A phase II study of the selective phosphatidylinositol 3-kinase delta (PI3Kδ) 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).

Leukemia Myelodysplasia and Transplantation
Session Type and Session Title: 
Oral Abstract Session, Leukemia, Myelodysplasia, and Transplantation
Abstract Number: 
J Clin Oncol 31, 2013 (suppl; abstr 7005)
Susan Mary O'Brien, Nicole Lamanna, Thomas J. Kipps, Ian Flinn, Andrew David Zelenetz, Jan Andreas Burger, Leanne Holes, David Michael Johnson, Jessie Gu, Roger D. Dansey, Ronald L. Dubowy, Steven E. Coutre; The University of Texas MD Anderson Cancer Center, Houston, TX; Memorial Sloan-Kettering Cancer Center, New York, NY; UC San Diego Moores Cancer Center, La Jolla, CA; Sarah Cannon Research Institute, Nashville, TN; Gilead Sciences, Inc., Seattle, WA; Stanford Cancer Institute, Stanford, CA

Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).

Abstract Disclosures


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 wks (18 discontinued, 11 due to AE, 4 due to death and 3 other); 30 pts entered the extension study and 26 remain on treatment. The median time on treatment was 16 months (range 0.8-27.5). The ORRwas 96% with 4% nonevaluable; median time to response was 1.9 mos (range 1.0-6.5). There have been no on-study relapses. The Kaplan-Meier estimated PFS is 91% at 24 mos. Of note, 6/6 pts with del(17p) responded (1 CR, 5 PR) and 3 remain on treatment for more than 21 months. 13/14 (93%) pts with thrombocytopenia and 12/12 (100%) pts with anemia at baseline responded. Of 20 pts with B symptoms at baseline, 13 (65%) were asymptomatic by 8 wks. Most frequent AEs (total%/ ≥G3%) were diarrhea (including reported as colitis) (46/16), pyrexia (42/4), chills (34/0), fatigue (34/2), rash (34/10), pneumonia (30/20) and nausea (28/0). Elevated ALT/AST was seen in 60%, Gr ≥3 in 22%. Conclusions: Idelalisib + R is highly active, resulting in durable disease control in treatment-naïve older pts with CLL. These results support the further development of idelalisib in frontline CLL. Clinical trial information: NCT01203930.