Anti-glioblastoma effect of a recombinant bispecific cytotoxin cotargeting human IL-13 and EGF receptors in a mouse xenograft model

Impact of repeated cycles of EGF bispecific angiotoxin (eBAT) administered at a reduced interval from doxorubicin chemotherapy in dogs with splenic haemangiosarcoma

We previously reported that eBAT, an EGF-targeted angiotoxin, was safe and it improved the overall survival for dogs with splenic haemangiosarcoma when added to the standard of care in a single cycle of three administrations in the minimal residual disease setting. Our objective for the SRCBST-2 trial was to assess whether increased dosing through multiple cycles of eBAT would be well tolerated and would further enhance the benefits of eBAT. Eligibility was expanded to dogs with stage 3 haemangiosarcoma, provided that gross lesions could be surgically excised. The interval between eBAT and the start of chemotherapy was reduced, and the experimental therapy was expanded to three cycles, each administered at the biologically active dose (50 μg/kg) on a Monday/Wednesday/Friday schedule following splenectomy, and scheduled 1 week prior to the first, second and fifth doxorubicin chemotherapy. Twenty-five dogs were enrolled; six experienced acute hypotension with two requiring hospitalization. Self-limiting elevation of ALT was observed in one dog. A statistically significant survival benefit was not seen in this study in eBAT-treated dogs compared with a Contemporary comparison group of dogs with stages 1-3 haemangiosarcoma treated with standard of care alone. Our results indicate that repeated dosing cycles of eBAT starting 1 week prior to doxorubicin chemotherapy led to greater toxicity and reduced efficacy compared with a single cycle given between surgery and a delayed start of chemotherapy. Further work is needed to understand the precise mechanisms of action of eBAT in order to optimize its clinical benefits in the treatment of canine haemangiosarcoma and other tumours. IACUC Protocols 1110A06186 and 1507-32804A.

Radioimmunotherapy (RIT) in Brain Tumors

Annually, the incidence of brain tumors has slightly increased and also the patient prognosis is still disappointing, especially for high-grade neoplasms. So, researchers seek methods to improve therapeutic index as a critical aim of treatment. One of these new challenging methods is radioimmunotherapy (RIT) that involves recruiting a coupling of radionuclide component with monoclonal antibody (mAb) which are targeted against cell surface tumor-related antigens or antigens of cells within the tumor microenvironment. In the context of cancer care, precision medicine is exemplified by RIT; precision medicine can offer a tailored treatment to meet the needs for treatment of brain tumors. This review aims to discuss the molecular targets used in radioimmunotherapy of brain tumors, available and future radioimmunopharmaceutics, clinical trials of radioimmunotherapy in brain neoplasms, and eventually, conclusion and future perspective of application of radioimmunotherapy in neurooncology cancer care.

Targeted Diphtheria Toxin-Based Therapy: A Review Article

Cancer remains one of the leading causes of death worldwide. Conventional therapeutic strategies usually offer limited specificity, resulting in severe side effects and toxicity to normal tissues. Targeted cancer therapy, on the other hand, can improve the therapeutic potential of anti-cancer agents and decrease unwanted side effects. Targeted applications of cytolethal bacterial toxins have been found to be especially useful for the specific eradication of cancer cells. Targeting is either mediated by peptides or by protein-targeting moieties, such as antibodies, antibody fragments, cell-penetrating peptides (CPPs), growth factors, or cytokines. Together with a toxin domain, these molecules are more commonly referred to as immunotoxins. Targeting can also be achieved through gene delivery and cell-specific expression of a toxin. Of the available cytolethal toxins, diphtheria toxin (DT) is one of the most frequently used for these strategies. Of the many DT-based therapeutic strategies investigated to date, two immunotoxins, Ontak^TM and Tagraxofusp^TM, have gained FDA approval for clinical application. Despite some success with immunotoxins, suicide-gene therapy strategies, whereby controlled tumor-specific expression of DT is used for the eradication of malignant cells, are gaining prominence. The first part of this review focuses on DT-based immunotoxins, and it then discusses recent developments in tumor-specific expression of DT.

Prolonged survival in secondary glioblastoma following local injection of targeted alpha therapy with 213Bi-substance P analogue

Background

Glioblastoma multiforme (GBM), the most common malignant brain tumor, mainly manifests as a primary de novo and less frequently as a secondary glial neoplasm. GBM has been demonstrated to overexpress the NK-1 receptor and substance P can be used as a ligand for targeted therapy. Alpha emitters, e.g. ²¹³Bi, that deposit their high energy within a short range allow the selective irradiation of tumor cells while sparing adjacent neuronal structures.

Material and methods

Among 50 glioma patients of different subtypes that have to date been treated with targeted alpha therapy at the Medical University Warsaw, we report here the data on nine patients with secondary GBM. Following surgery, chemo- and radiotherapy, recurrent GBM was treated by intracavitary injection of 1–6 doses of 0.9–2.3 GBq ²¹³Bi- DOTA-[Thi⁸,Met(O₂)¹¹]-substance P (²¹³Bi-DOTA-SP) in 2-month intervals. ⁶⁸Ga-DOTA-[Thi⁸,Met(O₂)¹¹]-substance P (⁶⁸Ga-DOTA-SP) was co-injected with the therapeutic doses to assess biodistribution using PET/CT. Therapeutic response was monitored with MRI.

Results

Treatment with activities ranging from 1.4 to 9.7 (median 5.8) GBq ²¹³Bi- DOTA-SP was well tolerated with only mild transient adverse reactions, mainly headaches due to a transient perfocal edema reaction. The median progression free survival and overall survival time following the initiation of alpha therapy was 5.8 and 16.4 months, respectively. The median overall survival time from the first diagnosis was 52.3 months. Two out of nine patients are still alive 39 and 51 months, respectively, after the initiation of the therapy.

Conclusions

Targeted alpha therapy of secondary GBM with ²¹³Bi-DOTA-SP is safe and well tolerated and may evolve as a promising novel therapeutic option for secondary GBM.

Antibody-drug conjugates in glioblastoma therapy: the right drugs to the right cells

Glioblastomas are high-grade brain tumours with a poor prognosis and, currently, few available therapeutic options. This lack of effective treatments has been linked to diverse factors, including target selection, tumour heterogeneity and poor penetrance of therapeutic agents through the blood-brain barrier and into tumours. Therapies using monoclonal antibodies, alone or linked to cytotoxic payloads, have proved beneficial for patients with different solid tumours; these approaches are currently being explored in patients with glioblastoma. In this Review, we summarise clinical data regarding antibody-drug conjugates (ADCs) against a variety of targets in glioblastoma, and compare the efficacy and toxicity of targeting EGFR with ADCs versus naked antibodies in order to illustrate key aspects of the use of ADCs in this malignancy. Finally, we discuss the complex challenges related to the biology and mutational changes of glioblastoma that can affect the use of ADC-based therapies in patients with this disease, and highlight potential strategies to improve efficacy.

Recombinant Immunotoxin Therapy of Glioblastoma: Smart Design, Key Findings, and Specific Challenges

Recombinant immunotoxins (RITs) refer to a group of recombinant protein-based therapeutics, which consists of two components: an antibody variable fragment or a specific ligand that allows RITs to bind specifically to target cells and an engineered toxin fragment that kills the target cells upon internalization. To date, over 1,000 RITs have been generated and significant success has been achieved in the therapy of hematological malignancies. However, the immunogenicity and off-target toxicities of RITs remain as significant barriers for their application to solid tumor therapy. A group of RITs have also been generated for the treatment of glioblastoma multiforme, and some have demonstrated evidence of tumor response and an acceptable profile of toxicity and safety in early clinical trials. Different from other solid tumors, how to efficiently deliver the RITs to intracranial tumors is more critical and needs to be solved urgently. In this article, we first review the design and expression of RITs, then summarize the key findings in the preclinical and clinical development of RIT therapy of glioblastoma multiforme, and lastly discuss the specific issues that still remain to forward RIT therapy to clinical practice.

Mutagenic Deimmunization of Diphtheria Toxin for Use in Biologic Drug Development

BACKGROUND

Targeted toxins require multiple treatments and therefore must be deimmunized. We report a method of protein deimmunization based on the point mutation of highly hydrophilic R, K, D, E, and Q amino acids on the molecular surface of truncated diphtheria-toxin (DT390).

METHODS

Based on their surface position derived from an X-ray-crystallographic model, residues were chosen for point mutation that were located in prominent positions on the molecular surface and away from the catalytic site. Mice were immunized with a targeted toxin containing either a mutated DT390 containing seven critical point mutations or the non-mutated parental toxin form.

RESULTS

Serum analysis revealed a significant 90% reduction in anti-toxin antibodies in mice immunized with the mutant, but not the parental drug form despite multiple immunizations. The experiment was repeated in a second strain of mice with a different MHC-haplotype to address whether point mutation removed T or B cell epitopes. Findings were identical indicating that B cell epitopes were eliminated from DT. The mutant drug form lost only minimal activity in vitro as well as in vivo.

CONCLUSION

These findings indicate that this method may be effective for deimmunizing of other proteins and that discovery of a deimmunized form of DT may lead to the development of more effective targeted toxin.

A novel bispecific immunotoxin delivered by human bone marrow-derived mesenchymal stem cells to target blood vessels and vasculogenic mimicry of malignant gliomas

Background

In previous years, immunotoxins have been shown to be a greatly promising therapeutic tool for brain malignancies, such as gliomas. Human mesenchymal stem cells (hMSCs) exhibit tropism to tumor tissue. However, the effect of bispecific immunotoxins in malignant gliomas is still unknown. The aim of this study was to investigate the function of bispecific immunotoxins in human malignant gliomas.

Materials and methods

In the present study, the bispecific immunotoxin VEGF₁₆₅-ephrin A1-PE38KDEL was established using deoxyribonucleic acid shuffling and cloning techniques. The VEGF₁₆₅-ephrin A1-PE38KDEL was delivered by hMSCs to mouse malignant gliomas. The effects of the bispecific immunotoxins on glioma-derived blood vessels and vasculogenic mimicry to elucidate the molecular mechanisms underlying the antitumorigenic effects of immunotoxins were examined in vivo.

Results

In vitro, transfected hMSCs significantly inhibited the cell viability of gliomas cell lines U87 and U251 in a dose-dependent manner compared with untransfected hMSCs (P<0.01). In vivo, the intratumoral injection of engineered hMSCs was effective at inhibiting tumor growth in a malignant glioma tumor model.

Conclusion

The bispecific immunotoxin secreted from hMSCs acts as a novel strategy for improving treatment options for malignant gliomas in the clinic.

Ginsenoside Rh2 inhibits growth of glioblastoma multiforme through mTor

Being the most malignant primary brain tumor in humans, glioblastoma multiforme (GBM) has a fairly poor patient survival after current combined treatment with chemotherapy, radiation, and surgery. Ginsenoside Rh2 (GRh2) has been reported to have a therapeutic effect on some tumors, and we recently reported its inhibitory effect on GBM growth in vitro and in vivo, possibly through an epidermal growth factor receptor (EGFR) signaling pathway. Here, using specific inhibitors, we found that the activation of EGFR signaling promoted GBM growth through PI3k/Akt/mTor signaling pathways. Moreover, GRh2 efficiently inhibited activation of this pathway at the receptor level. Together with our previous findings, these data suggest that GRh2 may suppress GBM growth through its competition with EGFR ligands for binding to the EGFR, and binding to EGFR by GRh2 does not lead to receptor phosphorylation. Thus, our data highlight a previous unappreciated role for GRh2 to inhibit EGFR signaling. GRh2 thus appears to be a promising therapy for cancers that require EGFR signaling to growth.

Inhibition of FoxO1 nuclear exclusion prevents metastasis of glioblastoma

Glioblastoma is the most aggressive malignant primary brain tumor in humans, with extremely poor patient survival. Although previous studies have demonstrated that expression of matrix metalloproteinase-9 (MMP9) in glioblastoma promotes cancer metastasis, the upstream molecular signaling cascades that control activation of MMP9 remain largely unknown. Here, we used a human glioblastoma line, A-172, to examine molecular signaling to activate MMP9. We found that epidermal growth factor (EGF)-induced activation of epidermal growth factor receptor (EGFR) in A-172 cells activated MMP9, resulting in an increase in cancer invasiveness. A specific inhibitor for EGFR efficiently blocked EGF-induced activation of MMP9 and then cancer invasiveness. Moreover, an inhibitor for phosphatidylinositol 3-kinase (PI-3 K)/protein kinase B (Akt) significantly inhibited the EGF-induced activation of MMP9. Furthermore, nuclear exclusion of a major Akt downstream target, Forkhead box protein O1 (FoxO1), was induced by Akt activation, which could be inhibited by either an EGFR inhibitor or by PI-3 K/Akt inhibitor. An expression of a constitutive nuclear form of FoxO1 significantly inhibited MMP9 activation induced by EGF. Taken together, these findings suggest that EGF/EGFR signaling activates downstream PI-3 K/Akt to induce FoxO1 nuclear exclusion, which activates MMP9 to promote glioblastoma invasiveness. Thus, FoxO1 appears to be a novel therapeutic target for inhibiting metastasis of glioblastoma.

Significance of interleukin-13 receptor alpha 2-targeted glioblastoma therapy

Glioblastoma multiforme (GBM) remains one of the most lethal primary brain tumors despite surgical and therapeutic advancements. Targeted therapies of neoplastic diseases, including GBM, have received a great deal of interest in recent years. A highly studied target of GBM is interleukin-13 receptor α chain variant 2 (IL13Rα2). Targeted therapies against IL13Rα2 in GBM include fusion chimera proteins of IL-13 and bacterial toxins, nanoparticles, and oncolytic viruses. In addition, immunotherapies have been developed using monoclonal antibodies and cell-based strategies such as IL13Rα2-pulsed dendritic cells and IL13Rα2-targeted chimeric antigen receptor-modified T cells. Advanced therapeutic development has led to the completion of phase I clinical trials for chimeric antigen receptor-modified T cells and phase III clinical trials for IL-13-conjugated bacterial toxin, with promising outcomes. Selective expression of IL13Rα2 on tumor cells, while absent in the surrounding normal brain tissue, has motivated continued study of IL13Rα2 as an important candidate for targeted glioma therapy. Here, we review the preclinical and clinical studies targeting IL13Rα2 in GBM and discuss new advances and promising applications.

EGFR signaling-dependent inhibition of glioblastoma growth by ginsenoside Rh2

Glioblastoma is the most common and most aggressive malignant primary brain tumor in humans, accounting for 52 % of all functional tissue brain tumor cases and 20 % of all intracranial tumors. The typical treatment involves a combination of chemotherapy, radiation, and surgery, whereas it still achieves fairly poor patient survival. Ginsenoside Rh2 has been reported to have a therapeutic effect on some tumors, but its effect on glioblastoma has not been extensively evaluated. Here, we show that ginsenoside Rh2 can substantially inhibit the growth of glioblastoma in vitro and in vivo in a mouse model. Moreover, the inhibition of the tumor growth appears to result from combined effects on decreased tumor cell proliferation and increased tumor cell apoptosis. Further analyses suggest that ginsenoside Rh2 may have its antiglioblastoma effect through inhibition of the epidermal growth factor receptor (EGFR) signaling pathway in tumor cells. In a lose-of-function experiment, recombinant EGFR was given together with ginsenoside Rh2 to the tumor cells in vitro and in vivo, which completely blocked the antitumor effects of ginsenoside Rh2. Thus, our data not only reveal an anti-glioblastoma effect of ginsenoside Rh2 but also demonstrate that this effect may function via inhibition of EGFR signaling in glioblastoma cells.

Hemangiosarcoma and its cancer stem cell subpopulation are effectively killed by a toxin targeted through epidermal growth factor and urokinase receptors

Targeted toxins have the potential to overcome intrinsic or acquired resistance of cancer cells to conventional cytotoxic agents. Here, we hypothesized that EGFuPA-toxin, a bispecific ligand-targeted toxin (BLT) consisting of a deimmunized Pseudomonas exotoxin (PE) conjugated to epidermal growth factor and urokinase, would efficiently target and kill cells derived from canine hemangiosarcoma (HSA), a highly chemotherapy resistant tumor, as well as cultured hemangiospheres, used as a surrogate for cancer stem cells (CSC). EGFuPA-toxin showed cytotoxicity in four HSA cell lines (Emma, Frog, DD-1 and SB) at a concentration of ≤100 nM, and the cytotoxicity was dependent on specific ligand-receptor interactions. Monospecific targeted toxins also killed these chemoresistant cells; in this case, a "threshold" level of EGFR expression appeared to be required to make cells sensitive to the monospecific EGF-toxin, but not to the monospecific uPA-toxin. The IC₅₀ of CSCs was higher by approximately two orders of magnitude as compared to non-CSCs, but these cells were still sensitive to EGFuPA-toxin at nanomolar (i.e., pharmacologically relevant) concentrations, and when targeted by EGFuPA-toxin, resulted in death of the entire cell population. Taken together, our results support the use of these toxins to treat chemoresistant tumors such as sarcomas, including those that conform to the CSC model. Our results also support the use of companion animals with cancer for further translational development of these cytotoxic molecules.

Targeting CD133 in an in vivo ovarian cancer model reduces ovarian cancer progression

OBJECTIVES

While most women with ovarian cancer will achieve complete remission after treatment, the majority will relapse within two years, highlighting the need for novel therapies. Cancer stem cells (CSC) have been identified in ovarian cancer and most other carcinomas as a small population of cells that can self-renew. CSC are more chemoresistant and radio-resistant than the bulk tumor cells; it is likely that CSC are responsible for relapse, the major problem in cancer treatment. CD133 has emerged as one of the most promising markers for CSC in ovarian cancer. The hypothesis driving this study is that despite their low numbers in ovarian cancer tumors, CSC can be eradicated using CD133 targeted therapy and tumor growth can be inhibited.

METHODS

Ovarian cancer cell lines were evaluated using flow cytometry for expression of CD133. In vitro viability studies with an anti-CD133 targeted toxin were performed on one of the cell lines, NIH:OVCAR5. The drug was tested in vivo using a stably transfected luciferase-expressing NIH:OVCAR5 subline in nude mice, so that tumor growth could be monitored by digital imaging in real time.

RESULTS

Ovarian cancer cell lines showed 5.6% to 16.0% CD133 expression. dCD133KDEL inhibited the in vitro growth of NIH:OVCAR5 cells. Despite low numbers of CD133-expressing cells in the tumor population, intraperitoneal drug therapy caused a selective decrease in tumor progression in intraperitoneal NIH:OVCAR5-luc tumors.

CONCLUSIONS

Directly targeting CSC that are a major cause of drug resistant tumor relapse with an anti-CD133 targeted toxin shows promise for ovarian cancer therapy.

In vitro and in vivo anti-tumor activities of anti-EGFR single-chain variable fragment fused with recombinant gelonin toxin

PURPOSE

Epidermal growth factor receptor (EGFR) plays an important role in the growth and metastasis of many solid tumors. Strategies that target EGFR hold promising therapeutic potential for the treatment for non-small cell lung cancer (NSCLC), as EGFR is normally overexpressed in these tumors. This study was designed to determine whether an anti-EGFR immunotoxin has anti-tumor activity against NSCLC, and if so, to further investigate the possible mechanisms of cytotoxicity.

METHODS

A fusion protein of anti-EGFR single-chain variable fragment (anti-EGFR scFv) and the plant toxin gelonin (rGel) was constructed, expressed in bacteria, and purified to homogeneity. Cytotoxicity of anti-EGFR scFv/rGel (E/rG) immunotoxin was assessed on A549, HCC827, and H1975 cells (EGFR-overexpressing NSCLC-derived cell lines) and A549 xenografts in nude mice.

RESULTS

Cytotoxicity experiments using E/rG on A549, HCC827, and H1975 cells demonstrated that E/rG can specifically inhibit proliferation of these cells, whereas it did not affect the proliferation of Raji cells that do not express EGFR. Treatment for A549 xenografts in nude mice with E/rG resulted in significant suppression of tumor growth compared to controls. Immunofluorescence in frozen tissue sections confirmed that E/rG could specifically bind to tumor tissues in nude mice bearing A549 tumor xenografts, while rGel alone showed no binding activity. Furthermore, E/rG inhibited the growth of A549 cells by cytotoxic effects that blocked tumor proliferation, and the immunotoxin-induced cell death may be mediated by autophagy.

CONCLUSIONS

These results showed that E/rG might have significant potential as a novel clinical therapeutic agent against human NSCLC.

Dual targeting strategies with bispecific antibodies

Monoclonal antibodies are widely used for the treatment of cancer, inflammatory and infectious diseases and other disorders. Most of the marketed antibodies are monospecific and therefore capable of interacting and interfering with a single target. However, complex diseases are often multifactorial in nature, and involve redundant or synergistic action of disease mediators or upregulation of different receptors, including crosstalk between their signaling networks. Consequently, blockade of multiple, different pathological factors and pathways may result in improved therapeutic efficacy. This result can be achieved by combining different drugs, or use of the dual targeting strategies applying bispecific antibodies that have emerged as an alternative to combination therapy. This review discusses the various dual targeting strategies for which bispecific antibodies have been developed and provides an overview of the established bispecific antibody formats.

Toxin-based targeted therapy for malignant brain tumors

Despite advances in conventional treatment modalities for malignant brain tumors-surgery, radiotherapy, and chemotherapy-the prognosis for patients with high-grade astrocytic tumor remains dismal. The highly heterogeneous and diffuse nature of astrocytic tumors calls for the development of novel therapies. Advances in genomic and proteomic research indicate that treatment of brain tumor patients can be increasingly personalized according to the characteristics of the targeted tumor and its environment. Consequently, during the last two decades, a novel class of investigative drug candidates for the treatment of central nervous system neoplasia has emerged: recombinant fusion protein conjugates armed with cytotoxic agents targeting tumor-specific antigens. The clinical applicability of the tumor-antigen-directed cytotoxic proteins as a safe and viable therapy for brain tumors is being investigated. Thus far, results from ongoing clinical trials are encouraging, as disease stabilization and patient survival prolongation have been observed in at least 109 cases. This paper summarizes the major findings pertaining to treatment with the different antiglioma cytotoxins at the preclinical and clinical stages.

Evaluation of a bispecific biological drug designed to simultaneously target glioblastoma and its neovasculature in the brain

OBJECT

The authors of this study aimed to genetically design a bispecific targeted toxin that would simultaneously target overexpressed markers on glioma as well as the tumor vasculature, to mutate certain amino acids to reduce the immunogenicity of this new drug, and to determine whether the drug was able to effectively reduce aggressive human brain tumors in a rat xenograft model via a novel hollow fiber (HF) catheter delivery system.

METHODS

A new bispecific ligand-directed toxin (BLT) was created in which 2 human cytokines-epidermal growth factor ([EGF], targeting overexpressed EGF receptor) and amino acid terminal fragment ([ATF], targeting urokinase plasminogen activator receptor)-were cloned onto the same single-chain molecule with truncated Pseudomonas exotoxin with a terminal lysyl-aspartyl-glutamyl-leucine (KDEL) sequence. Site-specific mutagenesis was used to mutate amino acids in 7 key epitopic toxin regions that dictate the B cell generation of neutralizing antitoxin antibodies to deimmunize the drug, now called "EGFATFKDEL 7mut." Bioassays were used to determine whether mutation reduced the drug's potency, and enzyme-linked immunosorbent assay studies were performed to determine whether antitoxin antibodies were decreased. Aggressive brain tumors were intracranially established in nude rats by using human U87 glioma genetically marked with a firefly luciferase reporter gene (U87-luc), and the rats were stereotactically treated with 2 intracranial injections of deimmunized EGFATFKDEL via convection-enhanced delivery (CED). Drug was administered through a novel HF catheter to reduce drug backflow upon delivery.

RESULTS

In vitro, EGFATFKDEL 7mut selectively killed the human glioblastoma cell line U87-luc as well as cultured human endothelial cells in the form of the human umbilical vein endothelial cells. Deimmunization did not reduce drug activity. In vivo, when rats with brain tumors were intracranially treated with drug via CED and a novel HF catheter to reduce backflow, there were significant tumor reductions in 2 experiments (p < 0.01). Some rats survived with a tumor-free status until 130 days post-tumor inoculation. An irrelevant BLT control did not protect establishing specificity. The maximal tolerated dose of EGFATFKDEL 7mut was established at 2 μg/injection or 8.0 μg/kg, and data indicated that this dose was nontoxic. Antitoxin antibodies were reduced by at least 90%.

CONCLUSIONS

First, data indicated that the BLT framework is effective for simultaneously targeting glioma and its neovasculature. Second, in the rodent CED studies, newly developed HF catheters that limit backflow are effective for drug delivery. Third, by mutating critical amino acids, the authors reduced the threat of the interference of neutralizing antibodies that are generated against the drug. The authors' experiments addressed some of the most urgent limitations in the targeted toxin field.

Allergy and risk of glioma: a meta-analysis

We evaluated the association between allergic conditions and the risk of glioma in case-control and cohort studies published so far on this issue. A total of 12 studies (10 case-control and 2 cohort studies) were included in the analysis, involving 61 090 participants, of whom 6408 had glioma. When compared with non-allergic conditions, the pooled odds ratio (OR) with any allergic conditions for glioma was 0.60 (95% CI: 0.52-0.69, P<0.001), suggesting a significant negative association (protective effect) between allergy and glioma. Subgroup analysis showed that the ORs were 0.70 (95% CI: 0.62-0.79, P<0.001), 0.69 (95% CI: 0.62-0.78, P<0.001), and 0.78 (95% CI: 0.70-0.87, P<0.001) for asthma, eczema, and hay fever, respectively. The significant association remained even after excluding the bias of proxy reporting (OR=0.61; 95% CI: 0.50-0.75, P<0.001). We conclude that allergic conditions may significantly reduce the risk of glioma.

A new drug delivery method of bispecific ligand-directed toxins, which reduces toxicity and promotes efficacy in a model of orthotopic pancreatic cancer

OBJECTIVE

Biologicals targeting epidermal growth factor (EGF) and interleukin 13 receptors not only react with overexpressed markers on cancer cells but also react with receptors on normal cells. Because we developed novel bispecific ligand-directed toxins synthesized by cloning EGF and interleukin 13 on the same molecule with toxin, our objective was to determine whether we could block normal receptors while still targeting receptors overexpressed on cancer cells, thereby decreasing toxicity while maintaining efficacy.

METHODS

A method, toxicity blocking (ToxBloc), was developed in which a bolus intraperitoneal dose of recombinant EGF13 (without toxin) was given to mice approximately 15 to 20 minutes before DTEGF13. Experiments were then performed to determine whether the maximal tolerated dose (MTD) was reduced and whether we were still able to eliminate progression of aggressive human, metastatic, pancreatic cancer induced by orthotopic injection (OT) in nude mice.

RESULTS

ToxBloc permitted us to safely exceed the DTEGF13 maximal tolerated dose by 15-fold. This approach permitted repetitive high dosing with the bispecific ligand-directed toxin resulting in tumor regression (P < 0.01). Tumor effects were documented using a tumor imaging model in which OT tumor growth was monitored noninvasively in real time. ToxBloc was selective because other bispecific peptides did not block.

CONCLUSIONS

ToxBloc represents a new method of drug delivery and a potential solution to the problem of toxicity.

Design and modification of EGF4KDEL 7Mut, a novel bispecific ligand-directed toxin, with decreased immunogenicity and potent anti-mesothelioma activity

BACKGROUND

Potency, immunogenicity, and toxicity are three problems that limit the use of targeted toxins in solid tumour therapy.

METHODS

To address potency, we used genetic engineering to develop a novel bispecific ligand-directed toxin (BLT) called EGF4KDEL, a novel recombinant anti-mesothelioma agent created by linking human epidermal growth factor (EGF) and interleukin-4 (IL-4) to truncated pseudomonas exotoxin (PE38) on the same single-chain molecule. Immunogenicity was reduced by mutating seven immunodominant B-cell epitopes on the PE38 molecule to create a new agent, EGF4KDEL 7Mut.

RESULTS

In vitro, bispecific EGF4KDEL showed superior anti-mesothelioma activity compared with its monospecific counterparts. Toxicity in mice was diminished by having both ligands on the same molecule, allowing administration of a 10-fold greater dose of BLT than a mixture of monomeric IL4KDEL and EGFKDEL. EGF4KDEL 7Mut, retained all of its functional activity and induced about 87% fewer anti-toxin antibodies than mice given the parental, non-mutated form. In vivo, intraperitoneal (IP) injection of the BLT showed significant (P<0.01) and impressive effects against two aggressive, malignant IP mesothelioma models when treatment was begun 14-16 days post tumour innoculation.

CONCLUSION

These data show that EGF4KDEL 7Mut is a promising new anti-mesothelioma agent that was developed to specifically address the obstacles facing clinical utility of targeted toxins.

Intracranial elimination of human glioblastoma brain tumors in nude rats using the bispecific ligand-directed toxin, DTEGF13 and convection enhanced delivery

A bispecific ligand-directed toxin (BLT) consisting of human interleukin-13, epithelial growth factor, and the first 389 amino acids of diphtheria toxin was assembled in order to target human glioblastoma. In vitro, DTEGF13 selectively killed the human glioblastoma cell line U87-luc as well as other human glioblastomas. DTEGF13 fulfilled the requirement of a successful BLT by having greater activity than either of its monospecific counterparts or their mixture proving it necessary to have both ligands on the same single chain molecule. Aggressive brain tumors established intracranially (IC) in nude rats with U87 glioma genetically marked with a firefly luciferase reporter gene were treated with two injections of DTEGF13 using convection enhanced delivery resulting in tumor eradication in 50% of the rats which survived with tumor free status at least 110 days post tumor inoculation. An irrelevant BLT control did not protect establishing specificity. The bispecific DTEGF13 MTD dose was measured at 2 microg/injection or 0.5 microg/kg and toxicity studies indicated safety in this dose. Combination of monospecific DTEGF and DTIL13 did not inhibit tumor growth. ELISA assay indicated that anti-DT antibodies were not generated in normal immunocompetent rats given identical intracranial DTEGF13 therapy. Thus, DTEGF13 is safe and efficacious as an alternative drug for glioblastoma therapy and warrants further study.

EGFR-targeted diphtheria toxin stimulates TRAIL killing of glioblastoma cells by depleting anti-apoptotic proteins

Current treatments for Glioblastoma multiforme (GBM) involve surgery, radiotherapy, and cytotoxic chemotherapy; however, these treatments are not effective and there is an urgent need for better treatments. We investigated GBM cell killing by a novel drug combination involving DT-EGF, an Epidermal Growth Factor Receptor-targeted bacterial toxin, and Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) or antibodies that activate the TRAIL receptors DR4 and DR5. DT-EGF kills GBM cells by a non apoptotic mechanism whereas TRAIL kills by inducing apoptosis. GBM cells treated with DT-EGF and TRAIL were killed in a synergistic fashion in vitro and the combination was more effective than either treatment alone in vivo. Tumor cell death with the combination occurred by caspase activation and apoptosis due to DT-EGF positively regulating TRAIL killing by depleting FLIP, a selective inhibitor of TRAIL receptor-induced apoptosis. These data provide a mechanism-based rationale for combining targeted toxins and TRAIL receptor agonists to treat GBM.

Genetic alteration of a bispecific ligand-directed toxin targeting human CD19 and CD22 receptors resulting in improved efficacy against systemic B cell malignancy

A bispecific ligand-directed toxin (BLT) called DT2219ARL consisting of two scFv ligands recognizing CD19 and CD22 and catalytic DT390 was genetically enhanced for superior in vivo anti-leukemia activity. Genetic alterations included reverse orienting VH-VL domains and adding aggregation reducing/stabilizing linkers. In vivo, these improvements resulted in previously unseen long-term tumor-free survivors measured in a bioluminescent xenograft imaging model in which the progression of human Raji Burkitt's lymphoma could be tracked in real time and in a Daudi model as well. Studies showed DT2219ARL was potent (IC50s 0.06-0.2 nM range) and selectively blockable. Imaging studies indicated the highly invasive nature of this B cell malignancy model and showed it likely induced pre-terminal hind limb paralysis because of metastasis to spinal regions prevented by DT2219ARL. DT2219ARL represents a new class of bispecific biological that can be continually improved by genetic mutation.