Potent anticarcinoma activity of the humanized anti-CD70 antibody h1F6 conjugated to the tubulin inhibitor auristatin via an uncleavable linker

Double agents in immunotherapy: Unmasking the role of antibody drug conjugates in immune checkpoint targeting

Antibody-drug conjugates (ADCs) have high specificity with lesser off-target effects, thus providing improved efficacy over traditional chemotherapies. A total of 14 ADCs have been approved for use against cancer by the US Food and Drug Administration (FDA), with more than 100 ADCs currently in clinical trials. Of particular interest ADCs targeting immune antigens PD-L1, B7-H3, B7-H4 and integrins. Specifically, we describe ADCs in development along with the gene and protein expression of these immune checkpoints across a wide range of cancer types let url = window.clickTag || window.clickTag1 || window.clickTag2 || window.clickTag3 || window.clickTag4 || window.bsClickTAG || window.bsClickTAG1 || window.bsClickTAG2 || window.url || ''; if(typeof url == 'string'){ document.body.dataset['perxceptAdRedirectUrl'] = url;}.

Current Landscape of Antibody-Drug Conjugate Development in Head and Neck Cancer

Antibody-drug conjugates (ADCs) are fusions of therapeutic drugs and antibodies conjugated by a linker, designed to deliver a therapeutic payload to cells expressing the target antigen. By delivering the highly cytotoxic agent directly to cancer cells, ADCs are designed to enhance safety and broaden the therapeutic window. Recently, ADCs have demonstrated promising efficacy in various solid tumors and are rapidly expanding their indications. The prognosis of patients with advanced head and neck squamous cell carcinoma (HNSCC) remains poor, with no new therapeutics since the advent of anti-PD-1 antibodies in 2016, highlighting a critical need for innovative therapies. Recent preliminary results suggest that ADCs could be promising treatment options for HNSCC as they explore a variety of target antigens, payloads, and linkers. However, for successful adaptation of ADCs in the treatment of HNSCC, addressing key challenges such as payload toxicities, antigen heterogeneity, and adaptive resistance will be essential. Current research focused on new ADC structures, including multispecific antibodies and noncytotoxic payloads, and diverse combination approaches, show promise for future advancements.

Cancer therapy with antibodies

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

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

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

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

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

Overview of CD70 as a Potential Therapeutic Target for Osteosarcoma

Osteosarcoma is a primary malignant bone tumor. Effective chemotherapy regimens for refractory disease are scarce, accounting for no improvement in survival. Immune-based cell therapies have emerged as novel alternatives. However, advancements with these therapies have been seen mostly when immune cells are armed to target specific tumor Ags. Recent studies identified cluster of differentiation 70 (CD70) as a promising target to osteosarcoma particularly because CD70 is highly expressed in osteosarcoma lung metastases (Pahl et al. 2015. Cancer Cell Int. 15: 31), and its overexpression by tumors has been correlated with immune evasion and tumor proliferation (Yang et al. 2007. Blood 110: 2537-2544). However, the limited knowledge of the overall CD70 expression within normal tissues and the potential for off-target effect pose several challenges (Flieswasser et al. 2022. J. Exp. Clin. Cancer Res. 41: 12). Nonetheless, CD70-based clinical trials are currently ongoing and are preliminarily showing promising results for patients with osteosarcoma. The present review sheds light on the recent literature on CD70 as it relates to osteosarcoma and highlights the benefits and challenges of targeting this pathway.

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.

Antibody-Drug Conjugates: A Review of Approved Drugs and Their Clinical Level of Evidence

Antibody-drug conjugates (ADCs) are an innovative family of agents assembled through linking cytotoxic drugs (payloads) covalently to monoclonal antibodies (mAbs) to be delivered to tumor tissue that express their particular antigen, with the theoretical advantage of an augmented therapeutic ratio. As of June 2023, eleven ADCs have been approved by the Food and Drug Administration (FDA) and are on the market. These drugs have been added to the therapeutic armamentarium of acute myeloblastic and lymphoblastic leukemias, various types of lymphoma, breast, gastric or gastroesophageal junction, lung, urothelial, cervical, and ovarian cancers. They have proven to deliver more potent and effective anti-tumor activities than standard practice in a wide variety of indications. In addition to targeting antigen-expressing tumor cells, bystander effects have been engineered to extend cytotoxic killing to low-antigen-expressing or negative tumor cells in the heterogenous tumor milieu. Inevitably, myelosuppression is a common side effect with most of the ADCs due to the effects of the cytotoxic payload. Also, other unique side effects are specific to the tissue antigen that is targeted for, such as the cardiac toxicity with Her-2 targeting ADCs, and the hemorrhagic side effects with the tissue factor (TF) targeting Tisotumab vedotin. Further exciting developments are centered in the strategies to improve the tolerability and efficacy of the ADCs to improve the therapeutic window; as well as the development of novel payloads including (1) peptide-drug conjugates (PDCs), with the peptide replacing the monoclonal antibody, rendering greater tumor penetration; (2) immune-stimulating antibody conjugates (ISACs), which upon conjugation of the antigen, cause an influx of pro-inflammatory cytokines to activate dendritic cells and harness an anti-tumor T-cell response; and (3) the use of radioactive isotopes as a payload to enhance cytotoxic activity.

Antibody-Drug Conjugates for Lung Cancer: Payloads and Progress

Antibody Drug Conjugates (ADCs) are a novel class of therapeutic that structurally comprise an antibody directed at a tumor epitope connected via a linker to a cytotoxic payload that have shown significant antitumor activity across a range of malignancies including lung cancer. In this article we review the pharmacology of ADCs, describe results of trials with ADCs directed at targets in lung cancer including Trophoblast cell-surface antigen 2(TROP2), HER3, MET, Carcinoembryonic antigen-related cell adhesion molecular 5(CECAM-5) and HER2. Trastuzumab Deruxtecan (also known as DS-8201a or T-DXd) an ADC directed at HER2 recently became the first ADC to receive FDA approval in lung cancer, on the basis of its activity in tumors with HER2 mutations, demonstrated in the Destiny-Lung01 and Lung02 trials.

Postulating the possible cellular signalling mechanisms of antibody drug conjugates in Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders in the world. Although the basic pathology of the disease is elucidated, it is difficult to restore or prevent the worsening of neurodegeneration and its symptoms. Antibody and small molecule-based approaches have been studied and are in study individually, but a combined approach like conjugation has not been performed to date. The conjugation between antibodies and drugs which are already used for Alzheimer's treatment or developed specifically for this purpose may have better efficacy and dual action in mitigating Alzheimer's disease. A probable mechanism for antibody-drug conjugates in Alzheimer's disease is discussed in the present review.

Antibody-drug conjugates for lymphoma patients: preclinical and clinical evidences

Antibody-drug conjugates (ADCs) are a recent, revolutionary approach for malignancies treatment, designed to provide superior efficacy and specific targeting of tumor cells, compared to systemic cytotoxic chemotherapy. Their structure combines highly potent anti-cancer drugs (payloads or warheads) and monoclonal antibodies (Abs), specific for a tumor-associated antigen, via a chemical linker. Because the sensitive targeting capabilities of monoclonal Abs allow the direct delivery of cytotoxic payloads to tumor cells, these agents leave healthy cells unharmed, reducing toxicity. Different ADCs have been approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of a wide range of malignant conditions, both as monotherapy and in combination with chemotherapy, including for lymphoma patients. Over 100 ADCs are under preclinical and clinical investigation worldwide. This paper it provides an overview of approved and promising ADCs in clinical development for the treatment of lymphoma. Each component of the ADC design, their mechanism of action, and the highlights of their clinical development progress are discussed.

Antibody drug conjugate: the "biological missile" for targeted cancer therapy

Antibody-drug conjugate (ADC) is typically composed of a monoclonal antibody (mAbs) covalently attached to a cytotoxic drug via a chemical linker. It combines both the advantages of highly specific targeting ability and highly potent killing effect to achieve accurate and efficient elimination of cancer cells, which has become one of the hotspots for the research and development of anticancer drugs. Since the first ADC, Mylotarg® (gemtuzumab ozogamicin), was approved in 2000 by the US Food and Drug Administration (FDA), there have been 14 ADCs received market approval so far worldwide. Moreover, over 100 ADC candidates have been investigated in clinical stages at present. This kind of new anti-cancer drugs, known as "biological missiles", is leading a new era of targeted cancer therapy. Herein, we conducted a review of the history and general mechanism of action of ADCs, and then briefly discussed the molecular aspects of key components of ADCs and the mechanisms by which these key factors influence the activities of ADCs. Moreover, we also reviewed the approved ADCs and other promising candidates in phase-3 clinical trials and discuss the current challenges and future perspectives for the development of next generations, which provide insights for the research and development of novel cancer therapeutics using ADCs.

Antibody-Drug Conjugate Targets, Drugs and Linkers

Antibody-drug conjugates offer the possibility of directing powerful cytotoxic agents to a malignant tumor while sparing normal tissue. The challenge is to select an antibody target expressed exclusively or at highly elevated levels on the surface of tumor cells and either not all or at low levels on normal cells. The current review explores 78 targets that have been explored as antibody-drug conjugate targets. Some of these targets have been abandoned, 9 or more are the targets of FDA-approved drugs, and most remain active clinical interest. Antibody-drug conjugates require potent cytotoxic drug payloads, several of these small molecules are discussed, as are the linkers between the protein component and small molecule components of the conjugates. Finally, conclusions regarding the elements for the successful antibody-drug conjugate are discussed.

Peptibody Based on FGFR1-Binding Peptides From the FGF4 Sequence as a Cancer-Targeting Agent

Targeted therapies are a promising alternative to conventional chemotherapy, with an increasing number of therapeutics targeting specific molecular aberrancies in cancer cells. One of the emerging targets for directed cancer treatments is fibroblast growth factor receptors (FGFRs), which are known to be involved in the pathogenesis and progression of multiple cancer types, specially in lung, bladder, and breast cancers. Here, we are demonstrating the development of the FGFR1-targeting agent based on the interactome screening approach, based on the isolation of binding regions from ligands interacting with the receptor. The parallel analysis by FGFR1 pull-down of chymotryptic peptides coupled with MS analysis, and PepSpot analysis yielded equivalent peptide sequences from FGF4, one of the FGFR1 ligands. Three sequences served as a basis for peptibody (Fc-fusion) generation, to overcome clinical limitations of peptidic agents, and two of them showed favorable FGFR1-binding in vitro and FGFR1-dependent internalization into cells. To validate if developed FGFR1-targeting peptibodies can be used for drug delivery, similar to the well-established concept of antibody-drug conjugates (ADCs), peptibodyF4_1 was successfully conjugated with monomethylauristatin E (MMAE), and has shown significant and specific toxicity toward FGFR1-expressing lung cancer cell lines, with nanomolar EC50 values. Essentially, the development of new effective FGFR1 binders that comprise the naturally occurring FGFR-recognition peptides and Fc region ensuring high plasma stability, and long bloodstream circulation is an interesting strategy expanding targeted anticancer agents' portfolio. Furthermore, identifying peptides effectively binding the receptor from sequences of its ligands is not limited to FGFRs and is an approach versatile enough to be a basis for a new peptide/peptibodies development strategy.

CD70 antibody-drug conjugate: A potential novel therapeutic agent for ovarian cancer

This study aimed to investigate the cytotoxicity of a cluster of differentiation 70 antibody-drug conjugate (CD70-ADC) against ovarian cancer in in vitro and in vivo xenograft models. CD70 expression was assessed in clinical samples by immunohistochemical analysis. Western blotting and fluorescence-activated cell sorting analyses were used to determine CD70 expression in the ovarian cancer cell lines A2780 and SKOV3, and in the cisplatin-resistant ovarian cancer cell lines A2780cisR and SKOV3cisR. CD70 expression after cisplatin exposure was determined in A2780 cells transfected with mock- or nuclear factor (NF)-κB-p65-small interfering RNA. We developed an ADC with an anti-CD70 monoclonal antibody linked to monomethyl auristatin F and investigated its cytotoxic effect. We examined 63 ovarian cancer clinical samples; 43 (68.3%) of them expressed CD70. Among patients with advanced stage disease (n = 50), those who received neoadjuvant chemotherapy were more likely to exhibit high CD70 expression compared to those who did not (55.6% [15/27] vs 17.4% [4/23], P < .01). CD70 expression was confirmed in A2780cisR, SKOV3, and SKOV3cisR cells. Notably, CD70 expression was induced after cisplatin treatment in A2780 mock cells but not in A2780-NF-κB-p65-silenced cells. CD70-ADC was cytotoxic to A2780cisR, SKOV3, and SKOV3cisR cells, with IC₅₀ values ranging from 0.104 to 0.341 nmol/L. In A2780cisR and SKOV3cisR xenograft models, tumor growth in CD70-ADC treated mice was significantly inhibited compared to that in the control-ADC treated mice (A2780cisR: 32.0 vs 1639.0 mm³ , P < .01; SKOV3cisR: 232.2 vs 584.9 mm³ , P < .01). Platinum treatment induced CD70 expression in ovarian cancer cells. CD70-ADC may have potential therapeutic implications in the treatment of CD70 expressing ovarian cancer.

Depleting Tumor Cells Expressing Immune Checkpoint Ligands-A New Approach to Combat Cancer

Antibodies against inhibitory immune checkpoint molecules (ICPMs), referred to as immune checkpoint inhibitors (ICIs), have gained a prominent place in cancer therapy. Several ICIs in clinical use have been engineered to be devoid of effector functions because of the fear that ICIs with preserved effector functions could deplete immune cells, thereby curtailing antitumor immune responses. ICPM ligands (ICPMLs), however, are often overexpressed on a sizeable fraction of tumor cells of many tumor types and these tumor cells display an aggressive phenotype with changes typical of tumor cells undergoing an epithelial-mesenchymal transition. Moreover, immune cells expressing ICPMLs are often endowed with immunosuppressive or immune-deviated functionalities. Taken together, these observations suggest that compounds with the potential of depleting cells expressing ICPMLs may become useful tools for tumor therapy. In this article, we summarize the current state of the art of these compounds, including avelumab, which is the only ICI targeting an ICPML with preserved effector functions that has gained approval so far. We also discuss approaches allowing to obtain compounds with enhanced tumor cell-depleting potential compared to native antibodies. Eventually, we propose treatment protocols that may be applied in order to optimize the therapeutic efficacy of compounds that deplete cells expressing ICPMLs.

CD70 antibody-drug conjugate as a potential therapeutic agent for uterine leiomyosarcoma

BACKGROUND

Uterine leiomyosarcoma is a rare and aggressive gynecologic malignancy originating in the myometrium of the uterine corpus that tends to recur even after complete surgical excision. Current therapeutic agents have only modest effects on uterine leiomyosarcoma. Although antibodies and antibody-drug conjugates have been recognized as useful targeted therapies for other cancers, no study has yet evaluated the effects of this approach on uterine leiomyosarcoma.

OBJECTIVE

This study aimed to examine the activity of tumoral CD70 in uterine leiomyosarcoma and assess the antitumor activity of CD70-antibody-drug conjugate treatment in uterine leiomyosarcoma.

STUDY DESIGN

Target membrane proteins were screened by profiling and comparing membrane protein expression in 3 uterine leiomyosarcoma cell lines (SK-UT-1, SK-LMS-1, and SKN) and normal uterine myometrium cells using the isobaric tags for relative and absolute quantitation labeling method. Western blotting, fluorescence-activated cell sorting analyses, and immunohistochemistry were used to examine CD70 expression in the membrane proteins in uterine leiomyosarcoma cell lines and clinical samples. We developed an antibody-drug conjugate with a monoclonal antibody of the target membrane protein linked to monomethyl auristatin F and investigated its antitumor effects against uterine leiomyosarcoma (in vitro, in vivo, and in patient-derived xenograft models).

RESULTS

CD70 was identified as a specific antigen highly expressed in uterine leiomyosarcoma cell lines. Of the 3 uterine leiomyosarcoma cell lines, CD70 expression was confirmed in SK-LMS-1 cells by western blotting and fluorescence-activated cell sorting analysis. CD70 overexpression was observed in 19 of 21 (90.5%) tumor specimens from women with uterine leiomyosarcoma. To generate CD70-antibody-drug conjugate, anti-CD70 monoclonal antibody was conjugated with a novel derivative of monomethyl auristatin F. CD70-antibody-drug conjugate showed significant antitumor effects on SK-LMS-1 cells (half maximal inhibitory concentration, 0.120 nM) and no antitumor effects on CD70-negative uterine leiomyosarcoma cells. CD70-antibody-drug conjugate significantly inhibited tumor growth in the SK-LMS-1 xenograft mouse model (tumor volume, 129.8 vs 285.5 mm³; relative reduction, 54.5%; P<.001) and patient-derived xenograft mouse model (tumor volume, 128.1 vs 837.7 mm³; relative reduction, 84.7%; P<.001).

CONCLUSION

Uterine leiomyosarcoma tumors highly express CD70 and targeted therapy with CD70-antibody-drug conjugate may have a potential therapeutic implication in the treatment of uterine leiomyosarcoma.

Novel Auristatins with High Bystander and Cytotoxic Activities in Drug Efflux-positive Tumor Models

Auristatins, a class of clinically validated anti-tubulin agents utilized as payloads in antibody-drug conjugates, are generally classified by their membrane permeability and the extent of cytotoxic bystander activity on neighboring cells after targeted delivery. The drugs typically fall within two categories: membrane permeable monomethyl auristatin E-type molecules with high bystander activities and susceptibility to efflux pumps, or charged and less permeable monomethyl auristatin F (MMAF) analogs with low bystander activities and resistance to efflux pumps. Herein, we report the development of novel auristatins that combine the attributes of each class by having both bystander activity and cytotoxicity on multidrug-resistant (MDR⁺) cell lines. Structure-based design focused on the hydrophobic functionalization of the N-terminal N-methylvaline of the MMAF scaffold to increase cell permeability. The resulting structure-activity relationships of the new auristatins demonstrate that optimization of hydrophobicity and structure can lead to highly active free drugs and antibody-drug conjugates with in vivo bystander activities.

FGF2-Derived PeptibodyF2-MMAE Conjugate for Targeted Delivery of Cytotoxic Drugs into Cancer Cells Overexpressing FGFR1

Fibroblast growth factor receptors (FGFRs) are emerging targets for directed cancer therapy. Presented here is a new FGFR1-targeting conjugate, the peptibodyF2, which employs peptibody, a fusion of peptide and the Fc fragment of human IgG as a selective targeting agent and drug carrier. Short peptide based on FGF2 sequence was used to construct a FGFR1-targeting peptibody. We have shown that this peptide ensures specific delivery of peptibodyF2 into FGFR1-expressing cells. In order to use peptibodyF2 as a delivery vehicle for cytotoxic drugs, we have conjugated it with MMAE, a drug widely used in antibody-drug conjugates for targeted therapy. Resulting conjugate shows high and specific cytotoxicity towards FGFR1-positive cells, i.e., squamous cell lung carcinoma NCI-H520, while remaining non-toxic for FGFR1-negative cells. Such peptibody-drug conjugate can serve as a basis for development of therapy for tumors with overexpressed or malfunctioning FGFRs.

Antibody-Drug Conjugates: The New Frontier of Chemotherapy

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

An overview on anti-tubulin agents for the treatment of lymphoma patients

Anti-tubulin agents constitute a large class of compounds with broad activity both in solid tumors and hematologic malignancies, due to the interference with microtubule dynamics. Since microtubules play crucial roles in the regulation of the mitotic spindles, the interference with their function usually leads to a block in cell division with arrest at the metaphase/anaphase junction of mitosis, followed to apoptosis. This explains the reason why tubulin-binding agents (TBAs) proved to be extremely active in patients with cancer. Several anti-tubulin agents are indicated in the treatment of patients with lymphomas both alone and in combination chemotherapy regimens. The article reviews the literature on classic and more recent anti-tubulin agents, providing an insight into their mechanisms of action and their use in the treatment of lymphoma.

Anti-glypican-1 antibody-drug conjugate is a potential therapy against pancreatic cancer

Background

Pancreatic cancer (PDAC) is the most lethal malignancy. New treatment options for it are urgently required. The aim was to develop an antibody–drug conjugate (ADC) targeting glypican-1 (GPC-1) as a new therapy for PDAC.

Methods

We evaluated GPC-1 expression in resected PDAC specimens and PDAC cell lines. We then measured the antitumour effect of anti-GPC-1 monoclonal antibody conjugated with the cytotoxic agent monomethyl auristatin F (MMAF) in vitro and in vivo.

Results

GPC-1 was overexpressed in most primary PDAC cells and tissues. The PDAC cell lines BxPC-3 and T3M-4 strongly expressed GPC-1 relative to SUIT-2 cells. Compared with control ADC, GPC-1-ADC showed a potent antitumour effect against BxPC-3 and T3M-4, but little activity against SUIT-2 cells. In the xenograft and patient-derived tumour models, GPC-1-ADC significantly and potently inhibited tumour growth in a dose-dependent manner. GPC-1-ADC-mediated G2/M-phase cell cycle arrest was detected in the tumour tissues of GPC-1-ADC-treated mice relative to those of control-ADC-treated mice.

Conclusions

GPC-1-ADC showed significant tumour growth inhibition against GPC-1-positive pancreatic cell lines and patient-derived, GPC-1-positive pancreatic cancer tissues. Our preclinical data demonstrated that targeting GPC-1 with ADC is a promising therapy for patients with GPC-1-positive pancreatic cancer.

Prospects of biological and synthetic pharmacotherapies for glioblastoma

Introduction: The field of neuro-oncology has experienced significant advances in recent years. More is known now about the molecular and genetic characteristics of glioma than ever before. This knowledge leads to the understanding of glioma biology and pathogenesis, guiding the development of targeted therapeutics and clinical trials. The goal of this review is to describe the state of basic, translational, and clinical research as it pertains to biological and synthetic pharmacotherapy for gliomas.Areas covered: Challenges remain in designing accurate preclinical models and identifying patients that are likely to respond to a particular targeted therapy. Preclinical models for therapeutic assessment are critical to identify the most promising treatment approaches.Expert opinion: Despite promising new therapeutics, there have been no significant breakthroughs in glioma treatment and patient outcomes. Thus, there is an urgent need to better understand the mechanisms of treatment resistance and to design effective clinical trials.

The role of antibody delivery formation in cancer therapy

Cancer has become one of the major threats to human survival. Because of antibodies specificity and low toxicity, it is the primary choice to diagnose and treat cancer. It is easy to be cleared from the blood circulation or distributing throughout the body and causes unnecessary side effects. It is necessary to delivery antibodies to the tumour region in a stable, safe and effective manner. In this review, we discuss the latest studies that aimed to delivery antibodies to tumour sites via several vector forms, such as liposomes, carbon nanomaterials, and gold nanomaterials. How to deliver antibodies to the target site is a difficulty for antibody therapy. This review summarises the antibody's therapeutic forms and carrier materials in recent years, and to explore how antibodies can be safely and stably delivered to the target site.

Responsive Antibody Conjugates Enable Quantitative Determination of Intracellular Bond Degradation Rate

Degradable crosslinkers that respond to intracellular biological stimuli are a critical component of many drug delivery systems. With numerous stimuli-responsive drug delivery systems in development, it is important to quantitatively study their intracellular processing. Herein we report a framework for quantifying the rate of intracellular bond degradation in the endocytic pathway. Toward this end, we devised and synthesized a reduction-sensitive FRET-based crosslinker that can be readily conjugated to a variety of targeting ligands. This crosslinker was conjugated to trastuzumab, a humanized monoclonal antibody against the HER2 receptor. We developed a model based on mass-action kinetics to describe the intracellular processing of this conjugate. The kinetic model was developed in conjunction with live-cell experiments to extract the rate constant for intracellular disulfide bond degradation. This framework may be applied to other endocytosis pathways, bond types, and cell types to quantify this fundamental degradation rate parameter.

An anti-CD103 antibody-drug conjugate prolongs the survival of pancreatic islet allografts in mice

CD103 mediates T-cell infiltration and organ allograft rejection, and depletion of CD103-expressing cells is a promising therapeutic strategy for allograft intolerance. Recently, we verified that M290-MC-MMAF, an anti-CD103 antibody-drug conjugate, potently eliminates CD103-positive cells in vivo, with high specificity and minimal toxicity. However, the contribution of M290-MC-MMAF to blocking the CD103/E-cadherin pathway involved in transplant rejection remains unclear. Herein, we examined the impact of systemic administration of M290-MC-MMAF on allografts in an islet transplantation model. M290-MC-MMAF treatment maintained the long-term survival of islet allografts (>60 days) compared to mock injection or unconjugated M290 antibody treatment (<18 days). The change was associated with a decrease in CD103⁺CD8⁺ effector T cells and an increase in CD4⁺CD25⁺ regulatory T cells. CD103⁺CD8⁺ effector T-cell transfer or CD4⁺CD25⁺ regulatory T-cell depletion resulted in a rapid loss of allografts in long-surviving islet hosts. Moreover, M290-MC-MMAF treatment reduced IL-4, IL-6, and TNF-α expression levels and increased IL-10 expression in the grafts, which presented an immunosuppressive cytokine profile. In conclusion, targeting CD103 with M290-MC-MMAF induced immunosuppression and prolonged the survival of pancreatic islet allografts in mice, indicating the potential clinical value of M290-MC-MMAF in therapeutic interventions for allograft rejection.

Convergent synthesis of hydrophilic monomethyl dolastatin 10 based drug linkers for antibody-drug conjugation

We report a modular approach to synthesize maleimido group containing hydrophilic dolastatin 10 (Dol10) derivatives as drug-linkers for the syntheses of antibody-drug conjugates (ADCs). Discrete polyethylene glycol (PEG) moieties of different chain lengths were introduced as part of the linker to impart hydrophilicity to these drug linkers. The synthesis process involved construction of PEG maleimido derivatives of the tetrapeptide intermediate (N-methylvaline-valine-dolaisoleucine-dolaproine), which were subsequently coupled with dolaphenine to generate the desired drug linkers. The synthetic method reported in this manuscript circumvents the use of highly cytotoxic Dol10 in its native form. By using trastuzumab (Herceptin®) as the antibody we have synthesized Dol10 containing ADCs. The presence of a discrete PEG chain in the drug linkers resulted in ADCs free from aggregation. The effect of PEG chain length on the biological activities of these Dol10 containing ADCs was investigated by in vitro cytotoxicity assays. ADCs containing PEG₆ and PEG₈ spacers exhibited the highest level of in vitro anti-proliferative activity against HER2-positive (SK-BR-3) human tumor cells. ADCs derived from Herceptin® and PEG₈-Dol10, at a dose of 10 mg kg^-1, effectively delayed the tumor growth and prolonged the survival time in mice bearing human ovarian SKOV-3 xenografts.

Antibody-Drug Conjugate that Exhibits Synergistic Cytotoxicity with an Endosome-Disruptive Peptide

Antibody-drug conjugates are an important class of cancer therapeutics. These agents generally bind a specific cell surface receptor, undergo receptor-mediated endocytosis, and enter the endosomal-lysosomal system, where the environment in these organelles facilitates the release of a membrane-permeable cytotoxin. By using a membrane-impermeable cytotoxin, we describe here a method that allows the cytotoxicity of an antibody conjugate to be triggered by co-administration with an endosome-disruptive peptide that exhibits low toxicity. This approach was validated by conjugation of an anionic derivative of the tubulin-binding cytotoxin colchinol methyl ether to lysine residues of the HER2-targeting antibody trastuzumab (Herceptin) via a disulfide. When this antibody binds HER2 on SKBR3 breast cancer cells and undergoes endocytosis, the membrane-impermeable cytotoxin is released, but it becomes trapped in endosomes, resulting in relatively low cytotoxicity (IC50 > 1 μM). However, co-administration with an essentially nontoxic (IC50 > 10 μM) cholesterol-linked endosome-disruptive peptide promotes the release of this small molecule into the cytoplasm, conferring subnanomolar cytotoxic potency (IC50 = 0.11 ± 0.07 nM). Studies of a structurally related fluorophore conjugate revealed that the endosome-disruptive peptide does not substantially enhance cleavage of the disulfide (t 1/2 = 8 ± 2 h) within endosomes, suggesting that the mechanism of endosomal escape involves the efflux of some small molecules without facilitating substantial influx of reduced glutathione.

Mouse Strains Influence Clearance and Efficacy of Antibody and Antibody-Drug Conjugate Via Fc-FcγR Interaction

To provide a better understanding of the pharmacokinetics-pharmacodynamics relationships of antibody-based drugs, we analyzed several chimeric and humanized monoclonal antibodies or antibody-drug conjugates (ADC) for PK and efficacy among four strains of mice. Notably, antibodies and ADCs displayed a dose-dependent drug disposition profile in the plasma of NSG mice. The increased clearance rate in NSG mice resulted in the reduction of antitumor activity of ADCs. Furthermore, we identified that the abnormal clearance was mediated by Fc-FcγR interaction by comparing antibodies that lack FcγR binding capacity. We also found a high percentage of FcγR-expressing macrophages in the bone marrow, spleen, and liver of NSG mice, which may be responsible for the abnormal distribution of antibodies. Overall, these findings suggest that preclinical evaluation of efficacy and pharmacokinetics of antibodies and ADCs need to consider mouse strain-induced variations.

Hypoxia-inducible factor-2 alpha up-regulates CD70 under hypoxia and enhances anchorage-independent growth and aggressiveness in cancer cells

Hypoxia-inducible factors (HIFs) facilitate cellular adaptation to environmental stress such as low oxygen conditions (hypoxia) and consequently promote tumor growth. While HIF-1α functions in cancer progression have been increasingly recognized, the contribution of HIF-2α remains widely unclear despite accumulating reports showing its overexpression in cancer cells. Here, we report that HIF-2α up-regulates the expression of CD70, a cancer-related surface antigen that improves anchorage-independent growth in cancer cells and is associated with poor clinical prognosis, which can be induced via epigenetic modifications mediated by DNMT1. The ablation of CD70 by RNAi led to decreased colony forming efficiency in soft agar. Most strikingly, we identified the emergence of CD70-expressing cells derived from CD70-negative cell lines upon prolonged hypoxia exposure or DNMT1 inhibition, both of which significantly reduced CpG-nucleotide methylations within CD70 promoter region. Interestingly, DNMT1 expression was decreased under hypoxia, which was rescued by HIF-2α knockdown. In addition, the expression of CD70 and colony forming efficiency in soft agar were decreased by knockdown of HIF-2α. These findings indicate that CD70 expression and an aggressive phenotype of cancer cells is driven under hypoxic conditions and mediated by HIF-2α functions and epigenetic modifications. This provides additional insights into the role of HIF-2α in coordinated regulation of stem-like functions and epigenetics that are important for cancer progression and may present additional targets for the development of novel combinatorial therapeutics.

Practical Considerations, Challenges, and Limitations of Bioconjugation via Azide-Alkyne Cycloaddition

Interrogating biological systems is often limited by access to biological probes. The emergence of "click chemistry" has revolutionized bioconjugate chemistry by providing facile reaction conditions amenable to both biologic molecules and small molecule probes such as fluorophores, toxins, or therapeutics. One particularly popular version is the copper-catalyzed azide-alkyne cycloaddition (AAC) reaction, which has spawned new alternatives such as the strain-promoted azide-alkyne cycloaddition reaction, among others. This focused review highlights practical approaches to AAC reactions for the synthesis of peptide or protein bioconjugates and contrasts current challenges and limitations in light of recent advances in the field. The conical success of antibody drug conjugates has expanded the toolbox of linkers and payloads to facilitate practical applications of bioconjugation to create novel therapeutics and biologic probes. The AAC reaction in particular is poised to enable a large set of functionalized molecules as a combinatorial approach to high-throughput bioconjugate generation, screening, and honing of lead compounds.

Anti-glypican-1 antibody-drug conjugate exhibits potent preclinical antitumor activity against glypican-1 positive uterine cervical cancer

Glypican-1 (GPC1) is highly expressed in solid tumors, especially squamous cell carcinomas (SCCs), and is thought to be associated with disease progression. We explored the use of a GPC1-targeted antibody-drug conjugate (ADC) as a novel treatment for uterine cervical cancer. On immunohistochemical staining, high expression levels of GPC1 were detected in about 50% of uterine cervical cancer tissues and also in a tumor that had relapsed after chemoradiotherapy. Novel anti-GPC1 monoclonal antibodies were developed, and clone 01a033 was selected as the best antibody for targeted delivery of the cytotoxic agent monomethyl auristatin F (MMAF) into GPC1-positive cells. The anti-GPC1 antibody was conjugated with MMAF. On flow cytometry, HeLa and ME180 cervical cancer cells highly expressed GPC1, however, RMG-I ovarian clear cell cancer cell line showed weak expression. The GPC1-ADC was rapidly internalized into GPC1-expressing cells in vitro and was potently cytotoxic to cancer cells highly expressing GPC1. There were no inhibitory effects on cancer cells with low expression of GPC1. In a murine xenograft model, GPC1-ADC also had significant and potent tumor growth inhibition. GPC1-ADC-mediated G2/M phase cell cycle arrest was detected, indicating that the dominant antitumor effect in vivo was MMAF-mediated. The toxicity of GPC-ADC was tolerable within the therapeutic dose range in mice. Our data showed that GPC1-ADC has potential as a promising therapy for uterine cervical cancer.

Intracellular trafficking of new anticancer therapeutics: antibody-drug conjugates

Antibody-drug conjugate (ADC) is a milestone in targeted cancer therapy that comprises of monoclonal antibodies chemically linked to cytotoxic drugs. Internalization of ADC takes place via clathrin-mediated endocytosis, caveolae-mediated endocytosis, and pinocytosis. Conjugation strategies, endocytosis and intracellular trafficking optimization, linkers, and drugs chemistry present a great challenge for researchers to eradicate tumor cells successfully. This inventiveness of endocytosis and intracellular trafficking has given considerable momentum recently to develop specific antibodies and ADCs to treat cancer cells. It is significantly advantageous to emphasize the endocytosis and intracellular trafficking pathways efficiently and to design potent engineered conjugates and biological entities to boost efficient therapies enormously for cancer treatment. Current studies illustrate endocytosis and intracellular trafficking of ADC, protein, and linker strategies in unloading and also concisely evaluate practically applicable ADCs.

Targeted alpha therapy using a novel CD70 targeted thorium-227 conjugate in in vitro and in vivo models of renal cell carcinoma

The cell surface receptor CD70 has been previously reported as a promising target for B-cell lymphomas and several solid cancers including renal cell carcinoma. We describe herein the characterization and efficacy of a novel CD70 targeted thorium-227 conjugate (CD70-TTC) comprising the combination of the three components, a CD70 targeting antibody, a chelator moiety and the short-range, high-energy alpha-emitting radionuclide thorium-227 (²²⁷Th). In vitro analysis demonstrated that the CD70-TTC retained binding affinity to its target and displayed potent and specific cytotoxicity compared to an isotype control-TTC. A biodistribution study in subcutaneous tumor-bearing nude mice using the human renal cell carcinoma cell line 786-O demonstrated significant uptake and retention with 122 ± 42% of the injected dose of ²²⁷Th per gram (% ID/g) remaining in the tumor seven days post dose administration compared to only 3% ID/g for the isotype control-TTC. Tumor accumulation correlated with a dose dependent and statistically significant inhibition in tumor growth compared to vehicle and isotype control-TTC groups at radioactivity doses as low as 50 kBq/kg. The CD70-TTC was well tolerated as evidenced by only modest changes in hematology and normal gain in body weight of the mice. To our knowledge, this is the first report describing molecular targeting of CD70 expressing tumors using a targeted alpha-therapy (TAT).

Wide application of a novel topoisomerase I inhibitor-based drug conjugation technology

To establish a novel and widely applicable payload-linker technology for antibody-drug conjugates (ADCs), we have focused our research on applying exatecan mesylate (DX-8951f), a potent topoisomerase I inhibitor, which exhibits extensive antitumor activity as well as significant myelotoxicity, as the payload part. Through this study, we discovered a promising exatecan derivative (DX-8951 derivative, DXd), that has the characteristics of low membrane permeability and shows considerably less myelotoxicity than that shown by exatecan mesylate in an in vitro human colony forming unit-granulocyte macrophage assay. DXd was further used for drug conjugation by using commercially or clinically useful monoclonal antibodies to evaluate the potency of the ADC. The result revealed that the DXd-ADCs targeting CD30, CD33, and CD70 were effective against each of their respective target-expressing tumor cell lines. Moreover, a novel DXd-ADC targeting B7-H3, which is a new target for ADCs, also showed potent antitumor efficacy both in vitro and in vivo. In conclusion, this study showed that this novel topoisomerase I inhibitor-based ADC technology is widely applicable to a diverse number of antibodies and is expected to mitigate myelotoxicity, thereby possibly resulting in better safety profiles than that of existing ADC technologies.

Effective antitumor therapy based on a novel antibody-drug conjugate targeting the Tn carbohydrate antigen

Antibody-drug conjugates (ADC), combining the specificity of tumor recognition by monoclonal antibodies (mAb) and the powerful cytotoxicity of anticancer drugs, are currently under growing interest and development. Here, we studied the potential of Chi-Tn, a mAb directed to a glyco-peptidic tumor-associated antigen, to be used as an ADC for cancer treatment. First, we demonstrated that Chi-Tn specifically targeted tumor cells in vivo. Also, using flow cytometry and deconvolution microscopy, we showed that the Chi-Tn mAb is rapidly internalized - condition necessary to ensure the delivery of conjugated cytotoxic drugs in an active form, and targeted to early and recycling endosomes. When conjugated to saporin (SAP) or to auristatin F, the Chi-Tn ADC exhibited effective cytotoxicity to Tn-positive tumor cells in vitro, which correlated with the level of tumoral Tn expression. Furthermore, the Chi-Tn mAb conjugated to auristatin F also exhibited efficient antitumor activity in vivo, validating for the first time the use of an anti-Tn antibody as an effective ADC.

Linkers Having a Crucial Role in Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) comprised of a desirable monoclonal antibody, an active cytotoxic drug and an appropriate linker are considered to be an innovative therapeutic approach for targeted treatment of various types of tumors and cancers, enhancing the therapeutic parameter of the cytotoxic drug and reducing the possibility of systemic cytotoxicity. An appropriate linker between the antibody and the cytotoxic drug provides a specific bridge, and thus helps the antibody to selectively deliver the cytotoxic drug to tumor cells and accurately releases the cytotoxic drug at tumor sites. In addition to conjugation, the linkers maintain ADCs' stability during the preparation and storage stages of the ADCs and during the systemic circulation period. The design of linkers for ADCs is a challenge in terms of extracellular stability and intracellular release, and intracellular circumstances, such as the acid environment, the reducing environment and cathepsin, are considered as the catalysts to activate the triggers for initiating the cleavage of ADCs. This review discusses the linkers used in the clinical and marketing stages for ADCs and details the fracture modes of the linkers for the further development of ADCs.

Ocular Adverse Events Associated with Antibody-Drug Conjugates in Human Clinical Trials

This article reviews ocular adverse events (AEs) reported in association with administration of antibody-drug conjugates (ADCs) in human clinical trials. References reporting ocular toxicity or AEs associated with ADCs were collected using online publication searches. Articles, abstracts, or citations were included if they cited ocular toxicities or vision-impairing AEs with a confirmed or suspected association with ADC administration. Twenty-two references were found citing ocular or vision-impairing AEs in association with ADC administration. All references reported use of ADCs in human clinical trials for treatment of various malignancies. The molecular target and cytotoxic agent varied depending on the ADC used. Ocular AEs affected a diversity of ocular tissues. The most commonly reported AEs involved the ocular surface and included blurred vision, dry eye, and corneal abnormalities (including microcystic corneal disease). Most ocular AEs were not severe (≤ grade 2) or dose limiting. Clinical outcomes were not consistently reported, but when specified, most AEs improved or resolved with cessation of treatment or with ameliorative therapy. A diverse range of ocular AEs are reported in association with administration of ADCs for the treatment of cancer. The toxicologic mechanism(s) and pathogenesis of such events are not well understood, but most are mild in severity and reversible. Drug development and medical professionals should be aware of the clinical features of these events to facilitate early recognition and intervention in the assessment of preclinical development programs and in human clinical trials.

Strategies and Advancement in Antibody-Drug Conjugate Optimization for Targeted Cancer Therapeutics

Antibody-drug conjugates utilize the antibody as a delivery vehicle for highly potent cytotoxic molecules with specificity for tumor-associated antigens for cancer therapy. Critical parameters that govern successful antibody-drug conjugate development for clinical use include the selection of the tumor target antigen, the antibody against the target, the cytotoxic molecule, the linker bridging the cytotoxic molecule and the antibody, and the conjugation chemistry used for the attachment of the cytotoxic molecule to the antibody. Advancements in these core antibody-drug conjugate technology are reflected by recent approval of Adectris(®) (anti-CD30-drug conjugate) and Kadcyla(®) (anti-HER2 drug conjugate). The potential approval of an anti-CD22 conjugate and promising new clinical data for anti-CD19 and anti-CD33 conjugates are additional advancements. Enrichment of antibody-drug conjugates with newly developed potent cytotoxic molecules and linkers are also in the pipeline for various tumor targets. However, the complexity of antibody-drug conjugate components, conjugation methods, and off-target toxicities still pose challenges for the strategic design of antibody-drug conjugates to achieve their fullest therapeutic potential. This review will discuss the emergence of clinical antibody-drug conjugates, current trends in optimization strategies, and recent study results for antibody-drug conjugates that have incorporated the latest optimization strategies. Future challenges and perspectives toward making antibody-drug conjugates more amendable for broader disease indications are also discussed.

Receptor Crosslinking: A General Method to Trigger Internalization and Lysosomal Targeting of Therapeutic Receptor:Ligand Complexes

A major unmet clinical need is a universal method for subcellular targeting of bioactive molecules to lysosomes. Delivery to this organelle enables either degradation of oncogenic receptors that are overexpressed in cancers, or release of prodrugs from antibody–drug conjugates. Here, we describe a general method that uses receptor crosslinking to trigger endocytosis and subsequently redirect trafficking of receptor:cargo complexes from their expected route, to lysosomes. By incubation of plasma membrane receptors with biotinylated cargo and subsequent addition of streptavidin to crosslink receptor:cargo–biotin complexes, we achieved rapid and selective lysosomal targeting of transferrin, an anti-MHC class I antibody, and the clinically approved anti-Her2 antibody trastuzumab. These three protein ligands each target a receptor with a distinct cellular function and intracellular trafficking profile. Importantly, we confirmed that crosslinking of trastuzumab increased lysosomal degradation of its cognate oncogenic receptor Her2 in breast cancer cell lines SKBR3 and BT474. These data suggest that crosslinking could be exploited for a wide range of target receptors, for navigating therapeutics through the endolysosomal pathway, for significant therapeutic benefit.