Development and evaluation of β-galactosidase-sensitive antibody-drug conjugates

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Antibody-Drug Conjugates: A promising breakthrough in cancer therapy

Antibody-drug conjugates (ADCs) provide effective cancer treatment through the selective delivery of cytotoxic payloads to the cancer cells. They offer unparalleled precision and specificity in directing drugs to cancer cells while minimizing off-target effects. Despite several advantages, there is a requirement for innovations in the molecular design of ADC owing to drug resistance, cancer heterogeneity along the adverse effects of treatment. The review critically analyses ADC function mechanisms, unraveling the intricate interplay between antibodies, linkers, and payloads in facilitating targeted drug delivery to cancer cells. The article also highlights notable advancements in antibody engineering, which aid in creating highly selective and potent ADCs. Additionally, the review details significant progress in clinical ADC development with an in-depth examination of pivotal trials and approved formulations. Antibody Drug Conjugates (ADCs) are a ground-breaking approach to targeted drug delivery, especially in cancer treatment. They offer unparalleled precision and specificity in directing drugs to cancer cells while minimizing off-target effects. This review provides a comprehensive examination of the current state of ADC development, covering their design, mechanisms of action, and clinical applications. The article emphasizes the need for greater precision in drug delivery and explains why ADCs are necessary.

Smart Galactosidase-Responsive Antimicrobial Dendron: Towards More Biocompatible Membrane-Disruptive Agents

Antimicrobial resistance is a global healthcare challenge that urgently needs the development of new therapeutic agents. Antimicrobial peptides and mimics thereof are promising candidates but mostly suffer from inherent toxicity issues due to the non-selective binding of cationic groups with mammalian cells. To overcome this toxicity issue, this work herein reports the synthesis of a smart antimicrobial dendron with masked cationic groups (Gal-Dendron) that could be uncaged in the presence of β-galactosidase enzyme to form the activated Enz-Dendron and confer antimicrobial activity. Enz-Dendron show bacteriostatic activity toward Gram-negative (P. aeruginosa and E. coli) and Gram-positive (S. aureus) bacteria with minimum inhibitory concentration values of 96 µm and exerted its antimicrobial mechanism via a membrane disruption pathway, as indicated by inner and outer membrane permeabilization assays. Crucially, toxicity studies confirmed that the masked prodrug Gal-Dendron exhibited low hemolysis and is at least 2.4 times less toxic than the uncaged cationic Enz-Dendron, thus demonstrating the advantage of masking the cationic groups with responsive immolative linkers to overcome toxicity and selectivity issues. Overall, this study highlights the potential of designing new membrane-disruptive antimicrobial agents that are more biocompatible via the amine uncaging strategy.

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Generation and Characterization of Iduronidase-Cleavable ADCs

A crucial design feature for the therapeutic success of antibody-drug conjugates (ADCs) is the linker that connects the antibody with the drug. Linkers must be stable in circulation and efficiently release the drug inside the target cell, thereby having a fundamental impact on ADC pharmacokinetics and efficacy. The variety of enzymatically cleavable linkers applied in ADCs is limited, and some are believed to be associated with unwanted side effects due to the expression of cleavage-mediating enzymes in nonmalignant cells. Based on a bioinformatic screen of lysosomal enzymes, we identified α-l-iduronidase (IduA) as an interesting candidate for ADC linker cleavage because of its low expression in normal tissues and its overexpression in several tumor types. In the present study, we report a novel IduA-cleavable ADC linker using exatecan and duocarmycin as payloads. We showed the functionality of our linker system in cleavage assays using recombinant IduA or cell lysates and compared it to established ADC linkers. Subsequently, we coupled iduronide-exatecan via interchain cysteines or iduronide-duocarmycin via microbial transglutaminase (mTG) to an anti-CEACAM5 (aCEA5) antibody. The generated iduronide-exatecan ADC showed high serum stability and similar target-dependent tumor cell killing in the subnanomolar range but reduced toxicity on nonmalignant cells compared to an analogous cathepsin B-activatable valine-citrulline-exatecan ADC. Finally, in vivo antitumor activity could be demonstrated for an IduA-cleavable duocarmycin ADC. The presented results emphasize the potential of iduronide linkers for ADC development and represent a tool for further balancing out tumor selectivity and safety.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Design and application of prodrug fluorescent probes for the detection of ovarian cancer cells and release of anticancer drug

Ovarian cancer is a gynecologic malignancy with high mortality. The main reason is that it is detected at an advanced stage due to a lack of early diagnosis and treatment. Therefore, it is of great interest to develop a chemical tool that can visualize ovarian cancer cells in real-time and eliminate them. Unfortunately, probes that can simultaneously monitor both modes of action for the diagnosis and treatment of ovarian cancer have not been developed. Here, we designed a novel prodrug fluorescent probe (YW-OAc) that not only visually tracks cancer cells but also enables the on-demand delivery of chemotherapeutic agents. By β-Gal-mediated glycosidic bond hydrolysis, the fluorescent signal changed from blue to green (signal 1), enabling visual tracking of ovarian cancer cells. Subsequently, the identified cancer cells were subjected to precise light irradiation to induce anticancer drug release accompanied by a fluorescence transition from green to blue (signal 2), enabling real-time information on drug release. Thus, the prodrug fluorescent probe YW-OAc provides comprehensive two-step monitoring during cancer cell recognition and clearance. Notably, YW-OAc exhibited high affinity (K_m = 3.74 μM), high selectivity, and low detection limit for β-Gal (0.0035 U/mL). We also demonstrated that YW-OAc can visually trace endogenous β-Gal in different cells and exhibit high phototoxicity in ovarian cancer cells. We hope that the prodrug fluorescent probe YW-OAc, can be used as an effective tool for biomedical diagnosis and treatment.

The Dawn of a New Era: Targeting the "Undruggables" with Antibody-Based Therapeutics

The high selectivity and affinity of antibodies toward their antigens have made them a highly valuable tool in disease therapy, diagnosis, and basic research. A plethora of chemical and genetic approaches have been devised to make antibodies accessible to more "undruggable" targets and equipped with new functions of illustrating or regulating biological processes more precisely. In this Review, in addition to introducing how naked antibodies and various antibody conjugates (such as antibody-drug conjugates, antibody-oligonucleotide conjugates, antibody-enzyme conjugates, etc.) work in therapeutic applications, special attention has been paid to how chemistry tools have helped to optimize the therapeutic outcome (i.e., with enhanced efficacy and reduced side effects) or facilitate the multifunctionalization of antibodies, with a focus on emerging fields such as targeted protein degradation, real-time live-cell imaging, catalytic labeling or decaging with spatiotemporal control as well as the engagement of antibodies inside cells. With advances in modern chemistry and biotechnology, well-designed antibodies and their derivatives via size miniaturization or multifunctionalization together with efficient delivery systems have emerged, which have gradually improved our understanding of important biological processes and paved the way to pursue novel targets for potential treatments of various diseases.

Induced-volatolomics for the design of tumour activated therapy

The discovery of tumour-associated markers is of major interest for the development of selective cancer chemotherapy. Within this framework, we introduced the concept of induced-volatolomics enabling to monitor simultaneously the dysregulation of several tumour-associated enzymes in living mice or biopsies. This approach relies on the use of a cocktail of volatile organic compound (VOC)-based probes that are activated enzymatically for releasing the corresponding VOCs. Exogenous VOCs can then be detected in the breath of mice or in the headspace above solid biopsies as specific tracers of enzyme activities. Our induced-volatolomics modality highlighted that the up-regulation of N-acetylglucosaminidase was a hallmark of several solid tumours. Having identified this glycosidase as a potential target for cancer therapy, we designed an enzyme-responsive albumin-binding prodrug of the potent monomethyl auristatin E programmed for the selective release of the drug in the tumour microenvironment. This tumour activated therapy produced a remarkable therapeutic efficacy on orthotopic triple-negative mammary xenografts in mice, leading to the disappearance of tumours in 66% of treated animals. Thus, this study shows the potential of induced-volatolomics for the exploration of biological processes as well as the discovery of novel therapeutic strategies.

Drug conjugate-based anticancer therapy - Current status and perspectives

Drug conjugates are conjugates comprising a tumor-homing carrier tethered to a cytotoxic agent via a linker that are designed to deliver an ultra-toxic payload directly to the target cancer cells. This strategy has been successfully used to increase the therapeutic efficacy of cytotoxic agents and reduce their toxic side effects. Drug conjugates are being developed worldwide, with the potential to revolutionize current cancer treatment strategies. Antibody-drug conjugates (ADCs) have developed rapidly, and 14 of them have received market approval since the first approval event by the Food and Drug Administration in 2000. However, there are some limitations in the use of antibodies as carriers. Other classes of drug conjugates are emerging, such as targeted drugs conjugated with peptides (peptide-drug conjugates, PDCs) and polymers (polymer-drug conjugates, PolyDCs) with the remaining constructs similar to those of ADCs. These novel drug conjugates are gaining attention because they overcome the limitations of ADCs. This review summarizes the current state and advancements in knowledge regarding the design, constructs, and clinical efficacy of different drug conjugates.

Lysosomal-mediated drug release and activation for cancer therapy and immunotherapy

The development of carrier systems that are able to transport and release therapeutics to target cells is an emergent strategy to treat cancer; however, they following endocytosis are usually trapped in the endo/lysosomal compartments. The efficacy of drug conjugates and nanotherapeutics relies critically on their intracellular drug release ability, for which advanced systems responding to the unique lysosomal environment such as acidic pH and abundant enzymes (e.g. cathepsin B, sulfatase and β-glucuronidase) or equipped with photochemical internalization property have been energetically pursued. In this review, we highlight the recent designs of smart systems that promote efficient lysosomal release and/or escape of anticancer agents including chemotherapeutics (e.g. doxorubicin, platinum, chloroquine and hydrochloroquine) and biotherapeutics (e.g. proteins, siRNA, miRNA, mRNA and pDNA) to cancer cells or immunotherapeutic agents (e.g. antigens, mRNA and immunoadjuvants) to antigen-presenting cells (APCs), thereby boosting cancer therapy and immunotherapy. Lysosomal-mediated drug release presents an appealing approach to develop innovative cancer therapeutics and immunotherapeutics.

Linkers: An Assurance for Controlled Delivery of Antibody-Drug Conjugate

As one of the major therapeutic options for cancer treatment, chemotherapy has limited selectivity against cancer cells. Consequently, this therapeutic strategy offers a small therapeutic window with potentially high toxicity and thus limited efficacy of doses that can be tolerated by patients. Antibody-drug conjugates (ADCs) are an emerging class of anti-cancer therapeutic drugs that can deliver highly cytotoxic molecules directly to cancer cells. To date, twelve ADCs have received market approval, with several others in clinical stages. ADCs have become a powerful class of therapeutic agents in oncology and hematology. ADCs consist of recombinant monoclonal antibodies that are covalently bound to cytotoxic chemicals via synthetic linkers. The linker has a key role in ADC outcomes because its characteristics substantially impact the therapeutic index efficacy and pharmacokinetics of these drugs. Stable linkers and ADCs can maintain antibody concentration in blood circulation, and they do not release the cytotoxic drug before it reaches its target, thus resulting in minimum off-target effects. The linkers used in ADC development can be classified as cleavable and non-cleavable. The former, in turn, can be grouped into three types: hydrazone, disulfide, or peptide linkers. In this review, we highlight the various linkers used in ADC development and their design strategy, release mechanisms, and future perspectives.

Stepping forward in antibody-drug conjugate development

Antibody-drug conjugates (ADCs) are cancer therapeutic agents comprised of an antibody, a linker and a small-molecule payload. ADCs use the specificity of the antibody to target the toxic payload to tumor cells. After intravenous administration, ADCs enter circulation, distribute to tumor tissues and bind to the tumor surface antigen. The antigen then undergoes endocytosis to internalize the ADC into tumor cells, where it is transported to lysosomes to release the payload. The released toxic payloads can induce apoptosis through DNA damage or microtubule inhibition and can kill surrounding cancer cells through the bystander effect. The first ADC drug was approved by the United States Food and Drug Administration (FDA) in 2000, but the following decade saw no new approved ADC drugs. From 2011 to 2018, four ADC drugs were approved, while in 2019 and 2020 five more ADCs entered the market. This demonstrates an increasing trend for the clinical development of ADCs. This review summarizes the recent clinical research, with a specific focus on how the in vivo processing of ADCs influences their design. We aim to provide comprehensive information about current ADCs to facilitate future development.

Glycosidase activated prodrugs for targeted cancer therapy

In this review glycosidase activated prodrugs that target cancer cells are discussed.

Antibody-drug conjugates: Recent advances in linker chemistry

Antibody–drug conjugates (ADCs) are gradually revolutionizing clinical cancer therapy. The antibody–drug conjugate linker molecule determines both the efficacy and the adverse effects, and so has a major influence on the fate of ADCs. An ideal linker should be stable in the circulatory system and release the cytotoxic payload specifically in the tumor. However, existing linkers often release payloads nonspecifically and inevitably lead to off-target toxicity. This defect is becoming an increasingly important factor that restricts the development of ADCs. The pursuit of ADCs with optimal therapeutic windows has resulted in remarkable progress in the discovery and development of novel linkers. The present review summarizes the advance of the chemical trigger, linker‒antibody attachment and linker‒payload attachment over the last 5 years, and describes the ADMET properties of ADCs. This work also helps clarify future developmental directions for the linkers.

Antibody-Drug Conjugates: Functional Principles and Applications in Oncology and Beyond

In the era of precision medicine, antibody-based therapeutics are rapidly enriched with emerging advances and new proof-of-concept formats. In this context, antibody-drug conjugates (ADCs) have evolved to merge the high selectivity and specificity of monoclonal antibodies (mAbs) with the cytotoxic potency of attached payloads. So far, ten ADCs have been approved by FDA for oncological indications and many others are currently being tested in clinical and preclinical level. This paper summarizes the essential components of ADCs, from their functional principles and structure up to their limitations and resistance mechanisms, focusing on all latest bioengineering breakthroughs such as bispecific mAbs, dual-drug platforms as well as novel linkers and conjugation chemistries. In continuation of our recent review on anticancer implication of ADC's technology, further insights regarding their potential usage outside of the oncological spectrum are also presented. Better understanding of immunoconjugates could maximize their efficacy and optimize their safety, extending their use in everyday clinical practice.

Advances and Limitations of Antibody Drug Conjugates for Cancer

The popularity of antibody drug conjugates (ADCs) has increased in recent years, mainly due to their unrivalled efficacy and specificity over chemotherapy agents. The success of the ADC is partly based on the stability and successful cleavage of selective linkers for the delivery of the payload. The current research focuses on overcoming intrinsic shortcomings that impact the successful development of ADCs. This review summarizes marketed and recently approved ADCs, compares the features of various linker designs and payloads commonly used for ADC conjugation, and outlines cancer specific ADCs that are currently in late-stage clinical trials for the treatment of cancer. In addition, it addresses the issues surrounding drug resistance and strategies to overcome resistance, the impact of a narrow therapeutic index on treatment outcomes, the impact of drug-antibody ratio (DAR) and hydrophobicity on ADC clearance and protein aggregation.

Enzyme-responsive smart nanocarriers for targeted chemotherapy: an overview

Nanocarriers play pivotal roles in the field of biomedical applications, particularly in anticancer therapy. One of the prominent strategies for the transport of anticancer drugs with site-specific release and improved therapeutic efficacy is the use of an enzyme-responsive drug delivery system. There is an emerging class of cancer therapeutics engineered to control the release of a drug via enzymatic degradation. Enzymes, being an essential component of bio-nanotechnology toolbox, hold exceptional biorecognition abilities as well as outstanding catalytic properties. Often, abnormal enzyme expression observed in cancer offers many opportunities in designing nanocarriers modified with enzyme-labile linkage. Through altered physical or chemical characteristics of these nanocarriers or cleavage of the drug in response to the bio-action of enzyme, an on-demand drug release can be obtained. In this review, several classes of enzymes performing critical roles in cancer such as hydrolases, lipases, and oxidoreductases are summarized. Insights on various approaches that interfere with the mechanism of these enzymes have also been included. Finally, various smart nanocarriers such as mesoporous silica nanoparticles, gold nanoparticles, carbon-nanotubes, micelles, liposomes, and dendrimers serving as excellent platforms for enzyme-responsive formulations have been discussed.

The Chemistry Behind ADCs

Combining the selective targeting of tumor cells through antigen-directed recognition and potent cell-killing by cytotoxic payloads, antibody-drug conjugates (ADCs) have emerged in recent years as an efficient therapeutic approach for the treatment of various cancers. Besides a number of approved drugs already on the market, there is a formidable follow-up of ADC candidates in clinical development. While selection of the appropriate antibody (A) and drug payload (D) is dictated by the pharmacology of the targeted disease, one has a broader choice of the conjugating linker (C). In the present paper, we review the chemistry of ADCs with a particular emphasis on the medicinal chemistry perspective, focusing on the chemical methods that enable the efficient assembly of the ADC from its three components and the controlled release of the drug payload.

A dual-enzyme cleavable linker for antibody-drug conjugates

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.

Site-selective modification strategies in antibody-drug conjugates

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.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Recent advances in construction of small molecule-based fluorophore-drug conjugates

As a powerful tool to advance drug discovery, molecular imaging may provide new insights into the process of drug effect and therapy at cellular and molecular levels. When compared with other detection methods, fluorescence-based strategies are highly attractive and can be used to illuminate pathways of drugs' transport, with multi-color capacity, high specificity and good sensitivity. The conjugates of fluorescent molecules and therapeutic agents create exciting avenues for real-time monitoring of drug delivery and distribution, both in vitro and in vivo. In this short review, we discuss recent developments of small molecule-based fluorophore-drug conjugates, including non-cleavable and cleavable ones, that are capable of visualizing drug delivery.

Antibody-Drug Conjugates: The New Frontier of Chemotherapy

In recent years, antibody-drug conjugates (ADCs) have become promising antitumor agents to be used as one of the tools in personalized cancer medicine. ADCs are comprised of a drug with cytotoxic activity cross-linked to a monoclonal antibody, targeting antigens expressed at higher levels on tumor cells than on normal cells. By providing a selective targeting mechanism for cytotoxic drugs, ADCs improve the therapeutic index in clinical practice. In this review, the chemistry of ADC linker conjugation together with strategies adopted to improve antibody tolerability (by reducing antigenicity) are examined, with particular attention to ADCs approved by the regulatory agencies (the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA)) for treating cancer patients. Recent developments in engineering Immunoglobulin (Ig) genes and antibody humanization have greatly reduced some of the problems of the first generation of ADCs, beset by problems, such as random coupling of the payload and immunogenicity of the antibody. ADC development and clinical use is a fast, evolving area, and will likely prove an important modality for the treatment of cancer in the near future.

Bispecific Antibodies and Antibody-Drug Conjugates for Cancer Therapy: Technological Considerations

The ability of monoclonal antibodies to specifically bind a target antigen and neutralize or stimulate its activity is the basis for the rapid growth and development of the therapeutic antibody field. In recent years, traditional immunoglobulin antibodies have been further engineered for better efficacy and safety, and technological developments in the field enabled the design and production of engineered antibodies capable of mediating therapeutic functions hitherto unattainable by conventional antibody formats. Representative of this newer generation of therapeutic antibody formats are bispecific antibodies and antibody–drug conjugates, each with several approved drugs and dozens more in the clinical development phase. In this review, the technological principles and challenges of bispecific antibodies and antibody–drug conjugates are discussed, with emphasis on clinically validated formats but also including recent developments in the fields, many of which are expected to significantly augment the current therapeutic arsenal against cancer and other diseases with unmet medical needs.

Sulfatase-cleavable linkers for antibody-drug conjugates

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 ADC 2 and ADC 3 were more cytotoxic than the non-cleavable ADC 4 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.

Antibody Conjugates-Recent Advances and Future Innovations

Monoclonal antibodies have evolved from research tools to powerful therapeutics in the past 30 years. Clinical success rates of antibodies have exceeded expectations, resulting in heavy investment in biologics discovery and development in addition to traditional small molecules across the industry. However, protein therapeutics cannot drug targets intracellularly and are limited to soluble and cell-surface antigens. Tremendous strides have been made in antibody discovery, protein engineering, formulation, and delivery devices. These advances continue to push the boundaries of biologics to enable antibody conjugates to take advantage of the target specificity and long half-life from an antibody, while delivering highly potent small molecule drugs. While the "magic bullet" concept produced the first wave of antibody conjugates, these entities were met with limited clinical success. This review summarizes the advances and challenges in the field to date with emphasis on antibody conjugation, linker-payload chemistry, novel payload classes, absorption, distribution, metabolism, and excretion (ADME), and product developability. We discuss lessons learned in the development of oncology antibody conjugates and look towards future innovations enabling other therapeutic indications.

Nanomaterials multifunctional behavior for enlightened cancer therapeutics

Cancer is an outrageous disease with uncontrolled differentiation, growth, and migration to the other parts of the body. It is the second-most common cause of death both in the U.S. and worldwide. Current conventional therapies, though much improved and with better prognosis, have several limitations. Chemotherapeutic agents, for instance, are cytotoxic to both tumor and healthy cells, and the non-specific distribution of drugs at tumor sites limits the dose administered. Nanotechnology, which evolved from the coalescence and union of varied scientific disciplines, is a novel science that has been the focus of much research. This technology is generating more effective cancer therapies to overcome biomedical and biophysical barriers against standard interventions in the body; its unique magnetic, electrical, and structural properties make it a promising tool. This article reviews endogenous- and exogenous-based stimulus-responsive drug delivery systems designed to overcome the limitations of conventional therapies. The article also summarizes the study of nanomaterials, including polymeric, gold, silver, magnetic, and quantum dot nanoparticles. Though an array of drug delivery systems has so far been proposed, there remain many challenges and concerns that should be addressed in order to fill the gaps in the field. Prominence is given to drug delivery systems that employ external- and internal-based stimuli and that are emerging as promising tools for cancer therapeutics in clinical settings.

Enzyme responsive drug delivery systems in cancer treatment

Recent technological approaches in drug delivery have attracted scientist interest for improving therapeutic index of medicines and drug compliance. One of the powerful strategies to control the transportation of drugs is implementation of intelligent stimuli-responsive drug delivery system (DDS). In this regard, tumor tissues with unique characteristics including leaky vasculature and diverse enzyme expression profiles facilitate the development of efficient enzyme-responsive nanoscale delivery systems. Based on the stimuli nature (physical, chemical and biological), these systems can be categorized into three groups according to the nature of trigger initiating the drug release. Enzymes are substantial constituents of the biotechnology toolbox offering promising capabilities and ideal characteristics to accelerate chemical reactions. Nanoparticles which have the ability to trigger their cargo release in the presence of specific enzymes are fabricated implementing fascinating physico-chemical properties of different materials in a nanoscale dimension. In order to reduce the adverse effects of the therapeutic agents, nanocarriers can be utilized and modified with enzyme-labile linkages to provide on-demand enzyme-responsive drug release. In the current review, we give an overview of drug delivery systems which can deliver drugs to the tumor microenvironment and initiate the drug release in response to specific enzymes highly expressed in particular tumor tissues. This strategy offers a versatile platform for intelligent drug release at the site of action.

Stimulus-responsive nanoscale delivery systems triggered by the enzymes in the tumor microenvironment

The tumor microenvironment is the cellular environment that is also described as the "soil" for supporting tumor growth, proliferation, invasion and metastasis, as well as protecting tumor cells from immunological recognition. Notably, tumor cells can grow much faster than other normal organs and invade surrounding tissues more easily, which results in abnormal expression of enzymes in the tumor microenvironment, including matrix metalloproteinases, cathepsins, phospholipases, oxidoreductases, etc. In opposite, due to the high selectivity and catalytic activity, these enzymes can promote nanoparticles to recognize tumor tissues more accurately, and the more accumulation of drugs at primal tumor sites will enhance therapeutic efficacy with lower systemic toxicity. Therefore, one promising antitumor strategy is to design stimulus-responsive nanoscale delivery systems triggered by the enzymes with the support of various nanocarriers, such as liposomes, micelles and inorganic nanoparticles, etc. In this review, numerous facts were cited to summarize and discuss the typical types of enzyme-stimulus responsive nanoscale delivery systems. More importantly, we also focused on their recent advancements in antitumor therapy, and offered the direction for further studies.

Cleavable linkers in antibody–drug conjugates

This tutorial review summarises the advances in the field of cleavable linker technologies for antibody–drug conjugates (ADCs).

Reduction-rebridging strategy for the preparation of ADPN-based antibody-drug conjugates

The reduction-rebridging strategy is a powerful method for the preparation of stable and homogeneous antibody-drug conjugates (ADCs). In this communication, we describe the development of the arylene-dipropiolonitrile (ADPN) functional group for the rebridging of reduced disulphide bonds and its application in the preparation of potent and selective ADCs.