The purpose of this study is to evaluate safety, tolerability, and PK/PD of M281 after single and multiple doses in healthy volunteers.

Inclusion Criteria:

1. Healthy male or female subjects between 18 and 55 years, inclusive.
2. Good health
3. Body weight between 50 and 110 kg inclusive

Exclusion Criteria:

1. History of any drug allergy, hypersensitivity, or intolerance to any drug product that in the opinion of the Investigator would place the subject at particular risk and compromise the safety of the subject in the study.
2. History or presence of clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, gastrointestinal, endocrine, immunologic, dermatologic, neurologic, oncologic, psychiatric disease, or any other condition, that in the opinion of the Investigator would jeopardize the safety of the subject or the validity of the study results.
3. History or current diagnosis of substance dependence (except nicotine and caffeine) or alcohol abuse over the past 2 years, according to the criteria of DSM-IV-TR.
4. Smokes or has smoked more than 5 cigarettes per day in the last 90 days and is unable to stop smoking during in-patient observation period in clinic.
5. Unwillingness to abstain from alcohol for at least 24 hours prior to dosing with study medication until the time of discharge from the study unit and at least 24 hours prior to each ambulatory visit.
6. Plans to participate in another clinical trial while enrolled in this study and/or received an investigational drug and/or device within 60 days prior to admission.
7. Donation or significant loss of whole blood (480 mL or more) within 30 days or plasma within 14 days prior to admission.
8. History of splenectomy, asthma (with the exception of childhood asthma that has resolved), COPD, recurrent or current GI or respiratory infections.
9. On fluid restriction.
10. Systemic steroids within 3 months prior to the start of study drug administration, or any prescription medication(s) within 14 days of dose administration or any non-prescribed systemic or topical medication (including any herbal product) within 7 days prior to dose administration.
11. Vaccination within 1 month before dosing, or plans to receive vaccination during the study.
12. Any illness within 5 days, or clinically significant airway infections within 30 days, prior to first study drug dosing.
13. Positive urine drug screen (UDS) at screening.
14. Positivity for human immunodeficiency virus (HIV), hepatitis B, or hepatitis C at screening.