Targeted Delivery of Tumor Necrosis Factor-α to Tumor Vessels Induces a Therapeutic T Cell–Mediated Immune Response that Protects the Host Against Syngeneic Tumors of Different Histologic Origin

Comparative transcriptome profile reveals insight into the antibacterial immunity mechanism of the loach (Misgurnus anguillicaudatus) fed with soybean fermented broth during lipopolysaccharide (LPS) exposure

Loach (Misgurnus anguillicaudatus) is a common freshwater commercial fish species in China. The meat of this fish is a good source of protein and other nutrients that are needed for human health. Aquaculture challenges such as diseases and pest susceptibility, excessive density, and nutritional deficiency result in low production of loach rather than increased demand. Due to a lack of knowledge about the immune system of loaches, we carried out this study to better understand its antibacterial molecular mechanism. Here, we performed RNA sequencing from liver tissue obtained from soya bean-fermented fed loach after subjecting it to the LPS challenge. The results revealed a total of 18,399 differentially expressed genes (DEGs) in the LPS-treated and control groups. There were 7482 DEGs that were upregulated and 10,917 DEGs were downregulated. The enrichment analysis of DEGs revealed that the majority of DEGs were found to be abundant in the pathways of DNA replication, spliceosome, nucleotide exception repair, cell cycle, and Herpes simplex virus 1 infection. Furthermore, qRT-PCR analysis of 21 selected DEGs demonstrated that the transcriptomic data is extremely reliable. Overall, this study provides insight into the molecular features and control mechanisms of genes that affect loach growth. The availability of this information will also contribute to the enhancement of the breeding and protection of loach resources.

Therapeutic antibodies for precise cancer immunotherapy: current and future perspectives

Antibodies, as one of the most important components of host adaptive immune system, play an important role in defense of infectious disease, immune surveillance, and autoimmune disease. Due to the development of recombinant antibody technology, antibody therapeutics become the largest and rapidly expanding drug to provide major health benefits to patients, especially for the treatment of cancer patients. Many antibody-based therapeutic strategies have been developed including monoclonal antibodies, antibody-drug conjugates, bispecific and trispecific antibodies and pro-antibodies with promising results from both clinical and pre-clinical trials. However, the response rate and side-effect still vary between patients with undefined mechanisms. Here, we summarized the current and future perspectives of antibody-based cancer immunotherapeutic strategies for designing next-generation drugs.

The use of supercytokines, immunocytokines, engager cytokines, and other synthetic cytokines in immunotherapy

Cytokines exert powerful immunomodulatory effects that are critical to physiology and pathology in humans. The application of natural cytokines in clinical studies has not been clearly established, and there are often problems associated with toxicity or lack of efficacy. The key reasons can be attributed to the pleiotropy of cytokine receptors and undesired activation of off-target cells. With a deeper understanding of the structural principles and functional signals of cytokine-receptor interactions, artificial modification of cytokine signaling through protein engineering and synthetic immunology has become an increasingly feasible and powerful approach. Engineered cytokines are designed to selectively target cells. Herein, the theoretical and experimental evidence of cytokine engineering is reviewed, and the "supercytokines" resulting from structural enhancement and the "immunocytokines" generated by antibody fusion are described. Finally, the "engager cytokines" formed by the crosslinking of cytokines and bispecific immune engagers and other synthetic cytokines formed by nonnatural analogs are also discussed.

Engineered Bifunctional Proteins for Targeted Cancer Therapy: Prospects and Challenges

Bifunctional proteins (BFPs) are a class of therapeutic agents produced through genetic engineering and protein engineering, and are increasingly used to treat various human diseases, including cancer. These proteins usually have two or more biological functions-specifically recognizing different molecular targets to regulate the related signaling pathways, or mediating effector molecules/cells to kill tumor cells. Unlike conventional small-molecule or single-target drugs, BFPs possess stronger biological activity but lower systemic toxicity. Hence, BFPs are considered to offer many benefits for the treatment of heterogeneous tumors. In this review, the authors briefly describe the unique structural feature of BFP molecules and innovatively divide them into bispecific antibodies, cytokine-based BFPs (immunocytokines), and protein toxin-based BFPs (immunotoxins) according to their mode of action. In addition, the latest advances in the development of BFPs are discussed and the potential limitations or problems in clinical applications are outlined. Taken together, future studies need to be centered on understanding the characteristics of BFPs for optimizing and designing more effective such drugs.

The immunocytokine L19-TNF eradicates sarcomas in combination with chemotherapy agents or with immune check-point inhibitors

Antibody-cytokine fusion proteins (also called 'immunocytokines') represent an emerging class of biopharmaceutical products, which are being considered for cancer immunotherapy. When used as single agents, pro-inflammatory immunocytokines are rarely capable of inducing complete and durable cancer regression in mouse models and in patients. However, the combination treatment with conventional chemotherapy or with other immune-stimulatory agents typically increases the therapeutic efficacy of immunocytokines. In this article, we describe combination treatments of a tumor-targeting antibody-cytokine fusion protein based on the L19 antibody (specific to a splice isoform of fibronectin) fused to murine tumor necrosis factor with standard chemotherapy (dacarbazine, trabectedin or melphalan) or with an immune check-point inhibitor (anti-PD-1) in a BALB/c derived immunocompetent murine model of sarcoma (WEHI-164). All combination treatments led to improved tumor remission compared to single-agent treatments, suggesting that these combination partners may be suitable for further clinical development in sarcoma patients.

Dose escalation and expansion phase I studies with the tumour-targeting antibody-tumour necrosis factor fusion protein L19TNF plus doxorubicin in patients with advanced tumours, including sarcomas

BACKGROUND

L19TNF is a recombinant fusion protein composed of a human antibody fragment and human tumour necrosis factor. L19TNF targets the EDB domain of oncofetal fibronectin highly expressed in tumour vasculature and induces tumour remission in mouse tumours. We summarise two phase I trials testing a combination of L19TNF with doxorubicin in patients with solid tumours, particularly soft tissue sarcomas (STS).

PATIENTS AND METHODS

The first study, an open-label, dose-escalation and expansion phase I study of L19TNF plus doxorubicin, enrolled 27 patients. Three cohorts (10.4-17 μg/kg L19TNF) of patients received L19TNF intravenously at days 1, 3, and 5 and doxorubicin (75 mg/m², then 60 mg/m²) on day 1 every 3 weeks. The expansion cohort enrolled patients with STS. The second study tried to re-escalate the doxorubicin dose to 75 mg/m² with 13 μg/kg L19TNF. Among primary objectives was the establishment of a recommended dose (RD).

RESULTS

The combination was safely applicable. Dose-limiting toxicity occurred either at 17 μg/kg L19TNF or at 75 mg/m² doxorubicin. RD is 13 μg/kg L19TNF plus 60 mg/m² doxorubicin. In 15 STS patients of the extension cohort evaluable for efficacy, antitumour activity was observed with complete remission in 1, partial remission in 1 and minor tumour shrinkage in 7 patients. The median overall survival for this heavily pretreated cohort was 14.9 months.

CONCLUSION

L19TNF can be safely applied in combination with doxorubicin and induces encouraging tumour remissions in patients with soft tissue sarcomas.

Tumor Vasculature Targeted TNFα Therapy: Reversion of Microenvironment Anergy and Enhancement of the Anti-tumor Efficiency

Tumor cells and tumor-associated stromal cells such as immune, endothelial and mesenchimal cells create a Tumor Microenvironment (TME) which allows tumor cell promotion, growth and dissemination while dampening the anti-tumor immune response. Efficient anti-tumor interventions have to keep into consideration the complexity of the TME and take advantage of immunotherapy and chemotherapy combined approaches. Thus, the aim of tumor therapy is to directly hit tumor cells and reverse endothelial and immune cell anergy. Selective targeting of tumor vasculature using TNFα-associated peptides or antibody fragments in association with chemotherapeutic agents, has been shown to exert a potent stimulatory effect on endothelial cells as well as on innate and adaptive immune responses. These drug combinations reducing the dose of single agents employed have led to minimize the associated side effects. In this review, we will analyze different TNFα-mediated tumor vesseltargeted therapies in both humans and tumor mouse models, with emphasis on the role played by the cross-talk between natural killer and dendritic cells and on the ability of TNFα to trigger tumor vessel activation and normalization. The improvement of the TNFα-based therapy with anti-angiogenic immunomodulatory drugs that may convert the TME from immunosuppressive to immunostimulant, will be discussed as well.

A phase II study of the L19IL2 immunocytokine in combination with dacarbazine in advanced metastatic melanoma patients

Engineered cytokine products represent promising agents for the treatment of immunogenic tumors, such as malignant melanoma, in addition to immune checkpoint inhibitors. Here we describe the results of a controlled, randomized phase II clinical trial, aimed at assessing the therapeutic potential of L19IL2, a fully human fusion protein consisting of the L19 antibody specific to the alternatively spliced extra-domain B of fibronectin, fused to human interleukin-2 in advanced metastatic melanoma. In one arm, patients received dacarbazine (DTIC; 1000 mg/m² of body surface on day 1 of 21-day cycles) as single agent, while in two other arms L19IL2 (22.5 million international units of IL2 equivalents) was added, based on two different schedules of administration. In total, 69 patients with stage IV melanoma were enrolled (24 in the dacarbazine arm, 23 and 22 in the other combination arms, respectively) and 67 received treatment. Analyses of efficacy results show a statistically significant benefit in terms of overall response rate and median progression-free survival for patients receiving L19IL2 in combination with DTIC, compared to DTIC as single agent. In light of these results, further clinical investigations with L19IL2 (alone or in combination with other agents) are warranted.

Antibody-cytokine fusion proteins: A novel class of biopharmaceuticals for the therapy of cancer and of chronic inflammation

Antibody-cytokine fusion proteins represent a novel class of biopharmaceuticals, with the potential to increase the therapeutic index of cytokine 'payloads' and to promote leukocyte infiltration at the site of disease. In this review, we present a survey of immunocytokines that have been used in preclinical models of cancer and in clinical trials. In particular, we highlight how antibody format, choice of target antigen and cytokine engineering, as well as combination strategies, may have a profound impact on therapeutic performance. Moreover, by using anti-inflammatory cytokines, antibody fusion strategies can conveniently be employed for the treatment of auto-immune and chronic inflammatory conditions.

Antibody-cytokine fusion proteins: Biopharmaceuticals with immunomodulatory properties for cancer therapy

Cytokines have long been used for therapeutic applications in cancer patients. Substantial side effects and unfavorable pharmacokinetics limit their application and may prevent dose escalation to therapeutically active regimens. Antibody-cytokine fusion proteins (often referred to as immunocytokines) may help localize immunomodulatory cytokine payloads to the tumor, thereby activating anticancer immune responses. A variety of formats (e.g., intact IgGs or antibody fragments), molecular targets (e.g., extracellular matrix components and cell membrane antigens) and cytokine payloads have been considered for the development of this novel class of biopharmaceuticals. This review presents the basic concepts on the design and engineering of immunocytokines, reviews their potential limitations, points out emerging opportunities and summarizes key features of preclinical and clinical-stage products.

Anti-cancer Therapies Employing IL-2 Cytokine Tumor Targeting: Contribution of Innate, Adaptive and Immunosuppressive Cells in the Anti-tumor Efficacy

Antibody-cytokine fusion proteins (immunocytokine) exert a potent anti-cancer effect; indeed, they target the immunosuppressive tumor microenvironment (TME) due to a specific anti-tumor antibody linked to immune activating cytokines. Once bound to the target tumor, the interleukin-2 (IL-2) immunocytokines composed of either full antibody or single chain Fv conjugated to IL-2 can promote the in situ recruitment and activation of natural killer (NK) cells and cytotoxic CD8⁺ T lymphocytes (CTL). This recruitment induces a TME switch toward a classical T helper 1 (Th1) anti-tumor immune response, supported by the cross-talk between NK and dendritic cells (DC). Furthermore, some IL-2 immunocytokines have been largely shown to trigger tumor cell killing by antibody dependent cellular cytotoxicity (ADCC), through Fcγ receptors engagement. The modulation of the TME can be also achieved with immunocytokines conjugated with a mutated form of IL-2 that impairs regulatory T (Treg) cell proliferation and activity. Preclinical animal models and more recently phase I/II clinical trials have shown that IL-2 immunocytokines can avoid the severe toxicities of the systemic administration of high doses of soluble IL-2 maintaining the potent anti-tumor effect of this cytokine. Also, very promising results have been reported using IL-2 immunocytokines delivered in combination with other immunocytokines, chemo-, radio-, anti-angiogenic therapies, and blockade of immune checkpoints. Here, we summarize and discuss the most relevant reported studies with a focus on: (a) the effects of IL-2 immunocytokines on innate and adaptive anti-tumor immune cell responses as well as immunosuppressive Treg cells and (b) the approaches to circumvent IL-2-mediated severe toxic side effects.

Bone tumors developed in patients with juvenile inflammatory arthritis after anti-TNFα therapy

Administration of anti-TNFα agents has become a mainstay in the treatment of chronic inflammatory arthritis such as rheumatoid arthritis (RA) and spondyloarthritis. Adverse events, including infections and allergic reactions, have been reported. Malignancies are rare but potentially life threatening. The existence of bone tumor in those patients is very rare, only five cases of bone tumors were mentioned in juvenile idiopathic arthritis (JIA) in the literature. We describe three patients in whom bone neoplasms developed after years of anti-TNFα therapy for JIA or juvenile ankylosing spondylitis (JAS). One patient developed chondroblastoma, and the other two were diagnosed with osteosarcoma. Rheumatologists should increase their awareness of bone neoplasia in JIA or juvenile ankylosing spondylitis patients after anti-TNFα treatment.

Strategy to targeting the immune resistance and novel therapy in colorectal cancer

Assessing the CRC subtypes that can predict the outcome of colorectal cancer (CRC) in patients with immunogenicity seems to be a promising strategy to develop new drugs that target the antitumoral immune response. In particular, the disinhibition of the antitumoral T‐cell response by immune checkpoint blockade has shown remarkable therapeutic promise for patients with mismatch repair (MMR) deficient CRC. In this review, the authors provide the update of the molecular features and immunogenicity of CRC, discuss the role of possible predictive biomarkers, illustrate the modern immunotherapeutic approaches, and introduce the most relevant ongoing preclinical study and clinical trials such as the use of the combination therapy with immunotherapy. Furthermore, this work is further to understand the complex interactions between the immune surveillance and develop resistance in tumor cells. As expected, if the promise of these developments is fulfilled, it could develop the effective therapeutic strategies and novel combinations to overcome immune resistance and enhance effector responses, which guide clinicians toward a more “personalized” treatment for advanced CRC patients.

Antibody-based delivery of tumor necrosis factor (L19-TNFα) and interleukin-2 (L19-IL2) to tumor-associated blood vessels has potent immunological and anticancer activity in the syngeneic J558L BALB/c myeloma model

PURPOSE

To analyze the impact of TNFα or IL2 on human lymphocytes in vitro and the anti-tumor and immune-modifying effects of L19-IL2 and L19-TNFα on subcutaneously growing J558L myeloma in immunocompetent mice.

METHODS

PBMCs from three healthy volunteers were incubated with IL2, TNFα, or with IL2 plus addition of TNFα (final 20 h). BALB/c J558L mice with subcutaneous tumors were treated with intravenous L19-TNFα plus L19-IL2, or controls. Tumor growth and intra- and peri-tumoral tissues were analyzed for micro-vessel density, necrosis, immune cell composition, and PD1 or PD-L1 expressing cells.

RESULTS

Exposure of PBMC in vitro to IL2, TNFα, or to IL2 over 3 and 5 days plus TNFα for the final 20 h resulted in an approximately 50 and 75% reduction of the CD25low effector cell/CD25high Treg cell ratio, respectively, compared to medium control. IL2 or TNFα increased the proportion of CD4- CD25low effector lymphocytes while reducing the proportion of CD4+ CD25low Teff cells. In the J558L myeloma model, tumor eradication was observed in 58, 42, 25, and 0% of mice treated with L19-TNFα plus L19-IL2, L19-TNFα, L19-IL2, and PBS, respectively. L19-TNFα/L19-IL2 combination caused tumor necrosis, capillary density doubling, peri-tumoral T cell and PD1+ T cell reduction (- 50%), and an increase in PD-L1+ myeloma cells.

CONCLUSION

IL2, TNFα, or IL2 plus TNFα (final 20 h) increased the proportion of CD4- CD25low effector lymphocytes possibly indicating immune activation. L19-TNFα/L19-IL2 combination therapy eradicated tumors in J558L myeloma BALB/c mice likely via TNFα-induced tumor necrosis and L19-TNFα/L19-IL2-mediated local cellular immune reactions.

A novel vascular-targeting peptide for gastric cancer delivers low-dose TNFα to normalize the blood vessels and improve the anti-cancer efficiency of 5-fluorouracil

Various vascular-targeted agents fused with tumor necrosis factor α (TNFα) have been shown to improve drug absorption into tumor tissues and enhance tumor vascular function. TCP-1 is a peptide selected through in vivo phage library biopanning against a mouse orthotopic colorectal cancer model and is a promising agent for drug delivery. This study further investigated the targeting ability of TCP-1 phage and peptide to blood vessels in an orthotopic gastric cancer model in mice and assessed the synergistic anti-cancer effect of 5-fluorouracil (5-FU) with subnanogram TNFα targeted delivered by TCP-1 peptide. In vivo phage targeting assay and in vivo colocalization analysis were carried out to test the targeting ability of TCP-1 phage/peptide. A targeted therapy for improvement of the therapeutic efficacy of 5-FU and vascular function was performed through administration of TCP-1/TNFα fusion protein in this model. TCP-1 phage exhibited strong homing ability to the orthotopic gastric cancer after phage injection. Immunohistochemical staining suggested that and TCP-1 phage/TCP-1 peptide could colocalize with tumor vascular endothelial cells. TCP-1/TNFα combined with 5-FU was found to synergistically inhibit tumor growth, induce apoptosis and reduce cell proliferation without evident toxicity. Simultaneously, subnanogram TCP-1/TNFα treatment normalized tumor blood vessels. Targeted delivery of low-dose TNFα by TCP-1 peptide can potentially modulate the vascular function of gastric cancer and increase the drug delivery of chemotherapeutic drugs.

Targeted Cancer Therapy Using Fusion Protein of TNFα and Tumor-Associated Fibronectin-Specific Aptide

Tumor necrosis factor-α has shown potent antitumor effects in preclinical and clinical studies. However, severe side effects at less than therapeutic doses have limited its systemic delivery, prompting the need for a new strategy for targeted delivery of the protein to tumors. Here, we report a fusion protein of mouse tumor necrosis factor (TNF)-α (mTNFα) and a cancer-targeting, high-affinity aptide and investigate its therapeutic efficacy in tumor-bearing mice. A fusion protein consisting of mTNFα, a linker, and an aptide specific to extra domain B (EDB) of fibronectin (APT_EDB), designated mTNFα-APT_EDB, was successfully produced by expression in Escherichia coli. mTNFα-APT_EDB retained specificity and affinity for its target, EDB. In mice bearing EDB-overexpressing fibrosarcomas, mTNFα-APT_EDB showed greater efficacy in inhibiting tumor growth than mTNFα alone or mTNFα linked to a nonrelevant aptide, without causing an appreciable loss in body weight. Moreover, in vivo antitumor efficacy was further significantly increased by combination treatment with the chemotherapeutic drug, melphalan, suggesting a synergistic effect attributable to enhanced drug uptake into the tumor as a result of TNFα-mediated enhanced vascular permeability. These results suggest that a fusion protein of mTNFα with a cancer-targeting peptide could be a new anticancer therapeutic option for ensuring potent antitumor efficacy after systemic delivery.

The therapeutic T-cell response induced by tumor delivery of TNF and melphalan is dependent on early triggering of natural killer and dendritic cells

The fusion protein L19mTNF (mouse TNF and human antibody fragment L19 directed to fibronectin extra domain B) selectively targets the tumor vasculature, and in combination with melphalan induces a long-lasting T-cell therapeutic response and immune memory in murine models. Increasing evidence suggests that natural killer (NK) cells act to promote effective T-cell-based antitumor responses. We have analyzed the role of NK cells and dendritic cells (DCs) on two different murine tumor models: WEHI-164 fibrosarcoma and C51 colon carcinoma, in which the combined treatment induces high and low rejection rates, respectively. In vivo NK-cell depletion strongly reduced the rejection of WEHI-164 fibrosarcoma and correlated with a decrease in mature DCs, CD4⁺ , and CD8⁺ T cells in the tumor-draining LNs and mature DCs and CD4⁺ T cells in the tumor 40 h after initiation of the therapy. NK-cell depletion also resulted in the impairment of the stimulatory capability of DCs derived from tumor-draining LNs of WEHI-164-treated mice. Moreover, a significant reduction of M2-type infiltrating macrophages was detected in both tumors undergoing therapy. These results suggest that the efficacy of L19mTNF/melphalan therapy is strongly related to the early activation of NK cells and DCs, which are necessary for an effective T-cell response.

Targeting Fibronectin for Cancer Imaging and Therapy

During cancer progression, the extracellular matrix (ECM) undergoes dramatic changes, which promote cancer cell migration and invasion. In the remodeled tumor ECM, fibronectin (FN) level is upregulated to assist tumor growth, progression, and invasion. FN serves as a central organizer of ECM molecules and mediates the crosstalk between the tumor microenvironment and cancer cells. Its upregulation is correlated with angiogenesis, cancer progression, metastasis, and drug resistance. A number of FN-targeting ligands have been developed for cancer imaging and therapy. Thus far, FN-targeting imaging agents have been tested for nuclear imaging, MRI, and fluorescence imaging, for tumor detection and localization. FN-targeting therapeutics, including nuclear medicine, chemotherapy drugs, cytokines, and photothermal moieties, were also developed in cancer therapy. Because of the prevalence of FN overexpression in cancer, FN targeting imaging agents and therapeutics have the promise of broad applications in the diagnosis, treatment, and image-guided interventions of many types of cancers. This review will summarize current understanding on the role of FN in cancer, discuss the design and development of FN-targeting agents, and highlight the applications of these FN-targeting agents in cancer imaging and therapy.

Fibronectin-targeted drug delivery in cancer

Fibronectin is an extracellular matrix protein with pivotal physiological and pathological functions in development and adulthood. Alternative splicing of the precursor mRNA, produced from the single copy fibronectin gene, occurs at three sites coding for the EDA, EDB and IIICS domains. Fibronectin isoforms comprising the EDA or EDB domains are known as oncofetal forms due to their developmental importance and their re-expression in tumors, contrasting with restricted presence in normal adult tissues. These isoforms are also recognized as important markers of angiogenesis, a crucial physiological process in development and required by tumor cells in cancer progression. Attributed to this feature, EDA and EDB domains have been extensively used for the targeted delivery of cytokines, cytotoxic agents, chemotherapy drugs and radioisotopes to fibronectin-expressing tumors to exert therapeutic effects on primary cancers and metastatic lesions. In addition to drug delivery, the EDA and EDB domains of fibronectin have also been utilized to develop imaging strategies for tumor tissues. Furthermore, EDA and EDB based vaccines seem to be promising for the treatment and prevention of certain cancer types. In this review, we will summarize recent advances in fibronectin EDA and EDB-based therapeutic strategies developed to treat cancer.

Vascular-targeted TNFα improves tumor blood vessel function and enhances antitumor immunity and chemotherapy in colorectal cancer

Delivery and penetration of chemotherapeutic drugs into neoplasm through the tumor vasculature are essential mechanisms to enhance the efficiency of chemotherapy. "Vascular targeting" strategy focuses on promoting the infiltration of chemotherapeutic drugs into neoplastic tissues. In this study, we achieved a targeted therapy by coupling tumor necrosis factor α (TNFα) with TCP-1, a novel vascular-targeting peptide, in an orthotopic colorectal cancer model in mice. High dose of TCP-1-conjugated TNFα (TCP-1/TNFα: 5μg/mouse) displayed potent antitumor activity by inducing apoptosis and reducing microvessel number in tumors than unconjugated TNFα, with no evidence of increased toxicity. In the combined therapy, the antitumor action of 5-fluorouracil (5-FU) was potentiated when the mice were pretreated with a low dose of TNFα (1ng/mouse) and to a greater extent by the same concentration of TCP-1/TNFα. In this regard, TCP-1/TNFα combined with 5-FU synergistically inhibited the tumor growth, induced apoptosis and reduced cell proliferation. More importantly, TCP-1/TNFα normalized the tumor vasculature and facilitated the infiltration of immune cells to neoplasm as well as attenuated the immunosuppressing effects of TNFα in bone marrow and spleen. At the same time, TCP-1/TNFα significantly improved 5-FU absorption into the tumor mass. Taken together, these findings underscore the therapeutic potential of TCP-1 as a drug carrier in cancer therapy. TCP-1 is a novel vascular-targeting peptide and appears to be a promising agent for drug delivery. TCP-1 fused with TNFα holds great promise for colorectal cancer therapy.

The coming of age of engineered multivalent antibodies

The development of monoclonal antibody (mAb) technology has had a profound impact on medicine. The therapeutic use of first-generation mAb achieved considerable success in the treatment of major diseases, including cancer, inflammation, autoimmune, cardiovascular, and infectious diseases. Next-generation antibodies have been engineered to further increase potency, improve the safety profile and acquire non-natural properties, and constitute a thriving area of mAb research and development. Currently, a variety of alternative antibody formats with modified architectures have been generated and are moving fast into the clinic. In fact, the bispecific antibody blinatumomab was the first in its class to be approved by the US Food and Drug Administration (FDA) as recently as December 2014. Here, we outline the fundamental strategies used for designing the next generation of therapeutic antibodies, as well as the most relevant results obtained in preclinical studies and clinical trials.

Orchestration of angiogenesis by immune cells

It is widely accepted that the tumor microenvironment (TUMIC) plays a major role in cancer and is indispensable for tumor progression. The TUMIC involves many "players" going well beyond the malignant-transformed cells, including stromal, immune, and endothelial cells (ECs). The non-malignant cells can acquire tumor-promoting functions during carcinogenesis. In particular, these cells can "orchestrate" the "symphony" of the angiogenic switch, permitting the creation of new blood vessels that allows rapid expansion and progression toward malignancy. Considerable attention within the context of tumor angiogenesis should focus not only on the ECs, representing a fundamental unit, but also on immune cells and on the inflammatory tumor infiltrate. Immune cells infiltrating tumors typically show a tumor-induced polarization associated with attenuation of anti-tumor functions and generation of pro-tumor activities, among these angiogenesis. Here, we propose a scenario suggesting that the angiogenic switch is an immune switch arising from the pro-angiogenic polarization of immune cells. This view links immunity, inflammation, and angiogenesis to tumor progression. Here, we review the data in the literature and seek to identify the "conductors" of this "orchestra." We also suggest that interrupting the immune → inflammation → angiogenesis → tumor progression process can delay or prevent tumor insurgence and malignant disease.

Tumor-targeting properties of novel immunocytokines based on murine IL1β and IL6

There is an increasing biotechnological interest in 'arming' therapeutic antibodies with bioactive payloads. Many antibody-cytokine fusion proteins (immunocytokines) have been described and some of these biopharmaceuticals have progressed to clinical studies. Here, we describe for the first time the expression and in vivo characterization of immunocytokines based on murine IL1β and IL6. These potent pro-inflammatory cytokines were fused at the N-terminus or at the C-terminus of the monoclonal antibodies F8 (specific to the alternatively-spliced extra-domain A domain of fibronectin, a marker of tumor angiogenesis). All immunocytokines retained the binding properties of the parental antibody and were homogenous, when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion chromatography, except for the N-terminal fusion of IL1β which revealed the presence of glycosylated species. When analyzed by quantitative biodistribution analysis using radioiodinated protein preparations, F8 fusions with IL6 revealed a preferential accumulation at the tumor site for both cytokine orientations, whereas IL1β fusions exhibited lower tumor to organ ratios and a slower blood clearance profile. The fusion proteins with the cytokine payload at the C-terminus were studied in therapy experiments in immunocompetent mice bearing F9 tumors. Immunocytokines based on IL1β resulted in 10% body weight loss at a 5-µg dose, whereas IL6-based products caused a 5% body weight loss at a 225-µg dose. Both F8-IL1β and F8-IL6 exhibited a <50% inhibition of tumor growth rate, which was substantially lower than the one previously reported for F8-TNF, a closely related pro-inflammatory immunocytokine. This study indicates that IL6 can be efficiently delivered to the tumor neo-vasculature by fusion with the F8 antibody. While F8-IL6 was not as potent as other F8-based immunocytokines that exhibit similar biodistribution profiles, the fusion protein sheds light on the different roles of pro-inflammatory cytokines in boosting immunity against the tumor.

Antibody-based delivery of IL2 and cytotoxics eradicates tumors in immunocompetent mice

Antibody-drug conjugates are increasingly being used for cancer therapy, but little is known about their ability to promote anticancer immunity, which may lead to long-lasting remissions. We investigated the therapeutic effect of antibody-based pharmacodelivery of cemadotin, a cytotoxic drug, and IL2, a strong proinflammatory cytokine. Using the F8 antibody, which selectively localizes to the tumor neovasculature, combination treatment led to tumor eradication, in a process dependent on CD8(+) T cells and natural killer cells in the C1498 syngeneic mouse model of acute myelogenous leukemia. The clinical combination of antibody-drug conjugates and antibody-cytokine proteins should be facilitated by their orthogonal toxicity profiles.

Boosting the MHC Class II-Restricted Tumor Antigen Presentation to CD4+ T Helper Cells: A Critical Issue for Triggering Protective Immunity and Re-Orienting the Tumor Microenvironment Toward an Anti-Tumor State

Although the existence of an immune response against tumor cells is well documented, the fact that tumors take off in cancer patients indicates that neoplastic cells can circumvent this response. Over the years many investigators have described strategies to rescue the anti-tumor immune response with the aim of creating specific and long-lasting protection against the disease. When exported to human clinical settings, these strategies have revealed in most cases a very limited, if any, positive outcome. We believe that the failure is mostly due to the inadequate triggering of the CD4+ T helper (TH) cell arm of the adaptive immunity, as TH cells are necessary to trigger all the immune effector mechanisms required to eliminate tumor cells. In this review, we focus on novel strategies that by stimulating MHC class II-restricted activation of TH cells generate a specific and persistent adaptive immunity against the tumor. This point is of critical importance for both preventive and therapeutic anti-tumor vaccination protocols, because adaptive immunity with its capacity to produce specific, long-lasting protection and memory responses is indeed the final goal of vaccination. We will discuss data from our as well as other laboratories which strongly suggest that triggering a specific and persistent anti-tumor CD4+ TH cell response stably modify not only the tumor microenvironment but also tumor-dependent extratumor microenvironments by eliminating and/or reducing the blood-derived tumor infiltrating cells that may have a pro-tumor growth function such as regulatory CD4+/CD25+ T cells and myeloid-derived-suppressor cells. Within this frame, therefore, we believe that the establishment of a pro-tumor environment is not the cause but simply the consequence of the tumor strategy to primarily counteract components of the adaptive cellular immunity, particularly TH lymphocytes.

Tumor targeting properties of antibody fusion proteins based on different members of the murine tumor necrosis superfamily

The tumor necrosis factor superfamily (TNFSF) consists of more than 20 members that can modulate cellular and immunological functions, including cell survival and the stimulation of an inflammatory response. Many TNF superfamily members display potent anticancer activity when used as recombinant proteins in vitro and in vivo. While TNF, TRAIL and FasL have already been used as payloads in antibody-based pharmacodelivery strategies, most TNF superfamily members have not yet been investigated as antibody payloads. Here, we report the cloning, production and characterization of eight novel antibody fusion proteins based on CD40L, FasL, TRAIL, LiGHT, VEGI, lymphotoxin alpha, lymphotoxin beta and lymphotoxin alpha1/beta2. The monoclonal antibody F8 was chosen as fusion partner of proven tumor targeting performance, which recognizes the alternatively-spliced EDA domain of fibronectin, a marker of angiogenesis. A quantitative biodistribution analysis performed with radioiodinated protein preparations in tumor-bearing mice revealed that TRAIL and lymphotoxin alpha1/beta2 were able to selectively accumulate at the tumor site, while all other members of the TNF superfamily abrogated the selective tumor targeting performance of the parental antibody or accumulated also in healthy tissues. The study indicates that even cytokines, which are closely related in terms of structure and function, may have a substantially different impact on the biodistribution and functional properties of the corresponding fusions with disease-homing antibodies.

Peptide-mediated targeting of cytokines to tumor vasculature: the NGR-hTNF example

A growing body of evidence suggests that the efficacy of cytokines in cancer therapy can be increased by targeting strategies based on conjugation with ligands that recognize receptors expressed by tumor cells or elements of the tumor microenvironment, including the tumor vasculature. The targeting approach is generally conceived to permit administration of low, yet pharmacologically active, doses of drugs, thereby avoiding toxic reactions. However, it is becoming clear that, in the case of cytokines, this strategy has another inherent advantage, i.e. the possibility of administering extremely low doses that do not activate systemic counter-regulatory mechanisms, which may limit their potential therapeutic effects. This review is focused on the use of tumor vasculature-homing peptides as vehicles for targeted delivery of cytokines to tumor blood vessel. In particular, we provide an overview of peptide-cytokine conjugates made with peptides containing the NGR, RGD, isoDGR or RGR sequences and describe, in more details, the biological and pharmacological properties of NGR-hTNF, a peptide-tumor necrosis factor-α conjugate that is currently being tested in phase II and III clinical studies. The results of preclinical and clinical studies performed with these products suggest that peptide-mediated vascular-targeting is indeed a viable strategy for delivering bioactive amounts of cytokines to tumor endothelial cells without causing the activation of counter-regulatory mechanisms and toxic reactions.

Antitumor activity of TNF-α after intratumoral injection using an in situ thermosensitive hydrogel

Local drug delivery strategies based on nanoparticles, gels, polymeric films, rods and wafers are increasingly used in cancer chemotherapy in order to enhance therapeutic effect and reduce systemic toxicity. Herein, a biodegradable and biocompatible in situ thermosensitive hydrogel was designed and employed to deliver tumor necrosis factor-α (TNF-α) locally by intratumoral injection. The triblock copolymer was synthesized by ring-opening polymerization (ROP) of β-butyrolactone (β-BL) and lactide (LA) in bulk using polyethylene glycol (PEG) as an initiator and Sn(Oct)2 as the catalyst, the polymer was characterized by NMR, gel permeation chromatography and differential scanning calorimetry. Blood and tumor pharmacokinetics and in vivo antitumor activity of TNF-α after intratumoral administration in hydrogel or solution with the same dose were evaluated on S180 tumor-bearing mice. Compared with TNF-α solution, TNF-α hydrogel exhibited a longer T1/2 (4-fold) and higher AUCtumor (19-fold), but Cmax was lower (0.5-fold), which means that the hydrogel formulation improved the efficacy with a lower systhemic exposure than the solution formation. In addition, TNF-α hydrogel improved the antitumor activity and survival due to lower systemic exposure than the solution. These results demonstrate that the in situ thermosensitive hydrogel-based local delivery system by intratumoral injection is well suited for the administration of TNF-α.

License for destruction: tumor-specific cytokine targeting

Stroma is an integral part of solid tumors and plays a key role in growth promotion and immune suppression. Most current therapies focus on destroying tumors and/or abnormal vasculature. However, evidence is emerging that anticancer efficacy improves with vessel normalization rather than destruction. Specific targeting of cytokines into tumors provides proof-of-concept that tumor stroma is dynamic and can be remodeled to increase drug access and alleviate immune suppression. Changing the inflammatory milieu 'opens' tumors for therapy and thus provides a license for destruction. This involves reprogramming of paracrine signaling networks between multiple stromal components to break the vicious cycle of angiogenesis and immune suppression. With active immunotherapy rapidly moving into the clinic, local cytokine delivery emerges as an attractive adjuvant.

Immunocytokines: a review of molecules in clinical development for cancer therapy

The concept of therapeutically enhancing the immune system’s responsiveness to tumors is long standing. Several cytokines have been investigated in clinical trials for their therapeutic activity in cancer patients. However, substantial side effects and unfavorable pharmacokinetic properties have been a major drawback hampering the administration of therapeutically relevant doses. The use of recombinant antibody–cytokine fusion proteins promises to significantly enhance the therapeutic index of cytokines by targeting them to the site of disease. This review aims to provide a concise and complete overview of the preclinical data and clinical results currently available for all immunocytokines having reached clinical development.

The antibody-based targeted delivery of interleukin-4 and 12 to the tumor neovasculature eradicates tumors in three mouse models of cancer

Preclinical studies with recombinant murine interleukin 4 (IL4) in models of cancer have shown potent tumor growth inhibition. However, systemic administration of human IL4 to cancer patients exhibited modest antitumor activity and considerable toxicities. To improve the therapeutic index and reduce side effects of this cytokine, we developed of a novel "immunocytokine" based on sequential fusion of murine IL4 with the antibody fragment F8 (specific to the alternatively spliced extra-domain A of fibronectin, a marker for tumor-angiogenesis) in diabody format. The resulting fusion protein, termed F8-IL4, retained full antigen-binding activity and cytokine bioactivity and was able to selectively localize on solid tumors in vivo. When used as single agent, F8-IL4 inhibited tumor growth in three different immunocompetent murine cancer models (F9 teratocarcinoma, CT26 colon carcinoma and A20 lymphoma). Furthermore, F8-IL4 showed synergistic effects when coadministered with immunocytokines based on IL2 and IL12. Indeed, combination therapy with an IL12-based immunocytokine yielded complete tumor eradication, in spite of the fact that IL4 and IL12 display opposite immunological mechanisms of action in terms of their polarization of T-cell based responses. No weight loss or any signs of toxicity were observed in treated mice, both in monotherapy and in combination, indicating a good tolerability of the immunocytokine treatment. Interestingly, mice cured from CT26 tumors acquired a durable protective antitumor immunity. Depletion experiments indicated that the antitumor activity was mediated by CD8+ T cells and by NK cells.

The antibody-based targeted delivery of TNF in combination with doxorubicin eradicates sarcomas in mice and confers protective immunity

Background:

Soft-tissue sarcomas are a group of malignancies of mesenchymal origin, which typically have a dismal prognosis if they reach the metastatic stage. The observation of rare spontaneous remissions in patients suffering from concomitant bacterial infections had triggered the clinical investigation of the use of heat-killed bacteria as therapeutic agents (Coley's toxin), which induced complete responses in patients in the pre-chemotherapy era and is now known to mediate substantial elevations in serum TNF levels.

Methods:

We designed and developed a novel immunocytokine based on murine TNF sequentially fused to the antibody fragment F8 (specific to extra-domain A of fibronectin). The antitumor activity was studied in two syngeneic murine sarcoma models.

Results:

The L19 antibody (specific to extra-domain B of fibronectin) has shown by SPECT imaging procedures to selectively localise on sarcoma in a patient with a peripheral nerve sheath tumour, and immunohistochemical analysis of human soft-tissue sarcoma samples showed comparable antigen expression of EDA and EDB. The antibody-based pharmacodelivery of TNF by the fusion protein ‘F8–TNF' to oncofetal fibronectin in sarcoma-bearing mice leads to complete and long-lasting tumour eradications when administered in combination with doxorubicin, the first-line drug for the treatment of sarcomas in humans. Doxorubicin alone did not display any therapeutic effect in both tested models of this study. The cured mice had acquired protective immunity against the tumour, as they rejected subsequent challenges with sarcoma cells.

Conclusion:

The findings of this study provide a rationale for the clinical study of the fully human immunocytokine L19-TNF in combination with doxorubicin in patients with soft-tissue sarcoma.

NGR-TNF, a novel vascular-targeting agent, does not induce cytokine recruitment of proangiogenic bone marrow-derived cells

Background:

Administration of certain chemotherapy drugs at the maximum tolerated dose, vascular-disrupting agents (VDAs) and irradiation can induce mobilisation and tumour homing of proangiogenic bone marrow-derived cells (BMDCs). Increases in cytokines and chemokines contribute to such mobilisation that eventually promotes tumour (re)growth. NGR-TNF is a vascular-targeting agent in advanced clinical development, coupling the CNGRCG angiogenic vessel-homing peptide with tumour necrosis factor-alpha (TNF). We investigated whether NGR-TNF mobilises host BMDCs and growth factors.

Methods:

Blood was obtained from Lewis lung carcinoma and 4T1 tumour-bearing mice at different time points following NGR-TNF, VDA or anti-VEGFR2/flk-1 antibody treatment. Levels of circulating growth factors were assessed by ELISAs. BMDCs were characterised by FACS. Circulating endothelial progenitor cells were defined as CD45⁻/CD13⁺/flk-1⁺/CD117⁺/7AAD⁻, Tie2-expressing monocytes as CD45⁺/CD11b⁺/Tie2⁺ and myeloid-derived suppressor cells as CD45⁺/CD11b⁺/Gr1⁺ cells.

Results:

NGR-TNF decreases tumour blood vessel density-inducing apoptosis of tumour and tumour endothelial cells. Unlike VDAs, or high-dose NGR-TNF, lower doses of NGR-TNF, comparable to those used in clinical trials, neither mobilise nor recruit to the tumour site proangiogenic BMDCs or induce host growth factors.

Conclusion:

Low-dose NGR-TNF exerts antitumour activity without inducing proangiogenic host responses, conceivably important for preventing/overcoming resistance and designing combination therapeutic strategies.

Schedule-dependent therapeutic efficacy of L19mTNF-α and melphalan combined with gemcitabine

L19-tumor necrosis factor alpha (L19mTNF-α; L), a fusion protein consisting of mouse TNFα and the human antibody fragment L19 directed to the extra domain-B (ED-B) of fibronectin, is able to selectively target tumor vasculature and to exert a long-lasting therapeutic activity in combination with melphalan (M) in syngeneic mouse tumor models. We have studied the antitumor activity of single L19mTNF-α treatment in combination with melphalan and gemcitabine (G) using different administration protocols in two histologically different murine tumor models: WEHI-164 fibrosarcoma and K7M2 osteosarcoma. All responding mice showed significant reduction in myeloid-derived suppressor cells (MDSCs) and an increase in CD4⁺ and CD8⁺ T cells in the tumor infiltrates, as well as significant reduction in regulatory T cells (Treg) at the level of draining lymph nodes. What is important is that all cured mice rejected tumor challenge up to 1 year after therapy. Targeted delivery of L19mTNF-α synergistically increases the antitumor activity of melphalan and gemcitabine, but optimal administration schedules are required. This study provides information for designing clinical studies using L19mTNF-α in combination with chemotherapeutic drugs.

Targeted delivery of L19mTNF-α synergistically increases the antitumor activity of melphalan and gemcitabine, but optimal administration schedule requires a pretreatment with L19mTNF-α otherwise an antagonistic effect could occur. This study provides information for designing clinical studies using L19mTNF-α in combination with chemotherapeutic drugs.

Adequate antigen availability: a key issue for novel approaches to tumor vaccination and tumor immunotherapy

A crucial parameter for activation of the anti-tumor immune response is an adequate antigen availability (AAA) defined here as the optimal tumor antigen dose and related antigen processing and MHC-II-restricted presentation necessary to efficiently trigger tumor-specific TH cells. We will discuss two distinct experimental systems: a) a preventive anti-tumor vaccination system; b) a therapy-induced anti-tumor vaccination approach. In the first case tumor cells are rendered constitutively MHC-II+ by transfecting them with the MHC-II transcriptional activator CIITA. Here AAA is generated by the function of tumor's newly expressed MHC-II molecules to present tumor-associated antigens to tumor-specific TH cells. In the second case, AAA is generated by treating established tumors with neovasculature-targeted TNFα. In conjuction with Melphalan, targeted TNFα delivery produces extensive areas of tumor necrosis that generate AAA capable of optimally activate tumor-specific TH cells which in turn activate CTL immune effectors. In both experimental systems tumor rejection and persistent and long-lived TH cell anti-tumor memory, responsible of defending the animals from subsequent challenges with tumor cells, are achieved. Based on these and other investigators' results we propose that AAA is a key element for triggering adaptive immune functions resulting in subversion from a pro-tumor to an anti-tumor microenvironment, tumor rejection and acquisition of anti-tumor immune memory. Hypotheses of neuro-immune networks involved in these approaches are discussed. These considerations are important also for the comprehension of how chemotherapy and/or radiation therapies may help to block and/or to eradicate the tumor and for the construction of suitable anti-tumor vaccine strategies.

Phase I/II study of the tumour-targeting human monoclonal antibody-cytokine fusion protein L19-TNF in patients with advanced solid tumours

PURPOSE

L19-TNF is an armed antibody that selectively targets human TNF to extra domain B-fibronectin on tumour blood vessels. We performed a phase I/II first-in-man trial with L19-TNF monotherapy in metastatic solid cancer patients to study safety and signs of clinical activity.

METHODS

Six cohorts of patients were treated with increasing (1.3-13 μg/kg) doses of intravenous L19-TNF on day 1, 3, and 5 of repeated 3-weekly cycles, and 12 colorectal cancer patients were treated at 13 μg/kg. PK, antibody formation, changes in lymphocyte subsets, 5-HIAA plasma levels as well as safety and clinical activity were analysed.

RESULTS

Thirty-four patients received at least one L19-TNF dose. The serum half-life of L19-TNF at 13 μg/kg was 33.6 min, and maximum peak serum concentration was 73.14 μg/L. Mild chills, nausea and vomiting but no haemato- or unexpected toxicity were observed. Grade 3 lumbar pain in bone metastasis was the only dose-limiting toxicity found in one patient. Objective tumour responses were not detected. Transient stable disease occurred in 19 of 31 evaluable patients.

CONCLUSIONS

Intravenous L19-TNF on day 1, 3, and 5 of a 3-weekly schedule was safe up to 13 μg/kg, but did not result in objective tumour responses. The maximally tolerated dose (MTD) was not reached, allowing for further dose escalation of L19-TNF possibly in combination with chemotherapy.

The immunocytokine L19-IL2 eradicates cancer when used in combination with CTLA-4 blockade or with L19-TNF

Systemic high-dose IL2 promotes long-term survival in a subset of metastatic melanoma patients, but this treatment is accompanied by severe toxicities. The immunocytokine L19-IL2, in which IL2 is fused to the human L19 antibody capable of selective accumulation on tumor neovasculature, has recently shown encouraging clinical activity in patients with metastatic melanoma. In this study, we have investigated the therapeutic performance of L19-IL2, administered systemically in combination with a murine anti-CTLA-4 antibody or with a second clinical-stage immunocytokine (L19-TNF) in two syngeneic immunocompetent mouse models of cancer. We observed complete tumor eradications when L19-IL2 was used in combination with CTLA-4 blockade. Interestingly, mice cured from F9 tumors developed new lesions when rechallenged with tumor cells after therapy, whereas mice cured from CT26 tumors were resistant to tumor rechallenge. Similarly, L19-IL2 induced complete remissions when administered in a single intratumoral injection in combination with L19-TNF, whereas the two components did not lead to cures when administered as single agents. These findings provide a rationale for combination trials in melanoma, as the individual therapeutic agents have been extensively studied in clinical trials, and the antigen recognized by the L19 antibody has an identical sequence in mouse and man.

Optimal MHC-II-restricted tumor antigen presentation to CD4+ T helper cells: the key issue for development of anti-tumor vaccines

Present immunoprevention and immunotherapeutic approaches against cancer suffer from the limitation of being not “sterilizing” procedures, as very poor protection against the tumor is obtained. Thus newly conceived anti-tumor vaccination strategies are urgently needed. In this review we will focus on ways to provide optimal MHC class II-restricted tumor antigen presentation to CD4+ T helper cells as a crucial parameter to get optimal and protective adaptive immune response against tumor. Through the description of successful preventive or therapeutic experimental approaches to vaccinate the host against the tumor we will show that optimal activation of MHC class II-restricted tumor specific CD4+ T helper cells can be achieved in various ways. Interestingly, the success in tumor eradication and/or growth arrest generated by classical therapies such as radiotherapy and chemotherapy in some instances can be re-interpreted on the basis of an adaptive immune response induced by providing suitable access of tumor-associated antigens to MHC class II molecules. Therefore, focussing on strategies to generate better and suitable MHC class II–restricted activation of tumor specific CD4+ T helper cells may have an important impact on fighting and defeating cancer.

Tumor-targeted TNFα stabilizes tumor vessels and enhances active immunotherapy

Solid tumors are intrinsically resistant to immune rejection. Abnormal tumor vasculature can act as a barrier for immune cell migration into tumors. We tested whether targeting IFNγ and/or TNFα into pancreatic neuroendocrine tumors can alleviate immune suppression. We found that intratumoral IFNγ causes rapid vessel loss, which does not support anti-tumor immunity. In contrast, low-dose TNFα enhances T-cell infiltration and overall survival, an effect that is exclusively mediated by CD8(+) effector cells. Intriguingly, lymphocyte influx does not correlate with increased vessel leakiness. Instead, low-dose TNFα stabilizes the vascular network and improves vessel perfusion. Inflammatory vessel remodeling is, at least in part, mediated by tumor-resident macrophages that are reprogrammed to secrete immune and angiogenic modulators. Moreover, inflammatory vessel remodeling with low-dose TNFα substantially improves antitumor vaccination or adoptive T-cell therapy. Thus, low-dose TNFα promotes both vessel remodeling and antitumor immune responses and acts as a potent adjuvant for active immunotherapy.

Immunocytokines: a novel class of potent armed antibodies

Several cytokines have been investigated in clinical trials, based on their potent therapeutic activity observed in animal models of cancer and other diseases. However, substantial toxicities are often reported at low doses, thus preventing escalation to therapeutically active regimens. The use of recombinant antibodies or antibody fragments as delivery vehicles promises to enhance greatly the therapeutic index of pro-inflammatory and anti-inflammatory cytokines. This review surveys preclinical and clinical data published in the field of antibody-cytokine fusions (immunocytokines). Molecular determinants (such as molecular format, valence, target antigen), which crucially contribute to immunocytokine performance in vivo, are discussed in the article, as well as recent trends for the combined use of this novel class of biopharmaceuticals with other therapeutic agents.

How to improve exposure of tumor cells to drugs: promoter drugs increase tumor uptake and penetration of effector drugs

Solid tumors are characterized by an abnormal architecture and composition that limit the uptake and distribution of antitumor drugs. Over the last two decades, drugs have been identified that improve the tumor uptake and distribution of drugs that have direct antitumor effects. We propose to refer to these drugs as promoter drugs, and as effector drugs to drugs that have direct antitumor effects. Some promoter drugs have received regulatory approval, while others are in active clinical development. This review gives an overview of promoter drugs, by classifying them according to their mechanism of action: promoter drugs that modulate tumor blood flow, modify the barrier function of tumor vessels, induce tumor cell killing, and overcome stromal barriers. Eventually, we discuss those that we feel are the main conclusions to be drawn from promoter drug research that has been performed so far, and suggest areas of future investigation to improve the efficacy of promoter drugs in cancer therapy.

Nanoparticle preconditioning for enhanced thermal therapies in cancer

Nanoparticles show tremendous promise in the safe and effective delivery of molecular adjuvants to enhance local cancer therapy. One important form of local cancer treatment that suffers from local recurrence and distant metastases is thermal therapy. In this article, we review a new concept involving the use of nanoparticle-delivered adjuvants to 'precondition' or alter the vascular and immunological biology of the tumor to enhance its susceptibility to thermal therapy. To this end, a number of opportunities to combine nanoparticles with vascular and immunologically active agents are reviewed. One specific example of preconditioning involves a gold nanoparticle tagged with a vascular targeting agent (i.e., TNF-α). This nanoparticle embodiment demonstrates preconditioning through a dramatic reduction in tumor blood flow and induction of vascular damage, which recruits a strong and sustained inflammatory infiltrate in the tumor. The ability of this nanoparticle preconditioning to enhance subsequent heat or cold thermal therapy in a variety of tumor models is reviewed. Finally, the potential for future clinical imaging to judge the extent of preconditioning and thus the optimal timing and extent of combinatorial thermal therapy is discussed.

Microvascular biodistribution of L19-SIP in angiogenesis targeting strategies

INTRODUCTION

Various strategies using L19-mediated fibronectin targeting have become useful clinical tools in anti-tumour therapy and diagnostics. The aim of our study was to characterise the microvascular biodistribution and binding process during tumour angiogenesis and after anti-angiogenic therapy.

MATERIALS AND METHODS

SF126 glioma and F9 teratocarcinoma cells were implanted into dorsal skin fold chambers (SF126: n = 4; F9: n = 6). Using fluorescence and confocal intravital microscopy the biodistribution process was assessed at t = 0 h, t = 4 h and t = 24 h after intravenous application of Cy3-L19-SIP. Sunitinib treatment was applied for six days and microscopy was performed 2 and 6 days after treatment initiation. Analysed parameters included: vascular and interstitial binding, preferential binding sites of L19-SIP, microvascular blood flow rate, microvascular permeability. Histological analysis included CD31 and DAPI.

RESULTS

L19-SIP showed a specific and time-dependent neovascular binding with a secondary extravasation process reaching optimal vascular/interstitial binding ratio 4 hours after iv administration (F9: L19-SIP: vascular binding: 74.6 ± 14.5; interstitial binding: 46.8 ± 12.1; control vascular: 22,2 ± 16.6). Angiogenic sprouts were preferred binding sites (F9: L19-SIP: 188 ± 15.5; RTV: 90.6 ± 13.5). Anti-angiogenic therapy increased microvascular hemodynamics (SF126: Su: 106.6 ± 13.3 μl/sec; Untreated: 19.7 ± 9.1 μl/sec) and induced increased L19-SIP accumulation (SF 126: t24; Su: 92.6 ± 2.7; Untreated: 71.9 ± 5.9) in therapy resistant tumour vessels.

CONCLUSION

L19-SIP shows a time and blood-flow dependent microvascular biodistribution process with angiogenic sprouts as preferential binding sites followed by secondary extravasation of the antibody. Microvascular biodistribution is enhanced in anti-angiogenic-therapy resistant tumour vessels.