A Phase 1b, randomized, partially double-blind, placebo-controlled study to assess the
pharmacokinetics, safety, and tolerability of multiple doses of orally administered
JNJ-53718678 in infants hospitalized with RSV infection

1. Each subject*s legally acceptable representative (ie, parent(s)/legal guardian/caregiver)
must sign an ICF indicating that he or she understands the purpose of and procedures
required for the study, are willing for their child to participate in the study, are willing
for their child to remain in the hospital for the first 3 days of dosing (even if not
clinically indicated), and are willing/able to adhere to the prohibitions and restrictions
specified in the protocol (see Section 4.3) and study procedures.
2. Subject has presented at the hospital for suspected RSV infection within 72 hours prior
to screening completion (ie, randomization).
3. Subject has been hospitalized for this suspected RSV infection.
4. Subject is a boy or a girl, who is >1 month to *24 months of age on the day of
randomization.
5. Subject has been diagnosed with RSV infection using a polymerase chain reaction
(PCR)-based assay, preferably commercially available locally.
Note: in case there is no commercially available PCR-based assay at the site, the
Sponsor should be consulted for agreement on the assay to be used.
6. Subject was born after a normal term pregnancy (*37 weeks and 0 days).
7. With the exception of the RSV-related illness, subject is otherwise in good health
without any significant medical illness on the basis of a medical evaluation that reveals
the absence of any clinically relevant abnormality and includes a physical examination,
skin examination, medical history, vital signs, ECG, and the results of blood
biochemistry, blood coagulation, and hematology tests performed at Screening. If there
are abnormalities, the subject may be included only if the Investigator judges the
abnormalities or deviations from normal to be not clinically significant. This
determination must be recorded in the subject*s source documents and initialed by the
Investigator.
Note: Procedures that are standard of care and performed within 72 hours prior to
screening completion (ie, randomization) may be used in determining study eligibility.

1. Subject is upon current admission initially hospitalized in the ICU and/or in need of
invasive endotracheal mechanical ventilation.
2. Subject has a history of any illness or a concurrent illness that, in the opinion of the
Investigator, might confound the results of the study or pose an additional risk in
administering study drug to the subject or that could prevent, limit or confound the
protocol-specified assessments. This may include, but is not limited to, bacteremia,
gross abnormalities, organ dysfunction, or severe comorbidity.
Note: The use of intravenous fluids is not exclusionary as long as the Investigator
believes the patient*s gastrointestinal tract still functions properly (i.e., is able to absorb
drugs or nutrition).
3. Subjects who had major surgery within the 28 days prior to randomization or planned
major surgery through the course of the study.
4. Subject has major congenital anomalies (eg, AV shunt) or known cytogenetic disorders
(eg, Down*s syndrome).
Note: Open ductus arteriosus and open foramen ovale are not exclusionary as not
considered major anomalies.
5. Subject has known or suspected immunodeficiency, such as known human
immunodeficiency virus (HIV) infection.
6. Subject has known or suspected hepatitis B or C infection.
7. Subject has known allergies, hypersensitivity, or intolerance to JNJ-53718678 or its
excipients.