PRINCETON, N.J., May 11, 2020 /PRNewswire/ -- Soligenix, Inc. (Nasdaq: SNGX) (Soligenix or the Company), a late-stage biopharmaceutical company focused on developing and commercializing products to treat rare diseases where there is an unmet medical need, announced today publication of immunogenicity studies for RiVax® (heat stable ricin toxin vaccine) identifying novel correlates of immune protection to facilitate potential approval under the United States Food and Drug Administration (FDA) "Animal Rule." The article, titled "A Multivariate Model Combining Endpoint and Epitope-specific Antibody Responses as a Correlate of Protection to Ricin Toxin," has been submitted to the peer-reviewed medical journal Vaccine and a preprint is available here.
RiVax® is the Company's vaccine candidate for the prevention of death following exposure to a lethal dose of ricin toxin using a unique antigen that is completely devoid of the toxic activity of ricin. Further formulated by Soligenix to have enhanced thermostability, RiVax® has demonstrated up to 100% protection in mice and non-human primates (NHPs) subsequently exposed to lethal doses of ricin toxin either systemically or by aerosol. In studies conducted in collaboration with the laboratory of Dr. Nicholas Mantis, Research Scientist, Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, species independent tests to evaluate the protective immunogenicity of the vaccine were developed. These tests will facilitate potential approval of RiVax® under the FDA Animal Rule which requires the evaluation of efficacy in animals (RiVax® has demonstrated up to 100% protection in NHPs exposed to lethal aerosolized ricin), safety in humans (the RiVax® antigen has been demonstrated to be well-tolerated in human Phase 1 clinical studies) and immunogenicity correlated between animal models and humans.
"These results continue to reinforce the link between the antibody response to the vaccination and the potency of the RiVax® vaccine," stated Dr. Oreola Donini, Chief Scientific Officer of Soligenix. "This, and other ongoing work in our collaboration with Dr. Mantis and his team, has continued to corroborate the efficacy of RiVax® and will facilitate its potential approval."
Approval for RiVax® will be pursued under the FDA "Animal Rule," which is applied to products where testing in clinical efficacy trials would be unethical. In the case of a ricin toxin vaccine, clinical efficacy testing of the vaccine is unethical since it would require intentionally exposing humans to ricin toxin. The Animal Rule is generally associated with the approval of medical countermeasures for biodefense purposes.
In addition to being protective and thermostable, RiVax® has demonstrated that a reduced number of vaccinations may establish protection, potentially utilizing only two doses instead of three.
RiVax® studies are supported by a contract (# HHSN272201400039C) award of up to $21.2 million from the National Institute of Allergy and Infectious Diseases (NIAID). Non-dilutive funding for the development of RiVax® has exceeded $40 million to date.
RiVax® has received Orphan Drug designations from both the FDA and European Medicines Agency (EMA) and, upon approval, has the potential to qualify for a biodefense Priority Review Voucher (PRV).
About Ricin Toxin
Ricin toxin is a lethal plant-derived toxin and potential biological weapon because of its stability and high potency, and the fact that it is readily extracted from by-products of castor oil production. Ricin comes in many forms including powder, mist or pellet. Ricin can also be dissolved in water and other liquids. The US Centers for Disease Control and Prevention estimates that the lethal dose in humans is about the size of a grain of salt. Ricin toxin illness causes tissue necrosis and general organ failure leading to death within several days of exposure. Ricin is especially toxic when inhaled. Ricin works by entering cells of the body and preventing the cells from making the proteins they need. Without the proteins, cells die, which is eventually harmful to the entire body.
There are currently no effective treatments for ricin poisoning. The successful development of an effective vaccine against ricin toxin may act as a deterrent against the actual use of ricin as a biological weapon and could be used to vaccinate military personnel and civilian emergency responders at high risk of potential exposure in the event of a biological attack.
About RiVax®
RiVax® is Soligenix's proprietary heat stable recombinant subunit vaccine developed to protect against exposure to ricin toxin, the threat of which has been highlighted in the news with an envelope addressed to President Trump that was thought to contain this potent and potentially lethal toxin. With RiVax®, Soligenix is a world leader in the area of ricin toxin vaccine research.
RiVax® contains a genetically altered version of a Ricin Toxin A (RTA) chain containing two mutations that inactivate the toxicity of the ricin molecule which was originally invented at the University of Texas Southwestern. Phase 1 clinical studies to date have demonstrated the safety of the antigen and adjuvant, as well as the generation of ricin neutralizing antibodies which are increased in the presence of the alum adjuvant. In animal studies, the alum formulation of RiVax® also induced higher titers and longer-lasting antibodies than the adjuvant-free vaccine. Vaccination with the thermostabilized alum-adjuvanted RiVax® formulation in a large animal model provided 100% protection (p