Inside out: optimization of lipid nanoparticle formulations for exterior complexation and in vivo delivery of saRNA

Abstract

Self-amplifying RNA (saRNA) is a promising biotherapeutic tool that has been used as a vaccine against both infectious diseases and cancer. saRNA has been shown to induce protein expression for up to 60 days and elicit immune responses with lower dosing than messenger RNA (mRNA). Because saRNA is a large (~9500 nt), negatively charged molecule, it requires a delivery vehicle for efficient cellular uptake and degradation protection. Lipid nanoparticles (LNPs) have been widely used for RNA formulations, where the prevailing paradigm is to encapsulate RNA within the particle, including the first FDA-approved small-interfering siRNA therapy. Here, we compared LNP formulations with cationic and ionizable lipids with saRNA either on the interior or exterior of the particle. We show that LNPs formulated with cationic lipids protect saRNA from RNAse degradation, even when it is adsorbed to the surface. Furthermore, cationic LNPs deliver saRNA equivalently to particles formulated with saRNA encapsulated in an ionizable lipid particle, both in vitro and in vivo. Finally, we show that cationic and ionizable LNP formulations induce equivalent antibodies against HIV-1 Env gp140 as a model antigen. These studies establish formulating saRNA on the surface of cationic LNPs as an alternative to the paradigm of encapsulating RNA.

The Long Road Toward COVID-19 Herd Immunity: Vaccine Platform Technologies and Mass Immunization Strategies

“…The first strategy includes an mRNA encoding the RBD of the S protein to induce nAbs ( 19 ), while the second strategy includes an mRNA that instructs the host to produce VLPs ( 19 ). Imperial College London (London, UK) is developing an mRNA COVID-19 vaccine based on prior work with lipid nanoparticle (LNP)-encapsulated self-amplifying RNA, which has previously been shown to induce antibodies against the HIV-1 Env gp140 ( 166 , 167 ). Arcturus Therapeutics (San Diego, CA, USA) in collaboration with Duke National University of Singapore (Singapore) is developing a vaccine candidate using its STARR™ (self-transcribing and replicating RNA) technology platform that combines self-replicating RNA with the nanoparticle delivery system LUNAR® into a single solution for in situ expression of SARS-CoV-2 proteins that induce an anti-viral immune response ( 168 ).…”

Advances in Lipid Nanoparticles for mRNA-Based Cancer Immunotherapy

“…For instance, the immunogenicity of the cationic lipid dimethyldioctadecylammonium (DDA) was illustrated already more than 50 years ago by Gall (Gall, 1966). DDA can act as a vaccine adjuvant, enhancing both cell-mediated and humoral immunity, and it has shown to be effective in different vaccine platforms, including mRNA-based vaccines (Henriksen-Lacey et al, 2010;Blakney et al, 2019). The adjuvant activity of DDA has been attributed to its positive surface charge and its ability to interact and stabilize antigens by ionic interactions.…”

The Current Status of COVID-19 Vaccines

“…modernatx.com). Finally, a first-in-human randomized, placebocontrolled, observer-blind, dose-finding phase I/II clinical trial based on an LNP saRNA vector (Blakney et al, 2019) encoding the SARS-CoV-2 S gene has started in healthy volunteers (ISRCTN17072692). The study will initially include healthy volunteers aged 18-45 years but will later be expanded to 18-75 years old volunteers.…”