The purpose of this study is to evaluate the effect of GS-1101 on the onset, magnitude, and duration of tumor control

This is a Phase 2, multicenter, single-arm, controlled, clinical trial evaluating the efficacy and safety of the phosphatidylinositol 3-kinase delta (PI3K-delta) inhibitor GS-1101 (CAL-101) as therapy for previously treated chronic lymphocytic leukemia.

This clinical trial (Study GS-US-312-0120) is a single-arm in which compliant subjects from GS US-312-0119 -Arm B who experience progression of CLL while receiving single-agent ofatumumab therapy are potentially eligible to receive single-agent, open-label GS 1101 therapy.

Inclusion Criteria:

• Participation in Study GS-US-312-0119
• Occurrence of confirmed progression of CLL while receiving single-agent ofatumumab in Study GS US 312 0119.
• Permanent cessation of Study GS-US-312-0119 (single-agent ofatumumab) and no intervening or continuing therapy (including radiotherapy, chemotherapy, immunotherapy, or investigational therapy) for the treatment of CLL.
• The time from permanent cessation of single-agent ofatumumab on Study GS-US-312-0119 and the initiation of GS 1101 on Study GS-US-312-0120 is no more than 12 weeks.