Assessment of the Immunogenicity and Safety of a Dose-Sparing BioThrax® AVA Schedule

This is a Phase IV, randomized, open-label immunogenicity and safety study to evaluate four
dosing regimens of BioThrax® for Post-Exposure Prophylaxis (PEP) for anthrax. BioThrax® will
be administered as a subcutaneous (SC) injection for the primary series and will be
administered as an intramuscular (IM) injection for the boost. The four dosing regimens
are: 0.50mL BioThrax® on Days 0, 14, and 6 month boost; 0.50mL BioThrax® on Days 0, 28 and 6
month boost; 0.50mL BioThrax® on Days 0, 14, 28 and 6 month boost and 0.25mL BioThrax® on
Days 0, 14, and 28, 6 month boost with 0.50ml IM Approximately 300 subjects will be
randomized 1:1:1:1 to one of the four study arms. Enrollment will be stratified by gender,
with approximately equal numbers of males and females (18 through 65 years) enrolled into
each dosing regimen. The Primary objective is to evaluate the immunogenicity of the four
dosing regimens of BioThrax® using the Toxin Neutralization Assay (TNA). The secondary
objective is to evaluate the safety of the four dosing regimens of BioThrax®.

Inclusion Criteria:

- Subject able to provide informed consent;

- Female or male, 18 through 65 years of age, inclusive;

- If the subject is female and of childbearing potential, she agrees to practice
abstinence from sexual intercourse with men (vaginal penetration by a penis, coitus)
or use acceptable contraception, initiated at least 30 days prior to the first study
vaccination through 56 days after the 6 month boost vaccination in order to avoid
pregnancy:

1. A woman is considered of childbearing potential unless post-menopausal (>/= 1
year without menses) or surgically sterilized (tubal ligation, bilateral
oophorectomy, or hysterectomy)

2. Acceptable contraception methods are restricted to effective devices (IUDs,
NuvaRing®) or licensed hormonal products with use of method for a minimum of 30
days prior to vaccination, condoms with spermicidal agents, monogamous
relationship with a vasectomized partner who has been vasectomized for 6 months
or more prior to study entry, or successful Essure placement with documented
confirmation test at least 3 months after the procedure, and any other Food and
Drug Administration (FDA)-approved contraceptive method

- Be willing and able to return for all visits and blood collections for the duration
of the study;

- Be able to understand and comply with planned study procedures;

- Agree to complete the memory aid and to report concomitant medications and Adverse
Events during the study period.

Further clarification of inclusion/exclusion criteria:

Provided a subject meets all study inclusion criteria and none of the study exclusion
criteria, the following conditions will not exclude the subject from study participation:

- History of gestational diabetes;

- Type II diabetes controlled with diet or oral hypoglycemic medications;

- Treated, controlled, uncomplicated hypertension;

- History of coronary artery disease, asymptomatic (New York Heart Association [NYHA]
Function Class I), on a stable medical regimen. Persons meeting these criteria must
be at least two years post-myocardial infarction, cardiac bypass surgery and/or
percutaneous coronary interventions (e.g., angioplasty, stent placement) in order to
qualify. Persons with a history of cardiac disease must be under the care of a
physician;

- Cured, non-metastatic cancer (excluding hematologic malignancies), disease-free for
five years;

- Localized skin cancer, resected (including squamous cell and basal cell carcinomas).
Participants with a history of melanoma must be disease-free for five years;

- Exercise-induced bronchospasm controlled with inhaled medication(s) only;

- Mild asthma: Subjects who have not been hospitalized for asthma in the past two years
and use only inhalers to control their symptoms will be eligible. Only low to medium
doses of inhaled steroids, defined as require oral or parenteral steroids will not be eligible.

- Subjects with isolated entrapment neuropathies, such as carpal tunnel syndrome, or
compression neuropathies, such as lumbar radiculopathy, that are not associated with
systemic disease or immune dysfunction may be eligible for enrollment. If the
subject's condition has been stable for six months, surgery is not planned for the
condition, the neurologic examination is normal (specifically no weakness or
paresthesias), and the mononeuropathy will not interfere with the assessment of
reactogenicity, the subject is eligible.

- Subjects with vitiligo who are otherwise healthy and the vitiligo is not widespread
in the area of the vaccinations may be eligible for enrollment.

- Subjects with seasonal allergies are eligible provided the dose of nasal steroids
that are used is < 800µg/day.

Exclusion Criteria:

- Have a prior history of anthrax or immunization against anthrax;

- Intend to enlist in the military during the study;

- Have a known allergy to aluminum hydroxide, formaldehyde, benzethonium chloride, or
latex;

- (Females only) Be pregnant, plan to become pregnant at any time between the Screening
Visit through 56 days after the 6 month boost vaccination, or refuse to use/not have
used an acceptable method of birth control (see Inclusion Criterion 3) from 30 days
prior to the first study vaccine dose through 56 days after the 6 month boost
vaccination;

- Have received experimental products within 30 days before study entry or plan to
receive experimental products at any time during the study;

- Have received a live vaccine within 30 days before study entry or plan to receive a
live vaccine prior to Day 63 of the study or within 30 days of the 6 month boost;

- Have received an inactivated vaccine within 14 days before study entry or plan to
receive an inactivated vaccine from Day 0 to Day 42 or within 14 days of the 6 month
boost;

- Have received immunosuppressive therapy (including systemic steroids) within 3 months
prior to study entry or plan to receive immunosuppressive therapy at any time during
the study;

- Have received cytotoxic therapy in the previous 5 years or plan to receive cytotoxic
therapy at any time during the study;

- Have received parenteral immunoglobulin or blood products within 3 months of the
study or plan to receive parenteral immunoglobulin or blood products at any time
during the study;

- Have a history of Guillain-Barré Syndrome;

- Have an active malignancy or history of metastatic or hematologic malignancy;

- Have Type I diabetes or Type II diabetes treated with insulin;

- Have cardiovascular disease (including any person with a history of cardiomyopathy or
congestive heart failure);

- Have moderate to severe asthma, chronic obstructive pulmonary disease or other
significant pulmonary disease;

- Have hepatic or renal insufficiency;

- Have an autoimmune, inflammatory, vasculitic or rheumatic disease including but not
limited to systemic lupus erythematosus, polymyalgia rheumatica, rheumatoid arthritis
or scleroderma;

- Have HIV, hepatitis B or hepatitis C infection;

- Have any other condition known to produce or be associated with immunosuppression;

- Have neuropathy or any other evolving neurological condition;

- Have an ongoing drug abuse/dependence (including alcohol) issues or a history of
these issues within five years of enrollment;

- Have a seizure disorder;

- Have moderate or severe illness and/or an oral temperature >100.4 F within 3 days
prior to vaccination;

- Have a blood pressure, heart rate or respiratory rate of Grade 2 or higher;

- Have any chronic condition that, in the opinion of the Investigator, would render
vaccination unsafe or would interfere with study evaluations or completion of the
study;

- Have a total White Blood Cell (WBC) count, Absolute Neutrophil Count (ANC),
hemoglobin or platelet count that is Grade 2 or higher;

- Have a creatinine higher than the normal range;

- Have an Alanine Aminotransferase (ALT) of >/= 1.2 x Upper Limit of Normal;

- Have a value higher than trace for glucose and/or protein on urinalysis;

- Have a history of hospitalization for psychiatric illness, suicide attempt, or
confinement for danger to self or others, within the past 10 years. (Subjects with a
psychiatric disorder [not meeting exclusion criteria, e.g. attention-deficit
hyperactivity disorder] that is controlled for a minimum of 3 months and the
investigator has determined that the subject's mental status will not compromise the
subject's ability to comply with protocol requirements may be enrolled);

- Be taking any of the following psychiatric drugs: aripiprazole, clozapine,
ziprasidone, haloperidol, molindone, loxapine, thioridazine, thiothixene, pimozide,
fluphenazine, risperidone, mesoridazine, quetiapine, trifluoperazine,
trifluopromazine, chlorprothixene, chlorpromazine, perphenazine, olanzapine,
carbamazepine, divalproex sodium, lithium carbonate or lithium citrate;

- Be taking more than one antidepressant drug not included in the list above (subjects
taking only one antidepressant drug [not listed in excluded psychiatric drugs] who
are stable for at least 3 months prior to enrollment without decompensating are
allowed enrollment into the study provided the investigator determines the subject's
mental status will not compromise the subject's ability to comply with protocol
requirements);

- Have donated blood within 30 days of enrollment or plans to donate blood during the
study.

- Have a tattoo in the area of the vaccination sites which will interfere with the
assessment of injection site reactogenicity.