Second-generation Proteasome Inhibitor Carfilzomib Research Articles

Functional Investigation of IGF1R Mutations in Multiple Myeloma.

High expression of the receptor tyrosine kinase (RTK) insulin-like growth factor-1 receptor (IGF1R) and RTK mutations are associated with high-risk/worse prognosis in multiple myeloma (MM). Combining the pIGF1R/pINSR inhibitor linsitinib with the proteasome inhibitor (PI) bortezomib seemed promising in a clinical trial, but IGF1R expression was not associated with therapy response. Because the oncogenic impact of IGF1R mutations is so far unknown, we investigated the functional impact of IGF1R mutations on survival signaling, viability/proliferation and survival response to therapy. We transfected four human myeloma cell lines (HMCLs) with IGF1RWT, IGF1RD1146N and IGF1RN1129S (Sleeping Beauty), generated CRISPR-Cas9 IGF1R knockouts in the HMCLs U-266 (IGF1RWT) and L-363 (IGF1RD1146N) and tested the anti-MM activity of linsitinib alone and in combination with the second-generation PI carfilzomib in seven HMCLs. IGF1R knockout entailed reduced proliferation. Upon IGF1R overexpression, survival signaling was moderately increased in all HCMLs and slightly affected by IGF1RN1129S in one HMCL, whereby the viability remained unaffected. Expression of IGF1RD1146N reduced pIGF1R-Y1135, especially under serum reduction, but did not impact downstream signaling. Linsitinib and carfilzomib showed enhanced anti-myeloma activity in six out of seven HMCL irrespective of the IGF1R mutation status. In conclusion, IGF1R mutations can impact IGF1R activation and/or downstream signaling, and a combination of linsitinib with carfilzomib might be a suitable therapeutic approach for MM patients potentially responsive to IGF1R blockade.

Synergistic Anti-Cancer Effects of Second-Generation Proteasome Inhibitor Carfilzomib with Doxorubicin and Dexamethasone Via p53-Mediated Apoptosis in Pre-B Acute Lymphoblastic Leukemia Cells

Background: The ubiquitin-proteasome system (UPS) plays a crucial role in regulating the levels and functions of a large number of proteins in the cell, which are important for cancer cell growth and survival. The proteasome is highly activated in B-cell precursor acute lymphoblastic leukemia (BCP-ALL), which is the most common malignancy in children. The attempt to inhibit proteasome as a therapeutic strategy has been successful for some malignancies.
 Materials and Methods: In this experimental study, human BCP-ALL cell lines NALM-6 and SUP-B15 were treated with carfilzomib with and without the chemotherapeutic agents. The XTT assay evaluated the viability of the cells. Cell cycle analysis and apoptosis assay were assessed by flow cytometry. RQ-PCR and western blotting evaluated the expression of pro-/anti-apoptotic signals. A drug combination study for synergistic or additive effects of carfilzomib with doxorubicin or dexamethasone was performed.
 Results: We observed that carfilzomib alone induced G2/M cell cycle arrest and caspase-dependent apoptosis in the human BCP-ALL cells (NALM-6 and SUP-B15). Gene and protein expression analysis indicated the upregulation of pro-apoptotic as well as downregulation of the cell survival and proliferative signals (P-value<0.05). The synergy of carfilzomib with doxorubicin or dexamethasone was revealed in BCP-ALL cells.
 Conclusion: Our results indicated that proteasome inhibition induces p53-mediated apoptosis in BCP-ALL cells. Since carfilzomib has a synergistic effect with anti-leukemic agents doxorubicin and dexamethasone in BCP-ALL cells, this combined-modality approach might be befitting for patients who do not respond well to conventional chemotherapy.

The cytotoxic activity of carfilzomib together with nelfinavir is superior to the bortezomib/nelfinavir combination in non-small cell lung carcinoma

Chemotherapy resistance is still a major problem in the treatment of patients with non-small-cell-lung carcinoma (NSCLC), and novel concepts for the induction of cytotoxicity in NSCLC are highly warranted. Proteotoxicity, the induction of cytotoxicity by targeting the ubiquitin proteasome system, represents an appealing innovative strategy. The combination of the proteasome inhibitor bortezomib (BTZ) and the proteotoxic stress-inducing HIV drug nelfinavir (NFV) synergistically induces proteotoxicity and shows encouraging preclinical efficacy in NSCLC. The second-generation proteasome inhibitor carfilzomib (CFZ) is superior to BTZ and overcomes BTZ resistance in multiple myeloma patients. Here, we show that CFZ together with NFV is superior to the BTZ + NFV combination in inducing endoplasmic reticulum stress and proteotoxicity through the accumulation of excess proteasomal substrate protein in NSCLC in vitro and ex vivo. Interestingly, NFV increases the intracellular availability of CFZ through inhibition of CFZ export from NSCLC cells that express multidrug resistance (MDR) protein. Combining CFZ with NFV may therefore represent a future treatment option for NSCLC, which warrants further investigation.

Combination of Second-Generation Proteasome Inhibitor Carfilzomib with Bortezomib in Four Different Breast Cancer Cell Lines.

Proteasome inhibitors target different pathways in cells and therefore are promising drugs in cancer therapy. The use of these inhibitors is approved mainly in hematological cancers, and recently many clinical trials and preclinical studies have been conducted on efficacy in solid tumors. Carfilzomib is a second-generation inhibitor and was developed to decrease the side effects of bortezomib. Although there are many valid therapies for breast cancer, resistance and recurrence are inevitable in many cases and the proteasomal system plays an important role in related pathways. This study is a preliminary work to evaluate the combined effects of bortezomib and carfilzomib in four different breast cancer cells. MDA-MB-231, MCF-7, UACC-2087, and SKBR-3 cell lines were used. Cell viability was determined using bortezomib and carfilzomib alone and in combination. Combination effect values were determined using the Chou- Talalay method. Apoptosis, proteasome activity, cleaved PARP, and HSP70 expressions were analyzed in the determined doses. The response to the combination of the two inhibitors was different in four cell lines. Apoptosis was significantly higher in combination groups compared to carfilzomib in three cell lines except for SKBR-3, and higher in the combination group compared to bortezomib only in UACC-2087. Combination decreased cleaved PARP levels in MDA-MB-231 and MCF-7 and increased SKBR-3 compared to bortezomib. HSP70 levels decreased in combination with UACC-2087 and SKBR-3 compared to carfilzomib. Taken together, the combination of the two inhibitors was more apoptotic compared to carfilzomib and apoptosis was higher only in UACC-2087 compared to bortezomib. This apoptosis data can not be directly correlated to the degree of proteasome inhibition, PARP cleavage, and HSP70 response.

Autologous Stem Cell Transplantation in Multiple Myeloma: Where Are We and Where Do We Want to Go?

The introduction of high-dose therapy in the 1990s as well as the development of drugs such as thalidomide, lenalidomide, and bortezomib in the 2000s led to an impressive improvement in outcome of patients with multiple myeloma (MM) eligible for autologous stem cell transplantation (ASCT). Clinical trials conducted in the first ten years of the twenty-first century established as standard therapy for these patients a therapeutic approach including induction, single or double ASCT, consolidation, and maintenance therapy. More recently, incorporating second-generation proteasome inhibitors carfilzomib and monoclonal antibody daratumumab into each phase of treatment significantly improved the efficacy of ASCT in terms of measurable residual disease (MRD) negativity, Progression Free Survival (PFS), and Overall Survival (OS). The availability of techniques such as multiparameter flow cytometry (MFC) and next-generation sequencing (NGS) for MRD assessment allowed the design of MRD-based response-adjusted trials that will define, in particular, the role of consolidation and maintenance therapies. In this review, we will provide an overview of the most recent evidence and the future prospects of ASCT in MM patients.

Demographic and Clinical Characteristics of Multiple Myeloma (MM) Patients Treated with Carfilzomib-Based Regimens in a Real World Setting

Introduction:The second-generation proteasome inhibitor carfilzomib (K) was initially approved in the United States (US) in 2012 as a single agent for treatment of patients with MM who received ≥2 prior therapies, including bortezomib and an immunomodulatory agent. K was subsequently approved in combination with lenalidomide and dexamethasone (KRd; in 2015) or with dexamethasone (Kd; in 2016) for treatment of patients with relapsed or refractory MM who received 1-3 prior lines of therapy. Due to the many regimens and dosing options available, we evaluated patient characteristics according to regimen and line of therapy (LOT). This study describes the demographic and disease characteristics of patients receiving K-based regimens in clinical practice since its approval.Methods:Data analyzed were from a database of oncology electronic health records (EHR) contained in Oncology Services Comprehensive Electronic Records (OSCER) database, generated by Flatiron Health (New York, NY, April 30, 2016). OSCER represents a longitudinal, demographically and geographically diverse database containing data from over 265 cancer clinics representing over 1.7 million active patients treated at community-based hematology/oncology practices and from three academic centers in the US. Patients identified were aged ≥18 years, diagnosed with MM (ICD9: 203.x; ICD-10: C90.x) and initiated K-based therapy in the years 2012-2016. Patient demographic and disease characteristics were identified, as well as the year of therapy initiation, LOT (1-4), and all treatment regimens received. Five treatment regimens were identified: four regimens based on K dosed at 27 mg/m2 twice weekly (Kd27, Kd27 + lenalidomide [KRd], Kd27 + pomalidomide [KPd], and Kd27 + cyclophosphamide [KCyd]) and Kd with K dosed at 56 mg/m2 (Kd56) twice weekly, as well as any other treatment combination with K. All regimens were assumed to contain dexamethasone.Results:Out of a total of 30,143 MM patients, 2202 K-treated patients were identified. Among K-treated patients, 40.6%, 36.7%, and 22.6% were aged ≤65 years, >65 and ≤75 years, and >75 years of age at index data, respectively, with 58.3% male and 65.7% white. Detailed results of the patients' clinical characteristics will also be presented. Kd27, the first approved K-containing regimen, was the most common K-based treatment regimen across all years, but the proportion of use relative to other K-based regimens was highest in 2012-2014 (61.7%, 51.3%, and 47.7% of patients, respectively), and decreased over time as other K regimens became available (39.1% and 29.5% in 2015 and 2016, respectively). KRd was the second-most common K regimen, representing 24.4% and 25.3% of K regimens in 2015 (year of approval) and 2016, respectively. Kd27 and KRd were also the most common treatment regimens across LOT (see figure). Use of Kd56 grew over time; in 2016 it accounted for 6.5%, 7.0%, 10.2%, 6.8% of LOT1-4, respectively. Additionally, over time, triplet regimen (KRd, KPd, KCyd) use increased. In 2012-2014, these triplet regimens were 29.8%, 32.5%, and 40.1% of all K regimens, respectively. Triplet use increased to 46.9% and 47.1% by 2015-2016.Conclusion:In 2012-2014, real-world use of K was primarily at the 27-mg dose in combination with dexamethasone. In 2015-2016, treatment patterns shifted, with KRd and Kd56 being used in a higher proportion of K-treated patients. This pattern may continue to grow since data from the phase III trials of these regimens showed improved survival. Drug combinations of K with pomalidomide or cyclophosphamide were used during the entire study period. Use of K-based triplet regimens increased over time. Overall, use of K-based regimens continues to grow, and the regimens in which K is used are changing with emerging data and as the understanding of the disease management evolves over time. [Display omitted] DisclosuresKim:Amgen, Inc.: Employment, Equity Ownership. Werther:Amgen, Inc.: Employment, Equity Ownership. Iskander:Amgen: Employment, Equity Ownership. Gruber:Amgen, Inc.: Employment, Equity Ownership. Mezzi:Amgen, Inc.: Employment, Equity Ownership.

SETD2 Non-Genomic Loss of Function and p53 Functional Inactivation in Advanced Systemic Mastocytosis (SM): Pathogenetic and Therapeutic Implications

KIT constitutive activation is thought to be necessary but not sufficient for the development of aggressive systemic mastocytosis (ASM) and mast cell leukemia (MCL). The identification and dissection of cooperating pathogenetic pathways may set the basis for the development of novel therapeutic strategies.We have recently found that the HMC-1.1 and -1.2 MCL cell lines and ASM/MCL patients (pts) display histone H3 Lys36 trimethylation (H3K36Me3) deficiency as a result of non-genomic loss of function of the SETD2 methyltransferase. SETD2 plays a key role in the control of transcription and splicing fidelity, homologous recombination (HR), mismatch repair (MMR). Inhibition of proteasome-mediated degradation by bortezomib restored SETD2 protein expression and H3K36Me3. Reversing the detrimental effects of SETD2 and H36K36Me3 deficiency may be a promising therapeutic strategy.In this study, we aimed to investigate the effects of SETD2 loss of function in ASM and MCL and to assess the in vitro efficacy of second-generation proteasome inhibitors as therapeutic agents. To investigate whether increased DNA damage and reduced HR proficiency can be observed in SETD2/H3K36Me3-deficient SM, we used western blotting and immunofluorescence to assess phosphorylated histone 2A.X (γH2AX), which marks ongoing DNA damage signaling and DNA double strand breaks and Rad51, which is a surrogate for active HR. Compared to cells from healthy controls, cells from SETD2- and H3K36Me3-deficient MCL pts had significantly higher levels of γH2AX and Rad51. To assess whether the increased DNA damage may translate into a greater number of submicroscopic genomic lesions, and whether the degree of SETD2 down-modulation may be inversely correlated with the degree of genomic complexity, SNP-array data from 13 pts were examined. Structural complexity score (SCS) and genome instability index (GII) were not significantly different (SCS, 387 vs 376; GII, 0.293 vs 0.337) between pts with > or <50% residual SETD2 and H3K36Me3 levels, suggesting that the activity of HR repair may counteract DNA damage events. Moreover, SETD2 down-modulation was not associated with reduced MMR proficiency, as assessed by lack of microsatellite instability. On the other hand, RNA-seq in SETD2-deficient pts showed evidence of transcription and splicing defects like transcription-induced chimeras and intron retention not observed in healthy donors.In renal cell carcinoma cell lines, SETD2 has been shown to bind and activate p53. After proteasome inhibition, SETD2 was indeed found to immunoprecipitate with p53 in HMC-1.1 and -1.2 cells. Rescuing the interaction between SETD2 and p53 with bortezomib stabilized p53 and upregulated the expression levels of p53 targets including p21, p27, Bax and Gadd45a. This restored inhibition of cell proliferation, block of the transition towards cell cycle checkpoints and consequent activation of apoptosis. The ubiquitin E3 ligase MDM2 was also found to complex with SETD2 after proteasomal inhibition. Treatment with SP-141, a new class of MDM2 inhibitors that promote MDM2 auto-ubiquitination and degradation, also rescued SETD2 expression and H3K36Me3, suggesting that MDM2 may play a role in SETD2 degradation in ASM and MCL. Moreover, SP-141 treatment of HMC-1 cells at micromolar doses for 24-48-72-96 hours induced cytostatic but not cytotoxic effects as shown by cell growth curves. Cytostatic effects resulted from a G2/M block of cell cycle induced by Gadd45a overexpression. Clonogenic assays supported the cytostatic effects of SP141 in HMC-1.1 and -1.2 cells (LD50=0.133µM and 0.050µM respectively).Finally, treatment with the second-generation proteasome inhibitors carfilzomib and ixazomib potently induced apoptosis and reduced colony growth in HMC-1.1 (LD50=0.10nM and 0.66nM respectively) and -1.2 (LD50=0.13nM and 0.72nM respectively) cells.In conclusion: MDM2-mediated ubiquitination contributes to SETD2 non-genomic loss of function in ASM and MCL. Loss of SETD2 and H3K36Me3 is associated with increased DNA damage and transcription and splicing defects in ASM and MCL pts and is likely to afford an alternative mechanism for the inactivation of the p53-mediated checkpoint without the need for TP53 gene mutations. Approaches aimed to inhibit MDM2 activity or proteasome-mediated degradation are promising therapeutic strategies worth to be further explored.Supported by AIL and AIRC (16996) DisclosuresZanotti:Deciphera: Consultancy. Ciceri:GSK: Other: B-thalassemia gene therapy was developed by Fondazione Telethon and Ospedale San Raffaele and has been inlicenced by GSK that provides funding for the clinical trial, Research Funding. Valent:Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; BMS: Honoraria; Ariad: Honoraria, Research Funding; Incyte: Honoraria; Deciphera: Honoraria, Research Funding; Pfizer: Honoraria; Blueprint: Research Funding; Teva: Honoraria. Martinelli:Amgen: Consultancy; Pfizer: Consultancy; Celgene: Consultancy; Roche: Consultancy; Johnson&Johnson: Consultancy; Ariad/Incyte: Consultancy. Soverini:Incyte Biosciences: Consultancy; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy.

A Randomized Study of Carfilzomib-Lenalidomide-Dexamethasone Vs Carfilzomib-Cyclophosphamide-Dexamethasone Induction in Newly Diagnosed Myeloma Patients Eligible for Transplant: High Efficacy in High- and Standard-Risk Patients

Background :Proteasome inhibitor-based induction is currently considered standard of care in newly diagnosed multiple myeloma (NDMM) patients (pts) eligible for high-dose therapy and transplant (MEL200-ASCT). The second-generation proteasome inhibitor Carfilzomib proved to be effective, either in combination with Lenalidomide-Dexamethasone (KRd) or with Cyclophosphamide-Dexamethasone (KCd) (Jakubowiak, Blood 2012; Bringhen, Blood 2014). Aim : The primary objective of this analysis was to compare the efficacy of KRd vs KCd induction in pts eligible for transplantation. The secondary aim was to evaluate the efficacy of KRd vs KCd in different subgroups of pts according to prognostic features, focusing specifically on high-risk pts. Methods : NDMM pts Results : At data cut-off, 309 pts were randomized to KRd vs 154 pts to KCd. Pts characteristics were well balanced: median age was 57 years in both groups, ISS Stage II/III was reported in 48% of pts in KRd and KCd, high-risk chromosomal abnormalities (del(17p) or t(4;14) or t(14;16)) were present in 30% of KRd pts and 34% of KCd pts. After 4 cycles of induction, the rate of ≥partial response (PR) was 96% with KRd vs 92% with KCd; ≥VGPR was 74% with KRd vs 61% with KCd (P=0.01), with 31% vs 20% of pts (P=0.03) achieving ≥near complete response (nCR) and 15% vs 6% (P=0.02) ≥complete response (CR) respectively in KRd and KCd; stable disease was reported in 3% of KRd vs 7% of KCd pts, with only 1% of pts in each group being primary refractory. Subgroup analysis of response rates showed the superiority of KRd vs KCd in terms of ≥VGPR in all the subgroups analyzed (Figure 1 - Panel A). Of interest, the rates of ≥VGPR, ≥nCR and ≥CR were comparable in high- and standard-risk pts treated with KRd (Figure 1 - Panel B). Six-month MRD results were available in a subset of pts (122 KRd and 53 KCd pts): MRD was negative in 66/122 (54%) KRd pts vs 16/53 (30%) KCd pts (P=0.005). Regarding safety, the rate of ≥1 grade 3-4 hematologic adverse events (AEs) was comparable between KRd and KCd (7% vs 6%), the most frequent being neutropenia (KRd 6% vs KCd 5%). The rate of ≥1 Grade 3-4 non-hematologic AEs was higher with KRd (32% vs 16%, P Conclusions :KRd induction showed a higher efficacy of KCd in terms of ≥VGPR, ≥nCR and ≥CR rates, with an acceptable safety profile. The superiority of KRd vs KCd was confirmed in high- and standard-risk groups, with response rates in high-risk pts treated with KRd comparable to the ones in standard-risk, suggesting the high efficacy of this regimen even in this subset of pts representing a current unmet medical need. Updated data will be presented at the meeting. Disclosures Gay: Takeda: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Seattle Genetics: Membership on an entity9s Board of Directors or advisory committees; Roche: Membership on an entity9s Board of Directors or advisory committees; Mundipharma: Membership on an entity9s Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Amgen: Honoraria; Celgene: Honoraria; Bristol Myers Squibb: Honoraria. Offidani: celgene: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity9s Board of Directors or advisory committees. Oliva: Takeda: Honoraria; Celgene: Honoraria. Mancuso: Bristol Myers Squibb: Honoraria; Amgen: Honoraria; Janssen: Honoraria; Celgene: Honoraria. Palumbo: Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding, Speakers Bureau; Takeda: Consultancy, Employment, Equity Ownership, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Genmab A/S: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Binding Site: Research Funding. Musto: Janssen: Honoraria; Celgene: Honoraria. Boccadoro: Amgen: Honoraria, Research Funding; Mundipharma: Research Funding; AbbVie: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding.

KD-PACE Salvage Therapy for Aggressive Relapsed Refractory Multiple Myeloma, Plasma Cell Leukemia and Extramedullary Myeloma

BackgroundPatients with advanced/aggressive multiple myeloma have limited treatment options to achieve rapid disease control. In eligible patients, bortezomib, dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide, and etoposide is often used. However, many patients are refractory to or have toxicities from bortezomib and there is a need for bridging therapy. We have used a modified regimen incorporating the second-generation proteasome inhibitor carfilzomib (carfilzomib, dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide and etoposide [KD-PACE]) instead of bortezomib for relapsed/refractory multiple myeloma. Patients and MethodsThis 2-center retrospective study included consecutive patients receiving KD-PACE for relapsed or refractory multiple myeloma, plasma cell leukemia, or extramedullary myeloma. The primary outcome was the feasibility of KD-PACE as a bridging therapy to a more definitive treatment option. ResultsFifty-two patients were included. The median age was 57 years, and 67% were male. Thirty-one patients were bridged with KD-PACE to autologous hematopoietic stem cell transplant (29%), allogenic hematopoietic stem cell transplant (27%), or a clinical trial (12%). Patients bridged to autologous hematopoietic stem cell transplant, allogenic hematopoietic stem cell transplant, or a clinical trial had a superior progression-free survival (8.3 months vs 2.3 months in the nonbridged group; P < .001) and overall survival (median, 16.7 months vs 4.3 months in the nonbridged group; P < .001). No unexpected toxicities occurred from the treatment regimen. ConclusionKD-PACE is a promising treatment option for select patients with advanced/aggressive forms of myeloma requiring rapid disease control before a more definitive salvage therapy such as auto/allotransplantation or a clinical trial.

Inhibition of P-Glycoprotein Does Not Increase the Efficacy of Proteasome Inhibitors in Multiple Myeloma Cells.

P-Glycoprotein is a well-known drug transporter associated with chemotherapy resistance in a number of cancers, but its role in modulating proteasome inhibitor efficacy in multiple myeloma is not well understood. The second-generation proteasome inhibitor carfilzomib is thought to be a substrate of P-glycoprotein whose efficacy may correlate with P-glycoprotein activity; however, research concerning the first-in-class proteasome inhibitor bortezomib is inconsistent. We show that while P-glycoprotein gene expression increases with the disease stages leading to multiple myeloma it does not affect the survival of newly diagnosed patients treated with bortezomib. Moreover, RNA-seq on LP-1 cells demonstrated minimal basal P-glycoprotein expression which did not increase after exposure to bortezomib or carfilzomib. Only one (KMS-18) of nine multiple myeloma cell lines expressed P-glycoprotein, including RPMI-8226 cells that are resistant to bortezomib or carfilzomib. We hypothesized that by inhibiting P-glycoprotein multiple myeloma cell sensitivity to proteasome inhibitors would increase; however, the sensitivity of multiple myeloma cells lines to proteasome inhibition was not enhanced by the specific P-glycoprotein inhibitor tariquidar. In addition, targeting glucosylceramide synthase with eliglustat did not inhibit P-glycoprotein activity nor improve proteasome inhibitor efficacy except at a high concentration. To confirm these negative findings, tariquidar did not substantially increase the cytotoxicity of bortezomib or carfilzomib in P-glycoprotein-expressing K562/ADM cells. We conclude the following: P-glycoprotein expression may not correlate with the survival of newly diagnosed multiple myeloma patients treated with proteasome inhibitors. P-glycoprotein is poorly expressed in many multiple myeloma cell lines, and its inhibition does not appreciably enhance the efficacy of proteasome inhibitors.

A study of carfilzomib and dexamethasone in patients with relapsed and refractory multiple myeloma in China.

The second-generation proteasome inhibitor carfilzomib produces superior outcomes in relapsed or refractory multiple myeloma (MM). We conducted a single-arm trial of twice-weekly carfilzomib (27mg/m2)-dexamethasone (Kd27) for relapsed and refractory MM in China. Kd27 was administered in 28-day cycles to 123 patients previously treated with ≥ 2 other regimens, including treatment with bortezomib and an immunomodulatory drug, and refractory to their most recent therapy. Overall response rate (ORR) was the primary endpoint; progression-free survival (PFS) and overall survival (OS) were key secondary endpoints. Primary analysis was conducted when all patients received ≥ 6 cycles of Kd27 or discontinued Kd27. Median age was 60years; median number of prior regimens was 4; 74% were refractory to proteasome inhibitors and immunomodulatory drugs. ORR was 35.8% (95% CI 27.3-44.9), median PFS was 5.6 (95% CI 4.6-6.5) months, and median OS was 16.6 (95% CI 12.2-NE) months. Grade ≥ 3 adverse events (AEs) occurred in 76.4% of patients. Grade ≥ 3 AEs of interest included hypertension (13.8%), acute renal failure (3.3%), cardiac failure (0.8%), ischemic heart disease (0.0%), and peripheral neuropathy (0.0%); 5.7% of patients discontinued carfilzomib due to AEs. Carfilzomib-dexamethasone produced a clinically meaningful response without new safety findings in Chinese patients with previously treated MM.Trial registration: NCT03029234.

The proteasome - structural aspects and inhibitors: a second life for a validated drug target

The proteasome is the central component of the adaptable ubiquitin proteasome system (UPS) discovered in the 1980's. It sustains protein homeostasis (proteostasis) under a large variety of physiological and pathological conditions. Its dysregulation has been often associated to various human diseases. Its potential regulation by modulators has emerged as promising avenue to develop treatments of various pathologies. The FDA approval in 2003 of the proteasome inhibitor bortezomib to treat multiple myeloma, then mantle lymphoma in 2006, has considerably increased the clinical interest of proteasome inhibition. Second-generation proteasome inhibitors (carfilzomib and ixazomib) have been approved to overcome bortezomib resistance and improved toxicity profile and route of administration. Selective inhibition of immunoproteasome is a promising approach towards the development of immunomodulatory drugs. The design of these drugs relies greatly on the elucidation of high-resolution structures of the targeted proteasomes. The ATPase-dependent 26S proteasome (2.4 MDa) consists of a 20S proteolytic core and one or two 19S regulatory particles. The 20S core contains three types of catalytic sites. In recent years, due to technical advances especially in atomic cryo-electron microscopy, significant progress has been made in the understanding of 26S proteasome structure and its dynamics. Stepwise conformational changes of the 19S particle induced by ATP hydrolysis lead to substrate translocation, 20S pore opening and processive protein degradation by the 20S proteolytic subunits (2β1, 2β2 and 2β5). A large variety of structurally different inhibitors, both natural products or synthetic compounds targeting immuno- and constitutive proteasomes, has been discovered. The latest advances in this drug discovery are presented. Knowledge about structures, inhibition mechanism and detailed biological regulations of proteasomes can guide strategies for the development of next-generation inhibitors to treat human diseases, especially cancers, immune disorders and pathogen infections. Proteasome activators are also potentially applicable to the reduction of proteotoxic stresses in neurodegeneration and aging.

Resistance of osteosarcoma cells to the proapoptotic effects of carfilzomib involves activation of mitogen activated protein kinase pathways.

What is the central question of this study? Carfilzomib, a second-generation proteasome inhibitor approved for the treatment of multiple myeloma, shows efficacy against osteosarcoma. However, drug resistance remains a major challenge. What is the role of carfilzomib-induced changes in mitogen-activated protein kinase (MAPK) pathways in the sensitivity of osteosarcoma cells to the proapoptotic effects of the drug? What is the main finding and its importance? The dose-dependent antiapoptotic effects in osteosarcoma are associated with activation of MAPK signalling. Combinational targeting of MAPK signalling pathways can synergistically enhance carfilzomib-induced cell apoptosis, suggesting that MAPK inhibitors in combination with proteasome inhibitors can serve as a novel therapeutic tool for osteosarcoma. Osteosarcoma is the most common primary bone malignancy. Despite efforts to improve outcomes, the overall survival rates for osteosarcoma have remained unchanged over the past three decades. In this study, we assessed the proapoptotic effects of the second-generation proteasome inhibitor carfilzomib on osteosarcoma and investigated the potential mechanisms underlying the synergistic proapoptotic action when combined with mitogen-activated protein kinase (MAPK) inhibitors. We found that carfilzomib alone significantly inhibited cell proliferation and induced apoptosis in a dose-dependent manner, characterized by the induction of cleaved caspase 3 and poly (ADP-ribose) polymerase. More importantly, focusing on the changes of antiapoptotic B-cell lymphoma 2 (Bcl-2) family members and signalling pathways, we found a striking induction of myeloid cell leukaemia 1 (Mcl-1) and the activation of MAPK pathways. Furthermore, we observed that combinational targeting of the MAPK pathways using the specific inhibitors U0126, SP600125 or SB203580 synergistically enhanced carfilzomib-induced cell apoptosis. Notably, we found that the combinational inhibition of extracellular signal-regulated kinase or c-Jun N-terminal kinase MAPK pathways significantly decreased the expression of the three antiapoptotic Bcl-2 family proteins, and in particular this reversed induction of Mcl-1 by carfilzomib. Collectively, our findings show that activation of the MAPK pathways contributes to the mechanisms of drug resistance to carfilzomib. In addition, the synergistic proapoptotic action of MAPK and proteasome inhibitors in osteosarcoma cells suggests that combinational therapy with both drug types may serve as a novel strategy for the clinical management of osteosarcoma.

Updates on Emerging Therapies in Cardiac Light Chain (AL) Amyloidosis

Introduction: Amyloidosis is a disorder where misfolded proteins get deposited in different tissues. The most common of them is immunoglobulin light chain (AL) deposition, otherwise known as AL amyloidosis. Cardiac involvement generally correlates with poor prognosis, and treatment options are limited if presented late. Novel disease-modifying agents are being studied in on-going trials to optimize treatment strategy. This review aims to summarize the updates on upcoming treatment options for AL amyloidosis, particularly involving the heart. Methodology: We performed a comprehensive literature search on PubMed, clinicaltrials.gov, and Cochrane databases (last updated on May 20, 2020). We used MeSH terms along with their keywords and combined their results. The literature search generated a total of 652 references. Two independent reviewers screened the articles and shortlisted 21 clinical trials that were included in our final review. Results: Monoclonal antibodies (daratumumab, isatuximab, elotuzumab and birtamimab) are being studied as monotherapy and combinations in relapsed/refractory (RR) AL amyloidosis. Despite good data on efficacy and safety, Daratumumab has not been approved yet in this category for advanced cardiac amyloidosis patients. Isatuximab showed the overall hematological response (HR) of 56% in phase I trial in a combination regimen and is now being evaluated as monotherapy in phase II. In a recent phase III trial of RR AL amyloidosis patients, the median progression-free survival was assessed over 24.5 months. It was increased from 14.9 months (lenalidomide and dexamethasone alone) to 19.4 months (elotuzumab, lenalidomide, and dexamethasone). Immunomodulators (lenalidomide, pomalidomide, thalidomide) are well studied for safety in other malignancies. Lenalidomide in various combinations has shown hematological response of greater than 60% in AL amyloidosis. Similarly, pomalidomide has shown an overall hematological response of 48-50% in two different early phase trials. Moreover, thalidomide was associated with significant toxicity in phase I/II trials and was discontinued. Second-generation proteasome inhibitors (ixazomib and carfilzomib) were assessed in RR cases of AL amyloidosis. Ixazomib achieved a hematological response of 52%. However, carfilzomib has been associated with cardiovascular toxicity and a higher risk of hospitalization in phase I trials, making it unsuitable. Venetoclax has shown encouraging results in multiple myeloma, particularly in t(11:14). 50% of AL amyloidosis cases have t(11:14) in whom venetoclax can be beneficial. A trial [NCT03000660] was suspended halfway citing clinical hold from regulatory authorities. Alkylating agents, mainly bendamustine, are currently under study after it showed a survival advantage in heavily pretreated cases [NCT01222260]. Underexplored venues: Small interfering RNAs (siRNAs) have a favorable response and excellent toxicity profile in AL amyloidosis. Issues regarding half-life and delivery systems have limited their use. CAEL-101, a novel chimeric fibril-reactive monoclonal antibody (gG1κ 11-1F4), tolerated well with improved organ function in AL amyloidosis in an early phase trial where it improved global longitudinal strain from baseline -9.58 to -13.39. SB203580 + rapamycin combination works in synergy with the former inhibiting the p38 MAPK pathway markedly reducing the toxicity of light chain immunoglobulins on cardiac myocytes and the latter restoring the SB203580-induced autophagic dysregulation. Epigallocatechin-3-gallate (EGCG) was well tolerated and found non-inferior to standard chemotherapy in a small phase II trial [NCT01511263]. Serum amyloid P (SAP) is a chaperone protein in amyloid fibril formation. Anti-SAP antibodies have shown promising results with safe toxicity profile in phase I trial [NCT01777243] in non-cardiac involved patients. However, another trial in cardiac involved cases was terminated due to significant toxicity. Table 1 Conclusion: Numerous drugs with novel mechanisms of actions are being studied, and results so far offer hope for improving the therapy &amp; outcomes, especially in patients with cardiac involvement. The drug combination regimens lead to slow down the disease progression by interfering at multiple steps in the cascade of light chain synthesis, secretion, deposition, and organ clearance. Disclosures Anwer: Incyte, Seattle Genetics, Acetylon Pharmaceuticals, AbbVie Pharma, Astellas Pharma, Celegene, Millennium Pharmaceuticals.: Honoraria, Research Funding, Speakers Bureau.

Carfilzomib-Based Regimens Are Efficacious and Well Tolerated in Heavily Pre-Treated Multiple Myeloma Patients: Real World Data from a Norwegian Cohort

IntroductionMultiple myeloma (MM) is considered an incurable disease. However, during the last years the survival has improved, partly due to the development of new drugs. The second-generation proteasome inhibitor Carfilzomib (Kyprolis®) was first approved for marketing in Norway in January 2016. Carfilzomib in combination with Dexamethasone (Kd) for patients with relapsing and/or refractory multiple myeloma (RRMM) was approved for reimbursement in August 2017, while the combination with Lenalidomide (Revlimid®) and Dexamethasone (KRd) is still not reimbursed in Norway. Both regimens now have mature and beneficial survival data (vs Vd and Rd, respectively). In the period before market approval, Carfilzomib was provided through a named patient program (NPP) for patients who had a critical disease with few treatments options. This abstract presents results from this cohort.AimIn this retrospective study all 33 Norwegian MM patients who received Carfilzomib through a named patient program (NPP) during the period of March 2014 to January 2016, were included. The aim was to describe the patients 'characteristics and their treatment responses, in addition to use the real-life experience to highlight a possible benefit of making new drugs available before marketing approval. During this study period, neither Daratumumab, Ixazomib nor Elotuzumab were available in Norway. The medical records were printed and sent from 10 different hospitals to Oslo Myeloma Center. Baseline values and treatment responses was assessed and entered into our myeloma database. Statistical analysis was done to determine response rates and time to event outcomes.ResultsThe participants had received a median of 6 (1-11) previous lines of therapy, including bortezomib (100%), and thalidomide and/or lenalidomide (97%) before inclusion in this study Among these, 64 % or 66 % respectively was refractory to the indicated treatment. 76 % of the study participants had received at least one ASCT. Median time from diagnosis to initiating carfilzomib treatment was 5 years (0-15) for the 32 patients who received carfilzomib. Patients who received the triplet treatment KRd, had a benefit in terms of response with ORR of 19%, compared to 8 %for patients receiving Kd/K (p=0, 04). CBR for these patients was 22 % and 25 %, respectively (p=0,33). There was no difference between the two groups for PFS or OS, with a median OS of 10 months (0-24) for patients receiving KRd compared to 9 month (2-14) for Kd/K. However, patients receiving KRd showed a trend towards a better PFS compared to Kd with a median PFS of 3,5 months (1,4 - 4,6) compared to 2,5 months (0,2 - 3,8) (p=0,095).Adverse events occurred in 91 % of the patients where 41 %, 31 % and 41 % respectively experienced a Grade 3 or higher for anemia, neutropenia or thrombocytopenia (according to CTCAE vs 4.0). 19 % experienced cardiovascular complications and 3% ended treatment due to them. Of these patients, 50 % had received doxorubicin at a previous treatment line and 17% received doxorubicin in combination with Carfilzomib. Overall, 9% of the patients discontinued the treatment due to adverse events while 6 % died before the end of the treatment. Carfilzomib was not considered a direct cause of death in any of these patients. At the end of the study (January 2018), 76 % of the participants were dead.ConclusionIn this real-life study, RRMM patients who received lenalidomide in addition to carfilzomib and dexametason showed a superior response in comparison with patients who received carfilzomib and dexamethasone with an ORR of 19 % versus 8 %. There was no significant overall survival benefit, but a trend towards a better PFS for KRd compared to Kd/K. As an overall conclusion, this group of highly treated MM patients had a benefit from receiving Carfilzomib in combination with lenalidomide before marketing approval. DisclosuresSchjesvold:Oncopeptides: Consultancy; Novartis: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Adaptive: Consultancy; Bayer: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Abbvie: Honoraria.

Carfilzomib-Lenalidomide-Dexamethasone (KRd) Induction-Autologous Transplant (ASCT)-Krd Consolidation Vs KRd 12 Cycles Vs Carfilzomib-Cyclophosphamide-Dexamethasone (KCd) Induction-ASCT-KCd Consolidation: Analysis of the Randomized Forte Trial in Newly Diagnosed Multiple Myeloma (NDMM)

Background: Proteasome inhibitor (PI)-based induction and consolidation proved to be effective in newly diagnosed multiple myeloma (NDMM) patients (pts) eligible for melphalan 200 mg/m2-autologous stem cell transplant (MEL200-ASCT). High response rates have been reported with the second-generation PI Carfilzomib in combination with Lenalidomide-dexamethasone (KRd) or Cyclophosphamide-dexamethasone (KCd). Aims: The primary aim was to evaluate the efficacy and safety of KRd induction-ASCT-KRd consolidation (KRd-ASCT-KRd) vs 12 cycles of KRd (KRd12) vs KCd induction-ASCT-KCd consolidation (KCd-ASCT-KCd). Methods: NDMM pts ≤65 years were randomized (1:1:1; stratification ISS and age) to: KRd-ASCT-KRd: 4 28-day cycles with KRd induction (Carfilzomib 20/36 mg/m2 IV days 1,2,8,9,15,16; Lenalidomide 25 mg days 1-21; dexamethasone 20 mg days 1,2,8,9,15,16) followed by MEL200-ASCT and 4 KRd consolidation cycles; KRd12: 12 KRd cycles; KCd-ASCT-KCd: 4 28-day induction cycles with KCd (Carfilzomib 20/36 mg/m2 IV days 1,2,8,9,15,16; Cyclophosphamide 300 mg/m2 days 1,8,15; dexamethasone 20 mg days 1,2,8,9,15,16) followed by MEL200-ASCT and 4 KCd consolidation cycles. Thereafter, pts were randomized to maintenance with Lenalidomide alone or plus Carfilzomib. Centralized minimal residual disease (MRD) evaluation - 8-color second generation flow cytometry, sensitivity 10-5 - was performed in pts achieving ≥very good partial response (VGPR). Endpoints were pre-maintenance stringent complete response (sCR) and MRD negativity in intention-to-treat (ITT) analysis. Data cut-off was May 30, 2018. Results: 474 NDMM pts were randomized (KRd-ASCT-KRd, n=158; KRd12, n=157; KCd-ASCT-KCd, n=159) and analyzed. Pts characteristics were well balanced. Median follow-up was 20 months. Depth of response improved during treatment (Figure). By ITT analysis, rates of pre-maintenance sCR was similar between KRd-ASCT-KRd (41%) and KRd12 (42%), and significantly higher than with KCd-ASCT-KCd (30%; P value KRd-ASCT-KRd vs KCd-ASCT-KCd=0.047; P value KRd12 vs KCd-ASCT-KCd=0.028). Similarly, rate of ≥CR was 49% with KRd-ASCT-KRd, 52% with KRd12 and 38% with KCd-ASCT-KCd (P value KRd-ASCT-KRd vs KCd-ASCT-KCd=0.041; P value KRd12 vs KCd-ASCT-KCd=0.014) and rate of ≥CR+unconfirmed CR (missing immunofixation confirmation) raised to 60% vs 63% vs 46% in the 3 groups, respectively; rate of ≥VGPR was 88% with KRd-ASCT-KRd, 86% with KRd12 and 74% with KCd-ASCT-KCd (P value KRd-ASCT-KRd vs KCd-ASCT-KCd=0.002; P value KRd12 vs KCd-ASCT-KCd=0.008). In multivariate analysis, the main factor affecting probability of achieving ≥VGPR, ≥CR or sCR was treatment with KRd-ASCT-KRd or KRd12 vs KCd, with no significant impact of ISS Stage or FISH abnormalities. In ITT analysis (MRD missing [31/395 VGPR pts, 8%] and Conclusions: Rates of MRD negativity, sCR, ≥CR, ≥VGPR were significantly higher with KRd-ASCT-KRd and KRd12 vs KCd. At present, no differences in MRD and overall best response (sCR, ≥CR, ≥VGPR) were noticed between KRd-ASCT-KRd and KRd12; longer follow-up is needed to evaluate survival. Treatment was well tolerated. Updated data will be presented at the meeting. Disclosures Gay:Roche: Other: Advisory Board; Seattle Genetics: Other: Advisory Board; Bristol-Myers Squibb: Honoraria; Janssen: Honoraria; Celgene: Honoraria, Other: Advisory Board; Amgen: Honoraria; Takeda: Honoraria, Other: Advisory Board. Galli:Sigma-Tau: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria. Belotti:Celgene: Other: Advisory Board; Amgen: Other: Advisory Board. Zamagni:BMS: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity9s Board of Directors or advisory committees. Angelucci:Novartis: Honoraria, Other: Chair Steering Committee TELESTO protocol in MDS; Celgene: Honoraria, Other: Chair DMC proptocol BELIEVE 1 and BELIVE 2 in Thalassemia; Vertex Pharmaceuticals Incorporated (MA) and CRISPR Therapeutics AG (CH): Other: Chair DMC CRISPR CAS9 in Hemoglobinopathies; Jazz Pharmaceuticals Italy: Other: Local (national) advisory board on AML; Roche Italia: Other: Local (national) advisory board on biosimilars. Annibali:Celgene; Takeda; Amgen, Janssen Cilag: Honoraria. Offidani:Amgen: Honoraria, Other: Advisory Board; Takeda: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Celgene: Honoraria, Other: Advisory Board; Bristol-Myers Squibb: Honoraria, Other: Advisory Board. Palumbo:Takeda: Employment. Musto:Amgen: Honoraria; BMS: Honoraria; Takeda: Honoraria; Janssen: Honoraria; Celgene: Honoraria. Cavo:GlaxoSmithKline: Honoraria, Membership on an entity9s Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity9s Board of Directors or advisory committees. Boccadoro:Bristol-Myers Squibb: Honoraria, Research Funding; Mundipharma: Research Funding; Sanofi: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; AbbVie: Honoraria.

Phase 1/2 Trial of Carfilzomib Plus High-Dose Melphalan Preparative Regimen for Salvage Autologous Hematopoietic Cell Transplantation Followed by Maintenance Carfilzomib in Patients with Relapsed/Refractory Multiple Myeloma

We performed a phase 1/2 trial to investigate the safety and activity of the second-generation proteasome inhibitor Carfilzomib (K) on days -3/-2 in combination with melphalan 200 mg/m2 (MEL200) on day -2 (K-MEL) in patients with relapsed multiple myeloma (MM) undergoing autologous hematopoietic cell transplantation (phases 1 and 2). Patients without progression received 12 cycles of K maintenance at 36 mg/m2 days 1, 8, and 15 (schedule A) or days 1, 2, 15, and 16 (schedule B), with patients being treated for 2 cycles in each schedule and on the patient-preferred schedule for the remaining cycles (phase 2). The patients had received a median of 3 previous lines of therapy, 56% had undergone previous AHCT, and 51% had received previous K therapy. During phase 1 (n = 15), the maximum tolerated dose of K in combination with MEL200 was not reached, so the maximum tested dose of 27 mg/m2 (on day -3) and 56 mg/m2 (on day -2) was used in phase 2. The rate of very good partial response after K-MEL therapy (n = 44) was 59.2%, compared with 13.7% before K-MEL therapy. Among patients starting maintenance therapy (n = 27), 12-month progression-free survival was 66.7% and 12-month overall survival was 88.1%. There was no strong patient preference for either schedule. Two patients discontinued maintenance due to toxicity. K-MEL followed by K maintenance is safe and active salvage therapy in patients with MM.

Multiple myeloma : What has been confirmed in therapy?

Multiple myeloma (MM) is amalignancy of terminally differentiated Bcells/plasma cells and is primarily located in the bone marrow. Symptomatic multiple myeloma typically presents with osteolyses, anemia, reduced renal function, and/or hypercalcemia. In the case of such MM-related end organ damage, urgent systemic treatment is indicated. In order to prevent end organ damage, current guidelines now recommend treatment initiation already when certain biomarkers are met. Current first-line treatment is based on proteasome inhibition and immunomodulation. Eligible patients still benefit from the addition of high-dose chemotherapy and autologous stem cell transplantation. Radiotherapy and orthopedic interventions play an important role in the treatment of localized skeletal complications. For relapsed MM, five novel agents have been approved in Europe during the last two years. These are second-generation proteasome inhibitors (carfilzomib, ixazomib) as well as first-in-class monoclonal antibodies (daratumumab, elotuzumab) and ahistone deacetylase inhibitor (panobinostat). Triple combinations based on the established regimens lenalidomide/dexamethasone and bortezomib/dexamethasone plus one of the novel agents have been shown to significantly prolong progression-free survival. Median overall survival of patients with MM has doubled since the turn of the millennium.

Nrf2: not "lost in translation".

Multiple myeloma (MM) is a clonal plasma cell malignancy which is frequently diagnosed in patients over 65 years of age. Because of an aging population, the incidence of MM has increased nearly 1 percent annually since 1975 and it is anticipated that the number of cases will nearly double by 2034 [1]. The introduction of novel agents such as the proteasome inhibitor bortezomib (BTZ) has significantly improved overall survival of patients with MM during the past decade. Therapeutic efficacy is related to the exquisite dependence of MM cells on proteasomal degradation of unfolded proteins to maintain proteostasis. However, progression towards BTZ-refractory disease occurs in the majority of MM patients. Unfortunately, once MM patients become refractory to BTZ, their median overall survival has been reported to be less than 1 year [2]. Moreover, in a pivotal phase 2 study with the second-generation proteasome inhibitor carfilzomib (CFZ), less than a 25% response rate was achieved in BTZ-treated patients who had relapsed [3]. These results indicate that the majority of MM cells that became resistant to BTZ were also resistant to CFZ. Clearly, to extend the life expectancy of patients with MM, it is essential to elucidate the underlying mechanisms of acquired proteasome inhibitor resistance.

Second-generation proteasome inhibitor carfilzomib sensitizes neuroblastoma cells to doxorubicin-induced apoptosis.

Neuroblastoma (NB), which accounts for about 15% of cancer-related mortality in children, is the most common extracranial malignant neoplasm in children. Elevated level of proteasome activity promotes cancer development and the inhibition of proteasome activity is a promising strategy for cancer treatment. Therefore, targeting proteasome by small molecule inhibitors may be a viable option for NB therapy. Here in this study, we show that a novel proteasome inhibitor Carfilzomib (CFZ) exerts anti-tumor effect on NB. CFZ caused decreased cell viability and attenuated colony formation ability of a subset of NB cell lines. CFZ induced cell apoptosis in NB cells. Moreover, CFZ enhanced the cytotoxic effect of doxorubicin (Dox) on NB cells and Dox-induced p38 and JNK phosphorylation. In addition, CFZ inhibited Dox-induced NF-κB activation by stabilizing the protein level of IκBα. Furthermore, CFZ induced apoptosis and augmented Dox-induced apoptosis in NB tumor cells in orthotopic xenograft mouse models. In summary, our study suggests that proteasome is a therapeutic target in NB and proteasome inhibition by CFZ is a potential therapeutic strategy for treating NB patients.