Phase 1 clinical trial of bortezomib in adults with recurrent malignant glioma

Bortezomib selectively binds and inhibits the 20S proteasome enzyme's active sites. This study was conducted to determine the side effects and maximum tolerated dose (MTD) of bortezomib in patients with recurrent malignant glioma. Separate dose escalations were conducted in patients taking or not taking enzyme-inducing anti-seizure drugs (+/-EIASD). The starting dose in both groups was 0.9 mg/m(2) intravenously twice weekly for the first three of each 4 week cycle. Imaging assessment of response was carried out and Plasma 20S proteasome activity inhibition and imaging was conducted to monitor efficacy. The 66 patients enrolled had a median age of 51 years, median KPS of 90%, and 77% had glioblastoma multiforme. The MTD in the -EIASD group was 1.70 mg/m(2) based on grade 3 thrombocytopenia, sensory neuropathy and fatigue. In the +EIASD group escalation was terminated at 2.5 mg/m(2) without meeting meet the MTD criteria. However, proteasome inhibition in this group did not change at doses above 1.90 mg/m(2) suggesting that further escalations would be unlikely to increase a biologic effect. Mean proteasome inhibition plateaued in +EIASD patients receiving 2.1 mg/m(2) of bortezomib at 77 ± 12% and in -EIASD patients treated with a dose of 1.7 mg/m(2) at 79 ± 6%. Two partial responses were observed. This study determined that EIASDs effect the MTD of bortezomib and the dose required for maximal inhibition of whole blood 20S proteasome. Some evidence of clinical activity was noted in this phase I study in patients with recurrent high grade gliomas.

Current status of bortezomib in the treatment of multiple myeloma

Bortezomib (formerly PS-341) has been the first proteasome inhibitor to enter clinical trials in cancer patients. Preclinical studies showing that this novel agent directly inhibits the proliferation of myeloma cells, induces their apoptosis, and abrogates paracrine tumor growth through alteration of interactions of myeloma and stromal cells and through nuclear factor kappaB-dependent cytokine secretion prompted the design of large phase II and III studies of bortezomib in patients with advanced relapsed and/or refractory multiple myeloma. Favorable results of these studies led to accelerated approval for use of bortezomib in patients with multiple myeloma who have progressed after at least their second therapy and, more recently, to expanded approval for second-line use in patients in whom one prior therapy has failed. Combination studies of bortezomib with various agents, including dexamethasone, DNA-damaging drugs (such as melphalan, cyclophosphamide, and doxorubicin), thalidomide, and lenalidomide, are currently ongoing in patients with both relapsed/refractory and newly diagnosed disease. Bortezomib may be the "backbone" for the development of more effective treatment strategies to improve patient outcome in multiple myeloma.

Bortezomib, ascorbic acid and melphalan (BAM) therapy for patients with newly diagnosed multiple myeloma: an effective and well-tolerated frontline regimen

BACKGROUND

We conducted a single-arm, multicentre phase 2 study to evaluate bortezomib, ascorbic acid and melphalan (BAM) for patients with newly diagnosed multiple myeloma (MM).

METHODS

Induction consisted of up to eight 28-d cycles of bortezomib 1.0 mg/m(2) on days 1, 4, 8 and 11, plus oral ascorbic acid 1 g and oral melphalan 0.1 mg/kg on days 1-4, followed by maintenance bortezomib 1.3 mg/m(2) every 2 wk until progression.

RESULTS

Among 35 patients enrolled (median age 70 yr), responses occurred in 23/31 evaluable patients (74%) including five (16%) complete, three (10%) very good partial, six (19%) partial and nine (29%) minimal responses. Six patients (19%) had stable disease. Thus, disease control was achieved in 29 (94%) patients. Median times to first and best responses were 2 and 3 months (ranges 1-5 and 1-7), respectively. Median time to progression was 19 months and median overall survival has not been reached (range 2-23+ months). Grade 3 and 4 adverse events occurred in 17 and 5 patients, respectively; the most common were neutropenia, neuropathy and thrombocytopenia.

CONCLUSIONS

BAM is an efficacious, well-tolerated and steroid- and immunomodulatory drug (IMiD)-free frontline treatment regimen for MM patients.

The role of high-dose chemotherapy followed by peripheral blood stem cell transplantation for the treatment of multiple myeloma

The management of multiple myeloma has changed significantly over the past 10 years. The results obtained with conventional chemotherapy were disappointing; however the use of high dose therapy (HDT) and stem cell transplantation has significantly improved survival. Autologous, allogeneic and tandem transplantation, along with different conditioning regimens, have been studied in an attempt to optimise and further improve outcomes. This review summarises the role of stem cell transplantation in multiple myeloma. The advent of novel therapies such as thalidomide, lenalidomide and bortezomib have started to redefine the role of peripheral stem cell transplantation, however, further study is needed to better understand how to most effectively use these agents in multiple myeloma in conjunction with HDT.

New drugs in multiple myeloma

PURPOSE OF REVIEW

Advances in the understanding of multiple myeloma pathogenesis have led to the development of innovative targeted therapies and improved management of this aggressive hematological neoplasia. This review will focus on the clinical trials that have reinforced the use of these new agents. Also, we will briefly take a look at the newer drugs making their way out of the laboratory and into early phase studies.

RECENT FINDINGS

During the past decade new multiple myeloma therapies featuring bortezomib and lenalidomide have come to light, whereas known agents such as thalidomide and arsenic trioxide have been reintroduced as key factors in multiple myeloma management. These new agents and their combinations have shown increased response rates and have added more options for patients with multiple myeloma whose disease has become resistant to conventional therapy. With these drug therapies has come a more targeted approach to treatment enabling not only improved antimyeloma efficacy but also the use of decreased dosing enhancing the safety and tolerability of these regimens. Newer agents including the histone deacetylase, hsp90, mammalian target of rapamycin and Akt inhibitors are showing promise preclinically and are now being assessed in phase I/II trials.

SUMMARY

This new antimultiple myeloma arsenal has shown its worth in both the relapsed/refractory and frontline setting and provides valuable options for patients with this debilitating disease.

Bortezomib-induced peripheral neuropathy in multiple myeloma: a comprehensive review of the literature

Bortezomib has demonstrated significant activity in clinical trials, mainly against recurrent or newly diagnosed multiple myeloma (MM). Peripheral neuropathy is a significant toxicity of bortezomib, requiring dose modification and potential changes in the treatment plan when it occurs. The mechanism underlying bortezomib-induced peripheral neuropathy (BIPN) is unknown. Metabolic changes resulting from the accumulation of bortezomib in the dorsal root ganglia cells, mitochondrial-mediated disregulation of Ca(++) homeostasis, and disregulation of neurotrophins may contribute to the pathogenesis of BIPN. It is increasingly recognized that BIPN may be a proteasome inhibitor class effect, producing primarily a small fiber and painful, axonal, sensory distal neuropathy. Incidence of BIPN is mainly related to various risk factors, including cumulative dose and evidence of preexisting neuropathy. Assessment of BIPN is based primarily on neurologic clinical examination and neurophysiologic methods. To date, apart from the use of dose reduction and schedule change algorithm, there is no effective treatment with neuroprotective agents for BIPN. Analgesics, tricyclic antidepressants, anticonvulsants, and vitamin supplements have been used as symptomatic treatment against bortezomib-associated neuropathic pain with some success. This review looks critically at the pathogenesis, incidence, risk factors, diagnosis, characteristics, and management of BIPN, and highlights areas for future research.

[New therapeutic strategies for multiple myeloma. Efficacy and cost-effectiveness analyses]

The objective of the present article is the review of the most important therapeutic innovations in the treatment of multiple myeloma in terms of efficacy and cost-effectiveness. Besides autologous transplant with peripheral-blood stem-cell, thalidomide establishes as one of the most powerful therapeutic tools in induction and maintenance treatment and together with lenalidomide and bortezomib as therapy for relapsing/refractory multiple myeloma. Considering, the last named situation thalidomide can be an adequate therapeutical option in combination with dexamethasone. Under a strictly pharmacoeconomic point of view, lenalidomide and bortezomib seem to be additional alternatives in patients previously treated with thalidomide.

Management of relapsed and relapsed refractory myeloma

Studies of bortezomib, thalidomide, and lenalidomide have shown promising clinical activity in relapsed/refractory multiple myeloma (MM). Bortezomib alone and in combination with other agents is associated with high response rates, consistently high rates of complete response, and a predictable and manageable profile of adverse events. Thalidomide-based regimens have also shown substantial clinical activity. The accumulating experience from ongoing trials of bortezomib/lenalidomide/dexamethasone combinations in patients who have relapsed/refractory or newly diagnosed MM will provide critical information that will determine the possible role of this combination as the basic backbone for combination regimens for management of advanced MM.

Phase II Pethema Trial of Alternating Bortezomib and Dexamethasone As Induction Regimen Before Autologous Stem-Cell Transplantation in Younger Patients With Multiple Myeloma: Efficacy and Clinical Implications of Tumor Response Kinetics

Purpose

This is the first study in which bortezomib and dexamethasone were administered on an alternating basis as up-front therapy in multiple myeloma (MM). We investigated the efficacy and kinetics of response to each drug and safety.

Patients and Methods

Patients with newly diagnosed MM who were less than 66 years old were treated with bortezomib at 1.3 mg/m2on days 1, 4, 8, and 11 (cycles 1, 3, and 5) and dexamethasone 40 mg orally on days 1 through 4, 9 to 12, and 17 to 20 (cycles 2, 4, and 6), followed by autologous stem-cell transplantation (ASCT). Responses were evaluated by modified European Bone Marrow Transplantation criteria. Random effects models were used to analyze the tumor response kinetics.

Results

Forty patients were enrolled. Partial response (PR) or greater was 65% (12.5% complete response [CR], 10% very good PR [VGPR], and 42.5% PR) plus 17.5% minor response. Time to response was rapid, with 82% serum M-protein reduction achieved within the first two cycles. The M-protein decrease was similar with dexamethasone and with bortezomib (P = .48). Chromosome 13 deletion, t(4;14), and t(14;16) did not have a negative impact on response. Toxicity was low, with no grade 3 to 4 peripheral neuropathy and no grade 2 to 4 thrombocytopenia. The response rate after ASCT was 88%, with 33% CR (negative immunofixation) plus 22% VGPR.

Conclusion

Bortezomib alternating with dexamethasone is a highly effective induction regimen with low toxicity. The kinetic study has shown a high degree of heterogeneity in response and rapid effect from both agents, supporting the use of a short induction regimen before ASCT in MM.

New drugs for myeloma

Although multiple myeloma remains incurable with conventional treatments, management of the disease has recently been transformed with the introduction of three novel agents, bortezomib, thalidomide, and lenalidomide. The proteasome inhibitor bortezomib is approved for the treatment of patients who have received one prior therapy; there is a growing body of clinical evidence showing its effectiveness alone and in combination in the frontline setting, with high response rates and consistently high rates of complete response. Thalidomide plus dexamethasone is approved as frontline treatment of multiple myeloma. Other combination regimens including thalidomide have demonstrated substantial activity in both relapsed and frontline settings. Recently, the thalidomide analogue lenalidomide has been approved, in combination with dexamethasone, for the treatment of patients who have received one prior therapy; this regimen has shown promising results in the frontline setting. These agents represent a new generation of treatments for multiple myeloma that affect both specific intracellular signaling pathways and the tumor microenvironment. Other novel, targeted therapies are also being evaluated in preclinical and clinical studies. Regimens incorporating bortezomib, thalidomide, lenalidomide, and other novel agents, together with commonly used conventional drugs, represent a promising future direction in myeloma treatment. At present, further investigation is required to assess the safety and activity of combinations integrating these other novel agents. However, bortezomib, thalidomide, and lenalidomide are now in widespread clinical use. This review therefore focuses on the extensive clinical data available from studies of these drugs in the treatment of newly diagnosed and advanced multiple myeloma.

Clinical Impact of Bortezomib in Frontline Regimens for Patients with Multiple Myeloma

Standard frontline therapy for multiple myeloma comprises cytoreductive therapy with or without consolidative high-dose therapy plus stem cell transplantation (HDT-SCT). Despite therapeutic advances, the disease remains incurable; most patients relapse following frontline treatment and die within 5 years of diagnosis. New options are required to enhance and prolong response, and improve survival, particularly for elderly patients and those with renal dysfunction. Preclinical studies have demonstrated the ability of bortezomib to enhance the activity of commonly used myeloma agents, an observation validated through clinical studies in both the relapsed and frontline settings. This review focuses on the growing body of clinical evidence showing the effectiveness of bortezomib and bortezomib-based combinations in newly diagnosed patients, characterized by high overall response rates and consistently high rates of complete response. A number of studies incorporating bortezomib as part of induction therapy have demonstrated no adverse impact of bortezomib on stem cell harvest and engraftment in patients proceeding to transplantation. The higher rates of complete response typically associated with bortezomib treatment may potentially improve clinical outcomes in this setting. Final results from ongoing phase III studies of bortezomib-based combinations versus standard regimens will help define the optimal use of bortezomib as a standard component of frontline therapy for multiple myeloma. Disclosure of potential conflicts of interest is found at the end of this article.

Current Standards for First-Line Therapy of Multiple Myeloma

Current standards of care for first-line treatment of multiple myeloma are evolving rapidly because of the introduction of regimens based on novel agents with unique mechanisms of action: the proteasome inhibitor bortezomib and the immunomodulatory drugs thalidomide and lenalidomide. These regimens are becoming increasingly widely used, offering substantially greater benefit to patients in terms of higher response rates and, more importantly, prolonged response durations and survival compared with established standard first-line treatment strategies. A notable aspect of many of these emerging treatment options is the very high rates of complete response (CR) reported, previously only seen with transplantation-based strategies. Achievement of CR is prognostic for improved overall survival; therefore, the higher rates and quality of responses seen with the new regimens might substantially improve patient outcomes versus established standards of care. For example, addition of each of the 3 novel agents to melphalan/prednisone results in higher overall response rates and CR rates, as well as prolonged progression-free and overall survival, compared with melphalan/prednisone alone. Similar substantial improvements in response are seen with addition of the 3 agents to single-agent dexamethasone and the use of bortezomib or thalidomide in VAD (vincristine/doxorubicin/dexamethasone)-like regimens, as induction therapies before stem cell transplantation and in patients not proceeding to transplantation. Ultimately, these novel regimens might obviate the need for stem cell transplantation in a sizeable proportion of patients. The emergence of these new therapeutic options appears likely to significantly alter the first-line treatment paradigm for patients with multiple myeloma.

Emerging drugs in multiple myeloma

The treatment of multiple myeloma has seen significant changes from the time of the initial use of cytotoxic agents such as melphalan, to the introduction of high-dose chemotherapy and stem cell transplantation, and most recently the era of novel targeted agents. These new drugs have rapidly become the mainstay of therapy of this disease and transformed the treatment paradigm, leading to improvements in survival and quality of life. Existing therapeutic options include agents such as thalidomide, bortezomib and lenalidomide, either used alone or in combination with standard agents, including glucocorticoids, and in conjunction with high-dose chemotherapy supported with stem cell transplantation. Several other targeted agents have demonstrated exciting preclinical activity, and are presently being tested in early Phase I and II clinical trials. This review summarizes the role of novel therapeutic agents in multiple myeloma, and the promising effect of multiple new agents in development.