A phase II study of the selective phosphatidylinositol 3-kinase delta (PI3K{delta}) inhibitor idelalisib (GS-1101) in combination with rituximab (R) in treatment-naive patients (pts) >=65 years with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).

7005 Background: PI3K-delta is critical for activation, proliferation and survival of B cells and plays a role in homing and retention in lymphoid tissues. PI3Kδ signaling is hyperactive in many B-cell malignancies. Idelalisib is a first-in-class, selective oral inhibitor of PI3Kδ. When combined with R in 19 relapsed/refractory patients with CLL, the ORR was 78% (Coutre, ASH 2012). Methods: Treatment-naive pts ≥65 yrs with CLL or SLL were treated with R 375 mg/m2 weekly x 8 and idelalisib 150 mg bid continuously for 48 weeks (primary study). Pts completing 48 wks w/o progression could continue to receive idelalisib on an extension study. Responses and progression were based on investigator assessment using IWCLL criteria (Hallek, Blood 2008). Results: Data is presented here on the first 50 of 64 pts enrolled, 48 CLL/2 SLL, median age 71 yrs (range: 65-89), M/F 70/30 (%), Rai stage III/IV 10/32 (%), nodes ≥5 cm in 16%, WHO 0/1/2 in 34/64/2 (%); del(17p) in 6 pts and del(11q) in 13 pts. 32 pts completed 48 ...