A phase III, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of idelalisib (GS-1101) in combination with bendamustine and rituximab for previously treated chronic lymphocytic leukemia (CLL)

TPS7133

Background: PI3K-delta is critical for the activation, proliferation and survival of B cells and plays a role in homing and retention of B cells in lymphoid tissues. PI3Kδ signaling is hyperactive in many B-cell malignancies. Idelalisib is a first-in-class, selective, oral inhibitor of PI3Kδ that reduces proliferation, enhances apoptosis, and alters trafficking of malignant B cells in lymphoid tissues (Lannutti, 2011). Phase 1 trials demonstrated that idelalisib is highly active in heavily pretreated pts with CLL as a single agent or in combination with rituximab (R), bendamustine (B), or BR: pts experienced reductions in disease-associated chemokines, profound and rapid reductions in lymphadenopathy, and durable clinical benefit with an acceptable safety profile (Coutre et al, 2012; Sharman et al, 2011). Methods: Study will enroll 390 pts with previously treated CLL who have measurable lymphadenopathy, have received prior therapy containing a purine analog or B and an anti-CD20 monoclonal antibody, are not refractory to B, have experienced CLL progression within 36 months from the completion of the last prior therapy, and are currently sufficiently fit to receive cytotoxic therapy. Pts are randomized in a 1:1 ratio to Arm A or B. On Arm A, subjects receive idelalisib continuously at 150 mg BID + R at 375 mg/m2 (1st dose) and then 500 mg/m2 every 4 weeks for 6 cycles + B at 70 mg/m2 on Days 1 and 2 of each 4-week cycle for 6 cycles. On Arm B, subjects receive placebo instead of idelalisib. Stratification factors address IGHV mutational status, del(17p)/p53 mutation status, and refractory vs relapsed disease. The primary endpoint is PFS and key secondary endpoints include ORR, lymph node response rate, CR rate, and OS. This is an event-driven trial and primary endpoint evaluation will be based on independent central review. For the primary efficacy analysis, the difference in PFS between the treatment arms will be assessed in the ITT analysis set. The study was initiated in June 2012 and a data monitoring committee has begun regular review of data. Clinical trial information: NCT01569295.

Update on a phase I study of the selective PI3Kδ inhibitor idelalisib (GS-1101) in combination with rituximab and/or bendamustine in patients with relapsed or refractory CLL

7017

Background: PI3K-delta signaling is critical for proliferation, survival, homing and tissue retention of malignant B cells. Idelalisib is a first-in-class, selective, oral inhibitor of PI3Kδ that has shown considerable monotherapy activity in pts with heavily pretreated CLL. Methods: This phase I study evaluated idelalisib continuously given at 150 mg BID in combination with rituximab (R, 375 mg/m2 every wk x 8), bendamustine (B, 70 or 90 mg/m2 x 2, every 4 wks x 6) or BR (every 4 wks x 6) for relapsed/refractory CLL. Pts still on treatment after 48 weeks were eligible to continue idelalisib on an extension study. Clinical response was evaluated according to published criteria (Hallek 2008; Cheson 2012). Results: 52 pts (23F/29M) with a median (range) age of 64 (41-87) years were enrolled. Adverse disease characteristics included bulky lymphadenopathy (62%), refractory disease (50%), multiple prior therapies (median 3, range: 1-14) with 96% receiving prior R and 44% receiving prior B. As of 14 Jan 2013, the median (range) treatment duration was 18 (1-33) months. 31/52 (60%) pts enrolled into the extension study; of those, 24/52 (46%) pts are continuing idelalisib treatment on the extension study. The ORR was 81%, with 1 CR, and a median (range) time to response of 1.9 (1.5-8.3) months. The 2-year PFS and OS were 62% and 85%, respectively. At 2 years follow up, 71% of responses were still enduring. There was no difference in outcomes for pts with <3 prior treatments (n=21) vs ≥3 prior treatments (n=31). The most common TEAEs (any Grade/≥Gr 3, independent of causality) included pyrexia (44%/6%), diarrhea (40%/14%), cough (31%/2%), fatigue (29%/2%), nausea (29%/0%). Pneumonia (any Gr/≥Gr 3) occurred in 15%/12% and rash was seen in 15%/0%. 10% of patients experienced ≥Gr 3 ALT/AST elevation based on laboratory values. Conclusions: A lack of overlapping toxicities allowed idelalisib to be co-administered with R, B, or BR, and all 3 combination regimens were highly active, resulting in durable tumor control in pts with heavily pretreated relapsed/refractory CLL. Phase III trials evaluating the efficacy of idelalisib in combination with R or BR are ongoing. Clinical trial information: NCT01088048.

Final results of a phase I study of idelalisib (GSE1101) a selective inhibitor of PI3Kδ, in patients with relapsed or refractory CLL

7003

Background: Signals through PI3K-delta regulate activation, proliferation and survival of B cells, critically influence homing and retention of B cells in lymphoid tissues, and are hyperactive in many BEcell malignancies. Idelalisib (GS-1101) is a first-in-class, selective, oral inhibitor of PI3Kδ that reduces proliferation, enhances apoptosis, and inhibits homing and retention of malignant B cells. Methods: Pts with relapsed/refractory CLL were treated continuously with single-agent oral idelalisib from 50E350 mg/dose (QD or BID). Response evaluated by investigators per Hallek (2008) and Cheson (2012). Results: 54 pts (9F/45M) median (range) age 63 (37E82) years enrolled with: bulky lymphadenopathy (80%), refractory disease (70%), extensive prior therapies (median: 5, range: 2E14), unmutated IgHV (91%), del17p and/or TP53 mutation (24%), del11q (28%), NOTCH1 mutation (17%). The median (range) exposure was 9 (0E41+) months. 25 (46%) pts completed the primary study, 23 (43%) enrolled into an extension study. ORR was 30/54 (56%, 2 CR, 28 PR). Of the 28 PR, 22 met Hallek (2008) and 6 met PR with lymphocytosis Cheson (2012). 44/54 (81%) showed a lymph node response (≥50% reduction in the nodal SPD). 21/54 were SD and 3/54 NE. The median (range) time to first response was 1.9 (0.9-12.9) months. Median PFS was 17 months and median DOR was 18 months. Idelalisib treatment resulted in resolution of splenomegaly (14/20, 70%) and normalization of cytopenias: anemia (17/25, 68%); thrombocytopenia (27/34 79%), neutropenia (15/15, 100%). Most common AEs independent of causality (any Grade/≥Gr 3) included fatigue (31%/2%), diarrhea (30%/6%), pyrexia (30%/4%), rash (22%/0%), upper respiratory tract infection (22%/0%), pneumonia (20%/19%). 2% of pts had ≥Gr 3 ALT/AST elevation. 15% of pts discontinued due to AEs, 7% potentially treatment-related. There were no dose-limiting toxicities. Conclusions: Idelalisib shows substantial clinical activity and a favorable safety profile in heavily pretreated, refractory and highErisk pts with CLL. Phase 3 trials with idelalisib in combination with rituximab or bendamustine/rituximab are ongoing. Clinical trial information: NCT01539512, NCT01569295.

A phase I/II study of the selective phosphatidylinositol 3-kinase-delta (PI3Kδ) inhibitor, GS-1101 (CAL-101), with ofatumumab in patients with previously treated chronic lymphocytic leukemia (CLL)

6518^

Background: PI3Kδ is expressed in cells of hematopoietic origin where it regulates the survival and proliferation of malignant B-cells. GS-1101 is an orally bioavailable, small-molecule inhibitor that selectively targets PI3Kδ and is highly active in patients with hematologic malignancies. Methods: This Phase 1/2 study evaluated repeated 28-day cycles of GS‑1101 in combination with ofatumumab. GS-1101 (150mg BID) was co-administered with a total of 12 infusions of ofatumumab over 24 weeks (300mg initial dose either on Day 1 or Day 2 (relative to the first dose of GS-1101), followed 1 week later by 1,000mg weekly for 7 doses, followed 4 weeks later by 1,000mg every 4 weeks for 4 doses). Thereafter, each subjects received single-agent GS‑1101 as long as the subject was benefitting. Results: Accrual is complete with 21 subjects enrolled and 11 evaluable. Six subjects started ofatumumab treatment on Day 1 and 5 on Day 2. Median [range] age was 63 [54‑76] years. The majority (9/11; 82%) of patients had bulky adenopathy. The median [range] number of prior therapies was 3 [1‑6], including prior exposure to alkylating agents (10/11; 90%), rituximab (9/11; 82%), purine analogs (8/11; 72%), alemtuzumab (3/11; 28%) and/or ofatumumab (2/11;18%). At the data cutoff, the median [range] treatment duration was 5 [0‑7] cycles. Almost all subjects (9/11;82%) experienced marked and rapid reductions in lymphadenopathy within the first 2 cycles. The lymphocyte mobilization that is expected with PI3Kδ inhibition was significantly reduced in magnitude and duration and persisted past Cycle 1 in only 1 patient. Early follow up data support a favorable safety profile and confirm a lack of clinically significant myelosuppression. Elevated baseline levels of CCL3, CCL4, CXCL13, and TNFa were significantly reduced after 28 days of treatment. Conclusions: GS-1101/ofatumumab offers a well-tolerated noncytotoxic combination regimen with substantial activity in previously treated patient with bulky adenopathy. Data on the complete cohort of 21 subjects will be presented.