Carfilzomib: a novel agent for multiple myeloma

Research strategies of small molecules as chemotherapeutics to overcome multiple myeloma resistance

Multiple myeloma (MM), a cancer of plasma cells, is the second most common hematological malignancy which is characterized by aberrant plasma cells infiltration in the bone marrow and complex heterogeneous cytogenetic abnormalities. Over the past two decades, novel treatment strategies such as proteasome inhibitors, immunomodulators, and monoclonal antibodies have significantly improved the relative survival rate of MM patients. However, the development of drug resistance results in the majority of MM patients suffering from relapse, limited treatment options and uncontrolled disease progression after relapse. There are urgent needs to develop and explore novel MM treatment strategies to overcome drug resistance and improve efficacy. Here, we review the recent small molecule therapeutic strategies for MM, and introduce potential new targets and corresponding modulators in detail. In addition, this paper also summarizes the progress of multi-target inhibitor therapy and protein degradation technology in the treatment of MM.

Pd(II) Complexes of Chiral Proline-Derived Ligands: Application for Dynamic Thermodynamic Resolution of α-Amino Acids and Their Antibacterial Activities

Novel type of Pd(II) complexes have been synthesized under operationally simple and convenient conditions and applied in the dynamic thermodynamic resolution of racemic N,C-unprotected α-amino acids. After rapid hydrolysis, these Pd(II) complexes produced the corresponding α-amino acids in satisfactory yields and enantioselectivities, accompanied by the recyclable proline-derived ligand. In addition, the method can be readily applied for S/R interconversion to obtain unnatural (R)-α-amino acids from readily available (S)-α-amino acids. Furthermore, biological assays showed that Pd(II) complexes (S,S)-3i and (S,S)-3m exhibited significant antibacterial activities similar to vancomycin, which may represent promising lead structures for further development of antibacterial agents.

Design and discovery of novel dipeptide boronic acid ester proteasome inhibitors, an oral slowly-released prodrug for the treatment of multiple myeloma

Multiple myeloma (MM), the second most common hematological malignancy, is a disease characterized by a clonal expansion of malignant plasma cells that accumulate in the bone marrow. Ixazomib citrate was the first commercially available oral proteasome inhibitor for the treatment of MM. However, it immediately hydrolyzed into the active form on exposure to aqueous solution and so it was a pseudo prodrug. Herein, a series of dipeptide boronic acid esters as novel oral proteasome inhibitors were designed, synthesized and biologically investigated for the inhibition of the β5 subunit of 20S proteasome. Based on the enzymatic results, structure-activity relationships (SAR) were discussed in detail. Some potent compounds were further evaluated to inhibit the proliferation of MM cell line RPMI-8226. The results showed that some compounds were active against RPMI-8226 with IC₅₀ values of less than 10 nM. The solution stability showed that ixazomib citrate was completely hydrolyzed to its active form ixazomib within 2 min in the simulated gastric juice. However, among the screened compounds, prodrug 18u was stable enough in simulated gastric juice and simulated intestinal juice, and its hydrolysis rate was 59.7% and 3.6% after 2 h, respectively. In addition, 18u exhibited good microsome stabilities and pharmacokinetic properties and displayed strong antiproliferative activity against the RPMI-8226 cell line (5.6 nM). Furthermore, compound 18u exhibited strong in vivo anticancer efficacy in human MM (RPMI-8226) xenograft mouse model.

Cu(II) Complexes with Proline-Derived Schiff Base Ligand: Chemical Resolution of N,C-Unprotected α-Amino Acids and Their Antibacterial Activity

An operationally simple and convenient resolution method via Cu(II) complexes was reported, efficiently providing valuable enantiopure N,C-unprotected α-amino acids. This protocol features synthetically attractive yields and a stereochemical outcome, using a recyclable Schiff base ligand and inexpensive easily accessible metal copper salts. These novel Cu(II) complexes can be obtained in an enantiopure state by means of column chromatography or recrystallization. Furthermore, all the Cu(II) complexes were evaluated for their antibacterial activities. Among them, complexes (S,2S)-3a, (S,2S)-3g, and (S,2S)-3o showed significant antibacterial activities against Staphylococcus aureus Mu50. Further biological evaluation indicated that they were effective against most of Gram-positive bacteria. It is the first study on the biological activities of transition metal complexes with this type of proline-derived Schiff base ligand.

Carfilzomib: A Promising Proteasome Inhibitor for the Treatment of Relapsed and Refractory Multiple Myeloma

The proteasome is crucial for the degradation of intracellular proteins and plays an important role in mediating a number of cell survival and progression events by controlling the levels of key regulatory proteins such as cyclins and caspases in both normal and tumor cells. However, compared to normal cells, cancer cells are more dependent on the ubiquitin proteasome pathway (UPP) due to the accumulation of proteins in response to uncontrolled gene transcription, allowing proteasome to become a potent therapeutic target for human cancers such as multiple myeloma (MM). Up to date, three proteasome inhibitors namely bortezomib (2003), carfilzomib (2012) and ixazomib (2015) have been approved by the US Food and Drug Administration (FDA) for the treatment of patients with relapsed and/or refractory MM. This review mainly focuses on the biochemical properties, mechanism of action, toxicity profile and pivotal clinical trials related to carfilzomib, a second-generation proteasome inhibitor that binds irreversibly with proteasome to overcome the major toxicities and resistance associated with bortezomib.

Cellular Responses to Proteasome Inhibition: Molecular Mechanisms and Beyond

Proteasome inhibitors have been actively tested as potential anticancer drugs and in the treatment of inflammatory and autoimmune diseases. Unfortunately, cells adapt to survive in the presence of proteasome inhibitors activating a variety of cell responses that explain why these therapies have not fulfilled their expected results. In addition, all proteasome inhibitors tested and approved by the FDA have caused a variety of side effects in humans. Here, we describe the different types of proteasome complexes found within cells and the variety of regulators proteins that can modulate their activities, including those that are upregulated in the context of inflammatory processes. We also summarize the adaptive cellular responses activated during proteasome inhibition with special emphasis on the activation of the Autophagic-Lysosomal Pathway (ALP), proteaphagy, p62/SQSTM1 enriched-inclusion bodies, and proteasome biogenesis dependent on Nrf1 and Nrf2 transcription factors. Moreover, we discuss the role of IRE1 and PERK sensors in ALP activation during ER stress and the involvement of two deubiquitinases, Rpn11 and USP14, in these processes. Finally, we discuss the aspects that should be currently considered in the development of novel strategies that use proteasome activity as a therapeutic target for the treatment of human diseases.

Next-generation proteasome inhibitors for cancer therapy

Over 2 decades ago, the proteasome was considered a risky or even untenable therapeutic target. Today, proteasome inhibitors are a mainstay in the treatment of multiple myeloma (MM) and have sales in excess of 3 billion US dollars annually. More importantly, the availability of proteasome inhibitors has greatly improved the survival and quality of life for patients with MM. Despite the remarkable success of proteasome inhibitor therapies to date, the potential for improvement remains, and the development and optimal use of proteasome inhibitors as anticancer agents continues to be an active area of research. In this review, we briefly discuss the features and limitations of the 3 proteasome inhibitor drugs currently used in the clinic and provide an update on current efforts to develop next-generation proteasome inhibitors with the potential to overcome the limitations of existing proteasome inhibitor drugs.

Tethered polymer nanoassemblies for sustained carfilzomib release and prolonged suppression of proteasome activity

AIM

Proteasome inhibitors, such as carfilzomib (CFZ), have shown potential to treat various types of cancers in preclinical models, but clinical applications are limited likely due to formulation and delivery issues. Results & methodology: Tethered polymer nanoassemblies (TNAs) were synthesized by tethering hydrophilic polymers and hydrophobic groups to charged polymer scaffolds, and then end-capping remaining amines on scaffold. Drug entrapment and drug release half-lives increased as charge was removed from scaffold. TNAs with sustained CFZ release maintained drug efficacy after preincubation and increased duration of proteasome inhibition in cancer cells compared with free CFZ.

CONCLUSION

TNAs fine-tuned CFZ release as charge was removed from polymer scaffold, which allowed for sustained proteasome inhibition in cancer cells and potentially enhanced anticancer efficacy.

Drug Synergism of Proteasome Inhibitors and Mitotane by Complementary Activation of ER Stress in Adrenocortical Carcinoma Cells

Mitotane is the only drug approved for treatment of the orphan disease adrenocortical carcinoma (ACC) and was recently shown to be the first clinically used drug acting through endoplasmic reticulum (ER)-stress induced by toxic lipids. Since mitotane has limited clinical activity as monotherapy, we here study the potential of activating ER-stress through alternative pathways. The single reliable NCI-H295 cell culture model for ACC was used to study the impact MG132, bortezomib (BTZ) and carfilzomib (CFZ) on mRNA and protein expression of ER-stress markers, cell viability and steroid hormone secretion. We found all proteasome inhibitors alone to trigger expression of mRNA (spliced X-box protein 1, XBP1) and protein markers indicative of the inositol-requiring enzyme 1 (IRE1) dependent pathway of ER-stress but not phosphorylation of eukaryotic initiation factor 2α (eIF2α), a marker of the PRKR-like endoplasmic reticulum kinase (PERK)-dependent pathway. Whereas mitotane alone activated both pathways, combination of BTZ and CFZ with low-dose mitotane blocked mitotane-induced eIF2α phosphorylation but increased XBP1-mRNA splicing indicating that proteasome inhibitors can commit signalling towards a single ER-stress pathway in ACC cells. By applying the median effect model of drug combinations using cell viability as a read out, we determined significant drug synergism between mitotane and both BTZ and CFZ. In conclusion, combination of mitotane with activators of ER-stress through the unfolded protein response is synergistic in an ACC cell culture model. Since proteasome inhibitors are readily available clinically, they are attractive candidates to study for ACC treatment in clinical trials in combination with mitotane.

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Carfilzomib (CFZ) is a second-generation proteasome inhibitor that is Food and Drug Administration and European Commission approved for the treatment of relapsed or refractory multiple myeloma. CFZ is an epoxomicin derivative with an epoxyketone electrophilic warhead that irreversibly adducts the catalytic threonine residue of the β5 subunit of the proteasome. Although CFZ produces a highly potent, sustained inactivation of the proteasome, the electrophilic nature of the drug could potentially produce off-target protein adduction. To address this possibility, we synthesized an alkynyl analog of CFZ and investigated protein adduction by this analog in HepG2 cells. Using click chemistry coupled with streptavidin based IP and shotgun tandem mass spectrometry (MS/MS), we identified two off-target proteins, cytochrome P450 27A1 (CYP27A1) and glutathione S-transferase omega 1 (GSTO1), as targets of the alkynyl CFZ probe. We confirmed the adduction of CYP27A1 and GSTO1 by streptavidin capture and immunoblotting methodology and then site-specifically mapped the adducts with targeted MS/MS methods. Although CFZ adduction of CYP27A1 and GSTO1 in vitro decreased the activities of these enzymes, the small fraction of these proteins modified by CFZ in intact cells should limit the impact of these off-target modifications. The data support the high selectivity of CFZ for covalent modification of its therapeutic targets, despite the presence of a reactive electrophile. The approach we describe offers a generalizable method to evaluate the safety profile of covalent protein-modifying therapeutics.

DNA repair of myeloma plasma cells correlates with clinical outcome: the effect of the nonhomologous end-joining inhibitor SCR7

DNA repair activity of malignant cells seems to influence therapeutic outcome and patients' survival. Herein, we investigated the mechanistic basis for the link between DNA repair efficiency and response to antimyeloma therapy. Nucleotide excision repair (NER), interstrand cross-links repair (ICL/R), double-strand breaks repair (DSB/R), and chromatin structure were evaluated in multiple myeloma (MM) cell lines (melphalan-sensitive RPMI8226; melphalan-resistant LR5) and bone marrow plasma cells (BMPCs) from MM patients who responded (n = 17) or did not respond (n = 9) to subsequent melphalan therapy. The effect of DSB/R inhibition was also evaluated. Responders' BMPCs showed slower rates of NER and DSB/R (P <0022), similar rates of ICL/R, and more condensed chromatin structure compared with nonresponders. Moreover, apoptosis rates of BMPCs were inversely correlated with individual DNA repair efficiency and were higher in responders' cells compared with those of nonresponders (P = .0011). Similarly, RPMI8226 cells showed slower rates of NER and DSB/R, comparable rates of ICL/R, more condensed chromatin structure, and higher sensitivity than LR5 cells. Interestingly, cotreatment of BMPCs or cell lines with DSB/R inhibitors significantly reduced the rates of DSB/R and increased melphalan sensitivity of the cells, with the nonhomologous end-joining inhibitor SCR7 showing the strongest effect. Together, responders' BMPCs are characterized by lower efficiencies of NER and DSB/R mechanisms, resulting in higher accumulation of the extremely cytotoxic ICLs and DSBs lesions, which in turn triggers the induction of the apoptotic pathway. Moreover, the enhancement of melphalan cytotoxicity by DSB/R inhibition offers a promising strategy toward improvement of existing antimyeloma regimens.

Final overall survival results of a randomized trial comparing bortezomib plus pegylated liposomal doxorubicin with bortezomib alone in patients with relapsed or refractory multiple myeloma

BACKGROUND

Previous results from an interim analysis of an open-label, randomized, phase 3 study demonstrated that bortezomib combined with pegylated liposomal doxorubicin (PLD) was superior to bortezomib monotherapy in patients with relapsed/refractory multiple myeloma who had previously received one or more lines of therapy. Protocol-defined final survival data from that study are provided here.

METHODS

Patients were randomized (1:1) to receive either bortezomib alone (1.3 mg/m(2) intravenously on days 1, 4, 8, and 11 of every 21-day cycle) or bortezomib-PLD (bortezomib plus PLD 30 mg/m(2) intravenously on day 4). The primary endpoint was the time to progression. Secondary efficacy endpoints included overall survival (OS), progression-free survival, and the overall response rate.

RESULTS

In total, 646 patients (bortezomib-PLD, n = 324; bortezomib alone, n = 322) were randomized between December, 2004, and March, 2006. On the clinical cutoff date (May 16, 2014) for the final survival analysis, at a median follow-up of 103 months, 79% of patients had died (bortezomib-PLD group: 253 of 324 patients; 78%; bortezomib alone group: 257 of 322 patients; 80%). The median OS in the bortezomib-PLD group was 33 months (95% confidence interval [CI], 28.9-37.1) versus 30.8 months (95% CI, 25.2-36.5) in the bortezomib alone group (hazard ratio, 1.047; 95% CI, 0.879-1.246; P = .6068). Salvage therapies included conventional and novel drugs, which were well balanced between the two treatment groups.

CONCLUSIONS

Despite inducing a superior time to progression, long-term follow-up revealed that PLD-bortezomib did not improve OS compared with bortezomib alone in patients with relapsed/refractory multiple myeloma. The inability to sustain the early observed survival advantage may have been caused by the effects of subsequent lines of therapy, and underscores the need for long-term follow-up of phase 3 trials while recognizing the challenge of having adequate power to detect long-term differences in OS. Cancer 2016;122:2050-6. © 2016 American Cancer Society.

Carfilzomib-induced cardiotoxicity mitigated by dexrazoxane through inhibition of hypertrophic gene expression and oxidative stress in rats

Carfilzomib (CFZ) is an inhibitor of proteasome that is generally used in the treatment of multiple myeloma but due to its cardiotoxicity clinical use may be limited. Dexrazoxane (DZR), an inhibitor of topoisomerase-II, prevents cardiac damage by reducing the formation of reactive oxygen species and hypertrophic gene expression. This study evaluated the protective effect of DZR on CFZ-induced cardiotoxicity. Thirty-two male Albino rats were randomly divided into four groups (n = 8). Group I received DMSO, Group II received CFZ (4 mg/kg, intraperitoneally [i.p.]) twice weekly up to day 16, Group III received DZR (20 mg/kg, i.p.) for 16 days and CFZ twice weekly for 16, Group IV received DZR (40 mg/kg, i.p.) for 16 days and CFZ twice weekly for 16. CFZ-induced cardiotoxicity was assessed by hematological, biochemical, mRNA expression, oxidative stress and histopathological studies. CFZ-induced significant changes have been observed in blood parameters including red blood cells, white blood cells, hemoglobin and hematocrit concentrations which were associated with increase in cardiac enzymes markers like creatine kinase (CK), CK-MB and lactate dehydrogenase. Treatment with DZR reversed the hematological statistics and the biochemical markers of CFZ-induced cardiotoxicity. Furthermore, DZR also attenuated the effects of CFZ-induced toxic effect on redox markers such as malondialdehyde and reduced glutathione. Above findings were further confirmed by beta-myosin heavy chain (β-MHC) and alpha-MHC (α-MHC) gene expression. Histopathological reports suggested that DZR ameliorates CFZ-induced changes in cardiac cellular architecture in rats. These results confirm that DZR protects heart from CFZ-induced cardiotoxicity.

Natural Products as a Vital Source for the Discovery of Cancer Chemotherapeutic and Chemopreventive Agents

Throughout history, natural products have played a dominant role in the treatment of human ailments. For example, the legendary discovery of penicillin transformed global existence. Presently, natural products comprise a large portion of current-day pharmaceutical agents, most notably in the area of cancer therapy. Examples include Taxol, vinblastine, and camptothecin. These structurally unique agents function by novel mechanisms of action; isolation from natural sources is the only plausible method that could have led to their discovery. In addition to terrestrial plants as sources for starting materials, the marine environment (e.g., ecteinascidin 743, halichondrin B, and dolastatins), microbes (e.g., bleomycin, doxorubicin, and staurosporin), and slime molds (e.g., epothilone B) have yielded remarkable cancer chemotherapeutic agents. Irrespective of these advances, cancer remains a leading cause of death worldwide. Undoubtedly, the prevention of human cancer is highly preferable to treatment. Cancer chemoprevention, the use of vaccines or pharmaceutical agents to inhibit, retard, or reverse the process of carcinogenesis, is another important approach for easing this formidable public health burden. Similar to cancer chemotherapeutic agents, natural products play an important role in this field. There are many examples, including dietary phytochemicals such as sulforaphane and phenethyl isothiocyanate (cruciferous vegetables) and resveratrol (grapes and grape products). Overall, natural product research is a powerful approach for discovering biologically active compounds with unique structures and mechanisms of action. Given the unfathomable diversity of nature, it is reasonable to suggest that chemical leads can be generated that are capable of interacting with most or possibly all therapeutic targets.

Misfolded proteins: from little villains to little helpers in the fight against cancer

The application of cytostatic drugs targeting the high proliferation rates of cancer cells is currently the most commonly used treatment option in cancer chemotherapy. However, severe side effects and resistance mechanisms may occur as a result of such treatment, possibly limiting the therapeutic efficacy of these agents. In recent years, several therapeutic strategies have been developed that aim at targeting not the genomic integrity and replication machinery of cancer cells but instead their protein homeostasis. During malignant transformation, the cancer cell proteome develops vast aberrations in the expression of mutated proteins, oncoproteins, drug- and apoptosis-resistance proteins, etc. A complex network of protein quality-control mechanisms, including chaperoning by heat shock proteins (HSPs), not only is essential for maintaining the extravagant proteomic lifestyle of cancer cells but also represents an ideal cancer-specific target to be tackled. Furthermore, the high rate of protein synthesis and turnover in certain types of cancer cells can be specifically directed by interfering with the proteasomal and autophagosomal protein recycling and degradation machinery, as evidenced by the clinical application of proteasome inhibitors. Since proteins with loss of their native conformation are prone to unspecific aggregations and have proved to be detrimental to normal cellular function, specific induction of misfolded proteins by HSP inhibitors, proteasome inhibitors, hyperthermia, or inducers of endoplasmic reticulum stress represents a new method of cancer cell killing exploitable for therapeutic purposes. This review describes drugs - approved, repurposed, or under investigation - that can be used to accumulate misfolded proteins in cancer cells, and particularly focuses on the molecular aspects that lead to the cytotoxicity of misfolded proteins in cancer cells.

Chromatin structure, transcriptional activity and DNA repair efficiency affect the outcome of chemotherapy in multiple myeloma

Background:

Melphalan is one of the most active chemotherapeutic agents in the treatment of multiple myeloma (MM). However, the mechanism underlying differential patient responses to melphalan therapy is unknown.

Methods:

Chromatin structure, transcriptional activity and DNA damage response signals were examined following ex vivo treatment with melphalan of both malignant bone marrow plasma cells (BMPCs) and peripheral blood mononuclear cells (PBMCs) of MM patients, responders (n=57) or non-responders (n=28) to melphalan therapy. PBMCs from healthy controls (n=25) were also included in the study.

Results:

In both BMPCs and PBMCs, the local chromatin looseness, transcriptional activity and repair efficiency of the transcribed strand (TS) were significantly higher in non-responders than in responders and lowest in healthy controls (all P<0.05). Moreover, we found that melphalan-induced apoptosis inversely correlated with the repair efficiency of the TS, with the duration of the inhibition of mRNA synthesis, phosphorylation of p53 at serine 15 and apoptosis rates being higher in responders than in non-responders (all P<0.001).

Conclusions:

Our findings provide a mechanistic basis for the link between DNA repair efficiency and response to melphalan therapy. Interestingly, the observation of these phenomena in PBMCs provides a novel approach for the prediction of response to anti-myeloma therapy.

An analysis of the safety profile of proteasome inhibitors for treating various cancers

INTRODUCTION

Emerging evidence demonstrates that the ubiquitin-proteasome pathway is a promising target for cancer therapy. Bortezomib (Velcade) exhibits great efficacy against multiple myeloma (MM) since the first clinical application. However, there are still several limitations associated with the use of bortezomib, including severe toxicities. To overcome bortezomib's shortcomings and to improve its safety profile, several second-generation proteasome inhibitors, for example, carfilzomib, ixazomib, oprozomib and marizomib, have been developed and currently tested in various clinical trials.

AREAS COVERED

A literature search was carried out using PubMed and Google Scholar. The activity and safety profiling of proteasome inhibitors in treatment of various cancers were reviewed.

EXPERT OPINION

Bortezomib, as a single or in combination therapy, demonstrates efficacy against MM or other hematological malignancies in clinical settings. However, it encounters two major problems, the acquired resistance and the severe side effects. Future direction in bortezomib-based therapy should focus on how to increase or retain its efficacy but improve its safety profile through, for example, rational combination therapies. Second-generation proteasome inhibitors have shown benefits in both overcoming bortezomib resistance and reducing related side effects, although these encouraging results should be further confirmed in a larger clinic population.

Incidence and management of adverse events in patients with relapsed and/or refractory multiple myeloma receiving single-agent carfilzomib

Carfilzomib, a selective proteasome inhibitor approved in the USA in 2012, is a single agent for relapsed and refractory multiple myeloma. Carfilzomib is administered as a 2–10-minute infusion on days 1, 2, 8, 9, 15, and 16 of a 28-day cycle at a starting dose of 20 mg/m² for cycle 1 and a target dose of 27 mg/m² thereafter. In the pivotal Phase II study (PX-171-003-A1), carfilzomib 20/27 mg/m² provided durable responses in a heavily pretreated population with relapsed and refractory multiple myeloma (n=266), with an overall response rate of 22.9% and a median duration of response of 7.8 months. In an integrated safety analysis of four Phase II studies, common adverse events (32.7%–55.5%) included fatigue, anemia, nausea, thrombocytopenia, dyspnea, and diarrhea. Grade 3/4 adverse events were generally hematologic and included thrombocytopenia (23.4%), anemia (22.4%), and lymphopenia (18.1%). Serious adverse events included pneumonia (9.9%), acute renal failure (4.2%), pyrexia (3.4%), and congestive heart failure (3.4%). New or worsening peripheral neuropathy was infrequent (13.9% overall, 1.3% grade 3, no grade 4). This review discusses findings of the integrated safety analysis and provides practical experience from a single institution in managing treatment-related and disease-related adverse events. Individualized treatment with proactive management of side effects and complications allows patients with advanced multiple myeloma to remain on carfilzomib for extended periods.

Effectiveness of targeted therapy as monotherapy or combined therapy in patients with relapsed or refractory multiple myeloma: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review was to evaluate the efficacy and safety of targeted agents used as monotherapy or combined therapy in patients with relapsed/refractory multiple myeloma (MM).

METHODS

The systematic literature search was conducted in PubMed, Embase, Cochrane Library till 27 May 2013.

RESULTS

Four randomized controlled trials were included. The meta-analysis showed that combined therapy significantly improved progression-free survival compared with monotherapy (P < 0.05). However, there was not a significant difference between monotherapy and combined therapy in overall survival (P > 0.05). The combined therapy also significantly increased the risk of serious adverse events and grade 3/4 AEs compared to monotherapy (P < 0.05). Overall, the results of comparisons between monotherapy and combined therapy in individual trials were differentiated, and some combinations were not more effective than monotherapy (bortezomib plub bevacizumab vs. bortezomib and thalidomide plus INFα vs. thalidomide) which emphasizes the role of individualized therapy in relapsed/refractory MM especially in the elderly or patients with significant comorbidities.

CONCLUSIONS

The results of this meta-analysis showed that combined therapy is superior to monotherapy only in some end points and it is less tolerated in patients with relapsed/refractory MM. Thus, the overall superiority of complex therapy to monotherapy depends on the combination of the targeted agents.

Carfilzomib-associated tumor lysis syndrome

Multiple myeloma is the second most common type of hematologic malignancy. It is a B-cell malignancy that affects the bone marrow and often results in thrombocytopenia as well as renal dysfunction. Treatment options range from oral and intravenous chemotherapy to bone marrow transplantation and supportive care. Carfilzomib was approved by the U.S. Food and Drug Administration in 2012 as a treatment option for patients with refractory multiple myeloma who have received at least two previous therapies and have demonstrated recent disease progression. According to the product labeling, the frequency of tumor lysis syndrome (TLS) is less than 1% in patients treated with carfilzomib. To our knowledge, no postmarketing events of TLS have been reported or published. We describe a 55-year-old man with relapsed multiple myeloma who developed a case of TLS that occurred after he received his first two doses of carfilzomib therapy on days 1 and 2; he also had chronic kidney disease secondary to his neoplastic disease. Beginning on day 4, his uric acid levels spiked to critical levels, prompting the use of rasburicase, which returned the levels to within normal limits. His phosphorus and creatinine levels increased during days 5 and 6. On day 8, the patient died, likely due to a combination of disease progression and the adverse effects of treatment. Use of the Naranjo adverse drug reaction probability scale indicated a probable relationship (score of 6) between the patient's development of TLS and carfilzomib therapy. The Hill criteria were used as a secondary measure to ensure causality, which also suggested a link between the patient's development of TLS and the administration of carfilzomib. This case report shows that even the most unlikely of adverse events may occur with medications, especially in the case of a new or recently approved medication. Caution must be taken when deciding to treat and when choosing hydration and premedications with regard to biologic and chemotherapeutic medications. In this case, additional hydration may have been considered. Although given the extent of the adverse reaction combined with the patient's underlying renal dysfunction, extra fluid may or may not have proven beneficial. The use of prophylactic rasburicase or allopurinol could have been considered, but these measures are not typically used with multiple myeloma due to the low incidence of TLS. All things considered, this unlikely adverse reaction may occur in certain patients. If other cases such as this occur, it may be advisable to use TLS prophylaxis in the future in certain patient populations, including those with renal dysfunction or worsening disease states.