Soligenix Announces Positive Phase 1B Clinical Results with RiVaxTM, its Vaccine Against Ricin Toxin Exposure

Princeton, NJ August 30, 2012 – Soligenix, Inc. (OTCQB: SNGX) (Soligenix or the Company), a development stage biopharmaceutical company, announced today the results of a Phase 1B clinical trial of an aluminum hydroxide (Alum) adjuvanted formulation of RiVax™, designed to improve the immunogenicity of the vaccine. The results of the Phase 1B study indicate that Alum adjuvanted RiVax™ is safe and well tolerated, and induces greater ricin neutralizing antibody levels in humans than adjuvant-free RiVax™. The results of this study have been published in the online edition of Clinical and Vaccine Immunology http://cvi.asm.org/content/early/2012/08/16/CVI.00381-12.full.pdf.

The Phase 1B trial was conducted by investigators at the University of Texas Southwestern Medical Center (UTSW) led by Dr. Ellen Vitetta, Director of the Cancer Immunobiology Center at UTSW and supported by a combination of grants including a $940,000 grant from the Office of Orphan Products Development (OOPD) of the Food and Drug Administration (FDA). The trial in healthy volunteers was designed to evaluate the long term safety and immunogenicity of escalating doses of the vaccine up to one year after a primary vaccination, in which the vaccine was administered by intramuscular injections at 0, 6 weeks, and 6 months in doses of 10 and 100 micrograms. The vaccine was well tolerated in all individuals with only mild side effects that are typical of reactions to vaccines injected intramuscularly. At peak antibody titers determined two weeks after the third vaccination, all of the subjects developed neutralizing antibodies against ricin toxin. When comparing peak antibody titers obtained in the Phase 1B trial to that of the prior Phase 1A trial which used an adjuvant-free formulation of RiVax™, all subjects in the 10 microgram dose group of the Phase 1B trial developed neutralizing antibodies with the Alum formulation of RiVax™ compared to only one of five subjects in the 10 microgram group of the adjuvant-free vaccine.  For the 100 microgram dose vaccine, peak neutralizing titers were four-fold higher with the Alum formulation of RiVax™ as compared to the adjuvant-free vaccine, with total antibody titers (including all antibodies directed against the vaccine) 17 fold higher. Of all vaccine recipients of both the high dose (100 micrograms) and the low dose (10 micrograms) in the Phase 1B trial, 100% were seropositive at nine months after the first vaccination, with 60% remaining positive at one year.

“These positive results indicate a route forward for the further development of the vaccine in larger and more definitive trials in humans and to provide the additional correlates of protective immunity in pivotal animal studies.” said Robert N. Brey, PhD, Chief Scientific Officer of Soligenix. “With the formal Request for Information (RFI) from the Department of Defense regarding the status of ricin toxin vaccine development, we believe that Soligenix is well positioned to collaborate with the DoD on the future development of RiVax™.”

Dr. Brey continued, “The Phase 1B results demonstrate that well characterized adjuvants can improve the performance of highly purified subunit antigens such as the one contained in RiVax™. The next steps for the development of RiVax™ will include the evaluation of secondary adjuvants to enhance the induction of neutralizing antibodies in fewer doses and the employment of our ThermoVax™ technology to stabilize the ingredients of the vaccine for long term storage at ambient temperature conditions.”

About RiVax™

RiVax™ is Soligenix’s proprietary recombinant subunit vaccine developed to protect against exposure to ricin toxin. With RiVax™, Soligenix is a world leader in the area of ricin toxin vaccine research.

RiVax™ contains a genetically altered version of ricin A chain containing two mutations that inactivate the inherent toxicity of the ricin molecule. The 1A clinical trial was conducted with a formulation of RiVax™ that did not contain an adjuvant.  That trial revealed dose dependent seroconversion as well as lack of toxicity of the molecule when administered intramuscularly to human volunteers.  The adjuvant-free formulation of  RiVax™ induced toxin neutralizing antibodies that lasted up to 127 days by the third vaccination in several individuals.  To increase the longevity and magnitude of toxin neutralizing antibodies, RiVax™ was formulated with Alum as an adjuvant for the Phase 1B clinical trial.  Alum is an adjuvant that is used in many human vaccines, including most vaccines used in infants. In preclinical animal studies, the Alum formulation of RiVax™ induced higher titers and longer lasting antibodies than the adjuvant-free vaccine.

Results of the prior Phase 1A trial of RiVax™ were published in the Proceedings of the National Academy of Sciences (Vitetta et al., 2006, PNAS, 105:2268-2273). The development of RiVax™ has been sponsored through a series of overlapping challenge grants (UC1) and cooperative grants (U01) from the NIH which were granted to Soligenix and to UTSW where the vaccine originated. Soligenix and UTSW have collectively received approximately $25 million in grant funding from the NIH for development of RiVax™ and related vaccine technologies.

About Ricin Toxin 

The Centers for Disease Control has classified ricin toxin as a Category B biological agent. Currently, there are no FDA approved therapeutics or vaccines that can be used to protect against ricin exposure or to reverse its effects once exposed. Ricin toxin is a protein that consists of an A and B subunit that can be extracted from the beans of the castor plant, Ricinus communis. The potential use of ricin toxin as a biological weapon of mass destruction has been highlighted in an FBI Bioterror report released in November 2007, entitled Terrorism 2002-2005, which states that “Ricin and the bacterial agent anthrax are emerging as the most prevalent agents involved in Weapons of Mass Destruction (WMD) investigations”.

The toxic effects of ricin are caused by its ability to inhibit protein synthesis. Ricin’s potency is due to its promiscuity, intoxicating all known cell types, and extremely efficient enzymatic activity. Ricin can be introduced into the body through inhalation of an aerosol, or through ingestion, injection or infusion. While ricin is second in toxicity only to botulinum toxin, it is far easier to obtain, prepare, and use.  Because of the high content of ricin in castor beans, ricin toxin can be extracted from the mash produced as a by-product of castor oil production (castor oil is found in many commonly used substances such as paints, varnishes, and lubricating oils, and is also used as a purgative) by several simple enrichment steps and, therefore is easy to stockpile. Recent economic surveys have shown that there are over 1 million tons of castor beans produced in the world annually. The global commercial production has the potential to yield approximately 50,000 tons of pure ricin. The fate of much of this ricin in countries outside of the US is unknown.

Once exposed to lethal doses of ricin, death is irreversible after four hours and takes three to five days to kill an individual. The current expectation that drives vaccine development of RiVax™ is that ricin is most likely to be distributed as an aerosol form, since it is highly lethal by this route. There are currently no effective means to prevent the effects of ricin intoxication. In recent years, Al Qaeda branches in Yemen and the Arabian Peninsula have threatened the use of ricin toxin to poison food and water supplies and in connection with explosive devices.

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 gastrointestinal Graft-versus-Host disease (GI GVHD), a common and potentially life-threatening complication of hematopoietic cell transplantation. Soligenix is also developing proprietary formulations of oral BDP for the prevention/treatment of gastrointestinal disorders characterized by severe inflammation, including pediatric Crohn’s disease (SGX203) and acute radiation enteritis (SGX201), which is the subject of a recently completed National Cancer Institute (NCI)-supported Phase 1/2 clinical trial.

Through its BioDefense Division, Soligenix is developing countermeasures pursuant to the Biomedical Advanced Research and Development Authority (BARDA) Strategic Plan of 2011-2016 for inclusion in the US government’s Strategic National Stockpile. 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 VeloThrax™, a vaccine against anthrax exposure. RiVax™ has been shown to be well tolerated and immunogenic in two Phase 1 clinical trials in healthy volunteers. Both RiVax™ and VeloThrax™ are currently the subject of a $9.4 million National Institute of Allergy and Infectious Diseases (NIAID) grant supporting development of Soligenix’s new vaccine heat stabilization technology known as ThermoVax™. Soligenix is also developing OrbeShield™ for the treatment of gastrointestinal acute radiation syndrome (GI ARS) under a $600,000 NIAID Small Business Innovation Research (SBIR) grant. OrbeShield™ has previously demonstrated statistically significant preclinical survival results in two separate canine GI ARS studies funded by the NIH.

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.