A Phase 3, Randomized, Double-Blind, Placebo-Controlled Study Evaluating the Efficacy and Safety of Idelalisib and Rituximab for Previously Treated Patients with Chronic Lymphocytic Leukemia (CLL)

Idelalisib (IDELA) is a first-in-class, selective, oral inhibitor of PI3Kδ that reduces proliferation, enhances apoptosis, and inhibits homing and retention of malignant B cells in lymphoid tissues. Phase 1 trials demonstrated that IDELA is highly active as a single agent or in combination with rituximab (R) in heavily pretreated patients (pts) with CLL. Pts in these trials experienced reductions in disease-associated chemokines, improvement of organomegaly and cytopenias, profound reductions in lymphadenopathy, and durable clinical benefit with an acceptable safety profile (Brown 2013; Barrientos 2013). Patients with early progression and significant co-morbidities have limited treatment options; single-agent rituximab is an option in these pts (NCCN 2013; Zelenetz 2013).

This Phase 3 study evaluated the efficacy and safety of IDELA + R vs placebo + R in pts with previously treated CLL. Eligibility criteria included the need for treatment per IWCLL guidelines, measurable lymphadenopathy, and CLL progression <24 mos since the completion of last therapy. Pts were considered unfit to receive cytotoxic therapy because of comorbidities (defined as a Cumulative Illness Rating Score [CIRS] > 6), renal dysfunction, or cytopenias due to poor marrow reserve. All pts received R at 375 mg/m² [1st dose] and then 500 mg/m²q2 wks x 4, followed by q4 wks x 3 [8 doses total]) and were randomized to Arm A (n=110; IDELA 150 mg BID continuously) or Arm B (n=110; placebo BID continuously). Primary endpoint was progression-free survival (PFS). Response and progression in both arms were assessed by an independent review committee using standard criteria (Hallek 2008; Cheson 2012). Results were reviewed by an external Data Monitoring Committee (DMC).

Results are from a pre-specified interim analysis after ∼50% of the total number of 119 planned events of CLL progression or death from any cause. Data cutoff was 30 Aug 2013. Pt characteristics (n=220) included a median age of 71 yrs (78% ≥ 65 yrs); CIRS > 6 in 85%; median creatinine clearance of 63.6 mL/min; and presence of anemia (73%), thrombocytopenia (61%), neutropenia (34%). Median time since diagnosis was 8.5 yrs, median number of prior therapies was 3 (range: 1-12), 44% had del(17p)/TP53 mutation, and 84% had unmutated IGHV. PFS in the IDELA + R arm was superior to placebo +R (HR [95% CI] = 0.15 [0.08, 0.28]; p = 3.0 x 10¹¹). Median PFS of pts treated with IDELA + R was not reached and for placebo + R was 5.5 mos. At 24 wks, the PFS rate for IDELA +R was 93% compared to 46% for placebo + R. PFS strongly favored IDELA + R in all subgroups, including those with del(17p)/TP53 or unmutated IGHV. Pts treated with IDELA + R and with ≥1 post-baseline assessment also had a superior overall response rate (ORR) relative to those in the control arm (81% vs. 13%; odds ratio 29.9; p = 3.0 x 10¹⁹) and a higher lymph node response (LNR) rate (93% vs. 4%; odds ratio 264.5; p = 1.3 x 10^-30). Relative to the control group, pts treated with IDELA +R also had a significant improvement in overall survival (OS): HR (95% CI) = 0.28 (0.09, 0.86), p = 0.018.

Adverse events (AEs) occurring in ≥20% of pts (any Gr/Gr ≥3) by arm were: pyrexia (IDELA + R 29%/3%; placebo + R 16%/1%), fatigue (IDELA + R 24%/3%; placebo + R 27%/2%), nausea (IDELA + R 24%/0%; placebo + R 22%/0%), chills (IDELA + R 22%/2%; placebo + R 16%/0%), infusion-related reactions (IDELA + R 16%/0%; placebo + R 28%/4%), and cough (IDELA + R 15%/0%; placebo + R 25%/2%). Other selected AEs (any Gr/Gr ≥3) included diarrhea (IDELA + R 19%/4%; placebo + R 14%/0%) and rash (IDELA + R 10%/2%; placebo + R 6%/0%). Select lab abnormalities (any Gr/Gr ≥3) included ALT elevation (IDELA + R 31%/6%; placebo + R 9%/1%), anemia (IDELA + R 26%/6%; placebo + R 30%/14%), neutropenia (IDELA + R 55%/34%; placebo + R 49%/22%), and thrombocytopenia (IDELA + R 17%/10%; placebo + R 26%/16%). The most common SAEs were pneumonia (6.4%), pyrexia (6.4%), and febrile neutropenia (4.5%) in IDELA + R, and pneumonia (8.4%), febrile neutropenia (5.6%), and dyspnea (3.7%) in placebo + R. AEs led to study drug discontinuation in 9 pts (8.2%) in IDELA + R and 11 pts (10.3%) in placebo + R.

Based on a review of efficacy and safety, the DMC recommended stopping the study early.

IDELA + R demonstrated statistically significant improvement with acceptable safety over placebo + R in PFS, ORR, LNR and OS in heavily pretreated pts with relapsed CLL, including those with adverse genetic features.

Furman:Gilead Sciences: Research Funding. Sharman:Gilead Sciences: Consultancy, Research Funding. Coutre:Gilead Sciences: Research Funding. Cheson:Gilead Sciences: Research Funding. Pagel:Gilead Sciences: Research Funding. Hillmen:Gilead Sciences: Research Funding. Barrientos:Gilead Sciences: Research Funding. Zelenetz:Gilead Sciences: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Kipps:Gilead Sciences: Research Funding. Flinn:Gilead Sciences: Research Funding. Ghia:Gilead Sciences: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Eradat:Gilead Sciences: Research Funding. Ervin:Gilead Sciences: Research Funding. Lamanna:Gilead Sciences: Research Funding. Hallek:Gilead Sciences: Research Funding. Coiffier:Gilead Sciences: Research Funding. Pettitt:Gilead Sciences: Research Funding. Ma:Gilead Sciences: Research Funding. Stilgenbauer:Gilead Sciences: Honoraria, Research Funding. Aiello:Gilead Sciences: Employment. Johnson:Gilead Sciences: Employment, Equity Ownership. Miller:Gilead Sciences: Employment, Equity Ownership. Li:Gilead Sciences: Employment. Jahn:Gilead Sciences: Employment. Dansey:Gilead Sciences: Employment, Equity Ownership. O'Brien:Gilead Sciences: Research Funding.