Olaparib hydroxamic acid derivatives as dual PARP and HDAC inhibitors for cancer therapy

Discovery of dual-targeted molecules based on Olaparib and Rigosertib for triple-negative breast cancer with wild-type BRCA

PARP inhibitors (PARPis) demonstrate significant potential efficacy in the clinical treatment of BRCA-mutated triple-negative breast cancer (TNBC). However, a majority of patients with TNBC do not possess BRCA mutations, and therefore cannot benefit from PARPis. Previous studies on multi-targeted molecules derived from PARPis or disruptors of RAF-RAF pathway have offered an alternative approach to develop novel anti-TNBC agents. Hence, to broaden the application of PARP inhibitors for TNBC patients with wild-type BRCA, a series of dual-targeted molecules were constructed via integrating the key pharmacophores of Olaparib (Ola) and Rigosertib into a single entity. Subsequent studies exhibited that the resulting compounds 13a-14c obtained potential anti-proliferative activity against BRCA-defected or wild-type TNBC cells. Among them, an optimal compound 13b showed good inhibitory activity toward PARP-1, displayed approximately 34-fold higher inhibitory activity than that of Ola in MDA-MB-231 cells, and exerted multi-functional mechanisms to induce apoptosis. Moreover, 13b displayed superior antitumor efficacy (TGI, 61.3 %) than the single administration of Ola (TGI, 38.5 %), 11b (TGI, 51.8 %) or even their combined administration (TGI, 56.7 %), but did not show significant systematic toxicity. These findings suggest that 13b may serve as a potential candidate for BRCA wild-type TNBC.

Poly(ADP-Ribose) Polymerase (PARP) Inhibitors for Cancer Therapy: Advances, Challenges, and Future Directions

Poly(ADP-ribose) polymerases (PARPs) are crucial nuclear proteins that play important roles in various cellular processes, including DNA repair, gene transcription, and cell death. Among the 17 identified PARP family members, PARP1 is the most abundant enzyme, with approximately 1-2 million molecules per cell, acting primarily as a DNA damage sensor. It has become a promising biological target for anticancer drug studies. Enhanced PARP expression is present in several types of tumors, such as melanomas, lung cancers, and breast tumors, correlating with low survival outcomes and resistance to treatment. PARP inhibitors, especially newly developed third-generation inhibitors currently undergoing Phase II clinical trials, have shown efficacy as anticancer agents both as single drugs and as sensitizers for chemo- and radiotherapy. This review explores the properties, characteristics, and challenges of PARP inhibitors, discussing their development from first-generation to third-generation compounds, more sustainable synthesis methods for discovery of new anti-cancer agents, their mechanisms of therapeutic action, and their potential for targeting additional biological targets beyond the catalytic active site of PARP proteins. Perspectives on green chemistry methods in the synthesis of new anticancer agents are also discussed.

Overview of class I HDAC modulators: Inhibitors and degraders

Class I histone deacetylases (HDACs) are closely associated with the development of a diverse array of diseases, including cancer, neurodegenerative disorders, HIV, and inflammatory diseases. Considering the essential roles in tumorigenesis, class I HDACs have emerged as highly desirable targets for therapeutic strategies, particularly in the field of anticancer drug development. However, the conventional class I HDAC inhibitors faced several challenges such as acquired resistance, inherent toxicities, and limited efficacy in inhibiting non-enzymatic functions of HDAC. To address these problems, novel strategies have emerged, including the development of class I HDAC dual-acting inhibitors, targeted protein degradation (TPD) technologies such as PROTACs, molecular glues, and HyT degraders, as well as covalent inhibitors. This review provides a comprehensive overview of class I HDAC enzymes and inhibitors, by initially introducing their structure and biological roles. Subsequently, we focus on the recent advancements of class I HDAC modulators, including isoform-selective class I inhibitors, dual-target inhibitors, TPDs, and covalent inhibitors, from the perspectives of rational design principles, pharmacodynamics, pharmacokinetics, and clinical progress. Finally, we also provide the challenges and outlines future prospects in the realm of class I HDAC-targeted drug discovery for cancer therapeutics.

Design, synthesis and antitumor activities of phthalazinone derivatives as PARP-1 inhibitors and PARP-1/HDAC-1 inhibitors

In recent years, poly(ADP-ribose)polymerase-1 (PARP-1) and histone deacetylase (HDAC) have emerged as significant targets in tumor therapy, garnering widespread attention. In this study, we designed and synthesized two novel phthalazinone PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors, named DLC-1-46 containing dithiocarboxylate fragments and DLC-47-63 containing hydroxamic acid fragments, and evaluated their inhibitory activities on enzymes and cells. Among the PARP-1 inhibitors, most compounds exhibited high inhibitory activity against the PARP-1 enzyme, with DLC-1-6 being particularly notable, showing IC50 values <0.2 nM. Notably, DLC-1 demonstrated significant anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells reaching 0.08, 26.39, and 1.01 μM, respectively. Further investigation revealed that DLC-1 arrested MDA-MB-231 cells in the G1 phase and induced apoptosis in a dose-dependent manner. Among the designed dual PARP-1/HDAC-1 inhibitors, several compounds exhibited potent dual-target inhibitory activity, with DLC-49 displaying IC50 values of 0.53 nM and 17 nM for PARP-1 and HDAC-1, respectively. DLC-50 demonstrated the most potent anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells at 0.30, 2.70, and 2.41 μM, respectively. Cell cycle arrest and apoptosis assays indicated that DLC-50 arrested the cell cycle in the G2 phase and induced apoptosis in HCT-116 cells. Our findings present a novel avenue for further exploration of PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors.

Small molecules targeting HDAC6 for cancer treatment: Current progress and novel strategies

Histone deacetylase 6 (HDAC6) plays a crucial role in the initiation and progression of various cancers, as its overexpression is linked to tumor growth, invasion, migration, survival, apoptosis, and angiogenesis. Therefore, HDAC6 has emerged as an attractive target for anticancer drug discovery in the past decade. However, the development of conventional HDAC6 inhibitors has been hampered by their limited clinical efficacy, acquired resistance, and inability to inhibit non-enzymatic functions of HDAC6. To overcome these challenges, new strategies, such as dual-acting inhibitors, targeted protein degradation (TPD) technologies (including PROTACs, HyT), are essential to enhance the anticancer activity of HDAC6 inhibitors. In this review, we focus on the recent advances in the design and development of HDAC6 modulators, including isoform-selective HDAC6 inhibitors, HDAC6-based dual-target inhibitors, and targeted protein degraders (PROTACs, HyT), from the perspectives of rational design, pharmacodynamics, pharmacokinetics, and clinical status. Finally, we discuss the challenges and future directions for HDAC6-based drug discovery for cancer therapy.

Combined strategies with PARP inhibitors for the treatment of BRCA wide type cancer

Genomic instability stands out as a pivotal hallmark of cancer, and PARP inhibitors (PARPi) emerging as a groundbreaking class of targeted therapy drugs meticulously crafted to inhibit the repair of DNA single-strand breaks(SSB) in tumor cells. Currently, PARPi have been approved for the treatment of ovarian cancer, pancreatic cancer, breast cancer, and prostate cancer characterized by homologous recombination(HR) repair deficiencies due to mutations in BRCA1/2 or other DNA repair associated genes and acquiring the designation of breakthrough therapy. Nonetheless, PARPi exhibit limited efficacy in the majority of HR-proficient BRCA1/2 wild-type cancers. At present, the synergistic approach of combining PARPi with agents that induce HR defects, or with chemotherapy and radiotherapy to induce substantial DNA damage, significantly enhances the efficacy of PARPi in BRCA wild-type or HR-proficient patients, supporting extension the use of PARPi in HR proficient patients. Therefore, we have summarized the effects and mechanisms of the combined use of drugs with PARPi, including the combination of PARPi with HR defect-inducing drugs such as ATRi, CHKi, HR indirectly inducing drugs like VEGFRi, CDKi, immune checkpoint inhibitors and drugs instigating DNA damage such as chemotherapy or radiotherapy. In addition, this review discusses several ongoing clinical trials aimed at analyzing the clinical application potential of these combined treatment strategies.

Dual-targeting class I HDAC inhibitor and ATM activator, SP-1-303, preferentially inhibits estrogen receptor positive breast cancer cell growth

Dual-targeting chromatin regulation and DNA damage repair signaling presents a promising avenue for cancer therapy. Applying rational drug design, we synthesized a potent dual-targeting small molecule, SP-1-303. Here, we report SP-1-303 as a class I isoform selective histone deacetylase (HDAC) inhibitor and an activator of the ataxia-telangiectasia mutated protein (ATM). In vitro enzymatic assays demonstrated selective inhibition of HDAC1 and HDAC3. Cellular growth inhibition studies show that SP-1-303 differentially inhibits growth of estrogen receptor positive breast cancer (ER+ BC) cells with effective growth inhibition concentrations (EC50) for MCF-7 and T47D cells ranging from 0.32 to 0.34 μM, compared to 1.2-2.5 μM for triple negative breast cancer cells, and ~12 μM for normal breast epithelial cells. Western analysis reveals that SP-1-303 decreases estrogen receptor alpha (ER-α) expression and increases p53 protein expression, while inducing the phosphorylation of ATM and its substrates, BRCA1 and p53, in a time-dependent manner in ER+ BC cells. Pharmacokinetic evaluation demonstrates an area under the curve (AUC) of 5227.55 ng/ml × h with an elimination half-life of 1.26 h following intravenous administration in a rat model. Collectively, SP-1-303 emerges as a novel second generation class I (HDAC1 and HDAC3) selective HDAC inhibitor, and ATM activator, capable of modulating ER expression, and inhibiting growth of ER+ BC cells. Combined targeting of class I HDACs and ATM by SP-1-303 offers a promising therapeutic approach for treating ER+ breast cancers and supports further preclinical evaluation.

Design, Synthesis, and Structure-Activity Relationship of Novel Pyridazinone-Based PARP7/HDACs Dual Inhibitors for Elucidating the Relationship between Antitumor Immunity and HDACs Inhibition

Histone deacetylases (HDACs) inhibitors such as vorinostat (SAHA) has been used to treat hematologic malignancies (rather than solid tumors) and have been found to suppress the JAK/STAT, a critical signal pathway for antitumor immunity, while PARP7 inhibitor RBN-2397 could activate the type I interferons (IFN-I) pathway, facilitating downstream effects such as STAT1 phosphorylation and immune activation. To elucidate whether simultaneous inhibition of these two targets could interfere with these two signal pathways, a series of pyridazinone-based PARP7/HDACs dual inhibitors have been designed, synthesized, and evaluated 7 inhibitor RBN-2397 could activate the type I interferons (IFN-I) pathway, facilitating downstream effects such as STAT1 phosphorylation and immune activation. To elucidate whether simultaneous inhibition of these two targets could interfere with these two signal pathways, a series of pyridazinone-based PARP7/HDACs dual inhibitors have been designed, synthesized, and evaluated in vitro and in vivo experiments. Compound 9l was identified as a potent and balanced dual inhibitor for the first time, exhibiting excellent antitumor capabilities both in vitro and in vivo. This suggests that 9l can be used as a valuable tool molecule for investigating the relationship between anticancer immunity and HDAC inhibition.

Emerging therapeutic strategies in cancer therapy by HDAC inhibition as the chemotherapeutic potent and epigenetic regulator

In developing new cancer medications, attention has been focused on novel epigenetic medicines called histone deacetylase (HDAC) inhibitors. Our understanding of cancer behavior is being advanced by research on epigenetics, which also supplies new targets for improving the effectiveness of cancer therapy. Most recently published patents emphasize HDAC selective drugs and multitarget HDAC inhibitors. Though significant progress has been made in emerging HDAC selective antagonists, it is urgently necessary to find new HDAC blockers with novel zinc-binding analogues to avoid the undesirable pharmacological characteristics of hydroxamic acid. HDAC antagonists have lately been explored as a novel approach to treating various diseases, including cancer. The complicated terrain of HDAC inhibitor development is summarized in this article, starting with a discussion of the many HDAC isotypes and their involvement in cancer biology, followed by a discussion of the mechanisms of action of HDAC inhibitors, their current level of development, effect of miRNA, and their combination with immunotherapeutic.

Novel dual inhibitors of PARP and HDAC induce intratumoral STING-mediated antitumor immunity in triple-negative breast cancer

PARP inhibitors and HDAC inhibitors have been approved for the clinical treatment of malignancies, but acquired resistance of or limited effects on solid tumors with a single agent remain as challenges. Bioinformatics analyses and a combination of experiments had demonstrated the synergistic effects of PARP and HDAC inhibitors in triple-negative breast cancer. A series of novel dual PARP and HDAC inhibitors were rationally designed and synthesized, and these molecules exhibited high enzyme inhibition activity with excellent antitumor effects in vitro and in vivo. Mechanistically, dual PARP and HDAC inhibitors induced BRCAness to restore synthetic lethality and promoted cytosolic DNA accumulation, which further activates the cGAS-STING pathway and produces proinflammatory chemokines through type I IFN-mediated JAK-STAT pathway. Moreover, these inhibitors promoted neoantigen generation, upregulated antigen presentation genes and PD-L1, and enhanced antitumor immunity when combined with immune checkpoint blockade therapy. These results indicated that novel dual PARP and HDAC inhibitors have antitumor immunomodulatory functions in triple-negative breast cancer. Novel dual PARP and HDAC inhibitors induce BRCAness to restore synthetic lethality, activating tumoral IFN signaling via the cGAS-STING pathway and inducing cytokine production, promoting neoantigen generation and presentation to enhance the immune response.

Small molecule tractable PARP inhibitors: Scaffold construction approaches, mechanistic insights and structure activity relationship

Diverse drug design strategies viz. molecular hybridization, substituent installation, scaffold hopping, isosteric replacement, high-throughput screening, induction and separation of chirality, structure modifications of phytoconstituents and use of structural templates have been exhaustively leveraged in the last decade to load the chemical toolbox of PARP inhibitors. Resultantly, numerous promising scaffolds have been pinpointed that in turn have led to the resuscitation of the credence to PARP inhibitors as cancer therapeutics. This review briefly presents the physiological functions of PARPs, the pharmacokinetics, and pharmacodynamics, and the interaction profiles of FDA-approved PARP inhibitors. Comprehensively covered is the section on the drug design strategies employed by drug discovery enthusiasts for furnishing PARP inhibitors. The impact of structural variations in the template of designed scaffolds on enzymatic and cellular activity (structure-activity relationship studies) has been discussed. The insights gained through the biological evaluation such as profiling of physicochemical properties andin vitroADME properties, PK assessments, and high-dose pharmacology are covered.

Identification of [1,2,4]Triazolo[4,3-a]pyrazine PARP1 inhibitors with overcome acquired resistance activities

Poly(ADP-ribose) polymerase 1 (PARP1) inhibitors can selectively kill homologous recombination (HR) deficient cancer cells and elicit anticancer effect through a mechanism of synthetic lethality. In this study, we designed, synthesized and pharmacologically evaluated a series of [1,2,4]triazolo[4,3-a]pyrazine derivatives as a class of potent PARP1 inhibitors. Among them, compounds 17m, 19a, 19c, 19e, 19i and 19k not only displayed more potent inhibitory activities (IC50s < 4.1 nM) than 9 and 1 against PARP1, but also exhibited nanomolar range of antiproliferative effects against MDA-MB-436 (BRCA1-/-, IC50s < 1.9 nM) and Capan-1 (BRCA2-/-, IC50s < 21.6 nM) cells. Notably, 19k significantly inhibited proliferation of resistant Capan-1 cells (IC50s < 0.3 nM). Collectively, the newly discovered PARP1 inhibitors act as a useful pharmacological tool for investigating the mechanism of acquired resistance to PARP1 inhibitors, and may also represent promising therapeutic agents for the treatment of HR deficient cancers with the potential to overcome the acquired resistance.

A review of progress in o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities for cancer therapy

Histone deacetylases, as a new class of anticancer targets, could maintain homeostasis by catalyzing histone deacetylation and play important roles in regulating the expression of target genes. Due to the fact that simultaneous intervention with dual tumor related targets could improve treatment effects, researches on innovative design of dual-target drugs are underway. HDAC is known as a "sensitizer" for the synergistic effects with other anticancer-target drugs because of its flexible structure design. The synergistic effects of HDAC inhibitor and other target inhibitors usually show enhanced inhibitory effects on tumor cells, and also provide new strategies to overcome multidrug resistance. Many research groups have reported that simultaneously inhibiting HDAC and other targets, such as tubulin, EGFR, could enhance the therapeutic effects. The o-aminobenzamide group is often used as a ZBG group in the design of HDAC inhibitors with potent antitumor effects. Given the prolonged inhibitory effects and reduced toxic side effects of HDAC inhibitors using o-aminobenzamide as the ZBG group, the o-aminobenzamide group is expected to become a more promising alternative to hydroxamic acid. In fact, o-aminobenzamide-based dual inhibitors of HDAC with different chemical structures have been extensively prepared and reported with synergistic and enhanced anti-tumor effects. In this work, we first time reviewed the rational design, molecular docking, inhibitory activities and potential application of o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities in cancer therapy, which might provide a reference for developing new and more effective anticancer drugs.

Study on the Multimodal Anticancer Mechanism of Ru(II)/Ir(III) Complexes Bearing a Poly(ADP-ribose) Polymerase 1 Inhibitor

A series of novel ruthenium(II) and iridium(III) complexes (Ru1-Ru3 and Ir1-Ir3) with different ancillary ligands and a PARP-1-inhibitory chelating ligand 2-(2,3-dibromo-4,5-dimethoxybenzylidene)hydrazine-1-carbothioamide (L1) were designed and prepared. The target complexes were structurally characterized by NMR and ESI-MS techniques. Among them, the crystal and molecular structures of Ir1 and Ir2 were also determined by X-ray crystallography. These complexes retained the PARP-1 enzyme inhibitory effect of L1 and showed potent antiproliferative activity on the tested cancer cell lines. The ruthenium(II) complexes Ru1-Ru3 were found to be more cytotoxic than the iridium(III) complexes Ir1-Ir3. Further investigations revealed that the most active complex Ru3 induced apoptosis in MCF-7 cells by multiple modes, inclusive of inducing DNA damage, suppressing DNA damage repair, disturbing cell cycle distribution, decreasing the mitochondrial membrane potential, and increasing the intracellular reactive oxygen species levels.

Discovery of dual PARP and CDK6 inhibitors for triple-negative breast cancer with wild-type BRCA

Inhibition of PARP is synthetic lethal with defects in BRCA, which provide effective targeted therapy strategy for BRCA mutation type of TNBC patients. However, approximately 80% of TNBC patients do not have BRCA mutations. Recent studies have shown that CDK4/6 inhibitors can increase the sensitivity of wild-type BRCA cells to PARP inhibitors. We designed a series of dual PARP and CDK6 inhibitors, and the most promising compound, P4i, showed good inhibitory activity against PARP1 and CDK6 and good inhibitory effects on MDA-MB-231 (IC50 = 1.96 μM), MDA-MB-468 (IC50 = 2.81 μM) and BT-549 (IC50 = 2.37 μM) cells with wild-type BRCA. Compared with Olaparib, the inhibition capacity of the three BRCA wild-type (MDA-MB-231, MDA-MB-468 and BT-549) cells was about 10-20 times higher, and even better than the combination of Olaparib and Palbociclib. As a novel PARP multifunctional molecule, it is a potential compound for the treatment of BRCA wild-type TNBC.

Prudent tactics to sail the boat of PARP inhibitors as therapeutics for diverse malignancies

INTRODUCTION

PARP inhibitors block the DNA-repairing mechanism of PARP and represent a promising class of anti-cancer therapy. The last decade has witnessed FDA approvals of several PARP inhibitors, with some undergoing advanced-stage clinical investigation. Medicinal chemists have invested much effort to expand the structure pool of PARP inhibitors. Issues associated with the use of PARP inhibitors that make their standing disconcerting in the pharmaceutical sector have been addressed via the design of new structural assemblages.

AREA COVERED

In this review, the authors present a detailed account of the medicinal chemistry campaigns conducted in the recent past for the construction of PARP1/PARP2 inhibitors, PARP1 biased inhibitors, and PARP targeting bifunctional inhibitors as well as PARP targeting degraders (PROTACs). Limitations associated with FDA-approved PARP inhibitors and strategies to outwit the limitations are also discussed.

EXPERT OPINION

The PARP inhibitory field has been rejuvenated with numerous tractable entries in the last decade. With numerous magic bullets in hand coupled with unfolded tactics to outwit the notoriety of cancer cells developing resistance toward PARP inhibitors, the dominance of PARP inhibitors as a sagacious option of targeted therapy is highly likely to be witnessed soon.

Single Inhibitors versus Dual Inhibitors: Role of HDAC in Cancer

Due to the multimodal character of cancer, inhibition of two targets simultaneously by a single molecule is a beneficial and effective approach against cancer. Histone deacetylase (HDAC) was widely investigated as a novel category of anticancer drug targets due to its crucial role in various biological processes like cell-proliferation, metastasis, and apoptosis. Numerous HDAC inhibitors such as vorinostat and panobinostat are clinically approved but have limited usage due to their low efficacy, nonselectivity, drug resistance, and toxicity. Therefore, HDACs with a dual targeting ability have attracted great attention. The strategy of combining a HDAC inhibitor with other antitumor agents has been proved advantageous for combating the nonselectivity and drug resistivity problems associated with single-target drugs. Henceforth, we have highlighted dual-targeting inhibitors to target HDAC along with topoisomerase, receptor tyrosine kinase inhibitors, and the zeste homolog 2 enzyme. Our Review mainly focuses on the impact of the substituent effect along with the linker variation of well-known HDAC-inhibitor-conjugated anticancer drugs.

Dual-target inhibitors of PARP1 in cancer therapy: a drug discovery perspective

Poly (ADP-ribose) polymerase 1 (PARP1), a key enzyme in DNA repair, has emerged as a promising anticancer druggable target. An increasing number of PARP1 inhibitors have been discovered to treat cancer, most notably those characterized by BRCA1/2 mutations. Although PARP1 inhibitors have achieved great clinical success, their cytotoxicity, development of drug resistance, and restriction of indication have weakened their clinical therapeutic effects. To address these issues, dual PARP1 inhibitors have been documented as a promising strategy. Here, we review recent progress in the development of dual PARP1 inhibitors, summarize the different designs of dual-target inhibitors, and introduce their antitumor pharmacology, shedding light on the discovery of dual PARP1 inhibitors for cancer treatment.

Rational Combinations of PARP Inhibitors with HRD-Inducing Molecularly Targeted Agents

Cancers with wild-type BRCA, homologous recombination proficiency, or de novo or acquired resistance to PARP inhibition represent a growing population of patients who may benefit from combinatorial PARP inhibitor strategies. We review targeted inhibitors of angiogenesis, epigenetic regulators, and PI3K, MAPK, and other cellular signaling pathways as inducers of homologous recombination deficiency, providing support for the use of PARP inhibitors in contexts not previously considered susceptible to PARP inhibition.

Multi-therapies Based on PARP Inhibition: Potential Therapeutic Approaches for Cancer Treatment

The nuclear enzymes called poly(ADP-ribose)polymerases (PARPs) are known to catalyze the process of PARylation, which plays a vital role in various cellular functions. They have become important targets for the discovery of novel antitumor drugs since their inhibition can induce significant lethality in tumor cells. Therefore, researchers all over the world have been focusing on developing novel and potent PARP inhibitors for cancer therapy. Studies have shown that PARP inhibitors and other antitumor agents, such as EZH2 and EGFR inhibitors, play a synergistic role in cancer cells. The combined inhibition of PARP and the targets with synergistic effects may provide a rational strategy to improve the effectiveness of current anticancer regimens. In this Perspective, we sum up the recent advance of PARP-targeted agents, including single-target inhibitors/degraders and dual-target inhibitors/degraders, discuss the fundamental theory of developing these dual-target agents, and give insight into the corresponding structure-activity relationships of these agents.

HDAC1 PREDICTOR: a simple and transparent application for virtual screening of histone deacetylase 1 inhibitors

Histone deacetylases play an important role in regulating gene expression by modifying histones and changing chromatin conformation. HDAC dysregulation is involved in many diseases, such as cancer, autoimmune and neurodegenerative diseases. Histone deacetylase 1 (HDAC1) inhibitors represent an important class of drugs. Quantitative Structure-Activity Relationship (QSAR) classification models were developed using 2D RDKit molecular descriptors; ECPF4 (Extended Connectivity Fingerprint) circular fingerprints; and the Random Forest, Gradient Boosting, and Support Vector Machine methods. The developed models were integrated into the HDAC1 PREDICTOR application, which is freely available at the link https://ovttiras-hdac1-inhibitors-hdac1-predictor-app-z3mrbr.streamlitapp.com. The HDAC1 PREDICTOR web application allows one to reveal the compounds for which the predicted activity to inhibit HDAC1 is higher than that of the reference Vorinostat compound (IC₅₀ = 11.08 nM). The algorithm implemented in HDAC1 PREDICTOR for determining the contributions of molecular fragments to the inhibitory activity can be used to find the molecule segments that increase or decrease the activity, enabling the researcher to conduct a rational molecular design of new highly active HDAC1 inhibitors. The developed QSAR models and the code for their construction in the Python programming language are freely available on the GitHub platform at https://github.com/ovttiras/HDAC1-inhibitors.

Olaparib Conjugates with Selenopheno[3,2-c]quinolinone Inhibit PARP1 and Reverse ABCB1-Related Multidrug Resistance

The restoration of the efficacy of antitumor medicines is a cornerstone in the combat with multidrug resistant (MDR) cancers. The overexpression of the ABCB1 transporter is a major obstacle to conventional doxorubicin therapy. The synergy of ABCB1 suppression and PARP1 activity inhibition that hampers malignant cell DNA repair could be a powerful tool in anticancer therapy. Herein, we report the design and synthesis of three novel olaparib conjugates with selenophenoquinolinones, their ability to reverse doxorubicin resistance in uterus sarcoma cells as well as their mechanism of action. It was found that the most potent chemosensitizer among studied compounds preserves PARP1 inhibitory activity and attenuates cells' resistance to doxorubicin by inhibiting ABCB1 transporter activity. These results demonstrate that the conjugation of PARP inhibitors with selenophenoquinolinones is a prospective direction for the development of agents for the treatment of MDR cancers.

PARP Inhibitors: Clinical Limitations and Recent Attempts to Overcome Them

PARP inhibitors are the first clinically approved drugs that were developed based on synthetic lethality. PARP inhibitors have shown promising outcomes since their clinical applications and have recently been approved as maintenance treatment for cancer patients with BRCA mutations. PARP inhibitors also exhibit positive results even in patients without homologous recombination (HR) deficiency. Therapeutic effects were successfully achieved; however, the development of resistance was unavoidable. Approximately 40–70% of patients are likely to develop resistance. Here, we describe the mechanisms of action of PARP inhibitors, the causes of resistance, and the various efforts to overcome resistance. Particularly, we determined the survival probability of cancer patients according to the expression patterns of genes associated with HR restoration, which are critical for the development of PARP inhibitor resistance. Furthermore, we discuss the innovative attempts to degrade PARP proteins by chemically modifying PARP inhibitors. These efforts would enhance the efficacy of PARP inhibitors or expand the scope of their usage.

QSAR analysis and experimental evaluation of new quinazoline-containing hydroxamic acids as histone deacetylase 6 inhibitors

Histone deacetylase inhibitors represent the most important class of drugs for the treatment of human cancer and other diseases due to their influence on cell growth, differentiation, and apoptosis. Among the well-known eighteen histone deacetylases, histone deacetylase 6 (HDAC6), which is involved in oncogenesis, cell survival, and cancer cell metastasis, is of great importance. Using the CDK and alvaDesc molecular descriptors and the Random Forest and EXtreme Gradient Boosting methods, we propose a number of adequate QSAR classification models, which are integrated into a consensus model and are freely available on the OCHEM web platform (https://ochem.eu). The consensus QSAR model is used for virtual screening of a series of seven new compounds, the derivatives of N-((hydroxyamino)-oxoalkyl)-2-(quinazoline-4-ilamino)-benzamides, the synthesis schemes of which are also presented in this work. In vitro evaluation of the inhibitory activity (IC₅₀) of this series of compounds against HDAC6 allowed us to confirm the results of virtual screening and to reveal promising compounds V-2 and V-4, IC₅₀ of which is 3.25 nM and 0.04 nM, respectively. The subsequent in silico evaluation of the main ADMET properties of active compounds V-2 and V-4 allowed us to find that they have acceptable pharmacokinetic parameters and level of acute toxicity.

Dual-target inhibitors based on PARP1: new trend in the development of anticancer research

PARP1 is a hot target, and its inhibitors have been approved for cancer therapy. However, some undesirable properties restrict the application of PARP1 inhibitors, including drug resistance, side effects and low efficiency. For multifactorial diseases, dual-target drugs have exhibited excellent synergistic effects, such as reduced drug resistance, low side effects and high therapeutic efficacy, by simultaneously regulating the main pathogenic and compensatory signal pathways of diseases. In recent years, several dual-target inhibitors based on PARP1 have been reported and have demonstrated unique advantages. In this review we summarize the research progress in dual-target inhibitors based on PARP1 and discuss the related drug design strategies and structure-activity relationships. This work is expected to provide references for the development of PARP1 inhibitors.

In Vitro and Computational Studies of Perezone and Perezone Angelate as Potential Anti-Glioblastoma Multiforme Agents

Glioblastoma multiforme (GBM) represents the most malignant type of astrocytoma, with a life expectancy of two years. It has been shown that Poly (ADP-ribose) polymerase 1 (PARP-1) protein is over-expressed in GBM cells, while its expression in healthy tissue is low. In addition, perezone, a phyto-compound, is a PARP-1 inhibitor with anti-neoplastic activity. As a consequence, in the present study, both in vitro and computational evaluations of perezone and its chemically related compound, perezone angelate, as anti-GBM agents were performed. Hence, the anti-proliferative assay showed that perezone angelate induces higher cytotoxicity in the GBM cell line (U373 IC50 = 6.44 μM) than perezone (U373 IC50 = 51.20 μM) by induction of apoptosis. In addition, perezone angelate showed low cytotoxic activity in rat glial cells (IC50 = 173.66 μM). PARP-1 inhibitory activity (IC50 = 5.25 μM) and oxidative stress induction by perezone angelate were corroborated employing in vitro studies. In the other hand, the performed docking studies allowed explaining the PARP-1 inhibitory activity of perezone angelate, and ADMET studies showed its probability to permeate cell membranes and the blood–brain barrier, which is an essential characteristic of drugs to treat neurological diseases. Finally, it is essential to highlight that the results confirm perezone angelate as a potential anti-GBM agent.

Dual-target inhibitors of poly (ADP-ribose) polymerase-1 for cancer therapy: Advances, challenges, and opportunities

PARP1 plays a crucial role in DNA damage repair, making it an essential target for cancer therapy. PARP1 inhibitors are widely used to treat BRCA-deficient malignancies, and six PARP inhibitors have been approved for clinical use. However, excluding the great clinical success of PARP inhibitors, the concomitant toxicity, drug resistance, and limited scope of application restrict their clinical efficacy. To find solutions to these problems, dual-target inhibitors have shown great potential. In recent years, several studies have linked PAPR1 to other primary cancer targets. Many dual-target inhibitors have been developed using structural fusion, linkage, or library construction methods, overcoming the defects of many single-target inhibitors of PARP1 and achieving great success in clinical cancer therapy. This review summarizes the advance of dual-target PARP1 inhibitors in recent years, focusing on their structural optimization process, structure-activity relationships (SARs), and in vitro or in vivo analysis results.

Dual targeting, a new strategy for novel PARP inhibitor discovery

As a hallmark for cancer treatment, PARP inhibitors can effectively kill tumor cells with a mechanism termed as synthetic lethality, and are used to treat various cancers including ovarian, breast, prostate, pancreatic and others with DNA repair defects. However, along with the clinical trials progressing, the limitations of PARP-1 inhibitors became apparent such as limited activity and indications. Studies have shown that a molecule that is able to simultaneously restrict two or more targets involving in tumors is more effective in preventing and treating cancers due to the enhancing synergies. In order to make up for the shortcomings of PARP inhibitors, reduce the development cost and overcome the pharmacokinetic defects, multiple works were carried out to construct dual targeting PARP inhibitors for cancer therapy. Herein, they were summarized briefly.

Quinazoline-based hydroxamic acid derivatives as dual histone methylation and deacetylation inhibitors for potential anticancer agents

Cancer is a common malignant disease with complex signaling networks, which means it is unmanageable to cancer therapy by using single classical targeted drug. Recently, dual- or multitarget drugs have emerged as a promising option for cancer therapies. Although many multifunctional compounds targeting HDAC have been validated, as far as we know, there is no molecule targeting GLP and HDAC synchronously. In the present work, we designed and synthesized a series of quinazoline-based hydroxamic acid derivatives as dual GLP and HDAC inhibitors. These hybrid compounds showed potent enzymatic inhibitory activities against GLP and HDAC1/6 with IC₅₀ values in the nanomolar range of less than 190 nM. Furthermore, most of our compounds displayed significant broad spectrum cytotoxic activities apart from D3 and D8 against all the tested cancer cells with IC₅₀ values less than 50 μM. D1, D6 and D7 showed more potent cytotoxic activities than D2, D4 and D5 in those cancer cells. Especially, compound D7 showed potent inhibitory potency activity against both GLP and HDAC1/6 with IC₅₀ values of 1.3, 89, 13 nM. Besides, D7 exhibited the most potent antiproliferative activity against all the tested cancer cells. Further evaluations indicated that D7 could inhibit the methylation and deacetylation of H3K9 on protein level. Moreover, D7 could induce cancer cell apoptosis, G0/G1 cell cycle arrest, and partly block migration and invasion. All these thorough evaluations warranted D7 as a promising lead compound worth further optimization and development for cancer therapy.

Dual PARP and RAD51 Inhibitory Drug Conjugates Show Synergistic and Selective Effects on Breast Cancer Cells

The genetic principle of synthetic lethality has most successfully been exploited in therapies engaging Poly-ADP-ribose-polymerase (PARP) inhibitors to treat patients with homologous recombination (HR)-defective tumors. In this work, we went a step further following the idea of a local molecular cooperation and designed hybrid compounds M1–M3. The drug conjugates M1–M3 combine Olaparib, the first PARP inhibitor approved for clinical use, with Cpd 1, an inhibitor of RAD51 that blocks its HR functions and yet permits RAD51 nucleoprotein filament formation on single-stranded DNA. While in M2 and M3, the parental drugs are linked by -CO-(CH₂)_n-CO-spacers (n = 2 and 4, respectively), they are directly merged omitting the piperazine ring of Olaparib in M1. Monitoring anti-survival effects of M1–M3 in six breast cancer cell lines of different molecular subtypes showed that in each cell line, at least one of the drug conjugates decreased viability by one to two orders of magnitude compared with parental drugs. While triple-negative breast cancer (TNBC) cells with frequent BRCA1 pathway dysfunction were sensitive to spacer-linked hybrid compounds M1 and M2 regardless of their HR capacities, non-TNBC cells were responsive to the merged drug conjugate M1 only, suggesting different spatial requirements for dual inhibition in these two groups of cell lines. These results demonstrate that, depending on chemical linkage, dual PARP1-RAD51 inhibitory drugs can either sensitize non-TNBC and re-sensitize TNBC cells, or discriminate between these groups of cells.

Dexamethasone and Fumaric Acid Ester Conjugate Synergistically Inhibits Inflammation and NF-κB in Macrophages

Macrophage-mediated inflammation drives autoimmune and chronic inflammatory diseases. Treatment with anti-inflammatory agents can be an effective strategy to reduce this inflammation; however, high concentrations of these agents can have immune-dampening and other serious side effects. Synergistic combination of anti-inflammatory agents can mitigate dosing by requiring less drug. Multiple anti-inflammatory agents were evaluated in combination for synergistic inhibition of macrophage inflammation. The most potent synergy was observed between dexamethasone (DXM) and fumaric acid esters (e.g., monomethyl fumarate (MMF)). Furthermore, this combination was found to synergistically inhibit inflammatory nuclear factor κB (NF-κB) transcription factor activity. The optimal ratio for synergy was determined to be 1:1, and DXM and MMF were conjugated by esterification at this molar ratio. The DXM-MMF conjugate displayed improved inhibition of inflammation over the unconjugated combination in both murine and human macrophages. In the treatment of human donor monocyte-derived macrophages, the combination of DXM and MMF significantly inhibited inflammatory gene expression downstream of NF-κB and overall performed better than either agent alone. Further, the DXM-MMF conjugate significantly inhibited expression of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome-associated genes. The potent anti-inflammatory activity of the DXM-MMF conjugate in human macrophages indicates that it may have benefits in the treatment of autoimmune and inflammatory diseases.

Dissecting Histone Deacetylase 3 in Multiple Disease Conditions: Selective Inhibition as a Promising Therapeutic Strategy

The acetylation of histone and non-histone proteins has been implicated in several disease states. Modulation of such epigenetic modifications has therefore made histone deacetylases (HDACs) important drug targets. HDAC3, among various class I HDACs, has been signified as a potentially validated target in multiple diseases, namely, cancer, neurodegenerative diseases, diabetes, obesity, cardiovascular disorders, autoimmune diseases, inflammatory diseases, parasitic infections, and HIV. However, only a handful of HDAC3-selective inhibitors have been reported in spite of continuous efforts in design and development of HDAC3-selective inhibitors. In this Perspective, the roles of HDAC3 in various diseases as well as numerous potent and HDAC3-selective inhibitors have been discussed in detail. It will surely open up a new vista in the discovery of newer, more effective, and more selective HDAC3 inhibitors.

Recent development in the discovery of PARP inhibitors as anticancer agents: a patent update (2016-2020)

INTRODUCTION

Discovery of small molecules that impede the activity of single-strand DNA repair enzyme, PARP1, has led to four marketed drugs for the treatment of advanced-stage cancers. Hence, there is a renewed enthusiasm in the PARP inhibitor discovery arena. To reduce nonspecific interactions or potential toxicities, and to understand the role of other minimally explored PARP enzymes, exciting new findings have emerged toward the development of selective inhibitors and targeted chemical biology probes. Importantly, the conventional PARP inhibitor design has evolved in a way that could potentially lead to multienzyme-targeting - a polypharmacological approach against aggressive cancers.

AREAS COVERED

This review comprises recent progress made in the development of PARP inhibitors, primarily focused on human cancers. Discovery of novel PARP inhibitors with pan, selective, and multi-target inhibition using in vitro and in vivo cancer models is summarized and critically evaluated. Emphasis is given to patents published during 2016-2020, excluding TNKS 1/2 inhibitors.

EXPERT OPINION

The outstanding success demonstrated by the FDA approved PARP inhibitors has fueled further clinical evaluations for expansion of their clinical utilities. The current clinical investigations include new candidates as well as marketed PARP-targeted drugs, both as single agents and in combination with other chemotherapeutics. Recent advances have also unveiled critical roles of other PARPs in oncogenic signal transduction, in addition to those of the well-documented PARP1/2 and TNKS1/2 enzymes. Further studies on lesser-known PARP members are urgently needed for functional annotations and for understanding their roles in cancer progression and other human diseases.

Shifting the paradigm in treating multi-factorial diseases: polypharmacological co-inhibitors of HDAC6

Multi-factorial diseases are illnesses that exploit multiple cellular processes, or stages within one process, and thus highly targeted therapies often succumb to the disease, losing efficacy as resistance sets in. Combination therapies have become a mainstay to battle these diseases, however these regimens are plagued with caveats. An emerging avenue to treat multi-factorial diseases is polypharmacology, wherein a single drug is rationally designed to bind multiple targets, and is widely touted to be superior to combination therapy by inherently addressing the latter's shortcomings, which include poor patient compliance, narrow therapeutic windows and spiraling healthcare costs. Through its roles in intracellular trafficking, cell motility, mitosis, protein folding and as a back-up to the proteasome pathway, HDAC6 has rapidly become an exciting new target for therapeutics, particularly in the discovery of new drugs to treat Alzheimer's disease and cancer. Herein, we describe recent efforts to marry together HDAC pharmacophores, with a particular emphasis on HDAC6 selectivity, with those of other targets towards the discovery of potent therapeutics to treat these evasive diseases. Such polypharmacological agents may supercede combination therapies through inherent synergism, permitting reduced dosing, wider therapeutic windows and improved compliance.

Fluorescent detection of PARP activity in unfixed tissue

Poly-ADP-ribose-polymerase (PARP) relates to a family of enzymes that can detect DNA breaks and initiate DNA repair. While this activity is generally seen as promoting cell survival, PARP enzymes are also known to be involved in cell death in numerous pathologies, including in inherited retinal degeneration. This ambiguous role of PARP makes it attractive to have a simple and fast enzyme activity assay, that allows resolving its enzymatic activity in situ, in individual cells, within complex tissues. A previously published two-step PARP activity assay uses biotinylated NAD+ and streptavidin labelling for this purpose. Here, we used the fluorescent NAD+ analogues ε-NAD+ and 6-Fluo-10-NAD+ to assess PARP activity directly on unfixed tissue sections obtained from wild-type and retinal degeneration-1 (rd1) mutant retina. In standard UV microscopy ε-NAD+ incubation did not reveal PARP specific signal. In contrast, 6-Fluo-10-NAD+ resulted in reliable detection of in situ PARP activity in rd1 retina, especially in the degenerating photoreceptor cells. When the 6-Fluo-10-NAD+ based PARP activity assay was performed in the presence of the PARP specific inhibitor olaparib, the activity signal was completely abolished, attesting to the specificity of the assay. The incubation of live organotypic retinal explant cultures with 6-Fluo-10-NAD+, did not produce PARP specific signal, indicating that the fluorescent marker may not be sufficiently membrane-permeable to label living cells. In summary, we present a new, rapid, and simple to use fluorescence assay for the cellular resolution of PARP activity on unfixed tissue, for instance in complex neuronal tissues such as the retina.

Comprehensive review for anticancer hybridized multitargeting HDAC inhibitors

Despite the encouraging clinical progress of chemotherapeutic agents in cancer treatment, innovation and development of new effective anticancer candidates still represents a challenging endeavor. With 15 million death every year in 2030 according to the estimates, cancer has increased rising of an alarm as a real crisis for public health and health systems worldwide. Therefore, scientist began to introduce innovative solutions to control the cancer global health problem. One of the promising strategies in this issue is the multitarget or smart hybrids having two or more pharmacophores targeting cancer. These rationalized hybrid molecules have gained great interests in cancer treatment as they are capable to simultaneously inhibit more than cancer pathway or target without drug-drug interactions and with less side effects. A prime important example of these hybrids, the HDAC hybrid inhibitors or referred as multitargeting HDAC inhibitors. The ability of HDAC inhibitors to synergistically improve the efficacy of other anti-cancer drugs and moreover, the ease of HDAC inhibitors cap group modification prompt many medicinal chemists to innovate and develop new generation of HDAC hybrid inhibitors. Notably, and during this short period, there are four HDAC inhibitor hybrids have entered different phases of clinical trials for treatment of different types of blood and solid tumors, namely; CUDC-101, CUDC-907, Tinostamustine, and Domatinostat. This review shed light on the most recent hybrids of HDACIs with one or more other cancer target pharmacophore. The designed multitarget hybrids include topoisomerase inhibitors, kinase inhibitors, nitric oxide releasers, antiandrogens, FLT3 and JAC-2 inhibitors, PDE5-inhibitors, NAMPT-inhibitors, Protease inhibitors, BRD4-inhibitors and other targets. This review may help researchers in development and discovery of new horizons in cancer treatment.

Dual inhibitors of histone deacetylases and other cancer-related targets: A pharmacological perspective

Epigenetic enzymes histone deacetylases (HDACs) are clinically validated anticancer drug targets which have been studied intensively in the past few decades. Although several drugs have been approved in this field, they are still limited to a subset of hematological malignancies (in particular T-cell lymphomas), with therapeutic potential not fully realized and the drug-resistance occurred after a certain period of use. To maximize the therapeutic potential of these classes of anticancer drugs, and to extend their application to solid tumors, numerous combination therapies containing an HDACi and an anticancer agent from other mechanisms are currently ongoing in clinical trials. Recently, dual targeting strategy comprising the HDACs component has emerged as an alternative approach for combination therapies. In this perspective, we intend to gather all HDACs-containing dual inhibitors related to cancer therapy published in literature since 2015, classify them into five categories based on targets' biological functions, and discuss the rationale why dual acting agents should work better than combinatorial therapies using two separate drugs. The article discusses the pharmacological aspects of these dual inhibitors, including in vitro biological activities, pharmacokinetic studies, in vivo efficacy studies, as well as available clinical trials. The review of the current status and advances should provide better analysis for future opportunities and challenges of this field.

Paradigm shift of "classical" HDAC inhibitors to "hybrid" HDAC inhibitors in therapeutic interventions

'Epigenetic' regulation of genes via post-translational modulation of proteins is the current mainstay approach for the disease therapies, particularly explored in the Histone Deacetylase (HDAC) class of enzymes. Mainly sight saw in cancer chemotherapeutics, HDAC inhibitors have also found a promising role in other diseases (neurodegenerative disorders, cardiovascular diseases, and viral infections) and successfully entered in various combination therapies (pre-clinical/clinical stages). The prevalent flexibility in the structural design of HDAC inhibitors makes them easily tuneable to merge with other pharmacophore modules for generating multi-targeted single hybrids as a novel tactic to overcome drawbacks of polypharmacy. Herein, we reviewed the putative role of prevalent HDAC hybrids inhibitors in the current and prospective stage as a translational approach to overcome the limitations of the existing conventional drug candidates (parent molecule) when used either alone (drug resistance, solubility issues, adverse side effects, selectivity profile) or in combination (pharmacokinetic interactions, patient compliance) for treating various diseases.

Synthesis, chemical characterization, PARP inhibition, DNA binding and cellular uptake of novel ruthenium(II)-arene complexes bearing benzamide derivatives in human breast cancer cells

Inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) showed remarkable clinical efficacy in BRCA-mutated tumors. Based on the rational drug design, derivatives of PARP inhibitor 3-aminobenzamide (3-AB), 2-amino-4-methylbenzamide (L1) and 3-amino-N-methylbenzamide (L2), were coordinated to the ruthenium(II) ion, to form potential drugs affecting DNA and inhibiting PARP enzyme. The four conjugated complexes of formula: C1 [(ƞ⁶-toluene)Ru(L1)Cl]PF₆, C2 [(ƞ⁶-p-cymene)Ru(L1)Cl]PF₆, C3 [(ƞ⁶-toluene)Ru(L2)Cl₂] and C4 [(ƞ⁶-p-cymene)Ru(L2)Cl₂], have been synthesized and characterized. Colorimetric 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide (MTT) assay showed the highest antiproliferative activity of C1 in HCC1937, MDA-MB-231, and MCF-7 breast cancer cells. Efficiency of inhibition of PARP-1 enzymatic activity in vitro decreased in order: C2 > C4 > 3-AB>C1 > C3. ICP-MS study of intracellular accumulation and distribution in BRCA1-mutated HCC1937 revealed that C1-C4 entered cells within 24 h. The complex C1 showed the highest intracellular accumulation, nuclear-targeting properties, and exhibited the highest DNA binding (39.2 ± 0.6 pg of Ru per μg of DNA) that resulted in the cell cycle arrest in the S phase.

Dual-Target Inhibitors Based on HDACs: Novel Antitumor Agents for Cancer Therapy

Histone deacetylases (HDACs) play an important role in regulating target gene expression. They have been highlighted as a novel category of anticancer targets, and their inhibition can induce apoptosis, differentiation, and growth arrest in cancer cells. In view of the fact that HDAC inhibitors and other antitumor agents, such as BET inhibitors, topoisomerase inhibitors, and RTK pathway inhibitors, exert a synergistic effect on cellular processes in cancer cells, the combined inhibition of two targets is regarded as a rational strategy to improve the effectiveness of these single-target drugs for cancer treatment. In this review, we discuss the theoretical basis for designing HDAC-involved dual-target drugs and provide insight into the structure-activity relationships of these dual-target agents.

Orthogonal Proteomic Platforms and Their Implications for the Stable Classification of High-Grade Serous Ovarian Cancer Subtypes

The National Cancer Institute (NCI) Clinical Proteomic Tumor Analysis Consortium (CPTAC) established a harmonized method for large-scale clinical proteomic studies. SWATH-MS, an instance of data-independent acquisition (DIA) proteomic methods, is an alternate proteomic approach. In this study, we used SWATH-MS to analyze remnant peptides from the original retrospective TCGA samples generated for the CPTAC ovarian cancer proteogenomic study. The SWATH-MS results recapitulated the confident identification of differentially expressed proteins in enriched pathways associated with the robust Mesenchymal high-grade serous ovarian cancer subtype and the homologous recombination deficient tumors. Hence, SWATH/DIA-MS presents a promising complementary or orthogonal alternative to the CPTAC proteomic workflow, with the advantages of simpler and faster workflows and lower sample consumption, albeit with shallower proteome coverage. In summary, both analytical methods are suitable to characterize clinical samples, providing proteomic workflow alternatives for cancer researchers depending on the context-specific goals of the studies.

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SWATH-MS and iTRAQ-DDA are used to classify 103 high-grade serous ovarian cancer

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SWATH-MS re-capitulates differentially expressed proteins in ovarian cancer subtypes

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SWATH-MS is a robust proteomic approach for large-scale clinical proteomic studies

Zinc Dependent Histone Deacetylase Inhibitors in Cancer Therapeutics: Recent Update

BACKGROUND

Histone deacetylases (HDAC) are an important class of enzymes that play a pivotal role in epigenetic regulation of gene expression that modifies the terminal of core histones leading to remodelling of chromatin topology and thereby controlling gene expression. HDAC inhibitors (HDACi) counter this action and can result in hyperacetylation of histones, thereby inducing an array of cellular consequences such as activation of apoptotic pathways, generation of reactive oxygen species (ROS), cell cycle arrest and autophagy. Hence, there is a growing interest in the potential clinical use of HDAC inhibitors as a new class of targeted cancer therapeutics. Methodology and Result: Several research articles spanning between 2016 and 2017 were reviewed in this article and presently offer critical insights into the important strategies such as structure-based rational drug design, multi-parameter lead optimization methodologies, relevant SAR studies and biology of various class of HDAC inhibitors, such as hydroxamic acids, benzamides, cyclic peptides, aliphatic acids, summarising the clinical trials and results of various combination drug therapy till date.

CONCLUSION

This review will provide a platform to the synthetic chemists and biologists to cater the needs of both molecular targeted therapy and combination drug therapy to design and synthesize safe and selective HDAC inhibitors in cancer therapeutics.