Carfilzomib in multiple myeloma

Myeloma bone disease: pathogenesis and management in the era of new anti-myeloma agents

INTRODUCTION

Multiple myeloma (MM) is a malignancy of plasma cells with characteristic bone disease. Despite recent great strides achieved in MM treatment owing to the implementation of new anti-MM agents, MM is still incurable and bone destruction remains a serious unmet issue in patients with MM.

APPROACH

In this review, we will summarize and discuss the mechanisms of the formation of bone disease in MM and the available preclinical and clinical evidence on the treatment for MM bone disease.

CONCLUSIONS

MM cells produce a variety of cytokines to stimulate receptor activator of nuclear factor-κB ligand-mediated osteoclastogenesis and suppress osteoblastic differentiation from bone marrow stromal cells, leading to extensive bone destruction with rapid loss of bone. MM cells alter the microenvironment through bone destruction where they colonize, which in turn favors tumor growth and survival, thereby forming a vicious cycle between tumor progression and bone destruction. Denosumab or zoledronic acid is currently recommended to be administered at the start of treatment in newly diagnosed patients with MM with bone disease. Proteasome inhibitors and the anti-CD38 monoclonal antibody daratumumab have been demonstrated to exert bone-modifying activity in responders. Besides their anti-tumor activity, the effects of new anti-MM agents on bone metabolism should be more precisely analyzed in patients with MM. Because prognosis in patients with MM has been significantly improved owing to the implementation of new agents, the therapeutic impact of bone-modifying agents should be re-estimated in the era of these new agents.

Small Molecule 20S Proteasome Enhancer Regulates MYC Protein Stability and Exhibits Antitumor Activity in Multiple Myeloma

Despite the addition of several new agents to the armamentarium for the treatment of multiple myeloma (MM) in the last decade and improvements in outcomes, the refractory and relapsing disease continues to take a great toll, limiting overall survival. Therefore, additional novel approaches are needed to improve outcomes for MM patients. The oncogenic transcription factor MYC drives cell growth, differentiation and tumor development in many cancers. MYC protein levels are tightly regulated by the proteasome and an increase in MYC protein expression is found in more than 70% of all human cancers, including MM. In addition to the ubiquitin-dependent degradation of MYC by the 26S proteasome, MYC levels are also regulated in a ubiquitin-independent manner through the REGγ activation of the 20S proteasome. Here, we demonstrate that a small molecule activator of the 20S proteasome, TCH-165, decreases MYC protein levels, in a manner that parallels REGγ protein-mediated MYC degradation. TCH-165 enhances MYC degradation and reduces cancer cell growth in vitro and in vivo models of multiple myeloma by enhancing apoptotic signaling, as assessed by targeted gene expression analysis of cancer pathways. Furthermore, 20S proteasome enhancement is well tolerated in mice and dogs. These data support the therapeutic potential of small molecule-driven 20S proteasome activation for the treatments of MYC-driven cancers, especially MM.

A combination of carfilzomib, dexamethasone, and daratumumab for treatment of adult patients with relapsed/refractory multiple myeloma in two dosing regimens: once-weekly and twice-weekly

INTRODUCTION

Despite the development of new therapeutic agents, relapsed/refractory multiple myeloma (RRMM) is associated with poor survival outcomes. Furthermore, many patients develop resistance to immunomodulatory drugs (IMiD), creating a need for IMiD-free regimens. Areas covered: This review focuses on the combination of carfilzomib, dexamethasone, and daratumumab (KdD or DKd) which has shown promising results in patients with RRMM who have tried multiple lines of therapy, and has been approved in the U.S., EU, and Japan. The KdD triplet has two recommended dosage regimens, carfilzomib once-weekly (KdD70 QW) and carfilzomib twice-weekly (KdD56 BIW), with comparable efficacy and safety profiles. Expert opinion: These options provide flexibility to patients and healthcare providers, especially in the era of COVID-19. Carfilzomib-based regimens remain a standard of care based on multiple randomized phase 3 studies. Additional studies are currently underway investigating carfilzomib-based regimens such as KdD combined with novel agents. Nevertheless, KdD is one of the most efficacious options for patients with RRMM.

In-depth proteomic analysis of proteasome inhibitors bortezomib, carfilzomib and MG132 reveals that mortality factor 4-like 1 (MORF4L1) protein ubiquitylation is negatively impacted

Proteasome inhibitors are an important class of chemotherapeutic drugs. In this study, we performed a large-scale ubiquitylome analysis of the three proteasome inhibitors MG132, bortezomib and carfilzomib. Although carfilzomib is currently being used for the treatment of multiple myeloma, it has not yet been subjected to a global ubiquitylome analysis. In this study, we identified more than 14,000 unique sites of ubiquitylation in more than 4400 protein groups. We introduced stringent criteria to determine the correct ubiquitylation site ratios and used five biological replicates to achieve increased statistical power. With the vast amount of data acquired, we made proteome-wide comparisons between the proteasome inhibitors and indicate candidate proteins that will benefit from further study. We find that in addition to the expected increase in ubiquitylation in the majority of proteins, unexpectedly a select few are specifically and significantly decreased in ubiquitylation at specific sites after treatment with proteasome inhibitors. We chose to follow-up on Mortality factor 4-like 1 (MORF4L1), which was significantly decreased in ubiquitylation at lysine 187 and lysine 104 upon proteasome inhibition, but increased in protein abundance by approximately two-fold. We demonstrate that the endogenous protein level of MORF4L1 is highly regulated by the ubiquitin proteasome system. SIGNIFICANCE: This study provides a highly curated dataset of more than 14,000 unique sites of ubiquitylation in more than 4400 protein groups. For the proper quantification of ubiquitylation sites, we introduced a higher standard by quantifying only those ubiquitylation sites that are not flanked by neighboring ubiquitylation, thereby avoiding the report of incorrect ratios. The sites identified will serve to identify important targets of the ubiquitin proteasome system and aid to better understand the repertoire of proteins that are affected by inhibiting the proteasome with MG132, bortezomib, and carfilzomib. In addition, we investigated the unusual observation that ubiquitylation of the tumor suppressor Mortality factor 4-like (MORF4L1) protein decreases rather than increases upon proteasome inhibition, which may contribute to an additional anti-tumor effect of bortezomib and carfilzomib.

Polymeric micelles loaded with carfilzomib increase tolerability in a humanized bone marrow-like scaffold mouse model

Carfilzomib-loaded polymeric micelles (CFZ-PM) based on poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) (mPEG-b-p(HPMA-Bz)) were prepared with the aim to improve the maximum tolerated dose of carfilzomib in a “humanized” bone marrow-like scaffold model. For this, CFZ-PM were prepared and characterized for their size, carfilzomib loading and cytotoxicity towards multiple myeloma cells. Further, circulation and tumor & tissue distribution of fluorescently labeled micelles were determined. Tolerability of CFZ-PM versus the clinical approved formulation – Kyprolis® – was assessed. CFZ-PM presented small diameter below 55 nm and low PDI < 0.1. Cy7-labeled micelles circulated for extended periods of time with over 80% of injected dose in circulation at 24 h after intravenous injection and 1.3% of the injected dose of Cy7-labeled micelles accumulated in myeloma tumor-bearing scaffolds. Importantly, CFZ-PM were well tolerated whereas Kyprolis® showed adverse effects. Kyprolis® dosed at the maximum tolerated dose, as well as CFZ-PM, did not show therapeutic benefit, while multiple myeloma cells showed sensitivity in vitro, underlining the importance of the bone marrow crosstalk in testing novel formulations. Overall, this work indicates that PM are potential drug carriers of carfilzomib.

Pipecolic esters as minimized templates for proteasome inhibition

Allosteric regulators of clinically important enzymes are gaining popularity as alternatives to competitive inhibitors. This is also the case for the proteasome, a major intracellular protease and a target of anti-cancer drugs. All clinically used proteasome inhibitors bind to the active sites in catalytic chamber and display a competitive mechanism. Unfortunately, inevitable resistance associated with this type of inhibition drives the search for non-competitive agents. The multisubunit and multicatalytic "proteolytic machine" such as the proteasome is occasionally found to be affected by agents with other primary targets. For example the immunosuppressive agent rapamycin has been shown to allosterically inhibit the proteasome albeit at levels far higher than its mTOR related efficacy. As part of an ongoing program to search for novel proteasome-targeting pharmacophores, we identified the binding domain of rapamycin as required for proteasome inhibition even without the macrocyclic context of the parent compound. By subsequent structure-activity relationship studies, we generated a pipecolic ester derivative compound 3 representing a new class of proteasome inhibitors. Compound 3 affects the core proteasome activities and proliferation of cancer cells with low micromolar/high nanomolar efficacy. Molecular modeling, atomic force microscopy imaging and biochemical data suggest that compound 3 binds into one of intersubunit pockets in the proteasomal α ring and destabilizes the α face and the gate. The α face is used as a docking area for proteasome-regulating protein modules and the gate is critical for controlling access to the catalytic chamber. Thus, the pipecolic ester template elicits a new and attractive mechanism for proteasome inhibition distinct from classical competitive drugs.

Dual inhibition of Mcl-1 by the combination of carfilzomib and TG02 in multiple myeloma

Carfilzomib (Kyprolis®), a second generation proteasome inhibitor, is FDA approved for single-agent use among relapsed/refractory multiple myeloma (MM). To enhance the therapeutic efficacy of carfilzomib, we sought to combine carfilzomib with other novel agents. TG02, a multi-kinase inhibitor, targets JAK2 and CDK9. The rationale for co-treatment with carfilzomib and TG02 is that both independently target Mcl-1 and most myeloma cells are dependent on this anti-apoptotic protein for survival. We observed at least additive effects using the combination treatment in MM cell lines and patient samples. To determine how the bone marrow environment affects the efficacy of the combination we conducted co-culture experiments with Hs-5 stromal cells. We also examined the mechanism of increased apoptosis by determining the affect on expression of the Bcl-2 family of proteins. We found that carfilzomib increases NOXA mRNA expression, as expected, and TG02 treatment caused a decrease in Mcl-1 protein but not mRNA levels. Consistent with this possibility, we find silencing CDK9 does not change carfilzomib sensitivity in the same manner as addition of TG02. Since changes in Mcl-1 protein occur in the presence of a proteasome inhibitor we hypothesize that regulation of Mcl-1 translation is the most likely mechanism. Taken together our data suggest that dual inhibition of Mcl-1 via decreased expression and the induction of its antagonist NOXA by the combination of carfilzomib and TG02 is active in myeloma and warrants further testing preclinically and in clinical trials. Moreover, regulation of Mcl-1 by TG02 is more complex than initially appreciated.

Safety and tolerability of pomalidomide-based regimens (pomalidomide-carfilzomib-dexamethasone with or without cyclophosphamide) in relapsed/refractory multiple myeloma and severe renal dysfunction: a case series

Renal dysfunction negatively impacts outcomes in patients with multiple myeloma (MM). Few treatment options are currently available for patients with MM and comorbid renal dysfunction, and as they are generally excluded from clinical trials, data on the use of immunomodulatory drugs in this population are scarce. In this paper, we describe a case series of five women with MM and severe renal dysfunction or dialysis dependency who were refractory to both bortezomib and either lenalidomide or thalidomide and were treated with full-dose (4 mg) pomalidomide. As part of their treatment regimen, these patients also received carfilzomib and dexamethasone with or without cyclophosphamide. All five patients achieved at least a partial response to pomalidomide-based therapy, which was relatively well tolerated. Our findings suggest that pomalidomide may represent a valuable and tolerable treatment option for MM patients with severe renal impairment. The fact that pomalidomide is extensively metabolized prior to urinary excretion may explain the improved tolerability of pomalidomide versus lenalidomide in such patients. Copyright © 2016 John Wiley & Sons, Ltd.

Oral proteasome inhibitor with strong preclinical efficacy in myeloma models

BACKGROUND

The proteasome is a validated anti-cancer target and various small-molecule inhibitors are currently in clinical development or on the market. However, adverse events and resistance associated with those proteasome inhibitors indicate the need for a new generation of drugs. Therefore, we focused on developing an oral proteasome inhibitor with improved efficacy and safety profiles.

METHOD

The in vitro inhibition of the 20S proteasome catalytic activities was determined in human multiple myeloma (MM) cellular lysates with fluorogenic peptide substrates specific for each catalytic subunit. Cell cytotoxicity was assessed with the ATP bioluminescence assay using human cell samples from tumor cell lines, MM patients or normal healthy donors. In mice bearing human MM xenografts, a single dose of LC53-0110 was administered orally, and concentration-time profiles of LC53-0110 and the 20S proteasome catalytic activities in plasma, blood, and tumor were determined. The efficacy of repeat-dose compound with regard to tumor growth inhibition in vivo was also evaluated in the same MM xenograft models.

RESULTS

LC53-0110 is far more specific for the chymotrypsin-like proteolytic (β5) site of the 20S proteasome as compared to bortezomib, carfilzomib, or ixazomib. LC53-0110 treatment showed accumulation of ubiquitinated proteins, inhibited cell viability with a low nM range potency in various tumor cell lines, and showed potent activity on CD138(+) cells isolated from MM patients who are resistant/refractory to current FDA-approved drug treatment. When a single dose was administered orally to tumor-bearing mice, LC53-0110 showed both greater maximum and sustained tumor proteasome inhibition as compared with ixazomib in MM xenograft models. The robust pharmacodynamic responses in tumor correlated with tumor growth regression. In addition, LC53-0151, an analog of LC53-0110, in combination with pomalidomide, a third-generation immunomodulatory drug, showed synergistic inhibition of tumor growth both in vitro and in the xenograft mouse model.

CONCLUSIONS

In view of the in vitro, in vivo, and ex vivo profiles, further investigation of additional LC compounds in preclinical studies is warranted for the nomination of a clinical development candidate.

Carfilzomib for the treatment of patients with relapsed and/or refractory multiple myeloma

Carfilzomib is a proteasome inhibitor that irreversibly binds to its target, resulting in sustained proteasomal inhibition with minimal off-target effects. As a single agent, carfilzomib has demonstrated durable antimyeloma activity with manageable toxicities, which has resulted in its approval in Argentina, Israel, Mexico and the USA for the treatment of patients with relapsed and refractory multiple myeloma. Data from ongoing Phase III studies that are evaluating carfilzomib in earlier lines of therapy may facilitate an expanded indication for this agent, as well as for regulatory approval in the EU. This article summarizes the chemistry, pharmacokinetics, pharmacodynamics and available clinical data for carfilzomib in the treatment of patients with multiple myeloma.

Targeting Cdc20 as a novel cancer therapeutic strategy

The Anaphase Promoting Complex (APC, also called APC/C) regulates cell cycle progression by forming two closely related, but functionally distinct E3 ubiquitin ligase sub-complexes, APC(Cdc20) and APC(Cdh1), respectively. Emerging evidence has begun to reveal that Cdc20 and Cdh1 have opposing functions in tumorigenesis. Specifically, Cdh1 functions largely as a tumor suppressor, whereas Cdc20 exhibits an oncogenic function, suggesting that Cdc20 could be a promising therapeutic target for combating human cancer. However, the exact underlying molecular mechanisms accounting for their differences in tumorigenesis remain largely unknown. Therefore, in this review, we summarize the downstream substrates of Cdc20 and the critical functions of Cdc20 in cell cycle progression, apoptosis, ciliary disassembly and brain development. Moreover, we briefly describe the upstream regulators of Cdc20 and the oncogenic role of Cdc20 in a variety of human malignancies. Furthermore, we summarize multiple pharmacological Cdc20 inhibitors including TAME and Apcin, and their potential clinical benefits. Taken together, development of specific Cdc20 inhibitors could be a novel strategy for the treatment of human cancers with elevated Cdc20 expression.

Targeting the ubiquitin pathway for cancer treatment

Proteasome-mediated degradation is a common mechanism by which cells renew their intracellular proteins and maintain protein homeostasis. In this process, the E3 ubiquitin ligases are responsible for targeting specific substrates (proteins) for ubiquitin-mediated degradation. However, in cancer cells, the stability and the balance between oncoproteins and tumor suppressor proteins are disturbed in part due to deregulated proteasome-mediated degradation. This ultimately leads to either stabilization of oncoprotein(s) or increased degradation of tumor suppressor(s), contributing to tumorigenesis and cancer progression. Therefore, E3 ubiquitin ligases including the SCF types of ubiquitin ligases have recently evolved as promising therapeutic targets for the development of novel anti-cancer drugs. In this review, we highlighted the critical components along the ubiquitin pathway including E1, E2, various E3 enzymes and DUBs that could serve as potential drug targets and also described the available bioactive compounds that target the ubiquitin pathway to control various cancers.