Panobinostat for the treatment of multiple myeloma: the evidence to date

Design, Synthesis, and Biological Evaluation of Histone Deacetylase Inhibitors Derived from Erianin and Its Derivatives

Multi-target histone deacetylase (HDAC) inhibitors can be designed by introducing dominant structures of natural products to enhance activity and efficacy while avoiding the toxicity from other targets. In this study, we reported a series of novel HDAC inhibitors based on erianin and amino erianin upon pharmacophore fusion strategy. Two representative compounds, N-hydroxy-2-(2-methoxy-5- (3,4,5-trimethoxyphenethyl)phenoxy)acetamide and N-Hydroxy-8-((2-methoxy-5- (3,4,5-trimethoxyphenethyl)phenyl)amino)octanamide, possessed good inhibitory effect against five cancer cells tested (IC50 =0.30-1.29 μΜ, 0.29-1.70 μΜ) with strong HDAC inhibition, and low toxicity toward L02 cells, which were selected for subsequent biological studies in PANC-1 cells. They were also found to promote the intracellular generation of reactive oxygen species, cause DNA damage, block the cell cycle at G2/M phase, and activate the mitochondria-related apoptotic pathway to induce cell apoptosis, which are significant for the discovery of new HDAC inhibitors.

Deacetylation induced nuclear condensation of HP1γ promotes multiple myeloma drug resistance

Acquired chemoresistance to proteasome inhibitors is a major obstacle in managing multiple myeloma but key regulators and underlying mechanisms still remain to be explored. We find that high level of HP1γ is associated with low acetylation modification in the bortezomib-resistant myeloma cells using SILAC-based acetyl-proteomics assay, and higher HP1γ level is positively correlated with poorer outcomes in the clinic. Mechanistically, elevated HDAC1 in the bortezomib-resistant myeloma cells deacetylates HP1γ at lysine 5 and consequently alleviates the ubiquitin-mediated protein degradation, as well as the aberrant DNA repair capacity. HP1γ interacts with the MDC1 to induce DNA repair, and simultaneously the deacetylation modification and the interaction with MDC1 enhance the nuclear condensation of HP1γ protein and the chromatin accessibility of its target genes governing sensitivity to proteasome inhibitors, such as CD40, FOS and JUN. Thus, targeting HP1γ stability by using HDAC1 inhibitor re-sensitizes bortezomib-resistant myeloma cells to proteasome inhibitors treatment in vitro and in vivo. Our findings elucidate a previously unrecognized role of HP1γ in inducing drug resistance to proteasome inhibitors of myeloma cells and suggest that targeting HP1γ may be efficacious for overcoming drug resistance in refractory or relapsed multiple myeloma patients.

Discovery of Novel Histone Deacetylase 6 (HDAC6) Inhibitors with Enhanced Antitumor Immunity of Anti-PD-L1 Immunotherapy in Melanoma

A series of 2-phenylthiazole analogues were designed and synthesized as potential histone deacetylase 6 (HDAC6) inhibitors based on compound 12c (an HDAC6/tubulin dual inhibitor discovered by us recently) and CAY10603 (a known HDAC6 inhibitor). Among them, compound XP5 was the most potent HDAC6 inhibitor with an IC50 of 31 nM and excellent HDAC6 selectivity (SI = 338 for HDAC6 over HDAC3). XP5 also displayed high antiproliferative activity against various cancer cell lines including the HDACi-resistant YCC3/7 gastric cancer cells (IC50 = 0.16-2.31 μM), better than CAY10603. Further, XP5 (50 mg/kg) exhibited significant antitumor efficacy in a melanoma tumor model with a tumor growth inhibition (TGI) of 63% without apparent toxicity. Moreover, XP5 efficiently enhanced the in vivo antitumor immune response when combined with a small-molecule PD-L1 inhibitor, as demonstrated by the increased tumor-infiltrating lymphocytes and reduced PD-L1 expression levels. Taken together, the above results suggest that XP5 is a promising HDAC6 inhibitor deserving further investigation.

The Use of Oncolytic Viruses in the Treatment of Multiple Myeloma

Simple Summary

Multiple myeloma is a type of blood cancer caused by the uncontrolled growth of antibody producing B cells (known as plasma cells) that reside in the bone marrow. It is classed as a largely incurable cancer as whilst patients respond well to initial chemotherapy treatments, unfortunately after periods of disease remission, relapse usually occurs with the emergence of chemotherapy resistance. Therefore, there is a need for new approaches that not only reduce tumour load but also prevent tumour relapse. Oncolytic viruses (OVs) (tumour killing viruses) are being explored as a therapy for various cancers, including multiple myeloma. This review discusses the use of OVs in myeloma in preclinical model systems and early phase clinical trials, and discusses some of the hurdles involved in the translation to myeloma patients.

Abstract

Multiple myeloma accounts for 1% of all new cancers worldwide. It is the second most common haematological malignancy and has a low five-year survival rate (53.2%). Myeloma remains an incurable disease and is caused by the growth of malignant plasma cells in the bone marrow. Current anti-myeloma therapies (conventional chemotherapies, immunomodulatory drugs i.e., thalidomide and its’ analogues, proteasome inhibitors, monoclonal antibodies, and radiotherapy) initially substantially debulk tumour burden, but after a period of remission ‘plateau phase’ disease invariably relapses due to tumour recrudescence from foci of minimal residual disease (MRD) and accumulating drug resistance. Therefore, there is a compelling clinical need for the development of novel treatment regimens to target MRD and effectively eliminate all remaining tumour cells. This review will discuss the potential use of oncolytic virus (OV) therapies in the treatment of myeloma. Specifically, it will focus on preclinical studies using DNA viruses (adenovirus (Ad), vaccinia virus (VV), myxoma virus (MYXV), and herpes simplex virus (HSV)), RNA viruses (reovirus (reo), coxsackie virus, measles virus (MV) and bovine viral diarrhoea virus (BVDV), and vesicular stomatitis virus (VSV)), and on four types of viruses (VV, reo, MV-NIS and VSV-IFNβ-NIS) that have been assessed clinically in a small number of myeloma patients.

Valproic Acid Enhanced Temozolomide-Induced Anticancer Activity in Human Glioma Through the p53-PUMA Apoptosis Pathway

Glioblastoma (GBM), the most lethal type of brain tumor in adults, has considerable cellular heterogeneity. The standard adjuvant chemotherapeutic agent for GBM, temozolomide (TMZ), has a modest response rate due to the development of drug resistance. Multiple studies have shown that valproic acid (VPA) can enhance GBM tumor control and prolong survival when given in conjunction with TMZ. However, the beneficial effect is variable. In this study, we analyzed the impact of VPA on GBM patient survival and its possible correlation with TMZ treatment and p53 gene mutation. In addition, the molecular mechanisms of TMZ in combination with VPA were examined using both p53 wild-type and p53 mutant human GBM cell lines. Our analysis of clinical data indicates that the survival benefit of a combined TMZ and VPA treatment in GBM patients is dependent on their p53 gene status. In cellular experiments, our results show that VPA enhanced the antineoplastic effect of TMZ by enhancing p53 activation and promoting the expression of its downstream pro-apoptotic protein, PUMA. Our study indicates that GBM patients with wild-type p53 may benefit from a combined TMZ+VPA treatment.

Characterization of Histone Deacetylase Mechanisms in Cancer Development

Over decades of studies, accumulating evidence has suggested that epigenetic dysregulation is a hallmark of tumours. Post-translational modifications of histones are involved in tumour pathogenesis and development mainly by influencing a broad range of physiological processes. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are pivotal epigenetic modulators that regulate dynamic processes in the acetylation of histones at lysine residues, thereby influencing transcription of oncogenes and tumour suppressor genes. Moreover, HDACs mediate the deacetylation process of many nonhistone proteins and thus orchestrate a host of pathological processes, such as tumour pathogenesis. In this review, we elucidate the functions of HDACs in cancer.

Efficient Synthesis and Bioevaluation of Novel Dual Tubulin/Histone Deacetylase 3 Inhibitors as Potential Anticancer Agents

Novel dual HDAC3/tubulin inhibitors were designed and efficiently synthesized by combining the pharmacophores of SMART (tubulin inhibitor) and MS-275 (HDAC inhibitor), among which compound 15c was found to be the most potent and balanced HDAC3/tubulin dual inhibitor with high HDAC3 activity (IC50 = 30 nM) and selectivity (SI > 1000) as well as excellent antiproliferative potency against various cancer cell lines, including an HDAC-resistant gastric cancer cell line (YCC3/7) with IC50 values in the range of 30-144 nM. Compound 15c inhibited B16-F10 cancer cell migration and colony formation. In addition, 15c demonstrated significant in vivo antitumor efficacy in a B16-F10 melanoma tumor model with a better TGI (70.00%, 10 mg/kg) than that of the combination of MS-275 and SMART. Finally, 15c presented a safe cardiotoxicity profile and did not cause nephro-/hepatotoxicity. Collectively, this work shows that compound 15c represents a novel tubulin/HDAC3 dual-targeting agent deserving further investigation as a potential anticancer agent.

Evodiamine-inspired dual inhibitors of histone deacetylase 1 (HDAC1) and topoisomerase 2 (TOP2) with potent antitumor activity

A great challenge in multi-targeting drug discovery is to identify drug-like lead compounds with therapeutic advantages over single target inhibitors and drug combinations. Inspired by our previous efforts in designing antitumor evodiamine derivatives, herein selective histone deacetylase 1 (HDAC1) and topoisomerase 2 (TOP2) dual inhibitors were successfully identified, which showed potent in vitro and in vivo antitumor potency. Particularly, compound 30a was orally active and possessed excellent in vivo antitumor activity in the HCT116 xenograft model (TGI = 75.2%, 150 mg/kg, p.o.) without significant toxicity, which was more potent than HDAC inhibitor vorinostat, TOP inhibitor evodiamine and their combination. Taken together, this study highlights the therapeutic advantages of evodiamine-based HDAC1/TOP2 dual inhibitors and provides valuable leads for the development of novel multi-targeting antitumor agents.

Nicotinamide Phosphoribosyltransferase (NAMPT) Is a New Target of Antitumor Agent Chidamide

Chidamide is a histone deacetylase (HDAC) inhibitor that is currently used to treat cutaneous T-cell lymphoma in clinic. Herein nicotinamide phosphoribosyltransferase (NAMPT) was identified to be a new target of chidamide on the basis of the pharmacophore analysis, molecular docking, biological assays, inhibitor design, and structure-activity relationship study. The polypharmacology of chidamide will provide important information for better understanding its antitumor mechanism. Also, design of dual NAMPT/HDAC inhibitors may serve as an effective strategy to develop novel antitumor agents.

Homology modeling of human histone deacetylase 10 and design of potential selective inhibitors

Histone deacetylases (HDACs) are implicated in the pathology of various cancers, and their pharmacological blockade has proven to be promising in reversing the malignant phenotypes. However, lack of crystal structures of some of the human HDAC isoforms (e.g., HDAC10) hinders the design of the isoform-selective inhibitor. Here, the recently solved X-ray crystal structure of Danio rerio (zebrafish) HDAC10 (Protein Data Bank (PDB) ID; 5TD7, released on 24 May 2017) was retrieved from the PDB and used as a template structure to model the three-dimensional structure of human HDAC10. The overall quality of the best model (M0017) was assessed by computing its z-score-a measure of the deviation of the total energy of the structure with respect to an energy distribution derived from random conformations and by docking of known HDAC10 inhibitors to its catalytic cavity. Furthermore, to identify potential HDAC10-selective inhibitor ligand-based virtual screening was carried out against the ZINC database. The free modeled structure of HDAC10 and its complexes with quisinostat and the highest-ranked compound ZINC19749069 were submitted to molecular dynamics simulation. The comparative analysis of root-mean-squared deviation, root-mean-squared fluctuation, radius of gyration (Rg), and potential energy of these systems showed that HDAC10-ZINC19749069 complex remained the most stable over time. Thus, M0017 could be potentially used for structure-based inhibitor against HDAC10, and ZINC19749069 may provide a scaffold for further optimization. Communicated by Ramaswamy H. Sarma.

Compounds targeting class II histone deacetylases do not cause panHDACI-associated impairment of megakaryocyte differentiation

Histone deacetylase inhibitors (HDACIs) have demonstrated effectiveness against lymphomas and myelomas in clinical practice. However, common to all currently approved broad-acting HDACIs (panHDACIs) is dose-limiting thrombocytopenia, which has prevented wider use in cancer therapy. Using CD34⁺ hematopoietic stem cells (HSCs), we show that megakaryocyte (MK) cell maturation and differentiation are impaired by panHDACIs, correlating to clinical thrombocytopenia. Importantly, we demonstrate that inhibitors of class II histone deacetylases (HDACs), including LMK235 and tubacin at clinically relevant concentrations, do not affect MK maturation. Furthermore, we show that HDACI-induced impairment of MK differentiation is associated with reduction of protein levels of the transcription factor GATA-1, but not tubulin hyperacetylation. Finally, we report that panHDACIs trigger a rapid loss of GATA-1 protein via a proteasome-dependent pathway. Our data support the notion that specifically targeting class II HDACs in cancer treatment is a potential strategy that would offer a safer alternative than current panHDACIs.

The Safety Profile of Concurrent Therapy for Multiple Myeloma in the Modern Era

Purpose

The management of multiple myeloma has evolved in the modern era, partially owing to the increasing number of biologic therapeutics. Nonetheless, radiation remains an important treatment in the management of painful lytic lesions from multiple myeloma. The goal of this study is to evaluate the side effect profile of radiation therapy (RT) while patients are concurrently treated with biologic agents.

Methods and Materials

We conducted a retrospective study based on data collected from patients receiving RT at our institute from 2007 to 2017. A total of 130 patients (279 treatment sites) were included in this study with a median follow-up time of 14 months. Patients were required to be receiving a biological agent at least within 1 month before starting and up to 1 month after RT. Generalized estimating equations with a log link function and binomial distribution were used to estimate the prevalence ratio (PR) and corresponding 95% confidence interval (CI) and compare the side effects between patients with RT alone and RT + biologic agent.

Results

The median age of all patients in our cohort was 64 years, with 53 men (58.9%) and 37 women (41.1%). The mean Karnofsky performance status score of all cohorts was 80. No significant difference in incidence of acute (PR: 1.33; 95% CI, 0.80-2.22; P = .2660) or subacute (PR: 0.90; 95% CI, 0.49-1.67; P = .7464) toxicities was found between patients with or without biologic agents who were treated concurrently with RT. No significant difference was found in reduction in laboratory values between patients with or without biologic agents treated concurrently with RT for white blood cells (P = .6916), platelets (P = .7779), or hematocrit (P = .0858).

Conclusions

Our study did not detect any significant toxicity rates from palliative radiation while patients were concurrently treated with biologic agents.

Discovery of Janus Kinase 2 (JAK2) and Histone Deacetylase (HDAC) Dual Inhibitors as a Novel Strategy for the Combinational Treatment of Leukemia and Invasive Fungal Infections

Clinically, leukemia patients often suffer from the limited efficacy of chemotherapy and high risks of infection by invasive fungal pathogens. Herein, a novel therapeutic strategy was developed in which a small molecule can simultaneously treat leukemia and invasive fungal infections (IFIs). Novel Janus kinase 2 (JAK2) and histone deacetylase (HDAC) dual inhibitors were identified to possess potent anti-proliferative activity toward hematological cell lines and excellent synergistic effects with fluconazole to treat resistant Candida albicans infections. In particular, compound 20a, a highly active and selective JAK2/HDAC6 dual inhibitor, showed excellent in vivo antitumor efficacy in several acute myeloid leukemia (AML) models and synergized with fluconazole for the treatment of resistant C. albicans infections. This study highlights the therapeutic potential of JAK2/HDAC dual inhibitors in treating AML and IFIs and provides an efficient strategy for multitargeting drug discovery.

The HDAC inhibitor panobinostat (LBH589) exerts in vivo anti-leukaemic activity against MLL-rearranged acute lymphoblastic leukaemia and involves the RNF20/RNF40/WAC-H2B ubiquitination axis

MLL-rearranged acute lymphoblastic leukaemia (ALL) represents an aggressive malignancy in infants (<1 year of age), associated with poor outcome. Current treatment intensification is not further possible, and novel therapy strategies are needed. Notably, MLL-rearranged ALL is characterised by a strongly deregulated epigenome and shows sensitivity to epigenetic perturbators. Here we demonstrate the in vivo efficacy of the histone deacetylase inhibitor panobinostat (LBH589) using xenograft mouse models of MLL-rearranged ALL. Panobinostat monotherapy showed strong anti-leukaemic effects, extending survival and reducing overall disease burden. Comprehensive molecular analyses in vitro showed that this anti-leukaemic activity involves depletion of H2B ubiquitination via suppression of the RNF20/RNF40/WAC E3 ligase complex; a pivotal pathway for MLL-rearranged leukaemic maintenance. Knockdown of WAC phenocopied loss of H2B ubiquitination and concomitant cell death induction. These combined data demonstrate that panobinostat cross-inhibits multiple epigenetic pathways, ultimately contributing to its highly efficacious targeting of MLL-rearranged ALL.

Dual NAMPT/HDAC Inhibitors as a New Strategy for Multitargeting Antitumor Drug Discovery

Novel dual nicotinamide phosphoribosyltransferase (NAMPT) and histone deacetylase (HDAC) inhibitors were designed by a pharmacophore fusion approach. The thiazolocarboxamide inhibitors were highly active for both targets. In particular, compound 7f (NAMPT IC₅₀ = 15 nM, HDAC1 IC₅₀ = 2 nM) showed potent in vivo antitumor efficacy in the HCT116 xenograft model. The study offers a new strategy for multitarget antitumor drug discovery by simultaneously acting on cancer metabolism and epigenetics.

Image-based drug screen identifies HDAC inhibitors as novel Golgi disruptors synergizing with JQ1

The Golgi apparatus is increasingly recognized as a major hub for cellular signaling and is involved in numerous pathologies, including neurodegenerative diseases and cancer. The study of Golgi stress-induced signaling pathways relies on the selectivity of the available tool compounds of which currently only a few are known. To discover novel Golgi-fragmenting agents, transcriptomic profiles of cells treated with brefeldin A, golgicide A, or monensin were generated and compared with a database of gene expression profiles from cells treated with other bioactive small molecules. In parallel, a phenotypic screen was performed for compounds that alter normal Golgi structure. Histone deacetylase (HDAC) inhibitors and DNA-damaging agents were identified as novel Golgi disruptors. Further analysis identified HDAC1/HDAC9 as well as BRD8 and DNA-PK as important regulators of Golgi breakdown mediated by HDAC inhibition. We provide evidence that combinatorial HDACi/(+)-JQ1 treatment spurs synergistic Golgi dispersal in several cancer cell lines, pinpointing a possible link between drug-induced toxicity and Golgi morphology alterations.

A Phase I/II Trial of Panobinostat in Combination With Lenalidomide in Patients With Relapsed or Refractory Hodgkin Lymphoma

BACKGROUND

Lenalidomide and panobinostat have shown single-agent efficacy of 14% to 50% and 27% to 58%, respectively, in Hodgkin lymphoma (HL). This phase I/II study was conducted to determine the maximum tolerated dose (MTD), safety, and efficacy of lenalidomide combined with panobinostat in relapsed/refractory HL.

PATIENTS AND METHODS

In the phase I trial, previously treated patients with classical or lymphocyte-predominant HL received escalating doses of lenalidomide on days 1 to 21 and panobinostat 3 times a week (TIW) every 28 days. Dose-limiting toxicity (DLT) was defined during cycle 1. When the MTD was determined, a phase II study was conducted to determine overall response (OR).

RESULTS

Twenty-four patients enrolled; 11 in the phase I and 13 in phase II portions. No DLTs were observed but 2 patients who received 25 mg lenalidomide and 20 mg panobinostat experienced neutropenia and thrombocytopenia > 14 days in cycle 2, leading to selection of 25 mg lenalidomide on days 1 to 21 and 15 mg panobinostat TIW for the phase II dose. In all 24 patients, Grade 3 to 4 toxicities consisted of neutropenia (58%), thrombocytopenia (42%), lymphopenia (25%), and febrile neutropenia (25%). OR was 16.7% (2 complete response [CR] and 2 partial response). One patient with CR had lymphocyte-predominant HL and received 22 cycles. Median progression-free survival and overall survival were 3.8 and 16.4 months, respectively.

CONCLUSION

Although the combination of panobinostat and lenalidomide appears safe in patients with relapsed/refractory HL, the limited efficacy and significant rates of neutropenia and febrile neutropenia observed do not support further evaluation of this combination in HL.

Synergistic activity of vorinostat combined with gefitinib but not with sorafenib in mutant KRAS human non-small cell lung cancers and hepatocarcinoma

Development of drug resistance limits the efficacy of targeted therapies. Alternative approaches using different combinations of therapeutic agents to inhibit several pathways could be a more effective strategy for treating cancer. The effects of the approved epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (gefitinib) or a multi-targeted kinase inhibitor (sorafenib) in combination with a histone deacetylase inhibitor (vorinostat) on cell proliferation, cell cycle distribution, apoptosis, and signaling pathway activation in human lung adenocarcinoma and hepatocarcinoma cells with wild-type EGFR and mutant KRAS were investigated. The effects of the synergistic drug combinations were also studied in human lung adenocarcinoma and hepatocarcinoma cells in vivo. The combination of gefitinib and vorinostat synergistically reduced cell growth and strongly induced apoptosis through inhibition of the insulin-like growth factor-1 receptor/protein kinase B (IGF-1R/AKT)-dependent signaling pathway. Moreover, the gefitinib and vorinostat combination strongly inhibited tumor growth in mice with lung adenocarcinoma or hepatocarcinoma tumor xenografts. In contrast, the combination of sorafenib and vorinostat did not inhibit cell proliferation compared to a single treatment and induced G₂/M cell cycle arrest without apoptosis. The sorafenib and vorinostat combination sustained the IGF-1R-, AKT-, and mitogen-activated protein kinase-dependent signaling pathways. These results showed that there was synergistic cytotoxicity when vorinostat was combined with gefitinib for both lung adenocarcinoma and hepatocarcinoma with mutant KRAS in vitro and in vivo but that the combination of vorinostat with sorafenib did not show any benefit. These findings highlight the important role of the IGF-1R/AKT pathway in the resistance to targeted therapies and support the use of histone deacetylase inhibitors in combination with EGFR-tyrosine kinase inhibitors, especially for treating patients with mutant KRAS resistant to other treatments.