Soligenix announces heightened stability for RiVax

Soligenix, Inc., has announced the publication of an article describing preclinical formulations of RiVax, a ricin toxin vaccine, with heightened stability.

The article, published in the February 2010 edition of Vaccine, was authored by Soligenix's collaborators at the University of Texas Southwestern Medical Center at Dallas, which originated the vaccine.

RiVax is currently under evaluation in Phase 1 human safety and immunogenicity trials as well as non-human primate trials for efficacy.

In this latest study, which was meant to establish preliminary conditions for long term stability to avoid the use of a cold chain, a series of formulations of RiVax, a modified recombinant ricin A chain protein, were examined for comparative effects of storage at room temperature versus refrigeration.

One combination, designed with excipients expected to add to protein stability and processed by lyophilization to remove water, was found to result in a vaccine retaining immunogenicity in animals for one year at room temperature.

"We know that the ricin subunit vaccine itself is very sensitive to denaturation, and we are very encouraged to find lyophilization conditions that aid in the long-term stability of the vaccine," Dr. Ellen Vitetta, director of the Cancer Immunobiology Center at UT Southwestern and an author of the study, said. "We are also pleased to see that in our study storage for over one year at ambient conditions resulted in no apparent degradation of potency or the integrity of the protein immunogen."

The lead formulation in the study showed no evidence of degradation while control formulations aggregated when reconstituted with water.

"These results are very promising not only for the future development of RiVax in particular, but also for the potential development of other vaccines with long-term stability, especially those using conventional adjuvants composed of aluminum salts," Robert N. Brey, Ph.D., chief scientific officer of Soligenix, said.