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983 The Bruton’s Tyrosine Kinase (BTK) Inhibitor PCI-32765 Induces Durable Responses in Relapsed or Refractory (R/R) Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL): Follow-up of a Phase Ib/II Study

Program: Oral and Poster Abstracts
Type: Oral
Session: 642. CLL - Therapy, excluding Transplantation: Relapse treatment, novel agents and treatment related complications
Tuesday, December 13, 2011: 7:30 AM
Ballroom 20A (San Diego Convention Center)

Susan O'Brien, MD1, Jan A. Burger, MD, PhD2, Kristie A. Blum, MD3, Richard R. Furman, MD4, Steven E. Coutre, MD5, Jeff Sharman, MD6*, Ian W. Flinn, MD, PhD7, Barbara Grant, MD8*, Nyla A. Heerema, PhD9, Amy J. Johnson, PhD3, Tasheda Navarro10*, Eric Holmgren, PhD10*, Eric Hedrick, MD10 and John C. Byrd, MD11

1Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX
2Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX
3The Ohio State University, Columbus, OH
4Department of Medicine, Division of Hematology-Oncology, Weill Cornell Medical College, New York, NY
5Divisions of Hematology and Oncology and Stanford Cancer Center, Stanford University School of Medicine, Stanford, CA
6US Oncology, Springfield, OR
7Sarah Cannon Research Institute, Nashville, TN
8Medicine, Vermont Cancer Center, University of Vermont, Burlington, VT
9Pathology, The Ohio State University, Columbus, OH
10Pharmacyclics, Inc, Sunnyvale, CA
11Division of Hematology, The Ohio State University, Columbus, OH

Introduction: Btk is a central mediator of B-cell receptor signaling which is essential for normal B-cell development. PCI-32765 is an orally-administered irreversible inhibitor of Btk which induces apoptosis and inhibits cellular migration and adhesion in malignant B-cells. An early analysis of the phase Ib/II study PCYC-1102 showed PCI-32765 to be highly active and tolerable in patients with CLL (Byrd, ASCO 2011). Here we report longer-term follow-up of this multicenter phase Ib/II trial.

Methods and Patients: Two cohorts of CLL patients (previously untreated ≥65 years old and relapsed/refractory [R/R] disease following at least 2 prior therapies, including fludarabine) were treated with oral PCI-32765 administered daily for 28-day cycles until progression of disease. Doses of 420mg (previously untreated and R/R) and 840mg daily (R/R) were examined. The patients with R/R disease are the subject of this report.  

Results:  Sixty-one R/R CLL/SLL patients were enrolled (420mg cohort n=27, 840mg cohort n=34). The median follow-up time for the 420mg cohort is 10.2 months and for the 840mg cohort is 6.5 months. The median number of prior treatment regimens for the 420mg cohort was 3 (2-10) and for the 840mg cohort was 5 (1-12). Seventy-two percent of patients had at least one poor-risk molecular feature: del(17p) 31%, del(11q) 33%, IgVH un-mutated 57%. Treatment has been well tolerated. Two patients have discontinued for adverse events (AE); 6 patients have required reduction of PCI-32765 dose (420mg cohort 2/27, 840mg cohort 4/34). Grade 1 or 2 diarrhea, fatigue, nausea, and ecchymosis have been the most frequently reported AEs. Serious AEs (SAEs) have occurred in 38% of patients; SAEs considered potentially related to PCI-32765 have occurred in 10% of patients. Grade ≥3 AEs considered potentially related to PCI-32765 occurred in 21% of patients. A characteristic pattern of response, with a transient phase of lymphocytosis typically peaking within the first 2 months of Rx, followed by resolution over time, has been observed in the majority of patients.  Objective response (ORR; PR + CR) by IWCLL criteria in the 420mg cohort cohort, previously reported as 48% with 6.2 months median follow-up (Byrd, et al ASCO 2011), is now 70% with 10.2 months median follow-up. ORR in the 840mg cohort is 44% at 6.5 months median follow-up. An additional 19%, and 35% of patients in these cohorts, respectively, have a nodal PR (>50% reduction in aggregate lymph node size) with residual lymphocytosis. ORR appears to be independent of molecular risk features. Eighty-two percent of patients (50/61; 420mg cohort 22/27, 840mg cohort 28/34) remain on PCI-32765. Only 8% (5/61) of patients have had progressive disease (PD); 6-month PFS is 92% in the 420mg cohort and 90% in the 840mg cohort. Treatment cessation not related to PD or AE includes: death (n=2) or investigator discretion (n=3).

Conclusions:  The potent Btk inhibitor PCI-32765 is well tolerated and is associated with high rates of 6-month PFS in R/R CLL/ SLL. Phase III trials of PCI-32765 in CLL/ SLL are planned.

Disclosures: O'Brien: Pharmacyclics, Inc: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Burger: Pharmacyclics, Inc: Research Funding. Blum: Pharmacyclics: Research Funding. Furman: Pharmacyclics, Inc: Research Funding. Coutre: Pharmacyclics, Inc: Research Funding. Sharman: Pharmacyclics, Inc: Research Funding. Flinn: Pharmacyclics, Inc: Research Funding. Grant: Pharmacyclics, Inc: Research Funding. Heerema: Pharmacyclics, Inc: Research Funding. Johnson: Pharmacyclics, Inc: Research Funding. Navarro: Pharmacyclics, Inc: Employment, Equity Ownership. Holmgren: Pharmacyclics, Inc: Consultancy. Hedrick: Pharmacyclics: Employment, Equity Ownership. Byrd: Pharmacyclics, Inc: Research Funding.

*signifies non-member of ASH