['respiratory syncytial virus infections']
['ak0529', 'placebo']

        Inclusion Criteria:

          1. Must be healthy males, or healthy females of non-childbearing potential or surgically
             sterilized or post-menopausal (amenorrhea for at least 1 year and confirmed by a
             follicle stimulating hormone [FSH] result of > 20 IU/mL).

          2. Must be aged 18 to 55 years of age inclusive.

          3. Must have body mass index (BMI) of 18.0 to 31.0 kg/m2 inclusive.

          4. Must have total body weight ≥50 kg at screening but ≤100 Kg.

          5. Must be willing and able to communicate and participate in the whole study.

          6. Must provide written informed consent.

          7. Must agree to use an adequate method of contraception (as defined in Section 4.2.1).

          8. Must have AST, ALT, total bilirubin, urea, creatinine and hemoglobin within the
             laboratory reference range at screening and Day -1.

          9. Must have QTcF <450 ms, QTcB <450 ms and PR interval <210 ms for screening, Day -1 and
             pre-dose ECG measurements, and not have any degree of heart block or conduction
             abnormality.

         10. Must have serology demonstrating they are free from infection with hepatitis B,
             hepatitis C, and human immunodeficiency virus (HIV-1 and HIV-2)

        Exclusion Criteria:

          1. Male subjects who have currently pregnant partners or who have partners planning to
             become pregnant during the duration of the study.

          2. Evidence or history of clinical significant oncological, pulmonary, chronic
             respiratory, hepatic, cardiovascular, hematological, metabolic, neurological,
             immunological, nephrological, endocrine or psychiatric disease, or current infection.

          3. Clinically relevant (as decided by the investigator and the medical monitor)
             abnormalities in the ECG (12 standard leads) including any degree of heart block,
             including asymptomatic bundle branch block.

          4. Family history of sudden death or of congenital prolongation of the QTc interval or
             known congenital prolongation of the QTc interval or any clinical condition known to
             prolong the QTc interval.

          5. History of symptomatic cardiac arrhythmias or with clinically relevant bradycardia.

          6. Electrolyte disturbances, particularly hypokalemia hypocalcemia or hypomagnesemia.

          7. Any condition that could possibly affect drug absorption, e.g. gastrectomy or
             diarrhea.

          8. History of post-antibiotic colitis.

          9. History of any drug or alcohol abuse in the past 2 years prior to screening.

         10. Regular alcohol consumption in males >21 units per week and females >14 units per week
             (1 unit = 400 mL beer, 25 mL of 40% spirit or a 75 mL glass of wine).

         11. Subjects who have a urine cotinine greater than 500 ng/mL at screening will be
             excluded. Subjects who are tobacco users (including smokers and users of snuff,
             chewing tobacco and other nicotine or nicotine-containing products) must have stopped
             use at least 90 days before screening.

         12. Receipt of an investigational drug or participation in another clinical research study
             within 90 days prior to drug administration.

         13. Subjects who are study site employees, or immediate family members of a study site or
             sponsor employee.

         14. Subjects who have previously been enrolled and dosed in this study, except subjects
             undergoing repeat dosing in Cohort 4F (the fed PK cohort of the SAD part of the
             study).

        Other protocol defined inclusion/exclusion criteria may apply.
      