SUNNYVALE, Calif., June 19, 2013 /PRNewswire/ -- Pharmacyclics, Inc. (the "Company") (Nasdaq: PCYC) today announced that The New England Journal of Medicine ( NEJM) published results online of a Phase 1b/2 study evaluating the investigational oral Bruton's tyrosine kinase (BTK) inhibitor ibrutinib in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). Ibrutinib was shown to be safe and effective in patients with relapsed/refractory CLL or SLL, even in patients who were at high-risk due to factors such as deletion of part of chromosome 17 (del 17p). Results of a separate study examining the safety and efficacy of ibrutinib monotherapy for the treatment of relapsed/refractory mantle cell lymphoma (MCL) has also been published online in NEJM today. Pharmacyclics sponsored both studies and is jointly developing ibrutinib with Janssen Research & Development, LLC. The open-label study reported on 85 patients with relapsed/refractory CLL or SLL. The majority of patients had advanced disease and had previously undergone treatment with several rounds of therapies before enrollment in the study. Approximately one-third of patients enrolled in the study presented with a malignancy carrying del 17p. Patients with del17p typically respond poorly to chemoimmunotherapy, which is the current standard treatment for CLL. "Patients with CLL and SLL have a great need for new, well tolerated and effective therapies," said lead author John C. Byrd, M.D., Director, Division of Hematology, D Warren Brown Professor of Leukemia Research, The Ohio State University Comprehensive Cancer Center. "These data are particularly exciting, as they demonstrate benefit for high risk CLL and SLL patients, with efficacy consistent across doses and continuing durable remissions lasting in excess of two years in the great majority of patients treated." Study participants were enrolled selected to receive either ibrutinib 420 mg (n=51) or 840 mg (n=34) as a once-daily, oral monotherapy. Both doses were associated with overall response rates of 71 percent. Del17p patients had an overall response rate of 68 percent. Two patients in the 420 mg dose arm had complete responses and 34 patients had partial responses. Across all relapsed or refractory patients, including the high risk patients, the estimated progression-free survival at 26 months was 75 percent. An additional 20 percent of patients treated with the 420 mg dose and 15 percent of patients taking the 840 mg dose achieved a partial response accompanied by lymphocytosis, an elevated blood lymphocyte count.