Venetoclax With High-dose Ibrutinib for CLL Progressing on Single Agent Ibrutinib

This is phase 1 study for patients with CLL or small lymphocytic lymphoma (SLL) experiencing disease progression on single ibrutinib. This study will evaluate the optimal ibrutinib dose (including doses higher than 420 mg) when combined with venetoclax During the screening period, patients will continue on ibrutinib at their previous tolerated dose, unless required to stop (e.g.: by a preceding clinical trial). On cycle 1, day 1, the dose of ibrutinib will be assigned based on the dose cohort. Patients in cohort 1 will receive ibrutinib 420 mg PO daily. Patients in cohort 2 will receive ibrutinib 560 mg PO daily. Cohort 3 will be 840 mg PO daily. On cycle 1, day 1, patients will initiate venetoclax. The dose of venetoclax will ramp-up from 20 mg PO daily to 400 mg PO daily over a 5 week period. The primary safety endpoint is determination of DLTs during the first 35 days (completion of dose ramp up). The primary efficacy endpoint of overall response rate will be assessed on approximately Cycle 7, Day 1. Rationale: The optimal management of patients that progress on ibrutinib, including those with acquired Btk or PLCg2 mutations, is not determined. In other cancers, continued treatment with small molecule inhibitors beyond disease progression provides significant benefit, with additional agents or adjustments to ablate the resistant subclone. Venetoclax is approved for the treatment of patients with CLL, and is well-tolerated and effective in high-risk disease, and so is an appropriate agent for this trial.