Antibody-drug conjugates (ADCs) for cancer therapy: Strategies, challenges, and successes

Emerging trends and therapeutic applications of monoclonal antibodies

Monoclonal antibodies (mAbs) are being used to prevent, detect, and treat a broad spectrum of malignancies and infectious and autoimmune diseases. Over the past few years, the market for mAbs has grown exponentially. They have become a significant part of many pharmaceutical product lines, and more than 250 therapeutic mAbs are undergoing clinical trials. Ever since the advent of hybridoma technology, antibody-based therapeutics were realized using murine antibodies which further progressed into humanized and fully human antibodies, reducing the risk of immunogenicity. Some of the benefits of using mAbs over conventional drugs include a drastic reduction in the chances of adverse reactions, interactions between drugs, and targeting specific proteins. While antibodies are very efficient, their higher production costs impede the process of commercialization. However, their cost factor has been improved by developing biosimilar antibodies, which are affordable versions of therapeutic antibodies. Along with biosimilars, innovations in antibody engineering have helped to design bio-better antibodies with improved efficacy than the conventional ones. These novel mAb-based therapeutics are set to revolutionize existing drug therapies targeting a wide spectrum of diseases, thereby meeting several unmet medical needs. In the future, mAbs generated by applying next-generation sequencing (NGS) are expected to become a powerful tool in clinical therapeutics. This article describes the methods of mAb production, pre-clinical and clinical development of mAbs, approved indications targeted by mAbs, and novel developments in the field of mAb research.

Nectin-4-directed antibody-drug conjugates (ADCs): Spotlight on preclinical and clinical evidence

Nectin-4 (Nectin cell adhesion molecule 4), a type I transmembrane cell adhesion protein, was demonstrated to be overexpressed in a variety of tumors, making it an attractive antigen for targeted therapies such as antibody-drug conjugates (ADCs). Of great note, the US Food and Drug Administration (FDA)-approval of the first Nectin-4-directed ADC, enfortumab vedotin (EV), in urothelial cancer (UC) not only introduced Nectin-4 as a clinically validated and reliable target antigen but also confirmed the evolving role of Nectin-4-directed ADCs as novel and promising cancer therapeutics. In addition to EV, there have been or are currently being seven and eleven Nectin-4-directed ADCs, respectively, in various stages of clinical trials and preclinical development, offering a promising future for the treatment of Nectin-4-positive cancer patients. This study reviewed clinical- and preclinical-stage Nectin-4-directed ADCs.

Antibody Drug Conjugates for Cancer Therapy: From Metallodrugs to Nature-Inspired Payloads

This review highlights significant advancements in antibody-drug conjugates (ADCs) equipped with metal-based and nature-inspired payloads, focusing on synthetic strategies for antibody conjugation. Traditional methods such us maleimide and succinimide conjugation and classical condensation reactions are prevalent for metallodrugs and natural compounds. However, emerging non-conventional strategies such as photoconjugation are gaining traction due to their milder conditions and, in an aspect which minimizes side reactions, selective formation of ADC. The review also summarizes the therapeutic and diagnostic properties of these ADCs, highlighting their enhanced selectivity and reduced side effects in cancer treatment compared to non-conjugated payloads. ADCs combine the specificity of monoclonal antibodies with the cytotoxicity of chemotherapy drugs, offering a targeted approach to the elimination of cancer cells while sparing healthy tissues. This targeted mechanism has demonstrated impressive clinical efficacy in various malignancies. Key future advancements include improved linker technology for enhanced stability and controlled release of cytotoxic agents, incorporation of novel, more potent, cytotoxic agents, and the identification of new cancer-specific antigens through genomic and proteomic technologies. ADCs are also expected to play a crucial role in combination therapies with immune checkpoint inhibitors, CAR-T cells, and small molecule inhibitors, leading to more durable and potentially curative outcomes. Ongoing research and clinical trials are expanding their capabilities, paving the way for more effective, safer, and personalized treatments, positioning ADCs as a cornerstone of modern medicine and offering new hope to patients.

Antibody-drug conjugates treatment of small cell lung cancer: advances in clinical research

Small cell lung cancer (SCLC) is an extremely aggressive cancer with a relatively low median survival rate after diagnosis. Treatment options such as chemotherapy or combination immunotherapy have shown clinical benefits, but resistance and relapse can occur. Antibody-drug conjugates (ADCs), as a novel class of biopharmaceutical compounds, have broad application prospects in the treatment of SCLC. ADCs consist of monoclonal antibodies that specifically target cancer cells and are attached to cytotoxic drugs, allowing for targeted killing of cancer cells while sparing healthy tissues. Current clinical studies focus on Delta-like protein 3 (DLL3), CD56, Trophoblast cell surface antigen 2 (Trop-2), B7-H3, and SEZ6. Although toxicities exceeding expectations have been observed with Rova-T, drugs targeting TROP-2 (Sacituzumab Govitecan), B7-H3 (DS-7300), and SEZ6 (ABBV-011) have shown exciting clinical benefits. In this review, we collect the latest clinical evidence to describe the therapeutic efficacy and safety of ADCs in SCLC and discuss prospects and challenges.

Single-Domain Antibodies as Antibody-Drug Conjugates: From Promise to Practice-A Systematic Review

BACKGROUND

Antibody-drug conjugates (ADCs) represent potent cancer therapies that deliver highly toxic drugs to tumor cells precisely, thus allowing for targeted treatment and significantly reducing off-target effects. Despite their effectiveness, ADCs can face limitations due to acquired resistance and potential side effects.

OBJECTIVES

This study focuses on advances in various ADC components to improve both the efficacy and safety of these agents, and includes the analysis of several novel ADC formats. This work assesses whether the unique features of VHHs-such as their small size, enhanced tissue penetration, stability, and cost-effectiveness-make them a viable alternative to conventional antibodies for ADCs and reviews their current status in ADC development.

METHODS

Following PRISMA guidelines, this study focused on VHHs as components of ADCs, examining advancements and prospects from 1 January 2014 to 30 June 2024. Searches were conducted in PubMed, Cochrane Library, ScienceDirect and LILACS using specific terms related to ADCs and single-domain antibodies. Retrieved articles were rigorously evaluated, excluding duplicates and non-qualifying studies. The selected peer-reviewed articles were analyzed for quality and synthesized to highlight advancements, methods, payloads, and future directions in ADC research.

RESULTS

VHHs offer significant advantages for drug conjugation over conventional antibodies due to their smaller size and structure, which enhance tissue penetration and enable access to previously inaccessible epitopes. Their superior stability, solubility, and manufacturability facilitate cost-effective production and expand the range of targetable antigens. Additionally, some VHHs can naturally cross the blood-brain barrier or be easily modified to favor their penetration, making them promising for targeting brain tumors and metastases. Although no VHH-drug conjugates (nADC or nanoADC) are currently in the clinical arena, preclinical studies have explored various conjugation methods and linkers.

CONCLUSIONS

While ADCs are transforming cancer treatment, their unique mechanisms and associated toxicities challenge traditional views on bioavailability and vary with different tumor types. Severe toxicities, often linked to compound instability, off-target effects, and nonspecific blood cell interactions, highlight the need for better understanding. Conversely, the rapid distribution, tumor penetration, and clearance of VHHs could be advantageous, potentially reducing toxicity by minimizing prolonged exposure. These attributes make single-domain antibodies strong candidates for the next generation of ADCs, potentially enhancing both efficacy and safety.

Kinetic models towards an enhanced understanding of diverse ADC conjugation reactions

The conjugation reaction is the central step in the manufacturing process of antibody-drug conjugates (ADCs). This reaction generates a heterogeneous and complex mixture of differently conjugated sub-species depending on the chosen conjugation chemistry. The parametrization of the conjugation reaction through mechanistic kinetic models offers a chance to enhance valuable reaction knowledge and ensure process robustness. This study introduces a versatile modeling framework for the conjugation reaction of cysteine-conjugated ADC modalities-site-specific and interchain disulfide conjugation. Various conjugation kinetics involving different maleimide-functionalized payloads were performed, while controlled gradual payload feeding was employed to decelerate the conjugation, facilitating a more detailed investigation of the reaction mechanism. The kinetic data were analyzed with a reducing reversed phase (RP) chromatography method, that can readily be implemented for the accurate characterization of ADCs with diverse drug-to-antibody ratios, providing the conjugation trajectories of the single chains of the monoclonal antibody (mAb). Possible kinetic models for the conjugation mechanism were then developed and selected based on multiple criteria. When calibrating the established model to kinetics involving different payloads, conjugation rates were determined to be payload-specific. Further conclusions regarding the kinetic comparability across the two modalities could also be derived. One calibrated model was used for an exemplary in silico screening of the initial concentrations offering valuable insights for profound understanding of the conjugation process in ADC development.

Antibody-Drug Conjugates-Evolution and Perspectives

Antineoplastic therapy is one of the main research themes of this century. Modern approaches have been implemented to target and heighten the effect of cytostatic drugs on tumors and diminish their general/unspecific toxicity. In this context, antibody-drug conjugates (ADCs) represent a promising and successful strategy. The aim of this review was to assess different aspects regarding ADCs. They were presented from a chemical and a pharmacological perspective and aspects like structure, conjugation and development particularities alongside effects, clinical trials, safety issues and perspectives and challenges for future use of these drugs were discussed. Representative examples include but are not limited to the following main structural components of ADCs: monoclonal antibodies (trastuzumab, brentuximab), linkers (pH-sensitive, reduction-sensitive, peptide-based, phosphate-based, and others), and payloads (doxorubicin, emtansine, ravtansine, calicheamicin). Regarding pharmacotherapy success, the high effectiveness expectation associated with ADC treatment is supported by the large number of ongoing clinical trials. Major aspects such as development strategies are first discussed, advantages and disadvantages, safety and efficacy, offering a retrospective insight on the subject. The second part of the review is prospective, focusing on various plans to overcome the previously identified difficulties.

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.

HER2-targeting antibody drug conjugate FS-1502 in HER2-expressing metastatic breast cancer: a phase 1a/1b trial

Currently approved HER2-targeting antibody-drug conjugates (ADCs) for HER2-positive breast cancer (BC) are associated with safety concerns. In this multicenter, single-arm, dose-escalation (phase 1a) and dose-expansion (phase 1b) phase 1 trial (NCT03944499), patients with HER2-expressing advanced solid tumors received FS-1502 (an anti-HER2 ADC) with a 3 + 3 design in phase 1a; patients with metastatic HER2-positive BC received FS-1502 at the recommended phase 2 dose (RP2D) in phase 1b. The primary end points were dose-limiting toxicities (DLTs), maximum tolerated dose (MTD) and RP2D for phase 1a and objective response rate (ORR) for phase 1b. A total of 150 patients with HER2-expressing solid tumors (n = 5) and BC (n = 145) were enrolled (female, n = 146, 97.3%). One DLT each was reported at 3.0 and 3.5 mg/kg; the MTD was not reached. The RP2D was 2.3 mg/kg once every 3 weeks. Five (3.3%) patients experienced pneumonitis; four (2.7%) had grade 3 reversible ocular events. Of 67 HER2-positive BC patients receiving the RP2D, the best ORR was 53.7% (95% CI, 41.1-66.0%), including PRs confirmed (confirmed ORR, 37.5%) and pending for confirmation. FS-1502 was well tolerated with limited ocular and pulmonary findings and demonstrated promising antitumor activity in HER2-positive BC patients.

Precision Medicine in Rheumatic Diseases: Unlocking the Potential of Antibody-Drug Conjugates

In the era of precision medicine, antibody-drug conjugates (ADCs) have emerged as a cutting-edge therapeutic strategy. These innovative compounds combine the precision of monoclonal antibodies with the potent cell-killing or immune-modulating abilities of attached drug payloads. This unique strategy not only reduces off-target toxicity but also enhances the therapeutic effectiveness of drugs. Beyond their well established role in oncology, ADCs are now showing promising potential in addressing the unmet needs in the therapeutics of rheumatic diseases. Rheumatic diseases, a diverse group of chronic autoimmune diseases with varying etiologies, clinical presentations, and prognoses, often demand prolonged pharmacological interventions, creating a pressing need for novel, efficient, and low-risk treatment options. ADCs, with their ability to precisely target the immune components, have emerged as a novel therapeutic strategy in this context. This review will provide an overview of the core components and mechanisms behind ADCs, a summary of the latest clinical trials of ADCs for the treatment of rheumatic diseases, and a discussion of the challenges and future prospects faced by the development of next-generation ADCs. SIGNIFICANCE STATEMENT: There is a lack of efficient and low-risk targeted therapeutics for rheumatic diseases. Antibody-drug conjugates, a class of cutting-edge therapeutic drugs, have emerged as a promising targeted therapeutic strategy for rheumatic disease. Although there is limited literature summarizing the progress of antibody-drug conjugates in the field of rheumatic disease, updating the advancements in this area provides novel insights into the development of novel antirheumatic drugs.

Progress in the study of antibody-drug conjugates for the treatment of cervical cancer

Cervical cancer is the second most prevalent malignancy affecting women's health globally, and the number of morbidity and mortality from cervical cancer continues to rise worldwide. The 5-year survival rate of patients with recurrent or metastatic cervical cancer is significantly reduced, and existing treatment modalities have low efficacy and high adverse effects, so there is a strong need for new, effective, and well-tolerated therapies. Antibody-drug conjugates (ADCs) are a new targeted therapeutic modality that can efficiently kill tumor cells. This review aims to summarize the composition, research, and development history and mechanism of action of ADCs, to review the research progress of ADCs in the treatment of cervical cancer, and to summarize and prospect the application of ADCs.

Implementation of antibody-drug conjugates in HER2-positive solid cancers: Recent advances and future directions

In recent decades, there has been a surge in the approval of monoclonal antibodies for treating a wide range of hematological and solid malignancies. These antibodies exhibit exceptional precision in targeting the surface antigens of tumors, heralding a groundbreaking approach to cancer therapy. Nevertheless, monoclonal antibodies alone do not show sufficient lethality against cancerous cells compared to chemotherapy. Consequently, a new class of anti-tumor medications, known as antibody-drug conjugates (ADCs), has been developed to bridge the divide between monoclonal antibodies and cytotoxic drugs, enhancing their therapeutic potential. ADCs are chemically synthesized by binding tumor-targeting monoclonal antibodies with cytotoxic payloads through linkers that are susceptible to cleavage by intracellular proteases. They combined the accurate targeting of monoclonal antibodies with the potent efficacy of cytotoxic chemotherapy drugs while circumventing systemic toxicity and boasting superior lethality over standalone targeted drugs. The human epidermal growth factor receptor (HER) family, which encompasses HER1 (also known as EGFR), HER2, HER3, and HER4, plays a key role in regulating cellular proliferation, survival, differentiation, and migration. HER2 overexpression in various tumors is one of the most frequently targeted antigens for ADC therapy in HER2-positive cancers. HER2-directed ADCs have emerged as highly promising treatment modalities for patients with HER2-positive cancers. This review focuses on three approved anti-HER2 ADCs (T-DM1, DS-8201a, and RC48) and reviews ongoing clinical trials and failed trials based on anti-HER2 ADCs. Finally, we address the notable challenges linked to ADC development and underscore potential future avenues for tackling these hurdles.

A Genetically Encoded Photocaged Cysteine for Facile Site-Specific Introduction of Conjugation-Ready Thiol Residues in Antibodies

Antibody-drug conjugates (ADCs) have emerged as a powerful class of anticancer therapeutics that enable the selective delivery of toxic payloads into target cells. There is increasing appreciation for the importance of synthesizing such ADCs in a defined manner where the payload is attached at specific permissive sites on the antibody with a defined drug to antibody ratio. Additionally, the ability to systematically alter the site of attachment is important to fine-tune the therapeutic properties of the ADC. Engineered cysteine residues have been used to achieve such site-specific programmable attachment of drug molecules onto antibodies. However, engineered cysteine residues on antibodies often get "disulfide-capped" during secretion and require reductive regeneration prior to conjugation. This reductive step also reduces structurally important disulfide bonds in the antibody itself, which must be regenerated through oxidation. This multistep, cumbersome process reduces the efficiency of conjugation and presents logistical challenges. Additionally, certain engineered cysteine sites are resistant to reductive regeneration, limiting their utility and the overall scope of this conjugation strategy. In this work, we utilize a genetically encoded photocaged cysteine residue that can be site-specifically installed into the antibody. This photocaged amino acid can be efficiently decaged using light, revealing a free cysteine residue available for conjugation without disrupting the antibody structure. We show that this ncAA can be incorporated at several positions within full-length recombinant trastuzumab and decaged efficiently. We further used this method to generate a functional ADC site-specifically modified with monomethyl auristatin F (MMAF).

Progress of antibody-drug conjugates (ADCs) targeting c-Met in cancer therapy; insights from clinical and preclinical studies

The cell-surface receptor tyrosine kinase c-mesenchymal-epithelial transition factor (c-Met) is overexpressed in a wide range of solid tumors, making it an appropriate target antigen for the development of anticancer therapeutics. Various antitumor c-Met-targeting therapies (including monoclonal antibodies [mAbs] and tyrosine kinases) have been developed for the treatment of c-Met-overexpressing tumors, most of which have so far failed to enter the clinic because of their efficacy and complications. Antibody-drug conjugates (ADCs), a new emerging class of cancer therapeutic agents that harness the target specificity of mAbs to deliver highly potent small molecules to the tumor with the minimal damage to normal cells, could be an attractive therapeutic approach to circumvent these limitations in patients with c-Met-overexpressing tumors. Of great note, there are currently nine c-Met-targeting ADCs being examined in different phases of clinical studies as well as eight preclinical studies for treating various solid tumors. The purpose of this study is to present a broad overview of clinical- and preclinical-stage c-Met-targeting ADCs.

Impact of the Design of Different Infusion Containers on the Dosing Accuracy of a Therapeutic Drug Product

Residual volumes of infusion solutions vary greatly due to container and dimensional variances. Manufacturers use overfill to compensate, but the exact amounts vary significantly. This variability in overfill - when carrier solutions are used to dilute other parenteral preparations - may lead to variable concentrations and dosing, hence, potential risk for patients. We analyzed the overfill and residual volume of 22 pre-filled infusion containers and evaluated the impact on the (simulated) dosing accuracy of a therapeutic drug product for different handling scenarios. In addition, compendial properties of the diluents (i.e. sub-visible particles, pH, color and opalescence) were assessed. The overfill and residual volume between different containers for the same diluent varied. As container size increased, the relative volume of overfill decreased while the residual volume remained constant. The design and material of the containers (e.g. port systems) defined the residual volume. Different handling scenarios led to differences in dosing accuracy. As a result, no universal approach applicable for all containers can be defined. To ensure the right dose, it is recommended to pre-select the preferred diluent, evaluate fill volumes of carrier solutions, and assess in-use compatibility of the product solution with its diluent in terms of concentration and volume.

A Kinetically Controlled Bioconjugation Method for the Synthesis of Radioimmunoconjugates and the Development of a Domain Mapping MS-Workflow for Its Characterization

Immunoconjugates exploit the high affinity of monoclonal antibodies for a recognized antigen to selectively deliver a cytotoxic payload, such as drugs or radioactive nuclides, at the site of disease. Despite numerous techniques have been recently developed for site-selective bioconjugations of protein structures, reaction of ε-amine group of lysine residues with electrophilic reactants, such as activated esters (NHS), is the main method reported in the literature as it maintains proteins in their native conformation. Since antibodies hold a high number of lysine residues, a heterogeneous mixture of conjugates will be generated, which can result in decreased target affinity. Here, we report an intradomain regioselective bioconjugation between the monoclonal antibody Trastuzumab and the N-hydroxysuccinimide ester of the chelator 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) by a kinetically controlled reaction adding substoichiometric quantities of the activated ester to the mAb working at slightly basic pH. Liquid chromatography-mass spectrometry (LC-MS) analyses were carried out to assess the chelator-antibody ratio (CAR) and the number of chelating moieties linked to the mAb chains. Proteolysis experiments showed four lysine residues mainly involved in bioconjugation (K188 for the light chain and K30, K293, and K417 for the heavy chain), each of which was located in a different domain. Since the displayed intradomain regioselectivity, a domain mapping MS-workflow, based on a selective domain denaturation, was developed to quantify the percentage of chelator linked to each mAb domain. The resulting immunoconjugate mixture showed an average CAR of 0.9. About a third of the heavy chains were found as monoconjugated, whereas conjugation of the chelator in the light chain was negligible. Domain mapping showed the CH3 domain bearing 13% of conjugated DOTA, followed by CH2 and VH respectively bearing 12.5 and 11% of bonded chelator. Bioconjugation was not found in the CH1 domain, whereas for the light chain, only the CL domain was conjugated (6%). Data analysis based on LC-MS quantification of different analytical levels (intact, reduced chains, and domains) provided the immunoconjugate formulation. A mixture of immunoconjugates restricted to 15 species was obtained, and the percentage of each one within the mixture was calculated. In particular, species bearing 1 DOTA with a relative abundance ranging from 4 to 20-fold, in comparison to species bearing 2DOTA, were observed. Pairing of bioconjugation under kinetic control with the developed domain mapping MS-workflow could raise the standard of chemical quality for immunoconjugates obtained with commercially available reactants.

Antibody-drug conjugates in urothelial carcinoma: scientometric analysis and clinical trials analysis

In 2020, bladder cancer, which commonly presents as urothelial carcinoma, became the 10th most common malignancy. For patients with metastatic urothelial carcinoma, the standard first-line treatment remains platinum-based chemotherapy, with immunotherapy serving as an alternative in cases of programmed death ligand 1 expression. However, treatment options become limited upon resistance to platinum and programmed death 1 or programmed death ligand 1 agents. Since the FDA's approval of Enfortumab Vedotin and Sacituzumab Govitecan, the therapeutic landscape has expanded, heralding a shift towards antibody-drug conjugates as potential first-line therapies. Our review employed a robust scientometric approach to assess 475 publications on antibody-drug conjugates in urothelial carcinoma, revealing a surge in related studies since 2018, predominantly led by U.S. institutions. Moreover, 89 clinical trials were examined, with 36 in Phase II and 13 in Phase III, exploring antibody-drug conjugates as both monotherapies and in combination with other agents. Promisingly, novel targets like HER-2 and EpCAM exhibit substantial therapeutic potential. These findings affirm the increasing significance of antibody-drug conjugates in urothelial carcinoma treatment, transitioning them from posterior-line to frontline therapies. Future research is poised to focus on new therapeutic targets, combination therapy optimization, treatment personalization, exploration of double antibody-coupled drugs, and strategies to overcome drug resistance.

Antibody-Drug Conjugate Overview: a State-of-the-art Manufacturing Process and Control Strategy

Antibody-drug conjugates (ADCs) comprise an antibody, linker, and drug, which direct their highly potent small molecule drugs to target tumor cells via specific binding between the antibody and surface antigens. The antibody, linker, and drug should be properly designed or selected to achieve the desired efficacy while minimizing off-target toxicity. With a unique and complex structure, there is inherent heterogeneity introduced by product-related variations and the manufacturing process. Here this review primarily covers recent key advances in ADC history, clinical development status, molecule design, manufacturing processes, and quality control. The manufacturing process, especially the conjugation process, should be carefully developed, characterized, validated, and controlled throughout its lifecycle. Quality control is another key element to ensure product quality and patient safety. A patient-centric strategy has been well recognized and adopted by the pharmaceutical industry for therapeutic proteins, and has been successfully implemented for ADCs as well, to ensure that ADC products maintain their quality until the end of their shelf life. Deep product understanding and process knowledge defines attribute testing strategies (ATS). Quality by design (QbD) is a powerful approach for process and product development, and for defining an overall control strategy. Finally, we summarize the current challenges on ADC development and provide some perspectives that may help to give related directions and trigger more cross-functional research to surmount those challenges.

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.

Innovations in Antibody-Drug Conjugate (ADC) in the Treatment of Lymphoma

Chemoimmunotherapy and cellular therapy are the mainstay of the treatment of relapsed/refractory (R/R) lymphomas. Development of resistance and commonly encountered toxicities of these treatments limit their role in achieving desired response rates and durable remissions. The Antibody-Drug Conjugate (ADC) is a novel class of targeted therapy that has demonstrated significant efficacy in treating various cancers, including lymphomas. To date, three ADC agents have been approved for different lymphomas, marking a significant advancement in the field. In this article, we aim to review the concept of ADCs and their application in lymphoma treatment, provide an analysis of currently approved agents, and discuss the ongoing advancements of ADC development.

Internal Fragments Enhance Middle-Down Mass Spectrometry Structural Characterization of Monoclonal Antibodies and Antibody-Drug Conjugates

Monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) are important large biotherapeutics (∼150 kDa) and high structural complexity that require extensive sequence and structure characterization. Middle-down mass spectrometry (MD-MS) is an emerging technique that sequences and maps subunits larger than those released by trypsinolysis. It avoids potentially introducing artifactual modifications that may occur in bottom-up MS while achieving higher sequence coverage compared to top-down MS. However, returning complete sequence information by MD-MS is still challenging. Here, we show that assigning internal fragments in direct infusion MD-MS of a mAb and an ADC substantially improves their structural characterization. For MD-MS of the reduced NIST mAb, including internal fragments recovers nearly 100% of the sequence by accessing the middle sequence region that is inaccessible by terminal fragments. The identification of important glycosylations can also be improved after the inclusion of internal fragments. For the reduced lysine-linked IgG1-DM1 ADC, we show that considering internal fragments increases the DM1 conjugation sites coverage to 80%, comparable to the reported 83% coverage achieved by peptide mapping on the same ADC (Luo et al. Anal. Chem. 2016, 88, 695-702). This study expands our work on the application of internal fragment assignments in top-down MS of mAbs and ADCs and can be extended to other heterogeneous therapeutic molecules such as multispecifics and fusion proteins for more widespread applications.

Antibody-drug conjugates in cancer therapy: innovations, challenges, and future directions

The emergence of antibody-drug conjugates (ADCs) as a potential therapeutic avenue in cancer treatment has garnered significant attention. By combining the selective specificity of monoclonal antibodies with the cytotoxicity of drug molecules, ADCs aim to increase the therapeutic index, selectively targeting cancer cells while minimizing systemic toxicity. Various ADCs have been licensed for clinical usage, with ongoing research paving the way for additional options. However, the manufacture of ADCs faces several challenges. These include identifying suitable target antigens, enhancing antibodies, linkers, and payloads, and managing resistance mechanisms and side effects. This review focuses on the strategies to overcome these hurdles, such as site-specific conjugation techniques, novel antibody formats, and combination therapy. Our focus lies on current advancements in antibody engineering, linker technology, and cytotoxic payloads while addressing the challenges associated with ADC development. Furthermore, we explore the future potential of personalized medicine, leveraging individual patients' molecular profiles, to propel ADC treatments forward. As our understanding of the molecular mechanisms driving cancer progression continues to expand, we anticipate the development of new ADCs that offer more effective and personalized therapeutic options for cancer patients.

Metastasis Models: Thermodynamics and Complexity

The thermodynamic formalism of nonequilibrium systems together with the theory of complex systems and systems biology offer an appropriate theoretical framework to explain the complexity observed at the macroscopic level in physiological phenomena. In turn, they allow the establishment of an appropriate conceptual and operational framework to address the study of phenomena such as the emergence and evolution of cancer.This chapter is organized as follows: In Subheading 1, an integrated vision of these disciplines is offered for the characterization of the emergence and evolution of cancer, seen as a nonlinear dynamic system, temporally and spatially self-organized out of thermodynamic equilibrium. The development of the various mathematical models and different techniques and approaches used in the characterization of cancer metastasis is presented in Subheading 2. Subheading 3 is devoted to the time course of cancer metastasis, with particular emphasis on the epithelial-mesenchymal transition (EMT henceforth) as well as chronotherapeutic treatments. In Subheading 4, models of the spatial evolution of cancer metastasis are presented. Finally, in Subheading 5, some conclusions and remarks are presented.

The origins of nonideality exhibited by monoclonal antibodies and Fab fragments in human serum

The development of therapeutic antibodies remains challenging, time-consuming, and expensive. A key contributing factor is a lack of understanding of how proteins are affected by complex biological environments such as serum and plasma. Nonideality due to attractive or repulsive interactions with cosolutes can alter the stability, aggregation propensity, and binding interactions of proteins in solution. Fluorescence correlation spectroscopy (FCS) can be used to measure apparent second virial coefficient (B2,app ) values for therapeutic and model monoclonal antibodies (mAbs) that capture the nature and strength of interactions with cosolutes directly in undiluted serum and similar complex biological media. Here, we use FCS-derived B2,app measurements to identify the components of human serum responsible for nonideal interactions with mAbs and Fab fragments. Most mAbs exhibit neutral or slightly attractive interactions with intact serum. Generally, mAbs display repulsive interactions with albumin and mildly attractive interactions with IgGs in the context of whole serum. Crucially, however, these attractive interactions are much stronger with pooled IgGs isolated from other serum components, indicating that the effects of serum nonideality can only be understood by studying the intact medium (rather than isolated components). Moreover, Fab fragments universally exhibited more attractive interactions than their parental mAbs, potentially rendering them more susceptible to nonideality-driven perturbations. FCS-based B2,app measurements have the potential to advance our understanding of how physiological environments impact protein-based therapeutics in general. Furthermore, incorporating such assays into preclinical biologics development may help de-risk molecules and make for a faster and more efficient development process.

The Evolving Landscape of Antibody-Drug Conjugates: In Depth Analysis of Recent Research Progress

Antibody-drug conjugates (ADCs) are targeted immunoconjugate constructs that integrate the potency of cytotoxic drugs with the selectivity of monoclonal antibodies, minimizing damage to healthy cells and reducing systemic toxicity. Their design allows for higher doses of the cytotoxic drug to be administered, potentially increasing efficacy. They are currently among the most promising drug classes in oncology, with efforts to expand their application for nononcological indications and in combination therapies. Here we provide a detailed overview of the recent advances in ADC research and consider future directions and challenges in promoting this promising platform to widespread therapeutic use. We examine data from the CAS Content Collection, the largest human-curated collection of published scientific information, and analyze the publication landscape of recent research to reveal the exploration trends in published documents and to provide insights into the scientific advances in the area. We also discuss the evolution of the key concepts in the field, the major technologies, and their development pipelines with company research focuses, disease targets, development stages, and publication and investment trends. A comprehensive concept map has been created based on the documents in the CAS Content Collection. We hope that this report can serve as a useful resource for understanding the current state of knowledge in the field of ADCs and the remaining challenges to fulfill their potential.

Unlocking New Horizons in Small-Cell Lung Cancer Treatment: The Onset of Antibody-Drug Conjugates

Small-cell lung cancer (SCLC) is a highly aggressive disease, accounting for about 15% of all lung cancer cases. Despite initial responses to chemoimmunotherapy, SCLC recurs and becomes resistant to treatment. Recently, antibody-drug conjugates (ADCs) have emerged as a promising therapeutic option for SCLC. ADCs consist of an antibody that specifically targets a tumor antigen linked to a cytotoxic drug. The antibody delivers the drug directly to the cancer cells, minimizing off-target toxicity and improving the therapeutic index. Several ADCs targeting different tumor antigens are currently being evaluated in clinical trials for SCLC. Despite the negative results of rovalpituzumab tesirine (Rova-T), other ADCs targeting different antigens, such as B7-H3, seizure-related homolog 6 (SEZ6), and CEACAM5, have also been investigated in clinical trials, including for SCLC, and their results suggest preliminary activity, either alone or in combination with other therapies. More recently, sacituzumab govitecan, an anti-TROP2 ADC, demonstrated promising activity in lung cancer, including SCLC. Furthermore, an anti-B7-H3 (CD276), ifinatamab deruxtecan (DS7300A), showed a high response rate and durable responses in heavily pretreated SCLC. Overall, ADCs represent an intriguing approach to treating SCLC, particularly in the relapsed or refractory setting. Further studies are needed to determine their efficacy and safety and the best location in the treatment algorithm for SCLC. In this review, we aim to collect and describe the results regarding the past, the present, and the future of ADCs in SCLC.

The nexus of dynamic T cell states and immune checkpoint blockade therapy in the periphery and tumor microenvironment

Immune checkpoint blockade (ICB) therapies, that is, using monoclonal antibodies to reinvigorate tumor-reactive, antigen-specific T cells from the inhibitory effects of CTLA-4, PD-1 and PD-L1 immune checkpoints, have revolutionized the therapeutic landscape of modern oncology. However, only a subset of patients can benefit from the ICB therapy. Biomarkers associated with ICB response, resistance and prognosis have been subjected to intensive research in the past decade. Early studies focused on the analysis of tumor specimens and their residing microenvironment. However, biopsies can be challenging to obtain in clinical practice, and do not reflect the dynamic changes of immunological parameters during the ICB therapy. Recent studies have investigated profiles of antigen-specific T cells derived from the peripheral compartment using multi-omics approaches. By tracking the clonotype and diversity of tumor-reactive T cell receptor repertoire, these studies collectively establish that de novo priming of antigen-specific T cells in peripheral blood occurs throughout the course of ICB, whereas preexisting T cells prior to ICB are exhausted to various degrees. Here, we review what is known about ICB-induced T cell phenotypic and functional changes in cancer patients both within the tumor microenvironment and in the peripheral compartment. A better understanding of parameters influencing the response to ICBs will provide rationales for developing novel diagnostics and combinatorial therapeutic strategies to maximize the clinical efficacies of ICB therapies.

Bioanalytical Assays for Pharmacokinetic and Biodistribution Study of Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) are produced by the chemical linkage of cytotoxic agents and monoclonal antibodies. The complexity and heterogeneity of ADCs and the low concentration of cytotoxic agent released in vivo poses big challenges to their bioanalysis. Understanding the pharmacokinetic behavior, exposure-safety, and exposure-efficacy relationships of ADCs is needed for their successful development. Accurate analytical methods are required to evaluate intact ADCs, total antibody, released small molecule cytotoxins, and related metabolites. The selection of appropriate bioanalysis methods for comprehensive analysis of ADCs is mainly dependent on the properties of cytotoxic agents, the chemical linker, and the attachment sites. The quality of the information about the whole pharmacokinetic profile of ADCs has been improved due to the development and improvement of analytical strategies for detection of ADCs, such as ligand-binding assays and mass spectrometry-related techniques. In this article, we will focus on the bioanalytical assays that have been used in the pharmacokinetic study of ADCs and discuss their advantages, current limitations, and potential challenges. SIGNIFICANCE STATEMENT: This article describes bioanalysis methods which have been used in pharmacokinetic study of ADCs and discusses the advantages, disadvantages and potential challenges of these assays. This review is useful and helpful and will provide insights and reference for bioanalysis and development of ADCs.

Hepatocellular carcinoma: Preclinical and clinical applications of nanotechnology with the potential role of carbohydrate receptors

Hepatocellular carcinoma (HCC) is one of the most common types of liver cancer; accounts for 75-85% of cases. The treatment and management of HCC involve different sanative options like surgery, chemotherapy, immunotherapy, etc. Recently, various advancements have been introduced for the diagnosis and targeting of hepatic tumor cells. Among these, biomarkers are considered the primary source for the diagnosis and differentiation of tumor cells. With the advancement in the field of nanotechnology, different types of nanocarriers have been witnessed in tumor targeting. Nanocarriers such as nanoparticles, liposomes, polymeric micelles, nanofibers, etc. are readily prepared for effective tumor targeting with minimal side-effects. The emergence of various approaches tends to improve the effectiveness of these nanocarriers as demonstrated in ample clinical trials. This review focuses on the significant role of carbohydrates such as mannose, galactose, fructose, etc. in the development, diagnosis, and therapy of HCC. Hence, the current focus of this review is to acknowledge various perspectives regarding the occurrence, diagnosis, treatment, and management of HCC.

Self-Assembled Multivalent Aptamer Drug Conjugates: Enhanced Targeting and Cytotoxicity for HER2-Positive Gastric Cancer

Antibody drug conjugates (ADCs) have shown promise to be the mainstream chemotherapeutics for advanced HER2-positive cancers, yet the issues of poor drug delivery efficiency, limited chemotherapeutic effects, severe immune responses, and drug resistance remain to be addressed before the clinical applications of ADCs. The DNA aptamer-guided drug conjugates (ApDCs) are receiving growing attention for specific tumors due to their excellent tumor affinity and low cost. Therefore, developing a multivalent ApDC nanomedicine by combining anti-HER2 aptamer (HApt), tetrahedral framework nucleic acid (tFNA), and deruxtecan (Dxd) together to form HApt-tFNA@Dxd might help to address these concerns. In this study, the HER2-targeted DNA aptamer modified DNA tetrahedron (HApt-tFNA) was employed as a system for drug delivery, and the adoption of tFNA could effectively enlarge the drug-loading rate compared to aptamer-guided ApDCs previously reported. Compared with free Dxd and tFNA@Dxd, HApt-tFNA@Dxd showed better structural stability, excellent targeted cytotoxicity to HER2-positive gastric cancer, and increased tissue aggregation ability in tumors. These features and superiorities make HApt-tFNA@Dxd a promising chemotherapeutic medicine for HER2-positive tumors. Our work developed a new targeting nanomedicine by combining DNA nanomaterials and chemotherapeutic agents, which represents a critical advance toward developing novel DNA-based nanomaterials and promoting their potential applications for HER2-positive cancer therapy.

Antibody-Drug Conjugates in Breast Cancer: Current Status and Future Directions

Antibody drug conjugates (ADCs) are novel medications that combine monoclonal antibodies with cytotoxic payloads, enabling the selective delivery of potent drugs to cancer cells expressing specific surface antigens. This targeted strategy seeks to optimize treatment effectiveness while reducing the risk of systemic toxicity, distinguishing ADCs from conventional chemotherapy. The rapid growth in ADC research has led to numerous developments and approvals for cancer treatment, with significant impacts on the management of breast cancer. ADCs like T-DXd for HER2-low disease and sacituzumab govitecan for triple negative breast cancer (TNBC) have provided valuable options for challenging subtypes of breast cancer. However, essential questions still need to be addressed, including the optimal order of ADCs amidst the growing number of newly developed ones and strategies to overcome resistance mechanisms. Preclinical studies have shed light on potential resistance mechanisms, emphasizing the potential benefit of combinational approaches with other agents such as immune checkpoint inhibitors (ICIs) and targeted tyrosine kinase inhibitors (TKIs) to enhance treatment effectiveness. Additionally, personalized approaches based on molecular profiling hold promise in tailoring ADC treatments to individual tumors, identifying unique molecular markers for each patient to optimize treatment efficacy while minimizing side effects.

Antibody-Drug Conjugates for Breast Cancer Treatment: Emerging Agents, Targets and Future Directions

To achieve the scheme of "magic bullets" in antitumor therapy, antibody-drug conjugates (ADCs) were developed. ADCs consist of antibodies targeting tumor-specific antigens, chemical linkers, and cytotoxic payloads that powerfully kill cancer cells. With the approval of ado-trastuzumab emtansine (T-DM1) and fam-trastuzumab deruxtecan (T-DXd), the therapeutic potentials of ADCs in breast cancer have come into the spotlight. Nearly 30 ADCs for breast cancer are under exploration to move targeted therapy forward. In this review, we summarize the presenting and emerging agents and targets of ADCs. The ADC structure and development history are also concluded. Moreover, the challenges faced and prospected future directions in this field are reviewed, which give insights into novel treatments with ADCs for breast cancer.

Synthesis, and biological evaluation of EGFR/HER2-NAMPT conjugates for tumor treatment

Throughout the reported applications of EGFR inhibitors, it is usually employed with HDAC or other targets to design multi-target inhibitors for cancer treatment. In this paper, we designed a drug conjugate that targeted EGFR&HER2 and had inhibitory activity of NAMPT simultaneously. Compound 20c significantly inhibited the EGFR&HER2 and NAMPT enzyme activities, and had comparable or even higher anti-proliferative activity than lapatinib in various cancer cells with over-expressed EGFR and HER2. Importantly, 20c was expected to increase sensitivity to EGFR inhibitor-resistant cells. In Osimertinib-resistant cells (NCI-1975 cells with the L858R/T790M/C797S triple mutation and Ba/F3 cells with the Del19/T790M/C797S triple mutation), the anti-proliferative activity of compound 20c was increased by more than twofold compared with Osimertinib, so as to obtain better curative effect. This strategy is a promising method of embedding multiple pharmacophores into a single molecule, which lays a good foundation for the design and synthesis of small molecule drug conjugates with strong targeting ability and high cytotoxicity.

Antibody-drug conjugates: the evolving field of targeted chemotherapy for breast cancer treatment

Antibody-drug conjugates (ADCs) are a class of antineoplastic agents whose structure is composed of three main components: a monoclonal antibody (mAB) targeting a specific target antigen, a cytotoxic payload, and a linker binding the antibody to the payload. By combining the specificity of mABs with the high potency of the payloads, ADCs constitute a smart drug delivery system with improved therapeutic index. After recognition and binding of the mAB to its target surface antigen, ADCs are internalized by endocytosis by the tumor cell, releasing the payloads into the cytoplasm, where they exert their cytotoxic activity, eventually leading to cell death. The composition of some of the new ADCs confers additional functional properties that allow expanding their activity to neighboring cells not expressing the target antigen, constituting a valuable strategy to overcome tumor heterogeneity. Some of these 'off-target effects', such as the bystander effect, are possibly the mechanism underlying the antitumor activity demonstrated in patients with low expression of the target antigens, which represents an important paradigm shift in anticancer targeted therapy. Three ADCs are currently approved for the treatment of breast cancer (BC); two anti-HER2 (human epidermal growth factor receptor 2) ADCs (trastuzumab emtansine and trastuzumab deruxtecan); and one Trop-2-targeted ADC (sacituzumab govitecan). Based on the unprecedented efficacy data demonstrated by these agents, ADCs have been incorporated as part of standard regimens for all subtypes of advanced BC, as well as for high-risk early HER2-positive BC. Despite the remarkable advances, several hurdles still remain to overcome, including the development of reliable biomarkers for patient selection, prevention, and management of potentially severe toxicities, ADC resistance mechanisms, post-ADC resistance patterns, and optimal treatment sequencing and combinations. In this review, we will summarize the currently available evidence related to the use of these agents, as well as explore the current landscape of ADC development for BC treatment.

Clinical perspective: Antibody-drug conjugates for the treatment of HER2-positive breast cancer

Antibody-drug conjugates (ADCs) are a promising class of cancer biopharmaceuticals that exploit the specificity of a monoclonal antibody (mAb) to selectively deliver highly cytotoxic small molecules to targeted cancer cells, leading to an enhanced therapeutic index through increased antitumor activity and decreased off-target toxicity. ADCs hold great promise for the treatment of patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer after the approval and tremendous success of trastuzumab emtansine and trastuzumab deruxtecan, representing a turning point in both HER2-positive breast cancer treatment and ADC technology. Additionally and importantly, a total of 29 ADC candidates are now being investigated in different stages of clinical development for the treatment of HER2-positive breast cancer. The purpose of this review is to provide an insight into the ADC field in cancer treatment and present a comprehensive overview of ADCs approved or under clinical investigation for the treatment of HER2-positive breast cancer.

Novel formats of antibody conjugates: recent advances in payload diversity, conjugation, and linker chemistry

INTRODUCTION

In the field of bioconjugates, the focus on antibody - drug conjugates (ADCs) with novel payloads beyond the traditional categories of potent cytotoxic agents is increasing. These innovative ADCs exhibit various molecular formats, ranging from small-molecule payloads, such as immune agonists and proteolytic agents, to macromolecular payloads, such as oligonucleotides and proteins.

AREAS COVERED

This review offers an in-depth exploration of unconventional strategies for designing conjugates with novel mechanisms of action and notable examples of approaches that show promising prospects. Representative examples of novel format payloads and their classification, attributes, and appropriate conjugation techniques are discussed in detail.

EXPERT OPINION

The existing basic technologies used to manufacture ADCs can be directly applied to synthesize novel formatted conjugates. However, a wide variety of new payloads require the creation of customized technologies adapted to the unique characteristics of these payloads. Consequently, fundamental technologies, such as conjugation methods aimed at achieving high drug - antibody ratios and developing stable crosslinkers, are likely to become increasingly important research areas in the future.

Antibody-drug conjugates (ADCs) targeting TROP-2 in lung cancer

INTRODUCTION

The advent of antibody-drug conjugates (ADCs) represents a renewed strategy in the era of precision oncology. Several epithelial tumors harbor overexpression of the trophoblast cell-surface antigen 2 (TROP-2), which represents a predictor of poor prognosis and a promising target for anticancer therapy.

AREAS COVERED

In this review, we aim to collect the available preclinical and clinical data regarding anti-TROP-2 ADCs in lung cancer obtained through extensive literature research and screening of the available abstract/posters presented at recent meetings.

EXPERT OPINION

Anti-TROP-2 ADCs represent an innovative upcoming weapon against both non-small cell lung cancer and small cell lung cancer subtypes, pending the results of several ongoing trials. The proper combination and placement of this agent throughout the lung cancer treatment pathway, the identification of potentially predictive biomarkers of benefit, as well as the optimal management and impact of peculiar toxicity (i.e. interstitial lung disease) are the next questions to be answered.

Tuftsin-tailored fusion protein inhibits the growth of circulating gastric tumor cells associated with macrophage phagocytosis

Circulating tumor cells (CTCs) are a major cause of tumor metastasis and resistance to anticancer therapies. To date, no effective low-toxicity chemotherapeutic agents or antibodies have exhibited significant clinical activity against CTCs. Macrophages are important mediators of antitumor immunity. Tuftsin (TF), a tetrapeptide located at residues 289-292 of the CH2 domain of the Fc region of the IgG heavy chain, binds to Nrp-1, a receptor on the surface of macrophages that promotes phagocytosis and induces nonspecific activation of the immune system against tumors. Lidamycin (LDM) is an antitumor chemotherapy agent that is strongly cytotoxic to tumors and can dissociate into an apoprotein (LDP) and active enediyne (AE) in vitro. We previously constructed the fusion protein LDP-TF through genetic engineering and inserted the chromophore AE to produce LDM-TF, which can target macrophages to promote their phagocytic and cytotoxic activity against tumor cells. Preliminary experiments confirmed the anti-tumor activity of LDM-TFs. In this study, we found that LDM-TF effectively inhibited the growth of CTCs of gastric cancer origin and enhanced macrophage phagocytosis both in vivo and in vitro. Tumor cell expression of CD47, which helps to evade phagocytosis by macrophages, was substantially downregulated by LDM-TF. Notably, our in vitro experiments demonstrated that the combination of LDM-TF and anti-CD47 antibodies promoted phagocytosis more than either component alone. Our findings demonstrate the significant inhibitory effect of LDM-TF on the growth of CTCs of gastric cancer origin and suggest that the combination of LDM-TF and anti-CD47 antibodies may exhibit synergistic effects, thereby providing a new option for the clinical treatment of patients with advanced tumors that have metastasized.

A sensitive LC-MS/MS assay to quantitate free payload Aur0101 from ADC PYX-201 in rat and monkey plasma

Aim: Aur0101 is a cytotoxic and small-molecule microtubule depolymerizing agent, and is the payload conjugated to antibody-drug conjugate PYX-201. Developing and validating a sensitive bioanalytical method to quantitate Aur0101 was novel and crucial in preclinical PYX-201 studies. Materials & methods: Reference standard Aur0101 and its stable isotope labelled internal standard Aur0101-d8 were used in this LC-MS/MS method. Results: This sensitive assay was validated at a lower limit of quantitation of 15 pg/ml and successfully applied to support preclinical rat and monkey toxicology studies. Preclinical plasma toxicokinetic parameters were presented. Conclusion: A sensitive and robust LC-MS/MS assay was validated for Aur0101 in rat and monkey plasma.

Added Value of Internal Fragments for Top-Down Mass Spectrometry of Intact Monoclonal Antibodies and Antibody-Drug Conjugates

Monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) are two of the most important therapeutic drug classes that require extensive characterization, whereas their large size and structural complexity make them challenging to characterize and demand the use of advanced analytical methods. Top-down mass spectrometry (TD-MS) is an emerging technique that minimizes sample preparation and preserves endogenous post-translational modifications (PTMs); however, TD-MS of large proteins suffers from low fragmentation efficiency, limiting the sequence and structure information that can be obtained. Here, we show that including the assignment of internal fragments in native TD-MS of an intact mAb and an ADC can improve their molecular characterization. For the NIST mAb, internal fragments can access the sequence region constrained by disulfide bonds to increase the TD-MS sequence coverage to over 75%. Important PTM information, including intrachain disulfide connectivity and N-glycosylation sites, can be revealed after including internal fragments. For a heterogeneous lysine-linked ADC, we show that assigning internal fragments improves the identification of drug conjugation sites to achieve a coverage of 58% of all putative conjugation sites. This proof-of-principle study demonstrates the potential value of including internal fragments in native TD-MS of intact mAbs and ADCs, and this analytical strategy can be extended to bottom-up and middle-down MS approaches to achieve even more comprehensive characterization of important therapeutic molecules.

Dual-Warhead Conjugate Based on Fibroblast Growth Factor 2 Dimer Loaded with α-Amanitin and Monomethyl Auristatin E Exhibits Superior Cytotoxicity towards Cancer Cells Overproducing Fibroblast Growth Factor Receptor 1

Targeting fibroblast growth factor receptor 1 (FGFR1) is a promising therapeutic strategy for various cancers associated with alterations in the FGFR1 gene. In this study, we developed a highly cytotoxic bioconjugate based on fibroblast growth factor 2 (FGF2), which is a natural ligand of this receptor, and two potent cytotoxic drugs-α-amanitin and monomethyl auristatin E-with completely independent mechanistic modes of action. Utilizing recombinant DNA technology, we produced an FGF2 N- to C-end dimer that exhibited superior internalization capacity in FGFR1-positive cells. The drugs were site-specifically attached to the targeting protein using SnoopLigase- and evolved sortase A-mediated ligations. The resulting dimeric dual-warhead conjugate selectively binds to the FGFR1 and utilizes receptor-mediated endocytosis to enter the cells. Moreover, our results demonstrate that the developed conjugate exhibits about 10-fold higher cytotoxic potency against FGFR1-positive cell lines than an equimolar mixture of single-warhead conjugates. The diversified mode of action of the dual-warhead conjugate may help to overcome the potential acquired resistance of FGFR1-overproducing cancer cells to single cytotoxic drugs.

Development, efficacy and side effects of antibody‑drug conjugates for cancer therapy (Review)

Antibody-drug conjugates (ADCs) are anticancer drugs that combine cytotoxic small-molecule drugs (payloads) with monoclonal antibodies through a chemical linker and that transfer toxic payloads to tumor cells expressing target antigens. All ADCs are based on human IgG. In 2009, the Food and Drug Administration (FDA) approved gemtuzumab ozogamicin as the initial first-generation ADC. Since then, at least 100 ADC-related projects have been initiated, and 14 ADCs are currently being tested in clinical trials. The limited success of gemtuzumab ozogamicin has led to the development of optimization strategies for the next generation of drugs. Subsequently, experts have improved the first-generation ADCs and have developed second-generation ADCs such as ado-trastuzumab emtansine. Second-generation ADCs have higher specific antigen levels, more stable linkers and longer half-lives and show great potential to transform cancer treatment models. Since the first two generations of ADCs have served as a good foundation, the development of ADCs is accelerating, and third-generation ADCs, represented by trastuzumab deruxtecan, are ready for wide application. Third-generation ADCs are characterized by strong pharmacokinetics and high pharmaceutical activity, and their drug-to-antibody ratio mainly ranges from 2 to 4. In the past decade, the research prospects of ADCs have broadened, and an increasing number of specific antigen targets and mechanisms of cytotoxic drug release have been discovered and studied. To date, seven ADCs have been approved by the FDA for lymphoma, and three have been approved to treat breast cancer. The present review explores the function and development of ADCs and their clinical use in cancer treatment.

Antibody-drug conjugates: the clinical development in gastric cancer

Gastric cancer (GC) is a prevalent malignant tumor of the digestive system worldwide, ranking among the top five in terms of incidence and mortality. However, the clinical efficacy of conventional treatments for gastric cancer remains limited, with a median overall survival of approximately eight months for advanced cases. In recent years, researchers have increasingly focused on antibody-drug conjugates (ADCs) as a promising approach. ADCs are potent chemical drugs that selectively target cancer cells by binding to specific cell surface receptors with antibodies. Notably, ADCs have demonstrated promising results in clinical studies and have made significant strides in the treatment of gastric cancer. Currently, several ADCs are under investigation in clinical trials for gastric cancer patients, targeting various receptors such as EGFR, HER-2, HER-3, CLDN18.2, Mucin 1, among others. This review offers a comprehensive exploration of ADC drug characteristics and provides an overview of the research progress in ADC-based therapies for gastric cancer.

Antibody drug conjugates as targeted cancer therapy: past development, present challenges and future opportunities

Antibody drug conjugates (ADCs) are promising cancer therapeutics with minimal toxicity as compared to small cytotoxic molecules alone and have shown the evidence to overcome resistance against tumor and prevent relapse of cancer. The ADC has a potential to change the paradigm of cancer chemotherapeutic treatment. At present, 13 ADCs have been approved by USFDA for the treatment of various types of solid tumor and haematological malignancies. This review covers the three structural components of an ADC-antibody, linker, and cytotoxic payload-along with their respective structure, chemistry, mechanism of action, and influence on the activity of ADCs. It covers comprehensive insight on structural role of linker towards efficacy, stability & toxicity of ADCs, different types of linkers & various conjugation techniques. A brief overview of various analytical techniques used for the qualitative and quantitative analysis of ADC is summarized. The current challenges of ADCs, such as heterogeneity, bystander effect, protein aggregation, inefficient internalization or poor penetration into tumor cells, narrow therapeutic index, emergence of resistance, etc., are outlined along with recent advances and future opportunities for the development of more promising next-generation ADCs.

Antibody-Drug Conjugates in Gynecologic Cancer

The present article reviews the current evidence for antibody-drug conjugates (ADCs) in gynecologic cancer. ADCs consist of a highly selective monoclonal antibody for a tumor-associated antigen and a potent cytotoxic payload conjugated through a linker. Overall, the toxicity profiles of ADCs are manageable. Ocular toxicity is a known class effect of some ADCs and is managed with prophylactic corticosteroid and vasoconstrictor eye drops as well as dose interruptions/holds and dose modifications. In ovarian cancer, mirvetuximab soravtansine, an ADC targeting alpha-folate receptor (FRα), received US Food and Drug Administration (FDA) accelerated approval in November 2022 after data from the single-arm phase III SORAYA trial. A second ADC targeting FRα, STRO-002, received FDA fast track designation in August 2021. Multiple studies with upifitamab rilsodotin, an ADC comprising a NaPi2B-binding antibody, are underway. In cervical cancer, tisotumab vedotin, an ADC-targeting tissue factor, received FDA accelerated approval in September 2021 after the phase II innovaTV 204 trial. Tisotumab vedotin in combination with chemotherapy and other targeted agents is currently being evaluated. Although there are no currently approved ADCs for endometrial cancer, there are many under active evaluation, including mirvetuximab soravtansine. Trastuzumab-deruxtecan (T-DXd), an ADC targeting human epidermal growth factor receptor 2 (HER2), is currently approved for HER2-positive and HER2-low breast cancer and shows promise in endometrial cancer. Like all anticancer treatments, the decision for a patient to undergo therapy with an ADC is a personal choice that balances the potential benefits with the side effects and requires thorough and compassionate support of their physician and care team and shared decision making.

Optimizing Conjugation Chemistry, Antibody Conjugation Site, and Surface Density in Antibody-Nanogel Conjugates (ANCs) for Cell-Specific Drug Delivery

Targeted delivery of therapeutics using antibody-nanogel conjugates (ANCs) with a high drug-to-antibody ratio has the potential to overcome some of the inherent limitations of antibody-drug conjugates (ADCs). ANC platforms with simple preparation methods and precise tunability to evaluate structure-activity relationships will greatly contribute to translating this promise into clinical reality. In this work, using trastuzumab as a model antibody, we demonstrate a block copolymer-based ANC platform that allows highly efficient antibody conjugation and formulation. In addition to showcasing the advantages of using an inverse electron-demand Diels-Alder (iEDDA)-based antibody conjugation, we evaluate the influence of antibody surface density and conjugation site on the nanogels upon the targeting capability of ANCs. We show that compared to traditional strain-promoted alkyne-azide cycloadditions, the preparation of ANCs using iEDDA provides significantly higher efficiency, which results in a shortened reaction time, simplified purification process, and enhanced targeting toward cancer cells. We also find that a site-specific disulfide-rebridging method in antibodies offers similar targeting abilities as the more indiscriminate lysine-based conjugation method. The more efficient bioconjugation using iEDDA allows us to optimize the avidity by fine-tuning the surface density of antibodies on the nanogel. Finally, with trastuzumab-mertansine (DM1) antibody-drug combination, our ANC demonstrates superior activities in vitro compared to the corresponding ADC, further highlighting the potential of ANCs in future clinical translation.

Emerging Targeted Therapies for HER2-Positive Breast Cancer

Breast cancer is the most common cancer in women and the leading cause of death. HER2 overexpression is found in approximately 20% of breast cancers and is associated with a poor prognosis and a shorter overall survival. Tratuzumab, a monoclonal antibody directed against the HER2 receptor, is the standard of care treatment. However, a third of the patients do not respond to therapy. Given the high rate of resistance, other HER2-targeted strategies have been developed, including monoclonal antibodies such as pertuzumab and margetuximab, trastuzumab-based antibody drug conjugates such as trastuzumab-emtansine (T-DM1) and trastuzumab-deruxtecan (T-DXd), and tyrosine kinase inhibitors like lapatinib and tucatinib, among others. Moreover, T-DXd has proven to be of use in the HER2-low subtype, which suggests that other HER2-targeted therapies could be successful in this recently defined new breast cancer subclassification. When patients progress to multiple strategies, there are several HER2-targeted therapies available; however, treatment options are limited, and the potential combination with other drugs, immune checkpoint inhibitors, CAR-T cells, CAR-NK, CAR-M, and vaccines is an interesting and appealing field that is still in development. In this review, we will discuss the highlights and pitfalls of the different HER2-targeted therapies and potential combinations to overcome metastatic disease and resistance to therapy.

Target Antigen Attributes and Their Contributions to Clinically Approved Antibody-Drug Conjugates (ADCs) in Haematopoietic and Solid Cancers

Antibody drug conjugates (ADCs) are powerful anti-cancer therapies comprising an antibody joined to a cytotoxic payload through a chemical linker. ADCs exploit the specificity of antibodies for their target antigens, combined with the potency of cytotoxic drugs, to selectively kill target antigen-expressing tumour cells. The recent rapid advancement of the ADC field has so far yielded twelve and eight ADCs approved by the US and EU regulatory bodies, respectively. These serve as effective targeted treatments for several haematological and solid tumour types. In the development of an ADC, the judicious choice of an antibody target antigen with high expression on malignant cells but restricted expression on normal tissues and immune cells is considered crucial to achieve selectivity and potency while minimising on-target off-tumour toxicities. Aside from this paradigm, the selection of an antigen for an ADC requires consideration of several factors relating to the expression pattern and biological features of the target antigen. In this review, we discuss the attributes of antigens selected as targets for antibodies used in clinically approved ADCs for the treatment of haematological and solid malignancies. We discuss target expression, functions, and cellular kinetics, and we consider how these factors might contribute to ADC efficacy.

Targeting the Epidermal Growth Factor Receptor with Molecular Degraders: State-of-the-Art and Future Opportunities

Epidermal growth factor receptor (EGFR) is an oncogenic drug target and plays a critical role in several cellular functions including cancer cell growth, survival, proliferation, differentiation, and motility. Several small-molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs) have been approved for targeting intracellular and extracellular domains of EGFR, respectively. However, cancer heterogeneity, mutations in the catalytic domain of EGFR, and persistent drug resistance limited their use. Different novel modalities are gaining a position in the limelight of anti-EGFR therapeutics to overcome such limitations. The current perspective reflects upon newer modalities, importantly the molecular degraders such as PROTACs, LYTACs, AUTECs, and ATTECs, etc., beginning with a snapshot of traditional and existing anti-EGFR therapies including small molecule inhibitors, mAbs, and antibody drug conjugates (ADCs). Further, a special emphasis has been made on the design, synthesis, successful applications, state-of-the-art, and emerging future opportunities of each discussed modality.