Efficacy and Safety of CR6261 in an H1N1 Influenza Healthy Volunteer Human Challenge Model

-INCLUSION CRITERIA: 1. Greater than or equal to 18 and less than or equal to 45 years of age. 2. Non-smoker. 3. Willingness to remain in isolation for the duration of viral shedding (at a minimum 10 days) and to comply with all study requirements. 4. A male subject is eligible for the study if he agrees to practicing abstinence or using a condom with spermicide plus an acceptable form of contraception (see inclusion criteria 5) being used by any female partner from 4 weeks before to 12 weeks after intranasal challenge with influenza. 5. A female participant is eligible for this study if she is not pregnant or breast feeding and 1 of the following: * Of nonchildbearing potential (i.e., women who have had a hysterectomy or tubal ligation or are postmenopausal, as defined by no menses in greater than or equal to 1 year). * Of childbearing potential but agrees to practice effective contraception or abstinence for 4 weeks prior to and 8 weeks after administration of the influenza challenge virus. Acceptable methods of contraception include a male partner who is sterile and is the sole sexual partner of the female participant or a male partner who uses a condom with spermicide plus 1 or more of the following: 1) implants of levonorgestrel; 2) injectable progestogen; 3) an intrauterine device with a documented failure rate of \<1%; 4) oral contraceptives; and 5) double barrier method including diaphragm. 6. Willing to have samples stored for future research. 7. Prechallenge serum HAI titer against the challenge virus less than or equal to 1:10 within 60 days of admission for the study. 8. HIV uninfected confirmed by testing within 60 days of admission for the study. 9. Agrees to abstain from alcohol intake 24 hours before admission on Day -1, during the inpatient period of the study, and 24 hours prior to all other outpatient clinic visits. 10. Agrees to not use over-the-counter medications (including aspirin, decongestants, antihistamines, and other NSAIDs), and herbal medication (including, but not limited to, herbal tea, St. John s Wort), within 14 days prior to study drug administration through the final follow-up visit, unless approved by the investigator. EXCLUSION CRITERIA: 1. Presence of self-reported or medically documented significant medical condition including but not limited to: 1. Chronic pulmonary disease (e.g., asthma, emphysema). 2. Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects). 3. Chronic medical conditions requiring close medical follow-up or hospitalization during the past 5 years (e.g., insulin dependent diabetes mellitus, renal dysfunction, hemoglobinopathies). 4. Immunosuppression or ongoing malignancy. 5. Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures). 6. Postinfectious or postvaccine neurological sequelae. 7. Hyperlipidemia requiring medical therapy per current American College of Cardiology (ACC) and American Heart Association (AHA) guidelines published in 2013. 2. Have close or household (i.e., share the same apartment or house) high-risk contacts including but not limited to: 1. Persons greater than or equal to 65 years of age. 2. Children less than or equal to 5 years of age. 3. Residents of nursing homes. 4. Persons of any age with significant chronic medical conditions such as: * Chronic pulmonary disease (e.g., severe asthma, COPD). * Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects). * Contacts who required medical follow-up or hospitalization during the past 5 years because of chronic metabolic disease (e.g., insulin dependent diabetes mellitus, renal dysfunction, hemoglobinopathies). * Immunosuppression or cancer. * Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures). * Individuals who are receiving long-term aspirin therapy. * Women who are pregnant or who are trying to become pregnant. 3. Positive serology for hepatitis C virus antibody or hepatitis B surface antigen. 4. Individual with body mass index (BMI) greater than or equal to 18 and greater than or equal to 35 or weight \> 114kg. 5. Acute illness within 7 days of admission and inoculation with the challenge virus (Day -1). 6. Complete blood count (CBC) with differential outside of the NIH Department of Laboratory Medicine (DLM) normal reference range and deemed clinically significant by the PI. 7. Chemistries in the acute care, mineral, and/or hepatic panels, and/or any of the following: lactate dehydrogenase, uric acid, creatine kinase, and total protein outside of the NIH DLM normal reference range and deemed clinically significant by the PI. 8. Amylase or Lipase outside of the NIH DLM normal reference range and deemed clinically significant by the PI. 9. Urinalysis outside of the NIH DLM normal reference range and deemed clinically significant by the PI. 10. Clinically significant abnormality as deemed by the PI on electrocardiogram. 11. Clinically significant abnormality as deemed by the PI on echocardiographic (ECHO) testing. 12. Clinically significant abnormality as deemed by the PI on the Pulmonary Function Test (PFT). 13. Known allergy to treatments for influenza (including but not limited to oseltamivir, nonsteroidals). 14. Known allergy to 2 or more classes of antibiotics (e.g., penicillins, cephalosporins, fluoroquinolones, or glycopeptides). 15. Receipt of blood or blood products (including immunoglobulins) within 3 months prior to enrollment. 16. Receipt of any unlicensed drug within 3 months or 5.5 half-lives (whichever is greater) prior to enrollment. 17. Receipt of any non-influenza-related unlicensed vaccine within 6 months prior to enrollment. 18. Self-reported or known history of current alcoholism or drug abuse, or positive urine/serum test for drugs of abuse and/or ethanol (i.e., amphetamines, cocaine, benzodiazepines, opiates, or metabolites, but not tetrahydrocannabinol (THC) or metabolites). 19. Self-reported or known history of psychiatric or psychological issues deemed by the PI to be a contraindication to protocol participation. 19\. Known close contact with anyone known to have influenza in the past 7 days. 21\. Known or suspected hypersensitivity to CR6261 or its excipients (sucrose, L-histidine, L-histidine monohydrochloride, polysorbate 20). 22\. History of a previous severe allergic reaction with generalized urticaria, angioedema, or anaphylaxis. 23\. Drinks more than 1200 mL (or 5 cups of 240 mL per cup) of tea/coffee/cocoa/cola or other caffeinated beverage per day more than 1 day per week in the 2 weeks before screening. 24\. Any condition or event that, in the judgment of the PI, is a contraindication to protocol participation or impairs the volunteer s ability to give informed consent.