Pharmacokinetic, Pharmacodynamic, Safety, and Efficacy Study of Rivaroxaban for Thromboprophylaxis in Pediatric Participants 2 to 8 Years of Age After the Fontan Procedure

Part A: This part includes a 12-day Initial PK, PD, and Safety Assessment Period.
Participants in Part A will not participate in Part B. Randomization in Part B of this study
will begin once the cumulative data from the Initial PK, PD, and Safety Assessment Period in
Part A are deemed acceptable by the Independent Data Monitoring Committee. Part A of the
study will consist of an up to 21-day Screening Period, a 12-day Initial PK, PD, and Safety
Assessment Period, a 12-month Open-Label Treatment Period, and a 30-day Follow-Up phone
contact. Part B: Participants will be randomly assigned to two treatment groups and
randomization ratio will be 2:1 for rivaroxaban and ASA. ASA will be used as control. There
will be an up to a 21-day Screening Period, a 12 month Open-Label Treatment Period and a
30-day Follow-Up phone contact.

Inclusion Criteria:

- Participant must be considered to be clinically stable by the investigator and able to
tolerate oral or enteral administration of a suspension formulation and oral/enteral
feedings

- Satisfactory initial post-Fontan transthoracic echocardiographic Screening as defined
in the Post-Fontan Echocardiographic Examination Research Protocol

- Parent/legally acceptable representative must sign an informed consent form (ICF) and
child assent will also be provided, if applicable, according to local requirements

Exclusion Criteria:

- Evidence of thrombosis, including those that are asymptomatic confirmed by post-Fontan
procedure transthoracic echocardiogram, or other imaging techniques, during the
Screening period of the study

- History of gastrointestinal disease or surgery associated with clinically relevant
impaired absorption

- History of or signs/symptoms suggestive of protein-losing enteropathy

- Active bleeding or high risk for bleeding contraindicating antiplatelet or
anticoagulant therapy, including a history of intracranial bleeding

- Platelet count less than (<)50*10^9/Liters (L) at Screening

- Estimated glomerular filtration rate (eGFR) <30 milliliters per minute per 1.73 meter
square (mL/min/1.73m^2)

- Known clinically significant liver disease