The potential of panobinostat as a treatment option in patients with relapsed and refractory multiple myeloma

Search for novel Plasmodium falciparum PfATP4 inhibitors from the MMV Pandemic Response Box through a virtual screening approach

Owing to its life cycle involving multiple hosts and species-specific biological complexities, a vaccine against Plasmodium, the causative agent of Malaria remains elusive. This makes chemotherapy the only viable means to address the clinical manifestations and spread of this deadly disease. However, rapid surge in antimalarial resistance poses significant challenges to our efforts to eliminate Malaria since the best drug available to-date; Artemisinin and its combinations are also rapidly losing efficacy. Sodium ATPase (PfATP4) of Plasmodium has been recently explored as a suitable target for new antimalarials such as Cipargamin. Prior studies showed that multiple compounds from the Medicines for Malaria Venture (MMV) chemical libraries were efficient PfATP4 inhibitors. In this context, we undertook a structure- based virtual screening approach combined to Molecular Dynamic (MD) simulations to evaluate whether new molecules with binding affinity towards PfATP4 could be identified from the Pandemic Response Box (PRB), a 400-compound library of small molecules launched in 2019 by MMV. Our analysis identified new molecules from the PRB library that showed affinity for distinct binding sites including the previously known G358 site, several of which are clinically used anti-bacterial (MMV1634383, MMV1634402), antiviral (MMV010036, MMV394033) or antifungal (MMV1634494) agents. Therefore, this study highlights the possibility of exploiting PRB molecules against Malaria through abrogation of PfATP4 activity.Communicated by Ramaswamy H. Sarma.

Therapeutic Targeting of Hypoxia-Inducible Factors in Cancer

In the realm of cancer therapeutics, targeting the hypoxia-inducible factor (HIF) pathway has emerged as a promising strategy. This study delves into the intricate web of HIF-associated mechanisms, exploring avenues for future anticancer therapies. Framing the investigation within the broader context of cancer progression and hypoxia response, this article aims to decipher the pivotal role played by HIF in regulating genes influencing angiogenesis, cell proliferation, and glucose metabolism. Employing diverse approaches such as HIF inhibitors, anti-angiogenic therapies, and hypoxia-activated prodrugs, the research methodologically intervenes at different nodes of the HIF pathway. Findings showcase the efficacy of agents like EZN-2968, Minnelide, and Acriflavine in modulating HIF-1α protein synthesis and destabilizing HIF-1, providing preliminary proof of HIF-1α mRNA modulation and antitumor activity. However, challenges, including toxicity, necessitate continued exploration and development, as exemplified by ongoing clinical trials. This article concludes by emphasizing the potential of targeted HIF therapies in disrupting cancer-related signaling pathways.

The Combination of Panobinostat and Melphalan for the Treatment of Patients with Multiple Myeloma

Histone deacetylase inhibitors show synergy with several genotoxic drugs. Herein, we investigated the biological impact of the combined treatment of panobinostat and melphalan in multiple myeloma (MM). DNA damage response (DDR) parameters and the expression of DDR-associated genes were analyzed in bone marrow plasma cells (BMPCs) and peripheral blood mononuclear cells (PBMCs) from 26 newly diagnosed MM patients. PBMCs from 25 healthy controls (HC) were examined in parallel. Compared with the ex vivo melphalan-only treatment, combined treatment with panobinostat and melphalan significantly reduced the efficiency of nucleotide excision repair (NER) and double-strand-break repair (DSB/R), enhanced the accumulation of DNA lesions (monoadducts and DSBs), and increased the apoptosis rate only in patients’ BMPCs (all p < 0.001); marginal changes were observed in PBMCs from the same patients or HC. Accordingly, panobinostat pre-treatment decreased the expression levels of critical NER (DDB2, XPC) and DSB/R (MRE11A, PRKDC/DNAPKc, RAD50, XRCC6/Ku70) genes only in patients’ BMPCs; no significant changes were observed in PBMCs from patients or HC. Together, our findings demonstrate that panobinostat significantly increased the melphalan sensitivity of malignant BMPCs without increasing the melphalan sensitivity of PBMCs from the same patients, thus paving the way for combination therapies in MM with improved anti-myeloma efficacy and lower side effects.

Mechanisms underlying synergism between circularized tumor necrosis factor-related apoptosis inducing ligand and bortezomib in bortezomib-sensitive or -resistant myeloma cells

Mechanisms underlying interactions between a novel, clinically relevant circularized tumor necrosis factor-related apoptosis inducing ligand (TRAIL) agonist, circularly permuted TRAIL (CPT) have been examined in multiple myeloma (MM) cells sensitive or resistant to bortezomib (BTZ). Various MM cell lines for example, U266, including those resistant to bortezomib-resistant U266 cells were exposed to low nanomolar concentrations of bortezomib ± CPT and apoptosis monitored. Circularly permuted TRAIL and bortezomib synergistically induced apoptosis in both BTZ-naïve and -resistant cells. The regimen up-regulated DR4 receptor internalization in MM cells, known to modulate both NF-κB and extrinsic apoptotic pathways. CPT/BTZ disrupted the non-canonical NF-κB pathway, reflected by tumor necrosis factor (TNF) receptor associated factors 3 (TRAF3) up-regulation, NF-κB inducing kinase down-regulation, diminished p52 and p50 processing, and B-cell lymphoma-extra large (BCL-XL) down-regulation, but failed to inactivate the canonical NF-κB pathway, reflected by unchanged or increased expression of phospho-p65. The regimen also sharply increased extrinsic apoptotic pathway activation. Cells exhibiting TRAF3 knock-down, dominant-negative Fas-associated protein with death domain, knock-down of caspase-8, BCL-2/BCL-XL, or exposure to a caspase-9 inhibitor displayed markedly reduced CPT/BTZ sensitivity. Concordant results were observed in bortezomib-resistant cells. The regimen was also active in the presence of stromal cells and was relatively sparing toward normal CD34+ hematopoietic cells. Finally, ex vivo results revealed synergism in primary MM primary cells, including those BTZ, and the CPT/BTZ regimen significantly decreased tumor growth in a patient-derived MM xenograft model. These results indicate that the CPT/BTZ regimen acts via the non-canonical NF-κB as well as intrinsic/extrinsic apoptotic pathways to induce cell death in MM cells, and may represent an effective strategy in the setting of bortezomib resistance.

Potential of histone deacetylase inhibitors in the control and regulation of prostate, breast and ovarian cancer

Histone deacetylases (HDACs) are enzymes that play a role in chromatin remodeling and epigenetics. They belong to a specific category of enzymes that eliminate the acetyl part of the histones’ -N-acetyl lysine, causing the histones to be wrapped compactly around DNA. Numerous biological processes rely on HDACs, including cell proliferation and differentiation, angiogenesis, metastasis, gene regulation, and transcription. Epigenetic changes, specifically increased expression and activity of HDACs, are commonly detected in cancer. As a result, HDACi could be used to develop anticancer drugs. Although preclinical outcomes with HDACs as monotherapy have been promising clinical trials have had mixed results and limited success. In both preclinical and clinical trials, however, combination therapy with different anticancer medicines has proved to have synergistic effects. Furthermore, these combinations improved efficacy, decreased tumor resistance to therapy, and decreased toxicity. In the present review, the detailed modes of action, classification of HDACs, and their correlation with different cancers like prostate, breast, and ovarian cancer were discussed. Further, the different cell signaling pathways and the structure-activity relationship and pharmaco-toxicological properties of the HDACi, and their synergistic effects with other anticancer drugs observed in recent preclinical and clinical studies used in combination therapy were discussed for prostate, breast, and ovarian cancer treatment.

Multiple Myeloma: Possible Cure from the Sea

Simple Summary

Multiple myeloma (MM) is a complex white blood cell (plasma cell, PC) cancer. The aetiology of MM is still unknown, and it is still an incurable disease despite efforts by the scientific community. The high level of PC genetic heterogeneity renders MM a complex puzzle to be solved. Combinations of drugs are generally used to treat MM patients, with a general increase in overall survival. Relapsed and refractory MM patients are the generation of patients who resist or do not respond to first-line therapy and need additional treatments. Exploring new sources, such as marine organisms, for drug discovery is fundamental to fighting MM. Various studies have shown that marine natural products (MNPs) might have antiproliferative and cancer-specific cytotoxic properties, giving MNPs a pivotal role in anticancer drug discovery. This review recaps updated frontline treatment options, including new ones developed from MNP research.

Abstract

Multiple myeloma (MM) is a blood cancer that occurs in the plasma cells (PCs), a type of white blood cell. Despite the progress of several current treatments that prolong the overall patient’s survival, most MM cases are incurable. For this reason, many efforts have been undertaken by the scientific community in the search for new treatments. BLENREP^TM and Aplidin^® are two marine-derived drugs currently in use for MM. In addition, other natural products have been identified from marine organisms, tested for their possible anticancer properties, and are in preclinical or clinical trials for MM, including cytarabine, a compound in use for leukaemia treatment. Between the most successful marine compounds in fighting MM, there are molecules with specific targets, such as the elongation factor 1-alpha 2 and proteasome inhibitors, and compounds conjugated with antibodies that recognise specific cell types and direct the drug to the correct cell target. Active compounds belong to different chemical classes, from cyclic peptides to alkaloids, highlighting the importance of screening the plethora of compounds produced by marine organisms. In this review, we summarise the current state of art of MM therapies focusing on the marine natural product emerging roles.

Co-Delivery of CPT-11 and Panobinostat with Anti-GD2 Antibody Conjugated Immunoliposomes for Targeted Combination Chemotherapy

Simple Summary

In targeted cancer therapies, liposomes conjugated with antibody (Ab) can selectively deliver drugs to antigen-expressing cancer cells through active targeting and improve anti-cancer efficacy. Many glioblastoma cell lines and primary biopsies express high levels of disialoganglioside GD2 antigen, making it an excellent candidate for targeted cancer therapy. In this study, we prepared anti-GD2 Ab conjugated immunoliposomes (ImmuLipCP) for co-delivery of CPT-11 and panobinostat, which is intended for combination targeted chemotherapy. To compare the GD2 targeting mechanism, we used glioma cells with low GD2 expression (U87MG) and its drug-resistant variant with high GD2 expression (U87 DR). We demonstrate that ImmuLipCP show enhanced cytotoxicity against U87DR through Ab-mediated intracellular trafficking and drug delivery, for synergistic cancer cell killing effects. Using a xenograft tumor model by subcutaneous implantation of U87DR in nude mice, we also validate the targeting and anti-cancer efficacy of ImmuLipCP in vivo.

Abstract

The consistent expression of disialoganglioside GD2 in neuroblastoma tumor cells and its restricted expression in normal tissues open the possibility to use it for molecularly targeted neuroblastoma therapy. On the other hand, immunoliposomes combining antibody-mediated tumor recognition with liposomal delivery of chemotherapeutics have been proved to enhance therapeutic efficacy in brain tumors. Therefore, we develop immunoliposomes (ImmuLipCP) conjugated with anti-GD2 antibody, for targeted co-delivery of CPT-11 and panobinostat in this study. U87MG human glioma cell line and its drug resistant variant (U87DR), which were confirmed to be associated with low and high expression of cell surface GD2, were employed to compare the targeting efficacy. From in vitro cytotoxicity assay, CPT-11 showed synergism drug interaction with panobinostat to support co-delivery of both drugs with ImmuLipCP for targeted synergistic combination chemotherapy. The molecular targeting mechanism was elucidated from intracellular uptake efficacy by confocal microscopy and flow cytometry analysis, where 6-fold increase in liposome and 1.8-fold increase in drug uptake efficiency was found using targeted liposomes. This enhanced intracellular trafficking for drug delivery endows ImmuLipCP with pronounced cytotoxicity toward U87DR cells in vitro, with 1.6-fold increase of apoptosis rate. Using xenograft nude mice model with subcutaneously implanted U87DR cells, we observe similar biodistribution profile but 5.1 times higher accumulation rate of ImmuLip from in vivo imaging system (IVIS) observation of Cy5.5-labelled liposomes. Taking advantage of this highly efficient GD-2 targeting, ImmuLipCP was demonstrated to be an effective cancer treatment modality to significantly enhance the anti-cancer therapeutic efficacy in U87DR tumors, shown from the significant reduced tumor size in and prolonged survival time of experiment animals as well as diminished expression of cell proliferation and enhanced expression of apoptosis marker proteins in tumor section.

Updated Understanding of Cancer as a Metabolic and Telomere-Driven Disease, and Proposal for Complex Personalized Treatment, a Hypothesis

In this review, we propose a holistic approach to understanding cancer as a metabolic disease. Our search for relevant studies in medical databases concludes that cancer cells do not evolve directly from normal healthy cells. We hypothesize that aberrant DNA damage accumulates over time-avoiding the natural DNA controls that otherwise repair or replace the rapidly replicating cells. DNA damage starts to accumulate in non-replicating cells, leading to senescence and aging. DNA damage is linked with genetic and epigenetic factors, but the development of cancer is favored by telomerase activity. Evidence indicates that telomere length is affected by chronic inflammations, alterations of mitochondrial DNA, and various environmental factors. Emotional stress also influences telomere length. Chronic inflammation can cause oxidative DNA damage. Oxidative stress, in turn, can trigger mitochondrial changes, which ultimately alter nuclear gene expression. This vicious cycle has led several scientists to view cancer as a metabolic disease. We have proposed complex personalized treatments that seek to correct multiple changes simultaneously using a psychological approach to reduce chronic stress, immune checkpoint therapy with reduced doses of chemo and radiotherapy, minimal surgical intervention, if any, and mitochondrial metabolic reprogramming protocols supplemented by intermittent fasting and personalized dietary plans without interfering with the other therapies.

Temporal expression of MOF acetyltransferase primes transcription factor networks for erythroid fate

Self-renewal and differentiation of hematopoietic stem cells (HSCs) are orchestrated by the combinatorial action of transcription factors and epigenetic regulators. Here, we have explored the mechanism by which histone H4 lysine 16 acetyltransferase MOF regulates erythropoiesis. Single-cell RNA sequencing and chromatin immunoprecipitation sequencing uncovered that MOF influences erythroid trajectory by dynamic recruitment to chromatin and its haploinsufficiency causes accumulation of a transient HSC population. A regulatory network consisting of MOF, RUNX1, and GFI1B is critical for erythroid fate commitment. GFI1B acts as a Mof activator which is necessary and sufficient for cell type-specific induction of Mof expression. Plasticity of Mof-depleted HSCs can be rescued by expression of a downstream effector, Gata1, or by rebalancing acetylation via a histone deacetylase inhibitor. Accurate timing and dosage of Mof expression act as a rheostat for the feedforward transcription factor network that safeguards progression along the erythroid fate.

Phase I study of the mTOR inhibitor everolimus in combination with the histone deacetylase inhibitor panobinostat in patients with advanced clear cell renal cell carcinoma

Background Preclinical studies suggested synergistic anti-tumor activity when pairing mTOR inhibitors with histone deacetylase (HDAC) inhibitors. We completed a phase I, dose-finding trial for the mTOR inhibitor everolimus combined with the HDAC inhibitor panobinostat in advanced clear cell renal cell carcinoma (ccRCC) patients. We additionally investigated expression of microRNA 605 (miR-605) in serum samples obtained from trial participants. Patients and Methods Twenty-one patients completed our single institution, non-randomized, open-label, dose-escalation phase 1 trial. miR-605 levels were measured at cycle 1/day 1 (C1D1) and C2D1. Delta Ct method was utilized to evaluate miR-605 expression using U6B as an endogenous control. Results There were 3 dosing-limiting toxicities (DLTs): grade 4 thrombocytopenia (n = 1), grade 3 thrombocytopenia (n = 1), and grade 3 neutropenia (n = 1). Everolimus 5 mg PO daily and panobinostat 10 mg PO 3 times weekly (weeks 1 and 2) given in 21-day cycles was the recommended phase II dosing based on their maximum tolerated dose. The 6-month progression-free survival was 31% with a median of 4.1 months (95% confidence internal; 2.0-7.1). There was higher baseline expression of miR-605 in patients with progressive disease (PD) vs those with stable disease (SD) (p = 0.0112). PD patients' miR-605 levels decreased after the 1st cycle (p = 0.0245), whereas SD patients' miR-605 levels increased (p = 0.0179). Conclusion A safe and tolerable dosing regimen was established for combination everolimus/panobinostat therapy with myelosuppression as the major DLT. This therapeutic pairing did not appear to improve clinical outcomes in our group of patients with advanced ccRCC. There was differential expression of miR-605 that correlated with treatment response. Clinical trial information: NCT01582009.

Pixantrone demonstrates significant in vitro activity against multiple myeloma and plasma cell leukemia

Treatment results for multiple myeloma and plasma cell leukemia have considerably improved, but cure remains elusive and establishing new therapeutic approaches constitutes a major unmet clinical need. We analyzed the anti-myeloma properties of the aza-anthracenedione pixantrone which has been successfully used in a phase III study for the treatment of patients with aggressive non-Hodgkin's lymphoma as monotherapy as well as in combination regimes in vitro and in an adapted in vivo model (ex ovo chicken chorioallantoic membrane (CAM) assay). Pixantrone significantly inhibited proliferation and metabolic activity of all investigated myeloma cell lines. Importantly, anti-myeloma effects were more pronounced in tumor cell lines than in stromal cells, mesenchymal stem cells, and peripheral blood mononuclear cells of healthy controls. Apoptosis of myeloma cell lines was observed only after a 7-day incubation period, indicating a fast cytostatic and a slower cytotoxic effect of this drug. Pixantrone reduced the viability of primary plasma cells of patients and induced downregulation of myeloma-cell growth in the CAM assay. Additionally, we demonstrate in vitro synergism between pixantrone and the histone deacetylase inhibitor panobinostat with respect to its anti-proliferative features. From these data, we conclude that systematic investigations of the clinical usefulness of pixantrone in the framework of controlled clinical trials are clearly indicated (e.g., in penta-refractory patients).

Design of Potent Panobinostat Histone Deacetylase Inhibitor Derivatives: Molecular Considerations for Enhanced Isozyme Selectivity between HDAC2 and HDAC8

Histone Deacetylases (HDACs) are an important family of 18 isozymes, which are being pursued as drug targets for many types of disorders. HDAC2 and HDAC8 are two of the isozymes, which have been identified as drug targets for the design of anti-cancer, neurodegenerative, immunological, and anti-parasitic agents. Design of potent HDAC2 and HDAC8 inhibitors will be useful for the therapeutic advances in many disorders. This work was undertaken to develop potent HDAC2 and HDAC8 inhibitors. A docking study was performed comparing panobinostat derivatives in both HDAC2 and HDAC8. Six of our derivatives showed stronger binding to HDAC2 than panobinostat, and two of our derivatives showed stronger binding to HDAC8 than panobinostat. We evaluated the molecular features, which improved potency of our inhibitors over panobinostat and also identified another molecular consideration, which could be used to enhance histone deacetylase inhibitor (HDACi) selectivity towards either the HDAC2 or HDAC8 isozymes. The results of this work can be used to assist future design of more potent and selective HDACi for HDAC2 and HDAC8.

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.

The histone deacetylase inhibitor panobinostat is a potent antitumor agent in canine diffuse large B-cell lymphoma

Non-Hodgkin lymphoma (NHL) is one of the most common causes of cancer-related death in the United States and Europe. Although the outcome of NHL patients has improved over the last years with current therapies, the rate of mortality is still high. A plethora of new drugs is entering clinical development for NHL treatment; however, the approval of new treatments remains low due in part to the paucity of clinically relevant models for validation. Canine lymphoma shares remarkable similarities with its human counterpart, making the dog an excellent animal model to explore novel therapeutic molecules and approaches. Histone deacetylase inhibitors (HDACis) have emerged as a powerful new class of anti-cancer drugs for human therapy. To investigate HDACi antitumor properties on canine diffuse large B-cell lymphoma, a panel of seven HDACi compounds (CI-994, panobinostat, SBHA, SAHA, scriptaid, trichostatin A and tubacin) was screened on CLBL-1 canine B-cell lymphoma cell line. Our results demonstrated that all HDACis tested exhibited dose-dependent inhibitory effects on proliferation of CLBL-1 cells, while promoting increased H3 histone acetylation. Amongst all HDACis studied, panobinostat proved to be the most promising compound and was selected for further in vitro and in vivo evaluation. Panobinostat cytotoxicity was linked to H3 histone and α-tubulin acetylation, and to apoptosis induction. Importantly, panobinostat efficiently inhibited CLBL-1 xenograft tumor growth, and strongly induced acetylation of H3 histone and apoptosis in vivo. In conclusion, these results provide new data validating HDACis and, especially, panobinostat as a novel anti-cancer therapy for veterinary applications, while contributing to comparative oncology.

Epigenetic Activation of Pro-angiogenic Signaling Pathways in Human Endothelial Progenitors Increases Vasculogenesis

Human endothelial colony-forming cells (ECFCs) represent a promising source of adult stem cells for vascular repair, yet their regenerative capacity is limited. Here, we set out to understand the molecular mechanism restricting the repair function of ECFCs. We found that key pro-angiogenic pathways are repressed in ECFCs due to the presence of bivalent (H3K27me3/H3K4me3) epigenetic marks, which decreases the cells' regenerative potential. Importantly, ex vivo treatment with a combination of epigenetic drugs that resolves bivalent marks toward the transcriptionally active H3K4me3 state leads to the simultaneous activation of multiple pro-angiogenic signaling pathways (VEGFR, CXCR4, WNT, NOTCH, SHH). This in turn results in improved capacity of ECFCs to form capillary-like networks in vitro and in vivo. Furthermore, restoration of perfusion is accelerated upon transplantation of drug-treated ECFCs in a model of hindlimb ischemia. Thus, ex vivo treatment with epigenetic drugs increases the vascular repair properties of ECFCs through transient activation of pro-angiogenic signaling pathways.

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Pro-angiogenic pathways are maintained in a poised state in ECFCs

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Epigenetic drugs resolve bivalently marked genes toward an active state in ECFCs

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Treatment with epigenetic drugs activates multiple pro-angiogenic pathways in ECFCs

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Ex vivo treatment with epigenetic drugs increases ECFC-mediated vasculogenesis

Acute Myeloid Leukemia: Advancements in Diagnosis and Treatment

OBJECTIVE

Leukemia is the most common pediatric malignancy and a major cause of morbidity and mortality in children. Among all subtypes, a lack of consensus exists regarding the diagnosis and treatment of acute myeloid leukemia (AML). Patient survival rates have remained modest for the past three decades in AML. Recently, targeted therapy has emerged as a promising treatment.

DATA SOURCES

We searched the PubMed database for recently published research papers on diagnostic development, target therapy, and other novel therapies of AML. Clinical trial information was obtained from ClinicalTrials.gov. For the major purpose of this review that is to outline the latest therapeutic development of AML, we only listed the ongoing clinical trials for reference. However, the published results of complete clinical trials were also mentioned.

STUDY SELECTION

This article reviewed the latest developments related to the diagnosis and treatment of AML. In the first portion, we provided some novel insights on the molecular basis of AML, as well as provided an update on the classification of AML. In the second portion, we summarized the results of research on potential molecular therapeutic agents including monoclonal antibodies, tyrosine kinase/Fms-like tyrosine kinase 3 (FLT3) inhibitors, epigenetic/demethylating agents, and cellular therapeutic agents. We will also highlight ongoing research and clinical trials in pediatric AML.

RESULTS

We described clonal evolution and how it changes our view on leukemogenesis, treatment responses, and disease relapse. Pediatric-specific genomic mapping was discussed with a novel diagnostic method highlighted. In the later portion of this review, we summarized the researches on potential molecular therapeutic agents including monoclonal antibodies, tyrosine kinase/FLT3 inhibitors, epigenetic/demethylating agents, and cellular therapeutic agents.

CONCLUSION

Gene sequencing techniques should set the basis for next-generation diagnostic methods of AML, and target therapy should be the focus of future clinical research in the exploration of therapeutic possibilities.

Panobinostat for the management of multiple myeloma

Multiple myeloma (MM) is the second most common blood cancer following non-Hodgkin's lymphoma. While the treatments for MM have improved over the past decade, for the most part, it remains an incurable disease. For this reason newer therapeutic agents are needed to combat this malignancy. Panobinostat is a pan-deacetylase inhibitor that impedes protein destruction by disturbing the enzymatic activity of deacetylases. It was US FDA approved in February 2015 for the management of relapsed/refractory MM in combination with bortezomib and dexamethasone. Several trials are ongoing, exploring the utility of panobinostat in various other settings for the management of MM. This review will detail the biology, clinical efficacy and potential future applications of panobinostat in the treatment of MM.

Panobinostat PK/PD profile in combination with bortezomib and dexamethasone in patients with relapsed and relapsed/refractory multiple myeloma

PURPOSE

Panobinostat, a potent pan-deacetylase inhibitor, improved progression-free survival (PFS) in patients with relapsed and refractory multiple myeloma when combined with bortezomib and dexamethasone in a phase 3 trial, PANORAMA-1. This study aims to explore exposure-response relationship for panobinostat in this combination in a phase 1 trial, B2207 and contrast with data from historical single-agent studies.

METHODS

Panobinostat plasma concentration-time profiles were obtained in patients from PANORAMA-1 (n = 12) and B2207 (n = 12) trials. Overall response rates (ORR) and major adverse events (AE) by panobinostat exposure were investigated in the B2207 trial. Panobinostat PK data from combination trials were contrasted with data from single-agent studies.

RESULTS

At maximum tolerated dose (MTD), the geometric mean of panobinostat area under curve from 0 to 24 h (AUC0-24) was 47.5 ng h/mL (77 % CV), and maximum plasma concentration (Cmax) was 8.1 ng/mL (90 % CV). These values were comparable with exposure data obtained in PANORAMA-1, but were 20 % lower than those without dexamethasone, and ∼ 50 % lower from single-agent trials, likely due to enzyme induction by dexamethasone. Higher levels of panobinostat exposure were associated with higher response rates and higher incidences of diarrhea and thrombocytopenia.

CONCLUSIONS

Apparent panobinostat exposure-AE and exposure-ORR relationships were observed when combined with bortezomib and dexamethasone in the treatment of patients with relapsed and refractory multiple myeloma. The addition of dexamethasone facilitated best response even though plasma exposure of panobinostat was reduced. Combination with a strong enzyme inducer should be avoided in future trials to prevent further reduction of panobinostat exposure.

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

Multiple myeloma is a malignancy involving plasma cell proliferation within the bone marrow. Survival of patients diagnosed with myeloma has significantly improved in the last decade, following the approval of novel agents. Despite great strides achieved in the management of multiple myeloma, it is still considered an incurable disease as the majority of patients relapse after initiation of therapy. Additionally, the duration of response generally decreases with an increasing number of therapy lines. The need to overcome resistance to therapy dictates research into more potent agents and those with novel mechanisms of action. A therapeutic option for relapsed/refractory myeloma includes histone deacetylase inhibition. Various histone deacetylase inhibitors, including the newly approved panobinostat, are currently under evaluation in this setting. Panobinostat for multiple myeloma is used in combination with other potent therapeutic agents, such as proteasome inhibitors and steroids. Ongoing research evaluating other panobinostat-containing regimens will provide additional insight into its place in myeloma management.

Dual-Mode HDAC Prodrug for Covalent Modification and Subsequent Inhibitor Release

Histone deacetylase inhibitors (HDACi) target abnormal epigenetic states associated with a variety of pathologies, including cancer. Here, the development of a prodrug of the canonical broad-spectrum HDACi suberoylanilide hydroxamic acid (SAHA) is described. Although hydroxamic acids are utilized universally in the development of metalloenzyme inhibitors, they are considered to be poor pharmacophores with reduced activity in vivo. We developed a prodrug of SAHA by appending a promoiety, sensitive to thiols, to the hydroxamic acid warhead (termed SAHA-TAP). After incubation of SAHA-TAP with an HDAC, the thiol of a conserved HDAC cysteine residue becomes covalently tagged with the promoiety, initiating a cascade reaction that leads to the release of SAHA. Mass spectrometry and enzyme kinetics experiments validate that the cysteine residue is covalently appended with the TAP promoiety. SAHA-TAP demonstrates cytotoxicity activity against various cancer cell lines. This strategy represents an original prodrug design with a dual mode of action for HDAC inhibition.