Therapeutic approaches to myeloma bone disease: an evolving story

Bone Marrow Mesenchymal Stromal Cells in Multiple Myeloma: Their Role as Active Contributors to Myeloma Progression

Multiple myeloma (MM) is a hematological malignancy of plasma cells that proliferate and accumulate within the bone marrow (BM). Work from many groups has made evident that the complex microenvironment of the BM plays a crucial role in myeloma progression and response to therapeutic agents. Within the cellular components of the BM, we will specifically focus on mesenchymal stromal cells (MSCs), which are known to interact with myeloma cells and the other components of the BM through cell to cell, soluble factors and, as more recently evidenced, through extracellular vesicles. Multiple structural and functional abnormalities have been found when characterizing MSCs derived from myeloma patients (MM-MSCs) and comparing them to those from healthy donors (HD-MSCs). Other studies have identified differences in genomic, mRNA, microRNA, histone modification, and DNA methylation profiles. We discuss these distinctive features shaping MM-MSCs and propose a model for the transition from HD-MSCs to MM-MSCs as a consequence of the interaction with myeloma cells. Finally, we review the contribution of MM-MSCs to several aspects of myeloma pathology, specifically to myeloma growth and survival, drug resistance, dissemination and homing, myeloma bone disease, and the induction of a pro-inflammatory and immunosuppressive microenvironment.

A Retrospective Analysis: A Novel Index Predicts Survival and Risk-Stratification for Bone Destruction in 419 Newly Diagnosed Multiple Myelomas

Objective

Multiple myeloma (MM) patients with bone destruction are difficult to restore, so it is of great clinical significance to further explore the factors affecting MM bone destruction.

Methods and results

This study retrospectively analyzed 419 cases with MM. Multiple linear regression analysis showed that those MM patients with a higher concentration of Ca²⁺ in serum, higher positive rate of CD138 immuno-phenotype and advanced in stage with 13q34 deletion in cytogenetics would be more prone to bone destruction, while total bile acid (TBA) and kappa chain isotope negatively correlated with bone destruction in MM patients. The Kaplan-Meier analysis indicated that Ca²⁺, serum β2-microglobulin (β2-MG), hemoglobin (HGB), creatinine (CREA), uric acid (UA) and age correlated with the survival of bone destruction in MM patients. Cox regression analysis further showed that the independent prognostic factors of β2-MG and CREA had a higher risk for early mortality in bone destruction patients. Moreover, an index was calculated based on β2-MG and globulin (GLB) to white blood cell (WBC) ratio to predict the poor survival of bone destruction patients.

Conclusion

We provide a novel marker to predict the prognosis of myeloma patients using routine examination method instead of bone marrow aspiration, and provide a reference for clinical evaluation.

Heme oxygenase-1 attenuates the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in multiple myeloma cells: Corelated with bortezomib tolerance in multiple myeloma

Osteoclasts (OCs) play an essential role in bone destruction in patients with multiple myeloma (MM). Bortezomib can ameliorate bone destruction in patients with MM, but advanced MM often resists bortezomib. We studied the molecular mechanisms of bortezomib tolerance in MM. The expression of the MM-related genes in newly diagnosed patients with MM and normal donors were studied. C-C motif chemokine ligand 3 (CCL3) is a cytokine involved in the differentiation of OCs, and its expression is closely related to APRIL (a proliferation-inducing ligand). We found that bortezomib treatment inhibited APRIL and CCL3. But the heme oxygenase-1 (HO-1) activator hemin attenuated the inhibitory effects of bortezomib on APRIL and CCL3. We induced mononuclear cells to differentiate into OCs, and the enzyme-linked immunosorbent assay showed that the more OCs differentiated, the higher the levels CCL3 secretions detected. Animal experiments showed that hemin promoted MM cell infiltration in mice. The weight and survival rate of tumor mice were associated with HO-1 expression. Immunohistochemical staining showed that HO-1, APRIL, and CCL3 staining were positively stained in the tumor infiltrating sites. Then, MM cells were transfected with L-HO-1/si-HO-1 expression vectors and cultured with an nuclear factor (NF)-kappa B (κB) pathway inhibitor, QNZ. The results showed that HO-1 was the upstream gene of APRIL, NF-κB, and CCL3. We showed that HO-1 could attenuate the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in MM cells, and the tolerance of MM cells to bortezomib and the promotion of bone destruction are related to HO-1.

Metastatic bone disease: Pathogenesis and therapeutic options: Up-date on bone metastasis management

Bone metastases (BM) are a common complication of cancer, whose management often requires a multidisciplinary approach. Despite the recent therapeutic advances, patients with BM may still experience skeletal-related events and symptomatic skeletal events, with detrimental impact on quality of life and survival. A deeper knowledge of the mechanisms underlying the onset of lytic and sclerotic BM has been acquired in the last decades, leading to the development of bone-targeting agents (BTA), mainly represented by anti-resorptive drugs and bone-seeking radiopharmaceuticals. Recent pre-clinical and clinical studies have showed promising effects of novel agents, whose safety and efficacy need to be confirmed by prospective clinical trials. Among BTA, adjuvant bisphosphonates have also been shown to reduce the risk of BM in selected breast cancer patients, but failed to reduce the incidence of BM from lung and prostate cancer. Moreover, adjuvant denosumab did not improve BM free survival in patients with breast cancer, suggesting the need for further investigation to clarify BTA role in early-stage malignancies. The aim of this review is to describe BM pathogenesis and current treatment options in different clinical settings, as well as to explore the mechanism of action of novel potential therapeutic agents for which further investigation is needed.

SRC kinase inhibition with saracatinib limits the development of osteolytic bone disease in multiple myeloma

Multiple myeloma (MM)-associated osteolytic bone disease is a major cause of morbidity and mortality in MM patients and the development of new therapeutic strategies is of great interest. The proto-oncogene SRC is an attractive target for such a strategy. In the current study, we investigated the effect of treatment with the SRC inhibitor saracatinib (AZD0530) on osteoclast and osteoblast differentiation and function, and on the development of MM and its associated bone disease in the 5TGM.1 and 5T2MM murine MM models. In vitro data showed an inhibitory effect of saracatinib on osteoclast differentiation, polarization and resorptive function. In osteoblasts, collagen deposition and matrix mineralization were affected by saracatinib. MM cell proliferation and tumor burden remained unaltered following saracatinib treatment and we could not detect any synergistic effects with drugs that are part of standard care in MM. We observed a marked reduction of bone loss after treatment of MM-bearing mice with saracatinib as reflected by a restoration of trabecular bone parameters to levels observed in naive control mice. Histomorphometric analyses support that this occurs through an inhibition of bone resorption. In conclusion, these data further establish SRC inhibition as a promising therapeutic approach for the treatment of MM-associated osteolytic bone disease.

Gamabufotalin triggers c-Myc degradation via induction of WWP2 in multiple myeloma cells

Deciding appropriate therapy for multiple myeloma (MM) is challenging because of the occurrence of multiple chromosomal changes and the fatal nature of the disease. In the current study, gamabufotalin (GBT) was isolated from toad venom, and its tumor-specific cytotoxicity was investigated in human MM cells. We found GBT inhibited cell growth and induced apoptosis with the IC50 values <50 nM. Mechanistic studies using functional approaches identified GBT as an inhibitor of c-Myc. Further analysis showed that GBT especially evoked the ubiquitination and degradation of c-Myc protein, thereby globally repressing the expression of c-Myc target genes. GBT treatment inhibited ERK and AKT signals, while stimulating the activation of JNK cascade. An E3 ubiquitin-protein ligase, WWP2, was upregulated following JNK activation and played an important role in c-Myc ubiquitination and degradation through direct protein-protein interaction. The antitumor effect of GBT was validated in a xenograft mouse model and the suppression of MM-induced osteolysis was verified in a SCID-hu model in vivo. Taken together, our study identified the potential of GBT as a promising therapeutic agent in the treatment of MM.

The anti-myeloma activity of bone morphogenetic protein 2 predominantly relies on the induction of growth arrest and is apoptosis-independent

Multiple myeloma (MM), a malignancy of the bone marrow, is characterized by a pathological increase in antibody-producing plasma cells and an increase in immunoglobulins (plasmacytosis). In recent years, bone morphogenetic proteins (BMPs) have been reported to be activators of apoptotic cell death in neoplastic B cells in MM. Here, we use bone morphogenetic protein 2 (BMP2) to show that the "apoptotic" effect of BMPs on human neoplastic B cells is dominated by anti-proliferative activities and cell cycle arrest and is apoptosis-independent. The anti-proliferative effect of BMP2 was analysed in the human cell lines KMS12-BM and L363 using WST-1 and a Coulter counter and was confirmed using CytoTox assays with established inhibitors of programmed cell death (zVAD-fmk and necrostatin-1). Furthermore, apoptotic activity was compared in both cell lines employing western blot analysis for caspase 3 and 8 in cells treated with BMP2 and FasL. Additionally, expression profiles of marker genes of different cell death pathways were analysed in both cell lines after stimulation with BMP2 for 48h using an RT-PCR-based array. In our experiments we observed that there was rather no reduction in absolute cell number, but cells stopped proliferating following treatment with BMP2 instead. The time frame (48–72 h) after BMP2 treatment at which a reduction in cell number is detectable is too long to indicate a directly BMP2-triggered apoptosis. Moreover, in comparison to robust apoptosis induced by the approved apoptotic factor FasL, BMP2 only marginally induced cell death. Consistently, neither the known inhibitor of apoptotic cell death zVAD-fmk nor the necroptosis inhibitor necrostatin-1 was able to rescue myeloma cell growth in the presence of BMP2.

I‑BET151 inhibits osteoclastogenesis via the RANKL signaling pathway in RAW264.7 macrophages

Excessive bone resorption mediated by osteoclasts may lead to the risk of various lytic bone diseases. In the present study, the effects of I‑BET151, a bromodomain and extra terminal domain protein inhibitor, on osteoclastogenesis in RAW264.7 cells and the underlying mechanism of this process was investigated. Cells were divided into 6 groups, including the control group, receptor activator of nuclear factor‑κB ligand (RANKL) group and 4 other groups containing RANKL and I‑BET151 at different concentrations. Tartrate‑resistant acid phosphatase (TRACP) staining was used to observe the effect of I‑BET151 on osteoclastogenesis and the number of TRACP positive multinucleated cells was calculated. Western blotting was used to evaluate the expression of tumor necrosis factor receptor associated factor (TRAF6), nuclear factor of activated T‑cells cytoplasmic 1 (NFATcl), transcription factor p65 (p65), nuclear factor of κ light polypeptide gene enhancer in B‑cells inhibitor‑α (IκB‑α), extracellular signal‑regulated kinase, Jun N‑terminal kinase (JNK) and p38. mRNA expression levels of osteoclast specific genes TRACP, matrix metalloproteinase‑9 (MMP9), cathepsin K (CtsK) and proto‑oncogene tyrosine‑protein kinase Src (c‑Src) were measured using the reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). TRACP staining results demonstrated that I‑BET151 inhibited osteoclastogenesis induced by RANKL and the inhibition was dose dependent. TRACP multinucleated positive cells were significantly decreased when treated with I‑BET151 compared with the RANKL group. The inhibitory effect on TRAF6 was significant when concentrations of 100 and 200 nM I‑BET151 were used, and NFATcl was significantly inhibited when a concentration of 200 nM was used compared with the RANKL group, in a dose-dependent manner. Nuclear translocation of p65 was significantly inhibited by I‑BET151 at all concentrations. The degradation of IκB‑α, and phosphorylation of JNK and p38 were also significantly inhibited by I‑BET151, with the exception of the expression of IκB‑α following treatment with 50 nM I‑BET151. The RT‑qPCR results revealed that osteoclast‑specific genes TRACP, MMP9, CtsK and c‑Src were all dose‑dependently inhibited by I‑BET151, except for CtsK. In conclusion, I‑BET151 may significantly suppress the osteoclastogenesis of RAW264.7 cells via the RANKL signaling pathway.

1,25(OH)2 vitamin D(3) contributes to osteoclast-like trans-differentiation of malignant plasma cells

1,25-dihydroxyvitamin D (1,25(OH)₂D) exerts pleiotropic effects including bone turnover and immune system regulation. It inhibits both T and B cell proliferation while decreasing the secretion of inflammatory cytokines and immunoglobulins. 1,25(OH)₂D also modulates monocyte-macrophage and osteoclast (OC) maturation. Since we have previously described that malignant plasma cells may trans-differentiate towards the myeloid lineage participating to skeletal devastation in multiple myeloma (MM), we here evaluated in vitro the role of 1,25(OH)₂D in this lineage switch. We investigated the gene and protein expression of vitamin D receptor (VDR) in MM cell lines. Thus, after cell treatment with 1,25(OH)₂D, we analyzed their morphology and the expression of myeloid and OC markers. Finally, we assessed their bone resorption property on calcium phosphate slices. All MM cells expressed VDR in nuclear and perinuclear sites. Treatment with 1,25(OH)₂D altered their morphology from round to fusiform, while inducing paxillin focalization. 1,25(OH)₂D administration also up-regulated myeloid and OC genes, including C/EBPα, RANK, M-CSFR and V-ATPase, whose promoters contain potential 1,25(OH)₂D responsive elements. Finally, 1,25(OH)₂D increased MM cell capability to generate pits of erosion on calcium phosphate discs. This data suggest that myeloma cells may undergo a functional trans-differentiation into OCs and, under appropriate experimental conditions, 1,25(OH)₂D triggers this lineage switch.

Utilizing BMP-2 muteins for treatment of multiple myeloma

Multiple myeloma (MM) represents a haematological cancer characterized by the pathological hyper proliferation of antibody-producing B-lymphocytes. Patients typically suffer from kidney malfunction and skeletal disorders. In the context of MM, the transforming growth factor β (TGFβ) member Activin A was recently identified as a promoter of both accompanying symptoms. Because studies have shown that bone morphogenetic protein (BMP)-2-mediated activities are counteracted by Activin A, we analysed whether BMP2, which also binds to the Activin A receptors ActRII and ActRIIB but activates the alternative SMAD-1/5/8 pathway, can be used to antagonize Activin A activities, such as in the context of MM. Therefore three BMP2 derivatives were generated with modified binding activities for the type II (ActRIIB) and/or type I receptor (BMPRIA) showing either increased or decreased BMP2 activity. In the context of MM these BMP2 muteins show two functionalities since they act as a) an anti-proliferative/apoptotic agent against neoplastic B-cells, b) as a bone-formation promoting growth factor. The molecular basis of both activities was shown in two different cellular models to clearly rely on the properties of the investigated BMP2 muteins to compete for the binding of Activin A to the Activin type II receptors. The experimental outcome suggests new therapeutic strategies using BMP2 variants in the treatment of MM-related pathologies.

Inhibition of miR-21 restores RANKL/OPG ratio in multiple myeloma-derived bone marrow stromal cells and impairs the resorbing activity of mature osteoclasts

miR-21 is an oncogenic microRNA (miRNA) with an emerging role as therapeutic target in human malignancies, including multiple myeloma (MM). Here we investigated whether miR-21 is involved in MM-related bone disease (BD). We found that miR-21 expression is dramatically enhanced, while osteoprotegerin (OPG) is strongly reduced, in bone marrow stromal cells (BMSCs) adherent to MM cells. On this basis, we validated the 3′UTR of OPG mRNA as miR-21 target. Constitutive miR-21 inhibition in lentiviral-transduced BMSCs adherent to MM cells restored OPG expression and secretion. Interestingly, miR-21 inhibition reduced RANKL production by BMSCs. Overexpression of protein inhibitor of activated STAT3 (PIAS3), which is a direct and validated target of miR-21, antagonized STAT3-mediated RANKL gene activation. Finally, we demonstrate that constitutive expression of miR-21 inhibitors in BMSCs restores RANKL/OPG balance and dramatically impairs the resorbing activity of mature osteoclasts. Taken together, our data provide proof-of-concept that miR-21 overexpression within MM-microenviroment plays a crucial role in bone resorption/apposition balance, supporting the design of innovative miR-21 inhibition-based strategies for MM-related BD.

Inhibition of Transforming Growth Factor-β Activation Diminishes Tumor Progression and Osteolytic Bone Disease in Mouse Models of Multiple Myeloma

Transforming growth factor (TGF)-β supports multiple myeloma progression and associated osteolytic bone disease. Conversion of latent TGF-β to its biologically active form is a major regulatory node controlling its activity. Thrombospondin1 (TSP1) binds and activates TGF-β. TSP1 is increased in myeloma, and TSP1-TGF-β activation inhibits osteoblast differentiation. We hypothesized that TSP1 regulates TGF-β activity in myeloma and that antagonism of the TSP1-TGF-β axis inhibits myeloma progression. Antagonists (LSKL peptide, SRI31277) derived from the LSKL sequence of latent TGF-β that block TSP1-TGF-β activation were used to determine the role of the TSP1-TGF-β pathway in mouse models of myeloma. TSP1 binds to human myeloma cells and activates TGF-β produced by cultured human and mouse myeloma cell lines. Antagonists delivered via osmotic pump in an intratibial severe combined immunodeficiency CAG myeloma model or in a systemic severe combined immunodeficiency CAG-heparanase model of aggressive myeloma reduced TGF-β signaling (phospho-Smad 2) in bone sections, tumor burden, mouse IL-6, and osteoclasts, increased osteoblast number, and inhibited bone destruction as measured by microcomputed tomography. SRI31277 reduced tumor burden in the immune competent 5TGM1 myeloma model. SRI31277 was as effective as dexamethasone or bortezomib, and SRI31277 combined with bortezomib showed greater tumor reduction than either agent alone. These studies validate TSP1-regulated TGF-β activation as a therapeutic strategy for targeted inhibition of TGF-β in myeloma.

Multiple myeloma mesenchymal stromal cells: Contribution to myeloma bone disease and therapeutics

Multiple myeloma is a hematological malignancy in which clonal plasma cells proliferate and accumulate within the bone marrow. The presence of osteolytic lesions due to increased osteoclast (OC) activity and suppressed osteoblast (OB) function is characteristic of the disease. The bone marrow mesenchymal stromal cells (MSCs) play a critical role in multiple myeloma pathophysiology, greatly promoting the growth, survival, drug resistance and migration of myeloma cells. Here, we specifically discuss on the relative contribution of MSCs to the pathophysiology of osteolytic lesions in light of the current knowledge of the biology of myeloma bone disease (MBD), together with the reported genomic, functional and gene expression differences between MSCs derived from myeloma patients (pMSCs) and their healthy counterparts (dMSCs). Being MSCs the progenitors of OBs, pMSCs primarily contribute to the pathogenesis of MBD because of their reduced osteogenic potential consequence of multiple OB inhibitory factors and direct interactions with myeloma cells in the bone marrow. Importantly, pMSCs also readily contribute to MBD by promoting OC formation and activity at various levels (i.e., increasing RANKL to OPG expression, augmenting secretion of activin A, uncoupling ephrinB2-EphB4 signaling, and through augmented production of Wnt5a), thus further contributing to OB/OC uncoupling in osteolytic lesions. In this review, we also look over main signaling pathways involved in the osteogenic differentiation of MSCs and/or OB activity, highlighting amenable therapeutic targets; in parallel, the reported activity of bone-anabolic agents (at preclinical or clinical stage) targeting those signaling pathways is commented.

Mesenchymal stem cell contact promotes CCN1 splicing and transcription in myeloma cells

CCN family member 1 (CCN1), also known as cysteine-rich angiogenic inducer 61 (CYR61), belongs to the extracellular matrix-associated CCN protein family. The diverse functions of these proteins include regulation of cell migration, adhesion, proliferation, differentiation and survival/apoptosis, induction of angiogenesis and cellular senescence. Their functions are partly overlapping, largely non-redundant, cell-type specific, and depend on the local microenvironment. To elucidate the role of CCN1 in the crosstalk between stromal cells and myeloma cells, we performed co-culture experiments with primary mesenchymal stem cells (MSC) and the interleukin-6 (IL-6)-dependent myeloma cell line INA-6. Here we show that INA-6 cells display increased transcription and induction of splicing of intron-retaining CCN1 pre-mRNA when cultured in contact with MSC. Protein analyses confirmed that INA-6 cells co-cultured with MSC show increased levels of CCN1 protein consistent with the existence of a pre-mature stop codon in intron 1 that abolishes translation of unspliced mRNA. Addition of recombinant CCN1-Fc protein to INA-6 cells was also found to induce splicing of CCN1 pre-mRNA in a concentration-dependent manner. Only full length CCN1-Fc was able to induce mRNA splicing of all introns, whereas truncated recombinant isoforms lacking domain 4 failed to induce intron splicing. Blocking RGD-dependent integrins on INA-6 cells resulted in an inhibition of these splicing events. These findings expand knowledge on splicing of the proangiogenic, matricellular factor CCN1 in the tumor microenvironment. We propose that contact with MSC-derived CCN1 leads to splicing and enhanced transcription of CCN1 which further contributes to the translation of angiogenic factor CCN1 in myeloma cells, supporting tumor viability and myeloma bone disease.

Preclinical activity of the oral proteasome inhibitor MLN9708 in Myeloma bone disease

PURPOSE

MLN9708 (ixazomib citrate), which hydrolyzes to pharmacologically active MLN2238 (ixazomib), is a next-generation proteasome inhibitor with demonstrated preclinical and clinical antimyeloma activity, but yet with an unknown effect on myeloma bone disease. Here, we investigated its bone anabolic and antiresorptive effects in the myeloma setting and in comparison with bortezomib in preclinical models.

EXPERIMENTAL DESIGN

The in vitro effect of MLN2238 was tested on osteoclasts and osteoclast precursors from healthy donors and patients with myeloma, and on osteoprogenitors derived from bone marrow mesenchymal stem cells also from both origins. We used an in vivo model of bone marrow-disseminated human myeloma to evaluate MLN2238 antimyeloma and bone activities.

RESULTS

Clinically achievable concentrations of MLN2238 markedly inhibited in vitro osteoclastogenesis and osteoclast resorption; these effects involved blockade of RANKL (receptor activator of NF-κB ligand)-induced NF-κB activation, F-actin ring disruption, and diminished expression of αVβ3 integrin. A similar range of MLN2238 concentrations promoted in vitro osteoblastogenesis and osteoblast activity (even in osteoprogenitors from patients with myeloma), partly mediated by activation of TCF/β-catenin signaling and upregulation of the IRE1 component of the unfolded protein response. In a mouse model of bone marrow-disseminated human multiple myeloma, orally administered MLN2238 was equally effective as bortezomib to control tumor burden and also provided a marked benefit in associated bone disease (sustained by both bone anabolic and anticatabolic activities).

CONCLUSION

Given favorable data on pharmacologic properties and emerging clinical safety profile of MLN9708, it is conceivable that this proteasome inhibitor may achieve bone beneficial effects in addition to its antimyeloma activity in patients with myeloma.

Combined composite osteofasciocutaneous fibular free flap and radial head arthroplasty for reconstruction of the elbow joint

Reconstruction of the radial head can be complicated in cases of wide resection, particularly in those cases including the proximal radial shaft. In such cases, radial head replacement may not be possible because of lack of adequate bone stock. Here, we report the use of a radial head prosthesis incorporated with a vascularized fibula for immediate anatomic restoration of the forearm and elbow. We present a case of a pathologic fracture non-union in the proximal radius in a 57-year-old female with a history of multiple myeloma. Non-operative management of the fracture was unsuccessful after chemotherapy and radiation. The proximal radius and radial head were resected and reconstructed with vascularized fibula graft in conjunction with immediate radial head prosthesis. The osteotomy site healed at 6-weeks and follow-up at 1 year showed good functional outcome. We feel that the use of this construct has definite promise and may be considered for reconstruction following resection of the proximal radius.

The Role of Denosumab for Prevention of Skeletal-Related Complications in Multiple Myeloma

OBJECTIVE

To evaluate the use of denosumab for the prevention of skeletal-related events (SREs) in patients with osteolytic lesions associated with multiple myeloma (MM).

DATA SOURCES

MEDLINE/Ovid (1946-April week 3, 2013), EMBASE (1980–2013 week 16), abstracts of the American Society of Clinical Oncology (1983-April 22, 2013), American Society of Hematology (2004-April 22, 2013), European Hematology Association (1994-April 22, 2013), and the European Society for Medical Oncology (1990-April 22, 2013) were searched using the terms denosumab and multiple myeloma.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials comparing the efficacy of denosumab with that of bisphosphonates in preventing or delaying SREs in patients with MM were included. Trials solely evaluating bone turnover markers were excluded. One Phase 2 trial, 1 Phase 3 trial, and 1 post hoc Phase 3 analysis were included.

DATA SYNTHESIS

A Phase 2 trial compared denosumab to bisphosphonate continuation in patients with elevated urinary N-telopeptide levels (uNTX) despite bisphosphonate therapy. Denosumab patients experienced fewer SREs; however, this was not statistically significant. A Phase 3 trial compared denosumab to zoledronic acid in patients with at least 1 osteolytic lesion. Denosumab delayed the time to a first SRE by 16% (median 20.6 vs 16.3 months; p = 0.0007 for noninferiority). Superiority of denosumab was not reached. A post hoc analysis revealed less favorable survival in MM patients treated with denosumab (HR 2.26; 95% CI 1.13–4.50). The incidence of overall adverse effects was similar between each group in both studies.

CONCLUSIONS

Denosumab may be an alternative for the prevention of SREs in patients with MM with deteriorating renal function. Because of the high cost of the drug, low percentage of MM patients in the available studies, and the potential for their decreased survival, use of denosumab should be limited.