Synthesis of Altissimacoumarin D and Other Prenylated Coumarins and Their Ability to Reverse the Multidrug Resistance Phenotype in Candida albicans

Azoles are the main antifungal agents employed in clinical practice to treat invasive candidiasis. Nonetheless, their efficacy is limited by fungal resistance mechanisms, mainly the overexpression of efflux pumps. Consequently, candidiasis has a worrisome death rate of 75%. One potential strategy to overcome efflux-mediated resistance is to inhibit this process. Ailanthus altissima is a Chinese tree that produces several active substances, including altissimacoumarin D. Due to the low yield of its extraction and the need to search for new drugs to treat candidiasis, this study aimed to synthesize altissimacoumarin D and its analogues, as well as evaluating their ability to reverse the resistance phenotype of Candida albicans. Coumarin isofraxidin was prepared via total synthesis through a solvent-free Knoevenagel condensation as the key step. Isofraxidin and other commercially available coumarins were alkylated with prenyl or geranyl groups to yield the natural product altissimacoumarin D and seven analogues. The antifungal activity of the coumarins and their ability to reverse the fungal resistance phenotype were assessed using microbroth methodologies. Toxicity was evaluated using erythrocytes and an in silico prediction. All compounds improved the antifungal activity of fluconazole by inhibiting efflux pumps, and ACS47 and ACS50 were the most active. None of the coumarins were toxic to erythrocytes. In silico predictions indicate that ACS47 and ACS50 may be safe for human use. ACS47 and ACS50 are promising candidates when used as adjuvants in the antifungal therapy against C. albicans-resistant strains.

Acute Respiratory Infection Incidence and Outpatient Antibiotic Prescription Patterns in People With or Without Human Immunodeficiency Virus Infection: A Virtual Cohort Study

Background

Inappropriate antibiotic use in acute respiratory infections (ARIs) is a major public health concern; however, data for people with human immunodeficiency virus (PWH) are limited.

Methods

The HIV Virtual Cohort Study is a retrospective cohort of adult Department of Defense beneficiaries. Male PWH cases (n = 2413) were matched 1:2 to controls without HIV (n = 4826) by age, gender, race/ethnicity, and beneficiary status. Acute respiratory infection encounters between 2016 and 2020 and corresponding antibiotic prescriptions were characterized as always, sometimes, or never appropriate based on International Classification of Diseases, Tenth Revision coding. Incidence of ARI encounters and antibiotic appropriateness were compared between PWH and controls. Subgroup analyses were assessed by CD4 count and viral load suppression on antiretroviral therapy.

Results

Mean rates of ARI encounters were similar for PWH (1066 per 1000 person-years) and controls (1010 per 1000 person-years); however, the rate was double among PWH without viral load (VL) suppression (2018 per 1000 person-years). Antibiotics were prescribed in 26% of encounters among PWH compared to 34% for controls (P ≤ .01); antibiotic use was "never" appropriate in 38% of encounters with PWH and 36% in controls. Compared to controls, PWH received more sulfonamides (5.5% vs 2.7%; P = .001), and variation existed among HIV subgroups in the prescription of sulfonamides, fluoroquinolones, and β-lactams.

Discussion

Acute respiratory infection encounters were similar for PWH and those without HIV; however, PWH with lower CD4 counts and/or nonsuppressed VL had more frequent ARI visits. Inappropriate antibiotic use for ARIs was high in both populations, and focused interventions to improve antibiotic appropriateness for prescribers caring for PWH should be pursued.

Synthesis, Characterization, and Physicochemical Studies Of Orientation-Controlled Multi-Arm PEG Zn(II)/Mg(II) (Aza)Phthalocyanines

Tuning the amphiphilicity of (aza)phthalocyanine hydrophobic cores by introducing multiple polyethylene glycol (PEG) moieties with controlled orientations of their (non)peripheral positions is an innovative approach to fabricating water-soluble macrocyclic materials. Although many water-soluble PEGylated macrocycles have been produced in this way, the ability to generate substances with PEG tails oriented outward from the macrocyclic plane in order to obtain non-aggregated, water soluble forms remains a challenge. In this study, we resolved this issue by developing a methods for the synthesis of four new dual directional PEG containing Zn(II)/Mg(II) amphiphiles (ZnPc-PEG, MgPc-PEG, ZnAzaPc-PEG and MgAzaPc-PEG). In addition, the non-aggregating behaviour, and photophysical and photochemical properties of these PEG-complexes were elucidated.

Euglenatides, Potent Antiproliferative Cyclic Peptides Isolated from the Freshwater Photosynthetic Microalga Euglena gracilis

By limiting the nitrogen source to glutamic acid, we isolated cyclic peptides from Euglena gracilis containing asparagine and non-proteinogenic amino acids. Structure elucidation was accomplished through spectroscopic methods, mass spectrometry and chemical degradation. The euglenatides potently inhibit pathogenic fungi and cancer cell lines e.g., euglenatide B exhibiting IC50 values of 4.3 μM in Aspergillus fumigatus and 0.29 μM in MCF-7 breast cancer cells. In an unprecedented convergence of non-ribosomal peptide synthetase and polyketide synthase assembly-line biosynthesis between unicellular species and the metazoan kingdom, euglenatides bear resemblance to nemamides from Caenorhabditis elegans and inhibited both producing organisms E. gracilis and C. elegans. By molecular network analysis, we detected over forty euglenatide-like metabolites in E. gracilis, E. sanguinea and E. mutabilis, suggesting an important biological role for these natural products.

Growth vector elaboration of fragments: regioselective functionalization of 5-hydroxy-6-azaindazole and 3-hydroxy-2,6-naphtyridine

This article discusses the reactivity of an 6-azaindazole (1) and a 2,6-naphthyridine (2), proposed to be “heteroaromatic rings of the future” which would be useful for fragment-based drug discovery (FBDD)...

From Hit Seeking to Magic Bullets: The Successful Union of Epigenetic and Fragment Based Drug Discovery (EPIDD + FBDD)

We review progress in the application of fragment-based drug discovery (FBDD) to epigenetic drug discovery (EPIDD) targeted at epigenetic writer and eraser enzymes as well as reader domains over the last 15 years. The greatest successes to date are in prospecting for bromodomain binding ligands. From a diverse array of fragment hits, multiple potent and selective compounds ensued, including the oncology clinical candidates mivebresib, ABBV-744, pelabresib, and PLX51107.

Factors associated with erectile dysfunction diagnosis in men with HIV infection: a case-control study

OBJECTIVES

HIV infection is associated with increased risk of erectile dysfunction (ED); however, factors associated with ED remain unclear. We evaluated the prevalence of ED among men living with HIV and factors associated with ED diagnosis in the US Military HIV Natural History Study (NHS).

METHODS

A retrospective cohort study evaluated participants in the NHS, a cohort of HIV-positive active duty members and beneficiaries with HIV infection. Men with a diagnosis of ED after HIV diagnosis were included. Cohort controls without ED diagnosis were matched 2:1 by age at HIV diagnosis and duration of follow-up. Multivariate logistic regression models were used to identify factors associated with ED.

RESULTS

A total of 543 of 5682 male participants (9.6% prevalence) had a diagnosis of ED, of whom 488 were included in the analysis. The median (interquartile range, IQR) age at ED diagnosis was 43 (37.0-49.0) years and the time from HIV diagnosis to antiretroviral therapy (ART) start was longer for cases (5.0 years, IQR: 2.0-9.0) than for controls (3.0 years, 1.0-6.0; P < 0.01). Cases had higher proportions of multiple comorbid conditions, including depression (33.4% vs. 21.7%), tobacco use (19.7% vs. 9.0%) and sleep apnoea (14.8% vs. 4.2%) compared with controls (P < 0.01 for all). Logistic regression showed increased odds of ED for delayed ART initiation > 4 years [odds ratio (OR) = 2.05, 95% confidence interval (CI): 1.56-2.71], protease inhibitor use ≥ 1 year (OR = 1.81, 95% CI: 1.38-2.38) and sleep apnoea (OR = 2.60, 95% CI: 1.68-4.01).

CONCLUSIONS

Erectile dysfunction was common in men with HIV and associated factors included both HIV-related and traditional factors.

Synthesis of Carboxamide-Containing Tranylcypromine Analogues as LSD1 (KDM1A) Inhibitors Targeting Acute Myeloid Leukemia

Lysine-specific demethylase 1 (LSD1/KDM1A) oxidatively removes methyl groups from histone proteins, and its aberrant activity has been correlated with cancers including acute myeloid leukemia (AML). We report a novel series of tranylcypromine analogues with a carboxamide at the 4-position of the aryl ring. These compounds, such as 5 a and 5 b with benzyl and phenethylamide substituents, respectively, had potent sub-micromolar IC50 values for the inhibition of LSD1 as well as cell proliferation in a panel of AML cell lines. The dose-dependent increase in cellular expression levels of H3K4me2, CD86, CD11b and CD14 supported a mechanism involving LSD1 inhibition. The tert-butyl and ethyl carbamate derivatives of these tranylcypromines, although inactive in LSD1 inhibition, were of similar potency in cell-based assays with a more rapid onset of action. This suggests that carbamates can act as metabolically labile tranylcypromine prodrugs with superior pharmacokinetics.

Insights into the Structure-Activity Relationship of Glycosides as Positive Allosteric Modulators Acting on P2X7 Receptors

P2X7 is an important ligand-gated ion channel expressed in multiple immune cell populations. This study aimed to investigate the chemical requirements of triterpenoid glycosides within a new binding pocket to characterize the structure-activity relationship. A set of glycosides were screened for positive modulator activity at human P2X7 using a YO-PRO-1 dye uptake assay in HEK-293 cells stably expressing the wild-type human P2X7 variant (HEK-hP2X7 cells). The highest positive modulator activity was with ginsenoside–compound K (CK), containing a monosaccharide (glucose) attached at carbon-20. Ginsenoside-20(S)-Rg3, containing a disaccharide group (glucose-glucose) at carbon-3, displayed positive modulator activity with a reduced EC₅₀ for ATP and increased maximal response at human P2X7. The epimer 20(R)-Rg3 was inactive. A similar stereo-specific pattern was observed for 20(S)-Rh2. Ginsenoside-F1, highly similar to ginsenoside-CK but containing a single additional hydroxyl group, was also inactive at P2X7. Computational docking suggests hydrophobic residues in the pocket are involved in steric discrimination between triterpenoids, whereas the position and identity of the carbohydrate group are important for positive modulator activity at human P2X7. Ginsenosides containing monosaccharide attachments perform better than di- or trisaccharide glycosides. Additional modifications to the triterpenoid scaffold at carbon-6 are not tolerated. Gypenosides from plant sources other than Panax ginseng (gypenoside XVII, gypenoside XLIX, stevenleaf) can also act as positive allosteric modulators of P2X7. We also investigated the effect of positive allosteric modulators on endogenous P2X7 in THP-1 monocytes and confirmed our findings in a calcium response assay. A cell viability assay showed potentiation of ATP-induced cell death with ginsenoside-CK in THP-1 and HEK-hP2X7 cells.

Three cheers for nitrogen: aza-DKPs, the aza analogues of 2,5-diketopiperazines

Nitrogen-containing heterocycles represent a major source of pharmacological probes and drug candidates. To extend their molecular diversity and their potential biological activities, it is of importance to design and synthesize new N-heterocyclic scaffolds. Therefore, aza-diketopiperazines (aza-DKPs), the aza analogues of well-known 2,5-diketopiperazines (DKPs), emerged as a promising new scaffold. Although the first synthesis of an aza-DKP dates from 1951, significant developments have been made during the last decade. This feature article summarizes the different synthetic strategies to access and functionalise aza-DKPs. Their biological properties and potential applications in medicinal chemistry and drug discovery are discussed as well.

Trends in complications and mortality following catheter ablation of atrial fibrillation: results from 22,582 ablations in Australia and New Zealand from 2010 to 2015

Background

Recent studies from the United States report rising rates of in-hospital complications and mortality following catheter ablation of atrial fibrillation (AF) but whether such a trend is observed in other populations is uncertain.

Purpose

To examine the trends in complications and mortality following AF ablations up to 30 days after discharge in Australia and New Zealand (ANZ) using nationwide data.

Methods

All patients ≥18y undergoing catheter ablation of AF from 2010–2015 were identified using hospitalisation data from all public and most private hospitals in ANZ. The primary endpoint was one or more procedural complications during the hospital stay or within 30 days of discharge. The secondary endpoints were mortality and other specific complications. Unadjusted trend was evaluated using Cochran-Armitage test while that of complications, adjusting for differences in other characteristics, was evaluated using multivariate logistic regression with the year of ablation modelled as a continuous variable. Results are reported as odd ratios (OR) and 95% confidence intervals (CI).

Results

A total of 22,582 AF ablations were included (mean age 62.2±11.6y, 29.1% female, 94.4% elective procedures). The number of ablations increased by 26.4% during the study period (3,097 in 2010 to 3,915 in 2015). Rates of heart failure (8.98% to 10.09%, p for trend=0.010), diabetes (4.52% to 12.46%, p&lt;0.001), chronic kidney disease (2.36% to 4.29%, p&lt;0.001) significantly increased over time but that of hypertension decreased (15.27% to 12.29%, p&lt;0.001). The incidence of overall complications (6.55% in 2010 to 6.67% in 2015, OR 0.99, 95% CI 0.96–1.03) was unchanged during the study period (Figure 1A). When individual complications were considered, mortality rate was low with no statistically significant change with time (0.19% to 0.15%, OR 1.03, 95% CI 0.84–1.28) (Figure 1A) while the rate of acute kidney injury (0.23% to 0.51%, OR 1.17, 95% CI 1.02–1.34) increased and that of venous thromboembolism (0.16% to 0.0%, OR 0.71, 95% CI 0.54–0.94) decreased (Figure 1B). Though the incidence of any bleeding (4.49% to 3.98%, OR 0.97, 95% CI 0.93–1.01) was unchanged, that of major bleeding requiring blood transfusion (0.97% to 0.64%, OR 0.87, 95% CI 0.79–0.96) declined significantly (Figure 1B). No significant trend was observed in other complications or when in-hospital (5.13% to 5.21%, OR 1.00, 95% CI 0.97–1.04) and post-discharge (1.55% to 1.63%, OR 0.97, 95% CI 0.91–1.03) complications were separately evaluated.

Conclusions

Though more patients with heart failure, diabetes and chronic kidney disease underwent catheter ablation of AF over time in ANZ, the overall complication rate was unchanged with a significant decrease in the incidences of major bleeding and venous thromboembolism. However, rate of acute kidney injury nearly doubled, and this could be a potential target for efforts to further improve procedural safety.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): The National Heart Foundation of Australia

Differences between public and private hospitals in complications following catheter ablation of atrial fibrillation: a cohort study in Australia

Background

Comparing outcomes of care between public and private hospitals is critical to inform patients and improve care quality.

Purpose

To compare complication rates following catheter ablation of atrial fibrillation (AF) up to 30-days post discharge between public and private hospitals.

Methods

We included patients ≥18 years who underwent AF ablation in the Australian states of New South Wales, Queensland, Victoria, and Western Australia from 2010–2015. The primary outcome was the occurrence of any complication up to 30-days after discharge. The association between provider type and the risk of complications was examined using logistic regression with inverse probability of treatment weighting (IPTW) propensity scores to account for differences in measured confounders. The minimum strength of association required for an unmeasured confounder to nullify any observed association was estimated using the E value.

Results

We identified 18,074 AF ablations during the study period (mean age 62.3±11.4y, 28.8% female, 78.4% performed in private hospitals). Patients ablated at public hospitals were younger (59.3 vs. 63.1y, p&lt;0.001) but had higher rates of heart failure (10.3% vs. 7.7%, p&lt;0.001), diabetes (10.9% vs. 7.9%, p&lt;0.001), chronic kidney disease (4.9% vs. 2.2%, p&lt;0.001), and chronic lung diseases (4.2% vs. 3.6%, p=0.046) than those at private hospitals. The unadjusted rate of complications was higher in publics hospitals compared with private ones (7.59% vs. 5.26%, p&lt;0.001). After IPTW, there was good covariate balance with a median standardised difference of 0.006 (range 0.0–0.032) and the adjusted difference in procedural complication rates between two sectors remained significant (OR=1.46, 95% CI 1.24–1.73). The difference was mainly driven by an elevated risk of complications requiring cardiac surgery (OR=3.85, 95% CI 1.35–10.98), acute kidney injury (OR=2.95, 95% CI 1.12–7.74), cardiorespiratory failure (OR=2.69, 95% CI 1.19–6.04), postprocedural infection (OR=2.50, 95% CI 1.28–4.86), and bleeding (OR=1.26, 95% CI 1.02–1.56) (Figure 1). The disparity in the complication rates persisted when in-hospital (OR=1.41, 95% CI 1.16–1.70) and post-discharge (OR=1.52, 95% CI 1.12–2.07) complications were analysed separately. The E value was 1.79, suggesting that the disparity might plausibly be explained by unmeasured confounders.

Conclusion

AF ablation at a public hospital was associated with a 46% higher risk of complications compared with ablation at a private hospital, mainly driven by a higher risk of complications requiring cardiac surgery, acute kidney injury, cardiorespiratory failure, infections, and bleeding. The disparity could be due to differences in care quality between two sectors or explained by unmeasured confounders such as higher procedural complexity in public hospitals.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): The National Heart Foundation of Australia

Thirty Years of HDAC Inhibitors: 2020 Insight and Hindsight

It is now 30 years since the first report of a potent zinc-dependent histone deacetylase (HDAC) inhibitor appeared. Since then, five HDAC inhibitors have received regulatory approval for cancer chemotherapy while many others are in clinical development for oncology as well as other therapeutic indications. This Perspective reviews the biological and medicinal chemistry advances over the past 3 decades with an emphasis on the design of selective inhibitors that discriminate between the 11 human HDAC isoforms.

Pharmacological inhibition of lysine-specific demethylase 1 (LSD1) induces global transcriptional deregulation and ultrastructural alterations that impair viability in Schistosoma mansoni

Treatment and control of schistosomiasis still rely on only one effective drug, praziquantel (PZQ) and, due to mass treatment, the increasing risk of selecting for schistosome strains that are resistant to PZQ has alerted investigators to the urgent need to develop novel therapeutic strategies. The histone-modifying enzymes (HMEs) represent promising targets for the development of epigenetic drugs against Schistosoma mansoni. In the present study, we targeted the S. mansoni lysine-specific demethylase 1 (SmLSD1), a transcriptional corepressor, using a novel and selective synthetic inhibitor, MC3935, which was used to treat schistosomula and adult worms in vitro. By using cell viability assays and optical and electron microscopy, we showed that treatment with MC3935 affected parasite motility, egg-laying, tegument, and cellular organelle structures, culminating in the death of schistosomula and adult worms. In silico molecular modeling and docking analysis suggested that MC3935 binds to the catalytic pocket of SmLSD1. Western blot analysis revealed that MC3935 inhibited SmLSD1 demethylation activity of H3K4me1/2. Knockdown of SmLSD1 by RNAi recapitulated MC3935 phenotypes in adult worms. RNA-Seq analysis of MC3935-treated parasites revealed significant differences in gene expression related to critical biological processes. Collectively, our findings show that SmLSD1 is a promising drug target for the treatment of schistosomiasis and strongly support the further development and in vivo testing of selective schistosome LSD1 inhibitors.

Signaling diversity enabled by Rap1-regulated plasma membrane ERK with distinct temporal dynamics

A variety of different signals induce specific responses through a common, extracellular-signal regulated kinase (ERK)-dependent cascade. It has been suggested that signaling specificity can be achieved through precise temporal regulation of ERK activity. Given the wide distrubtion of ERK susbtrates across different subcellular compartments, it is important to understand how ERK activity is temporally regulated at specific subcellular locations. To address this question, we have expanded the toolbox of Förster Resonance Energy Transfer (FRET)-based ERK biosensors by creating a series of improved biosensors targeted to various subcellular regions via sequence specific motifs to measure spatiotemporal changes in ERK activity. Using these sensors, we showed that EGF induces sustained ERK activity near the plasma membrane in sharp contrast to the transient activity observed in the cytoplasm and nucleus. Furthermore, EGF-induced plasma membrane ERK activity involves Rap1, a noncanonical activator, and controls cell morphology and EGF-induced membrane protrusion dynamics. Our work strongly supports that spatial and temporal regulation of ERK activity is integrated to control signaling specificity from a single extracellular signal to multiple cellular processes.

Stereoselective Synthesis of Protected l-allo-Enduracididine and l-Enduracididine via Asymmetric Nitroaldol Reaction

The diastereoselecetive and scalable synthesis of cyclic guanidine-containing nonproteinoginic amino acids, enduracididines, has been achieved. Both diastereomers, l-allo-enduracididine and l-enduracididine, were prepared via catalyst-controlled asymmetric nitroaldol reaction with the aldehyde precursor derived from l-aspartic acid. The cyclic guanidine of di-Cbz-protected l-allo-enduracididine was fully protected with an allyl group to suppress nucleophilic side reactions. Introduced allyl group was efficiently removed via π-allylpalladium chemistry without attaching the Cbz group on the cyclic guanidine moiety.

A Decade of Antifungal Leads from Natural Products: 2010-2019

In this review, we discuss novel natural products discovered within the last decade that are reported to have antifungal activity against pathogenic species. Nearly a hundred natural products were identified that originate from bacteria, algae, fungi, sponges, and plants. Fungi were the most prolific source of antifungal compounds discovered during the period of review. The structural diversity of these antifungal leads encompasses all the major classes of natural products including polyketides, shikimate metabolites, terpenoids, alkaloids, and peptides.

The timeline of epigenetic drug discovery: from reality to dreams

The flexibility of the epigenome has generated an enticing argument to explore its reversion through pharmacological treatments as a strategy to ameliorate disease phenotypes. All three families of epigenetic proteins—readers, writers, and erasers—are druggable targets that can be addressed through small-molecule inhibitors. At present, a few drugs targeting epigenetic enzymes as well as analogues of epigenetic modifications have been introduced into the clinic use (e.g. to treat haematological malignancies), and a wide range of epigenetic-based drugs are undergoing clinical trials. Here, we describe the timeline of epigenetic drug discovery and development beginning with the early design based solely on phenotypic observations to the state-of-the-art rational epigenetic drug discovery using validated targets. Finally, we will highlight some of the major aspects that need further research and discuss the challenges that need to be overcome to implement epigenetic drug discovery into clinical management of human disorders. To turn into reality, researchers from various disciplines (chemists, biologists, clinicians) need to work together to optimise the drug engineering, read-out assays, and clinical trial design.

P347Complications of catheter ablation for atrial fibrillation: a nation-wide study in Australia and New Zealand

Background

It is important to investigate complications of catheter ablation for atrial fibrillation (AF) - an increasingly common procedure - to inform patients and guide efforts to improve procedural quality. However, clinical trials and registries are limited by selection bias, while existing population-based studies either lack nation-wide data, or fail to report post-discharge complications. The timing and impact of these complications are also poorly understood.

Purpose

To obtain unbiased and comprehensive estimates of complications of AF ablations using national data from Australia and New Zealand. We also evaluated the impact of in-hospital complications on the length of stay and assessed the timing of post-discharge complications.

Methods

We included patients aged ≥18 years undergoing catheter ablation with a primary diagnosis of AF between 2010–2015 in all public and most private hospitals in Australia and New Zealand. The primary outcome was the occurrence of major complications in-hospital or up to 30-days after discharge. We identified major complications based on a literature review and expert clinical opinion and defined these using International Classification of Diseases – 10th revision, Australian Modification diagnoses codes and Australian Classification of Health Interventions procedure codes. We determined the impact of in-hospital complications on the length of stay, adjusting for other covariates, by using negative binomial regression, and reported results as incident rate ratio (IRR) and 95% confidence intervals (CI). Time to first post-discharge complication was evaluated using Kaplan Meier survival analysis.

Results

A total of 20,057 AF ablations were included (mean age 62.1±11.6 y, 56.7% ≤65 years old; 29.2% female; median length of stay 1 day). Of these, major complications occurred in 6.3% procedures (4.6% occurring in-hospital and a further 2.0% occurring in the 30-day post discharge). The most common complications were bleeding or haematoma formation and perforation (primarily pericardial effusion), which accounted to 60.3% and 14.3% of all complications, respectively. Rate of procedure-related deaths was 0.1%. Occurrence of an in-hospital complication more than doubled the length of stay (IRR: 2.3, 95% CI 2.2–2.4) with complications requiring cardiac surgery (IRR 4.5, 95% CI 3.2–6.4) and vascular injuries (IRR 3.9, 95% CI 3.1–4.9) having the length of stay prolonged the most (Figure 1A). In the first-week, 67.3% of post-discharge complications had occurred, and this number reached 95% within three-weeks (Figure 1B).

Conclusions

Major complications after AF ablation were common. In-hospital complications doubled the length of stay. Approximately 30% of complications occurred after discharge with the risk highest in the first seven days. Efforts to reduce complications should focus on reducing the incidence of bleeding and pericardial effusions which counted for more than 75% of all complications.

Acknowledgement/Funding

National Heart Foundation of Australia, The Hospital Research Foundation

Isoform-selective HDAC1/6/8 inhibitors with an imidazo-ketopiperazine cap containing stereochemical diversity

A series of hydroxamic acids linked by different lengths to a chiral imidazo-ketopiperazine scaffold were synthesized. The compounds with linker lengths of 6 and 7 carbon atoms were the most potent in histone deacetylase (HDAC) inhibition, and were specific submicromolar inhibitors of the HDAC1, HDAC6 and HDAC8 isoforms. A docking model for the binding mode predicts binding of the hydroxamic acid to the active site zinc cation and additional interactions between the imidazo-ketopiperazine and the enzyme rim. The compounds were micromolar inhibitors of the MV4-11, THP-1 and U937 cancer cell lines. Increased levels of histone H3 and tubulin acetylation support a cellular mechanism of action through HDAC inhibition.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.

Epigenetics: the first 25 centuries

Epigenetics is a natural progression of genetics as it aims to understand how genes and other heritable elements are regulated in eukaryotic organisms. The history of epigenetics is briefly reviewed, together with the key issues in the field today. This themed issue brings together a diverse collection of interdisciplinary reviews and research articles that showcase the tremendous recent advances in epigenetic chemical biology and translational research into epigenetic drug discovery.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.

Epigenetic drug discovery: a success story for cofactor interference

Within the past two decades, seven epigenetic drugs have received regulatory approval and numerous other candidates are currently in clinical trials. Among the epigenetic targets are the writer and eraser enzymes that are, respectively, responsible for the reversible introduction and removal of structural modifications in the nucleosome. This review discusses the progress achieved in the design and development of inhibitors against the key writer and eraser pairs: DNA methyltransferases and Tet demethylases; lysine/arginine methyltransferases and lysine demethylases; and histone acetyltransferases and histone deacetylases. A common theme for the successful inhibition of these enzymes in a potent and selective manner is the targeting of the cofactors present in the active site, namely zinc and iron cations, S-adenosylmethione, nicotinamide adenine dinucleotide, flavin adenine dinucleotide and acetyl Coenzyme A.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.

Synthesis of breast cancer targeting conjugate of temporin-SHa analog and its effect on pro- and anti-apoptotic protein expression in MCF-7 cells

The frog natural product temporin-SHa (FLSGIVGMLGKLF_amide) is a potent antimicrobial peptide, as is the analog [S3K]SHa. By solid-phase synthesis, we prepared temporin-SHa and several temporin-SHa analogs with one or more D-alanine residues incorporated. The natural product and the analog [G10a]SHa were found to be cytotoxic in mammalian cell lines and induce cell death. To achieve selectivity, we conjugated the analog [G10a]SHa with a breast cancer targeting peptide (BCTP). The resulting peptide temporin [G10a]SHa-BCTP conjugate was selectively active against the MCF-7 breast cancer cell line with no cytotoxicity in NIH-3T3 fibroblasts. Unlike the natural product or [G10a]SHa, the conjugated peptide induced apoptosis, downregulating the expression of Bcl-2 and survivin and upregulating Bax and caspase-3.

β-amino alcohols and their respective 2-phenyl-N-alkyl aziridines as potential DNA minor groove binders

It is known that aziridines and nitrogen mustards exert their biological activities, especially in chemotherapy, via DNA alkylation. The studied scaffold, 2-phenyl-1-aziridine, provides a distinct conformation compared to commonly used aziridines, and therefore, leads to a change in high-strained ring reactivity towards biological nucleophiles, such as DNA. The above series of compounds was tested in three breast cell lines: MCF-10, a healthy cell; MCF-7, a hormone responsive cancer cell; and MDA-MB-231, a triple negative breast cancer cell. Both aziridines and their precursors, β-amino alcohols, showed activity towards these cells, and some of the compounds showed higher selectivity index than cisplatin, the drug used as control. When the type of cell death was investigated, the synthesized compounds demonstrated higher apoptosis and lower necrosis rates than cisplatin, and when the mechanism of action was studied, the compounds were shown to interact with DNA via its minor groove instead of alkylation or intercalation.

Systematic Analysis of the Relationship among 3D Structure, Bioactivity, and Membrane Permeability of PF1171F, a Cyclic Hexapeptide with Paralyzing Effects on Silkworms

PF1171 hexapeptides, a family of cyclic hexapeptides produced by fungi, exhibit paralyzing effects on the larvae of silkworms via oral administration. To elucidate the structural features of PF1171 hexapeptides that are crucial for bioactivity, the relationship among 3D structure, bioactivity, and membrane permeability of PF1171F (the peptide with the highest bioavailability) was systematically analyzed through the synthesis of 22 analogues. The PF1171F analogues were prepared by the solid-phase synthesis of a linear precursor and subsequent solution-phase macrolactamization. Analysis by NMR spectroscopy and molecular modeling indicated that the major 3D conformations of PF1171F in various solvents resemble its X-ray crystal structure. The analogues with this conformation tend to exhibit potent paralysis against silkworms, indicating the significance of the conformation in the paralysis. The biological activity was dependent on the mode of administration, varying between hemolymph injection and oral administration. Parallel artificial membrane permeability assay (PAMPA) of the analogues revealed a correlation between membrane permeabilities and paralytic activity by hemolymph injection, indicating that the target molecule of PF1171F is present inside the cell membrane.

LSD1 inhibition attenuates androgen receptor V7 splice variant activation in castration resistant prostate cancer models

BACKGROUND

Castrate resistant prostate cancer (CRPC) is often driven by constitutively active forms of the androgen receptor such as the V7 splice variant (AR-V7) and commonly becomes resistant to established hormonal therapy strategies such as enzalutamide as a result. The lysine demethylase LSD1 is a co-activator of the wild type androgen receptor and a potential therapeutic target in hormone sensitive prostate cancer. We evaluated whether LSD1 could also be therapeutically targeted in CRPC models driven by AR-V7.

METHODS

We utilised cell line models of castrate resistant prostate cancer through over expression of AR-V7 to test the impact of chemical LSD1 inhibition on AR activation. We validated findings through depletion of LSD1 expression and in prostate cancer cell lines that express AR-V7.

RESULTS

Chemical inhibition of LSD1 resulted in reduced activation of the androgen receptor through both the wild type and its AR-V7 splice variant forms. This was confirmed and validated in luciferase reporter assays, in LNCaP and 22Rv1 prostate cancer cell lines and in LSD1 depletion experiments.

CONCLUSION

LSD1 contributes to activation of both the wild type and V7 splice variant forms of the androgen receptor and can be therapeutically targeted in models of CRPC. Further development of this approach is warranted.

The histone deacetylase inhibitor, romidepsin, as a potential treatment for pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease that usually affects elderly people. It has a poor prognosis and there are limited therapies. Since epigenetic alterations are associated with IPF, histone deacetylase (HDAC) inhibitors offer a novel therapeutic strategy to address the unmet medical need. This study investigated the potential of romidepsin, an FDA-approved HDAC inhibitor, as an anti-fibrotic treatment and evaluated biomarkers of target engagement that may have utility in future clinical trials. The anti-fibrotic effects of romidepsin were evaluated both in vitro and in vivo together with any harmful effect on alveolar type II cells (ATII). Bronchoalveolar lavage fluid (BALF) from IPF or control donors was analyzed for the presence of lysyl oxidase (LOX). In parallel with an increase in histone acetylation, romidepsin potently inhibited fibroblast proliferation, myofibroblast differentiation and LOX expression. ATII cell numbers and their lamellar bodies were unaffected. In vivo, romidepsin inhibited bleomycin-induced pulmonary fibrosis in association with suppression of LOX expression. LOX was significantly elevated in BALF of IPF patients compared to controls. These data show the anti-fibrotic effects of romidepsin, supporting its potential use as novel treatment for IPF with LOX as a companion biomarker for evaluation of early on-target effects.