Anti-MET VHH Pool Overcomes MET-Targeted Cancer Therapeutic Resistance

Promising Diagnostic and Therapeutic Approaches Based on VHHs for Cancer Management

The discovery of the distinctive structure of heavy chain-only antibodies in species belonging to the Camelidae family has elicited significant interest in their variable antigen binding domain (VHH) and gained attention for various applications, such as cancer diagnosis and treatment. This article presents an overview of the characteristics, advantages, and disadvantages of VHHs as compared to conventional antibodies, and their usage in diverse applications. The singular properties of VHHs are explained, and several strategies that can augment their utility are outlined. The preclinical studies illustrating the diagnostic and therapeutic efficacy of distinct VHHs in diverse formats against solid cancers are summarized, and an overview of the clinical trials assessing VHH-based agents in oncology is provided. These investigations demonstrate the enormous potential of VHHs for medical research and healthcare.

Engineering hydrophobicity and manufacturability for optimized biparatopic antibody-drug conjugates targeting c-MET

Optimal combinations of paratopes assembled into a biparatopic antibody have the capacity to mediate high-grade target cross-linking on cell membranes, leading to degradation of the target, as well as antibody and payload delivery in the case of an antibody-drug conjugate (ADC). In the work presented here, molecular docking suggested a suitable paratope combination targeting c-MET, but hydrophobic patches in essential binding regions of one moiety necessitated engineering. In addition to rational design of HCDR2 and HCDR3 mutations, site-specific spiking libraries were generated and screened in yeast and mammalian surface display approaches. Comparative analyses revealed similar positions amendable for hydrophobicity reduction, with a broad combinatorial diversity obtained from library outputs. Optimized variants showed high stability, strongly reduced hydrophobicity, retained affinities supporting the desired functionality and enhanced producibility. The resulting biparatopic anti-c-MET ADCs were comparably active on c-MET expressing tumor cell lines as REGN5093 exatecan DAR6 ADC. Structural molecular modeling of paratope combinations for preferential inter-target binding combined with protein engineering for manufacturability yielded deep insights into the capabilities of rational and library approaches. The methodologies of in silico hydrophobicity identification and sequence optimization could serve as a blueprint for rapid development of optimal biparatopic ADCs targeting further tumor-associated antigens in the future.

A novel bivalent anti-c-MET/PD-1 bispecific antibody exhibits potent cytotoxicity against c-MET/PD-L1-positive colorectal cancer

Previously, we generated a novel bispecific antibody (BsAb) simultaneously targeting both c-MET and PD-1 (PDCD1), which can bridge T cells and c-MET positive tumor cells. However, the specific mechanisms and antitumor activities of the BsAb against c-MET/PD-L1 (CD274) positive colorectal cancer (CRC) is not completely understood. In this study, in addition to the tumor intrinsic mechanism investigation with molecular biology assay in vitro, a humanized mouse model was used to evaluate antitumor activity of the BsAb in vivo. The BsAb could inhibit c-MET/PD-L1+ CRC cell migration and show strong antitumor activity against HCT116 tumors in mice, potentially by inducing the degradation of c-MET protein in a dose and time-dependent manner. The BsAb could suppress the phosphorylation of c-MET downstream proteins GRB2-associated-binding protein 1 (Gab1) and focal adhesion kinase (FAK). Considering the tumor extrinsic mechanism, the BsAb may promote phagocytosis of macrophage. Furthermore, the level of plasma exosomal-c-MET/PD-L1 is able to distinguish CRC patients from healthy controls. In summary, the BsAb exhibited potent anti-tumor activities by two distinguished mechanisms: inhibition of c-MET signal transduction and promotion of macrophage-mediated phagocytosis. Our BsAb may provide a novel therapeutic agent for patients with c-MET/PD-L1+ CRC, and the status of exosomal-c-MET/PD-L1 can serve as a biomarker to predict responsiveness to treatment of our BsAb.

Single domain Camelid antibody fragments for molecular imaging and therapy of cancer

Despite innovations in cancer therapeutics, cancer remains associated with high mortality and is one of biggest health challenges worldwide. Therefore, developing precise cancer imaging and effective treatments is an unmet clinical need. A relatively novel type of therapeutics are heavy chain variable domain antibody fragments (VHHs) derived from llamas. Here, we explored the suitability of VHHs for cancer imaging and therapy through reviewing the existing literature. We searched the MEDLINE, EMBASE and Cochrane databases and identified 32 papers on molecular imaging and 41 papers on therapy that were suitable for comprehensive reviewing. We found that VHHs harbor a higher specificity and affinity compared to mAbs, which contributes to high-quality imaging and less side-effects on healthy cells. The employment of VHHs in cancer imaging showed remarkably shorter times between administration and imaging. Studies showed that 18F and 99mTc are two optimal radionuclides for imaging with VHHs and that site-specific labelling is the optimal conjugation modality for VHHs with radionuclide or fluorescent molecules. We found different solutions for reducing kidney retention and immunogenicity of VHHs. VHHs as anticancer therapeutics have been tested in photodynamic therapy, targeted radionuclide therapy, immunotherapy and molecular targeted therapy. These studies showed that VHHs target unique antigen epitopes, which are distinct from the ones recognized by mAbs. This advantage means that VHHs may be more effective for targeted anticancer therapy and can be combined with mAbs. We found that high cellular internalization and specificity of VHHs contributes to the effectiveness and safety of VHHs as anticancer therapeutics. Two clinical trials have confirmed that VHHs are effective and safe for cancer imaging and therapy. Together, VHHs seem to harbor several advantages compared to mAbs and show potential for application in personalized treatment for cancer patients. VHH-based imaging and therapy are promising options for improving outcomes of cancer patients.

Development of a MET-targeted single-chain antibody fragment as an anti-oncogene targeted therapy for breast cancer

The usage of monoclonal antibodies (mAbs) and antibody fragments, as a matter associated with the biopharmaceutical industry, is increasingly growing. Harmonious with this concept, we designed an exclusive modeled single-chain variable fragment (scFv) against mesenchymal-epithelial transition (MET) oncoprotein. This scFv was newly developed from Onartuzumab sequence by gene cloning, and expression using bacterial host. Herein, we examined its preclinical efficacy for the reduction of tumor growth, invasiveness and angiogenesis in vitro and in vivo. Expressed anti-MET scFv demonstrated high binding capacity (48.8%) toward MET-overexpressing cancer cells. The IC₅₀ value of anti-MET scFv against MET-positive human breast cancer cell line (MDA-MB-435) was 8.4 µg/ml whereas this value was measured as 47.8 µg/ml in MET-negative cell line BT-483. Similar concentrations could also effectively induce apoptosis in MDA-MB-435 cancer cells. Moreover, this antibody fragment could reduce migration and invasion in MDA-MB-435 cells. Grafted breast tumors in Balb/c mice showed significant tumor growth suppression as well as reduction of blood-supply in response to recombinant anti-MET treatment. Histopathology and immunohistochemical assessments revealed higher rate of response to therapy. In our study, we designed and synthetized a novel anti-MET scFv which could effectively suppress MET-overexpressing breast cancer tumors.

Antibody variable region engineering for improving cancer immunotherapy

The efficacy and specificity of conventional monoclonal antibody (mAb) drugs in the clinic require further improvement. Currently, the development and application of novel antibody formats for improving cancer immunotherapy have attracted much attention. Variable region-retaining antibody fragments, such as antigen-binding fragment (Fab), single-chain variable fragment (scFv), bispecific antibody, and bi/trispecific cell engagers, are engineered with humanization, multivalent antibody construction, affinity optimization and antibody masking for targeting tumor cells and killer cells to improve antibody-based therapy potency, efficacy and specificity. In this review, we summarize the application of antibody variable region engineering and discuss the future direction of antibody engineering for improving cancer therapies.

A review of plant-based expression systems as a platform for single-domain recombinant antibody production

Monoclonal antibodies have contributed to improving the treatment of several diseases. However, limitations related to pharmacokinetic parameters and production costs have instigated the search for alternative products. Camelids produce functional immunoglobulins G devoid of light chains and CH1 domains, in which the antigenic recognition site is formed by a single domain called VHH or nanobody. VHHs' small size and similarity to the human VH domain contribute to high tissue penetration and low immunogenicity. In addition, VHHs provide superior antigen recognition compared to human antibodies, better solubility and stability. Due to these characteristics and the possibility of obtaining gene-encoding VHHs, applications of this biological tool, whether as a monomer or in related recombinant constructs, have been reported. To ensure antibody efficacy and cost-effectiveness, strategies for their expression, either using prokaryotic or eukaryotic systems, have been utilized. Plant-based expression systems are useful for VHH related constructs that require post-translational modifications. This system has exhibited versatility, low-cost upstream production, and safety. This article presents the main advances associated to the heterologous expression of VHHs in plant systems. Besides, we show insights related to the use of VHHs as a strategy for plant pathogen control and a tool for genomic manipulation in plant systems.

Reviving the role of MET in liver cancer therapy and vaccination: an autophagic perspective

Past failures in clinical trials have dampened the enthusiasm for studying the HGF receptor MET and postponed the development of MET-targeted drugs for cancer therapy. However, new evidence suggests that, at least in liver cancer, MET is still a promising therapeutic target, and may also be a potential target for cancer vaccines. This paper briefly highlights novel research advances in this rapidly-evolving field in the perspective of autophagy, and discusses future directions for further investigation of MET-based cancer therapy and vaccination.

The AKT-independent MET-V-ATPase-MTOR axis suppresses liver cancer vaccination

Despite recent progress in hepatitis treatment, there have been no significant advances in the development of liver cancer vaccines in recent years. In this study, we investigated the regulatory effect and potential mechanism of hepatocyte growth factor receptor (MET, also known as HGFR) on tumor vaccinations for liver cancer in mice. Herein, we demonstrate that MET expression is significantly associated with the immunogenicity of liver cancer in mice and humans, and that MET depletion dramatically enhances the protective efficacy of chemotherapy-based anti-liver cancer vaccination. Mechanistically, MET repressed liver cancer immunogenicity independent of the traditional PI3K–AKT cascade, and MET interacted with vacuolar ATP synthase (V-ATPase) and mediated the activation of mammalian target of rapamycin (MTOR), thus suppressing liver cancer immunogenicity. The efficacy of chemotherapy-based liver cancer vaccination was markedly enhanced by targeting the MET–V-ATPase–MTOR axis, highlighting a translational strategy for identifying MET-associated drug candidates for cancer prevention.

Suppression of c-Met-Overexpressing Tumors by a Novel c-Met/CD3 Bispecific Antibody

INTRODUCTION

Overexpression of c-Met, or hepatocyte growth factor (HGF) receptor, is commonly observed in tumor biopsies and often associated with poor patient survival, which makes HGF/c-Met pathway an attractive molecular target for cancer therapy. A number of antibody-based therapeutic strategies have been explored to block c-Met or HGF in cancers; however, clinical efficacy has been very limited, indicating that blockade of c-Met signal alone is not sufficient. Thus, an alternative approach is to develop an immunotherapy strategy for c-Met-overexpressing cancers. c-Met/CD3 bispecific antibody (BsAb) could bridge CD3-positive T lymphocytes and tumor cells to result in potent tumor cell killing.

MATERIALS AND METHODS

A bispecific antibody, BS001, which binds both c-Met and CD3, was generated using a novel BsAb platform. Western blotting and T cells-mediated killing assays were utilized to evaluate the BsAb's effects on cell proliferation, survival and signal transduction in tumor cells. Subcutaneous tumor mouse models were used to analyze the in vivo anti-tumor effects of the bispecific antibody and its combination therapy with PD-L1 antibody.

RESULTS

BS001 showed potent T-cell mediated tumor cells killing in vitro. Furthermore, BS001 inhibited phosphorylation of c-Met and downstream signal transduction in tumor cells. In A549 lung cancer xenograft model, BS001 inhibited tumor growth and increased the proportion of activated CD56+ tumor infiltrating lymphocytes. In vivo combination therapy of BS001 with Atezolizumab (an anti-programmed cell death protein1-ligand (PD-L1) antibody) showed more potent tumor inhibition than monotherapies. Similarly, in SKOV3 xenograft model, BS001 showed a significant efficacy in tumor growth inhibition and tumor recurrence was not observed in more than half of mice treated with a combination of BS001 and Pembrolizumab.

CONCLUSION

c-Met/CD3 bispecific antibody BS001 exhibited potent anti-tumor activities in vitro and in vivo, which was achieved through two distinguished mechanisms: through antibody-mediated tumor cell killing by T cells and through inhibition of c-Met signal transduction.

Targeting the HGF/MET Axis in Cancer Therapy: Challenges in Resistance and Opportunities for Improvement

Among hundreds of thousands of signal receptors contributing to oncogenic activation, tumorigenesis, and metastasis, the hepatocyte growth factor (HGF) receptor - also called tyrosine kinase MET - is a promising target in cancer therapy as its axis is involved in several different cancer types. It is also associated with poor outcomes and is involved in the development of therapeutic resistance. Several HGF/MET-neutralizing antibodies and MET kinase-specific small molecule inhibitors have been developed, resulting in some context-dependent progress in multiple cancer treatments. Nevertheless, the concomitant therapeutic resistance largely inhibits the translation of such targeted drug candidates into clinical application. Until now, numerous studies have been performed to understand the molecular, cellular, and upstream mechanisms that regulate HGF/MET-targeted drug resistance, further explore novel strategies to reduce the occurrence of resistance, and improve therapeutic efficacy after resistance. Intriguingly, emerging evidence has revealed that, in addition to its conventional function as an oncogene, the HGF/MET axis stands at the crossroads of tumor autophagy, immunity, and microenvironment. Based on current progress, this review summarizes the current challenges and simultaneously proposes future opportunities for HGF/MET targeting for therapeutic cancer interventions.

USP22 Deubiquitinates CD274 to Suppress Anticancer Immunity

PD-1 (CD279)-PD-L1 (CD274) inhibitory signaling is critical for cancer immune evasion, and thus has become one of the major targets in anticancer immunotherapy. There are several studies that demonstrate the potent effects of posttranslational modifications of CD274 on immune inactivation and suppression, such as ubiquitination, phosphorylation, glycosylation, and palmitoylation. However, the regulatory mechanisms for CD274 deubiquitination are still largely unclear. Here, we identified ubiquitin-specific protease 22 (USP22) as a novel deubiquitinase of CD274. USP22 directly interacted with the C terminus of CD274, inducing its deubiquitination and stabilization. Across multiple cancer types, USP22 was highly expressed and frequently altered in liver cancer, closely correlating with poor prognosis of these patients. Genetic depletion of USP22 inhibited liver cancer growth in an immune system-dependent manner, increased tumor immunogenicity and tumor-infiltrating lymphocytes, and improved therapeutic efficacy of CD274-targeted immunotherapy and CDDP-based chemotherapy in mice. We demonstrate that targeting USP22 is a promising strategy to potentiate anticancer immunity for CD274-amplified cancer.

Generation and Application of Fluorescent Anti-Human β2-Microglobulin VHHs via Amino Modification

The functionalization of VHHs enables their application in almost every aspect of biomedical inquiry. Amino modification remains a common strategy for protein functionalization, though is considered to be inferior to site-specific methods and cause protein property changes. In this paper, four anti-β2M VHHs were selected and modified on the amino group by NHS-Fluo. The impacts of amino modification on these VHHs were drastically different, and among all th examples, the modified NB-1 maintained the original stability, bioactivity and homogeneity of unmodified NB-1. Specific recognition of VHHs targeting β2M detected by fluorescence imaging explored the possible applications of VHHs. Via this study, we successfully functionalized the anti-β2M VHHs through amino modification and the results are able to instruct the simple and fast functionalization of VHHs in biomedical researches.