Intratumoral immunocytokine treatment results in enhanced antitumor effects

Administration of intratumoral GD2-directed interleukin-2 immunocytokine and local radiation therapy to activate immune rejection of spontaneous canine melanoma

Canine malignant melanoma provides a clinically relevant, large animal parallel patient population to study the GD2-reactive hu14.18-IL-2 immunocytokine as it is similar to human melanoma and expresses GD2. The objectives of this study were to evaluate safety, radiation fractionation, and identify informative biomarkers of an in-situ tumor vaccine involving local radiation therapy plus intratumoral-immunocytokine in melanoma tumor-bearing dogs. Twelve dogs (six dogs/arm) with locally advanced or metastatic melanoma were randomized to receive a single 8 Gy fraction (arm A) or three 8 Gy fractions over 1 week (arm B) to the primary site and regional lymph nodes (when clinically involved) with the single or last fraction 5 days before intratumoral-immunocytokine at 12 mg/m 2 on 3 consecutive days. Serial tumor biopsies were obtained. All 12 dogs completed protocol treatment, and none experienced significant or unexpected adverse events. Evidence of antitumor activity includes one dog with a complete response at day 60, one dog with a partial response at day 60, and four dogs with mixed responses. Histology of serial biopsies shows a variably timed increase in intratumoral lymphocytic inflammation in some dogs. Canine NanoString analyses of serial biopsies identified changes in gene signatures of innate and adaptive cell types versus baseline. There were no significant differences in NanoString results between arm A and arm B. We conclude that intratumoral-immunocytokine in combination with local radiation therapy in canine melanoma is well tolerated and has antitumor activity with the potential to inform clinical development in melanoma patients.

GD2-targeting therapy: a comparative analysis of approaches and promising directions

Disialoganglioside GD2 is a promising target for immunotherapy with expression primarily restricted to neuroectodermal and epithelial tumor cells. Although its role in the maintenance and repair of neural tissue is well-established, its functions during normal organism development remain understudied. Meanwhile, studies have shown that GD2 plays an important role in tumorigenesis. Its functions include proliferation, invasion, motility, and metastasis, and its high expression and ability to transform the tumor microenvironment may be associated with a malignant phenotype. Structurally, GD2 is a glycosphingolipid that is stably expressed on the surface of tumor cells, making it a suitable candidate for targeting by antibodies or chimeric antigen receptors. Based on mouse monoclonal antibodies, chimeric and humanized antibodies and their combinations with cytokines, toxins, drugs, radionuclides, nanoparticles as well as chimeric antigen receptor have been developed. Furthermore, vaccines and photoimmunotherapy are being used to treat GD2-positive tumors, and GD2 aptamers can be used for targeting. In the field of cell therapy, allogeneic immunocompetent cells are also being utilized to enhance GD2 therapy. Efforts are currently being made to optimize the chimeric antigen receptor by modifying its design or by transducing not only αβ T cells, but also γδ T cells, NK cells, NKT cells, and macrophages. In addition, immunotherapy can combine both diagnostic and therapeutic methods, allowing for early detection of disease and minimal residual disease. This review discusses each immunotherapy method and strategy, its advantages and disadvantages, and highlights future directions for GD2 therapy.

Cytokines and their role as immunotherapeutics and vaccine Adjuvants: The emerging concepts

Cytokines are a protein family comprising interleukins, lymphokines, chemokines, monokines and interferons. They are significant constituents of the immune system, and they act in accordance with specific cytokine inhibiting compounds and receptors for the regulation of immune responses. Cytokine studies have resulted in the establishment of newer therapies which are being utilized for the treatment of several malignant diseases. The advancement of these therapies has occurred from two distinct strategies. The first strategy involves administrating the recombinant and purified cytokines, and the second strategy involves administrating the therapeutics which inhibits harmful effects of endogenous and overexpressed cytokines. Colony stimulating factors and interferons are two exemplary therapeutics of cytokines. An important effect of cytokine receptor antagonist is that they can serve as anti-inflammatory agents by altering the treatments of inflammation disorder, therefore inhibiting the effects of tumour necrosis factor. In this article, we have highlighted the research behind the establishment of cytokines as therapeutics and vaccine adjuvants, their role of immunotolerance, and their limitations.

Intratumoral nanobody-IL-2 fusions that bind the tumor extracellular matrix suppress solid tumor growth in mice

Confining cytokine exposure to the tumors would greatly enhance cancer immunotherapy safety and efficacy. Immunocytokines, cytokines fused to tumor-targeting antibodies, have been developed with this intention, but without significant clinical success to date. A critical limitation is uptake by receptor-expressing cells in the blood, that decreases the dose at the tumor and engenders toxicity. Small-format immunocytokines, constructed with antibody fragments, are hypothesized to improve tumor specificity due to rapid systemic clearance. However, effective design criteria for small-format immunocytokines need further examination. Here, we engineer small interleukin-2 (IL-2) immunocytokines fused to nanobodies with nanomolar to picomolar affinities for the tumor-specific EIIIB domain of fibronectin (also known as EDB). Upon intravenous delivery into immunocompetent mice, such immunocytokines led to similar tumor growth delay as size-matched untargeted IL-2. Intratumoral (i.t.) delivery imparted improved survival dependent on affinity to EIIIB. I.t. administration offers a promising avenue to deliver small-format immunocytokines, given effective affinity for the tumor microenvironment.

Alum-anchored intratumoral retention improves the tolerability and antitumor efficacy of type I interferon therapies

Effective antitumor immunity in mice requires activation of the type I interferon (IFN) response pathway. IFNα and IFNβ therapies have proven promising in humans, but suffer from limited efficacy and high toxicity. Intratumoral IFN retention ameliorates systemic toxicity, but given the complexity of IFN signaling, it was unclear whether long-term intratumoral retention of type I IFNs would promote or inhibit antitumor responses. To this end, we compared the efficacy of IFNα and IFNβ that exhibit either brief or sustained retention after intratumoral injection in syngeneic mouse tumor models. Significant enhancement in tumor retention, mediated by anchoring these IFNs to coinjected aluminum-hydroxide (alum) particles, greatly improved both their tolerability and efficacy. The improved efficacy of alum-anchored IFNs could be attributed to sustained pleiotropic effects on tumor cells, immune cells, and nonhematopoietic cells. Alum-anchored IFNs achieved high cure rates of B16F10 tumors upon combination with either anti-PD-1 antibody or interleukin-2. Interestingly however, these alternative combination immunotherapies yielded disparate T cell phenotypes and differential resistance to tumor rechallenge, highlighting important distinctions in adaptive memory formation for combinations of type I IFNs with other immunotherapies.

Short-course neoadjuvant in situ vaccination for murine melanoma

BACKGROUND

Surgical resection remains an important component of multimodality treatment for most solid tumors. Neoadjuvant immunotherapy has several potential advantages, including in-situ tumor vaccination and pathologic assessment of response in the surgical specimen. We previously described an in-situ tumor vaccination strategy in melanoma using local radiation (RT) and an intratumoral injection of tumor-specific anti-GD2 immunocytokine (IT-IC). Here we tested whether neoadjuvant in-situ tumor vaccination using anti-GD2 immunocytokine and surgical resection, without RT, could generate immunologic memory capable of preventing recurrence or distant metastasis.

METHODS

Mice bearing GD2 expressing B78 melanoma tumors were treated with neoadjuvant radiation, IT-IC, or combined RT + IT-IC. Surgical resection was performed following neoadjuvant immunotherapy. Immune infiltrate was assessed in the resection specimens. Mice were rechallenged with either B78 contralateral flank tumors or pulmonary seeding of non-GD2 expressing B16 melanoma metastasis induced experimentally. Rejection of rechallenge in mice treated with the various treatment regimens was considered evidence of immunologic memory.

RESULTS

Neoadjuvant IT-IC and surgical resection resulted in increased CD8 T cell infiltration, a higher CD8:regulatory T cell ratio, and immunologic memory against contralateral flank rechallenge. The timing of resection did not significantly impact the development of memory, which was present as early as the day of surgery. There was less local wound toxicity with neoadjuvant IT-IC compared with neoadjuvant RT +IT IC. Neoadjuvant IT-IC and resection resulted in the rejection of B16 lung metastasis in a CD4 T cell dependent manner.

CONCLUSIONS

Neoadjuvant IT-IC generates immunologic memory capable of preventing distant metastasis despite limited efficacy against large primary melanoma tumors. By combining neoadjuvant tumor vaccination and surgery, the toxicity of local RT was avoided. These preclinical data support further investigation regarding the use of neoadjuvant IT-IC in patients with melanoma at high risk for occult distant disease.

Interleukin 2-Based Fusion Proteins for the Treatment of Cancer

Interleukin 2 (IL-2) plays a fundamental role in both immune activation and tolerance and has revolutionized the field of cancer immunotherapy since its discovery. The ability of IL-2 to mediate tumor regression in preclinical and clinical settings led to FDA approval for its use in the treatment of metastatic renal cell carcinoma and metastatic melanoma in the 1990s. Although modest success is observed in the clinic, cancer patients receiving IL-2 therapy experience a wide array of side effects ranging from flu-like symptoms to life-threatening conditions such as vascular leak syndrome. Over the past three decades, efforts have focused on circumventing IL-2-related toxicities by engineering methods to localize IL-2 to the tumor or secondary lymphoid tissue, preferentially activate CD8⁺ T cells and NK cells, and alter pharmacokinetic properties to increase bioavailability. This review summarizes the various IL-2-based strategies that have emerged, with a focus on chimeric fusion methods.

Radiation Augments the Local Anti-Tumor Effect of In Situ Vaccine With CpG-Oligodeoxynucleotides and Anti-OX40 in Immunologically Cold Tumor Models

Introduction

Combining CpG oligodeoxynucleotides with anti-OX40 agonist antibody (CpG+OX40) is able to generate an effective in situ vaccine in some tumor models, including the A20 lymphoma model. Immunologically "cold" tumors, which are typically less responsive to immunotherapy, are characterized by few tumor infiltrating lymphocytes (TILs), low mutation burden, and limited neoantigen expression. Radiation therapy (RT) can change the tumor microenvironment (TME) of an immunologically "cold" tumor. This study investigated the effect of combining RT with the in situ vaccine CpG+OX40 in immunologically "cold" tumor models.

Methods

Mice bearing flank tumors (A20 lymphoma, B78 melanoma or 4T1 breast cancer) were treated with combinations of local RT, CpG, and/or OX40, and response to treatment was monitored. Flow cytometry and quantitative polymerase chain reaction (qPCR) experiments were conducted to study differences in the TME, secondary lymphoid organs, and immune activation after treatment.

Results

An in situ vaccine regimen of CpG+OX40, which was effective in the A20 model, did not significantly improve tumor response or survival in the "cold" B78 and 4T1 models, as tested here. In both models, treatment with RT prior to CpG+OX40 enabled a local response to this in situ vaccine, significantly improving the anti-tumor response and survival compared to RT alone or CpG+OX40 alone. RT increased OX40 expression on tumor infiltrating CD4+ non-regulatory T cells. RT+CpG+OX40 increased the ratio of tumor-infiltrating effector T cells to T regulatory cells and significantly increased CD4+ and CD8+ T cell activation in the tumor draining lymph node (TDLN) and spleen.

Conclusion

RT significantly improves the local anti-tumor effect of the in situ vaccine CpG+OX40 in immunologically "cold", solid, murine tumor models where RT or CpG+OX40 alone fail to stimulate tumor regression.

Implantable optical fibers for immunotherapeutics delivery and tumor impedance measurement

Immune checkpoint blockade antibodies have promising clinical applications but suffer from disadvantages such as severe toxicities and moderate patient-response rates. None of the current delivery strategies, including local administration aiming to avoid systemic toxicities, can sustainably supply drugs over the course of weeks; adjustment of drug dose, either to lower systemic toxicities or to augment therapeutic response, is not possible. Herein, we develop an implantable miniaturized device using electrode-embedded optical fibers with both local delivery and measurement capabilities over the course of a few weeks. The combination of local immune checkpoint blockade antibodies delivery via this device with photodynamic therapy elicits a sustained anti-tumor immunity in multiple tumor models. Our device uses tumor impedance measurement for timely presentation of treatment outcomes, and allows modifications to the delivered drugs and their concentrations, rendering this device potentially useful for on-demand delivery of potent immunotherapeutics without exacerbating toxicities.

Utilizing Immunocytokines for Cancer Therapy

Cytokine therapy for cancer has indicated efficacy in certain diseases but is generally accompanied by severe toxicity. The field of antibody-cytokine fusion proteins (immunocytokines) arose to target these effector molecules to the tumor environment in order to expand the therapeutic window of cytokine therapy. Pre-clinical evidence has shown the increased efficacy and decreased toxicity of various immunocytokines when compared to their cognate unconjugated cytokine. These anti-tumor properties are markedly enhanced when combined with other treatments such as chemotherapy, radiotherapy, and checkpoint inhibitor antibodies. Clinical trials that have continued to explore the potential of these biologics for cancer therapy have been conducted. This review covers the in vitro, in vivo, and clinical evidence for the application of immunocytokines in immuno-oncology.

Prostate cancer cells enhance interleukin-15-mediated expansion of NK cells

OBJECTIVES

To identify cytokines that can activate and expand NK cells in the presence of prostate cancer cells in order to determine whether these agents may be useful in future intra-tumoural administration in pre-clinical and clinical prostate cancer trials.

MATERIALS AND METHODS

Lymphocytes isolated from normal donor blood were set up in co-cultures with either cancer or non-cancerous prostate cell lines, together with each of the cytokines interleukin (IL)-2, IL-12, IL-15, interferon (IFN)-γ or IL-21 for a period of 7 days. Then, expansion of NK cells, NKT cells and CD8 T cells was measured by flow cytometry and compared with the expansion of the same cells in the absence of prostate cells. The cytotoxic activity of NK cells, as measured by perforin and tumour cell killing, was also assessed. NK cell receptors and their corresponding ligands on prostate tumour cells were analysed to determine whether any of these were modulated by co-culture. The role of the tumour-secreted heat shock proteins HSP90 and HSP70 in the expansion of NK cells in the co-cultures was also investigated because of their effects on NK and CD8 T-cell activation.

RESULTS

We showed that, among a panel of cytokines known to cause NK cell activation and expansion, only IL-15 could actively induce expansion of NK, NKT and CD8 T cells in the presence of prostate cancer cell lines. Furthermore, the expansion of NK cells was far greater (up to 50% greater) in the presence of the cancer cells (LNCaP, PC3) than when lymphocytes were incubated alone. In contrast, non-cancerous cell lines (PNT2 and WPMY-1) did not exert any expansion of NK cells. The cytolytic activity of the NK cells, as measured by perforin, CD107a and killing of tumour cells, was also greatest in co-cultures with IL-15. Examination of NK cell receptors shows that NKG2D is upregulated to a greater degree in the presence of prostate cancer cells, compared with the upregulation with IL-15 in lymphocytes alone. However, blocking of NKG2D does not inhibit the enhanced expansion of NK cells in the presence of tumour cells.

CONCLUSIONS

Among a panel of NK cell-activating cytokines, IL-15 was the only cytokine that could stimulate expansion of NK cells in the presence of prostate cancer cells; therefore IL-15 may be a good candidate for novel future intra-tumoural therapy of the disease.

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.

Natural Killer Cell-Based Cancer Immunotherapy: A Review on 10 Years Completed Clinical Trials

NK cell cancer immunotherapy is an emerging anti-tumour therapeutic strategy that explores NK cell stimulation. In this review, we address strategies developed to circumvent limitations to clinical application of NK cell-based therapies, and comprehensively review the design and results of clinical trials conducted in the past 10 years (2008-2018) to test their therapeutic potential. NK cell-based immunotherapy of solid cancers remains controversial, but merit further detailed investigation.

Human and murine IL2 receptors differentially respond to the human-IL2 component of immunocytokines

The humanized immunocytokine, hu14.18-IL2 (ICp), leads to the immune cell-mediated destruction of GD2-expressing tumors in mouse models, resulting in potent antitumor effects with negligible IL2-related toxicity. In contrast, when ICp is used clinically, antitumor activity is accompanied by dose-limiting IL2-related toxicities. These species-specific differences in ICp toxicity may be linked to differential binding to mouse vs. human IL2 receptors (IL2Rs). We evaluated immunocytokines genetically engineered to preferentially bind either high-affinity αβγ-IL2Rs or intermediate-affinity βγ-IL2Rs. These ICs have the IL2 fused to the C-terminus of the IgG light chains rather than the heavy chains. We found that IC35, containing intact huIL2, maintained activation of human and mouse αβγ-IL2Rs but exhibited a 20-fold reduction in the ability to stimulate human βγ-IL2Rs, with no activation of mouse βγ-IL2Rs at the concentrations tested. The reduced ability of IC35 to stimulate human βγ-IL2Rs (associated with IL2-toxicities) makes it a potential candidate for clinical trials where higher clinical IC doses might enable better tumor targeting and increased antitumor effects with less toxicity. Contrastingly, ICSK (IC with an IL2 mutein that has enhanced binding to the IL2R β-chain) showed increased activation over ICp on mouse βγ-IL2Rs, with a dose-response curve similar to that seen with IC35 on human βγ-IL2Rs. Our data suggest that ICSK might be used in mouse models to simulate the anticipated effects of IC35 in clinical testing. Understanding the differences in species-dependent IL2R activation should facilitate the design of reagents and mouse models that better simulate the potential activity of IL2-based immunotherapy in patients.

Effective Combination of Innate and Adaptive Immunotherapeutic Approaches in a Mouse Melanoma Model

Most cancer immunotherapies include activation of either innate or adaptive immune responses. We hypothesized that the combined activation of both innate and adaptive immunity will result in better antitumor efficacy. We have previously shown the synergy of an agonistic anti-CD40 mAb (anti-CD40) and CpG-oligodeoxynucleotides in activating macrophages to induce tumor cell killing in mice. Separately, we have shown that a direct intratumoral injection of immunocytokine (IC), an anti-GD2 Ab linked to IL-2, can activate T and NK cells resulting in antitumor effects. We hypothesized that activation of macrophages with anti-CD40/CpG, and NK cells with IC, would cause innate tumor destruction, leading to increased presentation of tumor Ags and adaptive T cell activation; the latter could be further augmented by anti-CTLA-4 Ab to achieve tumor eradication and immunological memory. Using the mouse GD2⁺ B78 melanoma model, we show that anti-CD40/CpG treatment led to upregulation of T cell activation markers in draining lymph nodes. Anti-CD40/CpG + IC/anti-CTLA-4 synergistically induced regression of advanced s.c. tumors, resulting in cure of some mice and development of immunological memory against B78 and wild type B16 tumors. Although the antitumor effect of anti-CD40/CpG did not require T cells, the antitumor effect of IC/anti-CTLA-4 was dependent on T cells. The combined treatment with anti-CD40/CpG + IC/anti-CTLA-4 reduced T regulatory cells in the tumors and was effective against distant solid tumors and lung metastases. We suggest that a combination of anti-CD40/CpG and IC/anti-CTLA-4 should be developed for clinical testing as a potentially effective novel immunotherapy strategy.

Anti-GD2 mAbs and next-generation mAb-based agents for cancer therapy

Tumor-specific monoclonal antibodies (mAbs) have demonstrated efficacy in the clinic, becoming an important approach for cancer immunotherapy. Due to its limited expression on normal tissue, the GD2 disialogangloside expressed on neuroblastoma cells is an excellent candidate for mAb therapy. In 2015, dinutuximab (an anti-GD2 mAb) was approved by the US FDA and is currently used in a combination immunotherapeutic regimen for the treatment of children with high-risk neuroblastoma. Here, we review the extensive preclinical and clinical development of anti-GD2 mAbs and the different mechanisms by which they mediate tumor cell killing. In addition, we discuss different mAb-based strategies that capitalize on the targeting ability of anti-GD2 mAbs to potentially deliver, as monotherapy, or in combination with other treatments, improved antitumor efficacy.

Antibody fusions with immunomodulatory proteins for cancer therapy

The potential of immunomodulatory proteins, in particular cytokines, for cancer therapy is well recognized, but hampered by the toxicity associated with their systemic application. In order to address this problem, targeted delivery by antibody fusion proteins has been early proposed and their development intensively pursued over the last decade. Here, factors influencing the selection and modification of cytokines and antibody formats for this approach are being discussed, indicating current developments and translational advances in the field.

Antigen specificity can be irrelevant to immunocytokine efficacy and biodistribution

Cytokine therapy can activate potent, sustained antitumor responses, but collateral toxicity often limits dosages. Although antibody-cytokine fusions (immunocytokines) have been designed with the intent to localize cytokine activity, systemic dose-limiting side effects are not fully ameliorated by attempted tumor targeting. Using the s.c. B16F10 melanoma model, we found that a nontoxic dose of IL-2 immunocytokine synergized with tumor-specific antibody to significantly enhance therapeutic outcomes compared with immunocytokine monotherapy, concomitant with increased tumor saturation and intratumoral cytokine responses. Examination of cell subset biodistribution showed that the immunocytokine associated mainly with IL-2R-expressing innate immune cells, with more bound immunocytokine present in systemic organs than the tumor microenvironment. More surprisingly, immunocytokine antigen specificity and Fcγ receptor interactions did not seem necessary for therapeutic efficacy or biodistribution patterns because immunocytokines with irrelevant specificity and/or inactive mutant Fc domains behaved similarly to tumor-specific immunocytokine. IL-2-IL-2R interactions, rather than antibody-antigen targeting, dictated immunocytokine localization; however, the lack of tumor targeting did not preclude successful antibody combination therapy. Mathematical modeling revealed immunocytokine size as another driver of antigen targeting efficiency. This work presents a safe, straightforward strategy for augmenting immunocytokine efficacy by supplementary antibody dosing and explores underappreciated factors that can subvert efforts to purposefully alter cytokine biodistribution.

Intratumoral delivery of low doses of anti-CD40 mAb combined with monophosphoryl lipid a induces local and systemic antitumor effects in immunocompetent and T cell-deficient mice

In this study, an agonistic anti-CD40 monoclonal antibody was combined with monophosphoryl lipid A (MPL), a nontoxic derivative of lipopolysaccharide and agonist of toll-like receptor-4, to assess the immunomodulatory and antitumor synergy between the 2 agents in mice. Anti-CD40 was capable of priming macrophages to subsequent ex vivo activation by MPL in immunocompetent and T-cell-depleted mice. Intraperitoneal injections of anti-CD40+MPL induced additive to synergistic suppression of poorly immunogenic B16-F10 melanoma growing subcutaneously in syngeneic mice. When anti-CD40+MPL were injected directly into the subcutaneous tumor, the combination treatment was more effective, even with a 25-fold reduction in dose. Low-dose intratumoral treatment also slowed the growth of a secondary tumor growing simultaneously at a distant, untreated site. Antitumor effects were also induced in severe combined immunodeficiency mice and in T-cell-depleted C57BL/6 mice. Taken together, our results show that the antitumor effects of anti-CD40 are enhanced by subsequent treatment with MPL, even in T-cell-deficient hosts. These preclinical data suggest that an anti-CD40+MPL combined regimen is appropriate for clinical testing in human patients, including cancer patients who may be immunosuppressed from prior chemotherapy.

Intratumoral treatment of smaller mouse neuroblastoma tumors with a recombinant protein consisting of IL-2 linked to the hu14.18 antibody increases intratumoral CD8+ T and NK cells and improves survival

Hu14.18-IL2 is an immunocytokine (IC) consisting of human IL-2 linked to hu14.18 mAb, which recognizes GD2 disialoganglioside. Phase II clinical trials of intravenous-hu14.18-IL2 (IV-IC) in neuroblastoma and melanoma are underway, and have already demonstrated activity in neuroblastoma. In our Phase II trial, lower neuroblastoma burden at the time of treatment was associated with a greater likelihood of clinical response to IV-IC. We have previously shown that intratumoral-hu14.18-IL2 (IT-IC) compared to IV-IC results in enhanced local and systemic antitumor activity in tumor-bearing mice. We utilized a mouse model to investigate the impact of tumor burden on hu14.18-IL2 treatment efficacy in IV- versus IT-treated animals. Studies presented here describe the analyses of tumor burden at the initiation of treatment and its effects on treatment efficacy, survival, and tumor-infiltrating leukocytes in A/J mice bearing subcutaneous NXS2 neuroblastoma. We show that smaller tumor burden at treatment initiation is associated with increased infiltration of NK and CD8+ T cells and increased overall survival. NXS2 tumor shrinkage shortly after completion of the 3 days of hu14.18-IL2 treatment is necessary for long-term survival. This model demonstrates that tumor size is a strong predictor of hu14.18-IL2-induced lymphocyte infiltration and treatment outcome.

Localized immunotherapy via liposome-anchored Anti-CD137 + IL-2 prevents lethal toxicity and elicits local and systemic antitumor immunity

Immunostimulatory agonists such as anti-CD137 and interleukin (IL)-2 have elicited potent antitumor immune responses in preclinical studies, but their clinical use is limited by inflammatory toxicities that result upon systemic administration. We hypothesized that by rigorously restricting the biodistribution of immunotherapeutic agents to a locally accessible lesion and draining lymph node(s), effective local and systemic antitumor immunity could be achieved in the absence of systemic toxicity. We anchored anti-CD137 and an engineered IL-2Fc fusion protein to the surfaces of PEGylated liposomes, whose physical size permitted dissemination in the tumor parenchyma and tumor-draining lymph nodes but blocked entry into the systemic circulation following intratumoral injection. In the B16F10 melanoma model, intratumoral liposome-coupled anti-CD137 + IL-2Fc therapy cured a majority of established primary tumors while avoiding the lethal inflammatory toxicities caused by equivalent intratumoral doses of soluble immunotherapy. Immunoliposome therapy induced protective antitumor memory and elicited systemic antitumor immunity that significantly inhibited the growth of simultaneously established distal tumors. Tumor inhibition was CD8(+) T-cell-dependent and was associated with increased CD8(+) T-cell infiltration in both treated and distal tumors, enhanced activation of tumor antigen-specific T cells in draining lymph nodes, and a reduction in regulatory T cells in treated tumors. These data suggest that local nanoparticle-anchored delivery of immuno-agonists represents a promising strategy to improve the therapeutic window and clinical applicability of highly potent but otherwise intolerable regimens of cancer immunotherapy. Cancer Res; 73(5); 1547-58. ©2012 AACR.

A phase 1b study of humanized KS-interleukin-2 (huKS-IL2) immunocytokine with cyclophosphamide in patients with EpCAM-positive advanced solid tumors

Background

Humanized KS-interleukin-2 (huKS-IL2), an immunocytokine with specificity for epithelial cell adhesion molecule (EpCAM), has demonstrated favorable tolerability and immunologic activity as a single agent.

Methods

Phase 1b study in patients with EpCAM-positive advanced solid tumors to determine the maximum tolerated dose (MTD) and safety profile of huKS-IL2 in combination with low-dose cyclophosphamide. Treatment consisted of cyclophosphamide (300 mg/m² on day 1), and escalating doses of huKS-IL2 (0.5–4.0 mg/m² IV continuous infusion over 4 hours) on days 2, 3, and 4 of each 21-day cycle. Safety, pharmacokinetic profile, immunogenicity, anti-tumor and biologic activity were evaluated.

Results

Twenty-seven patients were treated for up to 6 cycles; 26 were evaluable for response. The MTD of huKS-IL2 in combination with 300 mg/m² cyclophosphamide was 3.0 mg/m². At higher doses, myelosuppression was dose-limiting. Transient lymphopenia was the most common grade 3/4 adverse event (AE). Other significant AEs included hypotension, hypophosphatemia, and increase in serum creatinine. All patients recovered from these AEs. The huKS-IL2 exposure was dose-dependent, but not dose-proportional, accumulation was negligible, and elimination half-life and systemic clearance were independent of dose and time. Most patients had a transient immune response to huKS-IL2. Immunologic activity was observed at all doses. Ten patients (38%) had stable disease as best response, lasting for ≥ 4 cycles in 3 patients.

Conclusion

The combination of huKS-IL2 with low-dose cyclophosphamide was well tolerated. Although no objective responses were observed, the combination showed evidence of immunologic activity and 3 patients showed stable disease for ≥ 4 cycles.

Trial registration

http://NCT00132522

Stability of the recombinant anti‑erbB2 scFv‑Fc‑interleukin‑2 fusion protein and its inhibition of HER2‑overexpressing tumor cells

The anti‑erbB2 scFv‑Fc‑IL‑2 fusion protein (HFI) is the basis for development of a novel targeted anticancer drug, in particular for the treatment of HER2‑positive cancer patients. HFI was fused with the anti‑erbB2 antibody and human IL‑2 by genetic engineering technology and by antibody targeting characteristics of HFI. IL‑2 was recruited to target cells to block HER2 signaling, inhibit or kill tumor cells, improve the immune capacity, reduce the dose of antibody and IL‑2 synergy. In order to analyse HFI drug ability, HFI plasmid stability was verified by HFI expression of the trend of volume changes. Additionally, HFI could easily precipitate and had progressive characteristics and thus, the buffer system of the additive phosphate‑citric acid buffer, arginine, Triton X‑100 or Tween‑80, the establishment of a microfiltration, ion exchange, affinity chromatography and gel filtration chromatography‑based purification process were explored. HFI samples were obtained according to the requirements of purity, activity and homogeneity. In vivo, HFI significantly delayed HER2 overexpression of non‑small cell lung cancer (Calu‑3) in human non‑small cell lung cancer xenografts in nude mice, and the inhibition rate was more than 60% (P<0.05) in the group treated with 1 mg/kg the HFI dose; HFI significantly inhibited HER2 expression of breast cancer (FVB/neu) transgenic mouse tumor growth in 1 mg/kg of the HFI dose group, and in the following treatment the 400 mm3 tumors disappeared completely. Combined with other HFI test data analysis, HFI not only has good prospects, but also laid the foundation for the development of antibody‑cytokine fusion protein‑like drugs.

Intratumoral hu14.18-IL-2 (IC) induces local and systemic antitumor effects that involve both activated T and NK cells as well as enhanced IC retention

hu14.18-IL-2 (IC) is an immunocytokine consisting of human IL-2 linked to hu14.18 mAb, which recognizes the GD2 disialoganglioside. Phase 2 clinical trials of i.v. hu14.18-IL-2 (i.v.-IC) in neuroblastoma and melanoma are underway and have already demonstrated activity in neuroblastoma. We showed previously that intratumoral hu14.18-IL-2 (IT-IC) results in enhanced antitumor activity in mouse models compared with i.v.-IC. The studies presented in this article were designed to determine the mechanisms involved in this enhanced activity and to support the future clinical testing of intratumoral administration of immunocytokines. Improved survival and inhibition of growth of both local and distant tumors were observed in A/J mice bearing s.c. NXS2 neuroblastomas treated with IT-IC compared with those treated with i.v.-IC or control mice. The local and systemic antitumor effects of IT-IC were inhibited by depletion of NK cells or T cells. IT-IC resulted in increased NKG2D receptors on intratumoral NKG2A/C/E⁺ NKp46⁺ NK cells and NKG2A/C/E⁺ CD8⁺ T cells compared with control mice or mice treated with i.v.-IC. NKG2D levels were augmented more in tumor-infiltrating lymphocytes compared with splenocytes, supporting the localized nature of the intratumoral changes induced by IT-IC treatment. Prolonged retention of IC at the tumor site was seen with IT-IC compared with i.v.-IC. Overall, IT-IC resulted in increased numbers of activated T and NK cells within tumors, better IC retention in the tumor, enhanced inhibition of tumor growth, and improved survival compared with i.v.-IC.

Current and Potential Uses of Immunocytokines as Cancer Immunotherapy

Immunocytokines (ICs) are a class of molecules created by linking tumor-reactive monoclonal antibodies to cytokines that are able to activate immune cells. Tumor selective localization is provided by the ability of the mAb component to bind to molecules found on the tumor cell surface or molecules found selectively in the tumor microenvronment. In this way the cytokine component of the immunocytokine is selectively localized to sites of tumor and can activate immune cells with appropriate receptors for the cytokine. Immunocytokines have been made and tested by us, and others, using a variety of tumor-reactive mAbs linked to distinct cytokines. To date, the majority of clinical progress has been made with ICs that have linked human interleukin-2 (IL2) to a select number of tumor reactive mAbs that had already been in prior clinical testing as non-modified mAbs (Figure 1). Here we briefly review the background for the creation of ICs, summarize current clinical progress, emphasize mechanisms of action for ICs that are distinct from those of their constituent components, and present some directions for future development and testing.

Phase II trial of hu14.18-IL2 for patients with metastatic melanoma

Phase I testing of the hu14.18-IL2 immunocytokine in melanoma patients showed immune activation, reversible toxicities, and a maximal tolerated dose of 7.5 mg/m(2)/day. In this phase II study, 14 patients with measurable metastatic melanoma were scheduled to receive hu14.18-IL2 at 6 mg/m(2)/day as 4-h intravenous infusions on Days 1, 2, and 3 of each 28 day cycle. Patients with stable disease (SD) or regression following cycle 2 could receive two additional treatment cycles. The primary objective was to evaluate antitumor activity and response duration. Secondary objectives evaluated adverse events and immunologic activation. All patients received two cycles of treatment. One patient had a partial response (PR) [1 PR of 14 patients = response rate of 7.1 %; confidence interval, 0.2-33.9 %], and 4 patients had SD and received cycles 3 and 4. The PR and SD responses lasted 3-4 months. All toxicities were reversible and those resulting in dose reduction included grade 3 hypotension (2 patients) and grade 2 renal insufficiency with oliguria (1 patient). Patients had a peripheral blood lymphocytosis on Day 8 and increased C-reactive protein. While one PR in 14 patients met protocol criteria to proceed to stage 2 and enter 16 additional patients, we suspended stage 2 due to limited availability of hu14.18-IL2 at that time and the brief duration of PR and SD. We conclude that subsequent testing of hu14.18-IL2 should involve melanoma patients with minimal residual disease based on compelling preclinical data and the confirmed immune activation with some antitumor activity in this study.

Pharmacokinetics of recombinant bifunctional fusion proteins

INTRODUCTION

The development of biotechnology has enabled the creation of various recombinant fusion proteins as a new class of biotherapeutics. The uniqueness of fusion proteins lies in their ability to fuse two or more protein domains, providing vast opportunities to generate novel combinations of functions. Pharmacokinetic (PK) studies, which are critical components in preclinical and clinical drug development, have not been fully explored for fusion proteins. The lack of general PK models and study guidelines has become a bottleneck for translation of fusion proteins from basic research to the clinic.

AREAS COVERED

This article reviews the current status of PK studies for fusion proteins, covering the processes that affect PK. According to their PK properties, a classification of fusion proteins is suggested along with examples from the clinic or under development. Current limitations and future perspectives for PK of fusion proteins are also discussed.

EXPERT OPINION

A PK model for bifunctional fusion proteins is presented to highlight the importance of mechanistic studies for a thorough understanding of the PK properties of fusion proteins. The model suggests investigating the receptor binding and subsequent intracellular disposition of individual domains, which can have dramatic impact on the PK of fusion proteins.

Ab-IL2 fusion proteins mediate NK cell immune synapse formation by polarizing CD25 to the target cell-effector cell interface

The huKS-IL2 immunocytokine (IC) consists of IL2 fused to a mAb against EpCAM, while the hu14.18-IL2 IC recognizes the GD2 disialoganglioside. They are under evaluation for treatment of EpCAM(+) (ovarian) and GD2(+) (neuroblastoma and melanoma) malignancies because of their proven ability to enhance tumor cell killing by antibody-dependent cell-mediated cytotoxicity (ADCC) and by antitumor cytotoxic T cells. Here, we demonstrate that huKS-IL2 and hu14.18-IL2 bind to tumor cells via their antibody components and increase adhesion and activating immune synapse (AIS) formation with NK cells by engaging the immune cells' IL-2 receptors (IL2R). The NK leukemia cell line, NKL (which expresses high affinity IL2Rs), shows fivefold increase in binding to tumor targets when treated with IC compared to matching controls. This increase in binding is effectively inhibited by blocking antibodies against CD25, the α-chain of the IL2R. NK cells isolated from the peritoneal environment of ovarian cancer patients, known to be impaired in mediating ADCC, bind to huKS-IL2 via CD25. The increased binding between tumor and effector cells via ICs is due to the formation of AIS that are characterized by the simultaneous polarization of LFA-1, CD2 and F-actin at the cellular interface. AIS formation of peritoneal NK and NKL cells is inhibited by anti-CD25 blocking antibody and is 50-200% higher with IC versus the parent antibody. These findings demonstrate that the IL-2 component of the IC allows IL2Rs to function not only as receptors for this cytokine but also as facilitators of peritoneal NK cell binding to IC-coated tumor cells.

Cytokines in cancer immunotherapy

Cytokines are molecular messengers that allow the cells of the immune system to communicate with one another to generate a coordinated, robust, but self-limited response to a target antigen. The growing interest over the past two decades in harnessing the immune system to eradicate cancer has been accompanied by heightened efforts to characterize cytokines and exploit their vast signaling networks to develop cancer treatments. The goal of this paper is to review the major cytokines involved in cancer immunotherapy and discuss their basic biology and clinical applications. The paper will also describe new cytokines in pre-clinical development, combinations of biological agents, novel delivery mechanisms, and potential directions for future investigation using cytokines.

Anti-tumor and immunomodulatory activity of resveratrol in vitro and its potential for combining with cancer immunotherapy

We evaluated the anti-tumor effect of Resveratrol (RV) on M21 and NXS2 tumor cell lines and its immunosuppressive activity on human and murine immune cells to determine the potential for combining RV and immunotherapy. In vitro, concentrations of RV≥25 mcM, inhibited cell proliferation, blocked DNA synthesis and induced G1 phase arrest in tumor and immune cells. RV at 12-50 mcM inhibited antibody dependent cell mediated cytotoxicity (ADCC) of tumor cells facilitated by the hu14.18-IL2 immunocytokine (IC). The in vivo anti-tumor and immunomodulating activity of RV given systemically were assessed in mice. Results showed that this RV regimen inhibited the growth of NXS2 tumors in vivo but did not appear to interfere with blood cell count, splenocyte or macrophage function. Thus, RV may be a candidate for combining with immunotherapy.

Clinical cancer therapy by NK cells via antibody-dependent cell-mediated cytotoxicity

Natural killer (NK) cells are powerful effector cells that can be directed to eliminate tumor cells through tumor-targeted monoclonal antibodies (mAbs). Some tumor-targeted mAbs have been successfully applied in the clinic and are included in the standard of care for certain malignancies. Strategies to augment the antitumor response by NK cells have led to an increased understanding of how to improve their effector responses. Next-generation reagents, such as molecularly modified mAbs and mAb-cytokine fusion proteins (immunocytokines, ICs) designed to augment NK-mediated killing, are showing promise in preclinical and some clinical settings. Continued research into the antitumor effects induced by NK cells and tumor-targeted mAbs suggests that additional intrinsic and extrinsic factors may influence the antitumor response. Therefore more research is needed that focuses on evaluating which NK cell and tumor criteria are best predictive of a clinical response and which combination immunotherapy regimens to pursue for distinct clinical settings.

Induction of potent anti-tumor responses while eliminating systemic side effects via liposome-anchored combinatorial immunotherapy

Immunostimulatory therapies that activate immune response pathways are of great interest for overcoming the immunosuppression present in advanced tumors. Agonistic anti-CD40 antibodies and CpG oligonucleotides have previously demonstrated potent, synergistic anti-tumor effects, but their clinical use even as monotherapies is hampered by dose-limiting inflammatory toxicity provoked upon systemic exposure. We hypothesized that by anchoring immuno-agonist compounds to lipid nanoparticles we could retain the bioactivity of therapeutics in the local tumor tissue and tumor-draining lymph node, but limit systemic exposure to these potent molecules. We prepared PEGylated liposomes bearing surface-conjugated anti-CD40 and CpG and assessed their therapeutic efficacy and systemic toxicity compared to soluble versions of the same immuno-agonists, injected intratumorally in the B16F10 murine model of melanoma. Anti-CD40/CpG-liposomes significantly inhibited tumor growth and induced a survival benefit similar to locally injected soluble anti-CD40 + CpG. Biodistribution analyses following local delivery showed that the liposomal carriers successfully sequestered anti-CD40 and CpG in vivo, reducing leakage into systemic circulation while allowing draining to the tumor-proximal lymph node. Contrary to locally-administered soluble immunotherapy, anti-CD40/CpG-liposomes did not elicit significant increases in serum levels of ALT enzyme, systemic inflammatory cytokines, or overall weight loss, confirming that off-target inflammatory effects had been minimized. The development of a delivery strategy capable of inducing robust anti-tumor responses concurrent with minimal systemic side effects is crucial for the continued progress of potent immunotherapies toward widespread clinical translation.

The anti-tumor effect of resveratrol alone or in combination with immunotherapy in a neuroblastoma model

We investigated the anti-tumor effect of peritumoral resveratrol in combination with immunotherapy in vivo in neuroblastoma-bearing mice. Subcutaneous NXS2 tumors were induced in A/J mice. On day 10, some mice received 15 mcg of intravenous immunocytokine for 5 days, mice received 20 mg of peritumoral resveratrol twice a week (starting on day 12) for a total of 5 injections, and a separate group received a combination of both regimens. Tumor progression and survival were assessed every 3-4 days. Blood and primary tumor tissue samples were collected on day 20 for Complete Blood Count and CD45 immunohistochemistry and histology, respectively. The primary tumor regressed in all mice receiving peritumoral resveratrol. Most of these mice receiving peritumoral resveratrol alone developed metastatic tumors and recurrence of the primary tumor after cessation of therapy. When resveratrol and immunocytokine regimens were combined, 61% of the mice receiving this combination therapy resolved their primary tumors and survived without developing metastatic tumors, compared to 15 and 13% receiving resveratrol or immunocytokine alone, respectively. None of the therapeutic regimes prevented lymphocyte infiltration or affected the complete blood count. Greater necrosis was observed microscopically in tumors from mice receiving the combination therapy. These results demonstrate that the combination therapy of peritumoral resveratrol plus intravenous immunocytokine provides better anti-tumor effects in this model than either therapy alone.

Differential internalization of hu14.18-IL2 immunocytokine by NK and tumor cell: impact on conjugation, cytotoxicity, and targeting

The hu14.18-IL2 (EMD 273063) IC, consisting of a GD(2)-specific mAb genetically engineered to two molecules of IL-2, is in clinical trials for treatment of GD(2)-expressing tumors. Anti-tumor activity of IC in vivo and in vitro involves NK cells. We studied the kinetics of retention of IC on the surface of human CD25(+)CD16(-) NK cell lines (NKL and RL12) and GD(2)(+) M21 melanoma after IC binding to the cells via IL-2R and GD(2), respectively. For NK cells, ∼ 50% of IC was internalized by 3 h and ∼ 90% by 24 h of cell culture. The decrease of surface IC levels on NK cells correlated with the loss of their ability to bind to tumor cells and mediate antibody-dependent cellular cytotoxicity in vitro. Unlike NK cells, M21 cells retained ∼ 70% of IC on the surface following 24 h of culture and maintained the ability to become conjugated and lysed by NK cells. When NKL cells were injected into M21-bearing SCID mice, IT delivery of IC augmented NK cell migration into the tumor. These studies demonstrate that once IC binds to the tumor, it is present on the tumor surface for a prolonged time, inducing the recruitment of NK cells to the tumor site, followed by tumor cell killing.

Targeting PI3K in neuroblastoma

PURPOSE

This work employs pharmacological targeting of phosphoinositide 3-kinases (PI3K) in selected neuroblastoma (NB) tumors with the inhibitor AS605240, which has been shown to express low toxicity and relative specificity for the PI3K species γ.

METHODS

The expression pattern of PI3K isoforms in 7 NB cell lines and 14 tumor patient samples was determined by Western blotting and immunocytochemistry. The effect of AS605240 on the growth of four selected tumor cell lines was assessed. Two cell lines exhibiting (SK-N-LO) or lacking (SK-N-AS) PI3Kγ expression were chosen for further in vitro analysis, which involved propidium iodide (PI)-based cell cycle staining, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL-staining) of apoptotic cells and analysis of PI3K/Akt-related signaling pathways via Western blotting and translocation experiments. The action of AS605240 in vivo was addressed by xenograft experiments in severe combined immunodeficiency (SCID) mice, thereby comparing SK-N-LO and SK-N-AS derived tumors. Apoptosis induced in SK-N-LO tumors was shown by immunohistochemical TUNEL-staining.

RESULTS

Significant expression of PI3Kγ in neuroblastoma patient biopsies and tumor cell lines was detected. AS605240 induced apoptosis in NB cell lines proportional to this expression and suppressed growth of PI3Kγ positive, but not negative, tumors in a xenograft mouse model. No adverse effects of the inhibitor treatment were observed.

CONCLUSIONS

Our observations hint to an oncogenic function of PI3Kγ in distinct neuroblastoma entities and reveal PI3K targeting by AS605240 as a promising molecular therapy of these tumors.

Immunotherapy for neuroblastoma: turning promise into reality

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

Phase I/II open-label study of the biologic effects of the interleukin-2 immunocytokine EMD 273063 (hu14.18-IL2) in patients with metastatic malignant melanoma

Background

To explore the biological activity of EMD 273063 (hu14.18-IL2), a humanized anti-GD2 monoclonal antibody fused to interleukin-2 (IL2), in patients with unresectable, stage IV cutaneous melanoma as measured by induction of immune activation at the tumor site and in peripheral blood.

Methods

Nine patients were treated with 4 mg/m² per day of EMD 273063 given as a 4-h intravenous infusion on days 1, 2, and 3 every four weeks (one cycle). Peripheral blood was analyzed for T cell and natural killer cell phenotype and frequency, as well as levels of soluble IL2 receptor (sIL2R), IL10, IL6, tumor necrosis factor alpha and neopterin. Biopsies of tumor metastasis were performed prior to therapy and at day 10 of the first 2 cycles to study lymphocyte accumulation by immunohistochemistry.

Results

Treatment was generally well tolerated and there were no study drug-related grade 4 adverse events. Grade 3 events were mainly those associated with IL2, most commonly rigors (3 patients) and pyrexia (2 patients). Best response on therapy was stable disease in 2 patients. There were no objective tumor regressions by standard response criteria. Systemic immune activation was demonstrated by increases in serum levels of sIL2R, IL10, and neopterin. There was evidence of increased tumor infiltration by T cells, but not NK cells, in most post-dosing biopsies, suggesting recruitment of immune cells to the tumor site.

Conclusion

EMD 273063 demonstrated biologic activity with increased immune-related cytokines and intratumoral changes in some patients consistent with the suspected mechanism of action of this immunocytokine.

Radiofrequency ablation combined with KS-IL2 immunocytokine (EMD 273066) results in an enhanced antitumor effect against murine colon adenocarcinoma

PURPOSE

Radiofrequency ablation (RFA) is a common treatment modality for surgically unresectable tumors. However, there is a high rate of both local and systemic recurrence.

EXPERIMENTAL DESIGN

In this preclinical study, we sought to enhance the antitumor effect of RFA by combining it with huKS-IL2 immunocytokine [tumor-specific monoclonal antibody fused to interleukin-2 (IL2)] in mice bearing CT26-KS colon adenocarcinoma. Mice were treated with RFA, huKS-IL2 via intratumoral injection, or combination therapy.

RESULTS

Treatment of mice bearing s.c. tumors with RFA and huKS-IL2 resulted in significantly greater tumor growth suppression and enhanced survival compared with mice treated with RFA or huKS-IL2 alone. When subtherapeutic regimens of RFA or huKS-IL2 were used, tumors progressed in all treated mice. In contrast, the combination of RFA and immunocytokine resulted in complete tumor resolution in 50% of mice. Treatment of a tumor with RFA and intratumoral huKS-IL2 also showed antitumor effects against a distant untreated tumor. Tumor-free mice after treatment with RFA and huKS-IL2 showed immunologic memory based on their ability to reject subsequent challenges of CT26-KS and the more aggressive parental CT26 tumors. Flow cytometry analysis of tumor-reactive T cells from mice with complete tumor resolution showed that treatment with RFA and huKS-IL2 resulted in a greater proportion of cytokine-producing CD4 T cells and CD8 T cells compared with mice treated with RFA or huKS-IL2 alone.

CONCLUSIONS

These results show that the addition of huKS-IL2 to RFA significantly enhances the antitumor response in this murine model, resulting in complete tumor resolution and induction of immunologic memory.

The development of antibody-IL-2 based immunotherapy with hu14.18-IL2 (EMD-273063) in melanoma and neuroblastoma

Patients with high risk melanoma and neuroblastoma frequently experience recurrence despite surgical resection and appropriate adjuvant therapies. Immunotherapy with the immunocytokine hu14.18-IL2 (EMD-273063) was developed by means of fusion of two molecules of IL-2 to the monoclonal antibody, 14.18, that recognizes GD2, expressed on the earlier mentioned malignancies. This article will discuss the results of preclinical work using EMD-273063 therapy, including data suggesting that intratumoral therapy may have enhanced antitumor benefit compared with intravenous therapy. Initial clinical trials in adult melanoma and pediatric neuroblastoma have demonstrated acceptable toxicity profiles in dosing that induces immune activation. Preclinical and initial clinical data suggest greater efficacy in the setting of minimal residual disease; therefore, future clinical testing is planned to test the benefit of EMD-273063 in this setting.

Modern Technologies for Creating Synthetic Antibodies for Clinical application

The modular structure and versatility of antibodies enables one to modify natural immunoglobulins in different ways for various clinical applications. Rational design and molecular engineering make it possible to directionally modify the molecular size, affinity, specificity, and immunogenicity and effector functions of an antibody, as well as to combine them with other functional agents. This review focuses on up-to-date methods of antibody engineering for diagnosing and treating various diseases, particularly on new technologies meant to refine the effector functions of therapeutic antibodies.