RiVax intradermal administration protects from mucosal, systemic ricin intoxication

Soligenix, Inc. (OTC Bulletin Board: SNGX) (Soligenix or the Company), a late-stage biopharmaceutical company, announced today the publication of an article in the June 2010 edition of Vaccine, which describes protection from mucosal and systemic ricin intoxication by intradermal administration of RiVax™, the Company's vaccine against ricin toxin. The article was authored by the Company's collaborators at the University of Texas Southwestern Medical Center at Dallas (UT Southwestern) where the vaccine originated. RiVax™ is currently being evaluated in Phase 1 human safety and immunogenicity trials, as well as non-human primate trials for efficacy.

The purpose of this study was to determine whether RiVax™ administered by intradermal (ID) injection would be more immunogenic and protective at lower doses. ID vaccination has several practical advantages in protecting humans due to the ease of administration, especially when using an ID gun, thereby eliminating the need for needles and subsequent needle disposal. In this publication, a comparison of ID and intramuscular (IM) vaccination with or without an aluminum salt adjuvant at several dose levels was investigated. The levels of anti-RiVax™ antibodies generated in serum as well as the ability of the vaccine to protect mice against ricin intoxication following systemic, gastric gavage or aerosol challenges were determined.

The major findings to emerge from this study are as follows:

1. ID vs. IM administration of RiVax™ without adjuvant conferred equal protection;
2. RiVax™ adsorbed to aluminum adjuvant was significantly better than RiVax™ alone in eliciting specific antibodies, resulting in both systemic and mucosal protection when 90-99% less vaccine was used;
3. Vaccination with RiVax™ adsorbed to aluminum adjuvant via the ID route was significantly better than vaccination via the IM route at protecting animals from ricin challenge, hence, smaller doses of vaccine may be required when ID vaccination is used;
4. In comparing IM vs. ID vaccination with RiVax™  adsorbed to aluminum adjuvant at low doses, the latter was more effective at protecting mice from ricin-induced lung damage; and
5. RiVax™ specific antibody levels correlated with post challenge survival.

"There have been many attempts to develop a prophylactic ricin vaccine, using different preparations of the ricin holotoxin with and without various adjuvants," stated Dr. Ellen Vitetta, Director of the Cancer Immunobiology Center at UT Southwestern and senior author of the study.  "But none of these have been as extensively studied as RiVax™ and none have looked at the ID vaccination route."

"Since it is likely that a ricin vaccine would be used in an emergency setting or by the military, the ease of ID vaccination with jet injectors or similar devices with lower doses of vaccine is rather important," stated Robert N. Brey, PhD, Chief Scientific Officer of Soligenix.  "It should also be noted that ID vaccination was highly effective at protecting the lungs of the mice from ricin aerosols, a likely route of delivery in the setting of bioterrorism."

The article, entitled "Intradermal administration of RiVax™ protects mice from mucosal and systemic ricin intoxication," was authored by Drs. Marconescu, Smallshaw, Pop, Ruback, and Vitetta at UT Southwestern. The research was funded directly by an NIH grant to UT Southwestern and complements the NIH funding to Soligenix for the development of RiVax™. The full article (Marconescu et. al., "Intradermal administration of RiVax protects mice from mucosal and systemic ricin intoxication," Vaccine) is available online at http://dx.doi.org/10.1016/j.vaccine.2010.05.045