Soligenix Initiates Clinical Trial Ricin Toxin Vaccine

Soligenix, Inc. has announced that it has opened the study titled "A Phase 1C, Double-Blind, Placebo-Controlled, Randomized Study to Evaluate the
Safety of RiVax, a Lyophilized Ricin Toxin A-Chain Subunit Vaccine with Alum-Adjuvant, in Healthy, Normal Adults."
Preliminary safety results from the trial are expected in the second quarter of 2020 with longer-term safety and immunogenicity results from throughout the 6-month follow-up period expected in the fourth quarter of 2020.

RiVax is the Company's vaccine candidate for the prevention of death following exposure to a lethal dose of ricin toxin using a unique antigen that is completely devoid of the toxic activity of ricin. The RiVax antigen has demonstrated safety in two previous Phase 1 clinical studies.  When formulated using Soligenix's proprietary heat stabilization technology (ThermoVax), RiVax has demonstrated significantly enhanced thermostability and up to 100% protection in non-human primates (NHPs) in preclinical aerosol challenge models. RiVax is being developed under the US Food and Drug Administration (FDA) "Animal Rule" and previous studies have identified potential immune correlates of protection between NHPs and humans that will be measured in this study.

The Phase 1C, double-blind, placebo-controlled, randomized study in healthy adult volunteers is designed to evaluate the safety and immunogenicity of a standard 3-dose vaccine regimen of RiVax utilizing ThermoVax, administered monthly, followed by a 6-month follow-up period.  In addition to evaluating the overall safety and tolerability of the vaccine, immunogenicity endpoints will be measured during and after vaccination throughout the follow-up period.  The study is expected to enroll 8 subjects (2 placebo, 6 RiVax).

"We are pleased to initiate this study and advance our world-leading vaccine candidate to protect against ricin toxin poisoning," stated Richard C. Straube, MD, Senior Vice President and Chief Medical Officer of Soligenix. "Ricin toxin is easily made in large quantities and is lethal in extremely small quantities. RiVax is an orphan designated product in both the US and Europe. We are pleased that RiVax may be able to provide significant protection against this deadly bioweapon." 

Previous studies with less refined formulations have demonstrated safety and immunogenicity of the vaccine antigen, but suffered from suboptimal stability. The thermostabilized RiVax formulation is stable for up to 12 months at temperatures as high as 40 degrees Celsius (104 degrees Fahrenheit). This thermostabilization is achieved with specific changes in formulation conditions, including the use of Generally Regarded as Safe (GRAS) stabilizing excipients and lyophilization (freeze-drying).  Both the Phase 1A study conducted with liquid formulated antigen alone and the Phase 1B study conducted with antigen and an alum-adjuvant have already demonstrated the safety and immunogenicity of these critical components of the RiVax formulation.

The development of RiVax has been funded through a series of grants from both the National Institute of Allergy and Infectious Diseases (NIAID) and the FDA and ongoing development is sponsored by NIAID contract #HHSN272201400039C. Non-dilutive funding for the development of RiVax has exceeded $40M to date.

Tags: CBRNe, Biological

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