Ibrutinib in mantle cell lymphoma patients: glass half full? Evidence and opinion.

Mantle cell lymphoma (MCL) is a rare subtype of non-Hodgkin's lymphoma typically marked by an aggressive clinical course and a predilection for relapse. The B-cell receptor (BCR) signaling survival pathway is chronically activated in MCL, contributing to its pathogenesis. Ibrutinib is an inhibitor of Bruton's tyrosine kinase, a vital component of this pathway. This article details the current clinical experience with ibrutinib in the treatment of patients with MCL, including completed and published clinical trials and reviews potential adverse events (AEs) and pitfalls associated with ibrutinib therapy. Although most AEs experienced by patients treated with ibrutinib are mild, some can be severe and treatment limiting and may be attributed to off-target effects. Ibrutinib is a very promising agent for patients with MCL with notable response rates. However, when used as a single agent, around one third of patients relapse in the first 2 years of treatment. Recently reported combination therapies have shown significant activity. Emerging data evaluating potential mechanisms of drug resistance and the poor clinical outcomes after treatment failure are also discussed. Further understanding of resistance and its implications not only in relapsed disease but in the frontline setting are needed. Investigation of strategies to overcome resistance remains an area of high unmet clinical need. Evaluation of the impact of shorter treatment duration, effects on minimal residual disease, and incorporation of novel combinations are also warranted.