Publications by authors named "David R Spring"

190 Publications

Rapid and robust cysteine bioconjugation with vinylheteroarenes.

Chem Sci 2021 Jul 7;12(26):9060-9068. Epub 2021 Jun 7.

Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK

Methods for residue-selective and stable modification of canonical amino acids enable the installation of distinct functionality which can aid in the interrogation of biological processes or the generation of new therapeutic modalities. Herein, we report an extensive investigation of reactivity and stability profiles for a series of vinylheteroarene motifs. Studies on small molecule and protein substrates identified an optimum vinylheteroarene scaffold for selective cysteine modification. Utilisation of this lead linker to modify a number of protein substrates with various functionalities, including the synthesis of a homogeneous, stable and biologically active antibody-drug conjugate (ADC) was then achieved. The reagent was also efficient in labelling proteome-wide cysteines in cell lysates. The efficiency and selectivity of these reagents as well as the stability of the products makes them suitable for the generation of biotherapeutics or studies in chemical biology.
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http://dx.doi.org/10.1039/d1sc02722kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8261766PMC
July 2021

Microscopy and chemical analyses reveal flavone-based woolly fibres extrude from micron-sized holes in glandular trichomes of Dionysia tapetodes.

BMC Plant Biol 2021 Jun 17;21(1):258. Epub 2021 Jun 17.

The Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, CB2 1LR, UK.

Background: Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic "woolly" farina. This contrasts with some related Primula which instead form a fine powder. Farina is formed by specialized cellular factories, a type of glandular trichome, but the precise composition of the fibres and how it exits the cell is poorly understood. Here, using a combination of cell biology (electron and light microscopy) and analytical chemical techniques, we present the principal chemical components of the wool and its mechanism of exit from the glandular trichome.

Results: We show the woolly farina consists of micron-diameter fibres formed from a mixture of flavone and substituted flavone derivatives. This contrasts with the powdery farina, consisting almost entirely of flavone. The woolly farina in D. tapetodes is extruded through specific sites at the surface of the trichome's glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle and forming a tight seal between the fibre and hole. The data is consistent with formation and thread elongation occurring from within the cell.

Conclusions: Our results suggest the composition of the D. tapetodes farina dictates its formation as wool rather than powder, consistent with a model of thread integrity relying on intermolecular H-bonding. Glandular trichomes produce multiple wool fibres by concentrating and maintaining their extrusion at specific sites at the cell cortex of the head cell. As the wool is extensive across the plant, there may be associated selection pressures attributed to living at high altitudes.
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http://dx.doi.org/10.1186/s12870-021-03010-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8210372PMC
June 2021

Demonstration of the utility of DOS-derived fragment libraries for rapid hit derivatisation in a multidirectional fashion.

Chem Sci 2020 May 14;11(39):10792-10801. Epub 2020 May 14.

Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK

Organic synthesis underpins the evolution of weak fragment hits into potent lead compounds. Deficiencies within current screening collections often result in the requirement of significant synthetic investment to enable multidirectional fragment growth, limiting the efficiency of the hit evolution process. Diversity-oriented synthesis (DOS)-derived fragment libraries are constructed in an efficient and modular fashion and thus are well-suited to address this challenge. To demonstrate the effective nature of such libraries within fragment-based drug discovery, we herein describe the screening of a 40-member DOS library against three functionally distinct biological targets using X-Ray crystallography. Firstly, we demonstrate the importance for diversity in aiding hit identification with four fragment binders resulting from these efforts. Moreover, we also exemplify the ability to readily access a library of analogues from cheap commercially available materials, which ultimately enabled the exploration of a minimum of four synthetic vectors from each molecule. In total, 10-14 analogues of each hit were rapidly accessed in three to six synthetic steps. Thus, we showcase how DOS-derived fragment libraries enable efficient hit derivatisation and can be utilised to remove the synthetic limitations encountered in early stage fragment-based drug discovery.
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http://dx.doi.org/10.1039/d0sc01232gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8162264PMC
May 2020

The multifaceted nature of antimicrobial peptides: current synthetic chemistry approaches and future directions.

Chem Soc Rev 2021 Jul;50(13):7820-7880

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

Bacterial infections caused by 'superbugs' are increasing globally, and conventional antibiotics are becoming less effective against these bacteria, such that we risk entering a post-antibiotic era. In recent years, antimicrobial peptides (AMPs) have gained significant attention for their clinical potential as a new class of antibiotics to combat antimicrobial resistance. In this review, we discuss several facets of AMPs including their diversity, physicochemical properties, mechanisms of action, and effects of environmental factors on these features. This review outlines various chemical synthetic strategies that have been applied to develop novel AMPs, including chemical modifications of existing peptides, semi-synthesis, and computer-aided design. We will also highlight novel AMP structures, including hybrids, antimicrobial dendrimers and polypeptides, peptidomimetics, and AMP-drug conjugates and consider recent developments in their chemical synthesis.
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http://dx.doi.org/10.1039/d0cs00729cDOI Listing
July 2021

Chemical probes targeting the kinase CK2: a journey outside the catalytic box.

Org Biomol Chem 2021 05;19(20):4380-4396

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

CK2 is a protein kinase that plays important roles in many physio-pathological cellular processes. As such, the development of chemical probes for CK2 has received increasing attention in the past decade with more than 40 lead compounds developed. In this review, we aim to provide the reader with a comprehensive overview of the chemical probes acting outside the highly-conserved ATP-site developed to date. Such probes belong to different classes of molecules spanning from small molecules to peptides, act with a range of mechanisms of action and some of them present themselves as promising tools to investigate the biology of CK2 and therefore develop therapeutics for many disease areas including cancer and COVID-19.
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http://dx.doi.org/10.1039/d1ob00257kDOI Listing
May 2021

Downfalls of Chemical Probes Acting at the Kinase ATP-Site: CK2 as a Case Study.

Molecules 2021 Mar 31;26(7). Epub 2021 Mar 31.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

Protein kinases are a large class of enzymes with numerous biological roles and many have been implicated in a vast array of diseases, including cancer and the novel coronavirus infection COVID-19. Thus, the development of chemical probes to selectively target each kinase is of great interest. Inhibition of protein kinases with ATP-competitive inhibitors has historically been the most widely used method. However, due to the highly conserved structures of ATP-sites, the identification of truly selective chemical probes is challenging. In this review, we use the Ser/Thr kinase CK2 as an example to highlight the historical challenges in effective and selective chemical probe development, alongside recent advances in the field and alternative strategies aiming to overcome these problems. The methods utilised for CK2 can be applied to an array of protein kinases to aid in the discovery of chemical probes to further understand each kinase's biology, with wide-reaching implications for drug development.
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http://dx.doi.org/10.3390/molecules26071977DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8037657PMC
March 2021

A dual-enzyme cleavable linker for antibody-drug conjugates.

Chem Commun (Camb) 2021 Apr 9;57(28):3457-3460. Epub 2021 Mar 9.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

A novel enzyme cleavable linker for antibody-drug conjugates is reported. The 3-O-sulfo-β-galactose linker is cleaved sequentially by two lysosomal enzymes - arylsulfatase A and β-galactosidase - to release the payload in targeted cells. An α-HER2 antibody-drug conjugate synthesised using this highly hydrophilic dual-cleavable linker exhibited excellent cytotoxicity and selectivity.
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http://dx.doi.org/10.1039/d1cc00957eDOI Listing
April 2021

The role of chemical synthesis in developing RiPP antibiotics.

Chem Soc Rev 2021 Apr 26;50(7):4245-4258. Epub 2021 Feb 26.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

The growing antimicrobial resistance crisis necessitates the discovery and development of novel classes of antibiotics if a 'postantibiotic era' is to be avoided. Ribosomally synthesised and post-translationally modified peptides, or RiPPs, are becoming increasingly recognised as a potential source of antimicrobial drugs. This is due to a combination of their potent antimicrobial activity and their high stability relative to unmodified linear peptides. However, as peptide drugs, their clinical development is often perturbed by issues such as low solubility and poor bioavailability. Chemical synthesis has the potential to overcome some of these challenges. Furthermore, the structural complexity of RiPPs makes them interesting synthetic targets in their own right, with the total synthesis of some structural classes having only been recently realised. This review focusses on the use of RiPPs as antimicrobial agents and will highlight various strategies that have been employed to chemically synthesise three major classes of RiPPs: lasso peptides, cyclotides, and lanthipeptides.
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http://dx.doi.org/10.1039/d0cs01386bDOI Listing
April 2021

Peptides as a platform for targeted therapeutics for cancer: peptide-drug conjugates (PDCs).

Chem Soc Rev 2021 Feb;50(3):1480-1494

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Peptides can offer the versatility needed for a successful oncology drug discovery approach. Peptide-drug conjugates (PDCs) are an emerging targeted therapeutic that present increased tumour penetration and selectivity. Despite these advantages, there are still limitations for the use of peptides as therapeutics exemplified through their slow progression to get into the clinic and limited oral bioavailability. New approaches to address these problems have been studied and successfully implemented to enhance the stability of peptides and their constructs. There is great promise for the future of PDCs with two molecules already on the market and many variations currently undergoing clinical trials, such as bicycle-toxin conjugates and peptide-dendrimer conjugates. This review summarises the entire process needed for the design and successful development of an oncology PDC including chemical and nanomaterial strategies to enhance peptide stability within circulation, the function of each component of a PDC construct, and current examples in clinical trials.
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http://dx.doi.org/10.1039/d0cs00556hDOI Listing
February 2021

Site-selective modification strategies in antibody-drug conjugates.

Chem Soc Rev 2021 Jan 8;50(2):1305-1353. Epub 2020 Dec 8.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Antibody-drug conjugates (ADCs) harness the highly specific targeting capabilities of an antibody to deliver a cytotoxic payload to specific cell types. They have garnered widespread interest in drug discovery, particularly in oncology, as discrimination between healthy and malignant tissues or cells can be achieved. Nine ADCs have received approval from the US Food and Drug Administration and more than 80 others are currently undergoing clinical investigations for a range of solid tumours and haematological malignancies. Extensive research over the past decade has highlighted the critical nature of the linkage strategy adopted to attach the payload to the antibody. Whilst early generation ADCs were primarily synthesised as heterogeneous mixtures, these were found to have sub-optimal pharmacokinetics, stability, tolerability and/or efficacy. Efforts have now shifted towards generating homogeneous constructs with precise drug loading and predetermined, controlled sites of attachment. Homogeneous ADCs have repeatedly demonstrated superior overall pharmacological profiles compared to their heterogeneous counterparts. A wide range of methods have been developed in the pursuit of homogeneity, comprising chemical or enzymatic methods or a combination thereof to afford precise modification of specific amino acid or sugar residues. In this review, we discuss advances in chemical and enzymatic methods for site-specific antibody modification that result in the generation of homogeneous ADCs.
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http://dx.doi.org/10.1039/d0cs00310gDOI Listing
January 2021

Photocatalytic methods for amino acid modification.

Chem Soc Rev 2021 Jan 11;50(1):39-57. Epub 2020 Nov 11.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

Amino acid modification plays an important role across several fields, including synthetic organic chemistry, materials science, targeted drug delivery and the probing of biological function. Although a myriad of methods now exist for the modification of peptides or proteins, many of these target a handful of the most reactive proteinogenic amino acids. Photocatalysis has recently emerged as a mild approach for amino acid modification, generating a sizable toolbox of reactions capable of modifying almost all of the canonical amino acids. These reactions are characterised by their mild, physiologically compatible conditions, greatly enhancing their usefulness for amino acid modification. This review aims to introduce the field of photocatalytic amino acid modification and discusses the most recent advances.
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http://dx.doi.org/10.1039/d0cs00344aDOI Listing
January 2021

Expeditious Total Synthesis of Hemiasterlin through a Convergent Multicomponent Strategy and Its Use in Targeted Cancer Therapeutics.

Angew Chem Int Ed Engl 2020 12 12;59(51):23045-23050. Epub 2020 Oct 12.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Hemiasterlin is an antimitotic marine natural product with reported sub-nanomolar potency against several cancer cell lines. Herein, we describe an expeditious total synthesis of hemiasterlin featuring a four-component Ugi reaction (Ugi-4CR) as the key step. The convergent synthetic strategy enabled rapid access to taltobulin (HTI-286), a similarly potent synthetic analogue. This short synthetic sequence enabled investigation of both hemiasterlin and taltobulin as cytotoxic payloads in antibody-drug conjugates (ADCs). These novel ADCs displayed sub-nanomolar cytotoxicity against HER2-expressing cancer cells, while showing no activity against antigen-negative cells. This study demonstrates an improved synthetic route to a highly valuable natural product, facilitating further investigation of hemiasterlin and its analogues as potential payloads in targeted therapeutics.
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http://dx.doi.org/10.1002/anie.202010090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7756509PMC
December 2020

Efficient and selective antibody modification with functionalised divinyltriazines.

Org Biomol Chem 2020 07;18(25):4739-4743

Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK.

A highly efficient disulfide rebridging strategy for the modification of monoclonal antibodies with substituted divinyltriazine linkers is reported. The reaction proceeds efficiently under mild conditions with near stoichiometric quantities of linker. This method of conjugation yields serum stable antibody conjugates with a controlled payload loading of 4.
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http://dx.doi.org/10.1039/d0ob01002bDOI Listing
July 2020

C(sp)-H arylation to construct all-syn cyclobutane-based heterobicyclic systems: a novel fragment collection.

Chem Commun (Camb) 2020 Jul;56(54):7423-7426

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

All-syn fused cyclobutanes remain an elusive chemotype and thus present an interesting synthetic challenge. Herein, we report the successful application of Pd-catalysed C(sp3)-H arylation of cyclobutane compounds to generate all-syn heterobicyclic fragments using an innovative 'inside-out' approach. Through this strategy we generate a virtual collection of 90 fragments, which we demonstrate to have enhanced three-dimensionality and superior fragment-like properties compared to existing collections.
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http://dx.doi.org/10.1039/d0cc03237aDOI Listing
July 2020

Hydroxylated Rotenoids Selectively Inhibit the Proliferation of Prostate Cancer Cells.

J Nat Prod 2020 06 27;83(6):1829-1845. Epub 2020 May 27.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K.

Prostate cancer is one of the leading causes of cancer-related death in men. The identification of new therapeutics to selectively target prostate cancer cells is therefore vital. Recently, the rotenoids rotenone () and deguelin () were reported to selectively kill prostate cancer cells, and the inhibition of mitochondrial complex I was established as essential to their mechanism of action. However, these hydrophobic rotenoids readily cross the blood-brain barrier and induce symptoms characteristic of Parkinson's disease in animals. Since hydroxylated derivatives of and are more hydrophilic and less likely to readily cross the blood-brain barrier, 29 natural and unnatural hydroxylated derivatives of and were synthesized for evaluation. The inhibitory potency (IC) of each derivative against complex I was measured, and its hydrophobicity (SlogP) predicted. Amorphigenin (), dalpanol (), dihydroamorphigenin (), and amorphigenol () were selected and evaluated in cell-based assays using C4-2 and C4-2B prostate cancer cells alongside control PNT2 prostate cells. These rotenoids inhibit complex I in cells, decrease oxygen consumption, and selectively inhibit the proliferation of prostate cancer cells, leaving control cells unaffected. The greatest selectivity and antiproliferative effects were observed with and . The data highlight these molecules as promising therapeutic candidates for further evaluation in prostate cancer models.
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http://dx.doi.org/10.1021/acs.jnatprod.9b01224DOI Listing
June 2020

General dual functionalisation of biomacromolecules via a cysteine bridging strategy.

Org Biomol Chem 2020 06;18(22):4224-4230

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Site-selective modification of peptides and proteins has resulted in the development of a host of novel tools for the study of cellular systems or the synthesis of enhanced biotherapeutics. There is a need for useful methodologies that enable site-selective modification of native peptides or proteins, which is even more prevalent when modification of the biomolecule with multiple payloads is desired. Herein, we report the development of a novel dual functional divinylpyrimidine (dfDVP) platform that enables robust and modular modification of peptides, antibody fragments and antibodies. These biomacromolecules could be easily functionalised with a range of functional payloads (e.g. fluorescent dyes, cytotoxic warheads or cell-penetrating tags). Importantly, the dual functionalised peptides and antibodies demonstrated exquisite bioactivity in a range of in vitro cellular assays, showcasing the enhanced utility of these bioactive conjugates.
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http://dx.doi.org/10.1039/d0ob00907eDOI Listing
June 2020

An efficient, stereocontrolled and versatile synthetic route to bicyclic partially saturated privileged scaffolds.

Chem Commun (Camb) 2020 Jun;56(50):6818-6821

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Herein, we describe the development of a simple, high yielding and stereocontrolled strategy for the synthesis of a series of triazolopiperazines and other biologically relevant fused scaffolds from optically active amino acids. This route was applied to the synthesis of 22 scaffolds containing new, previously inaccessible vectors and used to access a novel analogue of ganaplacide.
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http://dx.doi.org/10.1039/d0cc02728fDOI Listing
June 2020

Divergent Synthesis of Novel Cylindrocyclophanes that Inhibit Methicillin-Resistant Staphylococcus aureus (MRSA).

ChemMedChem 2020 07 12;15(14):1289-1293. Epub 2020 Jun 12.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

The cylindrocyclophanes are a family of macrocyclic natural products reported to exhibit antibacterial activity. Little is known about the structural basis of this activity due to the challenges associated with their synthesis or isolation. We hypothesised that structural modification of the cylindrocyclophane scaffold could streamline their synthesis without significant loss of activity. Herein, we report a divergent synthesis of the cylindrocyclophane core enabling access to symmetrical macrocycles by means of a catalytic, domino cross-metathesis-ring-closing metathesis cascade, followed by late-stage diversification. Phenotypic screening identified several novel inhibitors of methicillin-resistant Staphylococcus aureus. The most potent inhibitor has a unique tetrabrominated [7,7]paracyclophane core with no known counterpart in nature. Together these illustrate the potential of divergent synthesis using catalysis and unbiased screening methods in modern antibacterial discovery.
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http://dx.doi.org/10.1002/cmdc.202000179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522682PMC
July 2020

Diarylethene moiety as an enthalpy-entropy switch: photoisomerizable stapled peptides for modulating p53/MDM2 interaction.

Org Biomol Chem 2020 07;18(28):5359-5369

Taras Shevchenko National University of Kyiv, Vul. Volodymyrska 60, 01601 Kyiv, Ukraine and Lumobiotics GmbH, Auer Str. 2, 76227, Karlsruhe, Germany.

Analogs of the known inhibitor (peptide pDI) of the p53/MDM2 protein-protein interaction are reported, which are stapled by linkers bearing a photoisomerizable diarylethene moiety. The corresponding photoisomers possess significantly different affinities to the p53-interacting domain of the human MDM2. Apparent dissociation constants are in the picomolar-to-low nanomolar range for those isomers with diarylethene in the "open" configuration, but up to eight times larger for the corresponding "closed" isomers. Spectroscopic, structural, and computational studies showed that the stapling linkers of the peptides contribute to their binding. Calorimetry revealed that the binding of the "closed" isomers is mostly enthalpy-driven, whereas the "open" photoforms bind to the protein stronger due to their increased binding entropy. The results suggest that conformational dynamics of the protein-peptide complexes may explain the differences in the thermodynamic profiles of the binding.
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http://dx.doi.org/10.1039/d0ob00831aDOI Listing
July 2020

2-Aminopyridine Analogs Inhibit Both Enzymes of the Glyoxylate Shunt in .

Int J Mol Sci 2020 Apr 3;21(7). Epub 2020 Apr 3.

Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK.

is an opportunistic pathogen responsible for many hospital-acquired infections. can thrive in diverse infection scenarios by rewiring its central metabolism. An example of this is the production of biomass from C nutrient sources such as acetate via the glyoxylate shunt when glucose is not available. The glyoxylate shunt is comprised of two enzymes, isocitrate lyase (ICL) and malate synthase G (MS), and flux through the shunt is essential for the survival of the organism in mammalian systems. In this study, we characterized the mode of action and cytotoxicity of structural analogs of 2-aminopyridines, which have been identified by earlier work as being inhibitory to both shunt enzymes. Two of these analogs were able to inhibit ICL and MS in vitro and prevented growth of on acetate (indicating cell permeability). Moreover, the compounds exerted negligible cytotoxicity against three human cell lines and showed promising in vitro drug metabolism and safety profiles. Isothermal titration calorimetry was used to confirm binding of one of the analogs to ICL and MS, and the mode of enzyme inhibition was determined. Our data suggest that these 2-aminopyridine analogs have potential as anti-pseudomonal agents.
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http://dx.doi.org/10.3390/ijms21072490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177833PMC
April 2020

Hotspots API: A Python Package for the Detection of Small Molecule Binding Hotspots and Application to Structure-Based Drug Design.

J Chem Inf Model 2020 04 2;60(4):1911-1916. Epub 2020 Apr 2.

The Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge, CB2 1EZ, U.K.

Methods that survey protein surfaces for binding hotspots can help to evaluate target tractability and guide exploration of potential ligand binding regions. Fragment Hotspot Maps builds upon interaction data mined from the CSD (Cambridge Structural Database) and exploits the idea of identifying hotspots using small chemical fragments, which is now widely used to design new drug leads. Prior to this publication, Fragment Hotspot Maps was only publicly available through a web application. To increase the accessibility of this algorithm we present the Hotspots API (application programming interface), a toolkit that offers programmatic access to the core Fragment Hotspot Maps algorithm, thereby facilitating the interpretation and application of the analysis. To demonstrate the package's utility, we present a workflow which automatically derives protein hydrogen-bond constraints for molecular docking with GOLD. The Hotspots API is available from https://github.com/prcurran/hotspots under the MIT license and is dependent upon the commercial CSD Python API.
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http://dx.doi.org/10.1021/acs.jcim.9b00996DOI Listing
April 2020

Fsp-rich and diverse fragments inspired by natural products as a collection to enhance fragment-based drug discovery.

Chem Commun (Camb) 2020 Feb;56(15):2280-2283

Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge, UK.

Herein, we describe the natural product inspired synthesis of 38 complex small molecules based upon 20 unique frameworks suitable for fragment-based screening. Utilising an efficient strategy, two key building block diastereomers were harnessed to generate novel, three-dimensional fragments which each possess numerous synthetically accessible fragment growth positions.
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http://dx.doi.org/10.1039/c9cc09796aDOI Listing
February 2020

Functionalized Double Strain-Promoted Stapled Peptides for Inhibiting the p53-MDM2 Interaction.

ACS Omega 2020 Jan 7;5(2):1157-1169. Epub 2020 Jan 7.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.

The Sondheimer dialkyne reagent has previously been employed in strain-promoted double-click cycloadditions with bis-azide peptides to generate stapled peptide inhibitors of protein-protein interactions. The substituted variants of the Sondheimer dialkyne can be used to generate functionalized stapled peptide inhibitors with improved biological properties; however, this remains a relatively underdeveloped field. Herein, we report the synthesis of new substituted variants of Sondheimer dialkyne and their application in the stapling of p53-based diazido peptides to generate potent stapled peptide-based inhibitors of the oncogenic p53-MDM2 interaction. The functionalized stapled peptide formed from a -fluoro-substituted Sondheimer dialkyne was found to be the most potent inhibitor. Furthermore, through experimental studies and density functional theory calculations, we investigated the impact of the substituent on the strain-promoted double-click reactivity of Sondheimer dialkyne.
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http://dx.doi.org/10.1021/acsomega.9b03459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6977200PMC
January 2020

Sulfatase-cleavable linkers for antibody-drug conjugates.

Chem Sci 2020 Jan 27;11(9):2375-2380. Epub 2020 Jan 27.

Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK

Antibody-drug conjugates (ADCs) are a class of targeted drug delivery agents combining the cell-selectivity of monoclonal antibodies (mAbs) and the cytotoxicity of small molecules. These two components are joined by a covalent linker, whose nature is critical to the efficacy and safety of the ADC. Enzyme-cleavable dipeptidic linkers have emerged as a particularly effective ADC linker type due to their ability to selectively release the payload in the lysosomes of target cells. However, these linkers have a number of drawbacks, including instability in rodent plasma and their inherently high hydrophobicity. Here we show that arylsulfate-containing ADC linkers are cleaved by lysosomal sulfatase enzymes to tracelessly release their payload, while circumventing the instability problems associated with dipeptide-linkers. When incorporated with trastuzumab and the highly potent monomethyl auristatin E (MMAE) payload, the arylsulfate-containing and were more cytotoxic than the non-cleavable against HER2-positive cells, while maintaining selectivity over HER2-negative cells. We propose that the stability, solubility and synthetic tractability of our arylsulfate linkers make them an attractive new motif for cleavable ADC linkers, with clear benefits over the widely used dipeptidic linkers.
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http://dx.doi.org/10.1039/c9sc06410aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157321PMC
January 2020

Development of a Novel Cell-Permeable Protein-Protein Interaction Inhibitor for the Polo-box Domain of Polo-like Kinase 1.

ACS Omega 2020 Jan 24;5(1):822-831. Epub 2019 Dec 24.

Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, University of Cambridge, Hills Road, Cambridge CB2 2XZ, United Kingdom.

Polo-like kinase 1 (PLK1) is a key regulator of mitosis and a recognized drug target for cancer therapy. Inhibiting the polo-box domain of PLK1 offers potential advantages of increased selectivity and subsequently reduced toxicity compared with targeting the kinase domain. However, many if not all existing polo-box domain inhibitors have been shown to be unsuitable for further development. In this paper, we describe a novel compound series, which inhibits the protein-protein interactions of PLK1 via the polo-box domain. We combine high throughput screening with molecular modeling and computer-aided design, synthetic chemistry, and cell biology to address some of the common problems with protein-protein interaction inhibitors, such as solubility and potency. We use molecular modeling to improve the solubility of a hit series with initially poor physicochemical properties, enabling biophysical and biochemical characterization. We isolate and characterize enantiomers to improve potency and demonstrate on-target activity in both cell-free and cell-based assays, entirely consistent with the proposed binding model. The resulting compound series represents a promising starting point for further progression along the drug discovery pipeline and a new tool compound to study kinase-independent PLK functions.
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http://dx.doi.org/10.1021/acsomega.9b03626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6964520PMC
January 2020

Total synthesis and biological evaluation of simplified aplyronine analogues as synthetically tractable anticancer agents.

Chem Commun (Camb) 2020 Feb 10;56(10):1529-1532. Epub 2020 Jan 10.

University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, UK.

The aplyronines are a family of highly cytotoxic marine natural products with potential application in targeted cancer chemotherapy. To address the severe supply issue, function-oriented molecular editing of their macrolactone scaffold led to the design of a series of simplified aplyronine analogues. Enabled by a highly convergent aldol-based route, the total synthesis of four analogues was achieved, with a significant improvement in step economy versus previous compounds, and their cancer cell growth inhibition in the HeLa cell line was determined. The modular strategy presented offers a means for significantly shortening their chemical synthesis to facilitate the continued development of this promising class of anticancer agent.
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http://dx.doi.org/10.1039/c9cc09050aDOI Listing
February 2020

A cryptic hydrophobic pocket in the polo-box domain of the polo-like kinase PLK1 regulates substrate recognition and mitotic chromosome segregation.

Sci Rep 2019 11 4;9(1):15930. Epub 2019 Nov 4.

The Medical Research Council Cancer Unit, University of Cambridge, Hills Road, Cambridge, CB2 0XZ, United Kingdom.

The human polo-like kinase PLK1 coordinates mitotic chromosome segregation by phosphorylating multiple chromatin- and kinetochore-binding proteins. How PLK1 activity is directed to specific substrates via phosphopeptide recognition by its carboxyl-terminal polo-box domain (PBD) is poorly understood. Here, we combine molecular, structural and chemical biology to identify a determinant for PLK1 substrate recognition that is essential for proper chromosome segregation. We show that mutations ablating an evolutionarily conserved, Tyr-lined pocket in human PLK1 PBD trigger cellular anomalies in mitotic progression and timing. Tyr pocket mutations selectively impair PLK1 binding to the kinetochore phosphoprotein substrate PBIP1, but not to the centrosomal substrate NEDD1. Through a structure-guided approach, we develop a small-molecule inhibitor, Polotyrin, which occupies the Tyr pocket. Polotyrin recapitulates the mitotic defects caused by mutations in the Tyr pocket, further evidencing its essential function, and exemplifying a new approach for selective PLK1 inhibition. Thus, our findings support a model wherein substrate discrimination via the Tyr pocket in the human PLK1 PBD regulates mitotic chromosome segregation to preserve genome integrity.
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http://dx.doi.org/10.1038/s41598-019-50702-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828814PMC
November 2019

Cycloaddition Strategies for the Synthesis of Diverse Heterocyclic Spirocycles for Fragment-Based Drug Discovery.

European J Org Chem 2019 Sep 29;2019(31-32):5219-5229. Epub 2019 Jul 29.

Department of Chemistry University of Cambridge Lensfield Road 1EW Cambridge CB21EW.

In recent years the pharmaceutical industry has benefited from the advances made in fragment-based drug discovery (FBDD) with more than 30 fragment-derived drugs currently marketed or progressing through clinical trials. The success of fragment-based drug discovery is entirely dependent upon the composition of the fragment screening libraries used. Heterocycles are prevalent within marketed drugs due to the role they play in providing binding interactions; consequently, heterocyclic fragments are important components of FBDD libraries. Current screening libraries are dominated by flat, sp-rich compounds, primarily owing to their synthetic tractability, despite the superior physicochemical properties displayed by more three-dimensional scaffolds. Herein, we report step-efficient routes to a number of biologically relevant, fragment-like heterocyclic spirocycles. The use of both electron-deficient and electron-rich 2-atom donors was explored in complexity-generating [3+2]-cycloadditions to furnish products in 3 steps from commercially available starting materials. The resulting compounds were primed for further fragment elaboration through the inclusion of synthetic handles from the outset of the syntheses.
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http://dx.doi.org/10.1002/ejoc.201900847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774287PMC
September 2019

Synthesis and Reactivity of a Bis-Strained Alkyne Derived from 1,1'-Biphenyl-2,2',6,6'-tetrol.

ACS Omega 2019 Jan 29;4(1):2160-2167. Epub 2019 Jan 29.

Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, U.K.

The novel "double strained alkyne" has been prepared and evaluated in strain-promoted azide-alkyne cycloaddition reactions with azides. The X-ray crystallographic structure of , which was prepared in one step from 1,1'-biphenyl-2,2',6,6'-tetrol , reveals the strained nature of the alkynes. Dialkyne undergoes cycloaddition reactions with a number of azides, giving mixtures of regiosiomeric products in excellent yields. The monoaddition products were not observed or isolated from the reactions, suggesting that the second cycloaddition proceeds at a faster rate than the first, and this is supported by molecular modeling studies. Dialkyne was successfully employed for "peptide stapling" of a p53-based diazido peptide, whereby two azides are bridged to give a product with a stabilized conformation.
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http://dx.doi.org/10.1021/acsomega.8b03634DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648819PMC
January 2019

Water-soluble, stable and azide-reactive strained dialkynes for biocompatible double strain-promoted click chemistry.

Org Biomol Chem 2019 08;17(34):8014-8018

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

The Sondheimer dialkyne is extensively used in double strain-promoted azide-alkyne cycloadditions. This reagent suffers with poor water-solubility and rapidly decomposes in aqueous solutions. This intrinsically limits its application in biological systems, and no effective solutions are currently available. Herein, we report the development of novel highly water-soluble, stable, and azide-reactive strained dialkyne reagents. To demonstrate their extensive utility, we applied our novel dialkynes to a double strain-promoted macrocyclisation strategy to generate functionalised p53-based stapled peptides for inhibiting the oncogenic p53-MDM2 interaction. These functionalised stapled peptides bind MDM2 with low nanomolar affinity and show p53 activation in a cellular environment. Overall, our highly soluble, stable and azide-reactive dialkynes offer significant advantages over the currently used Sondheimer dialkyne, and could be utilised for numerous biological applications.
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http://dx.doi.org/10.1039/c9ob01745cDOI Listing
August 2019
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