Immunovaccine, Pfenex report positive results from anthrax vaccine studies

Immunovaccine, Inc., and Pfenex, Inc., announced positive results on Tuesday from anthrax challenge studies in rabbits in which most subjects were protected against a lethal anthrax challenge at a range of antigen doses.

The studies used Pfenex's mutant recombinant protective antigen formulated with Immunovaccine's DepoVax delivery system. Researchers tested mrPA-DepoVax as a single dose in rabbits and found all animals vaccinated with at least one third of a microgram of antigen were protected from anthrax infection. Four out of five animals vaccinated with mrPA-DepoVax containing one tenth of a microgram of antigen were also protected.

"The positive data from this latest study highlight the potential for the DepoVax platform to enable rapid response vaccines to combat bioterrorism," Marc Mansour, the chief operating officer of Immunovaccine, said. "The ability to decrease the antigen content and still produce lasting protective antibody titers that protect from anthrax challenge following one vaccination potentially demonstrates the immune enhancing characteristics of DepoVax."

Researchers observed a dose response in the first 28 days following vaccination with higher amounts of mrPA formulated in DepoVax eliciting higher levels of neutralizing antibodies. Antibody titers typically plateaued within 28 days and persisted until at least day 70 when animals were exposed to the disease agent. The findings suggest that animals may be protected within one month of a single immunization.

"Pfenex is excited to be collaborating with Immunovaccine in pursuit of a stable, fast acting, dose sparing and antigen sparing vaccine candidate that will meet the needs of the U.S. federal government," Bert Liang, the chief executive officer of Pfenex, said.

Further studies will be designed to evaluate the potential of DepoVax-based vaccines to offer rapid protection with one dose.