As part of a 2014 contract with the National Institute of Allergy and Infectious Diseases (NIAID) to advance the development of a heat-stable ricin vaccine, Soligenix just announced new funding of $2.5 million.

The funds will support bulk drug substance and finished drug product manufacturing of Soligenix’s ricin vaccine candidate RiVax for future studies. The new round brings the total amount awarded under the contract to $21.2 million of a potential $24.7 million.

Ricin, a plant toxin and byproduct of castor oil production, can be used as biological weapon and a tiny bit the size of a grain is lethal to humans. Soligenix’s candidate is a recombinant vaccine that fights ribotoxic A chain—one of the two ricin toxin subunits—and contains two mutations that inactivate the toxicity of the ricin molecule. A team led by Ellen Vitetta, Ph.D., from the University of Texas Southwestern, developed the nontoxic vaccine protein and is sharing the NIAID funds with Soligenix.

Developers decided to add an aluminum adjuvant to the original vaccine after a phase 1a trial, and the adjuvanted version induced greater ricin neutralizing antibody levels in humans in a phase 1b study.

Scientists are now testing the vaccine in combination with Soligenix’s proprietary thermostability technology, ThermoVax. The company believes the technology can help produce a vaccine capable of maintaining stability for up to a year under temperatures as high as 40°C (104°F), compared to the previous requirement of around 4°C (39°F), making it easier to store and transport, a feature particularly important in an emergency.

A study (PDF) on monkeys showed that the new heat-stable adjuvant vaccine provided 100% protection against acute exposure to aerosolized ricin, the most lethal route of exposure to ricin.

Emergent BioSolutions, another frequent government contractor, is among the collaborators helping Princeton, New Jersey-based Soligenix develop what could become the first approved ricin vaccine. The two are jointly working on a commercially viable, scalable production technology for producing RiVax’s protein antigen at Emergent’s Baltimore facility.

RiVax currently bears an orphan drug designation from the FDA on its vaccine. If the candidate turns into a successful vaccine, it could become part of the national stockpile as a biodefense measure.