On Sept. 28, 2021, Soligenix announced publication of pre-clinical immunogenicity studies for CiVax (heat stable COVID-19 vaccine program) that demonstrated durable broad-spectrum neutralizing antibody responses, including against the Beta, Gamma and Delta variants of concern. The article, titled “Protein Vaccine Induces a Durable, More Broadly Neutralizing Antibody Response in Macaques than Natural Infection with SARS-CoV-2 P.1,” was posted as an accelerated preprint on bioRxiv.

CiVax™ is the Company’s heat stable subunit vaccine candidate for the prevention of COVID-19, the disease caused by infection with SARS-CoV-2. Ongoing collaborations with Dr. Lehrer have confirmed the feasibility of developing a broadly immunogenic vaccine for COVID-19. A full-length Spike protein antigen coupled with liquid or lyophilized (thermostabilized) CoVaccine HT™ adjuvant has been tested for immunogenicity and efficacy in the context of Gamma variant challenge in non-human primates (NHPs). NHPs were vaccinated twice, three weeks apart, and were subsequently challenged with Gamma variant both intranasally and intratracheally 12 weeks later. While most vaccines tested in NHPs use a challenge date only four weeks post-vaccination when antibody levels are peaking, the use of a later challenge time in this study demonstrates the durable response elicited by this vaccine candidate.

While the vaccine antigen is developed based on the Spike protein of the original SARS-CoV-2 strain, it elicited cross-neutralizing antibodies against Beta, Gamma and Delta variants of concerns. After challenge, vaccinated animals had a lower peak viral load and more rapid resolution of infectious virus, coupled with reduced lung damage. After challenge with Gamma variant, animals that were not vaccinated with CiVax™ generated a neutralizing antibody response to Beta and Gamma variants but not to the original strain and the Delta variant, demonstrating that natural infection may not yield sufficiently robust immunity. In stark contrast, CiVax™-vaccinated animals subsequently challenged with Gamma variant had enhanced neutralizing antibody responses against the original strain, as well as the Beta, Gamma and Delta variants.

While a number of vaccines are available worldwide, the requirement for cold chain shipping and timely administration, coupled with manufacturing scale-up logistics, have limited the world’s supply. Rapid vaccine administration worldwide is necessary to curtail disease spread and slow or pre-empt evolution of mutations, which may abrogate the effectiveness of current vaccine approaches. Previous work with the novel CoVaccine HT™ adjuvant has indicated that it can be thermostabilized both alone and in combination with antigens, potentially yielding a single-vial presentation of CiVax™, which would not require cold chain distribution or storage.

Coronavirus infections can cause a wide spectrum of disease in humans, ranging from a common cold to a more severe respiratory infection, such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS), which have a case mortality rate of approximately 10% and 30%, respectively. Similar to filoviruses, coronaviruses also are endemic in wildlife populations and can be transmitted to humans with close contact. The COVID-19 outbreak, caused by SARS-CoV-2, is the most recent example of a suspected species crossover seen with this virus family. COVID-19 has been declared a global pandemic by the World Health Organization.