Safety and immunogenicity of INO-4800 DNA vaccine against SARS-CoV-2: A preliminary report of an open-label, Phase 1 clinical trial

Abstract

Background: A vaccine against SARS-CoV-2 is of high urgency. Here the safety and immunogenicity induced by a DNA vaccine (INO-4800) targeting the full length spike antigen of SARS-CoV-2 are described.

Methods: INO-4800 was evaluated in two groups of 20 participants, receiving either 1.0 mg or 2.0 mg of vaccine intradermally followed by CELLECTRA® EP at 0 and 4 weeks. Thirty-nine subjects completed both doses; one subject in the 2.0 mg group discontinued trial participation prior to receiving the second dose. ClinicalTrials.gov identifier: NCT04336410.

Findings: The median age was 34.5, 55% (22/40) were men and 82.5% (33/40) white. Through week 8, only 6 related Grade 1 adverse events in 5 subjects were observed. None of these increased in frequency with the second administration. No serious adverse events were reported. All 38 subjects evaluable for immunogenicity had cellular and/or humoral immune responses following the second dose of INO-4800. By week 6, 95% (36/38) of the participants seroconverted based on their responses by generating binding (ELISA) and/or neutralizing antibodies (PRNT IC50), with responder geometric mean binding antibody titers of 655.5 [95% CI (255.6, 1681.0)] and 994.2 [95% CI (395.3, 2500.3)] in the 1.0 mg and 2.0 mg groups, respectively. For neutralizing antibody, 78% (14/18) and 84% (16/19) generated a response with corresponding geometric mean titers of 102.3 [95% CI (37.4, 280.3)] and 63.5 [95% CI (39.6, 101.8)], in the respective groups. By week 8, 74% (14/19) and 100% (19/19) of subjects generated T cell responses by IFN-ɣ ELISpot assay with the median SFU per 106 PBMC of 46 [95% CI (21.1, 142.2)] and 71 [95% CI (32.2, 194.4)] in the 1.0 mg and 2.0 mg groups, respectively. Flow cytometry demonstrated a T cell response, dominated by CD8+ T cells co-producing IFN-ɣ and TNF-α, without increase in IL-4.

Interpretation: INO-4800 demonstrated excellent safety and tolerability and was immunogenic in 100% (38/38) of the vaccinated subjects by eliciting either or both humoral or cellular immune responses.

Funding: Coalition for Epidemic Preparedness Innovations (CEPI).

Keywords: COVID-19; DNA vaccine; INO-4800; Phase 1; SARS-CoV-2.

Conflict of interest statement

SY, JDB, ACQ, VMA, MPM, KK, JA, AS, JP, EG, IM, PP, KS, TRFS, SR, TMcM, MD, EB, MPM, JL, MD, ASB, JES, JJK, KEB and LMH report grants from Coalition for Epidemic Preparedness Innovations, during the conduct of the study; other from Inovio Pharmaceuticals, outside the submitted work. PT, ELR, AP, MP, FIZ, KYK, YD, DF, KB, MWC, JE and DBW report grants from Coalition for Epidemic Preparedness Innovations, during the conduct of the study.

Crown Copyright © 2020 Published by Elsevier Ltd.

Figures

Fig. 1

Consort flow diagram. *One subject in the 2.0 mg dose group was not able to secure consistent transportation and therefore discontinued.

Fig. 2

Related systemic and local adverse events in severity of mild (Grade 1), moderate (Grad 2), severe (Grade 3) and life-threatening (Grade 4).

Fig. 3

Humoral antibody response. The humoral response in the 1.0 mg dose group and 2.0 mg dose group was assessed for the ability to A) neutralize of live virus, (n = 18, 1.0 mg; n = 19, 2.0 mg). B) and binding to whole spike protein (S1 and S2) (n = 19, 1.0 mg; n = 19, 2.0 mg). End point titers for binding antibodies were calculated as the titer that exhibited an OD 3.0 SD above baseline, titers at baseline were set at 1 to normalize the post-baseline results. A response to live virus neutralization was a PRNT IC50 ≥ 10. In all graphs horizontal lines represent the Median and bars represent the Interquartile.

Fig. 4

Cellular immune response: PBMCs isolated from vaccinated individuals were stimulated in vitro with SARS-CoV-2 spike antigen. The number of cells capable of secreting IFN-gamma were measured in a standard ELISpot assay for the A) 1.0 mg dose group and 2.0 mg dose group. Horizontal lines represent Medians and bars represent Interquartile Ranges. B) Peptides spanning the entirety of the spike antigen were divided into pools and tested individually in ELISpot, with pools mapped to specific regions of the antigen represented by color. Three subjects are shown exemplifying the diversity of pool responses and associated magnitude across subjects. The pie chart represents the diversity of entirety of the 2.0 mg dose group C) A heat map of each subject in the 2.0 mg dose group and the percentage of their ELISpot response dedicated to each pool covering the SARS-CoV-2 spike antigen. D) SARS-CoV-2 spike specific cytokine production was measured from CD4+ and CD8+ T cells via flow cytometry. Bars represent Mean response. E) Cytokine production is additionally broken out using CCR7 and CD45RA into Central Memory (CM), Effector Memory (EM) or Effector (E) differentiation status with data conveying what percentage of the overall cytokine response originates from what differentiated group. F) Pie charts represent the polyfunctionality of CD4+ and CD8+ T cells for each dose cohort. G) IL-4 production by CD4+ T cells for each dose cohort. Horizontal lines represent Mean response. Graphs represent all evaluable subjects. Statistical analyses were performed on all paired datasets. Those that were significant are noted within the figure; lack of notation in the figure represents lack of statistical significance.