Immunogenicity and safety of a booster dose of a self-amplifying RNA COVID-19 vaccine (ARCT-154) versus BNT162b2 mRNA COVID-19 vaccine: a double-blind, multicentre, randomised, controlled, phase 3, non-inferiority trial

The safety, immunogenicity, and efficacy of heterologous boosting with a SARS-CoV-2 mRNA vaccine (SYS6006) in Chinese participants aged 18 years or more: a randomized, open-label, active-controlled phase 3 trial

Continuous emergence of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), enhanced transmissibility, significant immune escape, and waning immunity call for booster vaccination. We evaluated the safety, immunogenicity, and efficacy of heterologous booster with a SARS-CoV-2 mRNA vaccine SYS6006 versus an active control vaccine in a randomized, open-label, active-controlled phase 3 trial in healthy adults aged 18 years or more who had received two or three doses of SARS-CoV-2 inactivated vaccine in China. The trial started in December 2022 and lasted for 6 months. The participants were randomized (overall ratio: 3:1) to receive one dose of SYS6006 (N = 2999) or an ancestral receptor binding region-based, alum-adjuvanted recombinant protein SARS-CoV-2 vaccine (N = 1000), including 520 participants in an immunogenicity subgroup. SYS6006 boosting showed good safety profiles with most AEs being grade 1 or 2, and induced robust wild-type and Omicron BA.5 neutralizing antibody response on Days 14 and 28, demonstrating immunogenicity superiority versus the control vaccine and meeting the primary objective. The relative vaccine efficacy against COVID-19 of any severity was 51.6% (95% CI, 35.5-63.7) for any variant, 66.8% (48.6-78.5) for BA.5, and 37.7% (2.4-60.3) for XBB, from Day 7 through Month 6. In the vaccinated and infected hybrid immune participants, the relative vaccine efficacy was 68.4% (31.1-85.5) against COVID-19 of any severity caused by a second infection. All COVID-19 cases were mild. SYS6006 heterologous boosting demonstrated good safety, superior immunogenicity and high efficacy against BA.5-associated COVID-19, and protected against XBB-associated COVID-19, particularly in the hybrid immune population.Trial registration: Chinese Clinical Trial Registry: ChiCTR2200066941.

Frameworks for transformational breakthroughs in RNA-based medicines

RNA has sparked a revolution in modern medicine, with the potential to transform the way we treat diseases. Recent regulatory approvals, hundreds of new clinical trials, the emergence of CRISPR gene editing, and the effectiveness of mRNA vaccines in dramatic response to the COVID-19 pandemic have converged to create tremendous momentum and expectation. However, challenges with this relatively new class of drugs persist and require specialized knowledge and expertise to overcome. This Review explores shared strategies for developing RNA drug platforms, including layering technologies, addressing common biases and identifying gaps in understanding. It discusses the potential of RNA-based therapeutics to transform medicine, as well as the challenges associated with improving applicability, efficacy and safety profiles. Insights gained from RNA modalities such as antisense oligonucleotides (ASOs) and small interfering RNAs are used to identify important next steps for mRNA and gene editing technologies.

Safety, immunogenicity and efficacy of the self-amplifying mRNA ARCT-154 COVID-19 vaccine: pooled phase 1, 2, 3a and 3b randomized, controlled trials

Combination of waning immunity and lower effectiveness against new SARS-CoV-2 variants of approved COVID-19 vaccines necessitates new vaccines. We evaluated two doses, 28 days apart, of ARCT-154, a self-amplifying mRNA COVID-19 vaccine, compared with saline placebo in an integrated phase 1/2/3a/3b controlled, observer-blind trial in Vietnamese adults (ClinicalTrial.gov identifier: NCT05012943). Primary safety and reactogenicity outcomes were unsolicited adverse events (AE) 28 days after each dose, solicited local and systemic AE 7 days after each dose, and serious AEs throughout the study. Primary immunogenicity outcome was the immune response as neutralizing antibodies 28 days after the second dose. Efficacy against COVID-19 was assessed as primary and secondary outcomes in phase 3b. ARCT-154 was well tolerated with generally mild-moderate transient AEs. Four weeks after the second dose 94.1% (95% CI: 92.1-95.8) of vaccinees seroconverted for neutralizing antibodies, with a geometric mean-fold rise from baseline of 14.5 (95% CI: 13.6-15.5). Of 640 cases of confirmed COVID-19 eligible for efficacy analysis most were due to the Delta (B.1.617.2) variant. Efficacy of ARCT-154 was 56.6% (95% CI: 48.7- 63.3) against any COVID-19, and 95.3% (80.5-98.9) against severe COVID-19. ARCT-154 vaccination is well tolerated, immunogenic and efficacious, particularly against severe COVID-19 disease.

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.

An Omicron-specific, self-amplifying mRNA booster vaccine for COVID-19: a phase 2/3 randomized trial

Here we conducted a multicenter open-label, randomized phase 2 and 3 study to assess the safety and immunogenicity of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron-specific (BA.1/B.1.1.529), monovalent, thermostable, self-amplifying mRNA vaccine, GEMCOVAC-OM, when administered intradermally as a booster in healthy adults who had received two doses of BBV152 or ChAdOx1 nCoV-19. GEMCOVAC-OM was well tolerated with no related serious adverse events in both phase 2 and phase 3. In phase 2, the safety and immunogenicity of GEMCOVAC-OM was compared with our prototype mRNA vaccine GEMCOVAC-19 (D614G variant-specific) in 140 participants. At day 29 after vaccination, there was a significant rise in anti-spike (BA.1) IgG antibodies with GEMCOVAC-OM (P < 0.0001) and GEMCOVAC-19 (P < 0.0001). However, the IgG titers (primary endpoint) and seroconversion were higher with GEMCOVAC-OM (P < 0.0001). In phase 3, GEMCOVAC-OM was compared with ChAdOx1 nCoV-19 in 3,140 participants (safety cohort), which included an immunogenicity cohort of 420 participants. At day 29, neutralizing antibody titers against the BA.1 variant of SARS-CoV-2 were significantly higher than baseline in the GEMCOVAC-OM arm (P < 0.0001), but not in the ChAdOx1 nCoV-19 arm (P = 0.1490). GEMCOVAC-OM was noninferior (primary endpoint) and superior to ChAdOx1 nCoV-19 in terms of neutralizing antibody titers and seroconversion rate (lower bound 95% confidence interval of least square geometric mean ratio >1 and difference in seroconversion >0% for superiority). At day 29, anti-spike IgG antibodies and seroconversion (secondary endpoints) were significantly higher with GEMCOVAC-OM (P < 0.0001). These results demonstrate that GEMCOVAC-OM is safe and boosts immune responses against the B.1.1.529 variant. Clinical Trial Registry India identifier: CTRI/2022/10/046475 .

Efficient in vitro and in vivo transfection of self-amplifying mRNA with linear poly(propylenimine) and poly(ethylenimine-propylenimine) random copolymers as non-viral carriers

Messenger RNA (mRNA) based vaccines have been introduced worldwide to combat the Covid-19 pandemic. These vaccines consist of non-amplifying mRNA formulated in lipid nanoparticles (LNPs). Consequently, LNPs are considered benchmark non-viral carriers for nucleic acid delivery. However, the formulation and manufacturing of these mRNA-LNP nanoparticles are expensive and time-consuming. Therefore, we used self-amplifying mRNA (saRNA) and synthesized novel polymers as alternative non-viral carrier platform to LNPs, which enable a simple, rapid, one-pot formulation of saRNA-polyplexes. Our novel polymer-based carrier platform consists of randomly concatenated ethylenimine and propylenimine comonomers, resulting in linear, poly(ethylenimine-ran-propylenimine) (L-PEIx-ran-PPIy) copolymers with controllable degrees of polymerization. Here we demonstrate in multiple cell lines, that our saRNA-polyplexes show comparable to higher in vitro saRNA transfection efficiencies and higher cell viabilities compared to formulations with Lipofectamine MessengerMAX™ (LFMM), a commercial, lipid-based carrier considered to be the in vitro gold standard carrier. This is especially true for our in vitro best performing saRNA-polyplexes with N/P 5, which are characterised with a size below 100 nm, a positive zeta potential, a near 100% encapsulation efficiency, a high retention capacity and the ability to protect the saRNA from degradation mediated by RNase A. Furthermore, an ex vivo hemolysis assay with pig red blood cells demonstrated that the saRNA-polyplexes exhibit negligible hemolytic activity. Finally, a bioluminescence-based in vivo study was performed over a 35-day period, and showed that the polymers result in a higher and prolonged bioluminescent signal compared to naked saRNA and L-PEI based polyplexes. Moreover, the polymers show different expression profiles compared to those of LNPs, with one of our new polymers (L-PPI250) demonstrating a higher sustained expression for at least 35 days after injection.

Self-amplifying RNA COVID-19 vaccine

In November 2023, Japan's Ministry of Health, Labour and Welfare granted regulatory approval of ARCT-154, a self-amplifying RNA COVID-19 vaccine developed by Arcturus Therapeutics. Clinical trials showed comparable safety and efficacy using a lower dose compared to the mRNA vaccine BNT162b2. To view this Bench-to-Bedside, open or download the PDF.

Trans-Amplifying RNA: A Journey from Alphavirus Research to Future Vaccines

Replicating RNA, including self-amplifying RNA (saRNA) and trans-amplifying RNA (taRNA), holds great potential for advancing the next generation of RNA-based vaccines. Unlike in vitro transcribed mRNA found in most current RNA vaccines, saRNA or taRNA can be massively replicated within cells in the presence of RNA-amplifying enzymes known as replicases. We recently demonstrated that this property could enhance immune responses with minimal injected RNA amounts. In saRNA-based vaccines, replicase and antigens are encoded on the same mRNA molecule, resulting in very long RNA sequences, which poses significant challenges in production, delivery, and stability. In taRNA-based vaccines, these challenges can be overcome by splitting the replication system into two parts: one that encodes replicase and the other that encodes a short antigen-encoding RNA called transreplicon. Here, we review the identification and use of transreplicon RNA in alphavirus research, with a focus on the development of novel taRNA technology as a state-of-the art vaccine platform. Additionally, we discuss remaining challenges essential to the clinical application and highlight the potential benefits related to the unique properties of this future vaccine platform.

Single-Dose Immunogenic DNA Vaccines Coding for Live-Attenuated Alpha- and Flaviviruses

Single-dose, immunogenic DNA (iDNA) vaccines coding for whole live-attenuated viruses are reviewed. This platform, sometimes called immunization DNA, has been used for vaccine development for flavi- and alphaviruses. An iDNA vaccine uses plasmid DNA to launch live-attenuated virus vaccines in vitro or in vivo. When iDNA is injected into mammalian cells in vitro or in vivo, the RNA genome of an attenuated virus is transcribed, which starts replication of a defined, live-attenuated vaccine virus in cell culture or the cells of a vaccine recipient. In the latter case, an immune response to the live virus vaccine is elicited, which protects against the pathogenic virus. Unlike other nucleic acid vaccines, such as mRNA and standard DNA vaccines, iDNA vaccines elicit protection with a single dose, thus providing major improvement to epidemic preparedness. Still, iDNA vaccines retain the advantages of other nucleic acid vaccines. In summary, the iDNA platform combines the advantages of reverse genetics and DNA immunization with the high immunogenicity of live-attenuated vaccines, resulting in enhanced safety and immunogenicity. This vaccine platform has expanded the field of genetic DNA and RNA vaccines with a novel type of immunogenic DNA vaccines that encode entire live-attenuated viruses.