Comparable outcomes in CLL patients treated with reduced-dose ibrutinib: Results from a multi-center study.

7529Background: Ibrutinib (Ibr) is a first-in-class oral covalent inhibitor of Bruton's tyrosine kinase (BTK) dosed according to FDA labeling at 420 mg daily to achieve > 90% BTK occupancy (≥ 2.5 mg/kg/day). Although fewer pts achieve > 90% occupancy at < 420 mg, it is unknown whether lower doses translate into inferior outcomes. To address this question, we conducted a multi-center study to capture experiences of CLL pts treated with Ibr below suggested starting doses. Methods: Multi-center, IRB approved, retrospective study of all Ibr-treated CLL pts between 2010-2015. Demographics, Ibr dose, responses, and outcomes were recorded. Reduced dose was defined as sustained Ibr dosing ( < 420 mg/day), reduced within 3 mos of initiation. The primary endpoint was PFS determined by the Kaplan Meier method, stratified by dose. For comparison, log rank tests and Cox regressions were performed. Results: 197 Ibr-treated CLL pts were identified, of which 37 (19%) received reduced dose Ibr. For reduced dose pts, media...