Search

We have developed a practical method to perform the reductive photocleavage of sulfonamides using thioureas as organophotocatalysts. This transformation, which tolerates a variety of substrates, occurs under mild reaction conditions in the presence of tetrabutylammonium borohydride as a reducing agent. Experimental and theoretical mechanistic investigations complete the study, shedding light on the nature of the active species involved in the photocatalytic process.

In recent years there has been rising interest in the field of protein–protein conjugation, especially related to bispecific antibodies (bsAbs) and their therapeutic applications. These constructs contain two paratopes capable of binding two distinct epitopes on target molecules and are thus able to perform complex biological functions (mechanisms of action) not available to monospecific mAbs. Traditionally these bsAbs have been constructed through protein engineering, but recently chemical methods for their construction have started to (re-)emerge. While these have been shown to offer increased modularity, speed and for some methods, even the inherent capacity for further functionalization (e.g., with small molecule cargo), most of these approaches lacked the ability to include a fragment crystallizable (Fc) modality. The Fc component of IgG antibodies offers effector function and increased half-life. Here we report a first-in-class disulfide re-bridging and click-chemistry-based method for the generation of Fc-containing, IgG-like mono- and bispecific antibodies. These are in the FcZ (FabX)-FabY format, i.e., two distinct Fabs and an Fc, potentially all from different antibodies, attached in a homogeneous and covalent manner. We have dubbed these molecules synthetic antibodies (SynAbs). We have constructed a bispecific T cell-engager (BiTE) SynAb, FcCD20-(FabHER2)-FabCD3, and have confirmed that it exhibits the expected biological functions, including the ability to kill HER2+ target cells in a co-culture assay with T cells.

Diseases are multifactorial, with redundancies and synergies between various pathways. However, most of the antibody-based therapeutics on the market interact with only one target, thus limiting their efficacy. The targeting of multiple epitopes could improve the therapeutic index of treatment and counteract mechanisms of resistance. To this effect, a new class of therapeutics has emerged: bispecific antibodies. Bispecific formation using chemical methods is rare and low-yielding and/or requires a large excess of one of the two proteins to avoid homodimerization and heterogeneity. In order for chemically prepared bispecifics to deliver their full potential, high-yielding, modular, and reliable cross-linking technologies are required. Herein, we describe a novel approach not only for the rapid and high-yielding chemical generation of bispecific antibodies from native antibody fragments, but also for the site-specific dual functionalization of the resulting bioconjugates. Based on orthogonal clickable functional groups, this strategy enables the assembly of functionalized bispecifics with controlled loading in a modular and convergent manner.

Significant advancements in C-N bond formation via C-H bond functionalisation have made it a staple in the production of nitrogen-containing compounds in both industry and academia. However, transition metal-free synthesis, particularly in the case of C(sp3)-N formation, has remained a significant challenge to the synthetic community. Herein we report a procedure for α-C(sp3)-H amination of ethereal compounds through use of azodicarboxylates as the nitrogen source and freely-available atmospheric oxygen to access ethereal radical intermediates via aerobic C-H activation. The use of fluorinated alcohols as solvent is observed to greatly increase the efficiency of the reaction and we show experimentally and theoretically the key role of H-bonding between fluorinated alcohols and azodicarboxylates. Calculations of the condensed Fukui functions of a H-bonded fluorinated alcohol-azodicarboxylate complex correlates with a significantly increased susceptibility of azodicarboxylates to undergo reaction with radicals, which informs a number of recent reports in the literature.

Significant advancements in C-N bond formation via C-H bond functionalisation have made it a staple in the production of nitrogen-containing compounds in both industry and academia. However, transition metal-free synthesis, particularly in the case of C(sp3)-N formation, has remained a significant challenge to the synthetic community. Herein we report a procedure for α-C(sp3)-H amination of ethereal compounds through use of azodicarboxylates as the nitrogen source and freely-available atmospheric oxygen to access ethereal radical intermediates via aerobic C-H activation. The use of fluorinated alcohols as solvent is observed to greatly increase the efficiency of the reaction and we show experimentally and theoretically the key role of H-bonding between fluorinated alcohols and azodicarboxylates. Calculations of the condensed Fukui functions of a H-bonded fluorinated alcohol-azodicarboxylate complex correlates with a significantly increased susceptibility of azodicarboxylates to undergo reaction with radicals, which informs a number of recent reports in the literature.

Diseases are multifactorial, with redundancies and synergies between various pathways. However, most of the antibody-based therapeutics on the market interact with only one target, thus limiting their efficacy. The targeting of multiple epitopes could improve the therapeutic index of treatment and counteract mechanisms of resistance. To this effect, a new class of therapeutics has emerged: bispecific antibodies. Bispecific formation using chemical methods is rare and low-yielding and/or requires a large excess of one of the two proteins to avoid homodimerization and heterogeneity. In order for chemically prepared bispecifics to deliver their full potential, high-yielding, modular, and reliable cross-linking technologies are required. Herein, we describe a novel approach not only for the rapid and high-yielding chemical generation of bispecific antibodies from native antibody fragments, but also for the site-specific dual functionalization of the resulting bioconjugates. Based on orthogonal clickable functional groups, this strategy enables the assembly of functionalized bispecifics with controlled loading in a modular and convergent manner.

Bispecific antibodies (BsAbs) are antibodies with two different paratopes. In the past decade, advances in protein engineering have enabled the development of more than 100 formats of BsAbs. With two BsAbs approved for therapeutic use and more than 60 in clinical trials, this research area has shifted from being effervescent to being a mainstream therapeutic development topic. In parallel, recent progress in protein conjugation and cytotoxicity of small molecule drugs has resulted in a boom in monospecific antibody therapeutics development such as antibody-drug conjugates (ADCs). Recent examples have demonstrated how BsAbs approaches can be used to generate ADCs with better efficacy and safety profile. Rather than examining these two different yet similar areas independently, this minireview will explore the potential synergies that can exist between them.

Correction for ‘Use of pyridazinediones as extracellular cleavable linkers through reversible cysteine conjugation’ by Calise Bahou et al., Chem. Commun., 2019, 55, 14829–14832, https://doi.org/10.1039/C9CC08362F.

Exploitation of photosensitizers as payloads for antibody-based anticancer therapeutics offers a novel alternative to the small pool of commonly utilized cytotoxins. However, existing bioconjugation methodologies are incompatible with the requirement of increased antibody loading without compromising antibody function, stability, or homogeneity. Herein, we describe the first application of dendritic multiplier groups to allow the loading of more than 4 porphyrins to a full IgG antibody in a site-specific and highly homogeneous manner. Photophysical evaluation of UV-visible absorbance and singlet oxygen quantum yields highlighted porphyrin-dendron 14 as the best candidate for bioconjugation; with subsequent bioconjugation producing a HER2-targeted therapeutic with average loading ratios of 15.4:1. In vitro evaluation of conjugate 18 demonstrated a nanomolar photocytotoxic effect in a target cell line, which overexpresses HER2, with no observed photocytotoxicity at the same concentration in a control cell line which expresses native HER2 levels, or in the absence of irradiation with visible light.

Herein we report a retro-Michael deconjugation pathway of thiol-pyridazinedione linked protein bioconjugates to provide a novel cleavable linker technology. We demonstrate that the novel pyridazinedione linker does not suffer from off-target modification with blood thiols (e.g., glutathione, human serum albumin (HSA)), which is in sharp contrast to an analogous maleimide linker.

An efficient nano-sized delivery system is presented here allowing the immobilized, picolinium-tethered organic ligand to be released by X-ray irradiation. A marked difference was observed in the fragmentation efficiency by using conventional Cs-137

Diseases are multifactorial, with redundancies and synergies between various pathways. However, most of the antibody-based therapeutics in clinical trials and on the market interact with only one target thus limiting their efficacy. The targeting of multiple epitopes could improve the therapeutic index of treatment and counteract mechanisms of resistance. To this effect, a new class of therapeutics emerged: bispecific antibodies.Bispecific formation using chemical methods is rare and low yielding and/or requires a large excess of one of the two proteins to avoid homodimerisation. In order for chemically prepared bispecifics to deliver their full potential, high-yielding, modular and reliable cross-linking technologies are required. Herein, we describe a novel approach not only for the rapid and high-yielding chemical generation of bispecific antibodies from native antibody fragments, but also for the site-specific dual functionalisation of the resulting bioconjugates. Based on orthogonal clickable functional groups, this strategy enables the assembly of functionalised bispecifics with controlled loading in a modular and convergent manner.

Modification of immunoglobulin G (IgG) 1 proteins in cancer treatment is a rapidly growing field of research. Antibody-drug conjugates (ADCs) exploit the targeted nature of this immunotherapy by conjugating highly potent drugs to antibodies, allowing for effective transport of cargo(s) to cancerous cells. Of the many bioconjugation strategies now available for the formation of highly homogeneous ADCs, disulfide modification is considered an effective, low-cost, and widely accepted method for modifying IgG1s for improved clinical benefit. However, little is known about how disulfide modification impacts clinically relevant fragment crystallizable (Fc) region interactions. Although often overlooked as a secondary ADC function, Fc interactions could prove key in the rational design of cancer cell-targeting ADCs through consideration of potent mechanisms such as antibody-dependent cellular cytotoxicity (ADCC). This work explores different IgG1 disulfide modification techniques and the effect they have on quantifiable secondary IgG1 Fc interactions (e.g., CD16a and FcRn). The solvent accessible disulfide residues of trastuzumab, a clinically relevant IgG1, were modified to provide a range of bioconjugates with differing amounts of interchain covalent linkages. It was found that by natively rebridging the IgG1 model, all tested Fc functionalities were not significantly affected. Additionally, in non Fc-specific biophysical experiments (e.g., thermal stability/aggregation), the natively rebridged species provided an exceptional profile, showing no significant change from the tested native antibody. Conjugates with significant disruption of the covalent connectivity of IgG1 chains resulted in a suboptimal Fc profile (CD16a kinetics or ADCC activity), in addition to substandard non Fc-specific attributes (thermal stability). These results advocate native disulfide rebridging as an excellent synthetic strategy for forming homogeneous IgG1 bioconjugates, with no reported negative impact on biophysical profile relative to the native antibody.

Herein we report the use of pyridazinediones to functionalise the native solvent accessible interstrand disulfide bonds in trastuzumab with monomethyl auristatin E (MMAE). This method of conjugation delivers serum stable antibody–drug conjugates (ADCs) with a controlled drug loading of 4. Moreover, we demonstrate that the MMAE-bearing ADCs are potent, selective and efficacious against cancer cell lines in both in vitro and in vivo models.

Recent advances in nanomedicine have shown that dramatic improvements in nanoparticle therapeutics and diagnostics can be achieved through the use of disease specific targeting ligands., Recent advances in nanomedicine have shown that dramatic improvements in nanoparticle therapeutics and diagnostics can be achieved through the use of disease specific targeting ligands. Although immunoglobulins have successfully been employed for the generation of actively targeted nanoparticles, their use is often hampered by the suboptimal characteristics of the resulting complexes. Emerging data suggest that a switch in focus from full antibodies to antibody derived fragments could help to alleviate these problems and expand the potential of antibody–nanoparticle conjugates as biomedical tools. This review aims to highlight how antibody derived fragments have been utilised to overcome both fundamental and practical issues encountered during the design and application of antibody–targeted nanoparticles.

Antibody-drug conjugates (ADCs) comprise antibodies covalently attached to highly potent drugs using a variety of conjugation technologies. As therapeutics, they combine the exquisite specificity of antibodies, enabling discrimination between healthy and diseased tissue, with the cell-killing ability of cytotoxic drugs. This powerful and exciting class of targeted therapy has shown considerable promise in the treatment of various cancers with two US Food and Drug Administration approved ADCs currently on the market (Adcetris and Kadcyla) and approximately 40 currently undergoing clinical evaluation. However, most of these ADCs exist as heterogeneous mixtures, which can result in a narrow therapeutic window and have major pharmacokinetic implications. In order for ADCs to deliver their full potential, sophisticated site-specific conjugation technologies to connect the drug to the antibody are vital. This Perspective discusses the strategies currently used for the site-specific construction of ADCs and appraises their merits and disadvantages.

Herein we present an efficient method for the synthesis of esters from aromatic aldehydes via readily accessible acyl hydrazides. The developed reaction protocol is shown to be tolerant of a range of aromatic aldehydes, bearing various functionalities, as well as being amenable to the synthesis of thioesters and amides.

This article gives an overview of the use of 3,6-pyridazinediones in organic synthesis and chemical biology with an emphasis on recent developments. The properties of pyridazinediones, how they are constructed and how they have been applied in various fields of organic synthesis, medicinal chemistry and chemical biology will be highlighted.

With the advent of novel bioorthogonal reactions and "click" chemistry, an increasing number of strategies for the single labelling of proteins and oligonucleotides have emerged. Whilst several methods exist for the site-selective introduction of a single chemical moiety, site-selective and bioorthogonal dual modification of biomolecules remains a challenge. The introduction of multiple modules enables a plethora of permutations and combinations and can generate a variety of bioconjuguates with many potential applications. From de novo approaches on oligomers to the post-translational functionalisation of proteins, this review will highlight the main strategies to dually modify biomolecules.

We herein report the synthesis and analysis of a novel aza-BODIPY-antibody conjugate, formed by controlled and regioselective bioconjugation methodology. Employing the clinically relevant antibody, which targets HER2 positive cancers, represents an excellent example of an antibody targeting strategy for this class of near-IR emitting fluorophore. The NIR fluorescence and binding properties were validated through in vitro studies using live cell confocal imaging.

A novel reagent/strategy enables the controlled assembly of antibody conjugates with a loading of two modules without antibody engineering., The generation of antibody conjugates with a loading of two modules is desirable for a host of reasons. Whilst certain antibody engineering approaches have been useful in the preparation of such constructs, a reliable method based on a native antibody scaffold without the use of enzymes or harsh oxidative conditions has hitherto not been achieved. The use of native antibodies has several advantages in terms of cost, practicality, accessibility, time and overall efficiency. Herein we present a novel, reliable method of furnishing antibody conjugates with a loading of two modules starting from a native antibody scaffold.

With the advent of novel bioorthogonal reactions and “click” chemistry, an increasing number of strategies for the single labelling of proteins and oligonucleotides have emerged. Whilst several methods exist for the site-selective introduction of a single chemical moiety, site-selective and bioorthogonal dual modification of biomolecules remains a challenge. The introduction of multiple modules enables a plethora of permutations and combinations and can generate a variety of bioconjuguates with many potential applications. From de novo approaches on oligomers to the post-translational functionalisation of proteins, this review will highlight the main strategies to dually modify biomolecules.

Herein we present an efficient method for the synthesis of esters from aromatic aldehydes via readily accessible acyl hydrazides. The developed reaction protocol is shown to be tolerant of a range of aromatic aldehydes, bearing various functionalities, as well as being amenable to the synthesis of thioesters and amides.

This article gives an overview of the use of 3,6-pyridazinediones in organic synthesis and chemical biology with an emphasis on recent developments. The properties of pyridazinediones, how they are...

Herein we present a significant step towards next-generation antibody-based photodynamic therapeutics. Site-selective modification of a clinically relevant monoclonal antibody, with a serum-stable linker bearing a strained alkyne, allows for the controlled Cu-free "click" assembly of an in vitro active antibody-based PDT agent using a water soluble azide porpyhrin.

Thiol-stable albumin biologics are enabled by controlled, quantitative hydrolysis of maleimide–albumin conjugates, i.e. with no retro-Michael., Herein we report the use of bromomaleimides for the construction of stable albumin conjugates via conjugation to its native, single accessible, cysteine followed by hydrolysis. Advantages over the classical maleimide approach are highlighted in terms of quantitative hydrolysis and absence of undesirable retro-Michael deconjugation.