The adjuvanted RiVax was found to be safe and well tolerated in the study, conducted in healthy volunteers, and induced better ricin neutralising antibody levels in humans compared to adjuvant-free RiVax.
Soligenix chief scientific officer Robert Brey said the 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.
"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," Brey added.
"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."
The vaccine was found to be well tolerated with mild side effects that are characteristics of reactions to intramuscularly injected vaccines and all of the subjects developed neutralising antibodies against ricin toxin at peak antibody titers determined two weeks after the third vaccination.
All of the subjects who received either high dose (100 micrograms) or the low dose (10 micrograms) vaccine in the Phase 1B trial were 100% seropositive at nine months after the first vaccination, with 60% remaining positive at one year.