Vaccine Info

RiVax Ricin Toxin Vaccine

Authored by
Staff
Last reviewed
October 14, 2021
Fact checked by
Robert Carlson, MD
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RiVax Ricin Toxin Vaccine Description

RiVax Ricin Toxin Vaccine is Soligenix's proprietary heat stable recombinant subunit vaccine developed to protect against exposure to ricin toxin. RiVax® contains a genetically altered version of a Ricin Toxin A (RTA) chain containing two mutations that inactivate the ricin molecule's toxicity, originally invented at the University of Texas Southwestern. 

RiVax® uses Soligenix's proprietary ThermoVax® technology that creates a thermostabilized vaccine candidate that can be stored at room temperature for extended periods, making it compatible with United States government stockpiling requirements.

The thermostabilized version of RiVax® is produced by lyophilizing (freeze-drying) the vaccine in individual vials to form a solid white cake. This removes water and other components from the material, which would otherwise destabilize the protein. By using a proprietary process, the protein-aluminum combination remains intact.

The solid, lyophilized material can then be returned to a liquid form immediately before use by simply adding sterile water and mixing before injection. Because sterile water is also very common and very stable, this results in an extremely convenient product that can be stored for extended periods. Long-term storage and ease of use are key attributes for a product that may be stockpiled.

The RiVax® vaccine candidate uses one of the safest vaccination approaches known – using a modified inactivated protein component of the ricin toxin itself to raise antibody responses, combined with an alum adjuvant to boost the body’s response to the vaccine.

RiVax induces the adaptive immune system to produce antibodies that recognize and bind ricin toxin, preventing it from getting inside cells and killing them. After intramuscular injection with RiVax, IgG and other antibodies are produced and circulate within the body and are able to mop up ricin whether it was inhaled, eaten, or injected.

RiVax primarily consists of two components:

1. A modified form of the A-chain of the ricin toxin. The modifications have removed the biological activity of the protein while still retaining its shape to trigger an effective antibody response.

2. Aluminum (“alum”) as an adjuvant. Alum is a very well-known adjuvant, used in many commercial vaccines, with well-known safety profiles.

Soligenix, Inc. is a late-stage biopharmaceutical company (Nasdaq: SNGX) focused on developing and commercializing products to treat rare diseases where there is an unmet medical need.

Note: September 28, 2021 - Soligenix, Inc. announced the publication of pre-clinical immunogenicity studies for CiVax™ (heat-stable COVID-19 vaccine program), demonstrating 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."

RiVax Ricin Toxin Vaccine Indication

RiVax Ricin Toxin Vaccine candidate is indicated to prevent death following exposure to a lethal dose of ricin toxin.

RiVax Ricin Toxin Vaccine Dosage

RiVax is administered as an intramuscular injection on 2 or 3 occasions, resulting in the adaptive immune system mounting an antibody response.

RiVax induces the adaptive immune system to produce antibodies that recognize and bind ricin toxin, preventing it from getting inside cells and killing them. After intramuscular injection with RiVax®, IgG and other antibodies are produced and circulate within the body and can mop up ricin whether it was inhaled, eaten, or injected.

RiVax Ricin Toxin Vaccine News

December 8, 2020 - RiVax Ricin Toxin Vaccine is pursuing approval under the US Food and Drug Administration (FDA) "Animal Rule," applied to products where testing in clinical efficacy trials would be unethical. In the case of a ricin toxin vaccine, the vaccine's testing would be unethical since it would require exposing humans to ricin toxin. According to the CDC, Ricin is a poison found naturally in castor beans. Ricin can be found in many forms, including powder, mist, pellet, and can also be dissolved in water.  It is considered a weapon of terror based upon its stability and high potency and the fact that it is readily extracted from by-products of castor oil production.

RiVax Ricin Toxin Vaccine Clinical Trials

NCBI Phase 1: A pilot clinical trial of a recombinant ricin vaccine in normal humans.

NCBI Phase 1B:  Pilot Phase IB Clinical Trial of an Alhydrogel-Adsorbed Recombinant Ricin Vaccine

Clinical Trial NCT00812071: Phase 1B Study of RiVax, a Vaccine to Prevent the Toxic Effects of Ricin (FDA-OPD) Study Completion Date - January 2012

These studies suggest that RiVax/alum is safe and induces higher titers of total and neutralizing antibodies.