Preclinical assessment of a novel human antibody VH domain targeting mesothelin as an antibody-drug conjugate

Peptides based on the interface of hnRNPA2B1-transthyretin complex repress retinal angiogenesis in diabetic retinopathy

BACKGROUND

Heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) plays a vital role in angiogenesis, when its nucleic acid-binding domain is occupied by transthyretin (TTR), the neovascularization of human retinal microvascular endothelial cells (hRECs) is repressed under hyperglycemic conditions.

METHODS

HnRNPA2B1-targeting peptides (THIPs) were designed based on the core fragments at the TTR-hnRNPA2B1 interface. Biacore, Langmuir equilibrium adsorption, and co-immunoprecipitation (co-IP) assays were performed to determine the association between the THIPs and hnRNPA2B1. Proliferation and DNA synthesis in hRECs were detected using CCK-8 and EdU assays. Transwell, wound healing, and tube formation assays were used to evaluate migratory and the angiogenic capacity of hRECs. Related RNA and protein expression levels were tested by quantitative PCR and western blot assays, respectively. Streptozotocin (STZ)-induced diabetic retinopathy (DR) model rats were intravitreally injected with 5 μL of AAV9 virus (1 × 1012 vg/mL) every 8 weeks, with sterile saline used as control. After 16 weeks, the retinas were extracted and subjected to Evans blue leakage and retinal trypsin digestion assays. Retinal paraffin sections were prepared and stained with hematoxylin and eosin (H&E) or subjected to immunohistochemical or immunofluorescence assays.

RESULTS

Biacore, Langmuir equilibrium adsorption, and co-IP analyses demonstrated that the four designed THIPs specifically recognized hnRNPA2B1. CCK-8 and EdU labeling assays showed that the THIPs inhibited proliferation and DNA synthesis in hRECs under hyperglycemia. Transwell, wound healing and tube formation assays demonstrated that the THIPs inhibited the migratory and angiogenic capacity of hRECs. Quantitative PCR and western blot assays suggested that the THIPs exerted their effects via the STAT4/miR-223-3p/FBXW7 and the downstream Notch1/Akt/mTOR axes. In vivo studies using DR model rat revealed that the intravitreal administration of THIP-4 significantly mitigated retinal leakage, capillary decellularization, pericyte loss, fibrosis, and gliosis during DR progression.

CONCLUSION

Our findings demonstrated that under hyperglycemia, THIP-4 suppressed DR progression via the STAT4/miR-223-3p/FBXW7 and Notch1/Akt/mTOR axes both in vitro and in vivo. These results indicated that THIP-4 has strong potential for clinical application in DR and other angiogenesis associated diseases.

A synthetic heavy chain variable domain antibody library (VHL) provides highly functional antibodies with favorable developability

Synthetic antibody libraries have been developed as an efficient source for the discovery of the heavy chain variable (VH) domain, which exhibits low immunogenicity, high tissue penetration, and diverse binding epitopes in therapeutic biopharmaceuticals. In this study, the human IGHV3-23*04 germline gene was chosen as the scaffold with a high expression level and favorable thermal stability. Amino acid diversity was introduced into the complementarity determining region 3 (CDR3) to exclude potential sequence liabilities. A library containing 2.6 × 1011 independent clones was successfully constructed. The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, interleukin-17A (IL17A), B-cell maturation antigen (BCMA), and G-protein coupled receptor family C group 5 member D (GPRC5D) were used as target antigens to screen and identify VHs. In each case, Thirty-one to fifty-five VHs were screened out. The VH-Fc antibodies showed superior affinities (as high as 4.6 nM) to the corresponding antigens but did not bind to antigen-irrelevant cell CHO-S. Furthermore, the anti-RBD and anti-IL17A VH-Fc antibodies showed strong functional activity in the receptor-blocking assays. The VH-Fc antibodies from the synthetic library exhibited favorable developability (thermal stability, colloidal stability, hydrophilicity, anti-aggregation ability, and no interaction with human IgGs). We demonstrated that high-affinity and highly functional VH domain antibodies were generated from the rationally designed library with desired physicochemical properties. This approach is generally universal to target any antigen and has significant potential to accelerate candidate selection.

Applications of Cell-Based Protein Array Technology to Preclinical Safety Assessment of Biological Products

Off-target evaluation is essential in preclinical safety assessments of novel biotherapeutics, supporting lead molecule selection, endpoint selection in toxicology studies, and regulatory requirements for first-in-human trials. Off-target interaction of a therapeutic antibody and antibody derivatives has been historically assessed via the Tissue Cross-Reactivity (TCR) study, in which the candidate molecule is used as a reagent in immunohistochemistry (IHC) to assess binding of the candidate molecule to a panel of human tissue sections. The TCR approach is limited by the performance of the therapeutic as an IHC reagent, which is often suboptimal to outright infeasible. Furthermore, binding of the therapeutic in IHC conditions typically has poor in vitro to in vivo translation and lacks qualitative data of the identity of putative off-targets limiting the decisional value of the data. More recently, cell-based protein arrays (CBPA) that allow for screening against a large portion of the human membrane proteome and secretome have emerged as a complement, and likely a higher value alternative, to IHC-based off-target assessment. These arrays identify specific protein interactions and may be useful for testing nontraditional antibody-based therapeutic formats that are unsuitable for TCR studies. This article presents an overview of CBPA technologies in the context of TCR and off-target assessment studies. Selected case examples and strategic considerations covering a range of different modalities are presented.

Single-Domain Antibodies as Antibody-Drug Conjugates: From Promise to Practice-A Systematic Review

BACKGROUND

Antibody-drug conjugates (ADCs) represent potent cancer therapies that deliver highly toxic drugs to tumor cells precisely, thus allowing for targeted treatment and significantly reducing off-target effects. Despite their effectiveness, ADCs can face limitations due to acquired resistance and potential side effects.

OBJECTIVES

This study focuses on advances in various ADC components to improve both the efficacy and safety of these agents, and includes the analysis of several novel ADC formats. This work assesses whether the unique features of VHHs-such as their small size, enhanced tissue penetration, stability, and cost-effectiveness-make them a viable alternative to conventional antibodies for ADCs and reviews their current status in ADC development.

METHODS

Following PRISMA guidelines, this study focused on VHHs as components of ADCs, examining advancements and prospects from 1 January 2014 to 30 June 2024. Searches were conducted in PubMed, Cochrane Library, ScienceDirect and LILACS using specific terms related to ADCs and single-domain antibodies. Retrieved articles were rigorously evaluated, excluding duplicates and non-qualifying studies. The selected peer-reviewed articles were analyzed for quality and synthesized to highlight advancements, methods, payloads, and future directions in ADC research.

RESULTS

VHHs offer significant advantages for drug conjugation over conventional antibodies due to their smaller size and structure, which enhance tissue penetration and enable access to previously inaccessible epitopes. Their superior stability, solubility, and manufacturability facilitate cost-effective production and expand the range of targetable antigens. Additionally, some VHHs can naturally cross the blood-brain barrier or be easily modified to favor their penetration, making them promising for targeting brain tumors and metastases. Although no VHH-drug conjugates (nADC or nanoADC) are currently in the clinical arena, preclinical studies have explored various conjugation methods and linkers.

CONCLUSIONS

While ADCs are transforming cancer treatment, their unique mechanisms and associated toxicities challenge traditional views on bioavailability and vary with different tumor types. Severe toxicities, often linked to compound instability, off-target effects, and nonspecific blood cell interactions, highlight the need for better understanding. Conversely, the rapid distribution, tumor penetration, and clearance of VHHs could be advantageous, potentially reducing toxicity by minimizing prolonged exposure. These attributes make single-domain antibodies strong candidates for the next generation of ADCs, potentially enhancing both efficacy and safety.

Reforming solid tumor treatment: the emerging potential of smaller format antibody-drug conjugate

In recent years, substantial therapeutic efficacy of antibody-drug conjugates (ADCs) has been validated through approvals of 16 ADCs for the treatment of malignant tumors. However, realization of the maximum clinical use of ADCs requires surmounting extant challenges, mainly the limitations in tumor penetration capabilities when targeting solid tumors. To resolve the hurdle of suboptimal tumor penetration, miniaturized antibody fragments with engineered formats have been harnessed for ADC assembly. By virtue of their reduced molecular sizes, antibody fragment-drug conjugates hold considerable promise for efficacious delivery of cytotoxic agents, thus conferring superior therapeutic outcomes. This review will focus on current advancements in novel ADC development utilizing smaller antibody formats from ~6 to 80 kDa, with particular emphasis on single-domain antibodies, which have been widely applied in novel ADC design. Additionally, strategies to optimize clinical translation are discussed, including half-life extension, acceleration of internalization, and reduction of immunogenic potential.