Pilot Study to Determine Effects of the Btk Inhibitor PCI-32765 on Leukemia Cell Kinetics and Trafficking, Using Heavy Water Labeling in Subjects With CLL and SLL

50 ml 70% 2H2O 3 times a day for the first 5 days followed by 60 ml daily for a total of 4 weeks. After the 5-day loading period, a 60 ml maintenance dose of 2H2O will be drunk at bedtime. At end of the 4th week, subjects stop drinking 2H2O (washout phase) and be followed from 6-12 weeks until beginning treatment with PCI-32765.

420 mg orally once daily.