Impact of Endocytosis Mechanisms for the Receptors Targeted by the Currently Approved Antibody-Drug Conjugates (ADCs)-A Necessity for Future ADC Research and Development

Sacituzumab tirumotecan in advanced non-small-cell lung cancer with or without EGFR mutations: phase 1/2 and phase 2 trials

Trophoblast cell-surface antigen 2 (TROP2)-directed antibody-drug conjugate (ADC) is a promising anticancer agent that has shown remarkable efficacy in several malignancies. However, in lung cancer, two phase 3 trials on TROP2-ADCs in unselected patients with advanced non-small-cell lung cancer (NSCLC) have both failed. Sacituzumab tirumotecan (sac-TMT) is a novel TROP2-directed ADC. Here we report the efficacy and safety of sac-TMT in previously treated, advanced NSCLC with or without activating EGFR mutations from the phase 1/2 KL264-01 and phase 2 SKB264-II-08 studies. Primary endpoint was objective response rate (ORR). KL264-01 enrolled EGFR-wild-type and EGFR-mutant NSCLC (n = 43). Confirmed ORR was 40% (17 of 43; 95% confidence interval (CI), 25-56). Median progression-free survival (PFS) was 6.2 months (95% CI, 5.3-11.3). Post-hoc subgroup analyses found better outcomes in the EGFR-mutant subset (22 of 43, 51%) with a confirmed ORR of 55% (12 of 22) and median PFS of 11.1 months. These findings were independently supported by results from SKB264-II-08, where sac-TMT led to confirmed ORR of 34% (22 of 64; 95% CI, 23-47) and median PFS of 9.3 months (95% CI, 7.6-11.4) in 64 patients with EGFR-mutant NSCLC. For a total of 107 patients receiving sac-TMT, the most common treatment-related adverse events were hematologic toxicities. Diarrhea (4%) and interstitial lung disease (1%) were uncommon. Exploration of potential mechanisms revealed that the presence of EGFR mutation substantially increased the internalization and activity of sac-TMT in vitro. Overall, sac-TMT showed encouraging single-agent activity and manageable tolerability in previously treated, advanced NSCLC with EGFR mutations. Randomized phase 3 trials in treatment-naive and previously treated patients with EGFR-mutant NSCLC are ongoing. ClinicalTrials.gov Identifiers: NCT04152499 , NCT05631262 .

Opportunities and Challenges in Antibody-Drug Conjugates for Cancer Therapy: A New Era for Cancer Treatment

The antibody, linker, and payload moieties all play a significant role in giving the ADC its unique therapeutic potential. The antibody subclass employed in ADCs is determined based on relative individual receptor affinities and pharmacokinetics. Meanwhile, the linker used in an ADC can either be cleavable or non-cleavable. ADC therapy comprises antibody-dependent mechanisms in addition to the direct cytotoxic effects of the payload. These include antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, as well as the "bystander effect", which refers to the diffusion of a portion of the cytotoxic molecules out of the target cell, exerting its cytotoxic effect on the adjacent cells. Target antigens of ADCs are expected to be expressed on the membranes of the cancer cells facing the external matrix, although new approaches utilize antigens regarding tumor-associated cells, the tumor microenvironment, or the tumor vasculature. These target antigens of ADCs not only determine the efficacy of these agents but also impact the off-targets and related adverse effects. The majority of ADC-related toxicities are associated with off-targets. The proposed mechanisms of ADC resistance include disrupted intracellular drug trafficking, dysfunctional lysosomal processing, and the efflux of the cytotoxic molecule via ATP-binding cassette (ABC) transporters. The latter mechanism is especially prominent for multi-drug-resistant tumors. An important limitation of ADCs is the penetration of the conjugate into the tumor microenvironment and their delivery to target cancer cells. Cancerous tissues' vascular profile and the steric "binding site barrier" formed around the peripheral vessels of tumors stand as potential challenges of ADC therapy for solid tumors. As research efforts focus on reducing toxicities, overcoming resistance, and improving pharmacokinetics, ADC options for cancer therapy are expected to continue to diversify, including standalone approaches and combination therapies.

Antibody-drug conjugates in breast cancer treatment: resistance mechanisms and the role of therapeutic sequencing

Antibody-drug conjugates (ADCs) are a transformative approach in breast cancer therapy, offering targeted treatment with reduced toxicity by selectively delivering cytotoxic agents to cancer cells. While ADCs like trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd), and sacituzumab govitecan have shown significant efficacy, resistance mechanisms such as antigen loss, impaired internalization, and efflux of cytotoxic payloads challenge their effectiveness. This review discusses these resistance mechanisms and explores advanced strategies to overcome them, including innovations in linker chemistry, multi-antigen targeting, and biomarker-driven personalization. Additionally, therapeutic sequencing - determining the optimal order of ADCs with other treatments such as chemotherapy, endocrine therapy, and immunotherapy - is examined as a crucial approach to maximize ADC efficacy and manage resistance. Evidence-based sequencing strategies, particularly for human epidermal growth factor receptor 2 (HER2)-positive and triple-negative breast cancer (TNBC), are supported by clinical trials demonstrating the benefits of ADCs in both early-stage and metastatic settings. The potential of combination therapies, such as ADCs with immune checkpoint inhibitors (ICIs), further highlights the evolving landscape of breast cancer treatment. As ADC technology advances, personalized approaches integrating biomarkers and optimized sequencing protocols offer promising avenues to enhance treatment outcomes and combat resistance in breast cancer.

Clathrin functions in intracellular sorting during receptor-mediated endocytosis

Clathrin is a key protein involved in receptor-mediated endocytosis (RME), which is also known as clathrin-mediated endocytosis (CME). Ligand/receptor binding facilitates clathrin clustering and cell surface invagination. We recently found that the typical CME ligand transferrin (Tf) can be internalized into cells without the clathrin heavy chain (CLTC). In this study, we clarified the unknown roles of clathrin during intracellular trafficking. Microscopic observation revealed that Tf accumulates in the deeper compartments of CLTC-knockdown HeLa cells. A colocalization analysis with endosome/lysosome markers showed that endocytosed Tf moves to early/late endosomes and then to lysosomes in CLTC-knockdown cells. This suggests that clathrin contributes to the recycling and exocytosis of endocytosed molecules.

Unlocking Natural Potential: Antibody-Drug Conjugates With Naturally Derived Payloads for Cancer Therapy

Natural compound-derived chemotherapies remain central to cancer treatment, however, they often cause off-target side effects that negatively impact patients' quality of life. In contrast, antibody-drug conjugates (ADCs) combine cytotoxic payloads with antibodies to specifically target cancer cells. Most approved and clinically investigated ADCs utilize naturally derived payloads, while those with conventional synthetic molecular payloads remain limited. This review focuses on approved ADCs that enhance the efficacy of naturally derived payloads by linking them with antibodies. We provide an overview of the core components of ADCs, their working mechanisms, and FDA-approved ADCs featuring naturally derived payloads, such as calicheamicin, camptothecin, dolastatin 10, maytansine, pyrrolbenzodiazepine (PBD), and the immunotoxin Pseudomonas exotoxin A. This review also explores recent clinical advancements aimed at broadening the therapeutic potential of ADCs, their applicability in treating heterogeneously composed tumors and their potential use beyond oncology. Additionally, this review highlights naturally derived payloads that are currently being clinically investigated but have not yet received approval. By summarizing the current landscape, this review provides insights into promising avenues for exploration and contributes to the refinement of treatment protocols for improved patient outcomes.

Cathepsin B dependent activatable trigger fluorophore (CAT-Fluor) for in situ functional imaging of antibody-drug conjugates

Antibody-drug conjugates (ADC) have emerged as an important class of therapeutic agents that combine the target specificity of a monoclonal antibody with the potency of a cytotoxic payload. Despite clinical success, our understanding of receptor endocytosis and ADC toxicity remains limited. Less than 1% of ADCs reach tumors, raising concerns about off-target cytotoxicity. To shed light on these issues, our study introduces a smart antibody-fluorophore conjugate (sAFC) with Cathepsin B dependent Activatable Trigger Fluorophore (CAT-Fluor) to mimic ADC behavior in situ. Using a Cathepsin B-cleavable linker, we linked a Si-rhodamine (SiR) derivative with superior near-infrared emission to antibodies, creating sAFC. Carbamoylation of the primary amino group on SiR is employed to conjugate with the linker and inhibit the electron-push-pull effect of the xanthene skeleton, thus inducing fluorescence quenching. In vitro, the anti-EGFR sAFC emulates ADC metabolism and suggests that specific proteins implicated in endocytosis, like caveolin, significantly influence ADC internalization efficacy, potentially correlating with drug resistance. In vivo studies using sAFC demonstrate that 'passenger ADCs' found in normal tissues release minimal payload, likely elucidating how ADCs mitigate dose-limiting toxicities. Therefore, our sAFC-based strategy, combining CAT-Fluor and targeted interventions, quantitatively and objectively evaluated the impact of various stages and key proteins in the physiological process, spanning from antigen recognition, endocytosis mechanism, to transport and protein hydrolysis, on ADC efficiency. This comprehensive approach lays a mechanistic foundation for advancing ADC research and development, and offers novel insights into tackling ADC efficacy, resistance and potential toxicities from the standpoint of endocytosis mechanisms.

Targeting uPAR with an antibody-drug conjugate suppresses tumor growth and reshapes the immune landscape in pancreatic cancer models

Antibody-drug conjugates (ADCs) hold promise to advance targeted therapy of pancreatic ductal adenocarcinoma (PDAC), where the desmoplastic tumor stroma challenges effective treatment. Here, we explored the urokinase plasminogen activator receptor (uPAR) as a candidate ADC target in PDAC, harnessing its massive tumoral and stromal expression in this stroma-dense tumor. We generated a site-specific ADC offering high-affinity, cross-species reactivity, and efficient internalization of the anti-uPAR monoclonal antibody, FL1, carrying a potent anthracycline derivative (PNU-158692). In vitro, FL1-PNU exhibited potent and specific cytotoxicity against uPAR-expressing PDAC cell lines, stromal and immune cells, and bystander killing of uPAR-negative cells. In vivo, the ADC induced remission or sustained tumor regression and extended survival in xenograft models. In syngeneic orthotopic models, the antitumor effect promoted immunomodulation by enhancing infiltrating immune effectors and decreasing immunosuppressive cells. This study lays grounds for further exploring FL1-PNU as a putative clinical ADC candidate, potentially providing a promising therapeutic avenue for PDAC as a monotherapy or in combinatorial regimens.

Emerging Nanoparticle-Based Diagnostics and Therapeutics for Cancer: Innovations and Challenges

Malignant growth is expected to surpass other significant causes of death as one of the top reasons for dismalness and mortality worldwide. According to a World Health Organization (WHO) study, this illness causes approximately between 9 and 10 million instances of deaths annually. Chemotherapy, radiation, and surgery are the three main methods of treating cancer. These methods seek to completely eradicate all cancer cells while having the fewest possible unintended impacts on healthy cell types. Owing to the lack of target selectivity, the majority of medications have substantial side effects. On the other hand, nanomaterials have transformed the identification, diagnosis, and management of cancer. Nanostructures with biomimetic properties have been grown as of late, fully intent on observing and treating the sickness. These nanostructures are expected to be consumed by growth in areas with profound disease. Furthermore, because of their extraordinary physicochemical properties, which incorporate nanoscale aspects, a more prominent surface region, explicit geometrical features, and the ability to embody different substances within or on their outside surfaces, nanostructures are remarkable nano-vehicles for conveying restorative specialists to their designated regions. This review discusses recent developments in nanostructured materials such as graphene, dendrimers, cell-penetrating peptide nanoparticles, nanoliposomes, lipid nanoparticles, magnetic nanoparticles, and nano-omics in the diagnosis and management of cancer.

Exosomal PVRL4 Promotes Lung Adenocarcinoma Progression by Enhancing the Generation of Myeloid-Derived Suppressor Cell-Secreted TGF-β1

BACKGROUND

The cancer cell marker poliovirus receptor-like protein 4 (PVRL4) has been shown to be highly expressed in many cancers, including lung cancer. Myeloid-derived suppressor cells (MDSCs) are a population of immature myeloid cells with immunosuppressive roles that can attenuate the anticancer response. Here, the precise functions and the relationship between PVRL4 and MDSCs in lung adenocarcinoma (LUAD) progression were investigated.

METHODS

Detection of levels of mRNAs and proteins was conducted using qRT-PCR and western blotting. The CCK-8, colony formation, transwell, wound healing assays, and flow cytometry were used to explore cell growth, invasion, migration, and apoptosis, respectively. ELISA analysis detected TGF-β1 contents. LUAD mouse models were established for in vivo assay. Exosomes were isolated by ultracentrifugation. MDSCs were induced from peripheral blood mononuclear cells (PBMCs) by cytokine or co-culture with cancer cells.

RESULTS

LUAD tissues and cells showed high PVRL4 expression, and PVRL4 deficiency suppressed LUAD cell proliferation, invasion, migration, and induced cell apoptosis in vitro, and impeded LUAD growth in vivo. Thereafter, we found that PVRL4 was packaged into exosomes in LUAD cells, and could be transferred into PBMCs to promote MDSC induction and the expression of MDSC-secreted TGF-β1. Functionally, the silencing of exosomal PVRL4 impaired LUAD cell proliferation, invasion, migration, and evoked cell apoptosis, which could be reversed by the incubation of TGF-β1-overexpressed MDSCs.

CONCLUSION

Exosomal PVRL4 promoted LUAD progression by inducing the secretion of TGF-β1 in MDSCs, indicating a novel direction for LUAD immunotherapy.

From past to present: The evolution of immunotherapy and its modern modalities

Immunotherapy is emerging as a novel and reliable therapeutic technique for treating diseases such as autoimmunity, HIV/AIDS, allergy and cancers. This approach works by modulating the patient's immune system, activating both the innate and humoral branches to combat life-threatening diseases. The foundation of immunotherapy began with the discovery and development of "serum therapy" by German physiologist Emil Von Behring who received the Nobel Prize in 1901 for his contributions to the treatment of diphtheria. Around the same time, Dr. William Coley expanded the field for cancer treatment by developing the first immune based cure for sarcomas using attenuated strains of bacteria injected directly into patient's tumours. As medical science advanced, a broader understanding of the immune system and its components led to the emergence of different immunotherapeutic techniques. These include adoptive cell transfer therapy, cytokine therapy, cancer vaccines, and antibody-drug conjugates. The chapter provides a comprehensive understanding of the history and the current techniques used in immunotherapy, detailing the principles behind their mechanisms and the types of diseases tackled by each immunotherapeutic technique. By examining the journey from early discoveries to modern advancements, the chapter highlights the transformative impact of immunotherapy on medical science and patient care.

Understanding the Preclinical Efficacy of Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) represent a therapeutic modality that guides chemotherapies to tumoral cells by using antibodies against tumor-associated antigens (TAAs). The antibody and the chemotherapy or payload are attached by a chemical structure called the linker. The strategy for the development of this type of drug was based on several rational pillars, including the use of a very potent payload and the use of specific antibodies acting only on antigens expressed on tumoral cells. In this article, by using data from all approved ADCs that have received regulatory approval, we analyze the potential contribution of each ADC component to preclinical activity. We suggest that payload potency and the drug-to-antibody ratio (DAR) have a less relevant role in relation to efficacy than previously considered. Additionally, we have observed that some ADCs have been developed against antigens also present in non-transformed tissues, which could suggest that TAA specificity is not a mandatory requirement. Finally, we have identified that ADCs with payloads harboring more favorable physicochemical characteristics showed better potential activity. In this article, we also review other aspects that should be taken into consideration for ADC design, including linker structure, stability, conjugation type, pharmacokinetics, receptor internalization, and recycling. Based on currently available data, our study summaries different concepts that should be considered in the design of novel ADCs in the future.

Heterogeneous Surface CD79b Expression in Aggressive B-Cell Lymphomas Assessed by Flow Cytometry on Lymph Node Biopsies

Background: CD79b is a B-cell-specific antigen that is crucial to the B-cell receptor and is considered a key target for treatment in aggressive B-cell lymphomas. Methods: While immunohistochemical studies have shown widespread expression of CD79b in mature B-cell-derived lymphomas, flow cytometry allows for precise measurement and differentiation between surface and intracellular localization. Results: In our comparative analysis, we discovered that CD79b expression percentages and mean fluorescence intensity (MFI) were lower in a group of 127 cases of aggressive B-cell lymphomas compared to a control group of benign reactive hyperplasia. We also observed significant variability in the surface expression of CD79b among lymphoma cases, with 18% showing predominantly intracellular positivity. There was a strong correlation between the surface expression of CD79b and clonal light chains. Notably, primary mediastinal B-cell lymphomas exhibited significantly lower surface CD79b expression compared to other lymphoma subtypes (median 0.8% IQR 0-48.5 vs. 80% IQR 24-97, p = 0.0005). Furthermore, patients over 60 years old and those with a higher Revised International Prognostic Index (R-IPI) had significantly higher CD79b expression, both of which are associated with a significant benefit from adding an anti-CD79b drug conjugate to first-line chemotherapy in diffuse large B-cell lymphomas. Conclusions: In conclusion, the quantitative flow cytometric analysis of CD79b surface expression in aggressive B-cell lymphomas provides clinically relevant information, highlighting its potential usefulness in guiding therapeutic decisions.

Living in LALA land? Forty years of attenuating Fc effector functions

The Fc region of antibodies is vital for most of their physiological functions, many of which are engaged through binding to a range of Fc receptors. However, these same interactions are not always helpful or wanted when therapeutic antibodies are directed against self-antigens, and can sometimes cause catastrophic adverse reactions. Over the past 40 years, there have been intensive efforts to "silence" unwanted binding to Fc-gamma receptors, resulting in at least 45 different variants which have entered clinical trials. One of the best known is "LALA" (L234A/L235A). However, neither this, nor most of the other variants in clinical use are completely silenced, and in addition, the biophysical properties of many of them are compromised. I review the development of different variants to see what we can learn from their biological properties and use in the clinic. With the rise of powerful new uses of antibody therapy such as bispecific T-cell engagers, antibody-drug conjugates, and checkpoint inhibitors, it is increasingly important to optimize the Fc region as well as the antibody binding site in order to achieve the best combination of safety and efficacy.

Application and challenge of HER2DX genomic assay in HER2+ breast cancer treatment

HER2-positive breast cancer is highly aggressive, with a significant risk of recurrence and metastasis, leading to a poor prognosis. While most early-stage HER2-positive breast cancer patients benefit from combining trastuzumab monoclonal antibody with chemotherapy, the therapeutic response to various drug combinations varies across the HER2+ patient population. Therefore, predicting the prognosis and treatment response of HER2+ breast cancer patients to specific regimens is crucial for selecting appropriate precision individualized therapies. HER2DX is the first genomic tool designed to guide the treatment of HER2+ breast cancer patients. The three scores provided by HER2DX inform the entire treatment process, including predicting survival outcomes, recurrence, metastasis, and treatment responses like Pathological Complete Response Rate (pCR). It offers recommendations on follow-up intervals, treatment plans, and the duration of drug therapy. This review examines the literature and analyzes studies applying HER2DX to guide the comprehensive treatment and predict prognosis in HER2+ breast cancer patients, aiming to promote the widespread use of HER2DX in individualized treatment.

Targeting endocytosis to sensitize cancer cells to programmed cell death

Evading programmed cell death (PCD) is a hallmark of cancer that allows tumor cells to survive and proliferate unchecked. Endocytosis, the process by which cells internalize extracellular materials, has emerged as a key regulator of cell death pathways in cancer. Many tumor types exhibit dysregulated endocytic dynamics that fuel their metabolic demands, promote resistance to cytotoxic therapies, and facilitate immune evasion. This review examines the roles of endocytosis in apoptotic resistance and immune escape mechanisms utilized by cancer cells. We highlight how inhibiting endocytosis can sensitize malignant cells to therapeutic agents and restore susceptibility to PCD. Strategies to modulate endocytosis for enhanced cancer treatment are discussed, including targeting endocytic regulatory proteins, altering membrane biophysical properties, and inhibiting Rho-associated kinases. While promising, challenges remain regarding the specificity and selectivity of endocytosis-targeting agents. Nonetheless, harnessing endocytic pathways represents an attractive approach to overcome apoptotic resistance and could yield more effective therapies by rendering cancer cells vulnerable to PCD. Understanding the interplay between endocytosis and PCD regulation is crucial for developing novel anticancer strategies that selectively induce tumor cell death.

Cathepsin B Nuclear Flux in a DNA-Guided "Antinuclear Missile" Cancer Therapy

Some antinuclear antibodies (ANAs) bind extracellular nucleic acids released into tumor environments and are pulled into the nuclei of live cancer cells through nucleoside salvage pathways, independent of tumor-specific surface antigens. Here we show that ANA nuclear penetration induces nuclear flux by the lysosomal protease cathepsin B and leverage this mechanism to design an antinuclear antibody-drug conjugate (ANADC) with cathepsin B-labile drug linker. The ANADC targets nucleic acid exhaust from necrotic tumors and crosses membrane barriers through nucleoside salvage as a DNA-seeking and tumor agnostic "antinuclear missile" cancer therapy.

A novel bispecific antibody drug conjugate targeting HER2 and HER3 with potent therapeutic efficacy against breast cancer

Antibody drug conjugate (ADC) therapy has become one of the most promising approaches in cancer immunotherapy. Bispecific targeting could enhance the efficacy and safety of ADC by improving its specificity, affinity and internalization. In this study we constructed a HER2/HER3-targeting bispecific ADC (BsADC) and characterized its physiochemical properties, target specificity and internalization in vitro, and assessed its anti-tumor activities in breast cancer cell lines and in animal models. The HER2/HER3-targeting BsADC had a drug to antibody ratio (DAR) of 2.89, displayed a high selectivity against the target JIMT-1 breast cancer cells in vitro, as well as a slightly higher level of internalization than HER2- or HER3-monospecific ADCs. More importantly, the bispecific ADC potently inhibited the viability of MCF7, JIMT-1, BT474, BxPC-3 and SKOV-3 cancer cells in vitro. In JIMT-1 breast cancer xenograft mice, a single injection of bispecific ADC (3 mg/kg, i.v.) significantly inhibited the tumor growth with an efficacy comparable to that caused by combined injection of HER2 and HER3-monospecific ADCs (3 mg/kg for each). Our study demonstrates that the bispecific ADC concept can be applied to development of more potent new cancer therapeutics than the monospecific ADCs.

Antibody-drug conjugates in cancer therapy: mechanisms and clinical studies

Antibody-drug conjugates (ADCs) consist of monoclonal antibodies that target tumor cells and cytotoxic drugs linked through linkers. By leveraging antibodies' targeting properties, ADCs deliver cytotoxic drugs into tumor cells via endocytosis after identifying the tumor antigen. This precise method aims to kill tumor cells selectively while minimizing harm to normal cells, offering safe and effective therapeutic benefits. Recent years have seen significant progress in antitumor treatment with ADC development, providing patients with new and potent treatment options. With over 300 ADCs explored for various tumor indications and some already approved for clinical use, challenges such as resistance due to factors like antigen expression, ADC processing, and payload have emerged. This review aims to outline the history of ADC development, their structure, mechanism of action, recent composition advancements, target selection, completed and ongoing clinical trials, resistance mechanisms, and intervention strategies. Additionally, it will delve into the potential of ADCs with novel markers, linkers, payloads, and innovative action mechanisms to enhance cancer treatment options. The evolution of ADCs has also led to the emergence of combination therapy as a new therapeutic approach to improve drug efficacy.

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.

Recent Advances in Targeted Cancer Therapy: Are PDCs the Next Generation of ADCs?

Antibody-drug conjugates (ADCs) comprise antibodies, cytotoxic payloads, and linkers, which can integrate the advantages of antibodies and small molecule drugs to achieve targeted cancer treatment. However, ADCs also have some shortcomings, such as non-negligible drug resistance, a low therapeutic index, and payload-related toxicity. Many studies have focused on changing the composition of ADCs, and some have even further extended the concept and types of targeted conjugated drugs by replacing the targeted antibodies in ADCs with peptides, revolutionarily introducing peptide-drug conjugates (PDCs). This Perspective summarizes the current research status of ADCs and PDCs and highlights the structural innovations of ADC components. In particular, PDCs are regarded as the next generation of potential targeted drugs after ADCs, and the current challenges of PDCs are analyzed. Our aim is to offer fresh insights for the efficient design and expedited development of innovative targeted conjugated drugs.

Efficient intracellular drug delivery by co-administration of two antibodies against cell adhesion molecule 1

Cell adhesion molecule 1 (CADM1), a single-pass transmembrane protein, is involved in oncogenesis. We previously demonstrated the therapeutic efficacy of anti-CADM1 ectodomain monoclonal antibodies against mesothelioma; however, the underlying mechanism is unclear. In the present study, we explored the molecular behavior of anti-CADM1 antibodies in CADM1-expressing tumor cells. Sequencing analyses revealed that the anti-CADM1 chicken monoclonal antibodies 3E1 and 9D2 are IgY and IgM isotype antibodies, respectively. Co-administration of 3E1 and 9D2 altered the subcellular distribution of CADM1 from the detergent-soluble fraction to the detergent-resistant fraction in tumor cells. Using recombinant chicken-mouse chimeric antibodies that had been isotype-switched from IgG to IgM, we demonstrated that the combination of the variable region of 3E1 and the constant region of IgM was required for CADM1 relocation. Cytochemical studies showed that 3E1 colocalized with late endosomes/lysosomes after co-administration with 9D2, suggesting that the CADM1-antibody complex is internalized from the cell surface to intracellular compartments by lipid-raft mediated endocytosis. Finally, 3E1 was conjugated with the antimitotic agent monomethyl auristatin E (MMAE) via a cathepsin-cleavable linker. Co-administration of 3E1-monomethyl auristatin E and 9D2 suppressed the growth of multiple types of tumor cells, and this anti-tumor activity was confirmed in a syngeneic mouse model of melanoma. 3E1 and 9D2 are promising drug delivery vehicles for CADM1-expressing tumor cells.

Therapeutic prospects of nectin-4 in cancer: applications and value

Nectin-4 is a Ca2+-independent immunoglobulin-like protein that exhibits significantly elevated expression in malignant tumors while maintaining extremely low levels in healthy adult tissues. In recent years, overexpression of Nectin-4 has been implicated in tumor occurrence and development of various cancers, including breast cancer, urothelial cancer, and lung cancer. In 2019, the Food and Drug Administration approved enfortumab vedotin, the first antibody-drug conjugate targeting Nectin-4, for the treatment of urothelial carcinoma. This has emphasized the value of Nectin-4 in tumor targeted therapy and promoted the implementation of more clinical trials of enfortumab vedotin. In addition, many new drugs targeting Nectin-4 for the treatment of malignant tumors have entered clinical trials, with the aim of exploring potential new indications. However, the exact mechanisms by which Nectin-4 affects tumorigenesis and progression are still unclear, and the emergence of drug resistance and treatment-related adverse reactions poses challenges. This article reviews the diagnostic potential, prognostic significance, and molecular role of Nectin-4 in tumors, with a focus on clinical trials in the field of Nectin-4-related tumor treatment and the development of new drugs targeting Nectin-4.

Repurposing an endogenous degradation domain for antibody-mediated disposal of cell-surface proteins

The exquisite specificity of antibodies can be harnessed to effect targeted degradation of membrane proteins. Here, we demonstrate targeted protein removal utilising a protein degradation domain derived from the endogenous human protein Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9). Recombinant antibodies genetically fused to this domain drive the degradation of membrane proteins that undergo constitutive internalisation and recycling, including the transferrin receptor and the human cytomegalovirus latency-associated protein US28. We term this approach PACTAC (PCSK9-Antibody Clearance-Targeting Chimeras).

Insights into the role of derailed endocytic trafficking pathway in cancer: From the perspective of cancer hallmarks

The endocytic trafficking pathway is a highly organized cellular program responsible for the regulation of membrane components and uptake of extracellular substances. Molecules internalized into the cell through endocytosis will be sorted for degradation or recycled back to membrane, which is determined by a series of sorting events. Many receptors, enzymes, and transporters on the membrane are strictly regulated by endocytic trafficking process, and thus the endocytic pathway has a profound effect on cellular homeostasis. However, the endocytic trafficking process is typically dysregulated in cancers, which leads to the aberrant retention of receptor tyrosine kinases and immunosuppressive molecules on cell membrane, the loss of adhesion protein, as well as excessive uptake of nutrients. Therefore, hijacking endocytic trafficking pathway is an important approach for tumor cells to obtain advantages of proliferation and invasion, and to evade immune attack. Here, we summarize how dysregulated endocytic trafficking process triggers tumorigenesis and progression from the perspective of several typical cancer hallmarks. The impact of endocytic trafficking pathway to cancer therapy efficacy is also discussed.

Recent Technological and Intellectual Property Trends in Antibody-Drug Conjugate Research

Antibody-drug conjugate (ADC) therapy, an advanced therapeutic technology comprising antibodies, chemical linkers, and cytotoxic payloads, addresses the limitations of traditional chemotherapy. This study explores key elements of ADC therapy, focusing on antibody development, linker design, and cytotoxic payload delivery. The global rise in cancer incidence has driven increased investment in anticancer agents, resulting in significant growth in the ADC therapy market. Over the past two decades, notable progress has been made, with approvals for 14 ADC treatments targeting various cancers by 2022. Diverse ADC therapies for hematologic malignancies and solid tumors have emerged, with numerous candidates currently undergoing clinical trials. Recent years have seen a noteworthy increase in ADC therapy clinical trials, marked by the initiation of numerous new therapies in 2022. Research and development, coupled with patent applications, have intensified, notably from major companies like Pfizer Inc. (New York, NY, USA), AbbVie Pharmaceuticals Inc. (USA), Regeneron Pharmaceuticals Inc. (Tarrytown, NY, USA), and Seagen Inc. (Bothell, WA, USA). While ADC therapy holds great promise in anticancer treatment, challenges persist, including premature payload release and immune-related side effects. Ongoing research and innovation are crucial for advancing ADC therapy. Future developments may include novel conjugation methods, stable linker designs, efficient payload delivery technologies, and integration with nanotechnology, driving the evolution of ADC therapy in anticancer treatment.

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.

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.

Generation and Characterization of SORT1-Targeted Antibody-Drug Conjugate for the Treatment of SORT1-Positive Breast Tumor

Antibody-drug conjugates (ADCs) have greatly improved the outcomes of advanced breast tumors. However, the treatment of breast tumors with existing ADCs is still hindered by many issues, such as tumor antigen heterogeneity and drug resistance. Therefore, ADCs against new targets would provide options for the treatment of these challenges. Sortilin-1 (SORT1) may be a promising target for ADC as it is upregulated in breast cancer. To evaluate the possibility of SORT1 as an ADC target, a humanized antibody_8D302 with high affinity against SORT1 was generated. Additionally, 8D302 was conjugated with MMAE and DXd to generate two ADCs_8D302-MMAE and 8D302-DXd, respectively. Both 8D302-MMAE and 8D302-DXd showed effective cytotoxicity against SORT1 positive breast tumor cell lines and induced bystander killing. Consequently, 8D302-MMAE showed relatively better anti-tumor activity than 8D302-DXd both in vitro and in vivo, but 8D302-DXd had superior safety profile and pharmacokinetics profile over 8D302-MMAE. Furthermore, SORT1 induced faster internalization and lysosomal trafficking of antibodies and had a higher turnover compared with HER2. Also, 8D302-DXd exhibited superior cell cytotoxicity and tumor suppression over trastuzumab-DXd, a HER2-targeted ADC. We hypothesize that the high turnover of SORT1 enables SORT1-targeted ADC to be a powerful agent for the treatment of SORT1-positive breast tumor.

Multivalent protein-drug conjugates - An emerging strategy for the upgraded precision and efficiency of drug delivery to cancer cells

With almost 20 million new cases per year, cancer constitutes one of the most important challenges for public health systems. Unlike traditional chemotherapy, targeted anti-cancer strategies employ sophisticated therapeutics to precisely identify and attack cancer cells, limiting the impact of drugs on healthy cells and thereby minimizing the unwanted side effects of therapy. Protein drug conjugates (PDCs) are a rapidly growing group of targeted therapeutics, composed of a cancer-recognition factor covalently coupled to a cytotoxic drug. Several PDCs, mainly in the form of antibody-drug conjugates (ADCs) that employ monoclonal antibodies as cancer-recognition molecules, are used in the clinic and many PDCs are currently in clinical trials. Highly selective, strong and stable interaction of the PDC with the tumor marker, combined with efficient, rapid endocytosis of the receptor/PDC complex and its subsequent effective delivery to lysosomes, is critical for the efficacy of targeted cancer therapy with PDCs. However, the bivalent architecture of contemporary clinical PDCs is not optimal for tumor receptor recognition or PDCs internalization. In this review, we focus on multivalent PDCs, which represent a rapidly evolving and highly promising therapeutics that overcome most of the limitations of current bivalent PDCs, enhancing the precision and efficiency of drug delivery to cancer cells. We present an expanding set of protein scaffolds used to generate multivalent PDCs that, in addition to folding into well-defined multivalent molecular structures, enable site-specific conjugation of the cytotoxic drug to ensure PDC homogeneity. We provide an overview of the architectures of multivalent PDCs developed to date, emphasizing their efficacy in the targeted treatment of various cancers.

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.

Analyses of Genes Critical to Tumor Survival Reveal Potential 'Supertargets': Focus on Transcription

The identification of mechanisms that underlie the biology of individual tumors is aimed at the development of personalized treatment strategies. Herein, we performed a comprehensive search of genes (termed Supertargets) vital for tumors of particular tissue origin. In so doing, we used the DepMap database portal that encompasses a broad panel of cell lines with individual genes knocked out by CRISPR/Cas9 technology. For each of the 27 tumor types, we revealed the top five genes whose deletion was lethal in the particular case, indicating both known and unknown Supertargets. Most importantly, the majority of Supertargets (41%) were represented by DNA-binding transcription factors. RNAseq data analysis demonstrated that a subset of Supertargets was deregulated in clinical tumor samples but not in the respective non-malignant tissues. These results point to transcriptional mechanisms as key regulators of cell survival in specific tumors. Targeted inactivation of these factors emerges as a straightforward approach to optimize therapeutic regimens.

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.

RGD Peptidomimetic MMAE-Conjugate Addressing Integrin αVβ3-Expressing Cells with High Targeting Index

Small molecule-drug conjugates (SMDCs) mimicking the RGD sequence (-Arg-Gly-Asp-) with a non-peptide moiety require a pharmacophore-independent attachment site. A library of 36 sulfonamide-modified RGD mimetics with nM to pM affinity for integrin α_V β₃ was synthesized and analysed via DAD mapping. The best structure of the conjugable RGD mimetic was used and a linker was attached to an aromatic ring by Negishi cross-coupling. The product retained high affinity and selectivity for integrin α_V β₃ . The conjugable RGD mimetic was then attached to an enzymatically cleavable GKGEVA linker equipped with a self-immolative PABC and the antimitotic drug monomethyl auristatin E (MMAE). The resulting SMDC preferred binding to integrin α_V β₃ over α₅ β₁ in a ratio of 1 : 4519 (ELISA) and showed selectivity for α_V β₃ -positive WM115 cells over α_V β₃ -negative M21-L cells in the in vitro cell adhesion assay as well as in cell viability assays with a targeting index of 134 (M21-L/WM115).

A universal method to analyze cellular internalization mechanisms via endocytosis without non-specific cross-effects

Endocytosis is an essential biological process for nutrient absorption and intercellular communication; it can also be used to accelerate the cellular internalization of drug delivery carriers. Clarifying the cellular uptake mechanisms of unidentified endogenous and exogenous molecules and designing new effective drug delivery systems require an accurate, specific endocytosis analysis methodology. Therefore, we developed a method to specifically evaluate cellular internalization via three main endocytic pathways: clathrin- and caveolae-mediated endocytosis, and macropinocytosis. We first revealed that most known endocytosis inhibitors had no specific inhibitory effect or were cytotoxic. Second, we successfully established an alternative method using small interfering RNA to knock down dynamin-2 and caveolin-1, which are necessary for clathrin- and caveolae-mediated endocytosis, in HeLa cells. Third, we established another method to specifically analyze macropinocytosis using rottlerin on A431 cells. Finally, we validated the proposed methods by testing the cellular internalization of a biological molecule (insulin) and carriers (nanoparticles and cell-penetrating peptides). Through this study, we established versatile methods to precisely and specifically evaluate endocytosis of newly developed biopharmaceuticals or drug delivery systems.

Exploration of the antibody-drug conjugate clinical landscape

The antibody-drug conjugate (ADC) field has undergone a renaissance, with substantial recent developmental investment and subsequent drug approvals over the past 6 y. In November 2022, ElahereTM became the latest ADC to be approved by the US Food and Drug Administration (FDA). To date, over 260 ADCs have been tested in the clinic against various oncology indications. Here, we review the clinical landscape of ADCs that are currently FDA approved (11), agents currently in clinical trials but not yet approved (164), and candidates discontinued following clinical testing (92). These clinically tested ADCs are further analyzed by their targeting tumor antigen(s), linker, payload choices, and highest clinical stage achieved, highlighting limitations associated with the discontinued drug candidates. Lastly, we discuss biologic engineering modifications preclinically demonstrated to improve the therapeutic index that if incorporated may increase the proportion of molecules that successfully transition to regulatory approval.

Preclinical profiles of SKB264, a novel anti-TROP2 antibody conjugated to topoisomerase inhibitor, demonstrated promising antitumor efficacy compared to IMMU-132

Purpose

The aim of this study was to improve the intratumoral accumulation of an antibody-drug conjugate (ADC) and minimize its off-target toxicity, SKB264, a novel anti-trophoblast antigen 2 (TROP2) ADC that was developed using 2-methylsulfonyl pyrimidine as the linker to conjugate its payload (KL610023), a belotecan-derivative topoisomerase I inhibitor. The preclinical pharmacologic profiles of SKB264 were assessed in this study.

Methods

The in vitro and in vivo pharmacologic profiles of SKB264, including efficacy, pharmacokinetics-pharmacodynamics (PK-PD), safety, and tissue distribution, were investigated using TROP2-positive cell lines, cell-derived xenograft (CDX), patient-derived xenograft (PDX) models, and cynomolgus monkeys. Moreover, some profiles were compared with IMMU-132.

Results

In vitro, SKB264 and SKB264 monoclonal antibody (mAb) had similar internalization abilities and binding affinities to TROP2. After cellular internalization, KL610023 was released and inhibited tumor cell survival. In vivo, SKB264 significantly inhibited tumor growth in a dose-dependent manner in both CDX and PDX models. After SKB264 administration, the serum or plasma concentration/exposure of SKB264 (conjugated ADC, number of payload units ≥1), total antibody (Tab, unconjugated and conjugated mAb regardless of the number of the payload units), and KL610023 in cynomolgus monkeys increased proportionally with increasing dosage from 1 to 10 mg/kg. The linker stability of SKB264 was significantly enhanced as shown by prolonged payload half-life in vivo (SKB264 vs. IMMU-132, 56.3 h vs. 15.5 h). At the same dose, SKB264's exposure in tumor tissue was 4.6-fold higher than that of IMMU-132.

Conclusions

Compared with IMMU-132, the longer half-life of SKB264 had a stronger targeting effect and better antitumor activity, suggesting the better therapeutic potential of SKB264 for treating TROP2-positive tumors.

Delivery of Drugs into Cancer Cells Using Antibody-Drug Conjugates Based on Receptor-Mediated Endocytosis and the Enhanced Permeability and Retention Effect

Innumerable people worldwide die of cancer every year, although pharmaceutical therapy has actualized many benefits in human health. For background, anti-cancer drug development is difficult due to the multifactorial pathogenesis and complicated pathology of cancers. Cancer cells excrete hydrophobic low-molecular anti-cancer drugs by overexpressed efflux transporters such as multiple drug resistance 1 (MDR1) at the apical membrane. Mutation-driven drug resistance is also developed in cancer. Moreover, the poor distribution of drug to cancer cells is a serious problem, because patients suffer from off-target side effects. Thus, highly selective and effective drug delivery into solid cancer cells across the membrane should be established. It is known that substances (10-100 nm in diameter) such as monoclonal antibodies (mAbs) (approximately 14.2 nm in diameter) or nanoparticles spontaneously gather in solid tumor stroma or parenchyma through the capillary endothelial fenestration, ranging from 200-2000 nm, in neovasculatures due to the enhanced permeability and retention (EPR) effect. Furthermore, cancer antigens, such as HER2, Nectin-4, or TROP2, highly selectively expressed on the surface of cancer cells act as a receptor for receptor-mediated endocytosis (RME) using mAbs against such antigens. Thus, antibody-drug conjugates (ADCs) are promising anti-cancer pharmaceutical agents that fulfill accurate distribution due to the EPR effect and due to antibody-antigen binding and membrane permeability owing to RME. In this review, I introduce the implementation and possibility of highly selective anti-cancer drug delivery into solid cancer cells based on the EPR effect and RME using anti-cancer antigens ADCs with payloads through suitable linkers.

BT8009; A Nectin-4 Targeting Bicycle Toxin Conjugate for Treatment of Solid Tumors

Multiple tumor types overexpress Nectin-4 and the antibody-drug conjugate (ADC), enfortumab vedotin (EV) shows striking efficacy in clinical trials for metastatic urothelial cancer, which expresses high levels of Nectin-4, validating Nectin-4 as a clinical target for toxin delivery in this indication. Despite excellent data in urothelial cancer, little efficacy data are reported for EV in other Nectin-4 expressing tumors and EV therapy can produce significant toxicities in many patients, frequently leading to discontinuation of treatment. Thus, additional approaches to this target with the potential to extend utility and reduce toxicity are warranted. We describe the preclinical development of BT8009, a "Bicycle Toxin Conjugate" (BTC) consisting of a Nectin-4-binding bicyclic peptide, a cleavable linker system and the cell penetrant toxin mono-methylauristatin E (MMAE). BT8009 shows significant antitumor activity in preclinical tumor models, across a variety of cancer indications and is well tolerated in preclinical safety studies. In several models, it shows superior or equivalent antitumor activity to an EV analog. As a small hydrophilic peptide-based drug BT8009 rapidly diffuses from the systemic circulation, through tissues to penetrate the tumor and target tumor cells. It is renally eliminated from the circulation, with a half-life of 1-2 hours in rat and non-human primate. These physical and PK characteristics differentiate BT8009 from ADCs and may provide benefit in terms of tumor penetration and reduced systemic exposure. BT8009 is currently in a Phase 1/2 multicenter clinical trial across the US, Canada, and Europe, enrolling patients with advanced solid tumors associated with Nectin-4 expression.

Immunomodulatory role of metalloproteinase ADAM17 in tumor development

ADAM17 is a member of the a disintegrin and metalloproteinase (ADAM) family of transmembrane proteases involved in the shedding of some cell membrane proteins and regulating various signaling pathways. More than 90 substrates are regulated by ADAM17, some of which are closely relevant to tumor formation and development. Besides, ADAM17 is also responsible for immune regulation and its substrate-mediated signal transduction. Recently, ADAM17 has been considered as a major target for the treatment of tumors and yet its immunomodulatory roles and mechanisms remain unclear. In this paper, we summarized the recent understanding of structure and several regulatory roles of ADAM17. Importantly, we highlighted the immunomodulatory roles of ADAM17 in tumor development, as well as small molecule inhibitors and monoclonal antibodies targeting ADAM17.

The Significance of Cell Surface N-Glycosylation for Internalization and Potency of Cytotoxic Conjugates Targeting Receptor Tyrosine Kinases

Precise anticancer therapies employing cytotoxic conjugates constitute a side-effect-limited, highly attractive alternative to commonly used cancer treatment modalities, such as conventional chemotherapy, radiotherapy or surgical interventions. Receptor tyrosine kinases are a large family of N-glycoproteins intensively studied as molecular targets for cytotoxic conjugates in various cancers. At the cell surface, these receptors are embedded in a dense carbohydrate layer formed by numerous plasma membrane glycoproteins. The complexity of the cell surface architecture is further increased by galectins, secreted lectins capable of recognizing and clustering glycoconjugates, affecting their motility and activity. Cell surface N-glycosylation is intensively remodeled by cancer cells; however, the contribution of this phenomenon to the efficiency of treatment with cytotoxic conjugates is largely unknown. Here, we evaluated the significance of N-glycosylation for the internalization and toxicity of conjugates targeting two model receptor tyrosine kinases strongly implicated in cancer: HER2 and FGFR1. We employed three conjugates of distinct molecular architecture and specificity: AffibodyHER2-vcMMAE (targeting HER2), vcMMAE-KCK-FGF1.E and T-Fc-vcMMAE (recognizing different epitopes within FGFR1). We demonstrated that inhibition of N-glycosylation reduced the cellular uptake of all conjugates tested and provided evidence for a role of the galectin network in conjugate internalization. In vitro binding studies revealed that the reduced uptake of conjugates is not due to impaired HER2 and FGFR1 binding. Importantly, we demonstrated that alteration of N-glycosylation can affect the cytotoxic potential of conjugates. Our data implicate a key role for cell surface N-glycosylation in the delivery of cytotoxic conjugates into cancer cells.

Insights into Modern Therapeutic Approaches in Pediatric Acute Leukemias

Pediatric cancers predominantly constitute lymphomas and leukemias. Recently, our knowledge and awareness about genetic diversities, and their consequences in these diseases, have greatly expanded. Modern solutions are focused on mobilizing and impacting a patient’s immune system. Strategies to stimulate the immune system, to prime an antitumor response, are of intense interest. Amid those types of therapies are chimeric antigen receptor T (CAR-T) cells, bispecific antibodies, and antibody–drug conjugates (ADC), which have already been approved in the treatment of acute lymphoblastic leukemia (ALL)/acute myeloid leukemia (AML). In addition, immune checkpoint inhibitors (ICIs), the pattern recognition receptors (PRRs), i.e., NOD-like receptors (NLRs), Toll-like receptors (TLRs), and several kinds of therapy antibodies are well on their way to showing significant benefits for patients with these diseases. This review summarizes the current knowledge of modern methods used in selected pediatric malignancies and presents therapies that may hold promise for the future.

Versatile and Robust Method for Antibody Conjugation to Nanoparticles with High Targeting Efficiency

The application of antibodies in nanomedicine is now standard practice in research since it represents an innovative approach to deliver chemotherapy agents selectively to tumors. The variety of targets or markers that are overexpressed in different types of cancers results in a high demand for antibody conjugated-nanoparticles, which are versatile and easily customizable. Considering up-scaling, the synthesis of antibody-conjugated nanoparticles should be simple and highly reproducible. Here, we developed a facile coating strategy to produce antibody-conjugated nanoparticles using 'click chemistry' and further evaluated their selectivity towards cancer cells expressing different markers. Our approach was consistently repeated for the conjugation of antibodies against CD44 and EGFR, which are prominent cancer cell markers. The functionalized particles presented excellent cell specificity towards CD44 and EGFR overexpressing cells, respectively. Our results indicated that the developed coating method is reproducible, versatile, and non-toxic, and can be used for particle functionalization with different antibodies. This grafting strategy can be applied to a wide range of nanoparticles and will contribute to the development of future targeted drug delivery systems.

FGF/FGFR-Dependent Molecular Mechanisms Underlying Anti-Cancer Drug Resistance

Simple Summary

Deregulation of the FGF/FGFR axis is associated with many types of cancer and contributes to the development of chemoresistance, limiting the effectiveness of current treatment strategies. There are several mechanisms involved in this phenomenon, including cross-talks with other signaling pathways, avoidance of apoptosis, stimulation of angiogenesis, and initiation of EMT. Here, we provide an overview of current research and approaches focusing on targeting components of the FGFR/FGF signaling module to overcome drug resistance during anti-cancer therapy.

Abstract

Increased expression of both FGF proteins and their receptors observed in many cancers is often associated with the development of chemoresistance, limiting the effectiveness of currently used anti-cancer therapies. Malfunctioning of the FGF/FGFR axis in cancer cells generates a number of molecular mechanisms that may affect the sensitivity of tumors to the applied drugs. Of key importance is the deregulation of cell signaling, which can lead to increased cell proliferation, survival, and motility, and ultimately to malignancy. Signaling pathways activated by FGFRs inhibit apoptosis, reducing the cytotoxic effect of some anti-cancer drugs. FGFRs-dependent signaling may also initiate angiogenesis and EMT, which facilitates metastasis and also correlates with drug resistance. Therefore, treatment strategies based on FGF/FGFR inhibition (using receptor inhibitors, ligand traps, monoclonal antibodies, or microRNAs) appear to be extremely promising. However, this approach may lead to further development of resistance through acquisition of specific mutations, metabolism switching, and molecular cross-talks. This review brings together information on the mechanisms underlying the involvement of the FGF/FGFR axis in the generation of drug resistance in cancer and highlights the need for further research to overcome this serious problem with novel therapeutic strategies.