Skin-patch COVID-19 vaccine could offer enhanced antibody responses, according to preclinical data

Vaxxas’ COVID-19 vaccine is a recombinant SARS-CoV-2 spike glycoprotein, termed HexaPro, which has been stabilized in its prefusion conformation by removal of the furin cleavage site and the inclusion of six stabilizing proline mutations.

According to the preclinical study, vaccination ‘induced enhanced T-cell and spike-specific antibody responses as compared to needle-and-syringe delivery of the same vaccine in an animal model’,​ while the vaccine provided complete protection in a lethal challenge study.

While the vaccine was based on the spike of the Wuhan-Hu-1 reference strain, the authors say serum antibody levels demonstrate the potential to 'potently neutralize' emerging isolates including those from the B.1.1.7 lineage (‘ UK strain’) and B.1.351 lineage (‘South African’) among potentially other strains.

"Based on our results, we believe that Vaxxas’ HD-MAP could offer a compelling solution that importantly could use less vaccine and potentially could be readily distributed without refrigeration for self-administration,”​ said David A. Muller, Advance Queensland Industry Research Fellow, School of Chemistry and Molecular Biosciences, The University of Queensland.

“This combination could make the HD-MAP extremely well suited to support the massive need for global population vaccination and, indeed, we believe that HD-MAP offers a superior alternative to conventional needle-and-syringe.”​

Skin patch potential

Brisbane-headquartered Vaxxas was founded in 2011, setting out with a pipeline of influenza, polio and bacterial infection vaccines.

Its platform uses a high density micro-array patch (HD-MAP), which vaccinates by applying a patch to the skin for a few seconds. It is engineered to directly deposit the vaccine among a dense population of key immune cells in the skin for an ‘efficient and effective immune response’.

Potential advantages of the platform go beyond overcoming a fear of needles. Such vaccines could be self-administered rather than requiring a healthcare setting; while the tech does not require refrigeration. The preclinical study was based on using a single dose, rather than two doses (and studies for other single dose vaccines have required a higher dose than the 2 µg used by Vaxxas).

Another point of interest in the preclinical study was that the same responses were not seen when the same vaccine was delivered via needle-and-syringe with adjuvantation.

“HD-MAP spike vaccines are stable, immunogenic, and protective against virus challenge in mice after a single dose. These finding represent a substantial improvement in many areas of SARS-CoV-2 vaccination and offers a promising alternative to currently available vaccines that warrants further investigation in the context of human SARS15 CoV-2 infection,” ​write the authors in the preprint study.​​

Dry coating tech

The SARS-CoV-2 spike subunit vaccine is dry-coated on the HD-MAP patch using proprietary systems and technology developed by Vaxxas. These dry-coating technologies and potential for self-administration build upon clinical and other demonstration work being done for the United States Biomedical Advanced Research and Development Authority (BARDA) on pandemic influenza vaccination.

The skin-patch tech has also been used in a Phase 1 clinical trial against influenza: where the immune response was shown to be 'significantly higher​​ and have faster onset' than by intramuscular injection at comparable doses.