The combination of histone deacetylase inhibitors and radiotherapy: a promising novel approach for cancer treatment.

HDAC inhibitors (HDACi) play an essential role in various cellular processes, such as differentiation and transcriptional regulation of key genes and cytostatic factors, cell cycle arrest and apoptosis that facilitates the targeting of epigenome of eukaryotic cells. In the majority of cancers, only a handful of patients receive optimal benefit from chemotherapeutics. Additionally, there is emerging interest in the use of HDACi to modulate the effects of ionizing radiations. The use of HDACi with radiotherapy, with the goal of reaching dissimilar, often distinct pathways or multiple biological targets, with the expectation of synergistic effects, reduced toxicity and diminished intrinsic and acquired resistance, conveys an approach of increasing interest. In this review, the clinical potential of HDACi in combination with radiotherapy is described as an efficient synergy for cancer treatment will be overviewed.

Synthesis, biological evaluation and molecular docking studies of 2-amino-3,4,5-trimethoxyaroylindole derivatives as novel anticancer agents.

A series of novel 2-amino-3,4,5 trimethoxyaroylindole derivatives was synthesized and evaluated against selected human cancer cell lines of breast (MCF-7) and colon (HT-29). Introduction of an amino group at the C-2 position on ring A of 3,4,5-trimethoxyaroylindole derivatives resulted in novel compounds, i.e., 2-amino-3,4,5-trimethoxyaroylindole derivatives exhibiting excellent cytotoxic activity against human cancer cell lines. Substitution with methoxy group at R(6) in 2-amino-3,4,5-trimethoxyaroylindole 5d exhibited excellent cytotoxic activity against MCF-7 (0.013 µM) and colon HT-29 (0.143 µM) indicating slightly higher potency than Combretastatin A-4. Molecular modeling studies of 2-amino-3,4,5-trimethoxyaroylindole derivatives have similar structural alignment as colchicine in protein (PDB code: 1SA0) and exhibited hydrogen bond interaction between para position of 3,4,5-trimethoxyphenyl ring with CYS 241 and N-H molecule of indole ring with Val 315 of receptor molecule.

Multi-targeted HDAC Inhibitors as Anticancer Agents: Current Status and Future Prospective.

Multi-targeted agents can interact with multiple targets sequentially, resulting in synergistic and more effective therapies for several complicated disorders, including cancer, even with relatively modest activity. Histone deacetylase (HDAC) inhibitors are low molecular weight small compounds that increase the acetylation of histone and nonhistone proteins, altering gene expression and thereby impacting angiogenesis, metastasis, and apoptosis, among other processes. The HDAC inhibitors affect multiple cellular pathways thus producing adverse issues, causing therapeutic resistance, and they have poor pharmacokinetic properties. The designing of HDAC-based dual/multi-target inhibitor is an important strategy to overcome adverse effects, drug resistance and increase the effectiveness in controlling cancer. The selection of target combinations to design multitarget HDAC inhibitor is generally accomplished on the basis of systematic highthroughput screening (HTS), network pharmacology analysis methods. The identification of the pharmacophore against individual targets is performed using rational or computation methods. The identified pharmacophore can combine with merged, fused, or linked with the cleavable or non-cleavable linker to retain the interaction with the original target while being compatible with the other target. The objective of this review is to elucidate the potential targets' design strategies, biological activity, and the recent development of dual/multi-targeting HDAC inhibitors as potential anticancer agents. This review elucidates the designing strategies of the potential target along with biological activity and the recent development of dual/multi-targeting HDAC inhibitors as potential anticancer agents. The development of HDAC-based dual/multi-target inhibitors is important for overcoming side effects, drug resistance, and effective cancer control.

Combination Therapy for the Treatment of Alzheimer's Disease: Recent Progress and Future Prospects.

BACKGROUND: The management of Alzheimer's disease is challenging due to its complexity. However, the currently approved and marketed treatments for this neurodegenerative disorder revolves around cholinesterase inhibitors, glutamate regulators, or the combination of these agents. Despite the prompt assurance of many new drugs, several agents were unsuccessful, especially in phase II or III trials, not meeting efficacy endpoints. OBJECTIVE: The execution of effective treatment approaches through further trials investigating a rational combination of agents is necessitude for Alzheimer's disease. METHODS: For this review, more than 248 relevant scientific papers were considered from a variety of databases (Scopus, Web of Science, Google Scholar, ScienceDirect, and PubMed) using the keywords Alzheimer's disease, amyloid-ß, combination therapies, cholinesterase inhibitors, dementia, glutamate regulators, AD hypothesis. RESULT AND DISCUSSION: The researcher's intent is to either develop a disease-modifying therapeutic means for aiming in the early phases of dementia and/or optimize the available symptomatic treatments principally committed to the more advanced stages of Alzheimer's. Since Alzheimer's possesses multifactorial pathogenesis, designing a multimodal therapeutic intervention for targeting different pathological processes of dementia may appear to be the most practical method to alter the course of disease progression. CONCLUSION: The combination approach may even allow for providing individual agents in lower doses, with reducible costs and side effects. Numerous studies on combination therapy predicted better clinical efficacy than monotherapy. The literature review highlights the major clinical studies (both symptomatic and disease-modifying) conducted in the past decade on combination therapy to combat cognitive disorder.

Corticosteroids for treatment of COVID-19: effect, evidence, expectation and extent.

BACKGROUND: The World Health Organization (WHO) announced the COVID-19 occurrence as a global pandemic in March 2020. The treatment of SARS-CoV-2 patients is based on the experience gained from SARS-CoV and MERS-CoV infection during 2003. There is no clinically accepted therapeutic drug(s) accessible yet for the treatment of COVID-19. MAIN BODY: Corticosteroids, i.e., dexamethasone, methylprednisolone, hydrocortisone and prednisone are used alone or in combination for the treatment of moderate, severe and critically infected COVID-19 patients who are hospitalized and require supplemental oxygen as per current management strategies and guidelines for COVID-19 published by the National Institutes of Health. Corticosteroids are recorded in the WHO model list of essential medicines and are easily accessible worldwide at a cheaper cost in multiple formulations and various dosage forms. Corticosteroid can be used in all age group of patients, i.e., children, adult, elderly and during pregnancy or breastfeeding women. Corticosteroids have potent anti-inflammatory and immunosuppressive effects in both primary and secondary immune cells, thereby reducing the generation of proinflammatory cytokines and chemokines and lowering the activation of T cells, monocytes and macrophages. The corticosteroids should not be used in the treatment of non-severe COVID-19 patients because corticosteroids suppress the immune response and reduce the symptoms and associated side effects such as slow recovery, bacterial infections, hypokalemia, mucormycosis and finally increase the chances of death. CONCLUSION: Intensive research on corticosteroid therapy in COVID-19 treatment is urgently needed to elucidate their mechanisms and importance in contributing toward successful prevention and treatment approaches. Hence, this review emphasizes on recent advancement on corticosteroid therapy for defining their importance in overcoming SARS-CoV-2 pandemic, their mechanism, efficacy and extent of corticosteroids in the treatment of COVID-19 patients.

Understanding the role of ACE-2 receptor in pathogenesis of COVID-19 disease: a potential approach for therapeutic intervention.

Angiotensin-converting enzyme (ACE) and its homologue, ACE2, are commonly allied with hypertension, renin-angiotensin-aldosterone system pathway, and other cardiovascular system disorders. The recent pandemic of COVID-19 has attracted the attention of numerous researchers on ACE2 receptors, where the causative viral particle, SARS-CoV-2, is established to exploit these receptors for permitting their entry into the human cells. Therefore, studies on the molecular origin and pathophysiology of the cell response in correlation to the role of ACE2 receptors to these viruses are bringing novel theories. The varying level of manifestation and importance of ACE proteins, underlying irregularities and disorders, intake of specific medications, and persistence of assured genomic variants at the ACE genes are potential questions raising nowadays while observing the marked alteration in response to the SARS-CoV-2-infected patients. Therefore, the present review has focused on several raised opinions associated with the role of the ACE2 receptor and its impact on COVID-19 pathogenesis.

Synthetic and Semi-synthetic Drugs as a Promising Therapeutic Option for the Treatment of COVID-19.

The novel coronavirus disease-19 (COVID-19) is a global pandemic that emerged from Wuhan, China, and has spread all around the world, affecting 216 countries or territories with 21,732,472 people infected and 770,866 deaths globally (as per WHO COVID-19 updates of August 18, 2020). Continuous efforts are being made to repurpose the existing drugs and develop vaccines for combating this infection. Despite, to date, no certified antiviral treatment or vaccine exists. Although, few candidates have displayed their efficacy in in vitro studies and are being repurposed for COVID- 19 treatment. This article summarizes synthetic and semi-synthetic compounds displaying potent activity in clinical uses or studies on COVID-19 and also focuses on the mode of action of drugs being repositioned against COVID-19.

Identification of Hydroxamic Acid Based Selective HDAC1 Inhibitors: Computer Aided Drug Design Studies.

BACKGROUND: Overexpression of Histone deacetylase 1 (HDAC1) is responsible for carcinogenesis by promoting epigenetic silence of tumour suppressor genes. Thus, HDAC1 inhibitors have emerged as the potential therapeutic leads against multiple human cancers, as they can block the activity of particular HDACs, renovate the expression of several tumour suppressor genes and bring about cell differentiation, cell cycle arrest and apoptosis. METHODS: The present research work comprises atom-based 3D-QSAR, docking, molecular dynamic simulations and DFT (density functional theory) studies on a diverse series of hydroxamic acid derivatives as selective HDAC1 inhibitors. Two pharmacophoric models were generated and validated by calculating the enrichment factors with the help of the decoy set. The Four different 3D-QSAR models i.e., PLS (partial least square) model, MLR (multiple linear regression) model, Field-based model and GFA (Genetic function approximation) model were developed using 'PHASE' v3.4 (Schrödinger) and Discovery Studio (DS) 4.1 software and validated using different statistical parameters like internal and external validation. RESULTS AND DISCUSSION: The results showed that the best PLS model has R2=0.991 and Q2=0.787, the best MLR model has R2= 0.993 and Q2= 0.893, the best Field-based model has R2= 0.974 and Q2= 0.782 and the best GFA model has R2= 0.868 and Q2= 0.782. Cross-validated coefficients, (rcv 2) of 0.967, 0.926, 0.966 and 0.829 was found for PLS model, MLR, Field based and GFA model, respectively, indicated the satisfactory correlativity and prediction. The docking studies were accomplished to find out the conformations of the molecules and their essential binding interactions with the target protein. The trustworthiness of the docking results was further confirmed by molecular dynamics (MD) simulations studies. Density Functional Theory (DFT) study was performed which promptly optimizes the geometry, stability and reactivity of the molecule during receptor-ligand interaction. CONCLUSION: Thus, the present research work provides spatial fingerprints which would be beneficial for the development of potent HDAC1 inhibitors.

Histone Deacetylase Inhibitors for the Treatment of Colorectal Cancer: Recent Progress and Future Prospects.

BACKGROUND: Colorectal cancer is a devastating disease with a dismal prognosis which is heavily hampered by delayed diagnosis. Surgical resection, radiation therapy and chemotherapy are the curative options. Due to few therapeutic treatments available i.e., mono and combination therapy and development of resistance towards drug response, novel and efficacious therapy are urgently needed. OBJECTIVE: In this study, we have studied the potential of histone deacetylase inhibitors in colorectal cancer. RESULTS: Histone deacetylase inhibitors (HDACIs) are an emerging class of therapeutic agents having potential anticancer activity with minimal toxicity for different types of malignancies in preclinical studies. HDACIs have proven less effective in monotherapy thus the combination of HDACIs with other anticancer agents are being assessed for the treatment of colorectal cancer. CONCLUSION: The molecular mechanism emphasizing the anticancer effect of HDACIs in colorectal cancer was illustrated and a recapitulation was carried out on the recent advances in the rationale behind combination therapies currently underway in clinical evaluations.

Panobinostat as Pan-deacetylase Inhibitor for the Treatment of Pancreatic Cancer: Recent Progress and Future Prospects.

The histone deacetylase (HDAC) inhibitors have been demonstrated as an emerging class of anticancer drugs. HDACs are involved in regulation of gene expression and in chromatin remodeling, thus indicating valid targets for different types of cancer therapeutics. The pan-deacetylase inhibitor panobinostat (Farydac®, LBH589) was developed by Novartis Pharmaceuticals and has been recently approved by the US Food and Drug Administraion (FDA) as a drug to treat multiple myeloma. It is under clinical investigation for a range of haematological and solid tumors worldwide in both oral and intravenous formulations. Panobinostat inhibits tumor cell growth by interacting with acetylation of histones and non-histone proteins as well as various apoptotic, autophagy-mediated targets and various tumorogenesis pathways involved in development of tumors. The optimal combination regimen for pancreatic cancer remains to be fully elucidated with various combination regimens, and should be investigated in clinical trials. This article summarizes the current preclinical and clinical status of panobinostat in pancreatic cancer. Preclinical data suggests that panobinostat has potential inhibitory activity in pancreatic cancer cells by targeting various pathways and factors involved in the development of cancer. Herein, we reviewed the status of mono and combination therapy and the rationale behind the combination therapy undergoing trials, as well as possible future prospective use in the treatment of pancreatic cancer.

Novel pyrimidine based semicarbazones: Confirmation of four binding site pharmacophoric model hypothesis for antiepileptic activity.

BACKGROUND: Epilepsy is a neurological disorder, characterized by seizures accompanied by loss or disturbance of consciousness affecting various physical and mental functions. Current anticonvulsant drugs are effective in controlling seizures in about 70% of cases, but their use is often limited by side effects like ataxia, megaloblastic anemia, hepatic failure. In search for a novel anticovulsant drug with better efficacy and lower toxicity, a series of novel pyrimidine based semicarbazone were designed and evaluated for antiepileptic activity. METHODS: The test compounds were designed on the basis of four site binding hypothesis proposed for anticonvulsant activity. The chemical structures of the test compounds were elucidated using spectral (IR, 1H NMR, 13C NMR and MS) and elemental analysis. The minimal motor impairment activity was determined in mice using rotorod test. The maximal electroshock seizure (MES) and subcutaneous pentylenetrtrazole (scPTZ) models were employed for anticonvulsant evaluation. RESULTS: The results reveal that 76% of the compounds were active in the MES screening as compared to 53% of the compounds in the scPTZ test. Test compounds showed some MES selectivity displaying their effectiveness in generalized seizures of the tonic-clonic type. The molecular docking analysis of semicarbazone derivatives showed good ligand-receptor interactions with specially hydrogen bond interactions with ARG192, GLU270 and THR353 amino acid of receptor. CONCLUSION: The present report confirms that pharmacophore model with four binding sites is crucial for anticonvulsant activity in the semicarbazones.

Drug Design Strategies for the Discovery of Novel Anticonvulsants Concerned with Four Site Binding Pharmacophoric Model Studies.

Anticonvulsant refers to a group of pharmaceuticals used in the treatment of epileptic seizures. The use of current antiepileptic drugs has been questioned due to the non-selectivity of the drugs and the undesirable side effects produced by them. This led to the search for antiepileptic compounds with more selectivity and lower toxicity. Semicarbazones have been developed as versatile anticonvulsant pharmacophore. It has displayed potent anticonvulsant effect in a wide variety of preclinical anticonvulsant models. Till date various semicarbazone derivatives containing 1,3,4-oxadiazole, 1,3,4-thiadiazole, pyrimidine, benzothiazole and substituted phenyl/aryl ring have been synthesized and evaluated for anticonvulsant activity. The semicarbazone based pharmacophore model with four binding sites is essential for anticonvulsant activity. This model comprises of an aryl hydrophobic binding site, hydrogen bonding domain, an electron donor group and another hydrophobic-hydrophilic site regulating the pharmacokinetic properties of the anticonvulsant. Extensive structure-activity relationship has demonstrated that compound with OH, CH3O, NO2, Cl, F, Br substituents in the arylhydrophobic pocket, nitro, hydroxy group on distant phenyl ring and a hydrogen bonding domain possess anticonvulsant activity. In this review, advances made in the application of semicarbazones as a versatile pharmacophore model for the design of new anticonvulsant drugs are being updated and suggested for future drug design and development of novel anticonvulsants.

Pharmacophore Based 3D-QSAR, Virtual Screening and Docking Studies on Novel Series of HDAC Inhibitors with Thiophen Linker as Anticancer Agents.

BACKGROUND: Histone deacetylase (HDAC) inhibitors can reactivate gene expression and inhibit the growth and survival of cancer cells. OBJECTIVE: To identify the important pharmacophoric features and correlate 3Dchemical structure with biological activity using 3D-QSAR and Pharmacophore modeling studies. METHOD: The pharmacophore hypotheses were developed using e-pharmacophore script and phase module. Pharmacophore hypothesis represents the 3D arrangement of molecular features necessary for activity. A series of 55 compounds with wellassigned HDAC inhibitory activity were used for 3D-QSAR model development. RESULTS: Best 3D-QSAR model, which is a five partial least square (PLS) factor model with good statistics and predictive ability, acquired Q2 (0.7293), R2 (0.9811), cross-validated coefficient rcv 2=0.9807 and R2 pred=0.7147 with low standard deviation (0.0952). Additionally, the selected pharmacophore model DDRRR.419 was used as a 3D query for virtual screening against the ZINC database. In the virtual screening workflow, docking studies (HTVS, SP and XP) were carried out by selecting multiple receptors (PDB ID: 1T69, 1T64, 4LXZ, 4LY1, 3MAX, 2VQQ, 3C10, 1W22). Finally, six compounds were obtained based on high scoring function (dock score -11.2278-10.2222 kcal/mol) and diverse structures. CONCLUSION: The structure activity correlation was established using virtual screening, docking, energetic based pharmacophore modelling, pharmacophore, atom based 3D QSAR models and their validation. The outcomes of these studies could be further employed for the design of novel HDAC inhibitors for anticancer activity.

Tracheal Agenesis with Tracheo-oesophageal Fistula.

Tracheal Agenesis (TA) presents with respiratory distress at birth. Diagnosis requires recognition of clinical signs in newborns like failure of endotracheal intubation, respiratory distress with absent air entry over both side of chest and inaudible cry. We describe a TA Floyd Type I with a Tracheo-Oesophageal Fistula (TOF) without other congenital malformations.