A Phase II trial of weekly bortezomib and dexamethasone in veterans with newly diagnosed multiple myeloma not eligible for or who deferred autologous stem cell transplantation

Targeting the Ubiquitin-Proteasome System for Cancer Therapeutics by Small-Molecule Inhibitors

The ubiquitin-proteasome system (UPS) is a critical regulator of cellular protein levels and activity. It is, therefore, not surprising that its dysregulation is implicated in numerous human diseases, including many types of cancer. Moreover, since cancer cells exhibit increased rates of protein turnover, their heightened dependence on the UPS makes it an attractive target for inhibition via targeted therapeutics. Indeed, the clinical application of proteasome inhibitors in treatment of multiple myeloma has been very successful, stimulating the development of small-molecule inhibitors targeting other UPS components. On the other hand, while the discovery of potent and selective chemical compounds can be both challenging and time consuming, the area of targeted protein degradation through utilization of the UPS machinery has seen promising developments in recent years. The repertoire of proteolysis-targeting chimeras (PROTACs), which employ E3 ligases for the degradation of cancer-related proteins via the proteasome, continues to grow. In this review, we will provide a thorough overview of small-molecule UPS inhibitors and highlight advancements in the development of targeted protein degradation strategies for cancer therapeutics.

Bortezomib-based therapy for relapsed/refractory multiple myeloma in real-world medical practice

OBJECTIVE

The efficacy and safety of bortezomib-based therapy for relapsed/refractory multiple myeloma (RRMM) in clinical trials may differ from the oncology practice experience. The electronic VELCADE^® OBservational Study was designed to prospectively evaluate bortezomib for multiple myeloma (MM) in real-world medical practice.

METHOD

Patients scheduled to receive intravenous bortezomib for MM were eligible. The primary objective was to evaluate clinical outcomes, including response, time to response, time to next therapy, treatment-free interval, progression-free survival (PFS), and overall survival (OS). Secondary objectives included safety and healthcare resource utilization.

RESULTS

In total, 873 patients with a median of two therapy lines prior to initiating bortezomib were included. The overall response rate (≥partial response) was 69%, including 37% complete response/near-complete response. Median time to response was 1.8 months, median time to next therapy was 9.7 months, and median treatment-free interval was 7.9 months. After 22.6 months' median follow-up, median PFS was 12.0 months and median OS was 36.1 months. The most common adverse events (AEs) were neuropathy not otherwise specified (19%), diarrhea NOS, and thrombocytopenia (each 17%); 230 (26%) patients discontinued bortezomib due to AEs. Of 689 (79%) patients without baseline peripheral neuropathy (PN), the rate of new-onset any-grade PN increased to 51% (12% grade 3/4) by cycle 8. Overall, 244 (28%) patients were hospitalized, 372 (43%) attended an outpatient visit, and 341 (39%) underwent a diagnostic/therapeutic procedure during bortezomib treatment.

CONCLUSION

These prospective real-world data demonstrate the effectiveness and safety of bortezomib-based therapy for RRMM and confirm high response rates and long OS for this population.

Nuances in the Management of Older People With Multiple Myeloma

Multiple myeloma is a disease of the elderly, with about a third of patients at diagnosis older than 75 years of age. Yet, the population of elderly patients is heterogeneous: older patients are more likely to have comorbidities and frailties complicating both their initial diagnosis and subsequent management, but these are not consistent across the group. Furthermore, patients with comorbidities and frailty are generally underrepresented in clinical trials. Despite the survival of myeloma patients increasing following the introduction of novel agents, older patients continue to have worse outcomes with increased treatment-related toxicity. Treatment tolerability is not defined by age alone, rather a combination of age, physical function, cognitive function, and comorbidities. These factors all influence patients' tolerability of treatment and therefore treatment efficacy and should also be considered when reviewing the results of clinical trials. It is the nuances of determining how these factors interact that should influence initial treatment and ongoing management decisions and these will be discussed here.

The Singapore Myeloma Study Group Consensus Guidelines for the management of patients with multiple myeloma

Multiple myeloma (MM) is an incurable plasma cell neoplasm with an incidence of 100 patients per year in Singapore. Major advances have been made in the diagnosis, risk stratification and treatment of MM in the recent past. The reclassification of a subset of patients with smouldering MM, based on high-risk biomarkers, and the development of the revised international staging system are among the key new developments in diagnosis and staging. The use of novel agent-based treatment has resulted in significant improvements in the survival and quality of life of many patients with MM. Determining the optimal use of proteasome inhibitors, immunomodulators and, more recently, monoclonal antibodies is an area of ongoing investigation. In this guideline, we aim to provide an overview of the management of MM, incorporating the latest developments in diagnosis and treatment.

Current Trends of Renal Impairment in Multiple Myeloma

BACKGROUND

Renal impairment (RI) is a common complication of multiple myeloma (MM). Around 50% of patients with MM have RI at presentation, and up to 5% require dialysis treatment. Severe acute kidney injury (AKI) as a cause of RI is a particular challenge as historically the survival of patients who sustain this complication and require dialysis is very poor. However, in this current period, survival is improving and the focus is on optimum use of novel chemotherapies and the evaluation of extra-corporeal therapies for removal of serum immunoglobulin light chains.

SUMMARY

RI in patients with MM is commonly associated with excess monoclonal free light chain (FLC) production; myeloma cast nephropathy is the predominant renal pathology in patients presenting with severe RI secondary to AKI. The majority of patients have mild to moderate RI and recover renal function. However, patients with more severe RI, in particular those with a requirement for dialysis, are less likely to recover renal function. Rapid diagnosis and prompt institution of anti-myeloma therapy is an important determinant of renal function recovery, through targeting early and sustained reduction of involved monoclonal FLC. Novel agents are associated with excellent disease response, and bortezomib is now widely used as a first-line agent in the management of MM in patients with severe RI. Extended haemodialysis using high cut-off dialysers is more effective for extracorporeal removal of FLC than plasma exchange, and clinical trials are in process. High-dose chemotherapy with autologous stem cell transplantation does have a role in patients with severe RI but requires careful patient selection.

KEY MESSAGES

RI is very common in patients with MM, and renal function recovery is associated with improved clinical outcomes. We summarise the epidemiology of MM in the UK, present the impact of RI and renal function recovery on patient outcome, and describe the current management of MM in western countries.

FACTS FROM EAST AND WEST

(1) A serum creatinine level >2 mg/dl has been reported in 16, 21, 24, and 33% of patients with MM in cohort studies from Japan, Europe, China, and Korea, respectively. A creatinine clearance rate <30 ml/min was observed in 30 and 15% of patients in Chinese and Western MM cohorts, respectively. The commonest cause of severe RI in patients with MM is myeloma cast nephropathy. (2) The efficacy of novel treatments (bortezomib, carfilzomib, thalidomide, and lenalidomide) has predominantly been assessed in Western patients. Bortezomib and dexamethasone are the current standard of care for MM and severe RI in the West. Severe RI is not a contraindication to autologous stem cell transplantation (ASCT). Most of the data are from the West; there are case reports from China describing good outcomes with ASCT. The removal of FLC by high-cut-off hemodialysis is under evaluation in randomized controlled trials (RCTs) in the West. Studies in this area are not yet conducted in China. In China, new treatments, such as bortezomib, are more widely used than before, and favorable results are being reported; however, RCT studies are still needed in this area to confirm the efficacy and safety of this and other novel treatments.

Once-Weekly 1.6 mg/m2 Bortezomib BCD Regimen in Elderly Patients with Newly Diagnosed Multiple Myeloma Who are Unfit for Standard Dose Chemotherapy

Bortezomib has shown anti-myeloma effects in combination with alkylating agents, but clinical benefits can be limited by neurotoxicity. There is less information on the efficacy and tolerability of once-weekly 1.6 mg/m² bortezomib combined with cyclophosphamide and dexamethasone (BCD) regimen in elderly patients with newly diagnosed multiple myeloma who are unfit for standard dose chemotherapy. Here, we report our experience of weekly 1.6 mg/m² intravenous bortezomib in this group of patients. Between March 2010 and February 2015, we treated 34 newly diagnosed elderly patients with the combination of bortezomib 1.6 mg/m² intravenously on days 1 and 8; cyclophosphamide 200 mg/m² intravenously on days 1-4; dexamethasone 20 mg intravenously on days 1-4, and 8-11. Among the 34 patients, 14 (41 %) responded with complete response (CR), 6 (18 %) with very good partial response (VGPR) and 10 (29 %) with partial response (PR). The overall response rates were 88 %. After 2 cycles of treatments, the survival of patients who attained a response of VGPR or CR was significantly longer than those with PR or resistance to BCD, for both progression-free survival (PFS) (21.4 vs. 10.6 months, p = 0.002) and overall survival (OS) (23.0 vs. 16.8 months, p = 0.043). The 2-year PFS and OS were 26.5 and 64.7 % respectively in these elderly multiple myeloma patients in our study. Grade 1/2 neuropathy was observed in 20 % of the cycles while grade 3/4 neuropathy was not observed. No patients withdrew due to neuropathy or other side effects. Once-weekly bortezomib at 1.6 mg/m² BCD regimen is both effective and safe in elderly patients with newly diagnosed multiple myeloma who are unfit for standard dose chemotherapy.