SUNNYVALE, Calif., June 19, 2013 /PRNewswire/ -- Pharmacyclics, Inc. (the "Company") (Nasdaq: PCYC) today announced that The New England Journal of Medicine ( NEJM) published results of a Phase 2 study evaluating the investigational oral Bruton's tyrosine kinase (BTK) inhibitor ibrutinib in patients with relapsed/refractory mantle cell lymphoma (MCL) online. These data suggested ibrutinib may be effective and generally well-tolerated in patients with relapsed/refractory MCL. Results of a separate study examining the safety and efficacy of ibrutinib monotherapy for the treatment of patients with relapsed/refractory chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL), some of whom had deletion of part of chromosome 17 (del 17p), has also been published online by The NEJM. Pharmacyclics sponsored both studies and is jointly developing ibrutinib with Janssen Research & Development, LLC. "There remains a significant unmet need for patients with MCL," said lead author Michael Wang, M.D., Department of Lymphoma/Myeloma, The University of Texas MD Anderson Cancer Center. "These data are exciting because they demonstrate that the longer MCL patients are treated with ibrutinib the better they respond to the treatment." The study evaluated 111 patients with relapsed/refractory MCL treated with ibrutinib. The majority of patients (86 percent) had intermediate or high-risk MCL and had previously undergone treatment with a median of three prior therapies before enrollment in the study. Patients were enrolled in two cohorts based on whether they had prior exposure to bortezomib. Overall response rate across both cohorts was 68 percent with 47 percent of patients achieving a partial response and 21 percent achieving a complete response where all signs of cancer are gone. The estimated median response duration was 17.5 months. The median progression free survival was 13.9 months and while the median overall survival for this study has not yet been reached it is estimated to be 58 percent at 18 months. The overall response to ibrutinib was independent of prior treatment including bortezomib and lenalidomide or underlying risk/prognosis, bulky disease, gender or age. In an initial subset of patients enrolled in the study who have the longest follow up (n=51), the response to ibrutinib increased with longer duration of treatment, with the complete response rate increasing from 16 percent at a median follow-up of 3.7 months to 37 percent at a median follow-up of 18.2 months.