Current status of targeted therapies for mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a type of non-Hodgkin's lymphoma (NHL) with treatment outcomes that have historically been poorer than those observed with other NHL subtypes. Patients typically present with advanced-stage disease and frequent extranodal involvement; the median age at diagnosis is >60 years. Recent improvements in progression-free and overall survival have been observed with more dose-intensive strategies, although at least half of patients diagnosed with MCL are not eligible for such treatment approaches based on age and co-morbidities. In addition, therapy options for relapsed MCL are limited. Only bortezomib is approved for treatment of relapsed MCL in the US. Development of targeted therapy approaches to minimize toxicities while preserving anti-neoplastic properties is of particular importance in MCL. Multiple ongoing studies are attempting to build on the known efficacy of bortezomib by evaluating combination regimens with other targeted agents or cytotoxic chemotherapy. The mammalian target of rapamycin (mTOR) inhibitor temsirolimus has known activity in MCL, making this an attractive class of agents for further investigation in combination regimens. Rituximab and other monoclonal antibodies are being evaluated for novel roles in MCL treatment, including as maintenance therapy. Other classes of drugs being investigated in MCL are immunomodulatory agents, inhibitors of the phosphoinositide 3-kinase/Akt and B-cell receptor signalling pathways, and inhibitors of bcl-2 and histone deacetylase. Although many of the agents appear to have modest single-agent activity, the favourable toxicity profile of many agents will make them best suited for incorporation into combination regimens.