Antibody-drug conjugates come of age in oncology

Emerging strategy for the treatment of urothelial carcinoma: Advances in antibody-drug conjugates combination therapy

Urothelial carcinoma (UC) is a prevalent malignant tumor involving the urinary system. Although there are various treatment modalities, including surgery, chemotherapy, and immune checkpoint inhibitor (ICI) therapy, some patients experience disease recurrence and metastasis with poor prognosis and dismal long-term survival. Antibody-drug conjugates (ADCs), which combine the targeting ability of antibody drugs with the cytotoxicity of chemotherapeutic drugs, have recently emerged as a prominent research focus in the development of individualized precision cancer therapy. Although ADCs have improved the overall response rate in patients with UC, their effectiveness remains limited. Currently, ADC-based combination therapies, particularly ADC combined with ICIs, have demonstrated promising efficacy. This combination approach has advanced the treatment of UC, exhibiting the potential to become the standard first-line therapy for advanced UC in the future. This article reviewed clinical trials involving ADC-based combination therapy for UC and discussed the possible challenges and future perspectives to provide guidance for the clinical treatment of UC.

Recent strategies for evoking immunogenic Pyroptosis in antitumor immunotherapy

Pyroptosis is a specific type of programmed cell death (PCD) characterized by distinct morphological changes, including cell swelling, membrane blebbing, DNA fragmentation, and eventual cell lysis. Pyroptosis is closely associated with human-related diseases, such as inflammation and malignancies. Since the initial observation of pyroptosis in Shigella flexneri-infected macrophages more than 20 years ago, various pyroptosis-inducing agents, including ions, small molecules, and biological nanomaterials, have been developed for tumor treatment. Given that pyroptosis can activate the body's robust immune response against tumor and promote the formation of the body's long-term immune memory in tumor treatment, its status as a type of immunogenic cell death is self-evident. Therefore, pyroptosis should be used as a powerful anti-tumor strategy. However, there still is a lack of a comprehensive summary of the most recent advances in pyroptosis-based cancer therapy. Therefore, it is vital to fill this gap and inspire future drug design to better induce tumor cells to undergo pyroptosis to achieve advanced anti-tumor effects. In this review, we summarize in detail the most recent advances in triggering tumor cell immunogenic pyroptosis for adequate tumor clearance based on various treatment modalities, and highlight material design and therapeutic advantages. Besides, we also provide an outlook on the prospects of this emerging field in the next development.

Advances in the study of marketed antibody-drug Conjugates (ADCs) for the treatment of breast cancer

Breast cancer continues to have a high incidence rate among female malignancies. Despite significant advancements in treatment modalities, the heterogeneous nature of breast cancer and its resistance to various therapeutic approaches pose considerable challenges. Antibody-drug conjugates (ADCs) effectively merge the specificity of antibodies with the cytotoxicity of chemotherapeutic agents, offering a novel strategy for precision treatment of breast cancer. Notably, trastuzumab emtansine (T-DM1) has provided a new therapeutic option for HER2-positive breast cancer patients globally, especially those resistant to conventional treatments. The development of trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG) has further broadened the applicability of ADCs in breast cancer therapy, presenting new hopes for patients with low HER2 expression and triple-negative breast cancer. However, the application of ADCs presents certain challenges. For instance, their treatment may lead to adverse reactions such as interstitial lung disease, thrombocytopenia, and diarrhea. Moreover, prolonged treatment could result in ADCs resistance, complicating the therapeutic process. Economically, the high costs of ADCs might hinder their accessibility in low-income regions. This article reviews the structure, mechanism of action, and clinical trials of commercially available ADCs for breast cancer treatment, with a focus on the clinical trials of the three drugs, aiming to provide insights for clinical applications and future research.

Development and Validation of an ADA-Tolerant Assay for Quantification of an Exatecan-Based ADC in Monkey Plasma

BACKGROUND

The development of an anti-drug antibody (ADA)-tolerant pharmacokinetic (PK) assay is important when the drug exposure is irrelevant to toxicity in the presence of ADA. We aimed to develop and validate an ADA-tolerant assay for an exatecan-based antibody-drug conjugate (ADC) in monkey plasma.

RESULTS

The assay tolerated 5.00 µg/mL of ADA at 12 µg/mL of ADC. Its accuracy and precision results satisfied the acceptance criteria. Furthermore, the assay was free from hook and matrix effects and exhibited good dilutional linearity. Additionally, the ADC in plasma samples was stable under different storage conditions.

METHOD

An ADA-tolerant ADC assay was configured with an anti-payload antibody for capture, and a drug-target protein combined with a horseradish peroxidase (HRP)-labeled antibody against a drug-target-protein tag for detection. Samples were firstly acidified to dissociate drug and ADA complexes, and to convert the carboxylate form to the lactone form of exatecan molecules; then, the ADAs in the samples were removed with a naked antibody-coated microplate. The treated samples were further incubated with coated anti-payload antibody and captured ADC molecules were quantified by the detection reagent. The developed assay was optimized and validated against regulatory guidelines.

CONCLUSIONS

The assay met both methodological and sample-related ADA tolerance requirements, and was applicable to a nonclinical study in cynomolgus monkeys.

Antibody-Drug Conjugates: The Dynamic Evolution from Conventional to Next-Generation Constructs

Introduced almost two decades ago, ADCs have marked a breakthrough in the targeted therapy era, providing clinical benefits to many cancer patients. While the inherent complexity of this class of drugs has challenged their development and broad application, the experience gained from years of trials and errors and recent advances in construct design and delivery have led to an increased number of ADCs approved or in late clinical development in only five years. Target and payload diversification, along with novel conjugation and linker technologies, are at the forefront of next-generation ADC development, renewing hopes to broaden the scope of these targeted drugs to difficult-to-treat cancers and beyond. This review highlights recent trends in the ADC field, focusing on construct design and mechanism of action and their implications on ADCs' therapeutic profile. The evolution from conventional to innovative ADC formats will be illustrated, along with some of the current hurdles, including toxicity and drug resistance. Future directions to improve the design of next-generation ADCs will also be presented.

Adrenal crisis mainly manifested as recurrent syncope secondary to tislelizumab: a case report and literature review

As an immune checkpoint inhibitor (ICI), tislelizumab is an anti-programmed cell death protein 1 (PD-1) drug. With the extensive application of ICIs, there is an ever-increasing proportion of immune-related adverse events (irAEs) in clinical settings, some of which may even be life-threatening. Herein, we present a patient with tislelizumab-induced adrenal crisis. The main clinical manifestation was recurrent syncope accompanied by high-grade fever. Timely identification and hormone replacement therapy helped the patient overcome the crisis well. Finally, the patient discontinued tislelizumab and switched to antibody-drug conjugate (ADC) therapy. We report this case to improve our understanding of this situation, identify this kind of disease, and prevent adrenal crisis in time. Eventually, limiting toxicities reduces the interruption of immunotherapy. Since irAEs are multisystem damage with more non-specific symptoms, except for oncologists, general practitioners who endorse the need for taking a holistic approach to the patient should play a vital role in the management of cancer treatment.

The Nitrile Bis-Thiol Bioconjugation Reaction

Electron-poor aryl nitriles are promising reagents for bioconjugation due to their high electrophilicity and selectivity for reaction with thiols, albeit generally in a reversible manner. A transient species has previously been observed in such reactions, involving the addition of two thiols to the nitrile functional group, forming a tetrahedral amino dithioacetal (ADTA). In this work, the reaction of heteroaryl nitriles with bis-thiols is explored in an attempt to generate stable ADTAs, which could facilitate new bioconjugation protocols. By use of a 1,2-dithiol, or the incorporation of an electrophilic trap into the aryl nitrile design, the formation of stable products is achieved. The resultant "nitrile bis-thiol" (NBT) reaction is then explored in the context of protein modification, specifically to carry out antibody conjugation. By addition of these nitriles to the reduced disulfide bond of an antibody fragment, it is shown that, depending on the reagent design, cysteine-to-lysine transfer or disulfide bridged NBT products can be generated. Both represent site-selective conjugates and are shown to be stable when challenged with glutathione under physiological conditions and upon incubation in serum. Furthermore, the NBT reaction is tested in the more challenging context of a full antibody, and all four disulfide bonds are effectively modified by these new one-carbon bridging reagents. Overall, this reaction of heteroaryl-nitriles with bis-thiols is shown to be highly efficient and versatile, of tunable reversibility, and offers enticing prospects as a new addition to the toolbox of biocompatible "click"-type reactions.

ADCdb: the database of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are a class of innovative biopharmaceutical drugs, which, via their antibody (mAb) component, deliver and release their potent warhead (a.k.a. payload) at the disease site, thereby simultaneously improving the efficacy of delivered therapy and reducing its off-target toxicity. To design ADCs of promising efficacy, it is crucial to have the critical data of pharma-information and biological activities for each ADC. However, no such database has been constructed yet. In this study, a database named ADCdb focusing on providing ADC information (especially its pharma-information and biological activities) from multiple perspectives was thus developed. Particularly, a total of 6572 ADCs (359 approved by FDA or in clinical trial pipeline, 501 in preclinical test, 819 with in-vivo testing data, 1868 with cell line/target testing data, 3025 without in-vivo/cell line/target testing data) together with their explicit pharma-information was collected and provided. Moreover, a total of 9171 literature-reported activities were discovered, which were identified from diverse clinical trial pipelines, model organisms, patient/cell-derived xenograft models, etc. Due to the significance of ADCs and their relevant data, this new database was expected to attract broad interests from diverse research fields of current biopharmaceutical drug discovery. The ADCdb is now publicly accessible at: https://idrblab.org/adcdb/.

Rapid purification of mAb using protein a membranes yielding high HCP clearance

Protein A chromatography remains the crucial step in mAb purification because of the high binding specificity and impurity clearance. In recent years, highly productive membrane adsorbers emerged as an alternative to traditional resins allowing for rapid purification of biomolecules. In this study, we tested three commercially available protein A membranes (Sartobind® Rapid A, HiTrap Fibro™ PrismA and GORE™ Protein Capture Device) regarding flow distribution, permeability and binding performance. As an application study using a cell-culture supernatant (CCS) containing monoclonal antibodies (mAbs), acidic and high pH wash steps were investigated regarding recovery and impurity removal. All membranes proved their applicability as highly productive capture media leading to high HCP and DNA removal with no observable influence on recovery. GORE™ Protein Capture Device exhibited a superior flow distribution but revealed diffusional limitations at high flow rates. Sartobind® Rapid A and HiTrap Fibro™ PrismA showed binding capacities of ∼ 40 g/L even at residence times (RTs) < 12 s but were limited by hydrodynamics suggesting room for improvement with optimized membrane housing.

A pivotal decade for bispecific antibodies?

Bispecific antibodies (bsAbs) are a class of antibodies that can mediate novel mechanisms of action compared to monospecific monoclonal antibodies (mAbs). Since the discovery of mAbs and their adoption as therapeutic agents in the 1980s and 1990s, the development of bsAbs has held substantial appeal. Nevertheless, only three bsAbs (catumaxomab, blinatumomab, emicizumab) were approved through the end of 2020. However, since then, 11 bsAbs received regulatory agency approvals, of which nine (amivantamab, tebentafusp, mosunetuzumab, cadonilimab, teclistamab, glofitamab, epcoritamab, talquetamab, elranatamab) were approved for the treatment of cancer and two (faricimab, ozoralizumab) in non-oncology indications. Notably, of the 13 currently approved bsAbs, two, emicizumab and faricimab, have achieved blockbuster status, showing the promise of this novel class of therapeutics. In the 2020s, the approval of additional bsAbs can be expected in hematological malignancies, solid tumors and non-oncology indications, establishing bsAbs as essential part of the therapeutic armamentarium.

Nanomedicine Combats Drug Resistance in Lung Cancer

Lung cancer is the second most prevalent cancer and the leading cause of cancer-related death worldwide. Surgery, chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy are currently available as treatment methods. However, drug resistance is a significant factor in the failure of lung cancer treatments. Novel therapeutics have been exploited to address complicated resistance mechanisms of lung cancer and the advancement of nanomedicine is extremely promising in terms of overcoming drug resistance. Nanomedicine equipped with multifunctional and tunable physiochemical properties in alignment with tumor genetic profiles can achieve precise, safe, and effective treatment while minimizing or eradicating drug resistance in cancer. Here, this work reviews the discovered resistance mechanisms for lung cancer chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy, and outlines novel strategies for the development of nanomedicine against drug resistance. This work focuses on engineering design, customized delivery, current challenges, and clinical translation of nanomedicine in the application of resistant lung cancer.

Adavosertib and beyond: Biomarkers, drug combination and toxicity of WEE1 inhibitors

WEE1 kinase is renowned as an S-G2 checkpoint inhibitor activated by ATR-CHK1 in response to replication stress. WEE1 inhibition enhances replication stress and effectively circumvents checkpoints into mitosis, which triggers significant genetic impairs and culminates in cell death. This approach has been validated clinically for its promising anti-tumor efficacy across various cancer types, notably in cases of ovarian cancers. Nonetheless, the initial stage of clinical trials has shown that the first-in-human WEE1 inhibitor adavosertib is limited by dose-limiting adverse events. As a result, recent efforts have been made to explore predictive biomarkers and smart combination schedules to alleviate adverse effects. In this review, we focused on the exploration of therapeutic biomarkers, as well as schedules of combination utilizing WEE1 inhibitors and canonical anticancer drugs, according to the latest preclinical and clinical studies, indicating that the optimal application of WEE1 inhibitors will likely be as part of dose-reducing combination and be tailored to specific patient populations.

Antibody and Cell-Based Therapies against Virus-Induced Cancers in the Context of HIV/AIDS

Infectious agents, notably viruses, can cause or increase the risk of cancer occurrences. These agents often disrupt normal cellular functions, promote uncontrolled proliferation and growth, and trigger chronic inflammation, leading to cancer. Approximately 20% of all cancer cases in humans are associated with an infectious pathogen. The International Agency for Research on Cancer (IARC) recognizes seven viruses as direct oncogenic agents, including Epstein-Barr Virus (EBV), Kaposi's Sarcoma-associated herpesvirus (KSHV), human T-cell leukemia virus type-1 (HTLV-1), human papilloma virus (HPV), hepatitis C virus (HCV), hepatitis B virus (HBV), and human immunodeficiency virus type 1 (HIV-1). Most viruses linked to increased cancer risk are typically transmitted through contact with contaminated body fluids and high-risk behaviors. The risk of infection can be reduced through vaccinations and routine testing, as well as recognizing and addressing risky behaviors and staying informed about public health concerns. Numerous strategies are currently in pre-clinical phases or undergoing clinical trials for targeting cancers driven by viral infections. Herein, we provide an overview of risk factors associated with increased cancer incidence in people living with HIV (PLWH) as well as other chronic viral infections, and contributing factors such as aging, toxicity from ART, coinfections, and comorbidities. Furthermore, we highlight both antibody- and cell-based strategies directed against virus-induced cancers while also emphasizing approaches aimed at discovering cures or achieving complete remission for affected individuals.

Design, Synthesis, and Biochemical Analysis of a Molecule Designed to Enhance Endosomal Escape

RNA therapeutics, including siRNAs, ASOs, and PMOs, have great potential to treat human disease. However, RNA therapeutics are too large, too charged, and/or too hydrophilic to cross the cellular membrane and are instead taken up into cells by endocytosis. Unfortunately, the vast majority of RNA therapeutics remain trapped inside endosomes (≥ 99%), which is the sole reason preventing their use to treat cancer, COVID, and other diseases. In contrast, enveloped viruses, such as influenza, also have an endosomal escape problem, but have evolved a highly efficient endosomal escape mechanism using trimeric hemagglutinin (HA) fusogenic protein. HA contains an outer hydrophilic domain (HA1) that masks an inner hydrophobic fusogenic/endosomal escape domain (HA2). Once inside endosomes, HA1 is shed to expose HA2 that, due to hydrophobicity, buries itself into the endosomal lipid bilayer, driving escape into the cytoplasm in a non-toxic fashion. To begin to address the RNA therapeutics rate-limiting endosomal escape problem, we report here a first step in the design and synthesis of a universal endosomal escape domain (uEED) that biomimics the enveloped virus escape mechanism. uEED contains an outer hydrophilic mask covalently attached to an inner hydrophobic escape domain. In plasma, uEED is inert and highly metabolically stable; however, when placed in endo/lysosomal conditions, uEED is activated by enzymatic removal of the hydrophilic mask, followed by self-immolation of the linker resulting in exposure of the hydrophobic indole ring domain in the absence of any hydrophilic tags. Thus, uEED is a synthetic biomimetic of the highly efficient viral endosomal escape mechanism.

Rapid Access to Potent Bispecific T Cell Engagers Using Biogenic Tyrosine Click Chemistry

Bispecific antibodies as T cell engagers designed to display binding capabilities to both tumor-associated antigens and antigens on T cells are considered promising agents in the fight against cancer. Even though chemical strategies to develop such constructs have emerged, a method that readily converts a therapeutically applied antibody into a bispecific construct by a fully non-genetic process is not yet available. Herein, we report the application of a biogenic, tyrosine-based click reaction utilizing chemoenzymatic modifications of native IgG1 antibodies to generate a synthetic bispecific antibody construct that exhibits tumor-killing capability at picomolar concentrations. Control experiments revealed that a covalent linkage of the different components is required for the observed biological activities. In view of the highly potent nature of the constructs and the modular approach that relies on convenient synthetic methods utilizing therapeutically approved biomolecules, our method expedites the production of potent bispecific antibody constructs with tunable cell killing efficacy with significant impact on therapeutic properties.

Antibody-drug conjugates in urinary tumors: clinical application, challenge, and perspectives

Urinary tumors primarily consist of kidney, urothelial, and prostate malignancies, which pose significant treatment challenges, particularly in advanced stages. Antibody-drug conjugates (ADCs) have emerged as a promising therapeutic approach, combining monoclonal antibody specificity with cytotoxic chemotherapeutic payloads. This review highlights recent advancements, opportunities, and challenges in ADC application for urinary tumors. We discuss the FDA-approved ADCs and other novel ADCs under investigation, emphasizing their potential to improve patient outcomes. Furthermore, we explore strategies to address challenges, such as toxicity management, predictive biomarker identification, and resistance mechanisms. Additionally, we examine the integration of ADCs with other treatment modalities, including immune checkpoint inhibitors, targeted therapies, and radiation therapy. By addressing these challenges and exploring innovative approaches, the development of ADCs may significantly enhance therapeutic options and outcomes for patients with advanced urinary tumor.

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.

Copper assisted sequence-specific chemical protein conjugation at a single backbone amide

Direct, site-specific methods of protein functionalization are highly desirable for biotechnology. However, such methods are challenging due to the difficulty of chemically differentiating a single site within a large protein. Herein, we propose "metal binding targeting" strategy and develop a Copper Assisted Sequence-specific conjugation Tag (CAST) method to achieve rapid (second order rate 8.1 M-1 s-1), site-specific protein backbone chemical modification with pinpoint accuracy. We demonstrate the versatility of CAST conjugation by preparing various on-demand modified recombinant proteins, including a homogeneous antibody-drug conjugate with high plasma stability and potent efficacy in vitro and in vivo. Thus, CAST provides an efficient and quantitative method to site-specifically attach payloads on large, native proteins.

Introduction of Carbonyl Groups into Antibodies

Antibodies and their derivatives (scFv, Fabs, etc.) represent a unique class of biomolecules that combine selectivity with the ability to target drug delivery. Currently, one of the most promising endeavors in this field is the development of molecular diagnostic tools and antibody-based therapeutic agents, including antibody-drug conjugates (ADCs). To meet this challenge, it is imperative to advance methods for modifying antibodies. A particularly promising strategy involves the introduction of carbonyl groups into the antibody that are amenable to further modification by biorthogonal reactions, namely aliphatic, aromatic, and α-oxo aldehydes, as well as aliphatic and aryl-alkyl ketones. In this review, we summarize the preparation methods and applications of site-specific antibody conjugates that are synthesized using this approach.

Nickel-Catalyzed Antibody Bioconjugation

New biocompatible methods for post-translational protein modification are challenging to develop but crucial to create improved chemical probes and optimize next-generation biologic therapies such as antibody-drug conjugates (ADCs). Herein, we describe the bottom-up construction of an aqueous nickel-catalyzed cross-coupling for the chemospecific arylation of cysteine residues on peptides and proteins and its use for the preparation of ADCs. A variety of arene linkages are exemplified, enabling the incorporation of small molecules, probes, and cytotoxic payloads. The utility of this new bioconjugation platform in a drug discovery setting is highlighted by the construction of novel ADCs with target-mediated in vitro cytotoxic activity.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.

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.

HPLC-DAD validated method for DM4 and its metabolite S-Me-DM4 quantification in biological matrix for clinical and pharmaceutical applications

The present study focuses on the development and validation of an HPLC-DAD methodology for the detection of a potent chemotherapeutic agent, Maytansinoid Ravtansine (DM4), and its metabolite, S-methyl-DM4 (S-Me-DM4), in plasma samples. Methodologically, after a simple protein precipitation with acetonitrile and after drying 1 mL of supernatant, the sample (suspended with N,N-Dimethylacetamide, DMA) was directly analyzed by HPLC under isocratic elution using a mobile phase comprising milliQ water and methanol (25:75, v:v), both acidified with 0.1 % v:v formic acid. Employing a flow rate of 1.0 mL/min and a reversed-phase GraceSmart RP18 column thermostated at 40 °C, we achieved complete resolution and separation of DM4 and S-Me-DM4 within 13 min. The optimized injection volume of 20 μL and the wavelength set at 254 nm were utilized for quantitative analyses. Rigorous validation has not only ensured its reliability and reproducibility but has also addressed potential limitations associated with methodological inconsistency. The limit of detection and quantification of the method were 0.025 and 0.06 μg/mL for both the analytes, respectively. The calibration curve showed a good linearity in the range 0.06-20 μg/mL. For both analytes, the intraday precision and trueness were 2.3-8.2 % and -1.1 to 3.1 %, respectively, while the interday values were 0.7-10.1 % and -10.4 to 7.5 %, respectively. The developed methodology enables the concurrent determination and quantification of free DM4 and its metabolite, free S-Me-DM4, making it a valuable tool for assessing the pharmacokinetics and pharmacodynamics of DM4-based therapies. In addition, the procedure was successfully applied to analyse the presence of free DM4 or its metabolite, free S-Me-DM4, in human plasma samples spiked with the 1959-sss/DM4 antibody-drug conjugate (ADC). The utilization of the herein validated methodology allowed to confirm the presence of these analytes, thereby providing insights into their potential release from the ADC structure.

Studying Intermolecular Interactions in an Antibody-Drug Conjugate Through Chemical Screening and Computational Modeling

Antibody-drug conjugates (ADCs) combine the selectivity of antibodies with the cytotoxicity of drug payloads to yield highly targeted and potent therapeutics. Owing to the need to chemically modify residues for attachment of the payload and their more complex structure compared to either component alone, ADCs can present additional challenges related to stability of the final drug product. Here, we report for the first time the use of high-throughput experimental screens and computational techniques to tune the conformational and colloidal behavior of a monomethyl auristatin F-based ADC. The ADC, which exhibits high opalescence with strongly attractive protein-protein interactions, is transformed into a more stable structure by experimentally traversing a library of more than ∼100 formulations. A significant reduction in turbidity and increase in diffusion interaction parameter is observed by varying properties such as pH and ionic strength. Computational modeling rationalized these changes and pointed to the presence of attractive electrostatic interactions between ADC molecules facilitated by the drug payload and histidine residues. Taken together, the experimental and computational work presented provides a general roadmap of studies to perform during ADC development to find stable formulations, while the mechanistic learnings can be applied towards the design and stabilization of other IgG1-based ADCs.

Penetration of Nanobody-Dextran Polymer Conjugates through Tumor Spheroids

Here we report the generation of nanobody dextran polymer conjugates (dextraknobs) that are loaded with small molecules, i.e., fluorophores or photosensitizers, for potential applications in cancer diagnostics and therapy. To this end, the molecules are conjugated to the dextran polymer which is coupled to the C-terminus of an EGFR-specific nanobody using chemoenzymatic approaches. A monovalent EGFR-targeted nanobody and biparatopic version modified with different dextran average molecular weights (1000, 5000, and 10,000) were probed for their ability to penetrate tumor spheroids. For monovalent Cy5-labeled dextraknobs, the utilization of smaller sized dextran (MW 5000 vs. 10,000) was found to be beneficial for more homogeneous penetration into A431 tumor spheroids over time. For the biparatopic dual nanobody comprising MW 1000, 5000, and 10,000 dextran labeled with photosensitizer IRDye700DX, penetration behavior was comparable to that of a direct nanobody-photosensitizer conjugate lacking a dextran scaffold. Additionally, dextraknobs labeled with IRDye700DX incubated with cells in 2D and 3D showed potent cell killing upon illumination, thus inducing photodynamic therapy (PDT). In line with previous results, monovalent nanobody conjugates displayed deeper and more homogenous penetration through spheroids than the bivalent conjugates. Importantly, the smaller size dextrans did not affect the distribution of the conjugates, thus encouraging further development of dextraknobs.

A comprehensive overview on antibody-drug conjugates: from the conceptualization to cancer therapy

Antibody-Drug Conjugates (ADCs) represent an innovative class of potent anti-cancer compounds that are widely used in the treatment of hematologic malignancies and solid tumors. Unlike conventional chemotherapeutic drug-based therapies, that are mainly associated with modest specificity and therapeutic benefit, the three key components that form an ADC (a monoclonal antibody bound to a cytotoxic drug via a chemical linker moiety) achieve remarkable improvement in terms of targeted killing of cancer cells and, while sparing healthy tissues, a reduction in systemic side effects caused by off-tumor toxicity. Based on their beneficial mechanism of action, 15 ADCs have been approved to date by the market approval by the Food and Drug Administration (FDA), the European Medicines Agency (EMA) and/or other international governmental agencies for use in clinical oncology, and hundreds are undergoing evaluation in the preclinical and clinical phases. Here, our aim is to provide a comprehensive overview of the key features revolving around ADC therapeutic strategy including their structural and targeting properties, mechanism of action, the role of the tumor microenvironment and review the approved ADCs in clinical oncology, providing discussion regarding their toxicity profile, clinical manifestations and use in novel combination therapies. Finally, we briefly review ADCs in other pathological contexts and provide key information regarding ADC manufacturing and analytical characterization.

Discovery of VIP236, an αvβ3-Targeted Small-Molecule-Drug Conjugate with Neutrophil Elastase-Mediated Activation of 7-Ethyl Camptothecin Payload for Treatment of Solid Tumors

The emerging field of small-molecule-drug conjugates (SMDCs) using small-molecule biomarker-targeted compounds for tumor homing may provide new perspectives for targeted delivery. Here, for the first time, we disclose the structure and the synthesis of VIP236, an SMDC designed for the treatment of metastatic solid tumors by targeting αvβ3 integrins and extracellular cleavage of the 7-ethyl camptothecin payload by neutrophil elastase in the tumor microenvironment. Imaging studies in the Lewis lung mouse model using an elastase cleavable quenched substrate showed pronounced elastase activity in the tumor. Pharmacokinetics studies of VIP236 in tumor-bearing mice demonstrated high stability of the SMDC in plasma and high tumor accumulation of the cleaved payload. Studies in bile-duct-cannulated rats showed that biliary excretion of the unmodified conjugate is the primary route of elimination. Treatment- and time-dependent phosphorylation of H2AX, a marker of DNA damage downstream of topoisomerase 1 inhibition, verified the on-target activity of the payload cleaved from VIP236 in vivo. Treatment with VIP236 resulted in long-lasting tumor regression in subcutaneous patient-derived xenograft (PDX) models from patients with non-small-cell lung, colon, and renal cancer as well as in two orthotopic metastatic triple-negative breast cancer PDX models. In these models, a significant reduction of brain and lung metastases also was observed.

Antibody-Drug Conjugates for the Treatment of Renal Cancer: A Scoping Review on Current Evidence and Clinical Perspectives

Antibody-drug conjugates (ADCs) are complex chemical structures composed of a monoclonal antibody, serving as a link to target cells, which is conjugated with a potent cytotoxic drug (i.e., payload) through a chemical linker. Inspired by Paul Ehrlich's concept of the ideal anticancer drug as a "magic bullet", ADCs are also highly specific anticancer agents, as they have been demonstrated to recognize, bind, and neutralize cancer cells, limiting injuries to normal cells. ADCs are among the newest pharmacologic breakthroughs in treating solid and hematologic malignancies. Indeed, in recent years, various ADCs have been approved by the Food and Drug Administration and European Medicines Agency for the treatment of several cancers, resulting in a "practice-changing" approach. However, despite these successes, no ADC is approved for treating patients affected by renal cell carcinoma (RCC). In the present paper, we thoroughly reviewed the current literature and summarized preclinical studies and clinical trials that evaluated the activity and toxicity profile of ADCs in RCC patients. Moreover, we scrutinized the potential causes that, until now, hampered the therapeutical success of ADCs in those patients. Finally, we discussed novel strategies that would improve the development of ADCs and their efficacy in treating RCC patients.

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.

The endosomal-lysosomal system in ADC design and cancer therapy

INTRODUCTION

This discourse delves into the intricate connections between the endosomal-lysosomal system and antibody-drug conjugates (ADCs), shedding light on an essential yet less understood dimension of targeted therapy. While ADCs have revolutionized cancer treatment, resistance remains a formidable challenge, often involving diverse and overlapping mechanisms.

AREAS COVERED

This discourse highlights the roles of various components within the endosomal machinery, including Rab proteins, in ADC resistance development. It also explores how the transferrin-transferrin receptor and epidermal growth factor-epidermal growth factor receptor complexes, known for their roles in recycling and degradation process, respectively, can offer valuable insights for ADC design. Selected strategies to enhance lysosomal targeting are discussed, and potentially offer solutions to improve ADC efficacy.

EXPERT OPINION

By harnessing these different insights that connect ADCs with the endosomal-lysosomal system, the field may benefit to shape the next-generation of ADC design for increased efficacy and improved patient outcomes.