Randomized phase III study of pegylated liposomal doxorubicin plus bortezomib compared with bortezomib alone in relapsed or refractory multiple myeloma: combination therapy improves time to progression

DSMM XI study: dose definition for intravenous cyclophosphamide in combination with bortezomib/dexamethasone for remission induction in patients with newly diagnosed myeloma

A clinical trial was initiated to evaluate the recommended dose of cyclophosphamide in combination with bortezomib and dexamethasone as induction treatment before stem cell transplantation for younger patients with newly diagnosed multiple myeloma (MM). Thirty patients were treated with three 21-day cycles of bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11 plus dexamethasone 40 mg on the day of bortezomib injection and the day after plus cyclophosphamide at 900, 1,200, or 1,500 mg/m(2) on day 1. The maximum tolerated dose of cyclophosphamide was defined as 900 mg/m(2). At this dose level, 92% of patients achieved at least a partial response. The overall response rate [complete response (CR) plus partial response (PR)] across all dose levels was 77%, with a 10% CR rate. No patient experienced progressive disease. The most frequent adverse events were hematological and gastrointestinal toxicities as well as neuropathy. The results suggest that bortezomib in combination with cyclophosphamide at 900 mg/m(2) and dexamethasone is an effective induction treatment for patients with newly diagnosed MM that warrants further investigation.

Proteasome inhibitors in the treatment of multiple myeloma

Targeting intracellular protein turnover by inhibiting the ubiquitin-proteasome pathway as a strategy for cancer therapy is a new addition to our chemotherapeutic armamentarium, and has seen its greatest successes against multiple myeloma. The first-in-class proteasome inhibitor, bortezomib, was initially approved for treatment of patients in the relapsed/refractory setting as a single agent, and was recently shown to induce even greater benefits as part of rationally designed combinations that overcome chemoresistance. Modulation of proteasome function is also a rational approach to achieve chemosensitization to other antimyeloma agents, and bortezomib has now been incorporated into the front-line setting. Bortezomib-based induction regimens are able to achieve higher overall response rates and response qualities than was the case with prior standards of care, and unlike these older approaches, maintain efficacy in patients with clinically and molecularly defined high-risk disease. Second-generation proteasome inhibitors with novel properties, such as NPI-0052 and carfilzomib, are entering the clinical arena, and showing evidence of antimyeloma activity. In this spotlight review, we provide an overview of the current state of the art use of bortezomib and other proteasome inhibitors against multiple myeloma, and highlight areas for future study that will further optimize our ability to benefit patients with this disease.

Pomalidomide (CC4047) Plus Low-Dose Dexamethasone As Therapy for Relapsed Multiple Myeloma

Purpose

Thalidomide and lenalidomide are immunomodulatory drugs (IMiDs) that produce high remission rates in the treatment of multiple myeloma. Pomalidomide is a new IMiD with high in vitro potency. We report, to our knowledge, the first phase II trial of pomalidomide administered in combination with low-dose dexamethasone for the treatment of relapsed or refractory multiple myeloma.

Patients and Methods

Pomalidomide was administered orally at a dose of 2 mg daily on days 1 through 28 of a 28-day cycle. Dexamethasone 40 mg daily was administered orally on days 1, 8, 15, and 22 of each cycle. Responses were recorded using the criteria of the International Myeloma Working Group.

Results

Sixty patients were enrolled. Thirty-eight patients (63%) achieved confirmed response including complete response in three patients (5%), very good partial response in 17 patients (28%), and partial response in 18 patients (30%). Responses were seen in 40% of lenalidomide-refractory patients, 37% of thalidomide-refractory patients, and 60% of bortezomib-refractory patients. Responses were seen in 74% of patients with high-risk cytogenetic or molecular markers. Toxicity consisted primarily of myelosuppression. Grade 3 or 4 hematologic toxicity consisted of anemia (5%), thrombocytopenia (3%), and neutropenia (32%). One patient (1.6%) had a thromboembolic event. The median progression-free survival time was 11.6 months and was not significantly different in patients with high-risk disease compared with patients with standard-risk disease.

Conclusion

The combination of pomalidomide and low-dose dexamethasone is extremely active in the treatment of relapsed multiple myeloma, including high response rates in patients refractory to other novel agents.

Achievement of at least very good partial response is a simple and robust prognostic factor in patients with multiple myeloma treated with high-dose therapy: long-term analysis of the IFM 99-02 and 99-04 Trials

PURPOSE

The prognostic impact of complete response (CR) achievement in multiple myeloma (MM) has been shown mostly in the context of autologous stem-cell transplantation. Other levels of response have been defined because, even with high-dose therapy, CR is a relatively rare event. The purpose of this study was to analyze the prognostic impact of very good partial response (VGPR) in patients treated with high-dose therapy.

PATIENTS AND METHODS

All patients were included in the Intergroupe Francophone du Myelome 99-02 and 99-04 trials and treated with vincristine, doxorubicin, and dexamethasone (VAD) induction therapy followed by double autologous stem-cell transplantation (ASCT). Best post-ASCT response assessment was available for 802 patients.

RESULTS

With a median follow-up of 67 months, median event-free survival (EFS) and 5-year EFS were 42 months and 34%, respectively, for 405 patients who achieved at least VGPR after ASCT versus 32 months and 26% in 288 patients who achieved only partial remission (P = .005). Five-year overall survival (OS) was significantly superior in patients achieving at least VGPR (74% v 61% P = .0017). In multivariate analysis, achievement of less than VGPR was an independent factor predicting shorter EFS and OS. Response to VAD had no impact on EFS and OS. The impact of VGPR achievement on EFS and OS was significant in patients with International Staging System stages 2 to 3 and for patients with poor-risk cytogenetics t(4;14) or del(17p).

CONCLUSION

In the context of ASCT, achievement of at least VGPR is a simple prognostic factor that has importance in intermediate and high-risk MM and can be informative in more patients than CR.

The role of complete response in multiple myeloma

In multiple myeloma (MM), the impact of complete response (CR) could be shown only after introduction of high-dose therapy plus autologous stem cell transplantation (ASCT). In the context of ASCT, achieving CR (negative immunofixation and normal bone marrow) or at least very good partial response is associated with longer progression-free survival and in most studies longer survival. With novel agents, high CR rates are achieved and this prognostic impact of CR is being shown as well, both in relapsed and in newly diagnosed MM. However the benefit of CR achievement depends on the type of treatment and is not identical for all patients. In elderly patients, treatments inducing more CR may be more toxic. Although CR achievement is necessary in patients with poor-risk disease, it might not be as critical for long survival in more indolent MM. CR achievement is not the only objective of treatment because it is possible to further improve the depth of response and the outcome by continuing treatment after CR achievement. Finally, there are several levels of CR and in the future it will be necessary to confirm the prognostic impact of immunophenotypic or molecular CR or of CR defined by imaging procedures.

Retreatment with bortezomib alone or in combination for patients with multiple myeloma following an initial response to bortezomib

This clinical trial was conducted to determine the safety and efficacy of bortezomib retreatment in patients with multiple myeloma (MM) who had previously responded to bortezomib. Patients with progressive MM who had previously tolerated bortezomib as a single agent or in combination with other drugs, with a minimum of partial response (PR; >or=50% M-protein reduction) for >or=4 months, who had not received intervening MM therapy, were retreated with bortezomib (days 1, 4, 8, and 11 of a 21-day cycle) with a starting dose being the dose at which the patient ended the initial treatment. Patients were allowed to receive bortezomib on retreatment in combination with dexamethasone, thalidomide, or doxorubicin. Thirty-two patients received bortezomib retreatment (most with added dexamethasone). The median treatment-free interval (last dose of initial bortezomib treatment to first dose of retreatment) was 9.9 (range 2.5-34.0) months. The median duration of retreatment was 2.8 (<1-7.9) months; median total duration of bortezomib treatment was 6.7 (2.5-19.8) months. Based on the investigators' assessment of best response, the overall response rate (complete plus PR) was 50%. The median time from start of retreatment to progressive disease (PD) was 6.6 (95% confidence interval: 5.1-9.6) months. Thirteen patients (41%) experienced PN; bortezomib-related SAEs were reported in four patients. Retreatment with bortezomib alone or in combination is effective and well tolerated in patients with MM who have responded to their initial bortezomib treatment.

Dysregulation of unfolded protein response partially underlies proapoptotic activity of bortezomib in multiple myeloma cells

The 26S proteasome inhibitor, bortezomib, has shown remarkable therapeutic efficacy in multiple myeloma (MM), however, the mechanism by which this compound acts remains unknown. Here, we have demonstrated that bortezomib targets the prototypical expression of unfolded protein response (UPR) genes BiP, CHOP and XBP-1 at the mRNA and protein levels, resulting in induction of proapoptotic UPR outputs and suppression of cytoprotective UPR components, leading to caspase-dependent apoptosis in human MM H929 and 8226/S cell lines. Moreover, knockdown of XPB-1s, via lentivirus-mediated RNA interference approach, sensitises MM cells to apoptosis induction by bortezomib. Together, these data strongly suggest that dysregulated or disruptive UPR may, at least partly, underlie the antimyeloma activity of bortezomib.

Combination regimens using doxorubicin and pegylated liposomal doxorubicin prior to autologous transplantation in multiple myeloma

Doxorubicin and pegylated liposomal doxorubicin are key compounds of several induction regimens used prior to autologous stem cell transplantation in patients with de novo multiple myeloma, such as vincristine, doxorubicin, dexamethasone (VAD), vincristine, pegylated liposomal doxorubicin/Doxil, dexamethasone (DVd) or PS-341/bortezomib, doxorubicin, dexamethasone (PAD). The aim of this article is to summarize the more recent data available on the efficacy of these combinations and to discuss their role as part of initial therapy.

The use of novel agents in the treatment of relapsed and refractory multiple myeloma

Although outcomes for patients with multiple myeloma (MM) have improved over the past decade, the disease remains incurable and even patients who respond well to induction therapy ultimately relapse and require additional treatment. Conventional chemotherapy and high-dose therapy with stem cell transplantation (SCT) have historically been utilized in the management of relapsed MM, but in recent years the immunomodulatory drugs (IMiDs) thalidomide and lenalidomide, as well as the proteasome inhibitor bortezomib, have assumed a primary role in this setting. This review focuses on the role of thalidomide, lenalidomide and bortezomib in relapsed and refractory MM, with additional discussion dedicated to emerging drugs in relapsed MM that may prove beneficial to patients with this disease.

Phase II trial of combination therapy with bortezomib, pegylated liposomal doxorubicin, and dexamethasone in patients with newly diagnosed myeloma

PURPOSE

This single-center, open-label, phase II trial evaluated the bortezomib, pegylated liposomal doxorubicin (PLD), and dexamethasone combination regimen (VDD) as initial treatment for patients with newly diagnosed multiple myeloma (MM).

PATIENTS AND METHODS

Enrolled patients (N = 40) received up to six 3-week cycles of treatment with bortezomib 1.3 mg/m(2) intravenously (IV) on days 1, 4, 8, and 11; PLD 30 mg/m(2) IV on day 4; and dexamethasone 20 to 40 mg daily as specified in the study design. The primary end point was the complete/near-complete response (CR/nCR) rate after six cycles. Secondary end points included overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). The impact of VDD on stem-cell mobilization and collection also was evaluated.

RESULTS

After six cycles, the ORR was 85.0% (CR/nCR, 37.5%; very good partial response [VGPR] or better, 57.5%). Patients who underwent stem-cell transplantation (SCT) after VDD (n = 30) experienced increased rates of VGPR or better (53.3% to 76.6% after SCT). Overall, 1-year PFS and OS rates were 92.5% and 97.5%, respectively. Those who achieved VGPR or better after treatment with VDD showed a significantly greater 1-year PFS versus those who achieved less than VGPR (100% v 82%, respectively; P = .03). Similar results were observed in patients who underwent SCT. Grades 3 or 4 hematologic toxicities occurred in < or = 10% of patients; grade 2 painful neuropathy occurred in 7.5%; and grade 3 palmar-plantar erythrodysesthesia occurred in 2.5%.

CONCLUSION

VDD is highly effective for initial treatment of MM followed by SCT in appropriate patients, and it has a reasonable safety profile. Achievement of VGPR or better with this initial therapy predicted longer PFS, regardless of the consolidation therapy given.

Bortezomib in the management of multiple myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by clonal expansion of plasma cells within the bone marrow, the presence of a serum and/or urine monoclonal protein, lytic bone lesions, and anemia. On a cellular level, the disease is characterized by complex interactions between tumor cells and the surrounding bone marrow microenvironment. Understanding of the relationship between malignant plasma cells and the microenvironment has sparked ongoing efforts to develop targeted therapeutic agents for treatment of this disease. The successful development of the first-in-class small-molecule proteasome inhibitor bortezomib occurred as a result of these efforts. This review focuses on the rationale for bortezomib therapy in the treatment of patients with newly diagnosed and relapsed MM, important treatment-related side effects, and future directions for use of bortezomib and other, emerging proteasome inhibitors.

Bortezomib in combination with pegylated liposomal doxorubicin and thalidomide is an effective steroid independent salvage regimen for patients with relapsed or refractory multiple myeloma: results of a phase II clinical trial

Novel agents have demonstrated enhanced efficacy when combined with other antimyeloma agents especially dexamethasone. The steroid doses employed in myeloma regimens are often poorly tolerated. Therefore, in a phase II clinical trial we investigated the efficacy of a steroid-free combination including bortezomib, pegylated liposomal doxorubicin and thalidomide (VDT regimen). Twenty-three patients with relapsed or refractory myeloma or other plasma cell cancers were treated with the VDT regimen. Patient had a median of five prior therapies and 65.2% were refractory to their last regimen. The overall response rates were 55.5% and 22%, respectively. The median progression free survival was 10.9 months (95% CI: 7.3-15.8) and the median overall survival was 15.7 months (95% CI: 9.1-not reached). Fatigue and sensory neuropathy were the most common side effects noted. We observe that VDT is an effective steroid-free regimen with ability to induce durable remission even in patients with refractory myeloma.

Short-term thalidomide incorporated into double autologous stem-cell transplantation improves outcomes in comparison with double autotransplantation for multiple myeloma

PURPOSE

To assess potential benefits with thalidomide incorporated into double autologous stem-cell transplantation (ASCT) for younger patients with newly diagnosed multiple myeloma (MM).

PATIENTS AND METHODS

One hundred thirty-five patients who received thalidomide from induction until the second ASCT were retrospectively analyzed in comparison with an equal number of pair mates treated with double ASCT not including thalidomide.

RESULTS

On an intention-to-treat basis, the addition of thalidomide to double ASCT effected a significant improvement in the rate (68% v 49%; P = .001) and duration (62% v 33% at 4 years; P < .001) of at least very good partial response (VGPR), time to progression (TTP; 61% v 41% at 4 years; P < .001) and progression-free survival (PFS; 51% v 31% at 4 years; P = .001). A trend was also noted for extended overall survival (OS) among thalidomide-treated patients (69% at 5 years v 53% for the control group), although the difference between the two groups was not statistically significant (P = .07). Benefits with thalidomide in increasing the rate of VGPR or better response, TTP, and PFS were confirmed in a multivariate analysis. Median OS after relapse was 24 months for patients receiving thalidomide added to double ASCT and 25 months for the control group. Overall, 17% of patients discontinued thalidomide, including 8% because of drug-related adverse events.

CONCLUSION

In comparison with double ASCT, the addition of first-line thalidomide to double ASCT improved clinical outcomes. Short-term thalidomide was generally well tolerated and had no adverse impact on postrelapse survival.

A phase II evaluation of bortezomib in the treatment of recurrent platinum-sensitive ovarian or primary peritoneal cancer: a Gynecologic Oncology Group study

OBJECTIVE

To determine the activity and pharmacodynamics (PD) of bortezomib in platinum-sensitive epithelial ovarian or primary peritoneal cancer (EOC/PPC).

PATIENTS AND METHODS

Eligible women with recurrent EOC/PPC progressing between 6 and 12 months after initial chemotherapy were treated with bortezomib on days 1, 4, 8, and 11 [1.5 (cohort I) and 1.3 (cohort II) mg/m(2)/dose]. Patients must have had initial chemotherapy only. Response Evaluation Criteria in Solid Tumors (RECIST) was assessed by computed tomography (CT) scan every 2 cycles. 20S proteasome activity was quantified in three pre-treatment and a 1-hour post-treatment (cycle one, day 1) whole blood lysates.

RESULTS

Initially, 26 evaluable patients were treated at the 1.5 mg/m(2)/dose level. Objective response rate was 3.8% (1/26), a partial response. An additional 10 patients (38.5%) had stable disease. Given concerns that treatment discontinuations due to toxicity limited drug exposure/activity a second cohort of 29 evaluable patients was accrued at 1.3 mg/m(2)/dose. The 1.3 mg/m(2)/dose regimen is currently approved as an indication for multiple myeloma and mantle cell lymphoma. Treatment was more tolerable, although objective responses remained low at 6.9% (2/29, partial responses). Second stage accrual was not warranted at either dose. Bortezomib effectively inhibited 20S proteasome activity in whole blood lysates between 37 and 92% in 24/25 (96%) patients in cohort I, and 14-84% in 27/28 (96%) patients in cohort II who provided satisfactory pre- and post-treatment specimens for testing.

CONCLUSION

Bortezomib has minimal activity as a single-agent in the treatment of recurrent platinum-sensitive EOC/PPC. Treatment with bortezomib at 1.5 mg/m(2)/dose was not feasible in this patient population due to excess toxicity. Bortezomib was well tolerated at 1.3 mg/m(2)/dose.

Targeting the ubiquitin proteasome pathway for the treatment of septic shock in patients

Endotoxic shock is a serious systemic inflammatory response to an external biological stressor. The responsiveness of NF-kappaB is built upon rapid protein modification and degradation involving the ubiquitin proteasome pathway. Using transgenic mice, we have obtained in vivo evidence that interference with this pathway can alleviate the symptoms of toxic shock. We posit that administration of proteasome inhibitors may enhance the survival of patients with septic shock.

Multiple myeloma

Multiple myeloma is characterised by clonal proliferation of malignant plasma cells, and mounting evidence indicates that the bone marrow microenvironment of tumour cells has a pivotal role in myeloma pathogenesis. This knowledge has already expanded treatment options for patients with multiple myeloma. Prototypic drugs thalidomide, bortezomib, and lenalidomide have each been approved for the treatment of this disease by targeting both multiple myeloma cells and the bone marrow microenvironment. Although benefit was first shown in relapsed and refractory disease, improved overall response, duration of response, and progression-free and overall survival can be achieved when these drugs are part of first-line regimens. This treatment framework promises to improve outcome not only for patients with multiple myeloma, but also with other haematological malignancies and solid tumours.

Varicella-zoster virus prophylaxis with low-dose acyclovir in patients with multiple myeloma treated with bortezomib

BACKGROUND

Varicella-zoster virus (VZV) reactivation is a common complication in patients with multiple myeloma (MM) treated with bortezomib, with an incidence rate of 10%-60%. The aim of our study was to analyze the effect of acyclovir prophylaxis in this patient population.

PATIENTS AND METHODS

We studied 98 consecutive patients with relapsed MM treated with bortezomib. Bortezomib 1.3 mg/m2 was given on days 1, 4, 8, and 11 of a 21-day cycle. At first, patients did not receive any VZV prophylaxis, but because of the high incidence of VZV reactivation, VZV prophylaxis with acyclovir was implemented subsequently.

RESULTS

A total of 11 patients treated with bortezomib did not have any VZV prophylaxis, and 4 of these 11 patients (36%) developed VZV reactivation in the form of herpes zoster. No VZV reactivations were observed in the 32 patients who received acyclovir 400 mg 3 times daily or the 55 patients who received acyclovir in a dose reduced to 400 mg once daily during bortezomib treatment.

CONCLUSION

Varicellazoster virus reactivation is a common and serious adverse effect of bortezomib treatment. Acyclovir 400 mg once daily is sufficient to protect from VZV reactivation in patients with MM treated with bortezomib.

Clinical and immunohistochemical features associated with a response to bortezomib in patients with multiple myeloma

PURPOSE

Multiple myeloma is an incurable disease with heterogeneous clinical behavior. Bortezomib has offered some patients with relapsed and refractory disease an opportunity for prolonged survival. However, there remains a paucity of data in patients treated with bortezomib that accurately delineates and identifies such patients. This information is crucial to guide management.

EXPERIMENTAL DESIGN

In this study, we aimed to identify the patients most likely to respond to bortezomib salvage therapy. We analyzed the baseline clinical variables and profiled the baseline expression of a broad range of immunohistochemical markers of cell cycle activity, apoptosis, and angiogenesis in a large cohort of multiply relapsed myeloma patients recruited to one of two prospective multicentre trials assessing the efficacy of bortezomib salvage therapy.

RESULTS

Using the European Group for Bone Marrow Transplantation criteria, response (complete or partial) to bortezomib salvage therapy was associated with a previous history of complete response to alternative antimyeloma treatment. Patients who expressed cyclin D1 were more likely to achieve a response. In contrast, patients who expressed p16(INK4A), cytoplasmic p53, and the highest intensity of Bcl-2 staining had a poor response. Patients who achieved a response to bortezomib and those patients who expressed cyclin D1 at baseline showed a significant survival advantage. Patients who expressed FGFR3, a poor prognostic marker, responded equally well and had similar outcomes with bortezomib compared with FGFR3-negative patients.

CONCLUSIONS

Baseline clinical variables and selective immunohistochemical markers expressed by patients may be used effectively to identify patients that are most likely to achieve a meaningful clinical response to bortezomib salvage therapy.

Multiple myeloma: management of adverse events

The combination of conventional chemotherapy or dexamethasone with new drugs, such as immunomodulatory agents and proteasome inhibitors, has substantially changed the treatment paradigm of myeloma patients. New drugs have been incorporated in pre-transplant induction regimens and post-transplant consolidation and maintenance strategies for young patients; in elderly patients, standard melphalan and prednisone (MP) plus thalidomide or plus bortezomib are now considered standards of care, and ongoing trials are assessing if lenalidomide plus standard MP or plus low-dose dexamethasone may be other options. The efficacy of these drugs needs to be balanced against their toxicity. Different drugs have a different toxicity profile. The choice for the best treatment strategy for every single patient should be based on results of scientific randomized studies but tailored to account for patient's biological age, comorbidities, and the expected toxicity profile of different regimens. Prompt dose reduction and accurate management of treatment-related toxicity can greatly reduce early discontinuation rate and significantly improve treatment efficacy. This chapter will focus on frequency and management of main adverse events in newly diagnosed and relapsed myeloma patients and will provide guidelines for dose reductions and supportive therapy.

Treatment of relapsed/refractory multiple myeloma

The introduction of several novel and active treatments and improvements in supportive care of myeloma patients has resulted in a prolongation of the survival of these patients. However, myeloma remains an incurable disease and almost all patients will relapse. Effective management of the relapsing/refractory disease incorporates several different strategies, depending on prior treatments, responses, and duration of responses, as well as residual toxicity, age, and physical condition. High-dose dexamethasone still has a role in the management of disease complications such as cytopenias, renal impairment, or spinal cord compression until another agent is added. High-dose therapy may be considered for selected patients who have a long-term treatment-free interval after their first transplantation. Allogeneic transplantation is limited to selected young patients, preferably with an HLA-matched donor. However, the backbone of current strategies for the management of relapsed/refractory myeloma includes the novel agents thalidomide, bortezomib, and lenalidomide. These agents, either with dexamethasone or in combination with chemotherapy, have shown significant activity both in relapsed and in refractory patients. Based on the results of phase III trials, lenalidomide and bortezomib have increased the post-relapse survival and are active in patients who have received prior novel agents; lenalidomide is active in thalidomide-pretreated or bortezomib-pretreated patients and bortezomib alone or in combination with chemotherapy is active in thalidomide/lenalidomide-pretreated patients. Combinations of novel agents show synergistic activity and may overcome drug resistance. Finally, special consideration is needed for the management of patients with renal impairment or other poor prognostic features.

Clinical development of novel proteasome inhibitors for cancer treatment

BACKGROUND

Emerging evidence demonstrates that targeting the tumor proteasome is a promising strategy for cancer therapy.

OBJECTIVE

This review summarizes recent results from cancer clinical trials using specific proteasome inhibitors or some natural compounds that have proteasome-inhibitory effects.

METHODS

A literature search was carried out using PubMed. Results about the clinical application of specific proteasome inhibitors and natural products with proteasome-inhibitory activity for cancer prevention or therapy were reviewed.

RESULTS/CONCLUSION

Bortezomib, the reversible proteasome inhibitor that first entered clinical trials, has been studied extensively as a single agent and in combination with glucocorticoids, cytotoxic agents, immunomodulatory drugs and radiation as treatment for multiple myeloma and other hematological malignancies. The results in some cases have been impressive. There is less evidence of bortezomib's efficacy in solid tumors. Novel irreversible proteasome inhibitors, NPI-0052 and carfilzomib, have also been developed and clinical trials are underway. Natural products with proteasome-inhibitory effects, such as green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG), soy isoflavone genistein, and the spice turmeric compound curcumin, have been studied alone and in combination with traditional chemotherapy and radiotherapy against various cancers. There is also interest in developing these natural compounds as potential chemopreventive agents.

Doxorubicin-induced platelet cytotoxicity: a new contributory factor for doxorubicin-mediated thrombocytopenia

BACKGROUND

Doxorubicin (DOX) is a widely used anticancer drug for solid tumors and hematologic malignancy, but its active use is hampered by serious adverse effects, including thrombocytopenia. Although bone marrow toxicity of DOX has been suggested to be the sole mechanism underlying the reduced platelet counts, the direct effects of DOX on platelets have never been examined.

OBJECTIVE

Here, we investigated the DOX-induced platelet cytotoxicity and its underlying mechanism in an effort to elucidate the contribution of platelet cytotoxicity to DOX-induced thrombocytopenia.

RESULTS

In freshly isolated human platelets, DOX induced platelet cytotoxicity in a time-dependent and concentration-dependent manner. Reactive oxygen species (ROS) generation, decreased glutathione levels and subsequent protein thiol depletion were shown to underlie the DOX-induced platelet cytotoxicity. Conspicuously, DOX-treated platelets displayed apoptotic features such as caspase-3 activation, reduced mitochondrial transmembrane potential, and phosphatidylserine exposure. Decreased glutathiolation of procaspase-3 was shown to be a link between protein thiol depletion and caspase-3 activation. It is of note that DOX-mediated platelet cytotoxicity was significantly enhanced by shear stress, a common complicating factor in cancer patients. These in vitro results were further confirmed by an in vivo animal model, where administration of DOX induced a platelet count decrease, ROS generation, caspase-3 activation, protein thiol depletion, and damaged platelet integrity.

CONCLUSION

We demonstrated that DOX can directly induce platelet cytotoxicity through ROS generation, decreased glutathione levels, and protein thiol depletion. We believe that this study provides important evidence for the role of DOX-induced platelet cytotoxicity in the development of thrombocytopenia in DOX-treated patients.

The ubiquitin-proteasome system in cancer, a major player in DNA repair. Part 2: transcriptional regulation

DNA repair is an indispensable part of a cell’s defence system against the devastating effects of DNA-damaging conditions. The regulation of this function is a really demanding situation, particularly when the stressing factors persist for a long time. In such cases, the depletion of existing DNA repair proteins has to be compensated by the induction of the analogous gene products. In addition, the arrest of transcription, which is another result of many DNA-damaging agents, needs to be overcome through regulation of transcription-specific DNA repair pathways. The involvement of the ubiquitin-proteasome system (UPS) in cancer- and chemotherapy-related DNA-damage repair relevant to the above transcriptional modification mechanisms are illustrated in this review. Furthermore, the contribution of UPS to the regulation of localization and accessibility of DNA repair proteins to chromatin, in response to cellular stress is discussed.

Emerging therapies for multiple myeloma

Multiple myeloma (MM) is a clonal plasma cell malignancy clinically characterized by osteolytic lesions, immunodeficiency, and renal disease. There are an estimated 750,000 people diagnosed with MM worldwide, with a median overall survival of 3 - 5 years. Besides chromosomal aberrations, translocations, and mutations in essential growth and tumor-suppressor genes, accumulating data strongly highlight the pathophysiologic role of the bone marrow (BM) microenvironment in MM pathogenesis. Based on this knowledge, several novel agents have been identified, and treatment options in MM have fundamentally changed during the last decade. Thalidomide, bortezomib, and lenalidomide have been incorporated into conventional cytotoxic and transplantation regimens, first in relapsed and refractory and now also in newly diagnosed MM. Despite these significant advances, there remains an urgent need for more efficacious and tolerable drugs. Indeed, a plethora of preclinical agents awaits translation from the bench to the bedside. This article reviews the scientific rationale of new therapy regimens and newly identified therapeutic agents - small molecules as well as therapeutic antibodies - that hold promise to further improve outcome in MM.

Clinical challenges associated with bortezomib therapy in multiple myeloma and Waldenströms Macroglobulinemia

Rapid development of the small molecule proteasome inhibitor bortezomib has yielded important clinical benefit for patients with multiple myeloma. Early phase clinical trials suggest the agent has similar efficacy in Waldenströms Macroglobulinemia. Optimization of bortezomib-based therapy, though, requires an understanding of the various challenges associated with use of the drug. This review highlights the rationale for bortezomib therapy in patients with multiple myeloma and Waldenströms Macroglobulinemia, mechanisms of bortezomib resistance, important therapy-related side effects, and new directions for the use of proteasome inhibitors in these disorders.

Ascorbic acid inhibits antitumor activity of bortezomib in vivo

Earlier studies have shown that ascorbic acid (vitamin C) inhibits bortezomib-induced cytotoxicity against cancer cells in vitro. However, the clinical significance of vitamin C on bortezomib treatment is unclear. In this study, we examined whether daily oral intake of vitamin C inhibits antimultiple myeloma (MM) activities of bortezomib. Vitamin C, at orally achievable concentrations, inhibited in vitro MM cell cytotoxicity of bortezomib and blocked its inhibitory effect on 20S proteasome activity. Specifically, plasma collected from healthy volunteers taking 1 g/day vitamin C reduced bortezomib-induced MM cell death in vitro. This antagonistic effect of vitamin C against proteasome inhibitors is limited to the boronate class of inhibitors (bortezomib and MG262). In vivo activity of this combination treatment was then evaluated using our xenograft model of human MM in SCID (severe combined immune-deficient) mice. Bortezomib (0.1 mg/kg twice a week for 4 weeks) significantly inhibits in vivo MM cell growth, which was blocked by oral vitamin C (40 mg/kg/day). Therefore, our results for the first time show that vitamin C can significantly reduce the activity of bortezomib treatment in vivo; and importantly, suggest that patients receiving treatment with bortezomib should avoid taking vitamin C dietary supplements.

Combining milatuzumab with bortezomib, doxorubicin, or dexamethasone improves responses in multiple myeloma cell lines

PURPOSE

The humanized anti-CD74 monoclonal antibody, milatuzumab, is in clinical evaluation for the therapy of multiple myeloma (MM). The ability of milatuzumab to increase the efficacy of bortezomib, doxorubicin, and dexamethasone was examined in three human CD74+ MM cell lines, CAG, KMS11, KMS12-PE, and one CD74-MM cell line, OPM-2.

EXPERIMENTAL DESIGN

Activity of milatuzumab as a monotherapy and combined with the drugs was evaluated by studying in vitro cytotoxicity, signaling and apoptotic pathways, and in vivo therapeutic activity in severe combined immunodeficient (SCID) mouse models of MM.

RESULTS

Given as a monotherapy, cross-linked milatuzumab, but not milatuzumab alone, yielded significant antiproliferative effects in CD74+ cells. The combination of cross-linked milatuzumab with bortezomib, doxorubicin, or dexamethasone caused more growth inhibition than either cross-linked milatuzumab or drug alone, producing significant reductions in the IC(50) of the drugs when combined. Efficacy of combined treatments was accompanied by increased levels of apoptosis measured by increases of activated caspase-3 and hypodiploid DNA. Both milatuzumab and bortezomib affect the nuclear factor-kappaB pathway in CAG MM cells. In CAG- or KMS11-SCID xenograft models of disseminated MM, milatuzumab more than doubled median survival time, compared with up to a 33% increase in median survival with bortezomib but no significant benefit with doxorubicin. Moreover, combining milatuzumab and bortezomib increased survival significantly compared with either treatment alone.

CONCLUSIONS

The therapeutic efficacies of bortezomib, doxorubicin, and dexamethasone are enhanced in MM cell lines when given in combination with milatuzumab, suggesting testing these combinations clinically.

Role of combination bortezomib and pegylated liposomal doxorubicin in the management of relapsed and/or refractory multiple myeloma

The first in class proteasome inhibitor bortezomib (B) received its initial regulatory approval for therapy of patients with multiple myeloma (MM) in the relapsed/refractory setting. Modulation of proteasome function, however, is also a rational strategy for chemosensitization, and a variety of agents have shown synergistic activity with bortezomib pre-clinically, including anthracyclines. This formed the basis for evaluation of a regimen of bortezomib with pegylated liposomal doxorubicin (PLD). PLD+B, in a phase I study, induced a predictable and manageable toxicity profile, and showed encouraging anti-MM activity. In a recent international, randomized phase III trial, PLD+B demonstrated a superior overall response rate and response quality compared to bortezomib alone, as well as a longer time to progression, duration of response, progression-free survival, and overall survival. Sub-analyses revealed benefits in almost all clinically relevant subgroups, including several which would be considered to have high-risk disease. These findings have led to the establishment of the PLD+B regimen as one of the standards of care for patients with relapsed and/or refractory myeloma. Efforts are now underway to build on this combination further by adding other active anti-myeloma agents. In this review, we will discuss the role of PLD+B as an important addition to our therapeutic armamentarium for patients with MM.

Pegylated liposomal Doxorubicin: a review of its use in the treatment of relapsed or refractory multiple myeloma

Pegylated liposomal doxorubicin (Doxil, Caelyx) is associated with less frequent neutropenia, alopecia and cardiotoxicity than conventional doxorubicin and has an improved pharmacokinetic profile, allowing for intravenous administration over 1 hour. In the US and EU (as well as a number of other countries), pegylated liposomal doxorubicin is approved for use in combination with the proteasome inhibitor bortezomib for the treatment of patients with relapsed or refractory multiple myeloma. Results of the primary efficacy analysis of a large phase III trial in bortezomib-naive patients with relapsed or refractory multiple myeloma demonstrated that the combination of pegylated liposomal doxorubicin plus bortezomib significantly prolonged the time to progression (TTP) compared with bortezomib alone. In addition, pegylated liposomal doxorubicin plus bortezomib significantly increased TTP in most subgroup analyses, including in patients with or without previous anthracycline exposure. A number of secondary outcomes, including progression-free survival and overall survival at 15 months, were also improved with the combination compared with bortezomib alone in the overall study population. Pegylated liposomal doxorubicin plus bortezomib was associated with a higher incidence of grade 3 or 4 adverse events than bortezomib alone, which was mainly attributed to an increase in myelosuppression and gastrointestinal events with the combination. These events were predictable and often managed by dosage modifications and supportive therapy. The addition of pegylated liposomal doxorubicin to bortezomib treatment did not increase the incidence of cardiotoxicity or peripheral neuropathy, but did induce hand-foot syndrome in a proportion of patients. Pegylated liposomal doxorubicin plus bortezomib is now established as an additional standard of care in the treatment of patients with relapsed or refractory multiple myeloma who have received at least one prior therapy.

Pegylated liposomal doxorubicin plus bortezomib in relapsed or refractory multiple myeloma: efficacy and safety in patients with renal function impairment

A retrospective analysis was undertaken of patients (n = 193) with renal insufficiency (creatinine clearance [CrCl] < 60 mL/min) from a phase III trial comparing bortezomib +/- pegylated liposomal doxorubicin (PLD) in relapsed/refractory myeloma (n = 646). The response rate (49% vs. 42%) and median time to disease progression (331 days vs. 199 days) were comparable or slightly better for patients with renal insufficiency treated with PLD/bortezomib compared with patients treated with bortezomib alone. There was a steady, clinically meaningful improvement in renal function for patients with renal insufficiency in both treatment arms. However, patients with impaired renal function were at a slightly increased risk of a drug-related serious adverse event (28% vs. 19% for CrCl < 60 and > or = 60 mL/min, respectively).

The vital link between the ubiquitin-proteasome pathway and DNA repair: impact on cancer therapy

Proteasome-dependent protein degradation is involved in a variety of biological processes, including cell-cycle regulation, apoptosis, and stress-responses. Growing evidence from translational research and clinical trials proved the effectiveness of proteasome inhibitors (PIs) in treating several types of hematological malignancies. Although various key molecules in ubiquitin-dependent cellular processes have been proposed as relevant targets of therapeutic proteasome inhibition, our current understanding is far from complete. Recent rapid progress in DNA repair research has unveiled a crucial role of the ubiquitin-proteasome pathway (UPP) in regulating DNA repair. These findings thus bring up the idea that DNA repair pathways could be effective targets of PIs in mediating their cytotoxicity and enhancing the effect of radiotherapy and some DNA-damaging chemotherapeutic agents, such as cisplatin and camptothecin. In this review, we present the current perspective on the UPP-dependent regulatory mechanisms of DNA repair and discuss their therapeutic potential in the application of PIs to a broad spectrum of human cancers.

Complete remission of primary plasma cell leukemia with bortezomib, doxorubicin, and dexamethasone: a case report

Background

Plasma cell leukemia (PCL) is a rare lymphoproliferative disorder considered to be a variant of multiple myeloma. It is an aggressive disease with a poor clinical response to standard chemotherapeutic agents.

Case presentation

A novel regimen consisting of bortezomib, doxorubicin, and dexamethasone is currently under active evaluation for the treatment of multiple myeloma. We employed this combination as front-line chemoinduction therapy for a case of primary PCL.

Conclusion

Complete remission was achieved with rapid normalization of hematologic parameters. The combination of bortezomib, doxorubicin and dexamethasone demonstrates promise in the treatment of PCL.

Oncology: Treatment of Multiple Myeloma in the Targeted Therapy Era

Objective:

To review the clinical trials that have impacted treatment standards of multiple myeloma (MM).

Data Source:

A PubMed search (1980–June 2008) restricted to English-language publications was conducted using the key words multiple myeloma, clinical trials, targeted therapy, thalidomide, lenalidomide, bortezomib, dexamethasone, melphalan, autologous stem-cell transplantation, and tumor biology. Abstracts emanating from the meetings of the American Society of Clinical Oncology and American Society of Hematology from June 2002 to June 2008 were also reviewed.

Data Synthesis:

Although hematopoietic stem-cell transplantation has improved the response rate and duration of overall survival, MM remains an incurable disease. However, focused research aimed at the molecular basis of the disease has led to a number of new treatment strategies. Evidence from clinical trials indicates that each of the 3 novel agents, thalidomide, lenalidomide, and bortezomib, is remarkably effective as first-line therapy. The data also suggest that clinicians may need to reevaluate the role of stem-cell transplantation in the disease.

Conclusions:

Thalidomide, lenalidomide, or bortezomib in combination with dexamethasone have replaced traditional chemotherapy such as melphalan, doxorubicin, and vincristine as initial therapy of patients with MM who are eligible for stem-cell transplantation. Furthermore, these novel drugs can be incorporated into regimens used to treat transplant-ineligible patients or those with relapsing disease.

Lenalidomide, adriamycin, and dexamethasone (RAD) in patients with relapsed and refractory multiple myeloma: a report from the German Myeloma Study Group DSMM (Deutsche Studiengruppe Multiples Myelom)

We conducted a phase 1/2 trial combining lenalidomide (R) with adriamycin (A) and dexamethasone (D) for relapsed and relapsed-refractory myeloma to determine tolerability and efficacy of this novel regimen, RAD, delivered for six 28-day cycles. A total of 69 intensively pretreated patients with a median age of 65 years (range, 46-77 years) were enrolled. Using pegfilgrastim (G), the maximum tolerated dose (MTD) was formally not reached at the highest dose level (R, 25 mg on days 1-21; A, 9 mg/m(2) intravenously on days 1-4; and D, 40 mg on days 1-4 and 17-20; dose level 5+G), which was then used to determine efficacy. Grades 3/4 neutropenia and thrombocytopenia were seen in 48% and 38% of patients, respectively. Thromboembolic events occurred in 4.5% and severe infections in 10.5% of patients. On an intent-to treat analysis, overall response rate (ORR) was 73% for the whole study and 77% including 74% complete response (CR) plus very good partial response (VGPR) for dose level 5+G. Response rates and progression-free survival did not differ between relapsed and relapsed-refractory patients. Deletion of chromosome 17p and elevated beta(2)-microglobulin were associated with significantly inferior response and shortened time to progression. In conclusion, RAD induces substantial and durable remission with an acceptable toxicity profile in patients with relapsed and relapsed-refractory myeloma. This trial was registered at www.ClinicalTrials.gov as no. NCT00306813.