure that the read-outs correspond to the actual potency of the drug substance and not an artifactual value. mRNAs can be evaluated for potency at level of protein expression (cell-free), cellular protein expression/stability and enzyme activity in vitro.

Systemic delivery of factor IX messenger RNA for protein replacement therapy

Safe and efficient delivery of messenger RNAs for protein replacement therapies offers great promise but remains challenging. In this report, we demonstrate systemic, in vivo, nonviral mRNA delivery through lipid nanoparticles (LNPs) to treat a Factor IX (FIX)-deficient mouse model of hemophilia B.