The Effect of Rivaroxaban in Sickle Cell Disease

The study will consist of a Screening Phase, two Treatment Phases, a Wash-Out Phase, and a Follow-up Phase. The Screening Phase will occur within 28 days of randomization and will include informed consent, a physical examination, and complete medical history to include determination of sickle cell genotype and current medications. Clinical laboratory tests to be performed include: a Complete Blood Count (CBC) with differential and reticulocyte count; Prothrombin time(PT) / activated partial thromboplastin time (aPTT); and serum chemistries (BUN, creatinine, total and direct bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, and LDH). A chest x-ray and MRI/MRA of the brain will also be done at Screening to rule out underlying disease. If the patient is found through the screening process to be eligible, the 1st Treatment Phase begins. Baseline safety assessments and measurement of biomarkers are completed, then the subject is randomized to receive rivaroxaban or placebo. After 4 weeks of treatment, there is a 2-Week Wash-Out Phase. After the Wash-Out Phase, another set of baseline studies are performed and the 2nd Treatment Phase begins. For this Phase of the study, the subject "crosses over" to receive whatever treatment - rivaroxaban or placebo - that they did not receive in the 1st Treatment Phase. After taking the assigned study drug for 4 weeks, the 2nd Treatment Phase ends. The subject returns 2 weeks after the last dose of study treatment for the Follow-Up Phase, consisting of a single end-of-study visit during which safety assessments are repeated.