Brentuximab vedotin: a CD30-directed antibody-cytotoxic drug conjugate

Hodgkin lymphoma (HL) and systemic anaplastic large cell lymphoma (sALCL), which is a subtype of non-Hodgkin lymphoma, are relatively uncommon lymphoproliferative types of cancer. These malignancies are highly curable with initial treatment. Nonetheless, some patients are refractory to or relapse after first- and second-line therapies, and outcomes for these patients are less promising. Brentuximab vedotin is a CD30-directed antibody-cytotoxic drug conjugate that has demonstrated efficacy in response rates (objective response rates and complete response) when given to patients with refractory or relapsed HL and sALCL. Although not compared directly in clinical trials, the response rates with brentuximab vedotin are higher than those of several current treatments for refractory or relapsed HL and sALCL. Adverse effects associated with brentuximab vedotin are considered manageable. Nonetheless, several serious adverse effects (e.g., neutropenia, peripheral sensory neuropathy, tumor lysis syndrome, Stevens-Johnson syndrome, and progressive multifocal leukoencephalopathy, resulting in death) have been reported with its use. Despite a lack of survival and patient reported outcome data, the United States Food and Drug Administration (FDA) granted accelerated approval to brentuximab vedotin for the treatment of HL after failure of autologous stem cell transplantation or at least two combination chemotherapy regimens, and for sALCL after failure of at least one combination chemotherapy regimen. With this approval, brentuximab vedotin is the first FDA-approved agent for the treatment of HL in over three decades and the first agent specifically indicated to treat sALCL. Results of ongoing prospective trials should determine if brentuximab vedotin has a survival benefit when compared directly with standard treatment and if brentuximab vedotin is safe and efficacious when given earlier in the disease process, or when used with other chemotherapy for the treatment of HL and sALCL or other CD30-positive malignancies.

A phase 2 study of vorinostat for treatment of relapsed or refractory Hodgkin lymphoma: Southwest Oncology Group Study S0517

We performed a phase II study of oral vorinostat (200 mg twice daily, days 1-14 of a 21-day cycle), a histone and protein deacetylase inhibitor, to examine efficacy and tolerability in patients with relapsed/refractory Hodgkin lymphoma (HL) with ≤ 5 prior therapies. The primary endpoint was the objective response rate (ORR), with secondary endpoints of progression-free survival (PFS), overall survival (OS), safety and tolerability. A two-stage design was used for patient accrual. Twenty-five eligible patients were accrued in the first stage. Median time on treatment was 3.8 months. The ORR was 4% (one partial response). Median PFS was 4.8 months. The drug was well tolerated. The second stage of accrual was not opened due to few objective responses. Oral vorinostat has limited single-agent activity in relapsed/refractory HL. There was one partial response, while seven other patients had stable disease for > 1 year, including two with stable disease for nearly 3 years, suggesting that further studies in combination with other active agents in this setting may be warranted.

Targeting histone deacetyalses in the treatment of B- and T-cell malignancies

HDAC inhibitors (HDACI) are now emerging as one of the most promising new classes of drugs for the treatment of select forms of non-Hodgkin’s lymphoma (NHL). They are particularly active in T-cell lymphomas, possibly hodgkin’s lymphoma and indolent B cell lymphomas. Presently, two of these agents, vorinostat and romidepsin, have been approved in the US for the treatment of relapsed and refractory cutaneous T cell lymphomas (CTCL). Initially, these agents were developed with the idea that they affected transcriptional activation and thus gene expression, by modulating chromatin condensation and decondensation. It is now clear that their effects go beyond chromatin and by affecting the acetylation status of histones and other intra-cellular proteins, they modify gene expression and cellular function via multiple pathways. Gene expression profiles and functional genetic analysis has led to further understanding of the various molecular pathways that are affected by these agents including cell cycle regulation, pathways of cellular proliferation, apoptosis and angiogenesis all important in lymphomagenesis. There is also increasing data to support the effects of these agents on T cell receptor and immune function which may explain the high level of activity of these agents in T cell lymphomas and hodgkin’s lymphoma. There is ample evidence of epigenetic dysregulation in lymphomas which may underlie the mechanisms of action of these agents but how these agents work is still not clear. Current HDAC inhibitors can be divided into at least four classes based on their chemical structure. At present several of these HDAC inhibitors are in clinical trials both as single agents and in combination with chemotherapy or other biological agents. They are easy to administer and are generally well tolerated with minimal side effects. Different dosing levels and schedules and the use of isospecific HDAC inhibitors are some of the strategies that are being employed to increase the therapeutic effect of these agents in the treatment of lymphomas. There may also be class differences that translate into specific activity against different lymphoma. HDAC inhibitors will likely be incorporated into combinations of targeted therapies both in the upfront and relapsed setting for lymphomas.