Biology subjects

Gilbert, I. H.

Publications and source records attributed to Gilbert, I. H..

8 recordsLinked to original sources

bioRxiv2025

Use of a cytochrome P450 humanised mouse model to refine schistosomiasis drug discovery.

Control of schistosomiasis, a neglected tropical disease caused by infection with Schistosoma spp., remains reliant on a single chemotherapy, praziquantel (PZQ). This strategy presents a risk to global health should PZQ-resistant schistosomes establish in endemic areas and justifies the search for new drugs. However, species-specific metabolic differences between humans and preclinical models hinder the optimisation of next-generation anti-schistosomal therapeutics. Here, to bypass these species-specific limitations, we exploited a humanised mouse model, 8HUM, engineered to express the principal human Phase I cytochrome P450 enzymes (CYP1A1/2, CYP2C9, CYP2D6, CYP3A4/7) as well as the transcription factors constitutive androstane receptor (CAR) and pregnane X receptor (PXR) in place of 35 murine orthologues. We characterised S. mansoni development, immunopathology, hepatic transcriptomic responses, intestinal microbiome changes and PZQ metabolism as well as PZQ efficacy in 8HUM versus wild-type (WT) mice. 8HUM mice supported normal S. mansoni maturation, infection-associated microbiome dysbiosis, Th2-dominant immune responses and characteristic hepatic pathology. PZQ intrinsic clearance in 8HUM hepatic microsomes mirrored human levels and was >10-fold lower than that found for WT microsomes. Oral dosing revealed human-like PZQ exposures of (R)-PZQ and 4OH-PZQ in 8HUM mice at 25 mg/kg bodyweight and >90% reductions in worm burdens at 100 mg/kg bodyweight (equivalent to that seen in WT mice administered PZQ at 400 mg/kg bodyweight). Our results revealed that 8HUM mice recapitulate key features of murine schistosomiasis while exhibiting human-relevant drug metabolism. These findings establish 8HUM as a refined translational platform for anti-schistosomal drug development, improving predictive accuracy and accelerating therapeutic discovery. One Sentence SummaryA cytochrome P450 humanised mouse model is used to study Schistosoma mansoni development, schistosomiasis, drug metabolism and drug efficacy.

pharmacology and toxicology↗

bioRxiv2025

Experience from an HTS campaign: Investigation of susceptibility and rescue of SARS-CoV-2 nsp3 protease assay from metal contamination

Different biochemical assays yield different rates of false positives than others either due to the nature of the enzyme, the technology associated with the assay, or properties of the compounds being screened. Ensuring that the right counter-screens are in place to identify false positives without wasting time and resources on them is of great importance. Herein we describe the results of a high throughput screen (HTS) against non-structural protein 3 (nsp3) protease PLPro, which resulted exclusively in false-positive hits. By triaging hit compounds through purification of metal chelating resin, we identified contamination by either copper or palladium as the most likely source of false positives from the library screening campaign. We then performed a systematic assessment of the vulnerability of nsp3 protease screening to metal contamination and evaluated common additives to combat the inhibitory effects of different metal salts. We further conducted a thorough survey of the literature reports of nsp3 HTS campaigns with a focus on the presence of additives and what metal susceptibility was likely, given the results of our work. We conclude that the majority of reported nsp3 screens are susceptible to copper contamination with a smaller proportion also potentially susceptible to palladium contamination.

biochemistry↗

bioRxiv2025

Crystallographic characterisation and development of bi-substrate inhibitors of coronavirus nsp14 methyltransferase

SARS-CoV-2 non-structural protein 14 (nsp14) is essential for viral mRNA cap guanine-N7 methylation and represents a promising but underexplored antiviral target. Herein we describe a structure-guided campaign based on a hit from a focussed SAM mimetic library. Systematic SAR exploration guided by six X-ray co-crystal structures in complex with SARS-CoV-2 led to compound 26, a bi-substrate inhibitor that bridges the SAM and RNA cap binding sites. Compound 26 achieved nanomolar potency against nsp14 from SARS-CoV-2 (IC50 = 53 nM), SARS-CoV-1, and two alphacoronaviruses, with excellent selectivity over human RNMT and flaviviral MTase. In general, the compounds demonstrated favourable metabolic stability, passive permeability, and no HepG2 cytotoxicity. However, cellular antiviral activity was limited, revealing disconnects between enzyme inhibition and phenotypic response. These findings provide a structural framework for optimizing bi-substrate methyltransferase inhibitors against coronaviruses with a view for pan-coronaviral activity.

biochemistry↗

bioRxiv2025

Small molecule inhibitors of the NorA multidrug efflux pump potentiate antibiotic activity by binding the outward-open conformation

Antibiotic resistance is among the greatest threats of the modern era. Multidrug efflux pumps expel antibiotics from bacterial cells and present a particular challenge by conferring resistance to a broad range of antibiotic classes; however, there is currently a lack of potent and selective inhibitors. Here, we report the discovery of IMP-2380, a drug-like chemical probe for the multidrug efflux pump NorA that delivers low-nanomolar potentiation of ciprofloxacin activity in vitro and activity in an in vivo S. aureus infection model. A phenotypic high-throughput screen for inhibitors of the ciprofloxacin-activated SOS DNA repair pathway in methicillin-resistant Staphylococcus aureus (MRSA) identified hit compounds targeting NorA, and subsequent optimization established IMP-2380 as the most potent NorA inhibitor discovered to date. The structure of NorA bound to IMP-2380 was solved by cryo-electron microscopy at 2.52 [A] resolution, revealing that the small molecule locks the pump in the outward-open conformation. This closes the inner face and prevents antibiotics binding from the cytosol, providing an explanation for the exceptional potency of IMP-2380 and structure-activity relationship across the series. IMP-2380 represents an in vivo active NorA inhibitor, functioning via a structurally defined outward-open binding mode, and will enable future exploration of NorA as a druggable target to combat antibiotic resistance.

biochemistry↗

bioRxiv2025

Identification of a novel false-positive mechanism in RapidFire mass spectrometry and application in drug discovery

False-positives plague High Throughput Screening in general and are costly as they consume resource and time to resolve. Methods that can rapidly identify such compounds at the initial screen are therefore of great value. Advances in mass spectrometry have led to the ability to screen inhibitors in drug discovery applications by direct detection of an enzyme reaction product. The technique is free from some of the artefacts that trouble classical assays such as fluorescence interference. Its direct nature negates the need for coupling enzymes and hence is simpler with fewer opportunities for artefacts. Despite its myriad advantages, we report here a mechanism for false-positive hits which has not been reported in the literature. Further we have developed a pipeline for detecting these false-positive hits and suggest a method to mitigate against them. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=156 HEIGHT=200 SRC="FIGDIR/small/634670v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@a99654org.highwire.dtl.DTLVardef@1cc7ec8org.highwire.dtl.DTLVardef@978abaorg.highwire.dtl.DTLVardef@114c0d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

Sperm Cell Painting: A Mechanism Driven Approach for Drug Discovery in Human Spermatozoa

We have adapted the cell painting assay developed by Carpenter and colleagues on cultured U2OS cells to human spermatozoa. In Sperm Cell Painting (SCP) we assemble an image-based quantitative fingerprint of the functional state of sperm. We use this assay to gain insight into the mechanism of action of compounds that modify sperm function and as a platform for contraceptive discovery.

cell biology↗

bioRxiv2023

Sperm Toolbox - A selection of small molecules to study human spermatozoa

Male contraceptive options and infertility treatments are limited. To help overcome these limitations we established a small molecule library as a toolbox for assay development and screening campaigns using human spermatozoa. We have profiled all compounds in our automated high-throughput screening platform and provide the dataset, which allows direct side-by-side comparisons of compound effects and assays using live human spermatozoa.

pharmacology and toxicology↗

bioRxiv2021

Compounds enhancing human sperm motility identified using a high-throughput phenotypic screening platform

Study questionCan a high-throughput screening platform facilitate male fertility drug discovery? Summary answerA high-throughput screening platform identified a large number of compounds that enhanced sperm motility. What is known alreadySeveral efforts to find small molecules modulating sperm function have been performed but not using high-throughput technology. Study design, size, durationHealthy donor semen samples were used and samples were pooled (3-5 donors per pool). Primary screening was performed in singlicate; dose-response screening was performed in duplicate (independent donor pools). Participants/materials, setting, methodsSpermatozoa isolated from healthy donors were prepared by density gradient centrifugation and incubated in 384-well plates with compounds (6.25 uM) to identify those compounds with enhancing effects on motility. A total of [~]17,000 compounds from the following libraries: ReFRAME, Prestwick, Tocris, LOPAC, CLOUD and MMV Pathogen Box were screened. Dose response experiments of screening hits were performed to confirm the enhancing effect on sperm motility. Experiments were performed in a University setting. Main results and the role of chanceFrom our primary single concentration screening, 105 compounds elicited an enhancing effect on sperm motility compared to DMSO treated wells. Confirmed enhancing compounds were grouped based on their annotated targets/target classes. A major target class, phosphodiesterase inhibitors, were identified in particular PDE10A inhibitors as well as number of compounds not previously identified/known to enhance human sperm motility such as those related to GABA signaling. Limitations, reasons for cautionCompounds have been tested with prepared donor spermatozoa and only incubated for a short period of time. Therefore, the effect of compounds on whole semen or with longer incubation time may be different. All experiments were performed in vitro. Wider implications of the findingsThis phenotypic screening assay identified a large number of compounds that increased sperm motility. In addition to furthering our understanding of human sperm function, for example identifying new avenues for discovery, we highlight potential inhibitors as promising start-point for a medicinal chemistry programme for potential enhancement of male infertility. Moreover, with disclosure of the results of screening we present a substantial resource to inform further work in the field Study funding/competing interest(s)This study was supported by the Bill and Melinda Gates Foundation and Scottish Funding Council and Scottish Universities Life Science Alliance.

physiology↗