US-based Altimmune has reported that additional preclinical data on its single dose intranasal Covid-19 vaccine candidate, AdCOVID, showed 100% protection against lethal challenge from the SARS-CoV-2 virus, and reduction in viral replication.
The preclinical studies were undertaken at University of Alabama at Birmingham and Saint Louis University, which are collaborating institutions of the clinical-stage biopharmaceutical firm.
According to the data derived through the K18-hACE2 transgenic mouse model, a single intranasal dose of AdCOVID offered complete protection against SARS-CoV-2 virus. All animals survived and showed no weight loss.
The studies were carried out in the laboratories of James Brien, and Amelia Pinto in the Department of Molecular Microbiology & Immunology at Saint Louis.
Initial analysis of immunogenicity indicated mean antibody levels of about 1 mg/mL. This in turn showed that the serum IgG antibody response against the spike protein was strong and similar to that reported by the company earlier.
According to a separate study carried out with the same animal model in the laboratory of Dr Frances Lund at the University of Alabama, a single intranasal dose of AdCOVID showed a greater than 1000-fold cut down in replicating virus in the nasal cavity and respiratory tract after SARS-CoV-2 infection.
SLU assistant professor of molecular microbiology and immunology James Brien said: “These data are very promising in my view. They show that AdCOVID conferred protection not only against Covid-19 related death, but also against any clinical signs of infection in the mice.”
Earlier, the University of Alabama showed that serum IgG and respiratory mucosal IgA titers in mice treated with AdCOVID were maintained for at least six months after a single intranasal vaccination. Memory B cells particular for spike antigen were found in the lymph nodes when analysed 5.5 months post-vaccination.
The new data indicate that a single vaccination with AdCOVID in preclinical models results in long-lived systemic and mucosal immune responses against the SARS-CoV-2 virus and this is important for sustained protection from the disease.
Altimmune chief technology officer Dr Bertrand Georges said: “The data from these preclinical studies only reinforce our high expectations for the ongoing Phase 1 study of AdCOVID launched this quarter.
“The complete protection observed in a stringent challenge model combined with inhibition of viral replication and persistent serum and mucosal antibody responses has not previously been demonstrated in preclinical studies for a Covid-19 vaccine candidate and supports our view of AdCOVID as a leading Covid-19 vaccine candidate.”