The South African trial assessed the safety and immunogenicity of two vaccines candidates – SCOV1 and SCOV2 – in healthy vaccine naïve subjects as well as in the capacity of a booster in pre-vaccinated (or pre-infected) subjects.
The positive data helps validate both Scancell's vaccine tech and the vaccine's delivery with needle-free options, says the Oxford, UK headquartered company.
Data shows potential of tech
SCOV1 and SCOV2 are both plasmid DNA vaccines based on Scancell's ImmunoBody technology and incorporate its AvidiMab modifications to further enhance the immune responses induced following vaccination.
The vaccines were delivered either via intradermal or intramuscular needle-free injection, using Pharma-Jet's Tropis and Stratis systems. These needle-free injection systems deliver a spring-powered injection in one tenth of a second by means of a narrow stream of fluid that penetrates the skin with a precise dose and depth.
“The data from the Phase 1 COVIDITY trial showed that neutralising antibodies were induced, as well as T cell responses to both the receptor binding domain (RBD) of the spike protein and the nucleocapsid antigen (NCAP)," reports Scancell.
"In vaccine-naïve subjects, the seroconversion rate (the level of detectable antibodies in the blood due to vaccination) was 67% following SCOV1/SCOV2 vaccination, with a broad reactivity against multiple COVID-19 variants, including the currently dominant Omicron variant.
“These positive results demonstrate that SCOV1 and SCOV2, delivered via PharmaJet’s needle-free injection device, induce immune responses in naïve participants. Additionally, a single dose of SCOV2 boosted broad responses in previously exposed subjects.”
Proof of concept for novel vaccine technologies
The Board of Scancell have already decided not to take this vaccine forward in house due to the large size of later stage trials and the competitive Covid-19 landscape, but is now seeking a partner to progress the program.
The company adds the positive data demonstrates the validation of the AvidiMab vaccine tech, as well as providing the rationale to incorporate needle-free device in future trials.
Prof Lindy Durrant, Chief Executive Officer, Scancell, said: “These results are highly encouraging. Not only do they provide clinical proof of concept for the COVIDITY COVID-19 vaccine program itself, more broadly they also provide important further validation and learnings for Scancell’s ImmunoBody and AvidiMab platforms.
"The success of a human trial demonstrating that an AvidiMab modified DNA vaccine, delivered via a needle free injection, can induce both T cell and antibody responses, with no safety concerns, is a pivotal proof point for Scancell’s clinical strategy.
“Further large studies would be required to confirm the potential of the COVIDITY vaccine candidates to stimulate broad, cross-variant reactivity and compete with the currently approved COVID-19 vaccines. Therefore, and as previously disclosed, the Board has decided to seek a partner to further progress this program. Going forwards, Scancell will focus its resources on progressing the portfolio of innovative immuno-oncology drug candidates that we have generated from our platforms.”
Scancell and PharmaJet are also partnering on needle-free delivery in a Phase 2 melanoma DNA vaccine trial.
Phase 1 data
The Phase 1 study dosed vaccine naïve subjects with two vaccinations of SCOV1 to demonstrate safety, followed by two vacations of SCOV2 to induce responses against the Beta variant (prevalent in South Africa at the time of the start of the study).
22 participants were dosed with the vaccine either via intradermal or intramuscular needle-free injection. Thirteen of the vaccine-naïve subjects were seronegative at screening (indicating they had not had a previous COVID-19 infection) and nine were seropositive (indicating a previous infection); however, a surge of Omicron infections throughout South Africa resulted in most subjects becoming infected before they could generate a vaccine-specific immune response. However, three seronegative participants completed all four immunisations without becoming infected with COVID-19; two subjects had vaccine-specific T cell responses specific to RBD and/or NCAP, and two had a four-fold increase in RBD neutralising antibodies.
The protocol was amended to include SCOV2 boosting of volunteers who had previously been infected with SARS-CoV-2, irrespective of their vaccination status, or volunteers who were vaccinated but not infected with SARS-CoV-2.
In this cohort, 44 subjects were recruited, 41 of whom were seropositive at screening and, as such, had pre-existing T cell responses specific to RBD and NCAP, with correspondingly high neutralising antibody titres. Following vaccination with SCOV2, 51% of participants who remained COVID-free during the trial showed a further doubling in their RBD-specific T cell response and 26% showed a further doubling of their NCAP-specific T cell response. RBD neutralising antibody titres against the Beta variant doubled in 44% of subjects and NCAP antibody titres doubled in 42% of participants. Of particular interest was that the RBD neutralising antibody responses induced by SCOV2 cross-reacted with the Wuhan (A lineage), Gamma, Delta and Omicron variants.
The responses seen were similar irrespective of the route of administration, both SCOV1 and SCOV2 were well tolerated, there were no severe adverse events reported during the study and the needle-free administration was well received.