PharmAthene has announced the results of a Phase I clinical study of Valortim, a fully human monoclonal antibody, used as both post-exposure prophylaxis and therapeutic treatment for anthrax infection.

The Phase I clinical study involved 46 healthy volunteers, who received either a single intravenous (IV) dose of Valortim ranging from 0.3 to 20.0 mg/kg or a single 100 mg intramuscular (IM) dose of Valortim.

The Phase I study is designed to evaluate the safety and tolerability of Valortim, and showed that Valortim was safe, well-tolerated and non-immunogenic when administered as single 0.3mg/kg to 20mg/kg IV infusions or as a single IM dose injection at 100mg.

In the cohorts dosed with 1.0mg/kg IV or 100mg IM, subjects were tested for the level of toxin neutralising activity present in their serum 71 days after dosing, which provide a standard for defining a protective vaccine response.

Earlier preclinical studies showed that Valortim has the ability to provide protection against anthrax infection when administered prophylactically and also may increase survival when administered therapeutically.

In these studies, Valortim was found to protect both rabbits and monkeys against the lethal effects of anthrax infection at doses as low as 1mg/kg, and also improved survival as late as 48 hours post-exposure compared with controls.

PharmAthene executive vice-president and chief scientific officer Thomas Fuerst said the Phase I results reported that a single dose of Valortim can provide levels of antibodies in humans that correspond to protective levels in animal models and is well tolerated.

"The accumulating data suggest that Valortim is differentiated from other anthrax anti-toxins and possesses important characteristics that may make it a strong choice for procurement in the Strategic National Stockpile, including demonstrated efficacy in animal models as both a prophylactic and therapeutic for inhalational anthrax, efficacy at low doses, and a mechanism of action with unique properties.

”In addition to these recently published Phase I data, we have completed the in-life portion of a second Phase I clinical study of Valortim and expect to report final study results later this year,” Fuerst added.

The company also plans to work with the US Government to develop new biodefense countermeasures like Valortim to protect citizens both at home and on the battlefield.