Repurposing amine and carboxylic acid building blocks with an automatable esterification reaction

New methodologies to unite amines and carboxylic acids that complement the popular amide coupling can significantly expand accessible chemical space if they yield products distinct from the classic R-NHC(O)-R' amide arrangement. Here we have developed an amine-acid esterification reaction based on pyridinium salt activation of amine C-N bonds to create products of type R-OC(O)-R' upon reaction with alkyl and aryl carboxylic acids. The protocol is robust and facile as demonstrated by automation on open-source robotics.

In Vitro Evaluation and Mitigation of Niclosamide's Liabilities as a COVID-19 Treatment

Niclosamide, an FDA-approved oral anthelmintic drug, has broad biological activity including anticancer, antibacterial, and antiviral properties. Niclosamide has also been identified as a potent inhibitor of SARS-CoV-2 infection in vitro, generating interest in its use for the treatment or prevention of COVID-19. Unfortunately, there are several potential issues with using niclosamide for COVID-19, including low bioavailability, significant polypharmacology, high cellular toxicity, and unknown efficacy against emerging SARS-CoV-2 variants of concern. In this study, we used high-content imaging-based immunofluorescence assays in two different cell models to assess these limitations and evaluate the potential for using niclosamide as a COVID-19 antiviral. We show that despite promising preliminary reports, the antiviral efficacy of niclosamide overlaps with its cytotoxicity giving it a poor in vitro selectivity index for anti-SARS-CoV-2 inhibition. We also show that niclosamide has significantly variable potency against the different SARS-CoV-2 variants of concern and is most potent against variants with enhanced cell-to-cell spread including the B.1.1.7 (alpha) variant. Finally, we report the activity of 33 niclosamide analogs, several of which have reduced cytotoxicity and increased potency relative to niclosamide. A preliminary structure-activity relationship analysis reveals dependence on a protonophore for antiviral efficacy, which implicates nonspecific endolysosomal neutralization as a dominant mechanism of action. Further single-cell morphological profiling suggests niclosamide also inhibits viral entry and cell-to-cell spread by syncytia. Altogether, our results suggest that niclosamide is not an ideal candidate for the treatment of COVID-19, but that there is potential for developing improved analogs with higher clinical translational potential in the future.

In Vitro Evaluation and Mitigation of Niclosamide’s Liabilities as a COVID-19 Treatment.. [PMID: 35860224 PMCID: PMC9298134 DOI: 10.1101/2022.06.24.497526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Niclosamide, an FDA-approved oral anthelmintic drug, has broad biological activity including anticancer, antibacterial, and antiviral properties. Niclosamide has also been identified as a potent inhibitor of SARS-CoV-2 infection in vitro, generating interest in its use for the treatment or prevention of COVID-19. Unfortunately, there are several potential issues with using niclosamide for COVID-19, including low bioavailability, significant polypharmacology, high cellular toxicity, and unknown efficacy against emerging SARS-CoV-2 variants of concern. In this study, we used high-content imaging-based immunofluorescence assays in two different cell models to assess these limitations and evaluate the potential for using niclosamide as a COVID-19 antiviral. We show that despite promising preliminary reports, the antiviral efficacy of niclosamide overlaps with its cytotoxicity giving it a poor in vitro selectivity index for anti-SARS-CoV-2 inhibition. We also show that niclosamide has significantly variable potency against the different SARS-CoV-2 variants of concern and is most potent against variants with enhanced cell-to-cell spread including B.1.1.7. Finally, we report the activity of 33 niclosamide analogs, several of which have reduced cytotoxicity and increased potency relative to niclosamide. A preliminary structure-activity relationship analysis reveals dependence on a protonophore for antiviral efficacy, which implicates nonspecific endolysosomal neutralization as a dominant mechanism of action. Further single-cell morphological profiling suggests niclosamide also inhibits viral entry and cell-to-cell spread by syncytia. Altogether, our results suggest that niclosamide is not an ideal candidate for the treatment of COVID-19, but that there is potential for developing improved analogs with higher clinical translational potential in the future.

Gene-Guided Discovery and Ribosomal Biosynthesis of Moroidin Peptides

Moroidin is a bicyclic plant octapeptide with tryptophan side-chain cross-links, originally isolated as a pain-causing agent from the Australian stinging tree Dendrocnide moroides. Moroidin and its analog celogentin C, derived from Celosia argentea, are inhibitors of tubulin polymerization and, thus, lead structures for cancer therapy. However, low isolation yields from source plants and challenging organic synthesis hinder moroidin-based drug development. Here, we present biosynthesis as an alternative route to moroidin-type bicyclic peptides and report that they are ribosomally synthesized and posttranslationally modified peptides (RiPPs) derived from BURP-domain peptide cyclases in plants. By mining 793 plant transcriptomes for moroidin core peptide motifs within BURP-domain precursor peptides, we identified a moroidin cyclase in Japanese kerria, which catalyzes the installation of the tryptophan-indole-centered macrocyclic bonds of the moroidin bicyclic motif in the presence of cupric ions. Based on the kerria moroidin cyclase, we demonstrate the feasibility of producing diverse moroidins including celogentin C in transgenic tobacco plants and report specific cytotoxicity of celogentin C against a lung adenocarcinoma cancer cell line. Our study sets the stage for future biosynthetic development of moroidin-based therapeutics and highlights that mining plant transcriptomes can reveal bioactive cyclic peptides and their underlying cyclases from new source plants.

Discovery and biosynthesis of cyclic plant peptides via autocatalytic cyclases

Many bioactive plant cyclic peptides form side-chain-derived macrocycles. Lyciumins, cyclic plant peptides with tryptophan macrocyclizations, are ribosomal peptides (RiPPs) originating from repetitive core peptide motifs in precursor peptides with plant-specific BURP (BNM2, USP, RD22 and PG1beta) domains, but the biosynthetic mechanism for their formation has remained unknown. Here, we characterize precursor-peptide BURP domains as copper-dependent autocatalytic peptide cyclases and use a combination of tandem mass spectrometry-based metabolomics and plant genomics to systematically discover five BURP-domain-derived plant RiPP classes, with mono- and bicyclic structures formed via tryptophans and tyrosines, from botanical collections. As BURP-domain cyclases are scaffold-generating enzymes in plant specialized metabolism that are physically connected to their substrates in the same polypeptide, we introduce a bioinformatic method to mine plant genomes for precursor-peptide-encoding genes by detection of repetitive substrate domains and known core peptide features. Our study sets the stage for chemical, biosynthetic and biological exploration of plant RiPP natural products from BURP-domain cyclases.

Targeted case finding for hepatitis B using dry blood spot testing in the British-Chinese and South Asian populations of the North-East of England

Chronic infection with the hepatitis B virus (HBV) is a frequent cause of cirrhosis and liver cancer. Targeted HBV screening is recommended by the Centre for Disease Control (CDC) and Prevention for subjects born in countries with >2% HBV prevalence. However, there are no UK guidelines. Here, we applied the (CDC) recommendations to the British-Chinese and British-South Asian community of North-East (NE) England. British-Chinese and South Asian subjects were invited to attend for HBV education and screening sessions held in community centres. Hepatitis B surface antigen (HBsAg) and hepatitis B core total antibody (HBcAb) were tested with dry blood spot tests. South Asians were also tested for hepatitis C antibody (HCVAb). A total of 1126 subjects (606 Chinese and 520 South Asian) were screened. Sixty-two (5.5%) were HBsAg positive. Ten of these reported a previous diagnosis of HBV. The prevalence of HBsAg positivity was 4.6% when previously diagnosed individuals were excluded. The HBsAg prevalence was significantly higher in the Chinese subjects compared with South Asians (8.7% VS. 1.7% P < 0.001). In Chinese subjects, HBsAg positivity was highest in subjects born in Vietnam (17.4%), followed by China (11%), Hong Kong (7.8%) and the UK (6.7%). Subjects from Pakistan had the highest HBsAg and HCV Ab prevalence in the South Asians (3.1% and 1.8%, respectively). Ten percentage of HBsAg positive patients who had follow-up assessment had active disease requiring antiviral treatment. Undiagnosed HBV infection was above the 2% threshold for screening suggested by the CDC in the British-Chinese and Pakistani community of NE England, which provides evidence for a UK HBV-targeted screening programme.

Is formal training necessary for capsule endoscopy? The largest gastroenterology trainee study with controls

BACKGROUND

Little is known about the infrastructure to train gastroenterologists in capsule endoscopy. The level of capsule endoscopy exposure among trainees in the United Kingdom or Europe has also not been quantified.

AIMS AND METHODS

To assess the ability of 10 gastroenterology trainees with endoscopy experience to interpret 10 capsule endoscopy videos against five medical students, with an expert in capsule endoscopy as the gold standard. Parameters assessed included gastric emptying time, small bowel transit and the diagnosis made. A questionnaire survey assessed the level of capsule endoscopy exposure among United Kingdom trainees.

RESULTS

Trainees were better at determining the gastric emptying time (p=0.013) and more likely to record true positives compared to the students (p=0.037). They were also less likely to record false positives (p=0.005) and more likely to reach the correct diagnosis (p=0.001, OR 3.6, CI 1.8-7.4). Our survey found that, 65% of trainees had prior exposure to capsule endoscopy but only 13% had done capsule endoscopy reporting. Sixty seven percent felt capsule endoscopy should be incorporated into their training.

CONCLUSION

This study has shown that prior endoscopic experience enables trainees to interpret capsule endoscopy more accurately than medical students. However, there is a demand for focussed training which would enable trainees to reliably interpret pathology on capsule endoscopy.