Trial watch: Tumor-targeting monoclonal antibodies for oncological indications

A Chemically Defined TLR3 Agonist with Anticancer Activity

Toll-like receptor 3 (TLR3) agonists such as polyinosinic:polycytidylic acid (poly(I:C)) have immunostimulatory effects that can be taken advantage of to induce anticancer immune responses in preclinical models. In addition, poly(I:C) has been introduced into clinical trials to demonstrate its efficacy as an adjuvant and to enhance the immunogenicity of locally injected tumors, thus reverting resistance to PD-L1 blockade in melanoma patients. Here, we report the pharmacokinetic, pharmacodynamic, mechanistic and toxicological profile of a novel TLR3 agonist, TL-532, a chemically synthesized double-stranded RNA that is composed by blocks of poly(I:C) and poly(A:U) (polyadenylic - polyuridylic acid). In preclinical models, we show that TL-532 is bioavailable after parenteral injection, has an acceptable toxicological profile, and stimulates the production of multiple chemokines and interleukins that constitute pharmacodynamic markers of its immunostimulatory action. When given at a high dose, TL-532 monotherapy reduced the growth of bladder cancers growing on mice. In addition, in immunodeficient mice lacking formylpeptide receptor-1 (FPR1), TL-532 was able to restore the response of orthotopic subcutaneous fibrosarcoma to immunogenic chemotherapy. Altogether, these findings may encourage further development of TL-532 as an immunotherapeutic anticancer agent.

Inhibitory receptors for HLA class I as immune checkpoints for natural killer cell-mediated antibody-dependent cellular cytotoxicity in cancer immunotherapy

Natural killer (NK) cells mediate potent anti-tumor responses, which makes them attractive targets for immunotherapy. The anti-tumor response of endogenous- or allogeneic NK cells can be enhanced through clinically available monoclonal antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC). NK cell activation is regulated by interaction of inhibitory receptors with classical- and non-classical human leukocyte antigens (HLA) class I molecules. Inhibitory receptors of the killer immunoglobulin-like receptor (KIR) family interact with HLA-A, -B or -C epitopes, while NKG2A interacts with the non-classical HLA-E molecule. Both types of inhibitory interactions may influence the strength of the ADCC response. In the present review, we provide an overview of the effect of inhibitory KIRs and NKG2A on NK cell-mediated ADCC, which highlights the rationale for combination strategies with ADCC triggering antibodies and interference with the NK cell relevant inhibitory immune checkpoints, such as KIR and NKG2A.

Dying of Stress: Chemotherapy, Radiotherapy, and Small-Molecule Inhibitors in Immunogenic Cell Death and Immunogenic Modulation

Innovative strategies to re-establish the immune-mediated destruction of malignant cells is paramount to the success of anti-cancer therapy. Accumulating evidence suggests that radiotherapy and select chemotherapeutic drugs and small molecule inhibitors induce immunogenic cell stress on tumors that results in improved immune recognition and targeting of the malignant cells. Through immunogenic cell death, which entails the release of antigens and danger signals, and immunogenic modulation, wherein the phenotype of stressed cells is altered to become more susceptible to immune attack, radiotherapies, chemotherapies, and small-molecule inhibitors exert immune-mediated anti-tumor responses. In this review, we discuss the mechanisms of immunogenic cell death and immunogenic modulation and their relevance in the anti-tumor activity of radiotherapies, chemotherapies, and small-molecule inhibitors. Our aim is to feature the immunological aspects of conventional and targeted cancer therapies and highlight how these therapies may be compatible with emerging immunotherapy approaches.

Tumor factors stimulate lysosomal degradation of tumor antigens and undermine their cross-presentation in lung cancer

Activities of dendritic cells (DCs) that present tumor antigens are often suppressed in tumors. Here we report that this suppression is induced by tumor microenvironment-derived factors, which activate the activating transcription factor-3 (ATF3) transcription factor and downregulate cholesterol 25-hydroxylase (CH25H). Loss of CH25H in antigen presenting cells isolated from human lung tumors is associated with tumor growth and lung cancer progression. Accordingly, mice lacking CH25H in DCs exhibit an accelerated tumor growth, decreased infiltration and impaired activation of intratumoral CD8+ T cells. These mice do not establish measurable long-term immunity against malignant cells that undergo chemotherapy-induced immunogenic cell death. Mechanistically, downregulation of CH25H stimulates membrane fusion between endo-phagosomes and lysosomes, accelerates lysosomal degradation and restricts cross-presentation of tumor antigens in the intratumoral DCs. Administration of STING agonist MSA-2 reduces the lysosomal activity in DCs, restores antigen cross presentation, and increases therapeutic efficacy of PD-1 blockade against tumour challenge in a CH25H-dependent manner. These studies highlight the importance of downregulation of CH25H in DCs for tumor immune evasion and resistance to therapy.

Monoclonal antibodies for the treatment of acute lymphocytic leukemia: A literature review

BACKGROUND

Acute lymphocytic leukemia (ALL) is a type of blood cancer that is more prevalent in children. Several treatment methods are available for ALL, including chemotherapy, upfront treatment regimens, and pediatric-inspired regimens for adults. Monoclonal antibodies (Mabs) are the novel Food and Drug Administration (FDA) approved remedies for the relapsed/refractory (R/R) adult ALL. In this article, we aimed to review studies that investigated the efficacy and safety of Mabs on ALL.

METHODS

We gathered studies through a complete search with all proper related keywords in ISI Web of Science, SID, Scopus, Google Scholar, Science Direct, and PubMed for English language publications up to 2020.

RESULTS

The most commonly studied Mabs for ALL therapies are CD-19, CD-20, CD-22, and CD-52. The best results have been reported in the administration of blinatumomab, rituximab, ofatumumab, and inotuzumab with acceptable low side effects.

CONCLUSION

Appling personalized approach for achieving higher efficacy is one of the most important aspects of treatment. Moreover, we recommend that the wide use of these Mabs depends on designing further cost-effectiveness trials in this field.

Immunogenic cell death and its therapeutic or prognostic potential in high-grade glioma

Immunogenic cell death (ICD) has emerged as a key component of therapy-induced anti-tumor immunity. Over the past few years, ICD was found to play a pivotal role in a wide variety of novel and existing treatment modalities. The clinical application of these techniques in cancer treatment is still in its infancy. Glioblastoma (GBM) is the most lethal primary brain tumor with a dismal prognosis despite maximal therapy. The development of new therapies in this aggressive type of tumors remains highly challenging partially due to the cold tumor immune environment. GBM could therefore benefit from ICD-based therapies stimulating the anti-tumor immune response. In what follows, we will describe the mechanisms behind ICD and the ICD-based (pre)clinical advances in anticancer therapies focusing on GBM.

Decreased DHRS1 expression is a novel predictor of poor survival in patients with hepatocellular carcinoma

Aim: To investigate the effect of aberrant expression of DHRS1 on hepatocellular carcinoma (HCC). Materials & methods: Kaplan-Meier and Cox regression analyses were performed to evaluate the correlation between DHRS1 and overall survival. Gene set enrichment analysis was performed to explore the potential function of DHRS1 in HCC. Results: Multiple data analysis revealed that DHRS1 mRNA and protein expression level were remarkably lower in HCC than that in normal tissues. In survival analysis, patients with low DHRS1 expression presented a poorer prognosis, and was an independent risk factor for HCC. Conclusion: Decreased DHRS1 expression may be a potential predictor of poor prognosis in HCC.

Immunotherapeutic Strategies for Canine Lymphoma: Changing the Odds Against Non-Hodgkin Lymphoma

The new era of immune-oncology has brought complexities and challenges that emphasize the need to identify new strategies and models to develop successful and cost-effective therapies. The inclusion of a canine model in the drug development of cancer immunotherapies is being widely recognized as a valid solution to overcome several hurdles associated with conventional preclinical models. Driven by the success of immunotherapies in the treatment of human non-Hodgkin lymphoma (NHL) and by the remarkable similarities of canine NHL to its human counterpart, canine NHL has been one of the main focus of comparative research. Under the present review, we summarize a general overview of the challenges and prospects of today's cancer immunotherapies and the role that comparative medicine might play in solving the limitations brought by this rapidly expanding field. The state of art of both human and canine NHL and the rationale behind the use of the canine model to bridge the translational gap between murine preclinical studies and human clinical trials are addressed. Finally, a review of currently available immunotherapies for canine NHL is described, highlighting the potential of these therapeutic options.

Therapeutic peptides for chemotherapy: Trends and challenges for advanced delivery systems

The past decades witnessed an increasing interest in peptides as clinical therapeutics. Rightfully considered as a potential alternative for small molecule therapy, these remarkable pharmaceuticals can be structurally fine-tuned to impact properties such as high target affinity, selectivity, low immunogenicity along with satisfactory tissue penetration. Although physicochemical and pharmacokinetic challenges have mitigated, to some extent, the clinical applications of therapeutic peptides, their potential impact on modern healthcare remains encouraging. According to recent reports, there are more than 400 peptides under clinical trials and 60 were already approved for clinical use. As the demand for efficient and safer therapy became high, especially for cancers, peptides have shown some exciting developments not only due to their potent antiproliferative action but also when used as adjuvant therapies, either to decrease side effects with tumor-targeted therapy or to enhance the activity of anticancer drugs via transbarrier delivery. The first part of the present review gives an insight into challenges related to peptide product development. Both molecular and formulation approaches intended to optimize peptide's pharmaceutical properties are covered, and some of their current issues are highlighted. The second part offers a comprehensive overview of the emerging applications of therapeutic peptides in chemotherapy from bioconjugates to nanovectorized therapeutics.

Identification and functional study of novel oligonucleotides: CpG Seq 13 and CpG Seq 19

Aim: This study explored new immunoadjuvants with stronger immune activity to enhance therapeutic effects against leukemia. Materials & methods: Whole blood and bone marrow of acute myeloid leukemia (AML) patients and healthy volunteers were collected. Isolated mononuclear cells were treated with two newly designed CpG oligodeoxynucleotides, CpG sequence 13 and 19, and known CpG oligodeoxynucleotides and analyzed via flow cytometry. Results: CpG Seq 13 and 19 possess strong immune activation and enhance the proliferation, degranulation and cytotoxicity of T cells. They also inhibit AML cell proliferation. When CpG Seq 13/19 are combined with anti-OX40 antibodies, the cytotoxicity of T cells on AML cells are further enhanced. Conclusion: CpG Seq 13 and 19 are strong immune adjuvant candidates for AML treatment.

Primary and metastatic breast tumors cross-talk to influence immunotherapy responses

The presence of a tumor can alter host immunity systematically. The immune-tumor interaction in one site may impact the local immune microenvironment in distal tissues through the circulation, and therefore influence the efficacy of immunotherapies to distant metastases. Improved understanding of the immune-tumor interactions during immunotherapy treatment in a metastatic setting may enhance the efficacy of current immunotherapies. Here we investigate the response to αPD-1/αCTLA4 and trimAb (αDR5, α4-1BB, αCD40) of 67NR murine breast tumors grown simultaneously in the mammary fat pad (MFP) and lung, a common site of breast cancer metastasis, and compared to tumors grown in isolation. Lung tumors present in isolation were resistant to both therapies. However, in MFP and lung tumor-bearing mice, the presence of a MFP tumor could increase lung tumor response to immunotherapy and decrease the number of lung metastases, leading to complete eradication of lung tumors in a proportion of mice. The MFP tumor influence on lung metastases was mediated by CD8⁺ T cells, as CD8⁺ T cell depletion abolished the difference in lung metastases. Furthermore, mice with concomitant MFP and lung tumors had increased tumor specific, effector CD8⁺ T cells infiltration in the lungs. Thus, we propose a model where tumors in an immunogenic location can give rise to systemic anti-tumor CD8⁺ T cell responses that could be utilized to target metastatic tumors. These results highlight the requirement for clinical consideration of cross-talk between primary and metastatic tumors for effective immunotherapy for cancers otherwise resistant to immunotherapy.

Development and clinical application of bispecific antibody in the treatment of colorectal cancer

INTRODUCTION

Treatment of colorectal cancer as one of the most commonly diagnosed and a frequent cause of cancer-related deaths is of great challenges in health-related issues.

AREAS COVERED

Immunotherapy is the fourth pillar of cancer treatment which provides more novel therapeutic options with expanding investigational potentials. One of the modalities in immunotherapy is the use of bispecific antibodies. Despite demonstrating many promising roles, it still needs more advanced studies to identify the actual pros and cons. In this review, the application of bispecific antibody in the treatment of colorectal cancer has been explained, based on preclinical and clinical studies. The literature search was conducted mainly through PubMed in June and September 2019.

EXPERT OPINION

Bispecific antibody is in its early stages in colorectal cancer treatment, requiring modern technologies in manufacturing, better biomarkers and more specific target antigens, more studies on individual genetic variations, and conducting later phase clinical trials and systematic reviews to achieve better survival benefits.

Whole Transcriptomic Analysis of Apigenin on TNFα Immuno-activated MDA-MB-231 Breast Cancer Cells

BACKGROUND

Triple-negative breast cancer is categorized by a lack of hormone receptors, inefficacy of anti-estrogen or aromatase inhibitor chemotherapies and greater mortality rates in African American populations. Advanced-stage breast tumors have a high concentration of tumor necrosis factor-α (TNFα) throughout the tumor/stroma milieu, prompting sustained release of diverse chemokines (i.e. C-C motif chemokine ligand 2 (CCL2)/CCL5). These potent chemokines can subsequently direct mass infiltration of leukocyte sub-populations to lodge within the tumor, triggering a loss of tumor immune surveillance and subsequent rapid tumor growth. Previously, we demonstrated that in the MDA-MB-231 TNBC cell line, TNFα evoked a rise in immune signaling proteins: CCL2, granulocyte macrophage colony-stimulating factor, interleukin (IL)1α, IL6 and inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKBKε) all of which were attenuated by apigenin, a dietary flavonoid found in chamomile and parsley.

MATERIALS AND METHODS

The present work elucidates changes evoked by TNFα in the presence or absence of apigenin by examining the entire transcriptome for mRNA and long intergenic non-coding RNA with Affymetrix Hugene-2.1_ST human microarrays. Differential gene-expression analysis was conducted on 48,226 genes.

RESULTS

TNFα caused up-regulation of 75 genes and down-regulation of 10. Of these, apigenin effectively down-regulated 35 of the 75 genes which were up-regulated by TNFα. These findings confirm our previous work, specifically for the TNFα-evoked spike in IL1A vs. untreated controls [+21-fold change (FC), p<0.0001] being attenuated by apigenin in the presence of TNFa (-15 FC vs. TNFα, p<0.0001). Similar trends were seen for apigenin-mediated down-regulation of TNFα-up-regulated transcripts: IKBKE (TNFα: 4.55 FC vs. control, p<0.001; and TNFα plus apigenin: -4.92 FC, p<0.001), CCL2 (2.19 FC, p<0.002; and -2.12 FC, p<0.003), IL6 (3.25 FC, p<0.020; and -2.85 FC, p<0.043) and CSF2 (TNFα +6.04 FC, p<0.001; and -2.36 FC, p<0.007). In addition, these data further establish more than a 65% reduction by apigenin for the following transcripts which were also up-regulated by TNFα: cathepsin S (CTSS), complement C3 (C3), laminin subunit gamma 2 (LAMC2), (TLR2), toll-like receptor 2 G protein-coupled receptor class C group 5 member B (GPRC5B), contactin-associated protein 1 (CNTNAP1), claudin 1 (CLDN1), nuclear factor of activated T-cells 2 (NFATC2), C-X-C motif chemokine ligand 10 (CXCL10), CXCL11, interleukin 1 receptor-associated kinase 3 (IRAK3), nuclear receptor subfamily 3 group C member 2 (NR3C2), interleukin 32 (IL32), IL24, slit guidance ligand 2 (SLIT2), transmembrane protein 132A (TMEM132A), TMEM171, signal transducing adaptor family member 2 (STAP2), mixed lineage kinase domain-like pseudokinase (MLKL), kinase insert domain receptor (KDR), BMP-binding endothelial regulator (BMPER), and kelch-like family member 36 (KLHL36).

CONCLUSION

There is a possible therapeutic role for apigenin in down-regulating diverse genes associated with tumorigenic leukocyte sub-population infiltration by triple-negative breast cancer. The data have been deposited into the Gene Expression Omnibus for public analysis at https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE120550.

Therapeutic targeting of macrophages enhances chemotherapy efficacy by unleashing type I interferon response

Recent studies have revealed a role for macrophages and neutrophils in limiting chemotherapy efficacy; however, the mechanisms underlying the therapeutic benefit of myeloid-targeting agents in combination with chemotherapy are incompletely understood. Here, we show that targeting tumour-associated macrophages by colony-stimulating factor-1 receptor (CSF-1R) blockade in the K14cre;Cdh1^F/F;Trp53^F/F transgenic mouse model for breast cancer stimulates intratumoural type I interferon (IFN) signalling, which enhances the anticancer efficacy of platinum-based chemotherapeutics. Notably, anti-CSF-1R treatment also increased intratumoural expression of type I IFN-stimulated genes in patients with cancer, confirming that CSF-1R blockade is a powerful strategy to trigger an intratumoural type I IFN response. By inducing an inflamed, type I IFN-enriched tumour microenvironment and by further targeting immunosuppressive neutrophils during cisplatin therapy, antitumour immunity was activated in this poorly immunogenic breast cancer mouse model. These data illustrate the importance of breaching multiple layers of immunosuppression during cytotoxic therapy to successfully engage antitumour immunity in breast cancer.

Phase Ib/II Study of Pembrolizumab and Pegylated-Interferon Alfa-2b in Advanced Melanoma

PURPOSE

Objective responses are reported in 34% to 37% of patients with programmed death-1 (PD-1)-naïve advanced melanoma treated with PD-1 inhibitors. Pre-existing CD8+ T-cell infiltrate and interferon (IFN) gene signature correlate with response to PD-1 blockade. Here, we report a phase Ib/II study of pembrolizumab/pegylated (PEG)-IFN combination in PD-1-naïve advanced melanoma.

PATIENTS AND METHODS

PEG-IFN (1, 2, and 3 μg/kg per week) was dose escalated using a modified toxicity probability interval design in three cohorts of four patients each, whereas pembrolizumab was dosed at 2 mg/kg every 3 weeks in the phase Ib portion. Thirty-one patients were enrolled in the phase II portion. Primary objectives were safety and incidence of dose-limiting toxicities. Secondary objectives included objective response rate, progression-free survival (PFS), and overall survival.

RESULTS

Forty-three patients with stage IV melanoma were enrolled in the phase Ib and II portions of the study and included in the analysis. At the data cutoff date (December 31, 2017), median follow-up duration was 25 months (range, 1 to 38 months). All 43 patients experienced at least one adverse event; grade 3/4 treatment-related adverse events occurred in 21 of 43 patients (48.8%). Objective responses were seen at all three dose levels among 43 evaluable patients. The objective response rate was 60.5%, with 46.5% of patients exhibiting ongoing response. Median PFS was 11.0 months in all patients and unreached in responders, whereas median overall survival remained unreached in all patients. The 2-year PFS rate was 46%.

CONCLUSION

Pembrolizumab/PEG-IFN demonstrated an acceptable toxicity profile with promising evidence of clinical efficacy in PD-1-naïve metastatic melanoma. These results support the rationale to further investigate this pembrolizumab/PEG-IFN combination in this disease.

Preclinical evaluation of a MAGE-A3 vaccination utilizing the oncolytic Maraba virus currently in first-in-human trials

Multiple immunotherapeutics have been approved for cancer patients, however advanced solid tumors are frequently refractory to treatment. We evaluated the safety and immunogenicity of a vaccination approach with multimodal oncolytic potential in non-human primates (NHP) (Macaca fascicularis). Primates received a replication-deficient adenoviral prime, boosted by the oncolytic Maraba MG1 rhabdovirus. Both vectors expressed the human MAGE-A3. No severe adverse events were observed. Boosting with MG1-MAGEA3 induced an expansion of hMAGE-A3-specific CD4⁺ and CD8⁺ T-cells with the latter peaking at remarkable levels and persisting for several months. T-cells reacting against epitopes fully conserved between simian and human MAGE-A3 were identified. Humoral immunity was demonstrated by the detection of circulating MAGE-A3 antibodies. These preclinical data establish the capacity for the Ad:MG1 vaccination to engage multiple effector immune cell populations without causing significant toxicity in outbred NHPs. Clinical investigations utilizing this program for the treatment of MAGE-A3-positive solid malignancies are underway (NCT02285816, NCT02879760).

Trial Watch: Oncolytic viro-immunotherapy of hematologic and solid tumors

Oncolytic viruses selectively target and kill cancer cells in an immunogenic fashion, thus supporting the establishment of therapeutically relevant tumor-specific immune responses. In 2015, the US Food and Drug Administration (FDA) approved the oncolytic herpes simplex virus T-VEC for use in advanced melanoma patients. Since then, a plethora of trials has been initiated to assess the safety and efficacy of multiple oncolytic viruses in patients affected with various malignancies. Here, we summarize recent preclinical and clinical progress in the field of oncolytic virotherapy.

Tumor immunotherapy: New aspects of natural killer cells

A group of impressive immunotherapies for cancer treatment, including immune checkpoint-blocking antibodies, gene therapy and immune cell adoptive cellular immunotherapy, have been established, providing new weapons to fight cancer. Natural killer (NK) cells are a component of the first line of defense against tumors and virus infections. Studies have shown dysfunctional NK cells in patients with cancer. Thus, restoring NK cell antitumor functionality could be a promising therapeutic strategy. NK cells that are activated and expanded ex vivo can supplement malfunctional NK cells in tumor patients. Therapeutic antibodies, chimeric antigen receptor (CAR), or bispecific proteins can all retarget NK cells precisely to tumor cells. Therapeutic antibody blockade of the immune checkpoints of NK cells has been suggested to overcome the immunosuppressive signals delivered to NK cells. Oncolytic virotherapy provokes antitumor activity of NK cells by triggering antiviral immune responses. Herein, we review the current immunotherapeutic approaches employed to restore NK cell antitumor functionality for the treatment of cancer.

Trial watch: DNA-based vaccines for oncological indications

DNA-based vaccination is a promising approach to cancer immunotherapy. DNA-based vaccines specific for tumor-associated antigens (TAAs) are indeed relatively simple to produce, cost-efficient and well tolerated. However, the clinical efficacy of DNA-based vaccines for cancer therapy is considerably limited by central and peripheral tolerance. During the past decade, considerable efforts have been devoted to the development and characterization of novel DNA-based vaccines that would circumvent this obstacle. In this setting, particular attention has been dedicated to the route of administration, expression of modified TAAs, co-expression of immunostimulatory molecules, and co-delivery of immune checkpoint blockers. Here, we review preclinical and clinical progress on DNA-based vaccines for cancer therapy.

Synergistic inhibitory effects of an engineered antibody-like molecule ATF-Fc and trastuzumab on tumor growth and invasion in a human breast cancer xenograft mouse model

The overexpression of the oncogene human epidermal growth factor receptor 2 (HER-2) has been associated with decreased disease-free survival and is a marker of poor prognosis of invasive breast cancer. Although the high efficacy of trastuzumab, a drug that targets the HER-2 oncogene, has been widely recognized, the efficiency of the treatment remains at ~30%. Therefore, novel effective treatments are required for patients with recurrent metastatic breast cancer. The present study aimed to investigate the effects of an engineered antibody-like molecule administered alone or in combination with trastuzumab on the tumor growth and metastasis of HER-2-positive breast cancer. Another aim was to investigate novel cancer therapies for HER-2-positive breast cancer. The engineered antibody-like molecule consists of the amino-terminal fragment (ATF) of human urokinase-type plasminogen (uPA) and is conjugated with the Fc fragment of human immunoglobulin G1 (ATF-Fc). The anti-cancer effect of ATF-Fc (alone and in combination with trastuzumab) on tumor cells and in a nude mouse tumor model was evaluated by detecting the expression of uPA, urokinase plasminogen activator receptor (uPAR) and HER-2. In vitro experiments demonstrated that specifically blocking the uPA-uPAR and HER-2 signaling pathways may effectively promote the apoptosis of breast cancer cells. Additionally, ATF-Fc-induced cell death in HER-2-positive breast cancer cells was observed in vivo. When ATF-Fc was administered in combination with trastuzumab, cell death was increased and breast cancer metastasis was reduced. The novel engineered antibody-like molecule ATF-Fc was able to inhibit HER-2-positive breast cancer cell growth and metastasis by interfering with uPA and its receptor (uPA-uPAR) system. Additionally, the antibody-like molecule exhibits a synergistic inhibitory effect when administered in combination with trastuzumab.

Novel PSCA targeting scFv-fusion proteins for diagnosis and immunotherapy of prostate cancer

PURPOSE

Despite great progress in the diagnosis and treatment of localized prostate cancer (PCa), there remains a need for new diagnostic markers that can accurately distinguish indolent and aggressive variants. One promising approach is the antibody-based targeting of prostate stem cell antigen (PSCA), which is frequently overexpressed in PCa. Here, we show the construction of a molecular imaging probe comprising a humanized scFv fragment recognizing PSCA genetically fused to an engineered version of the human DNA repair enzyme O6-alkylguanine-DNA alkyltransferase (AGT), the SNAP-tag, enabling specific covalent coupling to various fluorophores for diagnosis of PCa. Furthermore, the recombinant immunotoxin (IT) PSCA(scFv)-ETA' comprising the PSCA(scFv) and a truncated version of Pseudomonas exotoxin A (PE, ETA') was generated.

METHODS

We analyzed the specific binding and internalization behavior of the molecular imaging probe PSCA(scFv)-SNAP in vitro by flow cytometry and live cell imaging, compared to the corresponding IT PSCA(scFv)-ETA'. The cytotoxic activity of PSCA(scFv)-ETA' was tested using cell viability assays. Specific binding was confirmed on formalin-fixed paraffin-embedded tissue specimen of early and advanced PCa.

RESULTS

Alexa Fluor® 647 labeling of PSCA(scFv)-SNAP confirmed selective binding to PSCA, leading to rapid internalization into the target cells. The recombinant IT PSCA(scFv)-ETA' showed selective binding leading to internalization and efficient elimination of target cells.

CONCLUSIONS

Our data demonstrate, for the first time, the specific binding, internalization, and cytotoxicity of a scFv-based fusion protein targeting PSCA. Immunohistochemical staining confirmed the specific ex vivo binding to primary PCa material.

Trial watch: Immune checkpoint blockers for cancer therapy

Immune checkpoint blockers (ICBs) are literally revolutionizing the clinical management of an ever more diversified panel of oncological indications. Although considerable attention persists around the inhibition of cytotoxic T lymphocyte-associated protein 4 (CTLA4) and programmed cell death 1 (PDCD1, best known as PD-1) signaling, several other co-inhibitory T-cell receptors are being evaluated as potential targets for the development of novel ICBs. Moreover, substantial efforts are being devoted to the identification of biomarkers that reliably predict the likelihood of each patient to obtain clinical benefits from ICBs in the absence of severe toxicity. Tailoring the delivery of specific ICBs or combinations thereof to selected patient populations in the context of precision medicine programs constitutes indeed a major objective of the future of ICB-based immunotherapy. Here, we discuss recent preclinical and clinical advances on the development of ICBs for oncological indications.

Trial Watch: Immunostimulatory monoclonal antibodies for oncological indications

The goal of cancer immunotherapy is to establish new or boost pre-existing anticancer immune responses that eradicate malignant cells while generating immunological memory to prevent disease relapse. Over the past few years, immunomodulatory monoclonal antibodies (mAbs) that block co-inhibitory receptors on immune effectors cells - such as cytotoxic T lymphocyte-associated protein 4 (CTLA4), programmed cell death 1 (PDCD1, best known as PD-1) - or their ligands - such as CD274 (best known as PD-L1) - have proven very successful in this sense. As a consequence, many of such immune checkpoint blockers (ICBs) have already entered the clinical practice for various oncological indications. Considerable attention is currently being attracted by a second group of immunomodulatory mAbs, which are conceived to activate co-stimulatory receptors on immune effector cells. Here, we discuss the mechanisms of action of these immunostimulatory mAbs and summarize recent progress in their preclinical and clinical development.

Trial Watch: Adoptively transferred cells for anticancer immunotherapy

Immunotherapies aimed at strengthening immune effector responses against malignant cells are growing at exponential rates. Alongside, the impressive benefits obtained by patients with advanced melanoma who received adoptively transferred tumor-infiltrating lymphocytes (TILs) have encouraged the scientific community to pursue adoptive cell transfer (ACT)-based immunotherapy. ACT involves autologous or allogenic effector lymphocytes that are generally obtained from the peripheral blood or resected tumors, expanded and activated ex vivo, and administered to lymphodepleted patients. ACT may be optionally associated with chemo- and/or immunotherapeutics, with the overall aim of enhancing the proliferation, persistence and functionality of infused cells, as well as to ensure their evolution in an immunological permissive local and systemic microenvironment. In addition, isolated lymphocytes can be genetically engineered to endow them with the ability to target a specific tumor-associated antigen (TAA), to increase their lifespan, and/or to reduce their potential toxicity. The infusion of chimeric antigen receptor (CAR)-expressing cytotoxic T lymphocytes redirected against CD19 has shown promising clinical efficacy in patients with B-cell malignancies. Accordingly, the US Food and Drug Administration (FDA) has recently granted 'breakthrough therapy' designation to a CAR-based T-cell therapy (CTL019) for patients with B-cell malignancies. Considerable efforts are now being devoted to the development of efficient ACT-based immunotherapies for non-hematological neoplasms. In this Trial Watch, we summarize recent clinical advances on the use of ACT for oncological indications.

Reconceptualizing cancer immunotherapy based on plant production systems

Plants can be used as inexpensive and facile production platforms for vaccines and other biopharmaceuticals. More recently, plant-based biologics have expanded to include cancer immunotherapy agents. The following review describes the current state of the art for plant-derived strategies to prevent or reduce cancers. The review discusses avenues taken to prevent infection by oncogenic viruses, solid tumors and lymphomas. Strategies including cancer vaccines, monoclonal antibodies and virus nanoparticles are described, and examples are provided. The review ends with a discussion of the implications of plant-based cancer immunotherapy for developing countries.

Cancer immunotherapy has made great strides over recent years. This review describes the use of plants as production systems to produce biopharmaceuticals such as vaccines and antibodies to treat a wide variety of cancers. The use of nanoparticle technology based on plant viruses as a novel strategy to target and combat cancers is also included. The review concludes with a discussion of plant production platforms and their relevance for the generation of cheap and effective cancer immunotherapies for developing countries.

Trial watch: Dendritic cell-based anticancer immunotherapy

Dendritic cell (DC)-based vaccines against cancer have been extensively developed over the past two decades. Typically DC-based cancer immunotherapy entails loading patient-derived DCs with an appropriate source of tumor-associated antigens (TAAs) and efficient DC stimulation through a so-called "maturation cocktail" (typically a combination of pro-inflammatory cytokines and Toll-like receptor agonists), followed by DC reintroduction into patients. DC vaccines have been documented to (re)activate tumor-specific T cells in both preclinical and clinical settings. There is considerable clinical interest in combining DC-based anticancer vaccines with T cell-targeting immunotherapies. This reflects the established capacity of DC-based vaccines to generate a pool of TAA-specific effector T cells and facilitate their infiltration into the tumor bed. In this Trial Watch, we survey the latest trends in the preclinical and clinical development of DC-based anticancer therapeutics. We also highlight how the emergence of immune checkpoint blockers and adoptive T-cell transfer-based approaches has modified the clinical niche for DC-based vaccines within the wide cancer immunotherapy landscape.

Effective Integration of Targeted Tumor Imaging and Therapy Using Functionalized InP QDs with VEGFR2 Monoclonal Antibody and miR-92a Inhibitor

Rapid diagnosis and targeted drug treatment require agents that possess multiple functions. Nanomaterials that facilitate optical imaging and direct drug delivery have shown great promise for effective cancer treatment. In this study, we first modified near-infrared fluorescent indium phosphide quantum dots (InP QDs) with a vascular endothelial growth factor receptor 2 (VEGFR2) monoclonal antibody to afford targeted drug delivery function. Then, a miR-92a inhibitor, an antisense microRNA that enhances the expression of tumor suppressor p63, was attached to the VEGFR2-InP QDs via electrostatic interactions. The functionalized InP nanocomposite (IMAN) selectively targets tumor sites and allows for infrared imaging in vivo. We further explored the mechanism of this active targeting. The IMAN was endocytosed and delivered in the form of microvesicles via VEGFR2-CD63 signaling. Moreover, the IMAN induced apoptosis of human myelogenous leukemia cells through the p63 pathway in vitro and in vivo. These results indicate that the IMAN may provide a new and promising chemotherapy strategy against cancer cells, particularly by its active targeting function and utility in noninvasive three-dimensional tumor imaging.

Pro-necrotic molecules impact local immunosurveillance in human breast cancer

Necrosis culminates in spilling cellular content through the permeabilized plasma membrane, thereby releasing potentially immunostimulatory molecules in the pericellular space of dead cells. Accordingly, molecules involved in necroptotic signaling, such as receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase-like (MLKL) have been found to stimulate anticancer immune responses in mouse models of chemotherapy. mRNAs encoding prominent pro-necrotic gene products (RIPK1, RIPK3, MLKL, PGAM5 and DFNA5) were correlated with immune-related metagenes in several cancer types (breast, colorectal, lung, ovary, melanoma), revealing the strongest associations in breast cancer. In two independent breast cancer cohorts, the expression of MLKL and DFNA5 was decreased at the mRNA levels in tumor as compared with normal tissues. Moreover, MLKL expression exhibited a strong positive correlation with genes reflecting the presence of B, NK and T lymphocytes in the tumor bed, in multiple distinct breast cancer subtypes. In contrast, the positive correlation between RIPK3 and lymphoid cells was restricted to HER2⁺ and triple negative/basal-like breast cancer. Moreover, the expression of DFNA5, which mediates post-apoptotic secondary necrosis, mostly correlated with the monocytic lineage and macrophages in ER⁺/luminal A breast cancers. MLKL (and to some extent RIPK1 and RIPK3) was strongly associated with the local expression of genes involved in interferon-α and interferon-γ responses. Altogether, these results support the idea that pro-necrotic signaling facilitates intratumoral immune responses in human breast cancer.

In vivo evaluation of a novel format of a bivalent HER3-targeting and albumin-binding therapeutic affibody construct

Overexpression of human epidermal growth factor receptor 3 (HER3) is involved in resistance to several therapies for malignant tumours. Currently, several anti-HER3 monoclonal antibodies are under clinical development. We introduce an alternative approach to HER3-targeted therapy based on engineered scaffold proteins, i.e. affibody molecules. We designed a small construct (22.5 kDa, denoted 3A3), consisting of two high-affinity anti-HER3 affibody molecules flanking an albumin-binding domain ABD, which was introduced for prolonged residence in circulation. In vitro, 3A3 efficiently inhibited growth of HER3-expressing BxPC-3 cells. Biodistribution in mice was measured using 3A3 that was site-specifically labelled with ¹¹¹In via a DOTA chelator. The residence time of ¹¹¹In-DOTA-3A3 in blood was extended when compared with the monomeric affibody molecule. ¹¹¹In-DOTA-3A3 accumulated specifically in HER3-expressing BxPC-3 xenografts in mice. However, ¹¹¹In-DOTA-3A3 cleared more rapidly from blood than a size-matched control construct ¹¹¹In-DOTA-TAT, most likely due to sequestering of 3A3 by mErbB3, the murine counterpart of HER3. Repeated dosing and increase of injected protein dose decreased uptake of ¹¹¹In-DOTA-3A3 in mErbB3-expressing tissues. Encouragingly, growth of BxPC-3 xenografts in mice was delayed in an experimental (pilot-scale) therapy study using 3A3. We conclude that the 3A3 affibody format seems promising for treatment of HER3-overexpressing tumours.

Novel anti-Sialyl-Tn monoclonal antibodies and antibody-drug conjugates demonstrate tumor specificity and anti-tumor activity

Targeted therapeutics that can differentiate between normal and malignant tumor cells represent the ideal standard for the development of a successful anti-cancer strategy. The Sialyl-Thomsen-nouveau antigen (STn or Sialyl-Tn, also known as CD175s) is rarely seen in normal adult tissues, but it is abundantly expressed in many types of human epithelial cancers. We have identified novel antibodies that specifically target with high affinity the STn glycan independent of its carrier protein, affording the potential to recognize a wider array of cancer-specific sialylated proteins. A panel of murine monoclonal anti-STn therapeutic antibodies were generated and their binding specificity and efficacy were characterized in vitro and in in vivo murine cancer models. A subset of these antibodies were conjugated to monomethyl auristatin E (MMAE) to generate antibody-drug conjugates (ADCs). These ADCs demonstrated in vitro efficacy in STn-expressing cell lines and significant tumor growth inhibition in STn-expressing tumor xenograft cancer models with no evidence of overt toxicity.

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

Unmethylated cytosine-guanine dinucleotide-containing oligodeoxynucleotides (CpG ODNs), which are synthetic agonists of Toll-like receptor 9 (TLR9), activate humoral and cellular immunity and are being developed as vaccine adjuvants to prevent or treat cancers, infectious diseases, and allergies. Free CpG ODNs have been used in many clinical trials implemented to verify their effects. However, recent research has reported that self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes demonstrate higher adjuvant effects than free CpG ODNs, owing to their improved uptake efficiency into cells expressing TLR9. Moreover, protein/peptide–CpG ODN conjugates and nanomaterial–CpG ODN complexes are able to deliver CpG ODNs and antigens (or allergens) to the same types of cells, which enables a higher degree of prophylaxis or therapeutic effect. In this review, the author describes recent trends in the research and development of CpG ODN nanomedicines containing self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes, focusing mainly on the results of preclinical and clinical studies.

Glypican-3 Targeting Immunotoxins for the Treatment of Liver Cancer

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, yet no effective therapeutics exist. This review provides an overview of the recent development of recombinant immunotoxins for the treatment of glypican-3 (GPC3) expressing HCC. GPC3 is a cell surface heparan sulfate proteoglycan that is overexpressed in HCC, but is absent from normal adult human tissues. Treatment of HCC with anti-GPC3 immunotoxins represents a new therapeutic option. Using phage display and hybridoma technologies, three high affinity antibodies (HN3, HS20 and YP7) have been generated against GPC3. Two of these antibodies (HN3 and HS20) have demonstrated the ability to inhibit Wnt/Yap signaling, leading to a reduction in liver cancer cell proliferation. By combining the HN3 antibody capable of inhibiting Wnt/Yap signaling with the protein synthesis inhibitory domain of the Pseudomonas exotoxin, a recombinant immunotoxin that exhibits a dual inhibitory mechanism was generated. This immunotoxin was found to be highly effective in the treatment of human HCCs in mouse xenograft models. Engineering of the toxin fragment to reduce the level of immunogenicity is currently being explored. The development of immunotoxins provides opportunities for novel liver cancer therapies.

Nanomedicine approaches in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the malignancy with the highest incidence amongst children (26% of all cancer cases), being surpassed only by the cancers of the brain and of the nervous system. The most recent research on ALL is focusing on new molecular therapies, like targeting specific biological structures in key points in the cell cycle, or using selective inhibitors for transmembranary proteins involved in cell signalling, and even aiming cell surface receptors with specifically designed antibodies for active targeting. Nanomedicine approaches, especially by the use of nanoparticle-based compounds for the delivery of drugs, cancer diagnosis or therapeutics may represent new and modern ways in the near future anti-cancer therapies. This review offers an overview on the recent role of nanomedicine in the detection and treatment of acute lymphoblastic leukemia as resulting from a thorough literature survey. A short introduction on the basics of ALL is presented followed by the description of the conventional methods used in the ALL detection and treatment. We follow our discussion by introducing some of the general nano-strategies used for cancer detection and treatment. The detailed role of organic and inorganic nanoparticles in ALL applications is further presented, with a special focus on gold nanoparticle-based nanocarriers of antileukemic drugs.

Trial Watch: Immunotherapy plus radiation therapy for oncological indications

Malignant cells succumbing to some forms of radiation therapy are particularly immunogenic and hence can initiate a therapeutically relevant adaptive immune response. This reflects the intrinsic antigenicity of malignant cells (which often synthesize a high number of potentially reactive neo-antigens) coupled with the ability of radiation therapy to boost the adjuvanticity of cell death as it stimulates the release of endogenous adjuvants from dying cells. Thus, radiation therapy has been intensively investigated for its capacity to improve the therapeutic profile of several anticancer immunotherapies, including (but not limited to) checkpoint blockers, anticancer vaccines, oncolytic viruses, Toll-like receptor (TLR) agonists, cytokines, and several small molecules with immunostimulatory effects. Here, we summarize recent preclinical and clinical advances in this field of investigation.

Trial Watch-Small molecules targeting the immunological tumor microenvironment for cancer therapy

Progressing malignancies establish robust immunosuppressive networks that operate both systemically and locally. In particular, as tumors escape immunosurveillance, they recruit increasing amounts of myeloid and lymphoid cells that exert pronounced immunosuppressive effects. These cells not only prevent the natural recognition of growing neoplasms by the immune system, but also inhibit anticancer immune responses elicited by chemo-, radio- and immuno therapeutic interventions. Throughout the past decade, multiple strategies have been devised to counteract the accumulation or activation of tumor-infiltrating immunosuppressive cells for therapeutic purposes. Here, we review recent preclinical and clinical advances on the use of small molecules that target the immunological tumor microenvironment for cancer therapy. These agents include inhibitors of indoleamine 2,3-dioxigenase 1 (IDO1), prostaglandin E2, and specific cytokine receptors, as well as modulators of intratumoral purinergic signaling and arginine metabolism.

Local retention of antibodies in vivo with an injectable film embedded with a fluorogen-activating protein

Herein we report an injectable film by which antibodies can be localized in vivo. The system builds upon a bifunctional polypeptide consisting of a fluorogen-activating protein (FAP) and a β-fibrillizing peptide (βFP). The FAP domain generates fluorescence that reflects IgG binding sites conferred by Protein A/G (pAG) conjugated with the fluorogen malachite green (MG). A film is generated by mixing these proteins with molar excess of EAK16-II, a βFP that forms β-sheet fibrils at high salt concentrations. The IgG-binding, fluorogenic film can be injected in vivo through conventional needled syringes. Confocal microscopic images and dose-response titration experiments showed that loading of IgG into the film was mediated by pAG(MG) bound to the FAP. Release of IgG in vitro was significantly delayed by the bioaffinity mechanism; 26% of the IgG were released from films embedded with pAG(MG) after five days, compared to close to 90% in films without pAG(MG). Computational simulations indicated that the release rate of IgG is governed by positive cooperativity due to pAG(MG). When injected into the subcutaneous space of mouse footpads, film-embedded IgG were retained locally, with distribution through the lymphatics impeded. The ability to track IgG binding sites and distribution simultaneously will aid the optimization of local antibody delivery systems.

Natural and therapy-induced immunosurveillance in breast cancer

The immunosurveillance theory postulates that tumors evolve and progress in an uncontrolled fashion only when anticancer immune responses fail. Natural immunosurveillance clearly influences human breast cancer (BC) progression because the prognosis of BC patients is dictated by the density, composition and activity of the tumor immune infiltrate at diagnosis. Moreover, chemotherapeutic and radiotherapeutic regimens commonly employed for the treatment of BC affect the tumor immune infiltrate, and accumulating data suggest that the clinical efficacy of these treatments is largely determined by T cell-dependent tumor-specific immune responses. In addition, the mechanism of action of targeted anticancer therapeutics, such as the erb-b2 receptor tyrosine kinase 2 (ERBB2)-targeting agent trastuzumab, involves the innate and adaptive arms of the immune system. In this Review, we discuss these findings as well as preliminary evidence indicating that immunotherapy constitutes a promising option for the treatment of BC. Moreover, we point out that the successful implementation of immunotherapy to BC management requires the optimization of current immunotherapeutic regimens and the identification of immunological biomarkers that enable improved risk stratification and the design of personalized, dynamic treatment plans.