Inclusion Criteria:

   - Subject must have a diagnosis of CLL that meets 2008 Modified International Workshop
   on Chronic Lymphocytic Leukemia National Cancer Institute-Working Group (iwCLL NCI-WG)
   criteria

   - Subject has relapsed/refractory disease with an indication for treatment

   - Subject has refractory disease or developed recurrence after therapy with a BCR PI

   - Subject must have an Eastern Cooperative Oncology Group performance score of equal to
   or less than 2

   - Subject must have adequate bone marrow function at Screening

   - Subject must have adequate coagulation profile, renal, and hepatic function, per
   laboratory reference range at Screening

Exclusion Criteria:

   - Subject has undergone an allogeneic stem cell transplant within the past year

   - Subject has developed Richter's transformation confirmed by biopsy

   - Subject has active and uncontrolled autoimmune cytopenia

   - Subject has malabsorption syndrome or other condition that precludes enteral route of
   administration

   - Subject is human immunodeficiency virus (HIV) positive or has chronic hepatitis B or
   hepatitis C virus requiring treatment

   - Subject has known contraindication or allergy to both xanthine oxidase inhibitors and
   rasburicase.