Interleukin-2: Evaluation of Routes of Administration and Current Delivery Systems in Cancer Therapy

The present and future of immunocytokines for cancer treatment

Monoclonal antibody (mAb) therapy has successfully been introduced as treatment of several lymphomas and leukemias. However, solid tumors reduce the efficacy of mAb therapy because of an immune-suppressive tumor micro-environment (TME), which hampers activation of effector immune cells. Pro-inflammatory cytokine therapy may counteract immune suppression in the TME and increase mAb efficacy, but untargeted pro-inflammatory cytokine therapy is limited by severe off-target toxicity and a short half-life of cytokines. Antibody-cytokine fusion proteins, also referred to as immunocytokines, provide a solution to either issue, as the antibody both acts as local delivery platform and increases half-life. The antibody can furthermore bridge local cytotoxic immune cells, like macrophages and natural killer cells with tumor cells, which can be eliminated after effector cells are activated via the cytokine. Currently, a variety of different antibody formats as well as a handful of cytokine payloads are used to generate immunocytokines. However, many potential formats and payloads are still left unexplored. In this review, we describe current antibody formats and cytokine moieties that are used for the development of immunocytokines, and highlight several immunocytokines in (pre-)clinical studies. Furthermore, potential future routes of development are proposed.

Therapeutic Response Assessment of High-Grade Gliomas During Early-Phase Drug Development in the Era of Molecular and Immunotherapies

ABSTRACT

Several new therapeutic strategies have emerged over the past decades to address unmet clinical needs in high-grade gliomas, including targeted molecular agents and various forms of immunotherapy. Each of these strategies requires addressing fundamental questions, depending on the stage of drug development, including ensuring drug penetration into the brain, engagement of the drug with the desired target, biologic effects downstream from the target including metabolic and/or physiologic changes, and identifying evidence of clinical activity that could be expanded upon to increase the likelihood of a meaningful survival benefit. The current review article highlights these strategies and outlines how imaging technology can be used for therapeutic response evaluation in both targeted and immunotherapies in early phases of drug development in high-grade gliomas.

Engineering Strategies for Immunomodulatory Cytokine Therapies - Challenges and Clinical Progress

Cytokines are immunoregulatory proteins involved in many pathological states with promising potential as therapeutic agents. A diverse array of cytokines have been studied in preclinical disease models since the 1950s, some of which became successful biopharmaceutical products with the advancement of recombinant protein technology in the 1980s. However, following these early approvals, clinical translation of these natural immune signaling molecules has been limited due to their pleiotropic action in many cell types, and the fact that they have evolved to act primarily locally in tissues. These characteristics, combined with poor pharmacokinetics, have hindered the delivery of cytokines via systemic administration routes due to dose-limiting toxicities. However, given their clinical potential and recent clinical successes in cancer immunotherapy, cytokines continue to be extensively pursued in preclinical and clinical studies, and a range of molecular and formulation engineering strategies are being applied to reduce treatment toxicity while maintaining or enhancing therapeutic efficacy. This review provides a brief background on the characteristics of cytokines and their history as clinical therapeutics, followed by a deeper discussion on the engineering strategies developed for cytokine therapies with a focus on the translational relevance of these approaches.

Treatment of equine sarcoids using recombinant poxviruses expressing feline interleukin-2

BACKGROUND

Interleukin (IL)-2 stimulates antitumour immunity and is successfully used for the treatment of different neoplasias.

HYPOTHESIS/OBJECTIVES

Canarypox virus locally expressing feline IL-2 is safe and can be used to treat equine sarcoids.

ANIMALS

Twenty horses of different breeds with a median age of eight years (interquartile range 6.0-13.3 years) and a total number of 59 sarcoids were included in the study.

METHODS

In this prospective clinical trial, sarcoids were injected twice seven days apart, with a recombinant canarypox virus expressing feline IL-2. Complete blood counts (CBC) and fibrinogen levels were measured before treatment and on days 1, 2, 7 and 8.

RESULTS

Complete regression was achieved in eight horses (40%) and partial regression in two horses (10%). No change in sarcoid size was observed in two horses (10%) and the disease progressed in five horses (25%). Sarcoids of three horses (15%) showed initial response followed by tumour growth. There were no significant changes in CBC and fibrinogen levels after either injection. One horse developed a mild fever the day after each injection, which subsided without treatment the following day.

CONCLUSIONS

Treatment of equine sarcoids with recombinant canarypox virus expressing feline IL-2 seems to be a safe therapy option. Although the expression of IL-2 after vector injection and its biological activity in horses were not proven in this study, the treatment resulted in regression and partial regression in 50% of the cases. Further studies are necessary to verify these findings and to establish a treatment protocol.

Next Generation Imaging Techniques to Define Immune Topographies in Solid Tumors

In recent years, cancer immunotherapy experienced remarkable developments and it is nowadays considered a promising therapeutic frontier against many types of cancer, especially hematological malignancies. However, in most types of solid tumors, immunotherapy efficacy is modest, partly because of the limited accessibility of lymphocytes to the tumor core. This immune exclusion is mediated by a variety of physical, functional and dynamic barriers, which play a role in shaping the immune infiltrate in the tumor microenvironment. At present there is no unified and integrated understanding about the role played by different postulated models of immune exclusion in human solid tumors. Systematically mapping immune landscapes or "topographies" in cancers of different histology is of pivotal importance to characterize spatial and temporal distribution of lymphocytes in the tumor microenvironment, providing insights into mechanisms of immune exclusion. Spatially mapping immune cells also provides quantitative information, which could be informative in clinical settings, for example for the discovery of new biomarkers that could guide the design of patient-specific immunotherapies. In this review, we aim to summarize current standard and next generation approaches to define Cancer Immune Topographies based on published studies and propose future perspectives.

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.

Imaging of T-cells and their responses during anti-cancer immunotherapy

Immunotherapy has proven to be an effective approach in a growing number of cancers. Despite durable clinical responses achieved with antibodies targeting immune checkpoint molecules, many patients do not respond. The common denominator for immunotherapies that have successfully been introduced in the clinic is their potential to induce or enhance infiltration of cytotoxic T-cells into the tumour. However, in clinical research the molecules, cells and processes involved in effective responses during immunotherapy remain largely obscure. Therefore, in vivo imaging technologies that interrogate T-cell responses in patients represent a powerful tool to boost further development of immunotherapy. This review comprises a comprehensive analysis of the in vivo imaging technologies that allow the characterisation of T-cell responses induced by anti-cancer immunotherapy, with emphasis on technologies that are clinically available or have high translational potential. Throughout we discuss their respective strengths and weaknesses, providing arguments for selecting the optimal imaging options for future research and patient management.

Combination of Immunotherapy With Targeted Therapy: Theory and Practice in Metastatic Melanoma

Metastatic melanoma is the most aggressive and obstinate skin cancer with poor prognosis. Variant novel applicable regimens have emerged during the past decades intensively, while the most profound approaches are oncogene-targeted therapy and T-lymphocyte mediated immunotherapy. Although targeted therapies generated remarkable and rapid clinical responses in the majority of patients, acquired resistance was developed promptly within months leading to tumor relapse. By contrast, immunotherapies elicited long-term tumor regression. However, the overall response rate was limited. In view of the above, either targeted therapy or immunotherapy cannot elicit durable clinical responses in large range of patients. Interestingly, the advantages and limitations of these regimens happened to be complementary. An increasing number of preclinical studies and clinical trials proved a synergistic antitumor effect with the combination of targeted therapy and immunotherapy, implying a promising prospect for the treatment of metastatic melanoma. In order to achieve a better therapeutic effectiveness and reduce toxicity in patients, great efforts need to be made to illuminate multifaceted interplay between targeted therapy and immunotherapy.

Adoptive T-Cell Therapy for Solid Malignancies

The use of immunotherapies for solid and hematologic malignancies has demonstrated durable antitumor effects. Use of checkpoint inhibitors allows for immunologic reactivation of the adaptive immune system against tumor-specific neoantigens and effective rejection. Recent developments in adoptive transfer of T cells has shown effective immune rejection of solid malignancies and durable regression. Adoptive cell transfer involves extraction of in vivo T lymphocytes, selection for or introduction of tumor reactive cells, in vitro expansion, and delivery of the T-cell product back to the patient. This article discusses the different approaches, challenges, and further directions of adoptive T-cell transfer in solid malignancies.

Release characteristics of cellulose sulphate capsules and production of cytokines from encapsulated cells

The size and speed of release of proteins of different sizes from standard cellulose sulphate capsules (Cell-in-a-Box®) was investigated. Proteins with molecular weights of up to around 70kD can be released. The conformation, charge and concentration of the protein being released play a role in the release kinetics. Small proteins such as cytokines can be easily released. The ability to produce cytokines at a sustained and predefined level from encapsulated cells genetically engineered to overexpress such cytokines and implanted into patients may aid immunotherapies of cancer as well as infectious and other diseases. It will also allow allogeneic rather than autologous cells to be used. We show that cells encapsulated in polymers of cellulose sulphate are able to release cytokines such as interleukin-2 (IL-2) in a stimulated fashion e.g. using phorbol 12-myristate 13-acetate (PMA) plus ionomycin. Given the excellent documented safety record of cellulose sulphate in patients, these data suggest that clinical usage of the technology may be warranted for cancer treatment and other diseases.

Immunomodulatory Monoclonal Antibodies in Combined Immunotherapy Trials for Cutaneous Melanoma

In the last few years, there has been a twist in cancer treatment toward immunotherapy thanks to the impressive results seen in advanced patients from several tumor pathologies. Cutaneous melanoma is a highly mutated and immunogenic tumor that has been a test field for the development of immunotherapy. However, there is still a way on the road to achieving complete and long-lasting responses in most patients. It is desirable that immunotherapeutic strategies induce diverse immune reactivity specific to tumor antigens, including the so-called neoantigens, as well as the blockade of immunosuppressive mechanisms. In this review, we will go through the role of promising monoclonal antibodies in cancer immunotherapy with immunomodulatory function, especially blocking of the inhibitory immune checkpoints CTLA-4 and PD-1, in combination with different immunotherapeutic strategies such as vaccines. We will discuss the rational basis for these combinatorial approaches as well as different schemes currently under study for cutaneous melanoma in the clinical trials arena. In this way, the combination of "push and release" immunomodulatory therapies can contribute to achieving a more robust and durable antitumor immune response in patients.

Interleukin-2: Old and New Approaches to Enhance Immune-Therapeutic Efficacy

Interleukin-2 (IL-2) is a very well-known cytokine that has been studied for the past 35 years. It plays a major role in the growth and proliferation of many immune cells such NK and T cells. It is an important immunotherapy cytokine for the treatment of various diseases including cancer. Systemic delivery of IL-2 has shown clinical benefit in renal cell carcinoma and melanoma patients. However, its use has been limited by the numerous toxicities encountered with the systemic delivery. Intravenous IL-2 causes the well-known "capillary leak syndrome," or the leakage of fluid from the circulatory system to the interstitial space resulting in hypotension (low blood pressure), edema, and dyspnea that can lead to circulatory shock and eventually cardiopulmonary collapse and multiple organ failure. Due to the toxicities associated with systemic IL-2, an aerosolized delivery approach has been developed, which enables localized delivery and a higher local immune cell activation. Since proteins are absorbed via pulmonary lymphatics, after aerosol deposition in the lung, aerosol delivery provides a means to more specifically target IL-2 to the local immune system in the lungs with less systemic effects. Its benefits have extended to diseases other than cancer. Delivery of IL-2 via aerosol or as nebulized IL-2 liposomes has been previously shown to have less toxicity and higher efficacy against sarcoma lung metastases. Dogs with cancer provided a highly relevant means to determine biodistribution of aerosolized IL-2 and IL-2 liposomes. However, efficacy of single-agent IL-2 is limited. As in general, for most immune-therapies, its effect is more beneficial in the face of minimal residual disease. To overcome this limitation, combination therapies using aerosol IL-2 with adoptive transfer of T cells or NK cells have emerged.Using a human osteosarcoma (OS) mouse model, we have demonstrated the efficacy of single-agent aerosol IL-2 and combination therapy aerosol IL-2 and NK cells or aerosol IL-2 and interleukin 11 receptor alpha-directed chimeric antigen receptor-T cells (IL-11 receptor α CAR-T cells) against OS pulmonary metastases. Combination therapy resulted in a better therapeutic effect. A Phase-I trial of aerosol IL-2 was done in Europe and proved to be safe. Others and our preclinical studies provided the basis for the development of a Phase-I aerosol IL-2 trial in our institution to include younger patients with lung metastases. OS, our disease of interest, has a peak incidence in the adolescent and young adult years. Our goal is to complete this trial in the next 2 years.In this chapter, we summarize the different effects of IL-2 and cover the advantages of the aerosol delivery route for diseases of the lung with an emphasis on some of our most recent work using combination therapy aerosol IL-2 and NK cells for the treatment of OS lung metastases.

Fluorinated dendrimer for TRAIL gene therapy in cancer treatment

The transfection of tumor necrosis factor-related apoptosis-inducing ligand gene by using fluorinated dendrimer is highly efficient and low toxic, resulting in efficient killing of cancer cells in vitro and suppressing tumor growth in vivo.

Functional Modulation of Regulatory T Cells by IL-2

The suppressive function of regulatory T cells (Tregs) is critical to the maintenance of immune homeostasis in vivo and yet, the specific identification of Tregs by phenotypic markers is not perfect. Tregs were originally identified in the CD4+CD25+ fraction of T cells, but FoxP3 expression was later included as an additional marker of Tregs as FoxP3 expression was identified as being critical to the development and function of these cells. Intracellular expression of FoxP3 makes it difficult in using to isolate live and not permeabilized cells for functional assays. As such CD4+CD25+ fraction is still frequently used for functional assays of Tregs. Although, the CD4+CD25+ fraction substantially overlaps with the FoxP3+ fraction, the minor mismatch between CD4+CD25+ and FoxP3+ fractions may confound the functional characteristics of Tregs. In this study, we isolated CD4+FoxP3+ as well as CD4+CD25+ fractions from Foxp3 knock-in mice, and compared their proliferative and suppressive activity in the presence or absence of various concentrations of IL-2. Our results showed comparable patterns of proliferative and suppressive responses for both fractions, except that contrary to the CD4+CD25+ fraction the FoxP3+ fraction did not proliferate in an autocrine fashion even in response to a strong stimulation. In presence of exogenous IL-2, both CD4+CD25+ and CD4+FoxP3+ fractions were more sensitive than the CD4+CD25- responder cells in proliferative responsiveness. In addition, a low dose IL-2 enhanced whereas a high dose abrogated the suppressive activities of the CD4+CD25+ and CD4+FoxP3+ fractions. These results may provide an additional understanding of the characteristics of the various fractions of isolated Tregs based on phenotype and function and the role of varying levels of exogenous IL-2 on the suppressive activity of these cells.

MicroRNA-33b inhibits lung adenocarcinoma cell growth, invasion, and epithelial-mesenchymal transition by suppressing Wnt/β-catenin/ZEB1 signaling

Altered expression of microRNA (miRNA) is associated with lung carcinogenesis and metastasis. Our previous study of lung cancer miRNAs using the gene chip assay demonstrated altered miR-33b expression in lung adenocarcinoma. The present study further investigated miR-33b expression, function, and gene regulation in lung cancer cells in vitro and in nude mouse xenografts. Our data showed that the level of miR-33b expression was dramatically decreased in lung adenocarcinoma cell lines and tissues and that the reduced miR-33b expression was associated with tumor lymph node metastasis. Furthermore, restoration of miR-33b expression inhibited lung adenocarcinoma cell proliferation, migration, and invasion and tumor cell epithelial-mesenchymal transition (EMT) in vitro. Luciferase assay revealed that miR-33b bound to ZEB1 3'-UTR region and inhibited ZEB1 expression, while expression of ZEB1 mRNA and miR-33b was inversely associated with lung adenocarcinoma cell lines and tissues. Subsequently, we found that miR-33b suppressed the activity of WNT/β-catenin signaling in lung adenocarcinoma cells and in turn suppressed tumor cell growth and EMT in vitro and in vivo nude mouse xenografts. In conclusion, the present study provided novel insight into the molecular mechanism of lung adenocarcinoma progression. MicroRNA-33b should be further investigated as a potential therapeutic target in human lung adenocarcinoma.

Photo-irradiation paradigm: Mapping a remarkable facile technique used for advanced drug, gene and cell delivery

Undoubtedly, the progression of photo-irradiation technique has provided a smart engineering tool for the state-of-the-art biomaterials that guide the biomedical and therapeutic domains for promoting the modern pharmaceutical industry. Many investigators had exploited such a potential technique to create/ameliorate numerous pharmaceutical carriers. These carriers show promising applications that vary from small drug to therapeutic protein delivery and from gene to living cell encapsulation design. Harmony between the properties of precisely engineered precursors and the formed network structure broadens the investigator's intellect for both brilliant creations and effective applications. As well, controlling photo-curing at the formulation level, through manipulating the absorption of light stimuli, photoinitiator system and photo-responsive precursor, facilitates the exploration of novel distinctive biomaterials. Discussion of utilizing different photo-curing procedures in designing/formulation of different pharmaceutical carriers is the main emphasis of this review. In addition, recent applications of these intelligent techniques in targeted, controlled, and sustained drug delivery with understanding of photo-irradiation concept and mechanism are illustrated.

Combining immunotherapy with oncogene-targeted therapy: a new road for melanoma treatment

Cutaneous melanoma arises from the malignant transformation of skin melanocytes; its incidence and mortality have been increasing steadily over the last 50 years, now representing 3% of total tumors. Once melanoma metastasizes, prognosis is somber and therapeutic options are limited. However, the discovery of prevalent BRAF mutations in at least 50% of melanoma tumors led to development of BRAF-inhibitors, and other drugs targeting the MAPK pathway including MEK-inhibitors, are changing this reality. These recently approved treatments for metastatic melanoma have made a significant impact on patient survival; though the results are shadowed by the appearance of drug-resistance. Combination therapies provide a rational strategy to potentiate efficacy and potentially overcome resistance. Undoubtedly, the last decade has also born a renaissance of immunotherapy, and encouraging advances in metastatic melanoma treatment are illuminating the road. Immune checkpoint blockades, such as CTLA-4 antagonist-antibodies, and multiple cancer vaccines are now invaluable arms of anti-tumor therapy. Recent work has brought to light the delicate relationship between tumor biology and the immune system. Host immunity contributes to the anti-tumor activity of oncogene-targeted inhibitors within a complex network of cytokines and chemokines. Therefore, combining immunotherapy with oncogene-targeted drugs may be the key to melanoma control. Here, we review ongoing clinical studies of combination therapies using both oncogene inhibitors and immunotherapeutic strategies in melanoma patients. We will revisit the preclinical evidence that tested sequential and concurrent schemes in suitable animal models and formed the basis for the current trials. Finally, we will discuss potential future directions of the field.

Formulation and stability of cytokine therapeutics

Cytokines are messenger proteins that regulate the proliferation and differentiation of cells and control immune responses. Interferons, interleukins, and growth factors have applications in cancer, autoimmune, and viral disease treatment. The cytokines are susceptible to chemical and physical instability. This article reviews the structure and stability issues of clinically used cytokines, as well as formulation strategies for improved stability. Some general aspects for identifying most probable stability concerns, selecting excipients, and developing stable cytokine formulations are presented. The vast group of cytokines offers possibilities for new biopharmaceuticals. The formulation approaches of the current cytokine products could facilitate development of new biopharmaceuticals.

Pathologic complete response to intralesional interleukin-2 therapy associated with improved survival in melanoma patients with in-transit disease

PURPOSE

Melanoma patients with in-transit disease have a high mortality rate despite various treatment strategies. The aim of this study was to validate the role of intralesional interleukin (IL)-2, to understand its mechanism of action, and to better understand factors that may influence its response.

METHODS

We retrospectively collected the clinicopathological data of 31 consecutive patients who presented to a tertiary care cancer center for treatment of in-transit melanoma with intralesional IL-2. Kaplan-Meier survival curves and multivariable Cox regression analysis were performed. Immunohistochemistry (IHC) was used to better understand the immune response to localized IL-2 therapy. Targeted next-generation sequencing was performed to genomically characterize the tumors.

RESULTS

Ten patients (10/31, 32 %) achieved a pathologic complete response (pCR), 17/21 (55 %) had a partial response, and 4/21 (19 %) had progressive disease on treatment. pCR to IL-2 therapy was associated with overall survival (log-rank p = 0.004) and improved progression-free survival (PFS) [adjusted hazard ratio (HR) 0.11; 95 % CI 0.02-0.47; p = 0.003). A higher CD8+ T cell infiltrate was identified in in-transit lesions with a pCR compared with the other lesions (mean IHC score 3.78 vs. 2.61; p = 0.01). Patients with an elevated CD8+ infiltrate demonstrated an improved PFS (unadjusted HR 0.08; 95 % CI 0.01-0.52; p = 0.008).

CONCLUSIONS

Thirty-two percent of patients achieved pCR with intralesional IL-2 therapy and had a significantly improved PFS compared with the rest of the cohort, which may be explained by a systemic CD8+ T-cell response.

Challenges and developing solutions for increasing the benefits of IL-2 treatment in tumor therapy

Interleukin-2 (IL-2) is a cytokine with pleiotropic effects on the immune system. Systemic IL-2 treatment has produced durable responses in melanoma and renal cancer patients, but unfortunately this is effective only in a fraction of patients. Moreover, IL-2 treatment also engenders serious side effects, which limit its clinical utility. It is now appreciated that IL-2 not only stimulates NK and effector T cells but also has a critical role in the generation and maintenance of regulatory T cells, which act to dampen immune responses. Thus, successful immunotherapy of cancers using IL-2 has to address two fundamentally important issues: (1) how to limit side effects yet be active where it is needed, and (2) how to preferentially activate effector T cells while limiting the stimulation of Tregs. Strategies are now being developed to address these critical obstacles that may lead to a renaissance of IL-2 therapy.

The effect of interleukin-2 on canine peripheral nerve sheath tumours after marginal surgical excision: a double-blind randomized study

Background

The objective of this study was to evaluate the effect on outcomes of intraoperative recombinant human interleukin-2 injection after surgical resection of peripheral nerve sheath tumours. In this double-blind trial, 40 patients due to undergo surgical excision (<5 mm margins) of presumed peripheral nerve sheath tumours were randomized to receive intraoperative injection of interleukin-2 or placebo into the wound bed.

Results

There were no significant differences in any variable investigated or in median survival between the two groups. The median recurrence free interval was 874 days (range 48–2141 days), The recurrence-free interval and overall survival time were significantly longer in dogs that undergone the primary surgery by a specialist-certified surgeon compared to a referring veterinarian regardless of whether additional adjunct therapy was given.

Conclusion

Overall, marginal excision of peripheral nerve sheath tumours in dogs resulted in a long survival time, but adjuvant treatment with recombinant human interleukin-2 (rhIL-2) did not provide a survival advantage.

Oligodeoxynucleotides expressing polyguanosine motifs promote antitumor activity through the upregulation of IL-2

The primary goal of cancer immunotherapy is to elicit an immune response capable of eliminating the tumor. One approach toward accomplishing that goal uses general (rather than tumor-specific) immunomodulatory agents to boost the number and activity of pre-existing CTLs. We find that the intratumoral injection of polyguanosine (poly-G) oligonucleotides (ODN) has such an effect, boosting antitumor immunity and promoting tumor regression. The antitumor activity of poly-G ODN was mediated through CD8 T cells in a TLR9-independent manner. Mechanistically, poly-G ODN directly induced the phosphorylation of Lck (an essential element of the T cell-signaling pathway), thereby enhancing the production of IL-2 and CD8 T cell proliferation. These findings establish poly-G ODN as a novel type of cancer immunotherapy.

Induction of interleukin 2 expression in the liver for the treatment of H22 hepatoma in mice

BACKGROUND AND AIMS

We designed this study to evaluate the ability of a plasmid carrying an RU486 regulatory system to induce expression of interleukin-2 (IL-2) gene and to examine the antitumour efficacy of the induced IL-2 gene.

METHODS

The plasmid pRS-mIL-2,which contains an RU486 inducible system and IL-2 gene was injected into mice. Sera and tissues from liver, spleen, lungs and kidneys were taken to test the properties of the plasmid. To examine the antitumour efficacy of pRS-mIL-2, tumours were established in the liver by direct inoculation of H22 hepatoma cells.

RESULTS

The IL-2 levels in serum correlated with the dose of plasmid and RU486. High and sustained IL-2 levels could be achieved by administration of RU486 every day. The mRNA of transgene IL-2 was found only in the liver. Treatment of mice with pRS-mIL-2 plus RU486 resulted in the significant reduction in tumour volume compared with control groups.

CONCLUSIONS

Tight temporal and spatial control of transgene IL-2 expression can be achieved by a plasmid containing an RU486 inducible system driven by liver specific promoter. pRS-mIL-2 exhibited strong antitumour efficacy following consecutive induction with RU486.

Palmitate-derivatized human IL-2: a potential anticancer immunotherapeutic of low systemic toxicity

PURPOSE AND EXPERIMENTAL DESIGN

Recombinant human IL-2 (rhIL-2) is a potent cytokine and FDA-approved anticancer drug. However, its clinical use has been limited by severe toxicity, associated primarily with systemic administration with excess protein distributing freely throughout the body. We hypothesized that rhIL-2 in alternate forms permitting more restricted localization may exert stronger antitumor efficacy and less toxicity. Here, we have tested the utility of palmitate-derivatized rhIL-2. rhIL-2 was reacted with N-hydroxysuccinimide palmitate ester. The resultant lipidated rhIL-2 (pIL-2), when mixed with cells, could spontaneously transfer from solution to cell surfaces. Next, anticancer efficacy of pIL-2 was assessed in two modalities. For adoptive T cell therapy, antitumor cytotoxic T cells (CTLs) were protein transferred ("painted") with pIL-2 and injected into mice bearing lymphoma. For in situ therapy, pIL-2 was injected intratumorally into mice bearing melanoma. Tumor growth and IL-2-associated toxicity were determined.

RESULTS

In the lymphoma model, painting of the antitumor CTLs with pIL-2 markedly increased their viability and titer. In the melanoma model, intratumoral injection of pIL-2, but not rhIL-2, increased the number of activated CD8(+) T cells (IFN-γ(+)) in the spleen, reduced lung metastasis and prolonged the survival of treated mice. Moreover, while repeated intratumoral injection of rhIL-2 at an excessively high dose (10 injections of 10,000 IU/mouse) caused marked vascular leakage syndrome, the same regimen using pIL-2 caused no detectable toxicity.

CONCLUSIONS

Transferring spontaneously from solution to cell surfaces, pIL-2 may bypass the current limitations of rhIL-2 and, thus, serve as a more effective and tolerable anticancer drug.

Antitumoral activity of parvovirus-mediated IL-2 and MCP-3/CCL7 delivery into human pancreatic cancer: implication of leucocyte recruitment

Pancreatic ductal adenocarcinoma (PDAC) represents the fourth leading cause of cancer-related death in western countries. The patients are often diagnosed in advanced metastatic stages, and the prognosis remains extremely poor with an overall 5-year survival rate less than 5 %. Currently, novel therapeutic strategies are being pursued to combat PDAC, including oncolytic viruses, either in their natural forms or armed with immunostimulatory molecules. Natural killer cells are critical players against tumours and infected cells. Recently, we showed that IL-2-activated human NK cells displayed killing activity against PDAC cells, which could further be enhanced through the infection of PDAC cells with the rodent parvovirus H-1PV. In this study, the therapeutic efficacy of parvovirus-mediated delivery of three distinct cyto/chemokines (Il-2, MCP-3/CCL7 and IP-10/CXCL10) was evaluated in xenograft models of human PDAC. We show here that activated NK and monocytic cells were found to be recruited by PDAC tumours upon infection with parvoviruses armed with IL-2 or the chemokine MCP-3/CCL7, resulting in a strong anti-tumour response.

Particle-mediated delivery of cytokines for immunotherapy

The ability of cytokines to direct the immune response to vaccination, infection and tumors has motivated their use in therapy to augment or shape immunity. To avoid toxic side effects associated with systemic cytokine administration, several approaches have been developed using particle-encapsulated cytokines to deliver this cargo to specific cell types and tissues. Initial work used cytokine-loaded particles to deliver proinflammatory cytokines to phagocytes to enhance antimicrobial and antitumor responses. These particles have also been used to create a cytokine depot at a local site to supplement prophylactic or antitumor vaccines or injected directly into solid tumors to activate immune cells to eliminate established tumors. Finally, recent advances have revealed that paracrine delivery of cytokines directly to T cells has the potential to enhance T-cell mediated therapies. The studies reviewed here highlight the progress in the last 30 years that has established the potential of particle-mediated cytokine immunotherapy.

In vitro assessment of choline dihydrogen phosphate (CDHP) as a vehicle for recombinant human interleukin-2 (rhIL-2)

Choline dihydrogen phosphate (CDHP) is an ionic liquid reported to increase thermal stability of model proteins. The current work investigated CDHP effect on structural integrity and biological activity of recombinant human interleukin-2 (rhIL-2), a therapeutic protein used for treating advanced melanoma. In vitro CDHP biocompatibility was also evaluated using primary cell cultures, or B16-F10 cell line, chronically exposed to the ionic liquid. Formulation of rhIL-2 in an aqueous 680mM CDHP pH 7.4 solution resulted in a 12.5°C increase in the T_m of rhIL-2 compared to a basic buffer formulation, and provided conformational rhIL-2 stabilization when the solution was heated to 23.3°C above the T_m. CDHP solutions (≤80mM), exhibited no cytotoxic activity toward primary splenocytes or B16-F10 cells in culture. However, a 10-fold loss in biological activity was observed when rhIL-2 was used in a 30mM CDHP aqueous solution with NaHCO₃ (pH≥7.2) compared to controls without CDHP. While increased T_m is associated with a diminished rhIL-2 biological activity, the therapeutic protein remains structurally intact and functional.

Structure and function of proteins in hydrated choline dihydrogen phosphate ionic liquid

Ionic liquids are being intensely studied as promising media for the stabilization of proteins and other biomolecules. Choline dihydrogen phosphate (CDHP) has been identified as one of the most promising candidates for this application. In this work we have probed in more detail the effects that CDHP may have on the thermodynamics, structure, and stability of proteins, including one of therapeutic interest. Microcalorimetry and circular dichroism spectropolarimetry (CD) were used to assess the thermal stability of protein solutions in CDHP/water mixtures at various concentrations. Increasing thermal stability of lysozyme and interleukin-2 in proportion to CDHP concentration was observed. Isothermal titration calorimetry (ITC) was used to quantify binding interactions, and indicate that the mechanism for stability does not appear to be dependent upon CDHP binding to protein. CD and small angle X-ray scattering (SAXS) analyses were used to probe for structural changes due to the presence of CDHP. SAXS indicates charge effects on the surface of the protein play a role in protein stability in ionic liquids, and no significant alteration of the overall tertiary conformation of lysozyme was observed at 25 °C. However, after incubation at 37 °C or at higher concentrations of CDHP, small changes in protein structure were seen. Effects on protein activity were monitored using turbidity assays, and CDHP decreases protein activity but does not eliminate it. Protein solubility was also monitored using a turbidity assay and was found to be inversely proportional to the concentration of CDHP in solution.

A phase I/II study of chemotherapy followed by donor lymphocyte infusion plus interleukin-2 for relapsed acute leukemia after allogeneic hematopoietic cell transplantation

The efficacy of donor lymphocyte infusion (DLI) for treatment of relapsed acute leukemia after allogeneic hematopoietic cell transplantation is limited. We hypothesized that interleukin-2 (IL-2) combined with DLI after chemotherapy might augment graft-versus-leukemia effects. To identify a safe and effective IL-2 regimen, a phase I/II study of DLI plus IL-2 therapy was performed for such patients. After chemotherapy, 17 patients received DLI (1 × 10(8) CD3/kg for patients with related donors, and 0.1 × 10(8) CD3/kg for those with unrelated donors) and an escalating dose of induction IL-2 (1.0, 2.0, or 3.0 × 10(6) IU/m(2)/day representing levels I [n = 7], Ia [n = 9], and II [n = 1]) for 5 days followed by maintenance (1.0 × 10(6) IU/m(2)/day) for 10 days as a continuous intravenous infusion. Unacceptable IL-2-related toxicities developed in 1 patient at level I, 2 at level Ia, and 1 at level II. Grades III-IV acute graft-versus-host disease (aGVHD) developed in 5 patients, and extensive chronic GVHD (cGVHD) developed in 8. Eight patients had a complete remission after chemotherapy prior to DLI, and 2 additional patients had a complete remission after DLI plus IL-2 therapy. In conclusion, the maximal tolerated induction dose of IL-2 combined with DLI appears to be 1.0 × 10(6) IU/m(2)/day. IL-2 administration after DLI might increase the incidence of cGVHD.

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.