MEDAREX, PHARMATHENE REPORT RESULTS OF ANTHRAX THERAPEUTIC STUDY
Medarex and PharmAthene have announced Phase I study results for Valortim (MDX-1303) in healthy volunteers. Valortim is a fully human antibody against anthrax infection developed using Medarex's UltiMAb Human Antibody Development System.
A Phase I clinical study was conducted to assess the safety and tolerability of Valortim. Forty-six healthy volunteers received either a single intravenous (IV) dose of Valortim ranging from 0.3 to 20 mg/kg (10 subjects in cohorts receiving 1, 3 or 10 mg/kg and three subjects in cohorts receiving 0.3 and 20 mg/kg) or a single 100-mg intramuscular (IM) dose of Valortim (10 subjects).
The data showed that Valortim was safe and well-tolerated. No drug-related Grade 2 to 4 or serious adverse events were reported. Grade 1 adverse events were reported in 16 of the volunteers overall, with the most common being pain/burning at the injection site for those being dosed intramuscularly (six subjects). Initial analyses of serum pharmacokinetics revealed increasing peak concentrations and overall duration of exposure to antibody with increasing dose, and a half-life of approximately 26 days for IV administration, and approximately 32 days for IM dosing.
In the cohorts dosed with 1.0 mg/kg IV or 100 mg IM, individual subjects were tested for the level of toxin-neutralizing activity present in their serum 71 days after dosing. The level of activity was comparable to the level of toxin neutralizing activity seen in pooled human sera provided by the Centers for Disease Control and Prevention; these reference sera were generated from anthrax toxin immunized individuals and provide a standard for defining a protective vaccine response. These data suggest that a single dose of Valortim given by the convenient IM route of administration could provide protection for two months.
Preclinical studies suggest that Valortim has the potential to provide significant protection against anthrax infection when administered prophylactically (prior to the emergence of symptoms of anthrax infection), and it also may increase survival when administered therapeutically (once symptoms become evident).
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