1
Title: Interim Report of a Phase 2 Randomized Trial of a Plant-Produced Virus-Like Particle 1
Vaccine for Covid-19 in Healthy Adults Aged 18-64 and Older Adults Aged 65 and Older 2
Authors: Philipe Gobeil
1
, Stéphane Pillet
1
, Annie Séguin
1
,
Iohann Boulay
1
, Asif Mahmood
1
, 3
Donald C Vinh
2
, Nathalie Charland
1
, Philippe Boutet
3
, François Roman
3
, Robbert Van Der 4
Most
4
, Maria de los Angeles Ceregido Perez
3
, Brian J Ward
1,2†
, Nathalie Landry
1†
5
Affiliations:
1
Medicago Inc., 1020 route de l’Église office 600, Québec, QC, Canada, G1V 6
3V9;
2
Research Institute of the McGill University Health Centre, 1001 Decarie St, Montreal, 7
QC H4A 3J1;
3
GlaxoSmithKline Biologicals SA (Vaccines), Avenue Fleming 20, 1300 Wavre, 8
Belgium;
4
GlaxoSmithKline Biologicals SA (Vaccines), rue de l’Institut 89, 1330 Rixensart, 9
Belgium;
†
These individuals are equally credited as senior authors. 10
* Corresponding author: Nathalie Landry, 1020 Route de l’Église, Bureau 600, Québec, Qc, 11
Canada, G1V 3V9; Tel. 418 658 9393; Fax. 418 658 6699; landryn@medicago.com 12
Abstract 13
The rapid spread of SARS-CoV-2 globally continues to impact humanity on a global scale with 14
rising morbidity and mortality. Despite the development of multiple effective vaccines, new 15
vaccines continue to be required to supply ongoing demand. We report Day 42 interim safety 16
and immunogenicity data from a Phase 2, randomized, placebo-controlled trial in Adults aged 17
18+ immunized with a virus-like particle vaccine candidate produced in plants displaying 18
SARS-CoV-2 spike glycoprotein (CoVLP) adjuvanted with AS03 (NCT04636697). This 19
report focuses on presenting safety, tolerability and immunogenicity, as measured by 20
neutralizing antibody (NAb) and cell mediated immunity (IFN-γ and IL-4 ELISpot) responses, 21
in Adults aged 18-64 (Adults) and Older Adults aged 65+ (Older Adults). CoVLP adjuvanted 22
with AS03 was well-tolerated and adverse events (AE) were primarily mild or moderate and of 23
transient duration. AEs in Older Adults were more limited than those observed in the Adult 24
population. CoVLP with AS03 induced a significant humoral immune response in both age 25
cohorts. CoVLP with AS03 induced a greater humoral response in Adults than Older Adults 26
after a single dose but this effect was overcome with a second dose when both age cohorts 27
responded with NAb titers that were ~10-fold higher than those in a panel of sera from patients 28
recovering from COVID-19. A single dose of CoVLP with AS03 induced a significant IFN-γ 29
response in both age cohorts; a second dose significantly boosted IFN-γ and IL-4 responses in 30
both age cohorts. Adults generated a stronger IFN-γ and IL-4 cellular response than did Older 31
Adults after one or two doses of AS03-adjuvanted CoVLP. Safety and immunogenicity from 32
Adults with comorbidities as well as final safety and immunogenicity responses after 12 33
months will be reported upon availability. 34
Keywords:
SARS-CoV-2, Covid-19 vaccine, virus-like particles, Nicotiana benthamiana, 35
Agrobacterium tumefaciens, safety and immunogenicity, neutralizing antibodies, cell-mediated 36
immunity. 37
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted May 17, 2021. ; https://doi.org/10.1101/2021.05.14.21257248doi: medRxiv preprint
NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.
2
Introduction 38
Following a cluster of pneumonia cases in the city of Wuhan in Hubei province of China in 39
December 2019
1
, a novel coronavirus (Severe Acute Respiratory Syndrome Coronavirus 2 40
[SARSCoV-2]) was identified as the causative agent. The disease was subsequently named 41
‘coronavirus disease 2019’, or COVID-19
1,2
. The rapid international spread of COVID-19 42
prompted the World Health Organization (WHO) to declare a pandemic in March 2020
3
. As 43
of May 6
th
, there has been more than 150 million cases of COVID-19 and >3.2 million deaths
4
. 44
This public health emergency sparked a remarkable global effort to develop vaccines using a 45
wide range of traditional and novel platforms including messenger ribonucleic acid (mRNA), 46
deoxyribonucleic acid (DNA), inactivated virus, live viral vectors, recombinant proteins, 47
peptides, or virus-like particles (VLPs)
5,6
. At the time of writing, >60 of these vaccines have 48
entered clinical testing and at least 14 of them have been authorized for use in at least one 49
country. Despite these successes, there remains an urgent global need to approve and distribute 50
further safe and effective vaccines
7
. 51
While it is now clear that humoral immunity is highly correlated with protection
8
, both innate
9-
52
12
and cellular immunity make significant contributions to lasting protection against SARS-53
CoV-2 infection. Passive antibody transfer has proven protective in both non-human primate 54
animal models and in the therapeutic treatment of patients
13-15
. Correlates of protection have 55
recently been proposed for both binding and neutralizing antibody titers
8,16
. Similarly, a clear 56
role for cell-mediated immunity has been suggested for viral clearance and prevention of 57
serious disease, as well as for long-term immunity
14,17-19
. Optimally, SARS-CoV-2 specific 58
vaccines should provide a well-coordinated response involving multiple elements of the 59
immune system. 60
The vaccine candidate developed by Medicago, a Coronavirus-like particle (CoVLP), is a self-61
assembling VLP that displays trimers of recombinant S protein of SARSCoV2 embedded into 62
the lipid bilayer of the nanoparticles. These VLPs are produced in a plant (Nicotiana 63
benthamiana) and closely resemble the native structure of SARS-CoV-2 viruses
20,21
. These 64
plant-produced VLPs lack viral genetic material and can be stored at 2 – 8 °C. Medicago’s 65
vaccine is administered with the oil-in-water Adjuvant System 03 (AS03)
22
. The AS03 initiates 66
a transient innate immune response at the injection site and draining lymph node in animal 67
models
23,24
and in human peripheral blood
10,25,26
. That innate immune response potentiates and 68
shapes the adaptive immune response to the vaccine antigen including both antibody and T-cell 69
responses, resulting in increased response magnitude, breadth, durability, and antibody avidity 70
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
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3
27-29
. AS03 has been used in the licensed pandemic A/H1N1pdm09 influenza vaccines 71
Arepanrix H1N1 (in Canada) and Pandemrix (in Europe), of which 90 million doses have been 72
administered worldwide, as well as in other licensed (Q Pan H5N1 in the USA) or vaccine 73
candidates
30
. In Medicago’s Phase 1 study, AS03 significantly enhanced both cellular and 74
humoral responses to CoVLPs and the vaccine had an acceptable safety profile
21
. 75
Herein we report interim results of the Phase 2 portion of an on-going Phase 2/3 randomized, 76
placebo-controlled study conducted at multiple sites in Canada and the USA. The Phase 2 77
portion of this study was designed to confirm the chosen formulation and dosing regimen (2 78
doses of 3.75 µg CoVLP adjuvanted with AS03 given 21 days apart: hereafter CoVLP+AS03) 79
in adults ≥18 years of age. This report includes responses in healthy adults aged 18-64 80
(Population #1: “Adults”) and in older adults aged 65 years and older (Population #2: “Older 81
Adults”). Analysis of the Phase 2 data for Population #3 (“Adults with Comorbidities”) is 82
underway and will be released once available. Assessment of the efficacy of CoVLP+AS03 in 83
all three adult Populations is currently on-going in the global, Phase 3 portion of the study. 84
85
Results 86
Demographic and baseline clinical characteristics 87
Subjects were screened for SARS-CoV-2 antibodies using a commercial ELISA that targets the 88
nucleocapsid protein (although both seronegative and seropositive subjects were enrolled) and 89
randomized 5:1 to receive CoVLP+AS03 or placebo (saline). 90
Participant demographics are presented in Table 1 and subject disposition is presented in Figure 91
1. The mean ages in Population 1(Adults), were 43.7 years and 42.4 years in vaccinated and 92
placebo groups, respectively. The mean ages in Population 2 (Older Adults), were 71.1 years 93
and 71.7 years in vaccinated and placebo groups, respectively. In all groups, subjects were 94
mostly White or Caucasian (96.7% in Adults, 98.6% in Older Adults). Subject in the Adult and 95
Older Adult populations self-identified as Hispanic or Latino (2.9% and 1.8%), Asian (2.0% 96
and 1.1%) or Black or African American (1.0% or 0%) respectively. Eleven countries are 97
planned for the Phase 3 portion of the Phase 2/3 study to include a more diverse population 98
than that recruited in Phase 2. 99
306 Adults and 282 Older Adults were enrolled in the study. Of the 588 subjects who received 100
a first dose of vaccine, 573 (97.4%) also received their second dose. 101
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted May 17, 2021. ; https://doi.org/10.1101/2021.05.14.21257248doi: medRxiv preprint
4
102
Safety 103
Safety and tolerability data after the first and second doses (as of April 2, 2021) are provided 104
for 306 and 301 subjects in the Adult and for 282 and 272 in the Older Adult groups 105
respectively. Overall, the vaccine was well-tolerated in both populations, with a slightly milder 106
reactogenicity profile in the Older Adults. 107
Reactogenicity is illustrated in Figure 2 for solicited A) local and B) systemic AE. Frequency 108
of solicited AE increased after the second dose relative to the first dose in both age cohorts 109
although Older Adults generally had more muted responses than Adults: 94.5% and 88.4% of 110
Adults reported at least one local AE after the first and second doses respectively compared to 111
61.7% and 54.2% of the Older Adults. In both study populations after the second dose, pain at 112
the injection site was the most frequently reported local AE (89.3% of Adults and 72.8% of 113
Older Adults) while fatigue (67.6% of Adults and 46.1% of Older Adults) and muscle aches 114
(66.0% of Adults and 43.0% of Older Adults) were the most frequently reported systemic AEs. 115
In both populations, the majority of AEs were mild (Grade 1) or moderate (Grade 2) in severity 116
(2.1% and 6.3% of Adults experienced grade 3 AEs after the first and second doses respectively 117
while in Older Adults 0% and 8.7% of participants experienced grade 3 AEs after the first and 118
second doses) and transient, typically resolving within 24 hours to 3 days. No Grade 4 AEs 119
were reported in either study population. No clinically significant laboratory abnormalities, 120
related serious AEs, or cases of Vaccine-Associated Enhanced Disease (VAED), anaphylaxis, 121
or potential immune-mediated disorders monitored as Adverse Events of Special Interest 122
(AESI) have been reported. No pregnancies have been reported to date. 123
124
Immunogenicity: Antibody Response 125
Pseudovirion neutralizing antibody (NAb) responses (based on a data cut-off of April 9
th
, 2021) 126
are illustrated in Figure 3. Relative to both pre-vaccine sera (Baseline) and placebo controls, 127
significant increases were observed in GMTs in both age cohorts at 21 days (D21) after the first 128
dose with further significant increases 21 days after the second dose (D42). 129
A single dose of CoVLP+AS03 induced a four-fold rise in NAb in a larger proportion of the 130
Adults (51.3%, 95CI: 44.7- 57.7) relative to Older Adults (39.6%, 95CI: 32.8- 46.7, p=0.017), 131
an effect also reflected in the D21 GMTs (44.1%, 95CI: 35.7- 54.6 in Adults and 31.1%, 95CI: 132
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5
24.7- 39.1 in Older Adults, p<0.001). This difference between the two age cohorts disappeared 133
with the second dose of CoVLP+AS03 and GMTs were not significantly different at D42 134
(2027, 95CI: 1749- 2350 for Adults and 1956, 95CI: 1526- 2509 in Older Adults, p=0.797). 135
The seroconversion rates were also comparable between the two age cohorts at D42 (99.2%, 136
95CI: 97.0- 99.9 in Adults and 97.7%, 95CI: 93.4- 99.5 in Older Adults, p=0.348). 137
Consistent with observations from the Phase 1 study, the NAb titers elicited by CoVLP+AS03 138
at D42 were approximately 10-fold higher than those observed in a panel of convalescent sera 139
(10.2x in Adults and 9.8x in Older Adults). 140
To assist in standardizing the NAb results, the WHO pooled plasma reference standard 20/136, 141
was included in the pseudovirion NAb assay yielding a reference GMT value of 1872. 142
Expressing the GMT results in International Units (IU/mL), the Adults in our Phase 2 study had 143
NAb values of 23.6 and 1083 IU/mL and the Older Adults had values of 16.6 and 1045 IU/mL 144
after the 1
st
and 2
nd
doses respectively. 145
Prior to vaccination, 9 (1.5%) of the subjects the Phase 2 portion of the study were seropositive 146
at Baseline (6 Adult and 3 Older Adults); all received CoVLP+AS03. At D21, their NAb GMTs 147
were significantly increased in all groups (5756 at D21 relative to 63.9 at D0 in Adults and 148
4909 at D21 relative to 49.6 at D0 in Older Adults). A second dose was only moderately 149
effective in further increasing NAb titers in Older Adults (5786 at D42 in Adults and 10400 at 150
D42 in Older Adults). These data illustrate the potential for CoVLP+AS03 to boost the NAb 151
response even in those presumed to have had prior infection. 152
Overall, CoVLP +AS03 induced comparable NAb responses in both age cohorts. Although 153
small differences between the groups were observed at D21 after the first dose, these 154
differences were overcome by the second dose. 155
156
Immunogenicity: Cell Mediated Response 157
Th
1
- and Th
2
–type cellular responses were assessed by IFN-γ and IL-4 ELISpots in peripheral 158
blood mononuclear cells (PBMC) restimulated with a spike protein peptide pool (Figure 3). 159
These interim data reflect a data cut-off of April 16
th
, 2021. 160
As observed in the Phase 1 study of CoVLP+AS03
21
and previously reported in several studies 161
31,32
, a significant minority (~20%) of individuals were observed to have pre-existing (D0) IFN-162
γ responses to the spike protein. There was no relationship between NAb seropositivity and 163
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