Most adverse events (AEs) were Grade 1 or 2 in severity, with the most common attributed to ibrutinib being diarrhea, fatigue, nausea and rash. Adverse hematologic events were relatively infrequent. In patients with cytopenia (low blood cell counts) at the beginning of the study, sustained improvements of platelet counts (78 percent) and hemoglobin (82 percent) were seen after treatment. There was no evidence of cumulative toxicity or long-term safety concerns.
Oral presentation 187, The BTK inhibitor ibrutinib (PCI-32765) in combination with rituximab is well tolerated and displays profound activity in high-risk chronic lymphocytic leukemia (CLL) patients
Jan A. Burger
, M.D., Ph.D., MD Anderson Cancer Center,
This presentation was based on findings from a Phase 2, single-center trial with 40 patients with HR CLL treated with 420 mg/day ibrutinib in combination with rituximab, a current standard CLL therapy. Patients with HR disease were previously treated and had one of the following characteristics: deletion of a part of chromosome 17 (del17p), which is associated with poorer treatment outcomes; a gene mutation called TP53; del11q, another partial chromosome deletion associated with poorer outcomes; or a short remission duration (less than three years) after first-line chemo-immunotherapy.
The results after a follow-up of three to six months are:
- The ORR was 83 percent
- 38 of 40 patients continue on therapy without disease progression
- 95 percent of all patients and 90 percent of patients with del17p had not progressed
- There was a large and rapid reduction in lymph node and spleen sizes, with 84 percent of patients (26/31) experiencing more than a 50 percent decrease in lymph node size
- Treatment was well tolerated overall, with Grade 3 or Grade 4 toxicities infrequent and transient in nature, including febrile neutropenia (fever with low white blood cell count), anemia, mucositis and pneumonia, in this clinical study
"We believe the updated findings from these two trials further affirm the possibilities of ibrutinib," said
, CEO and Chairman of the Board of Directors of Pharmacyclics. "We look forward to continuing our clinical development program for this therapy, and hope it can help us in achieving Pharmacyclics' mission of improving the quality and duration of life for patients with oncologic diseases."
Ibrutinib was designed to specifically target and selectively inhibit an enzyme called Bruton's tyrosine kinase (BTK). BTK is a key mediator of at least three critical B-cell pro-survival mechanisms occurring in parallel – regulating B-cell apoptosis, cell adhesion, and lymphocyte migration and homing. Data are consistent with a mechanistic model whereby ibrutinib blocks BCR signaling, which drives cells into apoptosis and/or disrupts cell migration and adherence to tumor-protective microenvironments.
The effectiveness of ibrutinib alone or in combination with other treatments is being studied in several B-cell malignancies, including CLL/SLL, relapsed/refractory mantle cell lymphoma, diffuse large B-cell lymphoma, follicular lymphoma and multiple myeloma. A comprehensive late stage Phase 2 and 3 program is under way.