Therapy Areas: AIDS & HIV
Soligenix Publishes Positive Long-Term Data Supporting Thermostability and Conformational Integrity of the RiVax Ricin Toxin Vaccine
5 September 2018 - - US-based biopharmaceutical company Soligenix, Inc. (NASDAQ : SNGX) has published extended stability studies for RiVax showing up to 100% protection in mice even after 12 months storage at 40 degrees Celsius (104 degrees Fahrenheit), as well as the identification of a potential in vitro stability indicating assay, critical to adequately confirming long-term shelf-life of the vaccine, the company said.

The article, entitled "Thermal Stability and Epitope Integrity of a Lyophilized Ricin Toxin Subunit Vaccine," is published in the journal Vaccine online and is available here.

RiVax is a ricin toxin vaccine, under development by Soligenix, and originally invented at the University of Texas Southwestern.

Further formulated by Soligenix to have enhanced thermostability, RiVax has demonstrated up to 100% protection in mice and non-human primates 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, the thermostabilized formulation of RiVax maintained potency (up to 100% protection of mice) even after storage under stressed conditions (40 degrees Celsius or 104 degrees Fahrenheit) for at least 12 months.

RiVax potency correlated with the maintenance of protein conformational integrity, as confirmed by evaluating binding potential to monoclonal antibodies; however, when RiVax protein conformation was altered, RiVax potency was shown to be reduced, as shown in this recent publication.

Additional studies, using these same antibodies to evaluate the protective efficiency of antibody generation as important biomarkers of vaccine efficacy, have also been completed, as presented previously here.

Approval for RiVax will be pursued under the United States (US) Food and Drug Administration "Animal Rule."

The FDA Animal Rule is applied to products where testing in clinical trials would be unethical. In the case of a ricin toxin vaccine, clinical efficacy testing of the vaccine is unethical since exposing unvaccinated humans (i.e., placebo-control group) to ricin toxin would be fatal.

The Animal Rule combines safety studies in humans and efficacy testing in animals, typically NHPs, to facilitate approval and is generally associated with the approval of medical countermeasures for biodefense purposes.

Key to the application of the Animal Rule is the requirement to establish a correlation between the responses observed in clinical trials in healthy volunteers with the response demonstrated in animal efficacy studies.

In addition to being protective and thermostable, RiVax has demonstrated that a reduced number of vaccinations may be required to establish protection, potentially utilizing only two doses instead of three.

Further efficacy studies in NHPs evaluating potential dosing regimens are anticipated within a year, in addition to continued human safety testing evaluating the thermostable RiVax formulation.
RiVax studies are supported by a contract (# HHSN272201400039C) award of up to USD24.7m from the National Institute of Allergy and Infectious Diseases (NIAID).

RiVax has received Orphan Drug designations from both the FDA and European Medicines Agency and, upon approval, has the potential to qualify for a biodefense Priority Review Voucher.
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