BackgroundSeveral COVID-19 vaccines are currently being deployed but supply constraints, concerns over durability of immune responses, solidifying vaccine hesitancy/resistance and vaccine efficacy in the face of emerging variants mean that new vaccines continue to be needed to fight the ongoing pandemic. The vaccine described here is an enveloped, coronavirus-like particle produced in plants (CoVLP) that displays the prefusion-stabilized spike (S) glycoprotein of SARS-CoV-2 (ancestral Wuhan strain) and is adjuvanted with AS03 (CoVLP+AS03). MethodsThis Phase 3 randomized, observer-blind, placebo-controlled trial was conducted at 85 centers in Argentina, Brazil, Canada, Mexico, the UK, and the USA. Adults [≥]18 years of age including those at high risk for COVID-19 complications were randomly assigned 1:1 to receive two intramuscular injections of CoVLP (3.75 g) adjuvanted with AS03 or placebo, 21 days apart. The primary efficacy endpoint was prevention of symptomatic ([≥] 1 symptom), PCR-confirmed SARS-CoV-2 infection with onset at least 7 days after the second injection and was triggered by the identification of [≥]160 virologically-confirmed cases. Tolerability and safety of CoVLP+AS03 were also determined. ResultsA total of 24,141 volunteers were randomly assigned 1:1 to receive vaccine or placebo (N= 12,074 and 12,067, respectively: median age 29, range 18 to 86 years). Overall, 83% received both doses. 14.8% were SARS-CoV-2 seropositive at baseline. Symptomatic SARS-CoV-2 infection was confirmed in 165 study participants in the intention to treat (ITT) set and 157 in the per-protocol population (PP) set. Of the 157 in the PP set, 118 COVID-19 cases were in the placebo group and 39 COVID-19 cases were in the CoVLP+AS03 group for an overall vaccine efficacy (VE) of 71.0% (95% confidence interval (CI) 58.6, 80.0). Moderate-to-severe COVID-19 occurred in 8 and 32 participants in the CoVLP+AS03 and placebo groups, respectively: VE 78.1% (95% CI: 53.9, 90.5) in the PP set overall and 84.5% (95% CI: 62.0, 94.7) in those seronegative at recruitment. To date, 100% of the sequenced strains (122/165 cases: 73.39%) were variants, dominated by Delta (45.9%) and Gamma (43.4%) strains. Vaccine efficacy by variant was 75.3% (95% CI 52.8, 87.9) against Delta and 88.6% (95% CI 74.6, 95.6) against Gamma. Cross-protection was also observed against Alpha, Lambda and Mu variants; although fewer cases were identified, all were in the placebo group. At diagnosis, viral loads in the CoVLP+AS03 breakthrough cases were >100-fold lower than in the placebo cases. Reactogenicity data for solicited adverse events (AEs) was analysed for a subset (N=4,136 in vaccine arm and N=3,683 for placebo) of participants. Reactogenicity was mostly mild to moderate, and transient, and occurred more frequently in the CoVLP+AS03 group. The safety analysis set used for unsolicited AE assessment comprised 24,076 participants who received at least one study injection: 12,036 received CoVLP+AS03 and 12,040 received placebo. All serious adverse events were assessed as unrelated, except two events reported in the same subject in the placebo group. No significant imbalance or safety concern was noted in medically attended AEs (MAAEs), adverse event of special interest (AESIs), AEs leading to withdrawal, deaths, or adverse events potentially associated with currently authorized vaccines. ConclusionsThe CoVLP+AS03 vaccine candidate conferred an efficacy of 71.0% in preventing symptomatic SARS-CoV-2 infection caused by a spectrum of variants. Vaccine efficacy of 78.1% was observed against moderate and severe disease, while variant-specific efficacy ranged from 75.3% to 100%. Markedly lower viral loads in the CoVLP+AS03 group at the time of diagnosis suggests a significant virologic impact of vaccination even in the breakthrough cases. CoVLP+AS03 vaccine candidate was well tolerated, and no safety concerns were identified during the study. If approved by regulators, this more traditional protein+adjuvant vaccine produced using the novel plant-based platform may be able to make an important contribution to the global struggle against the increasingly complex family of SARS-CoV-2 viruses (Funded by Medicago with grants from the governments of Quebec and Canada; NCT04636697).
Although antivirals are important tools to control the SARS-CoV-2 infection, effective vaccines are essential to control the current pandemic. Plant-derived virus-like particle (VLP) vaccine candidates have previously demonstrated immunogenicity and efficacy against influenza. Here we report the immunogenicity and protection induced in macaques by intramuscular injections of VLP bearing SARS-CoV-2 spike protein (CoVLP) vaccine candidate formulated with or without Adjuvant System 03 (AS03) or cytosine phosphoguanine (CpG) 1018. Although a single dose of unadjuvanted CoVLP vaccine candidate stimulated humoral and cell-mediated immune responses, booster immunization (at 28 days after prime) and adjuvants significantly improved both responses with a higher immunogenicity and protection provided by AS03 adjuvanted CoVLP. Fifteen microgram CoVLP adjuvanted with AS03 induced a balanced IL-2 driven response along with IL-4 expression in CD4 T cells and mobilization of CD4 follicular helper cells (Tfh). Animals were challenged by multiple routes (i.e. intratracheal, intranasal and ocular) with a total viral dose of 106 plaque forming units of SARS-CoV-2. Lower viral replication in nasal swabs and broncho-alveolar lavage (BAL) as well as fewer SARS-CoV-2 infected cells and immune cell infiltrates in the lungs concomitant with reduced levels of pro-inflammatory cytokines and chemotactic factors in BAL were observed in the animals immunized with CoVLP adjuvanted with AS03. No clinical, pathologic or virologic evidences of vaccine associated enhanced disease (VAED) were observed in vaccinated animals. CoVLP adjuvanted with AS03 was therefore selected for vaccine development and clinical trials.
The rapid spread of SARS-CoV-2 continues to impact humanity on a global scale with rising total morbidity and mortality. Despite the development of several effective vaccines, new products are needed to supply ongoing demand and the needs of specific populations. We report herein a pre-specified interim analysis of the phase 2 portion of an ongoing Phase 2/3, randomized, placebo-controlled trial of a coronavirus virus-like particle (CoVLP) vaccine candidate produced in plants that displays the SARS-CoV-2 spike glycoprotein adjuvanted with AS03 (NCT04636697). A total of 753 subjects were recruited between 25 November 2020 and 24 March 2021 into three groups: Healthy Adults (18-64 years: N=306), Older Adults ([≥] 65 years: N=282) and Adults with Comorbidities ([≥]18 years: N=165) and randomized 5:1 to receive two intramuscular doses of either vaccine CoVLP (3.75 g/dose + AS03) or placebo 21 days apart. This report presents safety, tolerability and immunogenicity data collected up to 21 days after the second dose. The immune outcomes presented include neutralizing antibody (NAb) titres and cellular (IFN-{gamma} and IL-4 ELISpot) responses. In this study, CoVLP+AS03 was well-tolerated and adverse events (AE) after each dose were generally mild to moderate and transient. Solicited AEs in Older Adults and Adults with Comorbidities were generally less frequent than in Healthy Adults. CoVLP+AS03 induced seroconversion in >35% of subjects in each group after the first dose and in [~]98% of subjects 21 days after the second dose. In all treatment groups, NAb levels were [~]10-fold higher than those in a panel of convalescent sera. A significant minority ([~]20%) of subjects had evidence of a pre-existing IFN-{gamma} response to the S protein and almost all subjects in all groups (>88%) had detectable cellular responses (IFN-{gamma}, IL-4 or both) at 21 days after the second dose. A Th1-biased response was most evident after the first dose and was still present after dose two. These data demonstrated that CoVLP+AS03 will likely be well-tolerated and highly immunogenic in adults [≥]18 years of age with and without comorbidities.
Longer AbstractO_ST_ABSBackgroundC_ST_ABSThe stabilized prefusion form of the SARS-CoV-2 spike protein is produced by transient expression in Nicotiana benthamiana. The trimeric spike glycoproteins are displayed at the surface of self-assembling Virus-Like-Particles that mimic the shape and the size of the virus. The candidate vaccine (CoVLP) administered alone or with AS03 or CpG1018 adjuvants was evaluated in a Phase 1 trial in healthy adults. (ClinicalTrials.gov number NCT04450004) MethodsThe study was a randomized, partially-blinded, prime-boost 21 days apart, dose-escalation Phase 1 study intended to assess the safety, tolerability, and immunogenicity of CoVLP at three dose levels (3.75 {micro}g, 7.5 {micro}g, and 15 {micro}g) unadjuvanted or adjuvanted with either CpG 1018 or AS03 in 180 SARS-CoV-2 seronegative healthy adults 18 to 55 years of age. Enrollment was staggered for dose-escalation. At each dose level, the vaccine was initially administered to a small number of subjects. Vaccination of the remaining subjects at the same dose level and the next higher vaccine dose level was administered with approval of an Independent Data Monitoring Committee (IDMC). The same procedure was followed for the second vaccine administration. Monitoring of safety signals was performed throughout the study with pre-determined pausing/stopping rules if there was clear evidence of harmful effects such as severe adverse events (AEs) related to the treatment. The primary endpoints were the safety and tolerability of the vaccine after each dose and the immunogenicity as assessed by neutralizing antibody responses assessed using a vesicular stomatitis virus (VSV) pseudovirion assay and interferon-gamma (IFN-{gamma}) and interleukin-4 (IL-4) ELISpot assays at Days 0, 21 and 42. Secondary endpoints were anti-spike antibody responses by ELISA and neutralizing antibodies measured by live virus plaque reduction neutralization test (PRNT) assay at Days 0, 21 and 42 and immunogenicity with additional safety and immunogenicity endpoints planned for 6-months following the last vaccination. The anti-spike and neutralizing antibody responses were compared with 23 convalescent serum samples from symptomatic Covid-19 patients. We performed a primary analysis at day 42. ResultsA total of 180 subjects (102 females: 78 males: average 34.3 years) were recruited to the study and interim safety and immunogenicity data up to day 42 after the first dose are reported here. There was no obvious CoVLP dose effect in safety outcomes for any of the formulations tested and all formulations were generally well-tolerated. Most solicited local and systemic AEs were mild-moderate and transient. Reactogenicity was increased in all adjuvanted formulations and was generally highest in the CoVLP+AS03 groups. Local and systemic adverse events were reported with similar frequency after the first and second doses in subjects who received either CoVLP alone or CoVLP+CpG1018 but increased in both frequency and severity after the second dose in the CoVLP+AS03 groups. CoVLP alone only elicited a weak total anti-spike IgG response at the highest dose level and little-to-no neutralization antibody response, even after the second dose. Cellular responses in the CoVLP alone groups (IFN{gamma} and IL-4) were detectable after the second dose but were still only marginally above background levels. The addition of either adjuvant substantially increased both antibody and cellular responses at most CoVLP dose levels and changes were most pronounced after the second dose. However, a substantial neutralizing antibody response after the first dose was only seen in all CoVLP+AS03 groups. After the second dose, both total anti-spike IgG and neutralizing antibody titers in the CoVLP+AS03 groups were higher than those in the CoVLP+CpG1018 groups. The antibody titers achieved were either similar to (CoVLP+CpG1018) or at least 10-times higher (CoVLP+AS03) than those seen in convalescent plasma. Administration of CoVLP with either adjuvant also significantly increased the cellular responses. After 2 doses, both IFN-{gamma} and IL-4 responses were significantly increased in the CoVLP+CpG1018 groups. In the CoVLP+AS03 groups, significant increases in the cellular responses were observed after the first dose while IFN-{gamma} and IL-4 increased further in both magnitude and number of subjects responding after the second dose. Again, the cellular responses in the CoVLP+AS03 groups were higher than those seen in the CoVLP+CpG1018 groups. ConclusionThese data demonstrate that CoVLP administered with either CpG1018 or AS03 has a safety profile similar to other candidate vaccines for SARS-CoV-2. When administered with either AS03 or CpG1018, several of the CoVLP dose levels elicited strong humoral and T cell responses after the second dose. When administered with AS03, even the 3.75 g CoVLP dose elicited neutralizing antibody titers that were [~]10-times higher than those observed in individuals recovering from Covid-19 as well as consistent and balanced IFN-{gamma} and IL-4 responses. Although many CoVLP formulations were immunogenic, in the absence of established correlates of protection and given the advantages of dose-sparing in the context of the on-going pandemic, these findings suggest that CoVLP (3.75 g)+AS03 has a good benefit/risk ratio and support the transition of this formulation to studies in expanded populations and to efficacy evaluations Shorter AbstractO_ST_ABSBackgroundC_ST_ABSVirus-like particles (VLP) displaying recombinant SARS-CoV-2 spike protein trimers were produced by transient expression in Nicotiana benthamiana. This candidate vaccine (CoVLP) was evaluated in healthy adults 18-55 years of age alone or with AS03 or CpG1018 (NCT04450004). MethodsThis randomized, partially-blinded, two-dose, dose-escalation study assessed CoVLP (3.75, 7.5 or 15 {micro}g/dose) administered intramuscularly alone or with CpG1018 or AS03 in SARS-CoV-2 seronegative adults (18-55 years). Primary endpoints of safety and immunogenicity are reported to day 42. Neutralizing antibodies (NtAb) were assessed using a VSV pseudovirus assay and cellular responses by ELISpot (IFN{gamma}, IL-4). Results180 subjects (avg.34.3yrs) were recruited. All formulations were well-tolerated but adjuvants increased reactogenicity. Adverse events were highest in the CoVLP+AS03 groups and increased in frequency/severity after dose two. CoVLP alone elicited weak humoral responses but modest cellular responses were detectable after dose two. Both adjuvants increased immunogenicity significantly, particularly after dose two. A significant NtAb response after dose one was only seen in CoVLP+AS03 groups. The vaccine dose had little impact on levels of NtAb responses achieved in the CoVLP+AS03 groups. Both adjuvants also increased IFN{gamma} and IL-4 responses but these cellular responses also tended to be highest in the AS03-adjuvanted groups. ConclusionCoVLP {+/-} adjuvants was well-tolerated. Several adjuvanted formulations elicited strong humoral and T cell responses after dose 2. Even at the lowest CoVLP+AS03 dose, NtAb titers were [~]10-times higher than in convalescent serum with a balanced IFN{gamma} and IL-4 response. These findings support the transition of CoVLP (3.75g+AS03) to further clinical evaluation. Research In ContextO_ST_ABSEvidence before this studyC_ST_ABSThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was recognized as the causative agent of COVID-19 in early 2020. Since that time, >150 candidate vaccines are reported to be under development of which 47 have entered clinical trials (https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines accessed Nov 4, 2020). No vaccine to prevent COVID-19 has been licensed yet for either emergency or general use in North America or Europe. We searched PubMed for research articles published between July 2019 and November 4, 2020, using the terms "SARS-CoV-2", "vaccine", "clinical trial" OR "human", AND "phase". The same terms were used to search ClinTrials.gov. No language restrictions were applied. We identified 10 peer-reviewed studies, describing phase 1 or 1/2 trials using a range of novel (eg: RNA, DNA, non-replicating virus vectored) and more traditional vaccine approaches (eg: inactivated virus or recombinant protein {+/-} adjuvants). None of these candidate vaccines was produced in plants. These reports demonstrate that several different vaccination strategies (typically delivered in two doses 14-28 days apart) are capable of eliciting neutralizing antibody responses. In several cases, vaccine-induced cellular responses against SARS-COV-2 antigens - predominantly the spike (S) protein - can also be demonstrated. Although local and systemic adverse events following vaccination have varied between reports, the trials published to date suggest that each of these candidate vaccines is well-tolerated in the context of an evolving pandemic. Added value of this studyWe report the results of the first clinical study of CoVLP, a virus-like particle (VLP) vaccine that is produced by transient transfection of Nicotiana benthamiana plants. These VLPs spontaneously assemble at the plant cell membrane and display SARS-COV-2 trimers of stabilized pre-fusion S protein on their surface. The vaccine was administered as two intramuscular doses 21 days apart at three dose levels (S protein content 3.75, 7,5 or 15g) alone or adjuvanted with either CpG1018 or AS03. All formulations were well-tolerated although both adjuvants increased reactogenicity. Humoral (anti-S IgG and neutralizing antibodies) as well as cellular responses (IFNg and IL4 ELISpots) were detectable in almost all subjects who received adjuvanted formulations 21 days after the second dose at all COVLP dose levels. Both antibody and cellular responses were highest in subjects who received AS03-adjuvanted formulations. Even at the lowest dose level (3.75g), the neutralizing antibody titers 21 days after the second dose in subjects who received the AS03-afdjuvanted vaccine were 10-50-fold higher than those seen in subjects recovering from COVID-19 infection. Implications of all the available evidenceEffective vaccines against SARS-CoV-2 are urgently needed to reduce the burden of disease and contribute to ending the global pandemic. Although no immune correlates for SARS-CoV-2 have been defined, it is likely that both arms of the immune system contribute to protection. After two doses of CoVLP (3.75g+AS03), strong humoral and cellular responses were induced supporting the further clinical development of this vaccine.
