An Open-label, Nonrandomized Study to Evaluate the Safety and Immunogenicity of Raxibacumab With Reinjection

An Open-Label Study to Evaluate the Immunogenicity and Safety of Raxibacumab (Human Monoclonal Antibody to B. Anthracis Protective Antigen) Administered in Healthy Subjects

This is an open-label study to evaluate the immunogenicity and safety of raxibacumab in healthy adult male and female subjects. Subjects who have received raxibacumab >= 4 months ago will be enrolled and dosed as follows: A maximum of 25 subjects (to include 3 evaluable female subjects) will receive a second dose of raxibacumab equal to that of the previous dose >= 4 months following the first dose. Subjects will remain in house from Day 0 until Day 1 and will be followed for 70 days after receiving the second dose of raxibacumab. Raxibacumab has been shown to provide improved survival in rabbit and monkey anthrax spore challenge studies. Preliminary data from our rabbit pivotal efficacy study showed significant survival benefit for raxibacumab over placebo. Exposure to anthrax and resulting clinical disease can occur more than once, especially in individuals who do not develop protective immunity. Hence, if clinically indicated for the treatment of anthrax, there may be a requirement for the repeat administration of raxibacumab. The rationale of the study is to evaluate the immunogenicity and safety of repeat administration of raxibacumab with a >= 4 month interval between dosing.

Inclusion Criteria:

• Enrolled and treated with raxibacumab in another HGS protocol, >= 4 months ago.
• Male or female >= 18 and <= 64 years of age.
• Laboratory values that are Grade 0 by the modified Division of Microbiology and Infectious Diseases (DMID) toxicity tables. Subjects with laboratory values that are Grade 1 and are not considered clinically significant by the Principal Investigator may be enrolled following consultation with the Medical Monitor.
• A female subject is eligible to enter the study if she is: Not pregnant or nursing, Post menopausal, has had a hysterectomy, or documentation of sterility, Of child bearing potential (ie, woman with an intact uterus and ovaries and no documentation of oviductal or uterine dysfunction that would cause sterility).
• These women must have a negative blood pregnancy test at screening and on Day -1 prior to dosing and agree to 1 of the following: a)Complete abstinence from intercourse from the date of screening through the duration of follow-up, b)Consistent and correct use of 1 of the following medically accepted methods of birth control, in addition to a male partner who correctly uses a condom or is sterile prior to the female subject's entry into the study and is the sole sexual partner for the female subject from the date of screening through the duration of follow-up, implants of levonorgestrel; injectable progesterone; any intrauterine device (IUD) with a documented failure rate of less than 1% per year; oral contraceptives (either combined or progesterone only); double barrier method: condom, cervical cap or diaphragm with spermicidal agent; transdermal contraceptive patch.
• All males who are not sterile must agree to either abstain from intercourse or consistently and correctly use a condom while their female partner agrees to use 1 of the appropriate medically accepted methods of birth control listed above from the date of screening through the duration of follow-up.
• Have the ability to understand the requirements of the study, provide written informed consent (including consent for the use and disclosure of research-related health information), comply with the study protocol procedures, and agree to return for the required study visits.

Exclusion Criteria:

• History or clinical evidence of significant, acute, or chronic diseases (ie, cardiovascular, pulmonary, gastrointestinal, hepatic, renal, neurological, or infectious diseases), which could confound the results of the study or put the subject at undue risk.
• Prior immunization with anthrax vaccine adsorbed (AVA), prior treatment with investigational anthrax therapies (other than raxibacumab >= 4 months ago), prior treatment for anthrax exposure, or a confirmed anthrax infection.
• History of Type I hypersensitivity reaction to food or drugs, intravenous (IV) contrast dye, or history of urticaria.
• Previous hypersensitivity to raxibacumab.
• Previous serious or Grade 3 or greater raxibacumab related adverse event (AE).
• Drug or alcohol addiction within the last 12 months. Subjects who have documented addiction free period of at least 12 months and in the clinical judgement of the investigator are not at risk for relapse may be enrolled in the study.
• Evidence of active or suspected malignancy or history of malignancy within the last 5 years (with the exception of adequately treated basal cell carcinoma of the skin or in situ carcinoma of the cervix).
• Participation in any other clinical trials of an investigational compound within 60 days of initiating study agent or refusal to refrain from participation during this study.