Immunoregulation by IL-7R-targeting antibody-drug conjugates: overcoming steroid-resistance in cancer and autoimmune disease

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

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

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is a haematological malignancy characterized by the uncontrolled proliferation of immature lymphoid cells. Over past decades, significant progress has been made in understanding the biology of ALL, resulting in remarkable improvements in its diagnosis, treatment and monitoring. Since the advent of chemotherapy, ALL has been the platform to test for innovative approaches applicable to cancer in general. For example, the advent of omics medicine has led to a deeper understanding of the molecular and genetic features that underpin ALL. Innovations in genomic profiling techniques have identified specific genetic alterations and mutations that drive ALL, inspiring new therapies. Targeted agents, such as tyrosine kinase inhibitors and immunotherapies, have shown promising results in subgroups of patients while minimizing adverse effects. Furthermore, the development of chimeric antigen receptor T cell therapy represents a breakthrough in ALL treatment, resulting in remarkable responses and potential long-term remissions. Advances are not limited to treatment modalities alone. Measurable residual disease monitoring and ex vivo drug response profiling screening have provided earlier detection of disease relapse and identification of exceptional responders, enabling clinicians to adjust treatment strategies for individual patients. Decades of supportive and prophylactic care have improved the management of treatment-related complications, enhancing the quality of life for patients with ALL.

Identification and validation of regulatory T cell-associated gene signatures to predict colon adenocarcinoma prognosis

Colon adenocarcinoma (COAD) is a common cause of cancer-related death. Due to the difficulty in early diagnosis and drug resistance, conventional treatments are difficult to be effective. Some studies have found that the functional recovery of T cells in the tumor microenvironment, especially regulatory T cells (Tregs), plays an important role in the progression of cancer. This study used the TCGA data set, clinical information and RNA-seq data of COAD patients to construct a Tregs-related risk score (TRS) through methods such as WGCNA, single-factor Cox, multi-factor Cox and random survival forest (RSF). Moreover, we also used the TCGA test set and internal validation set to verify the predictive ability of TRS, and used functional enrichment analysis and somatic mutation analysis to mine genes related to TRS, such as like thrombin/trypsin receptor 2 (F2RL2), inhibin subunit beta B (INHBB) and melanoma antigen family A12 (MAGEA12). Moreover, this study confirmed the expression of these prognostic genes using scRNA-seq data. We also performed qPCR analysis of various genes in normal and cancerous colon cancer cell lines to verify that these genes indeed play a role in CODA patients. We also constructed a mouse CODA model to study and evaluate the impact of key genes such as MAGEA12 on tumor growth in mice. This study explores the important role of Treg cells in the prognosis of COAD and discovers some potential biomarkers for the occurrence and development of COAD, which provides some new ideas for the treatment of COAD.

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

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

The Therapeutic Values of IL-7/IL-7R and the Recombinant Derivatives in Glioma: A Narrative Review

Interleukin-7 (IL-7) is essential for maintaining the immune system's defense functions by regulating the development and homeostasis of lymphocytes. Findings have shown the high efficacy of IL-7/IL-7 receptor (IL-7R)-based immunotherapy on various malignancies, with confirmation in both animal models and humans. In recent years, the progression-free survival and overall survival of patients suffering from gliomas significantly increased by introducing C7R-expressing chimeric antigen receptor (CAR)-T cells and long-acting IL-7 agonists such as NT-I7 (rhIL-7-hyFc, Efineptakin alfa). However, the effect of IL-7-based immunotherapies on the resistance of tumor cells to chemotherapy (when used simultaneously with chemotherapy agents) is still ambiguous and requires further studies. This article first reviews the pathophysiological roles of IL-7/IL-7R in tumors, focusing on gliomas. Subsequently, it discusses the therapeutic values of IL-7/IL-7R and the recombinant derivatives in gliomas.

Payload diversification: a key step in the development of antibody-drug conjugates

Antibody-drug conjugates (ADCs) is a fast moving class of targeted biotherapeutics that currently combines the selectivity of monoclonal antibodies with the potency of a payload consisting of cytotoxic agents. For many years microtubule targeting and DNA-intercalating agents were at the forefront of ADC development. The recent approval and clinical success of trastuzumab deruxtecan (Enhertu^®) and sacituzumab govitecan (Trodelvy^®), two topoisomerase 1 inhibitor-based ADCs, has shown the potential of conjugating unconventional payloads with differentiated mechanisms of action. Among future developments in the ADC field, payload diversification is expected to play a key role as illustrated by a growing number of preclinical and clinical stage unconventional payload-conjugated ADCs. This review presents a comprehensive overview of validated, forgotten and newly developed payloads with different mechanisms of action.

The Role of IL-7 and IL-7R in Cancer Pathophysiology and Immunotherapy

Interleukin-7 (IL-7) is a multipotent cytokine that maintains the homeostasis of the immune system. IL-7 plays a vital role in T-cell development, proliferation, and differentiation, as well as in B cell maturation through the activation of the IL-7 receptor (IL-7R). IL-7 is closely associated with tumor development and has been used in cancer clinical research and therapy. In this review, we first summarize the roles of IL-7 and IL-7Rα and their downstream signaling pathways in immunity and cancer. Furthermore, we summarize and discuss the recent advances in the use of IL-7 and IL-7Rα as cancer immunotherapy tools and highlight their potential for therapeutic applications. This review will help in the development of cancer immunotherapy regimens based on IL-7 and IL-7Rα, and will also advance their exploitation as more effective and safe immunotherapy tools.

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

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

Identification of new IL-7Rα small-molecule agonists: a multi-computational approach

Interleukin 7 (IL-7) is an essential cytokine that acts as a potent growth factor of T-cells and supports the growth of B-cell precursors. IL-7 binds to a heterodimeric receptor consisting of an IL-7 receptor alpha (IL-7Rα) and the common gamma chain receptor (γc) which is shared with IL-2, IL-4, IL-9, IL-15 and IL-21. The discovery of small-molecule agonists of cytokines would be of great pharmaceutical interest with the increasing scientific rationale. In this study, a series of molecular modelling methods, including field-based pharmacophore virtual screening, protein-protein docking and molecular dynamics simulations, led to the identification of two compounds (i.e. 1 and 2) of different classes that exhibit enhanced agonistic effects by activating the IL-7 signalling cascade. One of these compounds was selected as a hit and represents the first small-molecule agonist of IL-7Rα with single-digit micromolar activity. Moreover, the prediction model of the active compound to the IL-7Rα/γc interaction complex provides insight into the binding of a small-molecule agonist to its receptor.

Antibody-Drug Conjugates for the Treatment of Acute Pediatric Leukemia

The clinical development of antibody-drug conjugates (ADCs) has gained momentum in recent years and these agents are gradually moving into frontline regimens for pediatric acute leukemias. ADCs consist of a monoclonal antibody attached to a cytotoxic payload by a cleavable linker. This structure allows for highly cytotoxic agents to be directly delivered to leukemia cells leading to cell death and avoids excessive off-tumor toxicity. Near universal expression on B-cell acute lymphoblastic leukemia (ALL) blasts and the ability of rapid internalization has rendered CD22 an ideal target for ADC in B-ALL. Inotuzumab ozogamicin, the anti-CD22 antibody linked to calicheamicin led to complete remission rates of 60-80% in patients with relapsed/refractory B-ALL. In acute myeloid leukemia (AML), the CD33 targeting gemtuzumab ozogamicin has demonstrated modest improvements in survival and is the only ADC currently licensed in the United States for pediatric patients with de novo AML. Several other ADCs have been developed and tested clinically for leukemia but have achieved limited success to date. The search for additional leukemia-specific targets and optimization of ADC structure and specificity are ongoing efforts to improve their therapeutic window. This review provides a comprehensive overview of ADCs in acute leukemias, with a focus on pediatric ALL and AML.

Deregulation of the Interleukin-7 Signaling Pathway in Lymphoid Malignancies

The cytokine interleukin-7 (IL-7) and its receptor are critical for lymphoid cell development. The loss of IL-7 signaling causes severe combined immunodeficiency, whereas gain-of-function alterations in the pathway contribute to malignant transformation of lymphocytes. Binding of IL-7 to the IL-7 receptor results in the activation of the JAK-STAT, PI3K-AKT and Ras-MAPK pathways, each contributing to survival, cell cycle progression, proliferation and differentiation. Here, we discuss the role of deregulated IL-7 signaling in lymphoid malignancies of B- and T-cell origin. Especially in T-cell leukemia, more specifically in T-cell acute lymphoblastic leukemia and T-cell prolymphocytic leukemia, a high frequency of mutations in components of the IL-7 signaling pathway are found, including alterations in IL7R, IL2RG, JAK1, JAK3, STAT5B, PTPN2, PTPRC and DNM2 genes.

Characterization of the robust humoral immune response to GSK2618960, a humanized anti-IL-7 receptor monoclonal antibody, observed in healthy subjects in a Phase 1 study

Interleukin-7 (IL-7) signaling modulates T cell activity and is implicated in numerous autoimmune diseases. An anti-IL-7 receptor monoclonal antibody (GSK2618960) biotherapeutic was evaluated in healthy subjects for safety, pharmacokinetics (PK), pharmacodynamics (PD) and immunogenicity in a single-dose escalation phase I study. We found that antibodies against GSK2618960 (i.e., anti-drug antibodies or ADA) developed in 83% and 100% of GSK2618960-treated subjects in the 0.6 and 2.0 mg/kg dose cohorts, respectively. Of the ADA positive subjects, 64% (7 of 11) had detectable neutralizing activity. Further investigation revealed the presence of GSK2618960-specific memory B cells, indicating the development of immunological memory for the ADAs. Ex vivo stimulation of peripheral blood mononuclear cell (PBMC) samples demonstrated a relatively strong CD4⁺ T cell proliferation response to GSK2618960 as compared to the control anti-RSV antibody (which is known to have only low immunogenic potential), confirming the high immunogenic potential of GSK2618960. Furthermore, GSK2618960 was found to bind in vitro monocyte-derived dendritic cells (DCs). GSK2618960 treatment of PBMCs increased the proportion of DC cells showing an increase in expression of CD83, CD86 and CD209, which indicated enhanced DC differentiation and activation relative to the isotype control anti-β amyloid antibody. Collectively, the evidence supports that the high incidence of observed clinical immunogenicity was likely related to the receptor-mediated activity by GSK2618960.

Facts and Challenges in Immunotherapy for T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL), a T-cell malignant disease that mainly affects children, is still a medical challenge, especially for refractory patients for whom therapeutic options are scarce. Recent advances in immunotherapy for B-cell malignancies based on increasingly efficacious monoclonal antibodies (mAbs) and chimeric antigen receptors (CARs) have been encouraging for non-responding or relapsing patients suffering from other aggressive cancers like T-ALL. However, secondary life-threatening T-cell immunodeficiency due to shared expression of targeted antigens by healthy and malignant T cells is a main drawback of mAb—or CAR-based immunotherapies for T-ALL and other T-cell malignancies. This review provides a comprehensive update on the different immunotherapeutic strategies that are being currently applied to T-ALL. We highlight recent progress on the identification of new potential targets showing promising preclinical results and discuss current challenges and opportunities for developing novel safe and efficacious immunotherapies for T-ALL.

Modulation of Signaling Mediated by TSLP and IL-7 in Inflammation, Autoimmune Diseases, and Cancer

Thymic Stromal Lymphopoietin (TSLP) and Interleukin-7 (IL-7) are widely studied cytokines within distinct branches of immunology. On one hand, TSLP is crucially important for mediating type 2 immunity at barrier surfaces and has been linked to widespread allergic and inflammatory diseases of the airways, skin, and gut. On the other hand, IL-7 operates at the foundations of T-cell and innate lymphoid cell (ILC) development and homeostasis and has been associated with cancer. Yet, TSLP and IL-7 are united by key commonalities in their structure and the structural basis of the receptor assemblies they mediate to initiate cellular signaling, in particular their cross-utilization of IL-7Rα. As therapeutic targeting of TSLP and IL-7 via diverse approaches is reaching advanced stages and in light of the plethora of mechanistic and structural data on receptor signaling mediated by the two cytokines, the time is ripe to provide integrated views of such knowledge. Here, we first discuss the major pathophysiological roles of TSLP and IL-7 in autoimmune diseases, inflammation and cancer. Subsequently, we curate structural and mechanistic knowledge about receptor assemblies mediated by the two cytokines. Finally, we review therapeutic avenues targeting TSLP and IL-7 signaling. We envision that such integrated view of the mechanism, structure, and modulation of signaling assemblies mediated by TSLP and IL-7 will enhance and fine-tune the development of more effective and selective approaches to further interrogate the role of TSLP and IL-7 in physiology and disease.

IL-7R is essential for leukemia-initiating cell activity of T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy resulting from the dysregulation of signaling pathways that control intrathymic T-cell development. Relapse rates are still significant, and prognosis is particularly bleak for relapsed patients. Therefore, development of novel therapies specifically targeting pathways controlling leukemia-initiating cell (LIC) activity is mandatory for fighting refractory T-ALL. The interleukin-7 receptor (IL-7R) is a crucial T-cell developmental pathway that is commonly expressed in T-ALL and has been implicated in leukemia progression; however, the significance of IL-7R/IL-7 signaling in T-ALL pathogenesis and its contribution to disease relapse remain unknown. To directly explore whether IL-7R targeting may be therapeutically efficient against T-ALL relapse, we focused on a known Notch1-induced T-ALL model, because a majority of T-ALL patients harbor activating mutations in NOTCH1, which is a transcriptional regulator of IL-7R expression. Using loss-of-function approaches, we show that Il7r-deficient, but not wild-type, mouse hematopoietic progenitors transduced with constitutively active Notch1 failed to generate leukemia upon transplantation into immunodeficient mice, thus providing formal evidence that IL-7R function is essential for Notch1-induced T-cell leukemogenesis. Moreover, we demonstrate that IL-7R expression is an early functional biomarker of T-ALL cells with LIC potential and report that impaired IL-7R signaling hampers engraftment and progression of patient-derived T-ALL xenografts. Notably, we show that IL-7R-dependent LIC activity and leukemia progression can be extended to human B-cell acute lymphoblastic leukemia (B-ALL). These results have important therapeutic implications, highlighting the relevance that targeting normal IL-7R signaling may have in future therapeutic interventions, particularly for preventing T-ALL (and B-ALL) relapse.

Antibody Conjugates-Recent Advances and Future Innovations

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

New advances in targeting aberrant signaling pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disorder characterized by malignant transformation of immature progenitors primed towards T-cell development. Over the past 15 years, advances in the molecular characterization of T-ALL have uncovered oncogenic key drivers and crucial signaling pathways of this disease, opening new chances for the development of novel therapeutic strategies. Currently, T-ALL patients are still treated with aggressive therapies, consisting of high dose multiagent chemotherapy. To minimize and overcome the unfavorable effects of these regimens, it is critical to identify innovative targets and test selective inhibitors of such targets. Major efforts are being made to develop small molecules against deregulated signaling pathways, which sustain T-ALL cell growth, survival, metabolism, and drug-resistance. This review will focus on recent improvements in the understanding of the signaling pathways involved in the pathogenesis of T-ALL and on the challenging opportunities for T-ALL targeted therapies.

Antibody therapeutics and immunoregulation in cancer and autoimmune disease

Cancer and autoimmune disease are closely related, and many therapeutic antibodies are widely used in clinics for the treatment of both diseases. Among them, the anti-CD20 antibody has proven to be effective against both lymphoid malignancy and autoimmune disease. Moreover, immune checkpoint blockade using the anti-PD1/PD-L1/CTLA4 antibody has improved the prognosis of patients with refractory solid tumors. At the same time, however, over-enhancement of immunoreaction can induce autoimmune reaction. Although anti-TNF antibody therapies represent a breakthrough in the treatment of autoimmune diseases, optimal management is required to control the serious associated issues, including development and progression of cancer, and it is becoming more and more important to control the immunoreaction. In addition, next-generation antibody therapeutics such as antibody-drug conjugates and bispecific antibodies, are anticipated to treat uncontrolled cancer and autoimmune disease. IL-7R signaling plays an important role in the development and progression of both lymphoid malignancy and autoimmune disease. In addition, abnormal homing activity and steroid resistance caused by IL-7R signaling may worsen prognosis. Therefore, anti-IL-7R targeting antibody therapies that enable suppression of such pathophysiological status have the potential to be beneficial for the treatment of both diseases. In this review, we discuss current antibody therapeutics in cancer and autoimmune disease, and describe a new therapeutic strategy for immunoregulation including IL-7R targeting antibodies.

A fully human anti-IL-7Rα antibody promotes antitumor activity against T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological cancer for which treatment options often result in incomplete therapeutic efficacy and long-term side-effects. Interleukin 7 (IL-7) and its receptor IL-7Rα promote T-ALL development and mutational activation of IL-7Rα associates with very high risk in relapsed disease. Using combinatorial phage-display libraries and antibody reformatting, we generated a fully human IgG1 monoclonal antibody (named B12) against both wild-type and mutant human IL-7Rα, predicted to form a stable complex with IL-7Rα at a different site from IL-7. B12 impairs IL-7/IL-7R-mediated signaling, sensitizes T-ALL cells to treatment with dexamethasone and can induce cell death per se. The antibody also promotes antibody-dependent natural killer-mediated leukemia cytotoxicity in vitro and delays T-cell leukemia development in vivo, reducing tumor burden and promoting mouse survival. B12 is rapidly internalized and traffics to the lysosome, rendering it an attractive vehicle for targeted intracellular delivery of cytotoxic cargo. Consequently, we engineered a B12–MMAE antibody–drug conjugate and provide proof-of-concept evidence that it has increased leukemia cell killing abilities as compared with the naked antibody. Our studies serve as a stepping stone for the development of novel targeted therapies in T-ALL and other diseases where IL-7Rα has a pathological role.

IL-7R-mediated signaling in T-cell acute lymphoblastic leukemia: An update

Interleukin 7 (IL-7) and its receptor (IL-7R, a heterodimer of IL-7Rα and γc) are essential for normal lymphoid development. In their absence, severe combined immunodeficiency occurs. By contrast, excessive IL-7/IL-7R-mediated signaling can drive lymphoid leukemia development, disease acceleration and resistance to chemotherapy. IL-7 and IL-7R activate three main pathways: STAT5, PI3K/Akt/mTOR and MEK/Erk, ultimately leading to the promotion of leukemia cell viability, cell cycle progression and growth. However, the contribution of each of these pathways towards particular functional outcomes is still not completely known and appears to differ between normal and malignant states. For example, IL-7 upregulates Bcl-2 in a PI3K/Akt/mTOR-dependent and STAT5-independent manner in T-ALL cells. This is a 'symmetric image' of what apparently happens in normal lymphoid cells, where PI3K/Akt/mTOR does not impact on Bcl-2 and regulates proliferation rather than survival. In this review, we provide an updated summary of the knowledge on IL-7/IL-7R-mediated signaling in the context of cancer, focusing mainly on T-cell acute lymphoblastic leukemia, where this axis has been more extensively studied.

Electricity-driven 7α-hydroxylation of a steroid catalyzed by a cytochrome P450 monooxygenase in engineered yeast

Schematic diagram of the cytochrome P450 monooxygenase-catalyzed BES.

Engineering Platforms for T Cell Modulation

T cells are crucial contributors to mounting an effective immune response and increasingly the focus of therapeutic interventions in cancer, infectious disease, and autoimmunity. Translation of current T cell immunotherapies has been hindered by off-target toxicities, limited efficacy, biological variability, and high costs. As T cell therapeutics continue to develop, the application of engineering concepts to control their delivery and presentation will be critical for their success. Here, we outline the engineer's toolbox and contextualize it with the biology of T cells. We focus on the design principles of T cell modulation platforms regarding size, shape, material, and ligand choice. Furthermore, we review how application of these design principles has already impacted T cell immunotherapies and our understanding of T cell biology. Recent, salient examples from protein engineering, synthetic particles, cellular and genetic engineering, and scaffolds and surfaces are provided to reinforce the importance of design considerations. Our aim is to provide a guide for immunologists, engineers, clinicians, and the pharmaceutical sector for the design of T cell-targeting platforms.

Development of Antibody-Drug Conjugates Using DDS and Molecular Imaging

Antibody-drug conjugate (ADC), as a next generation of antibody therapeutics, is a combination of an antibody and a drug connected via a specialized linker. ADC has four action steps: systemic circulation, the enhanced permeability and retention (EPR) effect, penetration within the tumor tissue, and action on cells, such as through drug delivery system (DDS) drugs. An antibody with a size of about 10 nm has the same capacity for passive targeting as some DDS carriers, depending on the EPR effect. In addition, some antibodies are capable of active targeting. A linker is stable in the bloodstream but should release drugs efficiently in the tumor cells or their microenvironment. Thus, the linker technology is actually a typical controlled release technology in DDS. Here, we focused on molecular imaging. Fluorescent and positron emission tomography (PET) imaging is useful for the visualization and evaluation of antibody delivery in terms of passive and active targeting in the systemic circulation and in tumors. To evaluate the controlled release of the ADC in the targeted area, a mass spectrometry imaging (MSI) with a mass microscope, to visualize the drug released from ADC, was used. As a result, we succeeded in confirming the significant anti-tumor activity of anti-fibrin, or anti-tissue factor-ADC, in preclinical settings by using DDS and molecular imaging.