Challenges and opportunities for monoclonal antibody therapy in veterinary oncology

First site-specific conjugation method for native goat IgG antibodies via glycan remodeling at the conserved Fc region

Despite their triumph in treating human diseases, antibody therapies for animals have gained momentum more slowly. However, the first approvals of animal antibodies for osteoarthritic pain in cats and dogs may herald the dawn of a new era. For example, goats are vital to economies around the world for their milk, meat, and hide products. It is therefore imperative to develop therapies to safeguard goats-with antibodies at the forefront. Goat antibodies will be crucial in the development of therapeutic antibodies, for example, as tracers to study antibody distribution in vivo, reagents to develop other therapeutic antibodies, and therapeutic agents themselves (e.g., antibody-drug conjugates). Hamstringing this effort is a still-burgeoning understanding of goat antibodies and their derivatization. Historically, goat antibody conjugates were generated through stochastic chemical modifications, producing numerous attachment sites and modification ratios, thereby deleteriously impacting antigen binding. Site-specific methods exist but often require substantial engineering and have not been demonstrated with goat antibodies. Nevertheless, we present herein a novel method to site-specifically conjugate native goat antibodies: chemo-enzymatic remodeling of the native Fc N-glycan introduces a reactive azide handle, after which click chemistry with strained alkyne partners affords homogeneous conjugates labeled only on the Fc domain. This process is robust, and resulting conjugates retain their antigen binding and specificity. To our knowledge, our report is the first for site-specific conjugation of native goat antibodies. Furthermore, our approach should be applicable to other animal antibodies-even with limited structural information-with similar success.

Investigating Cox-2 and EGFR as Biomarkers in Canine Oral Squamous Cell Carcinoma: Implications for Diagnosis and Therapy

Oral squamous cell carcinoma (OSCC) is a common and highly aggressive dog tumor known for its local invasiveness and metastatic potential. Understanding the molecular mechanisms driving the development and progression of OSCC is crucial for improving diagnostic and therapeutic strategies. Additionally, spontaneous oral squamous cell carcinomas in dogs are an excellent model for studying human counterparts. In this study, we aimed to investigate the significance of two key molecular components, Cox-2 and EGFR, in canine OSCC. We examined 34 tumor sections from various dog breeds to assess the immunoexpression of Cox-2 and EGFR. Our findings revealed that Cox-2 was highly expressed in 70.6% of cases, while EGFR overexpression was observed in 44.1%. Cox-2 overexpression showed association with histological grade of malignancy (HGM) (p = 0.006) and EGFR with vascular invasion (p = 0.006). COX-2 and EGFR concurrent expression was associated with HGM (p = 0.002), as well as with the presence of vascular invasion (p = 0.002). These data suggest that Cox-2 and EGFR could be promising biomarkers and potential therapeutic targets, opening avenues for developing novel treatment strategies for dogs affected by OSCC. Further studies are warranted to delve deeper into these findings and translate them into clinical practice.

A Scoping Review on Tyrosine Kinase Inhibitors in Cats: Current Evidence and Future Directions

Tyrosine kinase inhibitors (TKIs) have become invaluable in the treatment of human and canine malignancies, but their role in feline oncology is less defined. While toceranib phosphate and masitinib mesylate are licensed for use in dogs, no TKI is yet approved for cats. This review systematically maps the research conducted on the expression of tyrosine kinases in neoplastic and non-neoplastic domestic feline tissues, as well as the in vitro/in vivo use of TKIs in domestic cats. We identify and discuss knowledge gaps and speculate on the further research and potential indications for TKI use in cats. A comprehensive search of three electronic databases and relevant paper reference lists identified 139 studies meeting the inclusion criteria. The most commonly identified tumors were mast cell tumors (MCTs), mammary and squamous cell carcinomas and injection-site sarcomas. Based on the current literature, toceranib phosphate appears to be the most efficacious TKI in cats, especially against MCTs. Exploring the clinical use of TKIs in mammary carcinomas holds promise. Despite the progress, currently, the evidence falls short, underscoring the need for further research to discover new indications in feline oncology and to bridge the knowledge gaps between human and feline medicine.

In Silico and In Vitro Evaluation of Bevacizumab Biosimilar MB02 as an Antitumor Agent in Canine Mammary Carcinoma

Canine mammary carcinomas (CMC) are associated with major aggressive clinical behavior and high mortality. The current standard of care is based on surgical resection, without an established effective treatment scheme, highlighting the urgent need to develop novel effective therapies. Vascular endothelial growth factor (VEGF) is a key regulator of tumor angiogenesis and progression in the majority of solid cancers, including human and canine mammary carcinomas. The first therapy developed to target VEGF was bevacizumab, a recombinant humanized monoclonal antibody, which has already been approved as an anticancer agent in several human cancers. The goal of this work was to establish the therapeutic value of MB02 bevacizumab biosimilar in CMC. First, through different in silico approaches using the MUSCLE multiple-sequence alignment tool and the FoldX protein design algorithm, we were able to predict that canine VEGF is recognized by bevacizumab, after showing an extremely high sequence similarity between canine and human VEGF. Further, by using an ELISA-based in vitro binding assay, we confirmed that MB02 biosimilar was able to recognize canine VEGF. Additionally, canine VEGF-induced microvascular endothelial cell proliferation was inhibited in a concentration-dependent manner by MB02 biosimilar. These encouraging results show a high potential for MB02 as a promising therapeutic agent for the management of CMC.

Potential Promises and Perils of Human Biological Treatments for Immunotherapy in Veterinary Oncology

The emergence of immunotherapy for the treatment of human cancers has heralded a new era in oncology, one that is making its way into the veterinary clinic. As the immune system of many animal species commonly seen by veterinarians is similar to humans, there is great hope for the translation of human therapies into veterinary oncology. The simplest approach for veterinarians would be to adopt existing reagents that have been developed for human medicine, due to the potential of reduced cost and the time it takes to develop a new drug. However, this strategy may not always prove to be effective and safe with regard to certain drug platforms. Here, we review current therapeutic strategies that could exploit human reagents in veterinary medicine and also those therapies which may prove detrimental when human-specific biological molecules are used in veterinary oncology. In keeping with a One Health framework, we also discuss the potential use of single-domain antibodies (sdAbs) derived from camelid species (also known as Nanobodies™) for therapies targeting multiple veterinary animal patients without the need for species-specific reformulation. Such reagents would not only benefit the health of our veterinary species but could also guide human medicine by studying the effects of outbred animals that develop spontaneous tumors, a more relevant model of human diseases compared to traditional laboratory rodent models.

Anti-EGFR monoclonal antibody Cetuximab displays potential anti-cancer activities in feline oral squamous cell carcinoma cell lines

Feline oral squamous cell carcinoma (FOSCC) is a malignant tumor characterized by an aggressive behavior and poor prognosis, for which no fully effective therapies are available. Studies of comparative oncology suggest that epidermal growth factor receptor (EGFR) may be a therapeutic target in FOSCC, similarly to human head and neck SCC (HNSCC), where the use of anti-EGFR monoclonal antibody Cetuximab has entered the clinical practice. The aim of this study was to assess the efficacy of Cetuximab in three validated preclinical models of FOSCC (SCCF1, SCCF2, SCCF3). Sequencing of tyrosine kinase domain of EGFR in the cell lines revealed a wild-type genotype, excluding the presence of activating mutations. Western blotting experiments demonstrated that Cetuximab inhibited activation of EGFR and its downstream kinase Akt in SCCF1, SCCF2 and SCCF3 along with HNSCC cell line CAL 27 included as control. Importantly, CCK-8 and trypan blue exclusion assays revealed that treatment with Cetuximab caused a decrease in cell proliferation and cell viability in all cell lines, with a general dose- and time-dependent trend. Cell death induced by Cetuximab was associated with cleavage of PARP, indicating occurrence of apoptosis. Taken together, our data suggest that Cetuximab exerts potential anti-cancer activities in FOSCC, paving the way for future translational studies aimed at assessing its employment in the therapy of this lethal cancer of cats.

The Use of Oncept Melanoma Vaccine in Veterinary Patients: A Review of the Literature

The Oncept melanoma vaccine is xenogeneic DNA vaccine targeting tyrosinase. It is USDA approved for treatment of stage II to III canine oral melanoma and is also used off-label for melanomas arising in other locations and in other species. While the vaccine appears safe, the published data is mixed as to whether it provides a survival benefit, and the use of the vaccine is somewhat controversial in the veterinary oncology community. In this paper, the published literature describing the use of Oncept is reviewed and evaluated.

The Dog as a Model to Study the Tumor Microenvironment

Cancer is a complex and dynamic disease with an outcome that depends on a strict crosstalk between tumor cells and other components in tumor microenvironment, namely, tumor-infiltrating immune cells, fibroblasts, cancer stem cells, adipocytes, and endothelial cells. Within the tumor microenvironment, macrophages and T-lymphocytes appear to be key effectors during the several steps of tumor initiation and progression. Tumor cells, through the release of a plethora of signaling molecules, can induce immune tolerance, by avoiding immune surveillance, and inhibit immune cells cytotoxic functions. Furthermore, as the tumor grows, tumor microenvironment reveals a series of dysfunctional conditions that potentiate a polarization of harmful humoral Th2 and Th17, an upregulation of Treg cells, and a differentiation of macrophages into the M2 subtype, which contribute to the activation of several signaling pathways involving important tissue biomarkers (COX-2, EGFR, VEGF) implicated in cancer aggressiveness and poor clinical outcomes. In order to maintain the tumor growth, cancer cells acquire several adaptations such as neovascularization and metabolic reprogramming. An extensive intracellular production of lactate and protons is observed in tumor cells as a result of their high glycolytic metabolism. This contributes not only for the microenvironment pH alteration but also to shape the immune response that ultimately impairs immune cells capabilities and effector functions.In this chapter, the complexity of tumor microenvironment, with special focus on macrophages, T-lymphocytes, and the impact of lactate efflux, was reviewed, always trying to demonstrate the strong similarities between data from studies of humans and dogs, a widely proposed model for comparative oncology studies.

Generation and Characterization of a Spike Glycoprotein Domain A-Specific Neutralizing Single-Chain Variable Fragment against Porcine Epidemic Diarrhea Virus

The emergence of the genotype (G) 2 and re-emergence of the G1 porcine epidemic diarrhea virus (PEDV) has caused severe economic impacts in the past decade. Developments of efficient vaccines against new variants of PEDV have been challenging, not least because of the difficulties in eliciting mucosal and lactogenic immunity. A single-chain fragment variable (scFv) capable of efficient antigen recognition is an alternative to vaccination and treatment of a viral infection. In the present study, the variable regions of the light chain and the heavy chain of a G2b PEDV spike domain A (S1^A)-specific neutralizing monoclonal antibody (mAb) were sequenced, constructed with a (G4S) x3 linker, and produced by a mammalian protein expression system. Our results demonstrated that the PEDV S1^A domain scFv was able to bind to S proteins of both G1 and G2b PEDVs. Nevertheless, the scFv was only capable of neutralizing the homologous G2b PEDV but not the G1 PEDV. The binding ability of the G2b-specific neutralizing scFv was not able to predict the neutralizing ability toward heterologous PEDV. The anti-PEDV S1^A scFv presented herein serves as a potential therapeutic candidate against the virulent G2b PEDV.

Generation and Validation of an Antibody to Canine CD19 for Diagnostic and Future Therapeutic Purposes

The B-cell coreceptor, CD19 is a transmembrane protein expressed throughout B-cell ontogeny from pro-B cell to plasmablast. It plays an important role in B-cell development and function and is an attractive target for antibody-directed immunotherapies against B-cell malignancies, including acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), and non-Hodgkin lymphoma (B-NHL) in humans. With the rapid development of next-generation immunotherapies aimed at improving therapeutic efficacy, there is a pressing need for a clinically relevant, immune-competent, spontaneous animal model to derisk these new approaches and inform human immunotherapy clinical trials. Pet dogs develop spontaneous B-cell malignancies, including B-NHL and leukemias that share comparable oncogenic pathways and similar immunosuppressive features to human B-cell malignancies. Despite treatment with multiagent chemotherapy, durable remissions in canine B-NHL are rare and most dogs succumb to their disease within 1 year of diagnosis. Here we report the development and validation of an anti-canine CD19-targeting monoclonal antibody and its single-chain derivatives, which enable next-generation CD19-targeted immunotherapies to be developed and evaluated in client-owned dogs with spontaneous B-NHL. These future in vivo studies aim to provide important information regarding the safety and therapeutic efficacy of CD19-targeted mono- and combination therapies and identify correlative biomarkers of response that will help to inform human clinical trial design. In addition, development of canine CD19-targeted immunotherapies aims to provide better therapeutic options for pet dogs diagnosed with B-cell malignancies.

Comparative aspects of canine and human inflammatory breast cancer

Inflammatory breast cancer (IBC) in humans is the most aggressive form of mammary gland cancer and shares clinical, pathologic, and molecular patterns of disease with canine inflammatory mammary carcinoma (CIMC). Despite the use of multimodal therapeutic approaches, including targeted therapies, the prognosis for IBC/CIMC remains poor. The aim of this review is to critically analyze IBC and CIMC in terms of biology and clinical features. While rodent cancer models have formed the basis of our understanding of cancer biology, the translation of this knowledge into improved outcomes has been limited. However, it is possible that a comparative "one health" approach to research, using a natural canine model of the disease, may help advance our knowledge on the biology of the disease. This will translate into better clinical outcomes for both species. We propose that CIMC has the potential to be a useful model for developing and testing novel therapies for IBC. Further, this strategy could significantly improve and accelerate the design and establishment of new clinical trials to identify novel and improved therapies for this devastating disease in a more predictable way.

Barking up the right tree: advancing our understanding and treatment of lymphoma with a spontaneous canine model

PURPOSE OF REVIEW

Spontaneous lymphoma in pet dogs is increasingly recognized as an ideal model for studying the disease in humans and for developing new targeted therapeutics for patients. Increasing interest by funding agencies, the private sector, and multidisciplinary academic collaborations between different disciplines and sectors now enables large knowledge gaps to be addressed and provides additional proof-of-concept examples to showcase the significance of the canine model.

RECENT FINDINGS

The current review addresses the rationale for a canine lymphoma model including the valuable role it can play in drug development, serving as a link between mouse xenograft models and human clinical trials and the infrastructure that is now in place to facilitate these studies. Research in this field has focused on filling in the gaps to make the canine lymphoma model more robust. These advances have included work on biomarkers, detection of minimal residual disease, expansion of genomic and proteomic data, and immunotherapy.

SUMMARY

Incorporating pet dogs into the drug development pipeline can improve the efficiency and predictability of preclinical models and decrease the time and cost required for a therapeutic target to be translated into clinical benefit.

Multi-parametric analysis reveals enhanced G2-phase arrest of an optimized anti-HER2 antibody to inhibit breast cancer

OBJECTIVES

To find a "me-better" antibody by epitope-specific antibody optimization and multi-parametric analysis.

RESULTS

Using epitope-specific library based on the commercial drug, Pertuzumab/2C4, we screened a novel human anti-HER2 antibody, MIL5, which has slightly higher affinity than the drug. MIL5 and 2C4 share the same epitope to bind HER2; however, MIL5 bound to HER2 His235-His245 more tightly than 2C4, which could be the main reason of its enhanced affinity. In vivo experiments also showed MIL5 had stronger anti-cancer activity than 2C4; however, the classical flow cytometry assays to detect cell apoptosis or cycling did not show convincing evidence of the advantages of MIL5. Thus we introduced the multi-parameter in-cell analysis method to evaluate the superiority of MIL5 to 2C4 in arresting cancer cells in G2-phase to inhibit cell growth and/or proliferation.

CONCLUSION

Multi-parametric method confirmed stronger arrest of G2 by MIL5 to show better anti-cancer function both in vitro and in vivo than 2C4.