A Phase 2a Study to Evaluate Orally Administered ALS-008176 in Adults Hospitalized With a Respiratory Syncytial Virus

Inclusion Criteria:

1. Subject is ≥50 years of age.

2. Female subjects of non-childbearing potential (i.e., surgically sterilized,
post-menopausal [amenorrhea for 1 year confirmed by negative hormone panel]) who also
have a negative pregnancy test at screening.

3. Male subjects must be either surgically sterilized (e.g., post-vasectomy or
orchiectomy) or willing to adhere to the study's contraceptive requirements. Male
subjects'female partner(s) must be surgically sterilized or post-menopausal
(amenorrhea for 1 year) or their female partner(s) of child-bearing potential must be
willing and able to adhere to the contraceptive requirements.

4. Each subject or their legal guardian must sign an informed consent form (ICF)
indicating that he or she understands the purpose of and procedures required for the
study and is willing to participate in the study before starting any screening
activities.

5. Subject has a positive RT-PCR test result for RSV at the time of screening. NOTE:
Co-infection with other acute viruses or bacteria is permitted.

6. Subject has been, or will be, admitted to the hospital for an acute respiratory
illness with signs and symptoms consistent with a viral infection (e.g., fever, cough,
nasal congestion, runny nose, sore throat, myalgia, lethargy, shortness of breath, or
wheezing) with onset <7 days from the anticipated time of randomization.

Exclusion Criteria:

1. Subject is undergoing peritoneal dialysis, hemodialysis or hemofiltration or has an
estimated glomerular filtration rate (GFR, determined by Cockcroft-Gault Formula) <30
mL/min.

2. Subject has presence of any concurrent illness, including laboratory, vital sign, ECG,
or physical exam findings, or medical history that, in the opinion of the
investigator, would place the subject at an unreasonably increased risk as a result of
participation in this study.

3. Subject reports receiving an investigational drug or vaccine within 30 days, or 5
half-lives (whichever is longer) prior to the planned first dose of study drug.

4. Subject has a known history of human immunodeficiency virus (HIV) or chronic, active
hepatitis infection.

5. ALT >3×ULN AND bilirubin >2×ULN (direct >35%) OR ALT>5×ULN

6. Subjects who have been hospitalized for >72 hours at the time of randomization.

7. Subjects anticipated to be hospitalized for <24 hours after randomization.

8. Subjects who are not expected to survive for <48 hours.

9. Recent (<5 half-lives) use, or anticipated use during conduct of the study, of
concomitant medications (prescription and non-prescription) which are inhibitors of
the OAT3 transporter.

10. Treatment of the current illness with drugs specifically targeting the RSV infection
itself (e.g., RSV immunoglobulin, ribavirin, palivizumab). Medications treating the
sequelae of the RSV infection or any concurrent illness are permitted if not otherwise
excluded.

11. Subjects unwilling to undergo regular nasal swab procedures or with any physical
abnormality which limits the ability to collect regular nasal specimens.

12. Subjects that are considered by the investigator to be immunocompromised over the past
12 months, whether due to underlying medical condition or medical therapy.

13. Subjects unable to take medications enterally (e.g., orally or via nasogastric or PEG
tube) or a known gastrointestinal-related condition that may interfere with study drug
absorption.

14. Female subject that is pregnant or breastfeeding

15. In the investigator's opinion, the subject is unwilling or unable to comply with
protocol requirements, instructions, and protocol stated restrictions, and is unlikely
to complete the study as planned.

16. Subject has known or suspected hypersensitivity to the study drug or its excipients
(microcrystalline cellulose, mannitol, croscarmellose sodium, magnesium stearate,
polyethylene glycol, polyvinyl alcohol, talc, titanium dioxide).