Solid-phase synthesis of duocarmycin analogues and the effect of C-terminal substitution on biological activity

YesThe duocarmycins are potent antitumour agents with potential in the development of antibody drug conjugates (ADCs) as well as being clinical candidates in their own right. In this paper, we describe the synthesis of a duocarmycin monomer (DSA) that is suitably protected for utilisation in solid phase synthesis. The synthesis was performed on a large scale and the resulting racemic protected Fmoc-DSA subunit was separated by supercritical fluid chromatography (SFC) into the single enantiomers. Application to solid phase synthesis methodology gave a series of monomeric and extended duocarmycin analogues with amino acid substituents. The DNA sequence selectivity was similar to previous reports for both the monomeric and extended compounds. The substitution at the C-terminus of the duocarmycin caused a decrease in antiproliferative activity for all of the compounds studied. An extended compound containing an alanine at the C-terminus was converted to the primary amide or to an extended structure containing a terminal tertiary amine but this had no beneficial effects on biological activity.MJS was funded by Novartis and UEA. We thank the EPSRC Mass Spectrometry Service, Swansea. We thank Richard Robinson and Julia Hatto at Novartis for help in the large scale synthesis

The expression and prognostic significance of retinoic acid metabolising enzymes in colorectal cancer

Peer reviewedPublisher PD

Antitumor activity of a pyrrole-imidazole polyamide

Many cancer therapeutics target DNA and exert cytotoxicity through the induction of DNA damage and inhibition of transcription. We report that a DNA minor groove binding hairpin pyrrole-imidazole (Py-Im) polyamide interferes with RNA polymerase II (RNAP2) activity in cell culture. Polyamide treatment activates p53 signaling in LNCaP prostate cancer cells without detectable DNA damage. Genome-wide mapping of RNAP2 binding shows reduction of occupancy, preferentially at transcription start sites, but occupancy at enhancer sites is unchanged. Polyamide treatment results in a time- and dose-dependent depletion of the RNAP2 large subunit RPB1 that is preventable with proteasome inhibition. This polyamide demonstrates antitumor activity in a prostate tumor xenograft model with limited host toxicity

Probing cytochrome P450-mediated activation with a truncated azinomycin analogue

YesA deactivated alkene precursor (IC50=81 mu M) to the azinomycin epoxide natural product can be bioactivated by several cytochromes P450 (CYP) to generate antiproliferative metabolites with increased potency (IC50=1-30 mu M) in CHOwt cells. CYP1A1 and 3A4 were shown to generate exclusively the unnatural and the natural-configured azinomycin epoxide diastereoisomer respectively, while CYP1B1 produced both epoxides in a 3:1 mixture. The antiproliferative activity is linked to DNA damage as demonstrated using the comet assay

New water-soluble carbamate ester derivatives of resveratrol

Low bioavailability severely hinders exploitation of the biomedical potential of resveratrol. Extensive phase-II metabolism and poor water solubility contribute to lowering the concentrations of resveratrol in the bloodstream after oral administration. Prodrugs may provide a solution—protection of the phenolic functions hinders conjugative metabolism and can be exploited to modulate the physicochemical properties of the compound. We report here the synthesis and characterization of carbamate ester derivatives of resveratrol bearing on each nitrogen atom a methyl group and either a methoxy-poly(ethylene glycol)-350 (mPEG-350) or a butyl-glucosyl promoiety conferring high water solubility. Ex vivo absorption studies revealed that the butyl-glucosyl conjugate, unlike the mPEG-350 one, is able to permeate the intestinal wall. In vivo pharmacokinetics confirmed absorption after oral administration and showed that no hydrolysis of the carbamate groups takes place. Thus, sugar groups can be attached to resveratrol to obtain soluble derivatives maintaining to some degree the ability to permeate biomembranes, perhaps by facilitated or active transport

Antibody Conjugation and Formulation

In an era where ultra-high antibody concentrations, high viscosities, low volumes, auto-injectors, and long storage requirements are already complex problems with the current unconjugated monoclonal antibodies on the market the formulation demands for antibody-drug conjugates (ADCs) are significant. Antibodies have historically been administered at relatively low concentrations through intravenous (IV) infusion due to their large size and the inability to formulate for oral delivery. Due to the high demands associated with IV infusion and the development of novel antibody targets and unique antibody conjugates more accessible routes of administration such as intramuscular (IM), and subcutaneous (SC) are being explored. This review will summarize various site-specific and non-site-specific antibody conjugation techniques in the context of antibody-drug conjugates (ADCs) and the demands of formulation for high concentration clinical implementation

Palladium-catalyzed selective α-arylation of ortho -bromoacetophenones

Synthesis of 1-(2-bromophenyl)-2-phenylethanones via an intermolecular Pd-catalyzed α-arylation of 1-(2-bromophenyl)ethanones is presented. The method relies on selective C-H activation (α-arylation) of relatively more reactive external iodo-arenes as coupling partners without affecting the bromo-substituent. Moreover, the scope and generality of the method has been well studied by employing the reaction with iodo-arenes as coupling partners bearing electron-withdrawing, simple, and electron-donating groups on the aromatic ring

Chemical proteomics approaches for identifying the cellular targets of natural products.

Covering: 2010 up to 2016. Deconvoluting the mode of action of natural products and drugs remains one of the biggest challenges in chemistry and biology today. Chemical proteomics is a growing area of chemical biology that seeks to design small molecule probes to understand protein function. In the context of natural products, chemical proteomics can be used to identify the protein binding partners or targets of small molecules in live cells. Here, we highlight recent examples of chemical probes based on natural products and their application for target identification. The review focuses on probes that can be covalently linked to their target proteins (either via intrinsic chemical reactivity or via the introduction of photocrosslinkers), and can be applied "in situ" - in living systems rather than cell lysates. We also focus here on strategies that employ a click reaction, the copper-catalysed azide-alkyne cycloaddition reaction (CuAAC), to allow minimal functionalisation of natural product scaffolds with an alkyne or azide tag. We also discuss 'competitive mode' approaches that screen for natural products that compete with a well-characterised chemical probe for binding to a particular set of protein targets. Fuelled by advances in mass spectrometry instrumentation and bioinformatics, many modern strategies are now embracing quantitative proteomics to help define the true interacting partners of probes, and we highlight the opportunities this rapidly evolving technology provides in chemical proteomics. Finally, some of the limitations and challenges of chemical proteomics approaches are discussed