Idelalisib, a selective inhibitor of phosphatidylinositol 3-kinase-δ, as therapy for previously treated indolent non-Hodgkin lymphoma

Idelalisib (GS-1101, CAL-101), an oral inhibitor of phosphatidylinositol 3-kinase-δ, was evaluated in a phase I study in 64 patients with relapsed indolent non-Hodgkin lymphoma (iNHL). Patients had a median (range) age of 64 (32-91) years, 34 (53%) had bulky disease (≥1 lymph nodes ≥5 cm), and 37 (58%) had refractory disease. Patients had received a median (range) of 4 (1-10) prior therapies. Eight dose regimens of idelalisib were evaluated; idelalisib was taken once or twice daily continuously at doses ranging from 50 to 350 mg. After 48 weeks, patients still benefitting (n = 19; 30%) enrolled into an extension study. Adverse events (AEs) occurring in 20% or more patients (total%/grade ≥3%) included diarrhea (36/8), fatigue (36/3), nausea (25/3), rash (25/3), pyrexia (20/3), and chills (20/0). Laboratory abnormalities included neutropenia (44/23), anemia (31/5), thrombocytopenia (25/11), and serum transaminase elevations (48/25). Twelve (19%) patients discontinued therapy due to AEs. Idelalisib induced disease regression in 46/54 (85%) of evaluable patients achieving an overall response rate of 30/64 (47%), with 1 patient having a complete response (1.6%). Median duration of response was 18.4 months, median progression-free survival was 7.6 months. Idelalisib is well tolerated and active in heavily pretreated, relapsed/refractory patients with iNHL. These trials were registered at clinicaltrials.gov as NCT00710528 and NCT01090414.

A phase 1 study of the PI3Kδ inhibitor idelalisib in patients with relapsed/refractory mantle cell lymphoma (MCL)

Idelalisib, an oral inhibitor of phosphatidylinositol-3-kinase δ (PI3Kδ), was evaluated in a 48-week phase 1 study (50-350 mg daily or twice daily) enrolling 40 patients with relapsed or refractory mantle cell lymphoma (MCL). Primary outcome was safety and dose-limiting toxicity (DLT). Secondary outcomes were pharmacokinetic parameters, pharmacodynamic effects, overall response rate (ORR), progression-free survival (PFS), and duration of response (DOR). Patients without DLT and no evidence of disease progression after 48 weeks enrolled in the extension study. Patients had median age of 69 years (range, 52-83) and received median of 4 prior therapies (1-14); 17 of 40 patients (43%) were refractory to their most recent treatment. Median duration of idelalisib treatment was 3.5 months (range, 0.7-30.7), with 6 (15%) continuing extension treatment. Common grade ≥3 adverse events (AEs) included (total%/grade ≥3%) diarrhea (40/18), nausea (33/5), pyrexia (28/0), fatigue (25/3), rash (23/3), decreased appetite (20/15), upper respiratory infection (20/0), pneumonia (13/10), and alanine transaminase or aspartate transaminase elevations (60/20). ORR was 16 of 40 patients (40%), with CR in 2 of 40 patients (5%). Median DOR was 2.7 months, median PFS was 3.7 months, and 1-year PFS was 22%. These data provide proof of concept that targeting PI3Kδ is a viable strategy and worthy of additional study in MCL. This trial was registered at www.clinicaltrials.gov as #NCT00710528.

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.

Final results of a phase I study of idelalisib, a selective inhibitor of PI3Kδ, in patients with relapsed or refractory indolent non-Hodgkin lymphoma (iNHL)

8526

Background: PI3K-delta signaling is critical for activation, proliferation and survival of B cells, plays a role in homing and retention in lymphoid tissues, and is hyperactive in many B-cell malignancies. Idelalisib (GS-1101) is a first-in-class, selective, oral inhibitor of PI3Kδ. Initial response rate of 38% was reported previously in iNHL (Kahl, ICML 2011). Long-term follow-up is now presented. Methods: This phase 1 study evaluated the activity of continuous idelalisib monotherapy in pts with relapsed hematologic malignancies. Doses ranged from 50 to 350 mg QD or BID in 8 cohorts. Response was evaluated based on investigator assessments using standard criteria (Cheson, 2007). Pts who continued to benefit were able to enroll in an ongoing extension study. Results: Study enrolled 64 pts with indolent iNHL. iNHL subtypes included 38 FL, 11 SLL, 9 LPL/WM, and 6 MZL. Pts were 69% male, median age [range] of 64 [32E91] years, 58% with refractory disease and 53% with bulky disease (LN diameter ≥5 cm). The median [range] number of prior therapies was 4 [1E10]. The median [range] duration of treatment was 3.8 [0-41] months, with 19 (30%) pts continuing on treatment extension protocol. ORR across all cohorts were 31/64 (48%), with 1 CR (1.6%). The median duration of response (mDOR) was 18.4 months, and median PFS (mPFS) was 7.6 months. For pts dosed with ≥100 mg BID (N=36); the ORR was 24/36 (67%), the mDOR was 15.4 months, and the mPFS was 16.6 months. The ORR for iNHL subtypes was: FL (45%), SLL (64%), LPL/WM (56%), and MZL (33%). Adverse events included (total%/≥G3%) diarrhea (36/8), fatigue (36/3), rash (27/3), nausea (25/2), pyrexia (20/3), chills (20/0), cough (19/2), pneumonia (17/16), and URI (17/0). Lab abnormalities included (total%/≥G3%) ALT/AST elevations (56/25). 8/64 (12.5%) pts discontinued therapy due to potentially treatment-related adverse events. Conclusions: The oral PI3Kδ inhibitor idelalisib is active in heavily pretreated pts with iNHL, can produce durable responses, and has a favorable safety profile. These data support further clinical development; phase 2 and 3 trials in iNHL are ongoing (NCT01732913, NCT01732926). Clinical trial information: NCT00710528.

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.

Final results of a phase I study of idelalisib, a selective inhibitor of phosphatidylinositol 3-kinase P110δ (PI3Kδ), in patients with relapsed or refractory mantle cell lymphoma (MCL)

8519

Background: PI3K-delta signaling 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. Initial response rate of 42% was previously reported in MCL (Kahl, ICML 2011). Long-term follow-up is now presented. Methods: This phase 1 study evaluated the activity of continuous (48 weeks) idelalisib monotherapy in pts with relapsed or refractory hematologic malignancies. Doses ranged from 50 mg BID to 350 mg BID in 8 cohorts. Response was based on investigator assessments using standard criteria (Cheson et al, 2007). Patients who continued to benefit were able to enroll in an extension study. Results: 40 patients with recurrent MCL enrolled. Patients were 88% male, median age [range] of 69 [52-83] years, 43% with refractory disease. The median [range] number of prior therapies was 4 [1E14]. The median [range] duration of idelalisib treatment was 3.5 [1-26+] months, with 6 (15%) patients continuing on treatment in the extension protocol. Overall response rate (ORR) was 16/40 (40%), with 2/40 CR (5%). The median duration of response (mDOR) was 2.7 months, and median PFS (mPFS) was 3.7 months. The 1-year PFS was 22%. For patients dosed with ≥100 mg BID, ORR was 12/23 (52%), for patients dosed with ≥150 mg BID, ORR was 11/16 (69%) including both CR (12.5%). Most common adverse events included (total%/≥G3%); diarrhea (40/18), nausea (33/5), pyrexia (28/0), fatigue (25/3), rash (25/3), decreased appetite (20/15), URI (20/0), and pneumonia (13/13). Abnormal lab values included (total%/≥G3%) ALT/AST elevations (65/20). 6/40 (15%) patients discontinued therapy due to AEs, potentially treatment related. Conclusions: The oral PI3Kδ inhibitor idelalisib (GSE1101) is active and well tolerated in heavily pre-treated pts with MCL. A proportion of patients have long-term (>1 year) clinical benefit. These data support further clinical evaluation of idelalisib in MCL. Clinical trials with idelalisib in combination with other agents are in progress. Clinical trial information: NCT00710528.