Soligenix Announces Publication of Positive Pre-Clinical Results with RiVax(TM), Its Vaccine Against Ricin Toxin

Collaborative Effort Between Soligenix and Wadsworth Center Describes the Properties of Protective Antibodies to Ricin Toxin

PRINCETON, NJ, USA I December 28, 2009 I Soligenix, Inc. (OTC Bulletin Board: SNGX) (Soligenix or the Company), formerly known as DOR BioPharma, Inc., a late-stage biotechnology company, announced today the publication of an article in the January 2010 edition of Infection and Immunity, detailing the characteristics of several immunodominant regions of ricin A chain, the antigenic component of RiVax™. RiVax™ is Soligenix's vaccine to protect against exposure to ricin toxin and is currently being evaluated in Phase 1 human safety and immunogenicity trials, as well as nonhuman primate trials for efficacy.

The article, entitled "A Monoclonal Immunoglobulin G Antibody Directed against an Immunodominant Linear Epitope on the Ricin A Chain Confers Systemic and Mucosal Immunity to Ricin," is the result of collaborative efforts between the Wadsworth Center of the New York State Department of Health (Albany, NY) and Soligenix. The research was funded in large part by several National Institutes of Health (NIH) grants to the Company for the development of RiVax™. The full article (Neal et al., Infection and Immunity, 2010, volume 78: pp. 552-561) is available online at:

In this study, the investigators produced and characterized a monoclonal antibody directed against a region ("epitope") of the ricin A chain previously known to be highly immunologically stimulatory ("immunodominant") in humans. The monoclonal antibody was shown to bind the ricin A chain with high affinity, and to be capable of neutralizing ricin toxin in a cell-based killing assay. Moreover, when administered passively to mice, the neutralizing antibody was sufficient to protect the animals against both systemic (i.e., intraperitoneal) and mucosal (i.e., intragastric) ricin challenge. These results advance the concept that antibodies present in the circulation at the time of toxin exposure not only protect animals against death, but may also prevent the toxin's effects on mucosal tissues. This is an important finding, as ricin is toxic to humans following ingestion and inhalation. The study is also significant because it raises the possibility of using specific linear determinants on the ricin A chain as markers for protective immune responses in humans. Immunological readouts, such as the ability of serum antibodies to react with specific neutralizing epitopes on the ricin A chain, along with other markers that are currently in use to investigate human immune responses, will be essential in fully evaluating the efficacy of candidate ricin vaccines such as RiVax™, in the absence of the ability to perform vaccine efficacy trials in humans.

"These data are important in terms of ricin vaccine development, since they firmly establish that pre-existing serum antibodies directed against linear determinants on the ricin A chain are sufficient to confer both systemic and mucosal immunity to ricin," stated Nicholas Mantis, Ph.D., Research Scientist IV, Wadsworth Center, and lead author of the study.

"Vaccination by injection primarily induces antibodies in the circulation, and in the case of RiVax™, these fundamental results further indicate that intramuscular vaccination will be expected to protect humans against ingestion of toxin or aerosolized toxin exposure," said Robert N. Brey, Ph.D., Chief Scientific Officer of Soligenix, and a co-author of the study. "The publication of these results is exciting as they lead the way to the potential development of new applications utilizing a key target of neutralizing antibodies in vivo."

About RiVax™

RiVax™ is Soligenix's proprietary vaccine developed to protect against exposure to ricin toxin and is the most advanced vaccine in the company's portfolio. RiVax™ induces a protective immune response in animal models of ricin exposure and is currently being evaluated in humans. One human Phase 1 clinical trial has been completed and a second trial is currently being conducted.

Results of the first Phase 1 clinical trial of RiVax™ established that the immunogen was safe and induced antibodies anticipated to protect humans from ricin exposure. The outcome of the study was published in the Proceedings of the National Academy of Sciences (Vitetta et al., 2006, PNAS, 105:2268-2273). The second trial, sponsored by the University of Texas Southwestern Medical Center (UTSW), is currently evaluating a more potent formulation of RiVax™. Soligenix has developed processes for large-scale manufacturing and is further establishing correlates of the human immune response in nonhuman primates.

The development of RiVax™ has been sponsored through a series of overlapping challenge grants (UC1) and cooperative grants (U01) from NIH, granted to Soligenix and to UTSW where the vaccine originated. The second clinical trial is being supported by a grant to UTSW from the US Food and Drug Administration's Office of Orphan Products Development. 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

Ricin toxin is a plant toxin thought to be a bioterror threat because of its stability and high potency, as well as the large worldwide reservoir created as a by-product of castor oil production. Exposure to ricin results in local tissue necrosis and general organ failure leading to death within several days of exposure. The potential use of ricin toxin as a biological weapon has been highlighted in an FBI terrorism report, which states that "Ricin and the bacterial agent anthrax are emerging as the most prevalent agents involved in WMD investigations" (

There are currently no effective means to prevent the effects of ricin intoxication. The successful development of an effective vaccine against ricin toxin may act as a deterrent against the actual use of ricin as a biological weapon and could be used in rapid deployment scenarios in the event of a biological attack. RiVax™ would potentially be added to the Strategic National Stockpile and dispensed in the event of a terrorist attack.

About Soligenix, Inc.

Soligenix, Inc. (Soligenix), formerly known as DOR BioPharma, Inc., is a late-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 or BDP), is a potent, locally acting corticosteroid being developed for the treatment of acute gastrointestinal Graft-versus-Host-Disease (GI GVHD), a common and potentially life-threatening complication of hematopoietic cell transplantation. orBec® is currently the subject of a confirmatory Phase 3 clinical trial for the treatment of acute GI GVHD and an NIH-supported, Phase 2, randomized, double-blind, placebo-controlled trial in the prevention of acute GVHD. Both of these trials are actively enrolling patients. Soligenix has also recently initiated an NIH-supported Phase 1/2 clinical trial of SGX201 in the prevention of acute radiation enteritis. Additionally, Soligenix has a Lipid Polymer Micelle (LPM™) drug delivery technology for the oral delivery of leuprolide for the treatment of prostate cancer and endometriosis.

Through its Biodefense Division, Soligenix is developing biomedical countermeasures pursuant to the Project BioShield Act of 2004. Soligenix's lead biodefense product in development is a recombinant subunit vaccine called RiVax™, which is designed to protect against the lethal effects of exposure to ricin toxin. RiVax™ has been shown to be well tolerated and immunogenic in a Phase 1 clinical trial in normal volunteers. RiVax™ will also be the subject of a recent $9.4 million NIH grant received by the Company supporting development of new heat stable vaccines.

For further information regarding Soligenix, Inc., please visit the Company's website at

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, including SGX201, orBec® and LPM™, 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 its cash expenditures will not exceed projected levels, 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, that the US Congress may not pass any legislation that would provide additional funding for the Project BioShield program, that it will be able to patent, register or protect its technology from challenge and products from competition or maintain or expand its license agreements with its current licensors, or that its business strategy will be successful. Important factors which may affect the future use of orBec® for gastrointestinal GVHD include the risks that: the FDA's requirement that Soligenix conduct additional clinical trials to demonstrate the safety and efficacy of orBec® will take a significant amount of time and money to complete and positive results leading to regulatory approval cannot be assumed; Soligenix is dependent on the expertise, effort, priorities and contractual obligations of third parties in the clinical trials, manufacturing, marketing, sales and distribution of its products; orBec® may not gain market acceptance if it is eventually approved by the FDA; and others may develop technologies or products superior to orBec®. Factors affecting the development and use of SGX201 and LPM™ are similar to those affecting orBec®. These and other 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.

SOURCE: Soligenix

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