Soligenix Announces Further Progress with ThermoVax™ for Long-Term Vaccine ThermoStability

Princeton, NJ – April 25, 2012 – Soligenix, Inc. (OTCBB: SNGX) (Soligenix or the Company), a development stage biopharmaceutical company, announced today further progress in the development of ThermoVax™, its proprietary vaccine thermostabilization technology.  Progress has been based on additional characterization of the stability of prototype vaccines that have been kept at elevated temperatures in excess of three months. These studies are being conducted as part of a continuing program to evaluate the effectiveness of vaccines designed to withstand extremes of temperature and other environmental stress conditions.  The research and development of ThermoVax™ is being supported by a $9.4 million National Institute of Allergy and Infectious Disease (NIAID) grant to Soligenix for biodefense indications against ricin toxin and anthrax exposure.

Prior results have indicated that the Company’s aluminum-adjuvanted ricin toxin vaccine, known as RiVax™, retained effectiveness and potency while stored at 40 degrees Celsius  for one month when combined with the ThermoVax™ technology.  Confirmatory results have now extended these initial observations to more than three months when the vaccine is kept at 40 degrees Celsius. In contrast, liquid RiVax™ vaccine when stored at 40 degrees Celsius rapidly degraded and no longer maintained its effectiveness. This is due to the fact that the ricin A chain is normally extremely labile and sensitive to temperature, and rapidly loses its ability to induce neutralizing antibodies when exposed to temperatures higher than 8 degrees Celsius.  ThermoVax™ is able to produce stable and potent vaccine formulations by combining precise lyophilzation technology with conventional aluminum adjuvants, secondary adjuvants (for rapid onset of immunity), and protein subunits.

The removal of water from pharmaceutical preparations by lyophilization is often used to confer extended shelf life to therapeutic protein products, but vaccines often lose potency during lyophilization, especially if they are formulated with aluminum salt adjuvants that are commonly used in vaccines. As a result, most vaccine products must be kept under tightly controlled conditions since accidental freezing or temperature excursions exceeding customary refrigeration ranges will destroy and inactivate these vaccines.

“We continue to be pleased with the data generated thus far with ThermoVax™.  The ability of vaccines to withstand extreme temperatures is a significant step forward in vaccine technology,” stated Robert N. Brey, PhD, Chief Scientific Officer of Soligenix. “ThermoVax™ may also enable preparation of otherwise difficult multivalent (protective against multiple pathogens) formulations. We plan to apply ThermoVax™ to other conventional vaccines that require refrigeration.”

The underlying technology has been developed by Drs. John Carpenter and Theodore Randolph at the University of Colorado whose team performed the studies along with Dr. Nicholas Mantis of The New York State Department of Health in Albany.

For vaccines that are intended for long-term stockpiling, such as for use in biodefense or in pandemic situations, the utilization of ThermoVax™ has the potential to facilitate storage and distribution of strategic national stockpile vaccines in emergency settings. NIAID has highlighted the priority of technologies for biodefense vaccines that focus on broad spectrum approaches including vaccine adjuvants and temperature stabilization for long shelf life, rapid onset of immunity, and surge capacity for production.  Further, the World Health Organization reports that 50% of all global vaccine doses are wasted because vaccines are not kept within required temperature ranges.  Elimination of the cold chain would also enhance the utility of these vaccines for emerging markets and for other applications requiring but lacking reliable cold chain capabilities.  Cold chain requirements add considerable cost to the production and storage of current conventional vaccines.

About Soligenix, Inc.

Soligenix is a development stage biopharmaceutical company developing products to treat life-threatening side effects of cancer treatments and serious gastrointestinal diseases, and vaccines for certain bioterrorism agents. Soligenix’s lead product, orBec® (oral beclomethasone dipropionate), is a potent, locally acting corticosteroid that has been initially developed for the treatment of acute gastrointestinal Graft-versus-Host disease (GI GVHD), a common and potentially life-threatening complication of hematopoietic cell transplantation. Soligenix is also developing oral BDP for the prevention/treatment of other gastrointestinal disorders characterized by severe inflammation, including acute radiation enteritis (SGX201), which is the subject of a recently completed National Cancer Institute (NCI)-supported Phase 1/2 clinical trial and pediatric Crohn’s disease (SGX203).

Through its Vaccines/Biodefense Division, Soligenix is developing countermeasures pursuant to the Project BioShield Act of 2004. Soligenix’s lead biodefense products in development are a recombinant subunit vaccine called RiVax™, which is designed to protect against the lethal effects of exposure to ricin toxin and SGX204, a vaccine against anthrax exposure.  RiVax™ has been shown to be well tolerated and immunogenic in a Phase 1 clinical trial in normal volunteers. Both RiVax™ and SGX204 are currently the subject of a $9.4 million National Institute of Allergy and Infectious Disease (NIAID) grant supporting development of new vaccine technology known as ThermoVax™. Soligenix is also developing SGX202 for the treatment of gastrointestinal acute radiation syndrome (GI ARS) and has demonstrated statistically significant preclinical survival results in a canine GI ARS model.

For further information regarding Soligenix, Inc., please visit the Company’s Website at www.soligenix.com.

This press release contains forward-looking statements that reflect Soligenix, Inc.’s current expectations about its future results, performance, prospects and opportunities. Statements that are not historical facts, such as “anticipates,” “believes,” “intends,” or similar expressions, are forward-looking statements. These statements are subject to a number of risks, uncertainties and other factors that could cause actual events or results in future periods to differ materially from what is expressed in, or implied by, these statements. Soligenix cannot assure you that it will be able to successfully develop or commercialize products based on its technology, particularly in light of the significant uncertainty inherent in developing vaccines against bioterror threats, manufacturing and conducting preclinical and clinical trials of vaccines, and obtaining regulatory approvals, that product development and commercialization efforts will not be reduced or discontinued due to difficulties or delays in clinical trials or due to lack of progress or positive results from research and development efforts, that it will be able to successfully obtain any further grants and awards, maintain its existing grants which are subject to performance, enter into any biodefense procurement contracts with the US Government or other countries, or that the US Congress may not pass any legislation that would provide additional funding for the Project BioShield program. These and other risk factors are described from time to time in filings with the Securities and Exchange Commission, including, but not limited to, Soligenix’s reports on Forms 10-Q and 10-K. Unless required by law, Soligenix assumes no obligation to update or revise any forward-looking statements as a result of new information or future events.