Abstract

Abstract 189

Background:

BTK is an essential mediator of B-cell receptor signaling in normal and transformed B-cells. Ibrutinib (PCI-32765), an oral inhibitor to BTK, promotes apoptosis and inhibits proliferation, migration and adhesion in CLL cells. Chemoimmunotherapy (CIT) treatment approaches such as fludarabine, cyclophosphamide and rituximab have markedly improved outcomes of younger, fit patients (pts) as initial or second-line therapy. While effective, fludarabine-based therapy is less well tolerated in the elderly and carries significant risk of cellular immune suppression and myelosupression that limit protracted use. Additionally, virtually all pts eventually relapse after fludarabine-based CIT and effective salvage regimens that induce durable remissions are lacking. Herein, we present mature data from a large (n=116 pts) multi-cohort Phase Ib/II trial of ibrutinib in treatment-naive (TN) or relapsed/refractory (RR) CLL/SLL. Pts experienced a high frequency of disease control extending beyond 22 months in both TN and RR CLL/SLL including those with high risk genomic features.

Methods:

Pts who were TN (all age >=65 years), RR (>= 2 prior therapies including a purine analog), or high-risk (HR) (relapse within 2 years following combination CIT or del 17p) were enrolled into 5 cohorts evaluating oral ibrutinib at fixed doses of 420mg or 840mg daily until disease progression (PD).

CohortPopulationDose mg/dayGroup Size
relapsed/refractory 420 27 
treatment-naïve; aged ≥ 65 years 420 26 
relapsed/refractory 840 34 
High Risk - relapsed or refractory 420 24 
treatment-naïve; aged ≥ 65 years 840 5a 
CohortPopulationDose mg/dayGroup Size
relapsed/refractory 420 27 
treatment-naïve; aged ≥ 65 years 420 26 
relapsed/refractory 840 34 
High Risk - relapsed or refractory 420 24 
treatment-naïve; aged ≥ 65 years 840 5a 
a

Cohort closed prior to full accrual after comparable activity and safety between doses was shown in R/R pts.

Primary objective was to determine the safety of the two dosing regimens. Secondary objectives were to assess efficacy, PK/PD and long-term safety. Overall Response rate (ORR) inclusive of complete and partial responses (CR and PR respectively) was assessed per IWCLL guidelines. In addition, those pts who achieved a PR with the exception of lymphocytosis were categorized as PR with lymphocytosis.

Results:
Study PopulationTreatment naive, age >= 65yrs (cohort 2 & 5)Relapsed or Refractory (cohort 1 & 3)High risk (cohort 4)
(N=116)    
Number of pts 31 61 24 
Median f/u, months (range) 16.6 (1.4, 23.2) 17.3 (0.3, 22.4) 10.3 (1.1, 11.5) 
Age (range) 71 (65, 84) 64 (40, 81) 68 (37, 82) 
Median # prior Tx (range) 4 (1,12) 4 (1,11) 
Hgb <11 g/dl OR Plt <100,000 μL 61% 57% 63% 
b2M >3 mg/L 8/31 (26%) 30/57 (53%) 9/23 (39%) 
IgVH unmutated (UM) 17/31 (55%) 50/58 (86%) 19/23 (83%) 
del 17p 2/30 (7%) 21/57 (37%) 7/23 (30%) 
del 11q 1/30 (3%) 23/57 (40%) 8/23 (35%) 
Best Response by Cohort:    
IWCLL ORR (CR + PR) 71% 67% 50% 
    CR 10% 3% 
    PR 61% 64% 50% 
PR with lymphocytosis 10% 20% 29% 
SD 13% 5% 8% 
PD 2% 4% 
Not evaluable 6% 7% 8% 
Study PopulationTreatment naive, age >= 65yrs (cohort 2 & 5)Relapsed or Refractory (cohort 1 & 3)High risk (cohort 4)
(N=116)    
Number of pts 31 61 24 
Median f/u, months (range) 16.6 (1.4, 23.2) 17.3 (0.3, 22.4) 10.3 (1.1, 11.5) 
Age (range) 71 (65, 84) 64 (40, 81) 68 (37, 82) 
Median # prior Tx (range) 4 (1,12) 4 (1,11) 
Hgb <11 g/dl OR Plt <100,000 μL 61% 57% 63% 
b2M >3 mg/L 8/31 (26%) 30/57 (53%) 9/23 (39%) 
IgVH unmutated (UM) 17/31 (55%) 50/58 (86%) 19/23 (83%) 
del 17p 2/30 (7%) 21/57 (37%) 7/23 (30%) 
del 11q 1/30 (3%) 23/57 (40%) 8/23 (35%) 
Best Response by Cohort:    
IWCLL ORR (CR + PR) 71% 67% 50% 
    CR 10% 3% 
    PR 61% 64% 50% 
PR with lymphocytosis 10% 20% 29% 
SD 13% 5% 8% 
PD 2% 4% 
Not evaluable 6% 7% 8% 

The majority of AEs have been Gr ≤ 2 in severity, most commonly diarrhea (54%), fatigue (29%), upper respiratory tract infection (29%), rash (28%), nausea (26%) and arthralgias (25%). Hematologic toxicity ≥ Gr 3 was relatively infrequent. There was no evidence of cumulative toxicity or long-term safety concerns with a median follow-up of 16 months for the 116 treated pts. Treatment discontinuation for AE occurred in 7/116 pts across cohorts. Serial evaluation of serum immunoglobulins revealed a significant increase in IgA at 3, 6, and 12 months (P < 0.005 at each time point) with no decline in IgG or IgM.

Responses were observed independent of poor-risk factors including advanced stage disease, prior lines of therapy, b2M, or cytogenetics (e.g. ORR in del 17p R/R (cohorts 1 & 3) 67%). Interestingly, 56/69 relapsed pts with UM IgVH developed treatment related lymphocytosis compared to 11/11 pts with mutated (M) IgVH that resolved more rapidly (median time to normalization 6.2 vs 14.8 months) and normalized more frequently (86% vs 55% P<0.04) compared to those with M IgVH.

Estimated 22 month PFS for the 85 RR and HR pts is 76% and for the 31 TN pts is 96%. Estimated 22 month OS for 85 R/R and HR pts is 85% and for the 31 TN pts is 96%. Median PFS and OS have not been met for any of the cohorts including pts with high-risk factors (see Figure- PFS by 17p del status).

Conclusions:

Ibrutinib monotherapy is highly active, well tolerated, and induces durable remissions in pts with RR CLL including those with high-risk disease and in older TN pts warranting phase III evaluation in these populations.

Disclosures:

Byrd:Pharmacyclics: Research Funding. Off Label Use: Ibrutinib is not approved for the treatment of NHL. Burger:Pharmacyclics: Consultancy, Research Funding. Sharman:Celgene: Consultancy; Pharmacyclics: Honoraria; Calistoga: Honoraria; Portola pharmaceuticals: Consultancy. Tran:pharmacyclics: Employment, Equity Ownership. Clow:Pharmacyclics: Employment, Equity Ownership. Kunkel:Onyx Pharmaceuticals: Consultancy. James:Pharmacyclics: Employment, Equity Ownership. O'Brien:Pharmacyclics: Research Funding.

Author notes

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Asterisk with author names denotes non-ASH members.