Search Results (159)

Malignant gliomas remain highly treatment-resistant brain tumors despite surgery and adjuvant therapies. Targeted toxin therapies represent a unique strategy that exploits receptor-mediated cellular internalization to deliver cytotoxic components that result in the irreversible inhibition of protein synthesis independent of DNA damage or cell-cycle status. Advances in molecular profiling, toxin engineering, and delivery development have refined components targeting IL4Rα, IL13Rα2, EGFR/EGFRvIII, uPAR, and the transferrin receptor. Early clinical studies demonstrated biological activity, acceptable safety, and durable responses in subsets of patients, validating the fundamental mechanism of this approach. However, late-phase trials failed to demonstrate a population-level survival benefit, largely due to variability in delivery, receptor heterogeneity, and limitations in trial design rather than insufficient cytotoxic potency. Recent progress has focused on multiple receptor-targeting and delivery systems capable of achieving reliable intratumoral distribution. MRI-guided convection-enhanced delivery, vector-mediated toxin expression, and blood–brain barrier penetrant nanocarriers now enable more precise tumor targeting. Emerging evidence also reveals that toxin-mediated cytotoxicity can enhance antitumor immune responses, supporting their integration with immunotherapy. These advances position targeted toxins as precision cytotoxic compounds whose success depends on coordinated molecular targeting, delivery optimization, and biologically stratified patient selection, establishing a translational pathway for future glioma therapy. Full article

Background/Objectives: Head and neck squamous cell carcinoma (HNSCC) affects over 600,000 individuals worldwide each year, and its incidence continues to rise. There is a growing need for novel therapeutic strategies that achieve high antitumor efficacy while minimizing functional impairment. We developed a novel approach to enhance intracellular delivery of immunotoxins (ITs) by combining a photosensitizer under illumination. This method, termed intelligent Targeted Anti-body Phototherapy (iTAP), utilizes light as a spatiotemporal trigger to promote the cytoplasmic release of toxins. In the present study, we investigated the in vivo therapeutic efficacy of iTAP using an EGFR-targeted IT composed of cetuximab conjugated to saporin (IT-Cmab), administered in combination with the clinically used photodynamic therapy (PDT) photosensitizer NPe6, in a xenograft mouse model. Methods: Sa3 cells were implanted subcutaneously into the right hind limb of nude mice. Mice were randomized into four groups (n = 5): (i) iTAP (IT-Cmab plus NPe6), (ii) IT-Cmab alone, (iii) NPe6 alone, and (iv) saline control. Treatment was initiated once tumors exceeded 40 mm³. Mice received intraperitoneal IT-Cmab (0.5 mg/kg), followed 72 h later by intravenous NPe6 (5 mg/kg). Tumors were irradiated 3–4 h later using a custom LED device (670 nm, 262 mW/cm², 30 J/cm²). Tumor volume and body weight were monitored over time, and antitumor effects were analyzed using a linear mixed-effects model. Results: iTAP treatment produced the earliest and most pronounced inhibition of tumor growth among the four groups. Significant suppression was observed from day 9 and persisted throughout the study. IT-Cmab alone showed a moderate but sustained antitumor effect with a later onset, whereas NPe6-mediated PDT exhibited only a delayed and weaker response. On the final day, median tumor volumes showed substantial reductions relative to the Control group (601%), with decreases of 41% in PDT (357%), 55% in IT-Cmab (271%), and 70% in iTAP (178%). Overall, iTAP demonstrated the strongest and most durable therapeutic efficacy in vivo. Conclusions: These findings indicate that iTAP represents a promising therapeutic strategy for HNSCC. Full article

Background: We are developing cytotoxic immunoconjugates (CICs) to eliminate HIV-infected cells. We investigated the efficacy and kinetics of killing by different forms of CICs targeted by the same monoclonal antibody (mAb), an immunotoxin (IT), antibody-drug conjugate (ADC), and radioimmunoconjugate (RIC). Methods: We compared in vitro effects of CICs made by conjugating anti-gp41 mAb 7B2 to deglycosylated ricin A chain (7B2-dgA), the anthracycline derivative PNU-159682 (7B2-PNU), or the α-emitting isotope actinium-225 (7B2-²²⁵Ac). Kinetic analyses of cell growth were performed measuring electrical impedance every 15 min over a 7-day period using cells stably expressing the HIV envelope and Env-negative parent cells. Results: 7B2-dgA and 7B2-²²⁵Ac were more potent and acted more rapidly to kill cells than 7B2-PNU. Both the 7B2-PNU and 7B2-²²⁵Ac induced bystander-cell killing, whereas the IT did not and consequently allowed the outgrowth of Env-negative cells. Low dose or brief exposure to 7B2-PNU resulted in an increased rate of cell growth. Conclusions: An IT, ADC, and RIC showed substantial differences in the degree of specific toxicity, kinetics, and mechanisms of killing. The results of this side-by-side comparison have implications for the development of CICs to treat HIV, as well as other conditions. Full article

Immunotoxins are chimeric molecules with high potential as therapeutic candidates that combine antibody specificity to recognize and bind tumor-associated antigens and the cytotoxic potency of the enzymatic activity of a toxin, leading to the selective death of target cells. The use of immunotoxins as therapeutic tools remains limited by various issues, such as selecting the appropriate tumor-associated antigen (TAA), penetration difficulties in solid tumors, low renal clearance, and low toxic payload. For this purpose, in this work we have designed a novel trimeric immunotoxin (IMTXTriA33αS) against colorectal cancer, combining the scFv against GPA33 as a targeting domain and the fungal ribotoxin α-sarcin (αS) as the toxic fragment, linked by a trimerization domain (TIE^XVIII). Our results demonstrate that IMTXTriA33αS has greater avidity and toxic load, showing a very significant increase in its in vitro and in vivo antitumor efficacy, due to its trimeric structure. Full article

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disorder characterized by progressive dilation and weakening of the abdominal aortic wall. Despite advances in surgical repair, rupture remains associated with mortality rates exceeding 65%, and no effective pharmacological therapy exists to prevent disease progression. Increasing evidence highlights chronic inflammation, extracellular matrix degradation, and immune dysregulation as central drivers of AAA pathogenesis. Among these mechanisms, the thrombospondin-1 (TSP1)–CD47 signaling axis has emerged as a critical upstream regulator of vascular inflammation. By engaging CD47, TSP1 promotes macrophage activation, impairs efferocytosis, and sustains a self-perpetuating inflammatory loop that accelerates tissue destruction. This positions the TSP1–CD47 pathway as more than a bystander in aneurysm biology, linking immune activation with structural failure of the aortic wall. The therapeutic relevance of this axis is underscored by the development of CD47-targeted agents in oncology, which restore phagocytosis and immune balance. Repurposing such strategies for vascular medicine, in combination with advanced drug delivery systems, offers a promising avenue for disease-modifying therapy in AAA. Notably, two targeted drug delivery approaches have been described: both employ bispecific targeting of CD47 in combination with a macrophage-specific marker, using immunotoxins encapsulated in liposomal carriers to enhance selectivity and therapeutic efficacy. By shifting focus from structural repair to immune modulation, targeting the TSP1–CD47 axis with these strategies has the potential to redefine the clinical management of this condition. Full article

Micro- and nanoplastics (MNPs) are emerging environmental immunotoxins with widespread human exposure through ingestion, inhalation, and dermal contact. Detected in the placenta, lungs, blood, bone marrow, and brain, MNPs accumulate in immune organs where they disrupt innate and adaptive cell functions. This review aims to provide a comprehensive summary of the current knowledge on how MNPs affect the immune system at the cellular and molecular levels. Experimental evidence shows that MNPs impair macrophage phagocytosis, skew dendritic cell maturation, trigger neutrophil extracellular traps, and alter T and B cell responses. Mechanistically, these effects are driven by oxidative stress, mitochondrial dysfunction, and activation of key inflammatory signaling pathways, including NF-κB, MAPK, and NLRP3 inflammasome, leading to apoptosis, pyroptosis, and chronic low-grade inflammation. Furthermore, MNP-induced disruption of epithelial barriers and gut microbiota composition undermines immune tolerance and contributes to the pathogenesis of autoimmune conditions. Preclinical models provide evidence linking MNP exposure to exacerbation of diseases such as systemic lupus erythematosus, inflammatory bowel disease, and rheumatoid arthritis. However, human epidemiological data remain limited, highlighting the urgent need for standardized exposure protocols, advanced omics technologies, and longitudinal cohort studies are urgently needed to establish causal links and inform public health strategies. Full article

Allergies constitute one of the major health problems worldwide, increasing their prevalence in developed countries. To overcome this multifactorial disease, immunotherapy and the use of immune molecules, such as immunotoxins, have arisen as promising therapeutic tools. We have designed, produced, and characterized a new immunotoxin called IL-33αS, encompassing the murine IL-33 (mIL-33) as the target domain and the ribotoxin α-sarcin as the toxic domain. IL-33 is a widely described alarmin that binds to the ST2 receptor of a variety of immune cells, including ILC2s, leading to Th2-derived inflammatory response, as occurs in allergic reactions. Both IL-33αS and mIL-33 were successfully produced in the methylotrophic yeast Pichia pastoris and purified to homogeneity through affinity chromatography for their characterization. Both IL-33αS and mIL-33 were able to specifically bind to ST2⁺ Raw 264.7 cells, and IL-33αS kept the ribonucleolytic activity of α-sarcin, allowing IL-33αS to exhibit cytotoxic effects against ST2⁺-targeted cells. In addition, IL-33αS induced significantly less secretion of the Th2-linked cytokine IL-13 in comparison to mIL-33, suggesting steric interference produced by the presence of the α-sarcin. These results assess the potential therapeutic effect of this new immunotoxin against allergies, causing ST2-targeted cytotoxicity while avoiding the Th2 cytokine secretion. Full article

Evidence of possible cerebellar involvement in spatial processing, place learning and other types of higher order functions comes mainly from clinical observations, as well as from mutant mice and lesion studies. The latter, in particular, have reported deficits in spatial learning and memory following surgical or neurotoxic cerebellar ablation. However, the low specificity of such manipulations has often made it difficult to precisely dissect the cognitive components of the observed behaviors. Likewise, due to conflicting data coming from lesion studies, it has not been possible so far to conclusively address whether a cerebellar dysfunction is sufficient per se to induce learning deficits, or whether concurrent damage to other regulatory structure(s) is necessary to significantly interfere with cognitive processing. In the present study, the immunotoxin 192 IgG-saporin, selectively targeting cholinergic neurons in the basal forebrain and a subpopulation of cerebellar Purkinje cells, was administered to adult rats bilaterally into the basal forebrain nuclei, the cerebellar cortices or both areas combined. Additional animals underwent injections of the toxin into the lateral ventricles. Starting from two–three weeks post-lesion, the animals were tested on paradigms of motor ability as well as spatial learning and memory and then sacrificed for post-mortem morphological analyses. All lesioned rats showed no signs of ataxia and no motor deficits that could impair their performance in the water maze task. The rats with discrete cerebellar lesions exhibited fairly normal performance and did not differ from controls in any aspect of the task. By contrast, animals with double lesions, as well as those with 192 IgG-saporin given intraventricularly did manifest severe impairments in both reference and working memory. Histo- and immunohistochemical analyses confirmed the effects of the toxin conjugate on target neurons and fairly similar patterns of Purkinje cell loss in the animals with cerebellar lesion only, basal forebrain-cerebellar double lesions and bilateral intraventricular injections of the toxin. No such loss was by contrast seen in the basal forebrain-lesioned animals, whose Purkinje cells were largely spared and exhibited a normal distribution pattern. The results suggest important functional interactions between the ascending regulatory inputs from the cerebellum and those arising in the basal forebrain nuclei that would act together to modulate the complex sensory–motor and cognitive processes required to control whole body movement in space. Full article

Protein toxins are biologically active polypeptides produced by a variety of organisms, including bacteria, plants, fungi, and animals. These molecules exert potent and specific toxic effects on target cells and are primarily associated with pathogenicity and defense mechanisms of the organisms. In the past few decades, significant progress has been made in understanding their structure, mechanisms of action, and regulation. Among these, bacterial protein toxins have emerged as valuable tools particularly in the development of targeted therapies. A notable example is Botulinum toxin, originally known for its neurotoxic effects, which was approved as a therapeutic agent in 1989 for strabismus treatment, paving way for repurposing bacterial toxins for clinical use. This review provides an overview of the different classes of bacterial toxin-based therapeutics, with a particular focus on Pseudomonas exotoxin A (PE) from Pseudomonas aeruginosa and anthrax toxin from Bacillus anthracis. The modular architecture and potent cytotoxicity of these A-B type toxins have enabled their successful adaptation into targeted cancer therapies. The clinical approval of the PE-based immunotoxin, moxetumomab pasudotox, for the treatment of hairy cell leukemia, underscores the potential of this strategy. This review also discusses current challenges and outlines future directions for the advancement of bacterial toxin-based therapeutics. Full article

Background. We are developing cytotoxic anti-HIV immunoconjugates to attack the reservoir of infected cells that persist after years of fully suppressive anti-retroviral therapy. Methods. We have produced a chimeric fusion protein, J3ExoA, consisting of J3VHH, a broadly reactive anti-gp120 camelid nanobody, joined to the de-immunized PE38 fragment of Pseudomonas exotoxin A. The efficacy of J3ExoA was compared to that of a well-studied anti-gp41 immunotoxin (IT), 7B2-dgA, in cytotoxicity assays and for inhibition of infectivity. Immunogenicity of the ITs was tested in mice. Results. J3ExoA killed cells expressing the HIV envelope with specificity in concentrations in the ng/mL range. Of all anti-HIV ITs we have tested, only J3ExoA compared to 7B2-dgA in cytotoxic efficacy, although there were differences between the two ITs on different target cells. J3ExoA suppressed the spread of HIV infection in tissue culture. J3ExoA was less immunogenic than 7B2-dgA, but mice made antibodies to both portions of the fusion protein. Conclusions. J3ExoA represents a novel IT that may be used to eliminate infected cells in the persistent HIV reservoir of infection, the barrier to an HIV “cure.” Additional approaches for addressing IT immunogenicity are discussed. Full article

Sarcomas are very complex and clinically challenging mesenchymal tumors. Although the standard therapeutic approach has improved the 5-year survival rate, many patients experience local relapses and/or distant metastases. To improve patient outcome, new strategies need to be investigated. Immunotoxins (ITs) based on rRNA N-glycosylases (also named ribosome-inactivating proteins, RIPs) are promising tools for cancer therapy because, by combining rRNA-glycosylase’s high cytotoxicity with carrier selectivity, they can specifically eliminate target neoplastic cells. In the last few years, 3D models have been extensively used in cancer research, particularly for target-specific drug screening. This study aimed to evaluate the possibility of utilizing ribosome-inactivating protein (RIP)-containing ITs to selectively target TfR1-, EGFR1- and Her2-expressing sarcoma adherent cells (ACs), spheroids (SSs) and organoids (ORs). To compare Its’ efficacy and ability to induce apoptosis, we performed dose–response viability and caspase 3/7 activation assays on rhabdomyosarcoma and osteosarcoma ACs, SSs and ORs treated with Tf-IT, αEGFR1-IT and αHer2-IT. Our results indicate that, compared to the corresponding unconjugated RIPs, all ITs showed increased cytotoxicity in sarcoma ACs. Despite the increased complexity characterizing 3D models, the higher IC₅₀ differences between ITs and unconjugated RIPs were obtained in ORs, which appeared more resistant to the nonspecific killing of the RIPs than either the ACs or SSs, thus augmenting the therapeutic window between unconjugated and conjugated RIPs. IT induced a more delayed apoptosis in 3D compared to 2D models. Our results provide essential outcomes for the potential use of these RIP-based ITs as a therapeutic strategy to treat sarcoma. Full article

The tumor microenvironment (TME) is a unique ecosystem that surrounds tumor tissues. The TME is composed of extracellular matrix, immune cells, blood vessels, stromal cells, and fibroblasts. These environments enhance cancer development, progression, and metastasis. Recent success in immune checkpoint blockade also supports the importance of the TME and immune cells residing in the tumor niche. Although the TME can be identified in almost all cancer types, the role of the TME may not be similar among different cancer types. Regulatory T cells (Tregs) play a pivotal role in immune homeostasis and are frequently found in the TME. Owing to their suppressive function, Tregs are often considered unfavorable factors that allow the immune escape of cancer cells. However, the presence of Tregs is not always linked to an unfavorable phenotype, which can be explained by the heterogeneity and plasticity of Tregs. In this review, the current understanding of the role of Tregs in TME is addressed for each cancer cell type. Moreover, recently a therapeutic approach targeting Tregs infiltrating in the TME has been developed including drug antibody conjugate, immunotoxin, and FOXP3 inhibiting peptide. Thus, understanding the role of Tregs in the TME may lead to the development of novel therapies that directly target the TME. Full article

Mesothelioma is characterized by the inactivation of tumor suppressor genes, with frequent mutations in neurofibromin 2 (NF2), BRCA1-associated protein 1 (BAP1), and cyclin-dependent kinase inhibitor 2A (CDKN2A). These mutations lead to disruptions in the Hippo signaling pathway and histone methylation, thereby promoting tumor growth. NF2 mutations result in Merlin deficiency, leading to uncontrolled cell proliferation, whereas BAP1 mutations impair chromatin remodeling and hinder DNA damage repair. Emerging molecular targets in mesothelioma include mesothelin (MSLN), oxytocin receptor (OXTR), protein arginine methyltransferase (PRMT5), and carbohydrate sulfotransferase 4 (CHST4). MSLN-based therapies, such as antibody–drug conjugates and immunotoxins, have shown efficacy in clinical trials. OXTR, upregulated in mesothelioma, is correlated with poor prognosis and represents a novel therapeutic target. PRMT5 inhibition is being explored in tumors with MTAP deletions, commonly co-occurring with CDKN2A loss. CHST4 expression is associated with improved prognosis, potentially influencing tumor immunity. Immune checkpoint inhibitors targeting PD-1/PD-L1 have shown promise in some cases; however, resistance mechanisms remain a challenge. Advances in multi-omics approaches have improved our understanding of mesothelioma pathogenesis. Future research will aim to identify novel therapeutic targets and personalized treatment strategies, particularly in the context of epigenetic therapy and combination immunotherapy. Full article

Background/Objectives: Antibody-based therapies often exhibit limited distribution within solid tumors due to the “binding-site barrier” (BSB). Our group has developed and validated the use of anti-idiotypic distribution enhancers (AIDEs), which transiently block antibody binding, improving intra-tumoral distribution and efficacy. This study evaluated 1HE and LG1, model anti-trastuzumab AIDEs, in combination with trastuzumab–PE24, a highly potent immunotoxin. Methods: The effects of 1HE on the whole-body disposition of radiolabeled trastuzumab were assessed in NCI-N87 tumor-bearing mice. Mechanistic pharmacokinetic/pharmacodynamic (PK/PD) modeling was employed to explore how AIDE binding kinetics influence antibody intra-tumoral distribution and immunotoxin potency. Trastuzumab–PE24 was developed by site-specific conjugation, enabled by self-splicing split intein, with cytotoxicity tested on various cell lines in vitro. The impact of 1HE and LG1 coadministration on trastuzumab–PE24 efficacy was evaluated in NCI-N87 xenograft-bearing mice. Results: 1HE coadministration decreased trastuzumab tumor maximum concentration, reducing tumor terminal slope by 8% and overall tumor exposure by 2.6%, without negatively affecting selectivity. Modeling predicted the optimal AIDE dissociation rate constant for trastuzumab–PE24 to be between 0.015 and 0.3 h⁻¹. The coadministration of trastuzumab–PE24 with 1HE and LG1 improved anti-tumor efficacy and extended median survival to 60 days (p = 0.0002). Conclusions: AIDE coadministration led to minimal negative impacts on overall tumor exposure, consistent with model simulations. AIDE coadministration improved the efficacy of trastuzumab–PE24 in NCI-N87 xenografts. Modeling further predicted that repeated AIDE administration with trastuzumab–PE24 could induce complete tumor regression. These findings highlight the advantages of the AIDE strategy, particularly when coadministered with highly potent immunotoxins. Full article

Effective cancer therapies must address the tumor microenvironment (TME), a complex network of tumor cells and stromal components, including endothelial, immune, and mesenchymal cells. Durable outcomes require targeting both tumor cells and the TME while minimizing systemic toxicity. Interleukin-2 (IL-2)-based therapies have shown efficacy in cancers such as metastatic melanoma and renal cell carcinoma but are limited by severe side effects. Innovative IL-2-based immunotherapeutic approaches include immunotoxins, such as antibody–drug conjugates, immunocytokines, and antibody–cytokine fusion proteins that enhance tumor-specific delivery. These strategies activate cytotoxic CD8⁺ T lymphocytes and natural killer (NK) cells, eliciting a potent Th1-mediated anti-tumor response. Modified IL-2 variants with reduced Treg cell activity further improve specificity and reduce immunosuppression. Additionally, IL-2 conjugates with peptides or anti-angiogenic agents offer improved therapeutic profiles. Combining IL-2-based therapies with immune checkpoint inhibitors (ICIs), anti-angiogenic agents, or radiotherapy has demonstrated synergistic potential. Preclinical and clinical studies highlight reduced toxicity and enhanced anti-tumor efficacy, overcoming TME-driven immune suppression. These approaches mitigate the limitations of high-dose soluble IL-2 therapy, promoting immune activation and minimizing adverse effects. This review critically explores advances in IL-2-based therapies, focusing on immunotoxins, immunocytokines, and IL-2 derivatives. Emphasis is placed on their role in combination strategies, showcasing their potential to target the TME and improve clinical outcomes effectively. Also, the use of IL-2 immunocytokines in “in situ” vaccination to relieve the immunosuppression of the TME is discussed. Full article