A Comparison of the Safety, PD and PK of a Single Dose of SYN023 Administered With Licensed Rabies Vaccines

Inclusion Criteria: 1. Male or female subjects between 18 and 50 years of age, inclusive 2. Body mass index between 18 and 30 kg/m², inclusive 3. Female subjects physically capable of pregnancy (i.e., not sterilized and still menstruating or within 1 year of the last menses if menopausal) must: 1. Agree to avoid pregnancy from 28 days prior to Study Day 0 through the duration of the study. 2. If in a sexual relationship with a man, use an acceptable method of avoiding pregnancy during this period. Acceptable methods of avoiding pregnancy include: the use of at least two forms of contraception, including use by a partner of a barrier method (e.g., male condom with intravaginal spermicide) as one form of contraception. 4. Women of childbearing potential must have a negative serum pregnancy test within 24 hours preceding receipt of each dose. 5. Can understand and sign the informed consent document, can communicate with the investigator and provide updated contact information as needed for the duration of the study, has no current plans to move from the study area for the duration of the study, and can understand and comply with the requirements of the protocol. Exclusion Criteria: 1. Oral temperature ≥37.5°C at screening 2. Complete blood count (CBC) and platelet count abnormal values (\>5% above the upper limit of normal \[ULN\] or \>5% below the lower limit of normal \[LLN\] per local laboratory parameters) at screening with exception of absolute lymphocyte count. 3. Abnormally elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, alkaline phosphatase (ALP), or creatinine (Cr) values at screening (however a single test AST, ALT or ALP may be \>10% above the ULN per local laboratory parameters) 4. Abnormal PT (INR) PTT 5. Abnormal screening urinalysis result that is, per the investigator, clinically significant, or a screening urine dipstick result of ≥2+ protein 6. Positive screening urine test for illicit drugs (opiates, cocaine, amphetamines methamphetamines, barbiturates, benzodiazepines, tetrahydrocannabinol, PCP, MDMA, and methadone) 7. History or evidence of autoimmune disease 8. History or evidence of any past, present, or future possible immunodeficiency state, including laboratory evidence of human immunodeficiency virus (HIV) 1 or 2 infection 9. History or evidence of chronic hepatitis 10. History or evidence of rabies infection 11. History or evidence of any other acute or chronic disease that, in the opinion of the investigator, may interfere with the evaluation of the safety or immunogenicity of the drug or compromise the safety of the subject; for example a clinically relevant history of respiratory, thyroid, gastrointestinal, renal, hepatic, hematological, lymphatic, oncologic, cardiovascular, psychiatric, neurological, musculoskeletal, genitourinary, infective, inflammatory, immunological, dermatological or connective tissue disease 12. History or evidence of allergic disease or reaction, including adverse responses to therapeutic monoclonal antibodies that, in the opinion of the investigator, may compromise the safety of the subject 13. History of non-compliance that, in the opinion of the investigator, will make it unlikely that the subject will comply with the protocol 14. Previous exposure to rabies vaccine 15. Receipt of an immunoglobulin or blood product within 90 days prior to Study Day 0 16. Receipt of immunosuppressive medications other than inhaled or topical immunosuppressant drugs within 45 days prior to Study Day 0 17. Body weight greater than 90 kg. 18. History or evidence of IgA deficiency