Bruton tyrosine kinase inhibitor ibrutinib (PCI-32765)

Management perspective for mantle cell lymphoma

SUMMARY Mantle cell lymphoma (MCL) is genetically characterized by the t(11;14) (q13;q32) translocation resulting in the overexpression of cyclin D1. It generally has an aggressive clinical course with a poor prognosis. However, there is now a recognized subgroup with clinically indolent MCL. Management of MCL can be challenging. Early recognition of young and fit patients for potential intensive therapy and autologous stem cell transplant is important. Combination of rituximab with high-dose cytarabine should be used in upfront therapy for appropriate patients. In elderly and/or less fit patients, chemoimmunotherapy may be considered. Novel agents offer promising potential in the management of MCL and are likely to change the way it is treated.

Tyrosine kinases, drugs, and Shigella flexneri dissemination

Shigella flexneri is an enteropathogenic bacterium responsible for approximately 100 million cases of severe dysentery each year. S. flexneri colonization of the human colonic epithelium is supported by direct spread from cell to cell, which relies on actin-based motility. We have recently uncovered that, in intestinal epithelial cells, S. flexneri actin-based motility is regulated by the Bruton's tyrosine kinase (Btk). Consequently, treatment with Ibrutinib, a specific Btk inhibitor currently used in the treatment of B-cell malignancies, effectively impaired S. flexneri spread from cell to cell. Thus, therapeutic intervention capitalizing on drugs interfering with host factors supporting the infection process may represent an effective alternative to treatments with antimicrobial compounds.

Ibrutinib and indolent B-cell lymphomas

Most patients with indolent B-cell lymphomas fail to achieve complete remission with current treatment approaches and invariably relapse. During the past decade, innovative immunochemotherapy strategies have substantially improved disease control rates but not survival, thus providing the rationale for development of novel agents targeting dysregulated pathways that are operable in these hematological malignancies. Ibrutinib, a novel first-in-human Bruton's tyrosine kinase (BTK) inhibitor, has progressed into phase III trials after early-phase clinical studies demonstrated effective target inhibition, increased tumor response rates, and significant improvement in survival, particularly in patients with indolent B-cell lymphomas. Recently, the compound was designated a "breakthrough therapy" by the United States Food and Drug Administration for the treatment of patients with relapsed or refractory mantle cell lymphoma and Waldenström macroglobulinemia. This review summarizes recent achievements of ibrutinib, with a focus on its emerging role in the treatment of patients with indolent B-cell lymphoid malignancies.

Bruton tyrosine kinase inhibitors: a promising novel targeted treatment for B cell lymphomas

Constitutive or aberrant signalling of the B cell receptor signalling cascade has been implicated in the propagation and maintenance of a variety of B cell malignancies. Small molecule inhibitors of Bruton tyrosine kinase (BTK), a protein early in this cascade and specifically expressed in B cells, have emerged as a new class of targeted agents. There are several BTK inhibitors, including ONO-WG-307, LFM-A13, dasatinib, CC-292, and PCI-32765 (ibrutinib), in preclinical and/or clinical development of which ibrutinib is currently in phase III trials. Recent clinical data suggest significant activity of ibrutinib as a first in class oral inhibitor of BTK. This review provides an overview of ongoing clinical studies of BTK inhibitors.

Management of mantle cell lymphoma in the elderly patient

Mantle cell lymphoma is a relatively rare B-cell lymphoma with a specific genetic lesion and a typical immunophenotypic profile. The median age is 65 years. There is no curative treatment, except allogeneic stem cell transplantation for a selected group of patients. For the majority of patients, especially the elderly, the aim of therapy should therefore be a long progression-free survival. Age and comorbidity may hamper the use of the most active treatment regimen, such as high dose cytarabine and autologous stem cell transplantation. Therefore, it is a challenge to select the most appropriate therapy for an elderly patient. Studies specifically designed for elderly patients are rare. A recently performed large randomized study for elderly patients, however, has shown that R-CHOP (rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy followed by maintenance rituximab can result in a long progression-free survival. For patients too frail for R-CHOP chemotherapy, a treatment should be offered that benefits the patient in reducing the symptoms of the disease without causing too many side effects. Progression or relapse will occur in all patients sooner or later. Second-line treatment should again be carefully selected. Several options are mentioned. New drugs are being developed, and new combinations are investigated. Further improvement in the outcome of patients with mantle cell lymphoma is expected. Participation in well-designed clinical trials, also by elderly patients, is important to find the real benefit that can be achieved, and to get information on the tolerability of these treatments in this age group.

Ibrutinib and novel BTK inhibitors in clinical development

Small molecule inhibitors targeting dysregulated pathways (RAS/RAF/MEK, PI3K/AKT/mTOR, JAK/STAT) have significantly improved clinical outcomes in cancer patients. Recently Bruton's tyrosine kinase (BTK), a crucial terminal kinase enzyme in the B-cell antigen receptor (BCR) signaling pathway, has emerged as an attractive target for therapeutic intervention in human malignancies and autoimmune disorders. Ibrutinib, a novel first-in-human BTK-inhibitor, has demonstrated clinical effectiveness and tolerability in early clinical trials and has progressed into phase III trials. However, additional research is necessary to identify the optimal dosing schedule, as well as patients most likely to benefit from BTK inhibition. This review summarizes preclinical and clinical development of ibrutinib and other novel BTK inhibitors (GDC-0834, CGI-560, CGI-1746, HM-71224, CC-292, and ONO-4059, CNX-774, LFM-A13) in the treatment of B-cell malignancies and autoimmune disorders.