Development of a novel, fully human, anti-PCSK9 antibody with potent hypolipidemic activity by utilizing phage display-based strategy

Harnessing filamentous phages for enhanced stroke recovery

Stroke poses a critical global health challenge, leading to substantial morbidity and mortality. Existing treatments often miss vital timeframes and encounter limitations due to adverse effects, prompting the pursuit of innovative approaches to restore compromised brain function. This review explores the potential of filamentous phages in enhancing stroke recovery. Initially antimicrobial-centric, bacteriophage therapy has evolved into a regenerative solution. We explore the diverse role of filamentous phages in post-stroke neurological restoration, emphasizing their ability to integrate peptides into phage coat proteins, thereby facilitating recovery. Experimental evidence supports their efficacy in alleviating post-stroke complications, immune modulation, and tissue regeneration. However, rigorous clinical validation is essential to address challenges like dosing and administration routes. Additionally, genetic modification enhances their potential as injectable biomaterials for complex brain tissue issues. This review emphasizes innovative strategies and the capacity of filamentous phages to contribute to enhanced stroke recovery, as opposed to serving as standalone treatment, particularly in addressing stroke-induced brain tissue damage.

PCSK9 inhibitors: current status and emerging frontiers in lipid control

INTRODUCTION

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of global mortality, imposing substantial healthcare economic burdens. Among the modifiable risk factors, hypercholesterolemia, especially elevated low-density lipoprotein cholesterol (LDL-C), plays a pivotal role in ASCVD development. Novel therapies such as PCSK9 (Proprotein Convertase Subtilisin/Kexin type 9) inhibitors are emerging to address this concern. These inhibitors offer the potential to reduce ASCVD risk by directly targeting LDL-C levels.

AREAS COVERED

The article reviews the structural and functional aspects of PCSK9, highlighting its role in LDL receptor regulation. The pharmacological strategies for PCSK9 inhibition, including monoclonal antibodies, binding peptides, gene silencing, and active immunization, are explored. Clinical evidence from various trials underscores the safety and efficacy of PCSK9 inhibitors in reducing LDL-C levels and potentially improving cardiovascular outcomes. Despite these promising results, challenges such as cost-effectiveness and long-term safety considerations are addressed.

EXPERT OPINION

Among PCSK9 inhibitors, monoclonal antibodies represent a cornerstone. Many trials have showed their efficacy in reducing LDL-C and the risk for major adverse clinical events, revealing long-lasting effects, with special benefits particularly for statin-intolerant and familial hypercholesterolemia patients. However, long-term impacts, high costs, and patient selection necessitate further research.

A novel fully human anti-NT-ANGPTL3 antibody from phage display library exhibits potent ApoB, TG, and LDL-C lowering activities in hyperlipidemia mice

Dyslipidemia is characterized by elevated plasma levels of low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and TG-rich lipoprotein (TGRLs) in circulation, and is closely associated with the incidence and development of cardiovascular disease. Angiopoietin-like protein 3 (ANGPTL3) deficiency has been identified as a cause of familial combined hypolipidemia in humans, which allows it to be an important therapeutic target for reducing plasma lipids. Here, we report the discovery and characterization of a novel fully human antibody F1519-D95aA against N-terminal ANGPTL3 (NT-ANGPTL3), which potently inhibits NT-ANGPTL3 with a KD as low as 9.21 nM. In hyperlipidemic mice, F1519-D95aA shows higher apolipoprotein B (ApoB) and TG-lowering, and similar LDL-C reducing activity as compared to positive control Evinacumab (56.50% vs 26.01% decrease in serum ApoB levels, 30.84% vs 25.28% decrease in serum TG levels, 23.32% vs 22.52% decrease in serum LDLC levels, relative to vehicle group). Molecular docking and binding energy calculations reveal that the F1519-D95aA-ANGPTL3 complex (10 hydrogen bonds, -65.51 kcal/mol) is more stable than the Evinacumab-ANGPTL3 complex (4 hydrogen bonds, -63.76 kcal/mol). Importantly, F1519-D95aA binds to ANGPTL3 with different residues in ANGPTL3 from Evinacumab, suggesting that F1519-D95aA may be useful for the treatment of patients resistant to Evinacumab. In conclusion, F1519-D95aA is a novel fully human anti-NT-ANGPTL3 antibody with potent plasma ApoB, TG, and LDL-C lowering activities, which can potentially serve as a therapeutic agent for hyperlipidemia and relevant cardiovascular diseases.

A bifunctional anti-PCSK9 scFv/Exendin-4 fusion protein exhibits enhanced lipid-lowering effects via targeting multiple signaling pathways in HFD-fed mice

Fusion protein which encompasses more than one functional component, has become one of the most important representatives of macromolecular drugs for disease treatment since that monotherapy itself might not be effective enough to eradicate the disease. In this study, we sought to construct a bifunctional antibody fusion protein by fusing anti-PCSK9 scFv with Exendin-4 for simultaneously lowering both LDL-C and TG. Firstly, three Ex4-anti-PCSK9 scFv fusion proteins were constructed by genetically connecting the C-terminal of Exendin-4 to the N-terminal of anti-PCSK9 scFv through various flexible linker peptides (G4S)n (n = 2, 3, 4). After soluble expression in E. coli, the most potent Ex4-(G4S)4-anti-PCSK9 scFv fusion protein was selected based on in vitro activity assays. Then, we investigated the in vivo therapeutic effects of Ex4-(G4S)4-anti-PCSK9 scFv on the serum lipid profile and bodyweight changes as well as underlying molecular mechanism in HFD-fed C57BL/6 mice. The data showed that Ex4-(G4S)4-anti-PCSK9 scFv exhibits enhanced effects of lowering both LDL-C and TG in serum, reducing food intake and body weight via blocking PCSK9/LDLR, activating AMPK/SREBP-1 pathways, and up-regulating sirt6. Conclusively, Ex4-(G4S)4-anti-PCSK9 has the potential to serve as a promising therapeutic agent for effectively treating dyslipidemia with high levels of both LDL-C and TG.

A fully human monoclonal antibody targeting Semaphorin 5A alleviates the progression of rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common chronic autoimmune disease worldwide. Although progress has been made in RA treatment in recent decades, remission cannot be effectively achieved for a considerable proportion of RA patients. Thus, novel potential targets for therapeutic strategies are needed. Semaphorin 5A (SEMA5A) plays a pivotal role in RA progression by facilitating pannus formation, and it is a promising therapeutic target. In this study, we sought to develop an antibody treatment strategy targeting SEMA5A and evaluate its therapeutic effect using a collagen-induced arthritis (CIA) model. We generated SYD12-12, a fully human SEMA5A blocking antibody, through phage display technology. SYD12-12 intervention effectively inhibited angiogenesis and aggressive phenotypes of RA synoviocytes in vitro and dose-dependently inhibited synovial hyperplasia, pannus formation, bone destruction in CIA mice. Notably, SYD12-12 also improved the Treg/Th17 imbalance in CIA mice. We confirmed through immunofluorescence and molecular docking that SYD12-12 integrated with the unique TSP-1 domain of SEMA5A. In conclusion, we developed and characterized a fully human SEMA5A-blocking antibody for the first time. SYD12-12 effectively alleviated disease progression in CIA mice by inhibiting pannus formation and improving the Treg/Th17 imbalance, demonstrating its potential for the RA treatment.

Affinity maturation of antibody fragments: A review encompassing the development from random approaches to computational rational optimization

Routinely screened antibody fragments usually require further in vitro maturation to achieve the desired biophysical properties. Blind in vitro strategies can produce improved ligands by introducing random mutations into the original sequences and selecting the resulting clones under more and more stringent conditions. Rational approaches exploit an alternative perspective that aims first at identifying the specific residues potentially involved in the control of biophysical mechanisms, such as affinity or stability, and then to evaluate what mutations could improve those characteristics. The understanding of the antigen-antibody interactions is instrumental to develop this process the reliability of which, consequently, strongly depends on the quality and completeness of the structural information. Recently, methods based on deep learning approaches critically improved the speed and accuracy of model building and are promising tools for accelerating the docking step. Here, we review the features of the available bioinformatic instruments and analyze the reports illustrating the result obtained with their application to optimize antibody fragments, and nanobodies in particular. Finally, the emerging trends and open questions are summarized.

Isolation and characterization of human anti-CD20 single-chain variable fragment (scFv) from a Naive human scFv library

CD20 is a receptor expressed on B cells with anonymous functions. The receptor is the target of some food and drug administration (FDA) approved monoclonal antibodies (mAb), such as Rituximab and Obinutuzumab. Blocking CD20 using the aforementioned mAbs has improved Non-Hodgkin Lymphoma (NHL) therapy. All commercial mAbs on the market were raised in non-human animal models. Antibody humanization is inevitable to mitigate immune response. In order to keep the affinity of antibody intact, humanizations are only applied to frameworks which do not eliminate immune response to foreign CDRs sequences. To address this issue, human monoclonal antibody deemed imperative. Herein, we report the isolation and characterization of a fully human single-chain variable fragment (scFv) against the large loop of CD20 from naïve human antibody library. After three rounds of phage display, a library of enriched anti-CD20 scFv was obtained. The polyclonal phage ELISA demonstrated that after each round of phage display, the population of anti-CD20 scFv became dominant. The scFv, G7, with the most robust interaction with CD20 was selected for further characterization. The specificity of G7 scFv was evaluated by ELISA, western blot, and flow cytometry. Detecting CD20 in western blot showed that G7 binds to a linear epitope on CD20 large loop. Next, G7 scFv was also bound to Raji cell (CD20⁺) while no interaction was recorded with K562 cell line (CD20^—). This data attested that the epitope recognized by G7 scFv is accessible on the cell membrane. The affinity of G7 scFv was estimated to be 63.41 ± 3.9 nM. Next, the sensitivity was evaluated to be 2 ng/ml. Finally, G7 scFv tertiary structure was modeled using Graylab software. The 3D structure illustrated two domains of variable heavy (V_H) and variable light (V_L) connected through a linker. Afterward, G7 scFv and CD20 were applied to in-silico docking using ClusPro to illustrate the interaction of G7 with the large loop of CD20. As the selected scFv from the human antibody library is devoid of interspecies immunogenic amino acids sequences, no humanization or any other modifications are required prior to clinical applications.

Mechanistic insight into premature atherosclerosis and cardiovascular complications in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with a significant risk of cardiovascular disease (CVD), which substantially increases disease mortality and morbidity. The overall mechanisms associated with the development of premature atherosclerosis and CVD in SLE remain unclear, but has been considered as a result of an intricate interplay between the profound immune dysregulation and traditional CVD risk factors. Aberrant systemic inflammation in SLE may lead to an abnormal lipid profile and dysfunction, which can further fuel the pro-atherosclerotic environment. The existence of a strong imbalance between endothelial damage and vascular repair/angiogenesis promotes vascular injury, which is the early step in the progression of atherosclerotic CVD. Profound innate and adaptive immune dysregulation, characterized by excessive type I interferon burden, aberrant macrophage, platelet and complements activation, neutrophil dysregulation and neutrophil extracellular traps formation, uncontrolled T cell activation, and excessive autoantibody production and immune complex formation, have been proposed to promote accelerated CVD in SLE. While designing targeted therapies to correct the dysregulated immune activation may be beneficial in the treatment of SLE-related CVD, much additional work is needed to determine how to translate these findings into clinical practice. Additionally, a number of biomarkers display diagnostic potentials in improving CVD risk stratification in SLE, further prospective studies will help understand which biomarker(s) will be the most impactful one(s) in assessing SLE-linked CVD. Continued efforts to identify novel mechanisms and to establish criteria for assessing CVD risk as well as predicting CVD progression are in great need to improve CVD outcomes in SLE.

Generation of a Novel High-Affinity Antibody Binding to PCSK9 Catalytic Domain with Slow Dissociation Rate by CDR-Grafting, Alanine Scanning and Saturated Site-Directed Mutagenesis for Favorably Treating Hypercholesterolemia

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) has become an attractive therapeutic strategy for lowering low-density lipoprotein cholesterol (LDL-C). In this study, a novel high affinity humanized IgG1 mAb (named h5E12-L230G) targeting the catalytic domain of human PCSK9 (hPCSK9) was generated by using CDR-grafting, alanine-scanning mutagenesis, and saturated site-directed mutagenesis. The heavy-chain constant region of h5E12-L230G was modified to eliminate the cytotoxic effector functions and mitigate the heterogeneity. The biolayer interferometry (BLI) binding assay and molecular docking study revealed that h5E12-L230G binds to the catalytic domain of hPCSK9 with nanomolar affinity (K_D = 1.72 nM) and an extremely slow dissociation rate (k_off, 4.84 × 10⁻⁵ s⁻¹), which interprets its quite low binding energy (−54.97 kcal/mol) with hPCSK9. Additionally, h5E12-L230G elevated the levels of LDLR and enhanced the LDL-C uptake in HepG2 cells, as well as reducing the serum LDL-C and total cholesterol (TC) levels in hyperlipidemic mouse model with high potency comparable to the positive control alirocumab. Our data indicate that h5E12-L230G is a high-affinity anti-PCSK9 antibody candidate with an extremely slow dissociation rate for favorably treating hypercholesterolemia and relevant cardiovascular diseases.

Potential of Phage Display Antibody Technology for Cardiovascular Disease Immunotherapy

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. CVD includes coronary artery diseases such as angina, myocardial infarction, and stroke. "Lipid hypothesis" which is also known as the cholesterol hypothesis proposes the linkage of plasma cholesterol level with the risk of developing CVD. Conventional management involves the use of statins to reduce the serum cholesterol levels as means for CVD prevention or treatment. The regulation of serum cholesterol levels can potentially be regulated with biological interventions like monoclonal antibodies. Phage display is a powerful tool for the development of therapeutic antibodies with successes over the recent decade. Although mainly for oncology, the application of monoclonal antibodies as immunotherapeutic agents could potentially be expanded to CVD. This review focuses on the concept of phage display for antibody development and discusses the potential target antigens that could potentially be beneficial for serum cholesterol management.