Bortezomib in multiple myeloma

BACKGROUND

Bortezomib is a novel, first-in-class proteasome inhibitor that has improved outcomes in multiple myeloma, with manageable toxicities.

OBJECTIVE

To summarise the chemistry, pharmacokinetics and metabolism of bortezomib, and review its clinical efficacy and toxicity, including use in elderly patients, use in patients with renal impairment and/or a poor prognosis, and effects on bone metabolism.

METHODS

Literature search of bortezomib studies (within 10 years) and recent congress abstracts.

RESULTS/CONCLUSIONS

Bortezomib has improved response rates, overall survival, and time to progression in relapsed or refractory disease, both as a single agent and as part of combination regimens. Promising results have also been reported with bortezomib combinations in frontline induction therapy. Patient subgroups where conventional approaches are inappropriate may also benefit, thereby expanding the therapeutic armamentarium against this debilitating disease.

Clinical updates and nursing considerations for patients with multiple myeloma

Multiple myeloma accounts for approximately 1% of all new cancers and is characterized by abnormal plasma cell proliferation in the bone marrow. As a result, many patients develop bone lesions, hypercalcemia, anemia, and renal impairment. Although no cure exists for multiple myeloma, current treatments, such as oral melphalan and prednisone, can slow disease progression and prolong overall survival. Several new therapeutic options show promise: lenalidomide, thalidomide, liposomal doxorubicin, and bortezomib. Clinical research presented at the 2006 meeting of the American Society of Hematology, the 2007 meeting of the American Society of Clinical Oncology, and the 11th International Myeloma Workshop showed that newer therapeutic combinations were well tolerated and effective in patients with multiple myeloma. Oncology nurses, with their specialized knowledge of treatment administration and monitoring and their expertise in patient education, have an important role in the management of patients with multiple myeloma to help improve overall survival and quality of life. As newer regimens become available, oncology nurses must be aware of factors that optimize outcomes to help patients understand the benefits of treatment, how to manage side effects, and the importance of treatment adherence.

Proteasome inhibitor, bortezomib, for myeloma and lymphoma

Bortezomib, a boronic acid, is a potent and selective proteasome inhibitor. The 20S proteasome is an enzyme complex present in cells, and it degrades many cell-cycle control factors, signal transduction factors, transcription factors, and oncogene and anti-oncogene products, thus controlling cell proliferation, differentiation, and apoptosis. Bortezomib is a novel molecular targeting agent which was designed to exhibit an antitumor effect by selectively inhibiting the 20S proteasome. Multiple myeloma is one of the incurable B-cell malignancies that continues to relapse with current treatment modalities, and the duration to progression becomes shorter in patients who repeatedly receive chemotherapy. There are no available treatment options in which durable efficacy can be expected after relapse; therefore, an effective therapy with a novel mechanism of action has been desired. In this review article, the results of clinical trials of bortezomib for multiple myeloma, including a Japanese phase I/II and pharmacokinetic/pharmacodynamic study, and those for non-Hodgkin lymphoma, especially for mantle cell lymphoma, are summarized. In the Japanese phase I/II study of bortezomib for relapsed multiple myeloma, this agent showed remarkable efficacy, with acceptable toxicities and unique pharmacokinetic/pharmacodynamic profiles, warranting further investigations, including more relevant administration schedules.

Management of multiple myeloma: the changing landscape

Many changes have been incorporated into the approach to multiple myeloma over the last few years, due to improvements in our understanding of the disease biology. New diagnostic and prognostic criteria from the International Myeloma Working Group have clarified the initial clinical approach to this disease. The prognostic impact of chromosomal abnormalities is now recognized, and the detection of specific abnormal cytogenetics is beginning to influence therapeutic decisions. The introduction of the novel agents thalidomide, bortezomib and lenalidomide has expanded treatment options at different points in the disease course; these agents are being evaluated in conjunction with conventional chemotherapy and stem cell transplantation. This report highlights some of the key recent findings in multiple myeloma, and describes areas for future research.

The treatment of relapsed and refractory multiple myeloma

Relapsed and refractory multiple myeloma (MM) constitutes a specific and unmet medical need. Median survival ranges from as little as 6 to 9 months, and responses to treatment are characteristically short. Patients with relapsed/refractory disease are defined as those who, having achieved minor response or better, relapse and then progress while on salvage therapy, or experience progression within 60 days of their last therapy. In the era prior to the development of novel biologically based therapies for MM, relapse from successive treatment regimens resulted in progressively shorter response durations, which typically reflected emerging drug resistance, as well as changes in disease biology within each patient, with tumor cells expressing a more aggressive phenotype, higher proliferative fraction and lower apoptotic rates. Both bortezomid- and lenalidomide-based therapies are expecially active, with bortezomib in particular being shown to provide a platform for combinations able to overcome resistance in this setting. The addition of novel and conventional agents to the treatment backbone of lenalidomide, thalidomide, and bortezomib are areas of active study, with participation in clincial trials a clear priority for such patients. Clinical challenges in the relapsed/refractory population include light chain and IgA isotype, renal failure, extramedullary disease, hyposecretory myeloma, and advanced bone disease.