Respiratory Syncytial Virus (RSV) Human Challenge Study of Molnupiravir in Healthy Participants (MK-4482-017)

Inclusion Criteria

• Is in good health based on medical history, physical examination, vital sign measurements, spirometry, and electrocardiograms (ECGs) performed before randomization.
• Has a total body weight ≥50 kg and Body Mass Index (BMI) ≥18 kg/m^2 and ≤35 kg/m^2.
• For males, agrees to abstain from heterosexual intercourse OR use contraception unless confirmed to be azoospermic during the study and for 90 days after.
• For females, is not pregnant or breastfeeding, AND is either not a woman of childbearing potential (WOCBP) or is a WOCBP AND uses a highly effective contraceptive (low user dependency OR a user dependent hormonal method in combination with a barrier method), has a negative highly sensitive pregnancy test at screening, and has medical, menstrual, and recent sexual activity history reviewed by the investigator to decrease risk of early undetected pregnancy.

Exclusion Criteria

• Has a history of, or currently active, symptoms or signs suggestive of upper or lower respiratory tract infection within 4 weeks prior to the first study visit.
• Has a history of clinically significant endocrine, gastrointestinal (GI), cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary, or major neurological (including stroke and chronic seizures) abnormalities or diseases.
• Has a history of resolved depression and/or anxiety 1 or more years ago may be included at the discretion of the investigator.
• Has a history of cancer (malignancy).
• Has a history of rhinitis (including hay fever) which is clinically active or history of moderate to severe rhinitis, or history of seasonal allergic rhinitis likely to be active at the time of inclusion into the study and/or requiring regular nasal corticosteroids on an at least weekly basis, within 30 days of admission to quarantine.
• Has a history of atopic dermatitis/eczema which is clinically severe and/or requiring moderate to large amounts of daily dermal corticosteroids.
• If the reporting physician has diagnosed migraine can be included, provided there are no associated neurological symptoms such as hemiplegia or visual loss.
• If there is a physician diagnosed mild Irritable Bowel Syndrome not requiring regular treatment, can be included at the discretion of the investigator.
• Uses or anticipates use during study of herbal supplements within 7 days prior to Viral Challenge, any cytochrome P450 (CYP450)-inhibiting medications within 21 days prior to Viral Challenge, any over-the-counter medications (eg, ibuprofen) within 7 days prior to Viral Challenge, or any systemic anti-viral administration within 4 weeks of Viral Challenge/first dosing of study medication.
• Has evidence of receipt of vaccine within the 4 weeks prior to the planned date of viral challenge/first dosing with study medication (whichever occurs first).
• Intends to receive any vaccine before the last study visit.
• Has received any investigational drug within 3 months or 5 half-lives (whichever is greater) prior to the planned date of viral challenge/first dosing with study medication (whichever occurs first).
• Has received ≥3 investigational drugs in the past 12 months.
• Has had a prior inoculation with a virus from the same family as the challenge virus.
• Has smoked ≥10 pack years at any time (one pack of 20 cigarettes a day for 10 years).
• Has a recent history or presence of alcohol addiction, or excessive use of alcohol (weekly intake in excess of 28 units alcohol; 1 unit being a half glass of beer, a small glass of wine or a measure of spirits), or excessive consumption of xanthine-containing substances (eg, daily intake in excess of 5 cups of caffeinated drinks such as coffee, tea, cola).
• Has a lifetime history of anaphylaxis and/or a lifetime history of severe allergic reaction.
• Has any significant abnormality altering the anatomy of the nose in a substantial way or nasopharynx that may interfere with the aims of the study and, in particular, any of the nasal