Inclusion Criteria:

1. Healthy male or female subjects between the ages of 18-50 inclusive at the time of enrollment. In each of the drug cohorts (subgroups), at least three of the subjects must be female.
2. The following screening laboratory parameters must be within 5% of the normal range: CBC (excluding WBC) and coagulation tests (aPTT, PT and INR). Absolute counts of WBC must be within 10% of the normal range. BUN, creatinine, and total and direct bilirubin may be up to 10% above the upper limits of normal. AST, ALT and alkaline phosphatase must be within normal limits. Urinalysis must be within generally accepted normal limits.

3. The values for the following tests at screening are to be:

   G-6-P dehydrogenase - normal HBsAg - negative HBV - negative (except immunized subjects may have positive anti-HBs) Anti-HCV - negative Anti-HIV (HIV antibody test) - negative Urine drug screen (including cotinine) - negative

4. Female subjects must agree to practice heterosexual abstinence or to use a licensed, effective form of birth control (e.g., oral contraceptives, diaphragm or condom in combination with contraceptive jelly, cream or foam, intrauterine contraceptive device, Depo-Provera®, skin patch, vaginal ring, or cervical cap) for at least 30 days prior to enrollment and for the duration of the study, including the follow-up period. Females using hormonal contraceptives must agree to use at least one other method for at least 30 days prior to enrollment and for the duration of the study, including the follow-up period.
5. Female subjects must have a negative pregnancy test.
6. No history of hospitalization for illness within the six months prior to study enrollment.
7. Nonsmoker or ex-smoker. If a subject is an ex-smoker, he/she must not have used nicotine for at least 6 months prior to enrollment. This will be confirmed by a negative urine test for cotinine. Exceptions may be made for sporadic users with negative urine cotinine tests; this will be determined on a case-by-case basis.
8. Able to spend the two days specified in the study schedule confined in a facility under study rules.
9. Able to read, understand and sign the informed consent form

Exclusion Criteria:

1. Routine consumption of any medication (prescription or OTC), vitamin, mineral, or dietary supplement, for one week before and during the study. The sole exceptions are hormonal contraceptive agents, as detailed above.

   The withdrawal time for any prescription medication should be no less than 1 week prior to the beginning of the study.

2. Blood pressure greater than 139 mm Hg systolic and 89 mm Hg diastolic. Repeat measurements are allowed.
3. Contraindication to the use of any monoclonal antibody: history of allergic reactions to any biologic or formulation component
4. Medical condition that in the Investigator's opinion could adversely impact the subject's participation, safety or conduct of the study.
5. Subject has taken an investigational medication in the previous three months.
6. The subject has a history of drug or alcohol abuse within the past two years.
7. The subject is female and plans to become pregnant during the whole study period or 6 months.
8. Calculated Body Mass Index (BMI) greater than 35.0 or less than 18.5.
9. The subject has been previously vaccinated with anthrax or has participated in clinical research involving anthrax.

10. Any ECG abnormality except for the following:

    • Sinus bradycardia, no lower than 46 beats per minute in younger, athletic subjects
    • Sinus tachycardia if the heart rate is within normal limits when vital signs are measured
    • Respiratory arrhythmia
    • Mild first degree A-V block (P-R interval < 0.23 sec)
    • Incomplete right bundle branch block
    • Left anterior hemiblock
    • Ectopic atrial focus
    • Premature atrial contractions
    • Unifocal premature ventricular contractions
    • Mild right or left axis deviation
    • Indeterminate axis
    • J-point elevation