Nanobodies® † †Nanobody is a registered trademark of Ablynx NV. as inhaled biotherapeutics for lung diseases

Current development of severe acute respiratory syndrome coronavirus 2 neutralizing antibodies (Review)

The coronavirus disease 2019 pandemic due to severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) seriously affected global public health security. Studies on vaccines, neutralizing antibodies (NAbs) and small molecule antiviral drugs are currently ongoing. In particular, NAbs have emerged as promising therapeutic agents due to their well‑defined mechanism, high specificity, superior safety profile, ease of large‑scale production and simultaneous application for both prevention and treatment of viral infection. Numerous NAb therapeutics have entered the clinical research stages, demonstrating promising therapeutic and preventive effects. These agents have been used for outbreak prevention and control under urgent authorization processes. The present review summarizes the molecular targets of SARS‑CoV‑2‑associated NAbs and screening and identification techniques for NAb development. Moreover, the current shortcomings and challenges that persist with the use of NAbs are discussed. The aim of the present review is to offer a reference for the development of NAbs for any future emergent infectious diseases, including SARS‑CoV‑2.

Single-Domain Antibodies-Novel Tools to Study and Treat Allergies

IgE-mediated allergies represent a major health problem in the modern world. Apart from allergen-specific immunotherapy (AIT), the only disease-modifying treatment, researchers focus on biologics that target different key molecules such as allergens, IgE, or type 2 cytokines to ameliorate allergic symptoms. Single-domain antibodies, or nanobodies, are the newcomers in biotherapeutics, and their huge potential is being investigated in various research fields since their discovery 30 years ago. While they are dominantly applied for theranostics of cancer and treatment of infectious diseases, nanobodies have become increasingly substantial in allergology over the last decade. In this review, we discuss the prerequisites that we consider to be important for generating useful nanobody-based drug candidates for treating allergies. We further summarize the available research data on nanobodies used as allergen monitoring and detection probes and for therapeutic approaches. We reflect on the limitations that have to be addressed during the development process, such as in vivo half-life and immunogenicity. Finally, we speculate about novel application formats for allergy treatment that might be available in the future.

Nanobody engineering: computational modelling and design for biomedical and therapeutic applications

Nanobodies, the smallest functional antibody fragment derived from camelid heavy-chain-only antibodies, have emerged as powerful tools for diverse biomedical applications. In this comprehensive review, we discuss the structural characteristics, functional properties, and computational approaches driving the design and optimisation of synthetic nanobodies. We explore their unique antigen-binding domains, highlighting the critical role of complementarity-determining regions in target recognition and specificity. This review further underscores the advantages of nanobodies over conventional antibodies from a biosynthesis perspective, including their small size, stability, and solubility, which make them ideal candidates for economical antigen capture in diagnostics, therapeutics, and biosensing. We discuss the recent advancements in computational methods for nanobody modelling, epitope prediction, and affinity maturation, shedding light on their intricate antigen-binding mechanisms and conformational dynamics. Finally, we examine a direct example of how computational design strategies were implemented for improving a nanobody-based immunosensor, known as a Quenchbody. Through combining experimental findings and computational insights, this review elucidates the transformative impact of nanobodies in biotechnology and biomedical research, offering a roadmap for future advancements and applications in healthcare and diagnostics.

A novel inhalable nanobody targeting IL-4Rα for the treatment of asthma

BACKGROUND

Inhalable biologics represent a promising approach to improve the efficacy and safety of asthma treatment. Although several mAbs targeting IL-4 receptor α chain (IL-4Rα) have been approved or are undergoing clinical trials, the development of inhalable mAbs targeting IL-4Rα presents significant challenges.

OBJECTIVE

Capitalizing on the distinctive advantages of nanobodies (Nbs) in maintaining efficacy during storage and administration, we sought to develop a novel inhalable IL-4Rα Nb for effectively treating asthma.

METHODS

Three IL-4Rα immunized Nb libraries were used to generate specific and functional IL-4Rα Nbs. LQ036, a bivalent Nb comprising 2 HuNb103 units, was constructed with a high affinity and specificity for human IL-4Rα. The efficacy, pharmacokinetics, and safety of inhaled LQ036 were evaluated in B-hIL4/hIL4RA humanized mice.

RESULTS

LQ036 inhibited secreted embryonic alkaline phosphatase reporter activity, inhibited TF-1 cell proliferation, and suppressed phosphorylated signal transducer and activator of transduction 6 in T cells from patients with asthma. Crystal structure analysis revealed a binding region similar to dupilumab but with higher affinity, leading to better efficacy in blocking the signaling pathway. HuNb103 competed with IL-4 and IL-13 for IL-4Rα binding. Additionally, LQ036 significantly inhibited ovalbumin-specific IgE levels in serum, CCL17 levels in bronchoalveolar lavage fluid, bronchial mucous cell hyperplasia, and airway goblet cell hyperplasia in B-hIL4/hIL4RA humanized mice. Inhaled LQ036 exhibited favorable pharmacokinetics, safety, and tissue distribution, with higher concentrations observed in the lungs and bronchi.

CONCLUSIONS

These findings from preclinical studies establish the safety and efficacy of inhaled LQ036, underscoring its potential as a pioneering inhalable biologic therapy for asthma.

Comprehensive Overview of Broadly Neutralizing Antibodies against SARS-CoV-2 Variants

Currently, SARS-CoV-2 has evolved into various variants, including the numerous highly mutated Omicron sub-lineages, significantly increasing immune evasion ability. The development raises concerns about the possibly diminished effectiveness of available vaccines and antibody-based therapeutics. Here, we describe those representative categories of broadly neutralizing antibodies (bnAbs) that retain prominent effectiveness against emerging variants including Omicron sub-lineages. The molecular characteristics, epitope conservation, and resistance mechanisms of these antibodies are further detailed, aiming to offer suggestion or direction for the development of therapeutic antibodies, and facilitate the design of vaccines with broad-spectrum potential.

Single domain antibodies from camelids in the treatment of microbial infections

Infectious diseases continue to pose significant global health challenges. In addition to the enduring burdens of ailments like malaria and HIV, the emergence of nosocomial outbreaks driven by antibiotic-resistant pathogens underscores the ongoing threats. Furthermore, recent infectious disease crises, exemplified by the Ebola and SARS-CoV-2 outbreaks, have intensified the pursuit of more effective and efficient diagnostic and therapeutic solutions. Among the promising options, antibodies have garnered significant attention due to their favorable structural characteristics and versatile applications. Notably, nanobodies (Nbs), the smallest functional single-domain antibodies of heavy-chain only antibodies produced by camelids, exhibit remarkable capabilities in stable antigen binding. They offer unique advantages such as ease of expression and modification and enhanced stability, as well as improved hydrophilicity compared to conventional antibody fragments (antigen-binding fragments (Fab) or single-chain variable fragments (scFv)) that can aggregate due to their low solubility. Nanobodies directly target antigen epitopes or can be engineered into multivalent Nbs and Nb-fusion proteins, expanding their therapeutic potential. This review is dedicated to charting the progress in Nb research, particularly those derived from camelids, and highlighting their diverse applications in treating infectious diseases, spanning both human and animal contexts.

Next generation single-domain antibodies against respiratory zoonotic RNA viruses

The global impact of zoonotic viral outbreaks underscores the pressing need for innovative antiviral strategies, particularly against respiratory zoonotic RNA viruses. These viruses possess a high potential to trigger future epidemics and pandemics due to their high mutation rate, broad host range and efficient spread through airborne transmission. Recent pandemics caused by coronaviruses and influenza A viruses underscore the importance of developing targeted antiviral strategies. Single-domain antibodies (sdAbs), originating from camelids, also known as nanobodies or VHHs (Variable Heavy domain of Heavy chain antibodies), have emerged as promising tools to combat current and impending zoonotic viral threats. Their unique structure, coupled with attributes like robustness, compact size, and cost-effectiveness, positions them as strong alternatives to traditional monoclonal antibodies. This review describes the pivotal role of sdAbs in combating respiratory zoonotic viruses, with a primary focus on enhancing sdAb antiviral potency through optimization techniques and diverse administration strategies. We discuss both the promises and challenges within this dynamically growing field.

Progress in novel delivery technologies to improve efficacy of therapeutic antibodies

Monoclonal antibody-based therapeutics have achieved remarkable success in treating a wide range of human diseases. However, conventional systemic delivery methods have limitations in insufficient target tissue permeability, high costs, repeated administrations, etc. Novel technologies have been developed to address these limitations and further enhance antibody therapy. Local antibody delivery via respiratory tract, gastrointestinal tract, eye and blood-brain barrier have shown promising results in increasing local concentrations and overcoming barriers. Nucleic acid-encoded antibodies expressed from plasmid DNA, viral vectors or mRNA delivery platforms also offer advantages over recombinant proteins such as sustained expression, rapid onset, and lower costs. This review summarizes recent advances in antibody delivery methods and highlights innovative technologies that have potential to expand therapeutic applications of antibodies.

Engineered Multivalent Nanobodies Efficiently Neutralize SARS-CoV-2 Omicron Subvariants BA.1, BA.4/5, XBB.1 and BQ.1.1

Most available neutralizing antibodies are ineffective against highly mutated SARS-CoV-2 Omicron subvariants. Therefore, it is crucial to develop potent and broad-spectrum alternatives to effectively manage Omicron subvariants. Here, we constructed a high-diversity nanobody phage display library and identified nine nanobodies specific to the SARS-CoV-2 receptor-binding domain (RBD). Five of them exhibited cross-neutralization activity against the SARS-CoV-2 wild-type (WT) strain and the Omicron subvariants BA.1 and BA.4/5, and one nanobody demonstrated marked efficacy even against the Omicron subvariants BQ.1.1 and XBB.1. To enhance the therapeutic potential, we engineered a panel of multivalent nanobodies with increased neutralizing potency and breadth. The most potent multivalent nanobody, B13-B13-B13, cross-neutralized all tested pseudoviruses, with a geometric mean of the 50% inhibitory concentration (GM IC50) value of 20.83 ng/mL. An analysis of the mechanism underlying the enhancement of neutralization breadth by representative multivalent nanobodies demonstrated that the strategic engineering approach of combining two or three nanobodies into a multivalent molecule could improve the affinity between a single nanobody and spike, and could enhance tolerance toward escape mutations such as R346T and N460K. Our engineered multivalent nanobodies may be promising drug candidates for treating and preventing infection with Omicron subvariants and even future variants.

A SARS-CoV-2 Nanobody Displayed on the Surface of Human Ferritin with High Neutralization Activity

Purpose

COVID-19 is rampant throughout the world, which has caused great damage to human lives and seriously hindered the development of the global economy. Aiming at the treatment of SARS-CoV-2, in this study, we proposed a novel fenobody strategy based on ferritin (Fe) self-assembly technology.

Methods

The neutralizing nanobody H11-D4 of SARS-CoV-2 fused to the C-terminus of end-modified human ferritin was expressed in E. coli and silkworm baculovirus expression systems. A large number of nanoparticles were successfully self-assembled in silkworms, while relatively few nanoparticles can be observed in the treated products from E. coli by electron microscopy. Subsequently, the fenobody's expression level and neutralizing activity were then evaluated.

Results

The results showed that the IC50 of H11-D4 and fenobody Fe-H11-D4 expressed in E. coli were 171.1 nmol L-1 and 20.87 nmol L-1, respectively. However, the IC50 of Fe-HD11-D4 expressed in silkworms was 1.46 nmol L-1 showing better neutralization activity.

Conclusion

Therefore, fenobodies can be well self-assembled in silkworm baculovirus expression system, and ferritin self-assembly technology can effectively improve nanobody neutralization activity.

Approaches to the Prevention and Treatment of Respiratory Syncytial Virus Infection in Children: Rationale and Progress to Date

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in children, and is associated with long-term pulmonary sequelae for up to 30 years after infection. The mainstay of RSV management is supportive therapy such as supplemental oxygen. Palivizumab (Synagis™-AstraZeneca), a monoclonal antibody targeting the RSV F protein site II, has been licensed for the prevention of RSV in high-risk groups since 1998. There has been recent promising progress in preventative strategies that include vaccines and long-acting, high-potency monoclonal antibodies. Nirsevimab (Beyfortus™-AstraZeneca/Sanofi), a monoclonal antibody with an extended half-life, has recently been registered in the European Union and granted licensure by the US Food and Drug Administration. Furthermore, a pre-fusion sub-unit protein vaccine has been granted licensure for pregnant women, aimed at protecting their young infants, following established safety and efficacy in clinical trials (Abrysvo™-Pfizer). Also, multiple novel antiviral therapeutic options are in early phase clinical trials. The next few years have the potential to change the landscape of LRTI through improvements in the prevention and management of RSV LRTI. Here, we discuss these new approaches, current research, and clinical trials in novel therapeutics, monoclonal antibodies, and vaccines against RSV infection in infants and children.

A nanobody inhibiting porcine reproductive and respiratory syndrome virus replication via blocking self-interaction of viral nucleocapsid protein

Porcine reproductive and respiratory syndrome (PRRS) is a serious global pig industry disease. Understanding the mechanism of viral replication and developing efficient antiviral strategies are necessary for combating with PRRS virus (PRRSV) infection. Recently, nanobody is considered to be a promising antiviral drug, especially for respiratory viruses. The present study evaluated two nanobodies against PRRSV nucleocapsid (N) protein (PRRSV-N-Nb1 and -Nb2) for their anti-PRRSV activity in vitro and in vivo. The results showed that intracellularly expressed PRRSV-N-Nb1 significantly inhibited PRRSV-2 replication in MARC-145 cells (approximately 100%). Then, the PRRSV-N-Nb1 fused with porcine IgG Fc (Nb1-pFc) as a delivering tag was produced and used to determine its effect on PRRSV-2 replication in porcine alveolar macrophages (PAMs) and pigs. The inhibition rate of Nb1-pFc against PRRSV-2 in PAMs could reach >90%, and it can also inhibit viral replication in vivo. Epitope mapping showed that the motif Serine 105 (S105) in PRRSV-2 N protein was the key amino acid binding to PRRSV-N-Nb1, which is also pivotal for the self-interaction of N protein via binding to Arginine 97. Moreover, viral particles were not successfully rescued when the S105 motif was mutated to Alanine (S105A). Attachment, entry, genome replication, release, docking model analysis, and blocking enzyme-linked immunosorbent assay (ELISA) indicated that the binding of PRRSV-N-Nb1 to N protein could block its self-binding, which prevents the viral replication of PRRSV. PRRSV-N-Nb1 may be a promising drug to counter PRRSV-2 infection. We also provided some new insights into the molecular basis of PRRSV N protein self-binding and assembly of viral particles.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) causes serious economic losses to the swine industry worldwide, and there are no highly effective strategies for prevention. Nanobodies are considered a promising novel approach for treating diseases because of their ease of production and low costing. Here, we showed that PRRSV-N-Nb1 against PRRSV-N protein significantly inhibited PRRSV-2 replication in vitro and in vivo. Furthermore, we demonstrated that the motif Serine 105 (S105) in PRRSV-N protein was the key amino acid to interact with PRRSV-N-Nb1 and bond to its motif R97, which is important for the self-binding of N protein. The PRRSV-N-Nb1 could block the self-interaction of N protein following viral assembly. These findings not only provide insights into the molecular basis of PRRSV N protein self-binding as a key factor for viral replication for the first time but also highlight a novel target for the development of anti-PRRSV replication drugs.

A potent neutralizing nanobody targeting a unique epitope on the receptor-binding domain of SARS-CoV-2 spike protein

SARS-CoV-2 and its variants continue to threaten public health. Nanobodies that block the attachment of the RBD to host cell angiotensin-converting enzyme 2 (ACE2) represent promising drug candidates. In this study, we reported the identification and structural biological characterization of a nanobody from a RBD-immunized alpaca. The nanobody, termed as 2S-1-19, shows outstanding neutralizing activity against both pseudotyped and authentic SARS-CoV-2 viruses. The crystal structure of 2S-1-19 bound to SARS-CoV-2 RBD reveals an epitope that overlaps with the binding site for ACE2. We also showed that 2S-1-19 reserves promising, though compromised, neutralizing activity against the Delta variant and that the trivalent form of 2S-1-19 remarkably increases its neutralizing capacity. Despite this, neither the monomeric or trimeric 2S-1-19 could neutralize the Omicron BA.1.1 variant, possibility due to the E484A and Q493K mutations found within this virus variant. These data provide insights into immune evasion caused by SARS-CoV-2 variants.

Nanobodies to multiple spike variants and inhalation of nanobody-containing aerosols neutralize SARS-CoV-2 in cell culture and hamsters

The ongoing threat of COVID-19 has highlighted the need for effective prophylaxis and convenient therapies, especially for outpatient settings. We have previously developed highly potent single-domain (VHH) antibodies, also known as nanobodies, that target the Receptor Binding Domain (RBD) of the SARS-CoV-2 Spike protein and neutralize the Wuhan strain of the virus. In this study, we present a new generation of anti-RBD nanobodies with superior properties. The primary representative of this group, Re32D03, neutralizes Alpha to Delta as well as Omicron BA.2.75; other members neutralize, in addition, Omicron BA.1, BA.2, BA.4/5, and XBB.1. Crystal structures of RBD-nanobody complexes reveal how ACE2-binding is blocked and also explain the nanobodies' tolerance to immune escape mutations. Through the cryo-EM structure of the Ma16B06-BA.1 Spike complex, we demonstrated how a single nanobody molecule can neutralize a trimeric spike. We also describe a method for large-scale production of these nanobodies in Pichia pastoris, and for formulating them into aerosols. Exposing hamsters to these aerosols, before or even 24 h after infection with SARS-CoV-2, significantly reduced virus load, weight loss and pathogenicity. These results show the potential of aerosolized nanobodies for prophylaxis and therapy of coronavirus infections.

Next generation of multispecific antibody engineering

Multispecific antibodies recognize two or more epitopes located on the same or distinct targets. This added capability through protein design allows these man-made molecules to address unmet medical needs that are no longer possible with single targeting such as with monoclonal antibodies or cytokines alone. However, the approach to the development of these multispecific molecules has been met with numerous road bumps, which suggests that a new workflow for multispecific molecules is required. The investigation of the molecular basis that mediates the successful assembly of the building blocks into non-native quaternary structures will lead to the writing of a playbook for multispecifics. This is a must do if we are to design workflows that we can control and in turn predict success. Here, we reflect on the current state-of-the-art of therapeutic biologics and look at the building blocks, in terms of proteins, and tools that can be used to build the foundations of such a next-generation workflow.

Single-domain antibodies applied as antiviral immunotherapeutics

Viral infections have been the cause of high mortality rates throughout different periods in history. Over the last two decades, outbreaks caused by zoonotic diseases and transmitted by arboviruses have had a significant impact on human health. The emergence of viral infections in different parts of the world encourages the search for new inputs to fight pathologies of viral origin. Antibodies represent the predominant class of new drugs developed in recent years and approved for the treatment of various human diseases, including cancer, autoimmune and infectious diseases. A promising group of antibodies are single-domain antibodies derived from camelid heavy chain immunoglobulins, or VHHs, are biomolecules with nanometric dimensions and unique pharmaceutical and biophysical properties that can be used in the diagnosis and immunotherapy of viral infections. For viral neutralization to occur, VHHs can act in different stages of the viral cycle, including the actual inhibition of infection, to hindering viral replication or assembly. This review article addresses advances involving the use of VHHs in therapeutic propositions aimed to battle different viruses that affect human health.

Revolutionizing antiviral therapy with nanobodies: Generation and prospects

As the world continues to grapple with infectious diseases, scientists are constantly searching for effective ways to combat these deadly pathogens. One promising avenue of research is the use of nanobodies as neutralization agents. These small proteins, derived from camelid antibodies, have several unique advantages over traditional antibodies, including their small size. Nanobodies are much smaller than conventional antibodies, typically weighing in at around 15 kDa compared to the 150 kDa of a typical human antibody. This small size allows them to penetrate into tight spaces that larger molecules cannot reach, such as the crevices on the surface of viruses or bacteria. This makes them highly effective at neutralizing viruses by binding to and blocking their key functional sites. In this mini-review we discuss the construction approaches of nanobodies, and some methods to increase the half-life of nanobodies. Moreover, we discuss Nanobodies and their therapeutic potential for infectious agents.

Theoretical charge plots as a tool for targeted and accelerated ion exchange chromatography method development of NANOBODYⓇ molecules

NANOBODYⓇ molecules are an innovative class of biotherapeutics based on heavy chain only VHH immunoglobulins. Much like canonical antibodies, they are prone to the formation of charge variants and other post-translational modifications, which can potentially impact their critical quality attributes. Therefore, establishing high-resolution product-specific methods, such as IEX chromatography, is essential for evaluating the purity of these molecules. However, due to the lower surface charge of NANOBODYⓇ molecules, their charge-based elution behavior can differ considerably from that of classical antibodies, resulting in a more extensive method development set-up for these smaller molecules. Using an initial pH screening gradient based on theoretical protein charge plots, we investigated the IEX retention behavior of eight NANOBODYⓇ molecules with a wide range of pI values (pI 5.0 to 10.0). Our findings reveal that the charge-based chromatographic behavior of NANOBODYⓇ molecules cannot be solely attributed to the isoelectric point (pI) of the protein. Rather, a molecule-specific charge threshold was identified as a critical parameter for NANOBODYⓇ molecule retention. Furthermore, the protein charge plot also showed that NANOBODYⓇ molecule elution can be characterized by a charge plateau where the net charge of the protein remains constant over a certain pH range (∼ pH 5.5 to pH 8.0), further challenging the paradigm that elution pH and pI are fixed values. The application of this theoretical approach using protein charge plots to define NANOBODYⓇ molecule charge threshold and charge plateau parameters, can reduce overall IEX method development turnaround time by at least 2-fold.

A nanobody recognizes a unique conserved epitope and potently neutralizes SARS-CoV-2 omicron variants

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) Omicron variant sub-lineages spread rapidly worldwide, mostly due to their immune-evasive properties. This has put a significant part of the population at risk for severe disease and underscores the need for effective anti-SARS-CoV-2 agents against emergent strains in vulnerable patients. Camelid nanobodies are attractive therapeutic candidates due to their high stability, ease of large-scale production, and potential for delivery via inhalation. Here, we characterize the receptor binding domain (RBD)-specific nanobody W25 and show superior neutralization activity toward Omicron sub-lineages in comparison to all other SARS-CoV2 variants. Structure analysis of W25 in complex with the SARS-CoV2 spike glycoprotein shows that W25 engages an RBD epitope not covered by any of the antibodies previously approved for emergency use. In vivo evaluation of W25 prophylactic and therapeutic treatments across multiple SARS-CoV-2 variant infection models, together with W25 biodistribution analysis in mice, demonstrates favorable pre-clinical properties. Together, these data endorse W25 for further clinical development.

Barriers for orally inhaled therapeutic antibodies

INTRODUCTION

Respiratory diseases represent a worldwide health issue. The recent Sars-CoV-2 pandemic, the burden of lung cancer, and inflammatory respiratory diseases urged the development of innovative therapeutic solutions. In this context, therapeutic antibodies (Abs) offer a tremendous opportunity to benefit patients with respiratory diseases. Delivering Ab through the airways has been demonstrated to be relevant to improve their therapeutic index. However, few inhaled Abs are on the market.

AREAS COVERED

This review describes the different barriers that may alter the fate of inhaled therapeutic Abs in the lungs at steady state. It addresses both physical and biological barriers and discusses the importance of taking into consideration the pathological changes occurring during respiratory disease, which may reinforce these barriers.

EXPERT OPINION

The pulmonary route remains rare for delivering therapeutic Abs, with few approved inhaled molecules, despite promising evidence. Efforts must focus on the intertwined barriers associated with lung diseases to develop appropriate Ab-formulation-device combo, ensuring optimal Ab deposition in the respiratory tract. Finally, randomized controlled clinical trials should be carried out to establish inhaled Ab therapy as prominent against respiratory diseases.

Localized delivery of nanomedicine and antibodies for combating COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been a major health burden in the world. So far, many strategies have been investigated to control the spread of COVID-19, including social distancing, disinfection protocols, vaccines, and antiviral treatments. Despite the significant achievement, due to the constantly emerging new variants, COVID-19 is still a great challenge to the global healthcare system. It is an urgent demand for the development of new therapeutics and technologies for containing the wild spread of SARS-CoV-2. Inhaled administration is useful for the treatment of lung and respiratory diseases, and enables the drugs to reach the site of action directly with benefits of decreased dose, improved safety, and enhanced patient compliance. Nanotechnology has been extensively applied in the prevention and treatment of COVID-19. In this review, the inhaled nanomedicines and antibodies, as well as intranasal nanodrugs, for the prevention and treatment of COVID-19 are summarized.

An evolving perspective on novel modified release drug delivery systems for inhalational therapy

INTRODUCTION

Drugs delivered via the lungs are predominantly used to treat various respiratory disorders, including asthma, chronic obstructive pulmonary diseases, respiratory tract infections and lung cancers, and pulmonary vascular diseases such as pulmonary hypertension. To treat respiratory diseases, targeted, modified or controlled release inhalation formulations are desirable for improved patient compliance and superior therapeutic outcome.

AREAS COVERED

This review summarizes the important factors that have an impact on the inhalable modified release formulation approaches with a focus toward various formulation strategies, including dissolution rate-controlled systems, drug complexes, site-specific delivery, drug-polymer conjugates, and drug-polymer matrix systems, lipid matrix particles, nanosystems, and formulations that can bypass clearance via mucociliary system and alveolar macrophages.

EXPERT OPINION

Inhaled modified release formulations can potentially reduce dosing frequency by extending drug's residence time in the lungs. However, inhalable modified or controlled release drug delivery systems remain unexplored and underdeveloped from the commercialization perspective. This review paper addresses the current state-of-the-art of inhaled controlled release formulations, elaborates on the avenues for developing newer technologies for formulating various drugs with tailored release profiles after inhalational delivery and explains the challenges associated with translational feasibility of modified release inhalable formulations.

A Competitive Panning Method Reveals an Anti-SARS-CoV-2 Nanobody Specific for an RBD-ACE2 Binding Site

Most neutralizing antibodies neutralize the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by directly blocking the interactions between the spike glycoprotein receptor-binding domain (RBD) and its receptor, human angiotensin-converting enzyme 2 (ACE2). Here, we report a novel nanobody (Nb) identified by an RBD-ACE2 competitive panning method that could specifically bind to the RBD of SARS-CoV-2 with a high affinity (EC₅₀ = 0.03 nM) and successfully block the binding between the RBD and ACE2 recombinant protein. A structural simulation of the RBD-VHH complex also supports a mechanism of the Nb to block the interaction between the RBD and ACE2. A pseudovirus assay of the Nb showed it could neutralize the WT pseudovirus with high potency (IC₅₀ = 0.026 μg/mL). Furthermore, we measured its binding to phages displaying RBDs of different SARS-CoV-2 variants and found that it could bind to recombinant phages displaying the RBD of beta and delta variants. This study also provides a method of phage library competitive panning, which could be useful for directly screening high-affinity antibodies targeting important functional regions.

Applications of nanobodies in the prevention, detection, and treatment of the evolving SARS-CoV-2

Global health and economy are deeply influenced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its newly emerging variants. Nanobodies with nanometer-scale size are promising for the detection and treatment of SARS-CoV-2 and its variants because they are superior to conventional antibodies in terms of cryptic epitope accessibility, tissue penetration, cost, formatting adaptability, and especially protein stability, which enables their aerosolized specific delivery to lung tissues. This review summarizes the progress in the prevention, detection, and treatment of SARS-CoV-2 using nanobodies, as well as strategies to combat the evolving SARS-CoV-2 variants. Generally, highly efficient generation of potent broad-spectrum nanobodies targeting conserved epitopes or further construction of multivalent formats targeting non-overlapping epitopes can promote neutralizing activity against SARS-CoV-2 variants and suppress immune escape.

Inhalable neutralizing antibodies - promising approach to combating respiratory viral infections

Monoclonal antibodies represent an exciting class of therapeutics against respiratory viral infections. Notwithstanding their specificity and affinity, the conventional parenteral administration is suboptimal in delivering antibodies for neutralizing activity in the airways due to the poor distribution of macromolecules to the respiratory tract. Inhaled therapy is a promising approach to overcome this hurdle in a noninvasive manner, while advances in antibody engineering have led to the development of unique antibody formats which exhibit properties desirable for inhalation. In this Opinion, we examine the major challenges surrounding the development of inhaled antibodies, identify knowledge gaps that need to be addressed and provide strategies from a drug delivery perspective to enhance the efficacy and safety of neutralizing antibodies against respiratory viral infections.

Expanding and improving nanobody repertoires using a yeast display method: Targeting SARS-CoV-2

COVID-19, caused by the coronavirus SARS-CoV-2, represents a serious worldwide health issue, with continually emerging new variants challenging current therapeutics. One promising alternate therapeutic avenue is represented by nanobodies, small single-chain antibodies derived from camelids with numerous advantageous properties and the potential to neutralize the virus. For identification and characterization of a broad spectrum of anti-SARS-CoV-2 Spike nanobodies, we further optimized a yeast display method, leveraging a previously published mass spectrometry-based method, using B-cell complementary DNA from the same immunized animals as a source of V_HH sequences. Yeast display captured many of the sequences identified by the previous approach, as well as many additional sequences that proved to encode a large new repertoire of nanobodies with high affinities and neutralization activities against different SARS-CoV-2 variants. We evaluated DNA shuffling applied to the three complementarity-determining regions of antiviral nanobodies. The results suggested a surprising degree of modularity to complementarity-determining region function. Importantly, the yeast display approach applied to nanobody libraries from immunized animals allows parallel interrogation of a vast number of nanobodies. For example, we employed a modified yeast display to carry out massively parallel epitope binning. The current yeast display approach proved comparable in efficiency and specificity to the mass spectrometry-based approach, while requiring none of the infrastructure and expertise required for that approach, making these highly complementary approaches that together appear to comprehensively explore the paratope space. The larger repertoires produced maximize the likelihood of discovering broadly specific reagents and those that powerfully synergize in mixtures.

A bovine antibody possessing an ultralong complementarity-determining region CDRH3 targets a highly conserved epitope in sarbecovirus spike proteins

Broadly neutralizing antibodies have huge potential as novel antiviral therapeutics due to their ability to recognize highly conserved epitopes that are seldom mutated in viral variants. A subset of bovine antibodies possess an ultralong complementarity-determining region (CDR)H3 that is highly adept at recognizing such conserved epitopes, but their reactivity against Sarbecovirus Spike proteins has not been explored previously. Here, we use a SARS-naïve library to isolate a broadly reactive bovine CDRH3 that binds the receptor-binding domain of SARS-CoV, SARS-CoV-2, and all SARS-CoV-2 variants. We show further that it neutralizes viruses pseudo-typed with SARS-CoV Spike, but this is not by competition with angiotensin-converting enzyme 2 (ACE2) binding. Instead, using differential hydrogen-deuterium exchange mass spectrometry, we demonstrate that it recognizes the major site of vulnerability of Sarbecoviruses. This glycan-shielded cryptic epitope becomes available only transiently via interdomain movements of the Spike protein such that antibody binding triggers destruction of the prefusion complex. This proof of principle study demonstrates the power of in vitro expressed bovine antibodies with ultralong CDRH3s for the isolation of novel, broadly reactive tools to combat emerging pathogens and to identify key epitopes for vaccine development.

Single domain antibodies derived from ancient animals as broadly neutralizing agents for SARS-CoV-2 and other coronaviruses

With severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an emergent human virus since December 2019, the world population is susceptible to coronavirus disease 2019 (COVID-19). SARS-CoV-2 has higher transmissibility than the previous coronaviruses, associated by the ribonucleic acid (RNA) virus nature with high mutation rate, caused SARS-CoV-2 variants to arise while circulating worldwide. Neutralizing antibodies are identified as immediate and direct-acting therapeutic against COVID-19. Single-domain antibodies (sdAbs), as small biomolecules with non-complex structure and intrinsic stability, can acquire antigen-binding capabilities comparable to conventional antibodies, which serve as an attractive neutralizing solution. SARS-CoV-2 spike protein attaches to human angiotensin-converting enzyme 2 (ACE2) receptor on lung epithelial cells to initiate viral infection, serves as potential therapeutic target. sdAbs have shown broad neutralization towards SARS-CoV-2 with various mutations, effectively stop and prevent infection while efficiently block mutational escape. In addition, sdAbs can be developed into multivalent antibodies or inhaled biotherapeutics against COVID-19.

Inhaled IgG1 antibodies: The buffering system is an important driver of stability during mesh-nebulization

In the past decade, oral inhalation has been a thriving focus of research to administer antibody directly to the lungs as an aerosol, for local treatment of respiratory diseases. Formulation of inhaled antibodies is central for the stability of antibody, lung safety and to ensure inhaler performances. Surfactants have already been shown to prevent antibody degradation during aerosolization, but little is known about the impact of other components of liquid formulations on the structural stability of antibodies. Here, we report for the first time to the best of our knowledge, a significant effect of the buffering system on monoclonal antibodies stability, during mesh-nebulization. While the monoclonal antibody extensively aggregated in citrate buffer after nebulization and required high concentration of polysorbate 80 (PS80) to maintain protein integrity, acetate and histidine buffers resulted in a slight to moderate aggregation without PS80 and low concentration of PS80 was sufficient to stabilize antibody during mesh-nebulization.

From animal studies into clinical trials: the relevance of animal models to develop vaccines and therapies to reduce disease severity and prevent hRSV infection

INTRODUCTION

Human respiratory syncytial virus (hRSV) is an important cause of lower respiratory tract infections in the pediatric and the geriatric population worldwide. There is a substantial economic burden resulting from hRSV disease during winter. Although no vaccines have been approved for human use, prophylactic therapies are available for high-risk populations. Choosing the proper animal models to evaluate different vaccine prototypes or pharmacological treatments is essential for developing efficient therapies against hRSV.

AREAS COVERED

This article describes the relevance of using different animal models to evaluate the effect of antiviral drugs, pharmacological molecules, vaccine prototypes, and antibodies in the protection against hRSV. The animal models covered are rodents, mustelids, bovines, and nonhuman primates. Animals included were chosen based on the available literature and their role in the development of the drugs discussed in this manuscript.

EXPERT OPINION

Choosing the correct animal model is critical for exploring and testing treatments that could decrease the impact of hRSV in high-risk populations. Mice will continue to be the most used preclinical model to evaluate this. However, researchers must also explore the use of other models such as nonhuman primates, as they are more similar to humans, prior to escalating into clinical trials.

Camels' biological fluids contained nanobodies: promising avenue in cancer therapy

Cancer is a major health concern and accounts for one of the main causes of death worldwide. Innovative strategies are needed to aid in the diagnosis and treatment of different types of cancers. Recently, there has been an evolving interest in utilizing nanobodies of camel origin as therapeutic tools against cancer. Nanotechnology uses nanobodies an emerging attractive field that provides promises to researchers in advancing different scientific sectors including medicine and oncology. Nanobodies are characteristically small-sized biologics featured with the ability for deep tissue penetration and dissemination and harbour high stability at high pH and temperatures. The current review highlights the potential use of nanobodies that are naturally secreted in camels’ biological fluids, both milk and urine, in the development of nanotechnology-based therapy for treating different typesQuery of cancers and other diseases. Moreover, the role of nano proteomics in the invention of novel therapeutic agents specifically used for cancer intervention is also illustrated.

Advances in Nanomaterial-Based Platforms to Combat COVID-19: Diagnostics, Preventions, Therapeutics, and Vaccine Developments

The COVID-19 pandemic caused by the SARS-CoV-2, a ribonucleic acid (RNA) virus that emerged less than two years ago but has caused nearly 6.1 million deaths to date. Recently developed variants of the SARS-CoV-2 virus have been shown to be more potent and expanded at a faster rate. Until now, there is no specific and effective treatment for SARS-CoV-2 in terms of reliable and sustainable recovery. Precaution, prevention, and vaccinations are the only ways to keep the pandemic situation under control. Medical and scientific professionals are now focusing on the repurposing of previous technology and trying to develop more fruitful methodologies to detect the presence of viruses, treat the patients, precautionary items, and vaccine developments. Nanomedicine or nanobased platforms can play a crucial role in these fronts. Researchers are working on many effective approaches by nanosized particles to combat SARS-CoV-2. The role of a nanobased platform to combat SARS-CoV-2 is extremely diverse (i.e., mark to personal protective suit, rapid diagnostic tool to targeted treatment, and vaccine developments). Although there are many theoretical possibilities of a nanobased platform to combat SARS-CoV-2, until now there is an inadequate number of research targeting SARS-CoV-2 to explore such scenarios. This unique mini-review aims to compile and elaborate on the recent advances of nanobased approaches from prevention, diagnostics, treatment to vaccine developments against SARS-CoV-2, and associated challenges.

Advances in the design of new types of inhaled medicines

Inhalation of small molecule drugs has proven very efficacious for the treatment of respiratory diseases due to enhanced efficacy and a favourable therapeutic index compared with other dosing routes. It enables targeted delivery to the lung with rapid onset of therapeutic action, low systemic drug exposure, and thereby reduced systemic side effects. An increasing number of pharmaceutical companies and biotechs are investing in new modalities-for this review defined as therapeutic molecules with a molecular weight >800Da and therefore beyond usual inhaled small molecule drug-like space. However, our experience with inhaled administration of PROTACs, peptides, oligonucleotides (antisense oligonucleotides, siRNAs, miRs and antagomirs), diverse protein scaffolds, antibodies and antibody fragments is still limited. Investigating the retention and metabolism of these types of molecules in lung tissue and fluid will contribute to understanding which are best suited for inhalation. Nonetheless, the first such therapeutic molecules have already reached the clinic. This review will provide information on the physiology of healthy and diseased lungs and their capacity for drug metabolism. It will outline the stability, aggregation and immunogenicity aspects of new modalities, as well as recap on formulation and delivery aspects. It concludes by summarising clinical trial outcomes with inhaled new modalities based on information available at the end of 2021.

Nanobodies: from structure to applications in non-injectable and bispecific biotherapeutic development

The increasing demand for convenient, miniaturized and multifunctional antibodies necessitates the development of novel antigen-recognition molecules for biological and medical studies. Nanobodies, the functional variable regions of camelid heavy-chain-only antibodies, as a new tool, complement the conventional antibodies and are in the stage of rapid development. The outstanding advantages of nanobodies include a stable structure, easy production, excellent water solubility, high affinity toward antigens and low immunogenicity. With promising application potential, nanobodies are now increasingly applied to various studies, including protein structure analysis, microscopic imaging, medical diagnosis, and drug development. The approval of the first nanobody drug Caplacizumab by the FDA disclosed the therapeutic potential of nanobodies. The outbreak of COVID-19 accelerated the development of nanobody drugs in non-injectable and bispecific biotherapeutic applications. Herein, we reviewed recent studies on the nanobody structure, screening and their applications in protein structure analysis and nanobody drugs, especially on non-injectable nanobody and bispecific nanobody development.

Nanobodies Protecting From Lethal SARS-CoV-2 Infection Target Receptor Binding Epitopes Preserved in Virus Variants Other Than Omicron

The emergence of SARS-CoV-2 variants that escape from immune neutralization are challenging vaccines and antibodies developed to stop the COVID-19 pandemic. Thus, it is important to establish therapeutics directed toward multiple or specific SARS-CoV-2 variants. The envelope spike (S) glycoprotein of SARS-CoV-2 is the key target of neutralizing antibodies (Abs). We selected a panel of nine nanobodies (Nbs) from dromedary camels immunized with the receptor-binding domain (RBD) of the S, and engineered Nb fusions as humanized heavy chain Abs (hcAbs). Nbs and derived hcAbs bound with subnanomolar or picomolar affinities to the S and its RBD, and S-binding cross-competition clustered them in two different groups. Most of the hcAbs hindered RBD binding to its human ACE2 (hACE2) receptor, blocked cell entry of viruses pseudotyped with the S protein and neutralized SARS-CoV-2 infection in cell cultures. Four potent neutralizing hcAbs prevented the progression to lethal SARS-CoV-2 infection in hACE2-transgenic mice, demonstrating their therapeutic potential. Cryo-electron microscopy identified Nb binding epitopes in and out the receptor binding motif (RBM), and showed different ways to prevent virus binding to its cell entry receptor. The Nb binding modes were consistent with its recognition of SARS-CoV-2 RBD variants; mono and bispecific hcAbs efficiently bound all variants of concern except omicron, which emphasized the immune escape capacity of this latest variant.

Dromedary camel nanobodies broadly neutralize SARS-CoV-2 variants

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike is a trimer of S1/S2 heterodimers with three receptor-binding domains (RBDs) at the S1 subunit for human angiotensin-converting enzyme 2 (hACE2). Due to their small size, nanobodies can recognize protein cavities that are not accessible to conventional antibodies. To isolate high-affinity nanobodies, large libraries with great diversity are highly desirable. Dromedary camels (Camelus dromedarius) are natural reservoirs of coronaviruses like Middle East respiratory syndrome CoV (MERS-CoV) that are transmitted to humans. Here, we built large dromedary camel VHH phage libraries to isolate nanobodies that broadly neutralize SARS-CoV-2 variants. We isolated two VHH nanobodies, NCI-CoV-7A3 (7A3) and NCI-CoV-8A2 (8A2), which have a high affinity for the RBD via targeting nonoverlapping epitopes and show broad neutralization activity against SARS-CoV-2 and its emerging variants of concern. Cryoelectron microscopy (cryo-EM) complex structures revealed that 8A2 binds the RBD in its up mode with a long CDR3 loop directly involved in the ACE2 binding residues and that 7A3 targets a deeply buried region that uniquely extends from the S1 subunit to the apex of the S2 subunit regardless of the conformational state of the RBD. At a dose of ≥5 mg/kg, 7A3 efficiently protected transgenic mice expressing hACE2 from the lethal challenge of variants B.1.351 or B.1.617.2, suggesting its therapeutic use against COVID-19 variants. The dromedary camel VHH phage libraries could be helpful as a unique platform ready for quickly isolating potent nanobodies against future emerging viruses.

Biparatopic sybodies neutralize SARS-CoV-2 variants of concern and mitigate drug resistance

The ongoing COVID‐19 pandemic represents an unprecedented global health crisis. Here, we report the identification of a synthetic nanobody (sybody) pair, Sb#15 and Sb#68, that can bind simultaneously to the SARS‐CoV‐2 spike RBD and efficiently neutralize pseudotyped and live viruses by interfering with ACE2 interaction. Cryo‐EM confirms that Sb#15 and Sb#68 engage two spatially discrete epitopes, influencing rational design of bispecific and tri‐bispecific fusion constructs that exhibit up to 100‐ and 1,000‐fold increase in neutralization potency, respectively. Cryo‐EM of the sybody‐spike complex additionally reveals a novel up‐out RBD conformation. While resistant viruses emerge rapidly in the presence of single binders, no escape variants are observed in the presence of the bispecific sybody. The multivalent bispecific constructs further increase the neutralization potency against globally circulating SARS‐CoV‐2 variants of concern. Our study illustrates the power of multivalency and biparatopic nanobody fusions for the potential development of therapeutic strategies that mitigate the emergence of new SARS‐CoV‐2 escape mutants.

Nanobodies: From Serendipitous Discovery of Heavy Chain-Only Antibodies in Camelids to a Wide Range of Useful Applications

The presence of unique heavy chain-only antibodies (HCAbs) in camelids was discovered at Vrije Universiteit Brussel (VUB, Brussels, Belgium) at a time when many researchers were exploring the cloning and expression of smaller antigen-binding fragments (Fv and Fab) from hybridoma-derived antibodies. The potential importance of this discovery was anticipated, and efforts were immediately undertaken to understand the emergence and ontogeny of these HCAbs as well as to investigate the applications of the single-domain antigen-binding variable domains of HCAbs (nanobodies). Nanobodies were demonstrated to possess multiple biochemical and biophysical advantages over other antigen-binding antibody fragments and alternative scaffolds. Today, nanobodies have a significant and growing impact on research, biotechnology, and medicine.

Bovine-derived antibodies and camelid-derived nanobodies as biotherapeutic weapons against SARS-CoV-2 and its variants: A review article

The Coronavirus Disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected 305 million individuals worldwide and killed about 5.5 million people as of January 10, 2022. SARS-CoV-2 is the third major outbreak caused by a new coronavirus in the previous two decades, following SARS-CoV and MERS-CoV. Even though vaccination against SARS-CoV-2 is considered a critical strategy for preventing virus spread in the population and limiting COVID-19 clinical manifestations, new therapeutic drugs, and management strategies are urgently needed, particularly in light of the growing number of SARS-CoV-2 variants (such as Delta and Omicron variants). However, the use of conventional antibodies has faced many challenges, such as viral escape mutants, increased instability, weak binding, large sizes, the need for large amounts of plasma, and high-cost manufacturing. Furthermore, the emergence of new SARS-CoV-2 variants in the human population and recurrent coronavirus spillovers highlight the need for broadly neutralizing antibodies that are not affected by an antigenic drift that could limit future zoonotic infection. Bovine-derived antibodies and camelid-derived nanobodies are more potent and protective than conventional human antibodies, thanks to their inbuilt characteristics, and can be produced in large quantities. In addition, it was reported that these biotherapeutics are effective against a broad spectrum of epitopes, reducing the opportunity of viral pathogens to develop mutational escape. In this review, we focus on the potential benefits behind our rationale for using bovine-derived antibodies and camelid-derived nanobodies in countering SARS-CoV-2 and its emerging variants and mutants.

The role of single-domain antibodies (or nanobodies) in SARS-CoV-2 neutralization

The severe acute respiratory syndrome (SARS-CoV-2), a newly emerging of coronavirus, continues to infect humans in the absence of a viable treatment. Neutralizing antibodies that disrupt the interaction of RBD and ACE2 has been under the spotlight as a way of developing the COVID-19 treatment. Some animals, such as llamas, manufacture heavy-chain antibodies that have a single variable domain (VHH) instead of two variable domains (VH/VL) as opposed to typical antibodies. Nanobodies are antigen-specific, single-domain, changeable segments of camelid heavy chain-only antibodies that are recombinantly produced. These types of antibodies exhibit a wide range of strong physical and chemical properties, like high solubility, and stability. The VHH's high-affinity attachment to the receptor-binding domain (RBD) allowed the neutralization of SARS-CoV-2. To tackle COVID-19, some nanobodies are being developed against SARS-CoV-2, some of which have been recently included in clinical trials. Nanobody therapy may be useful in managing the COVID-19 pandemic as a potent and low-cost treatment. This paper describes the application of nanobodies as a new class of recombinant antibodies in COVID-19 treatment.

Nebulized delivery of a broadly neutralizing SARS-CoV-2 RBD-specific nanobody prevents clinical, virological, and pathological disease in a Syrian hamster model of COVID-19

There remains an unmet need for globally deployable, low-cost therapeutics for the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Previously, we reported on the isolation and in vitro characterization of a potent single-domain nanobody, NIH-CoVnb-112, specific for the receptor-binding domain (RBD) of SARS-CoV-2. Here, we report on the molecular basis for the observed broad in vitro neutralization capability of NIH-CoVnb-112 against variant SARS-CoV-2 pseudoviruses. The structure of NIH-CoVnb-112 bound to SARS-CoV-2 RBD reveals a large contact surface area overlapping the angiotensin converting enzyme 2 (ACE2) binding site, which is largely unencumbered by the common RBD mutations. In an in vivo pilot study, we demonstrate effective reductions in weight loss, viral burden, and lung pathology in a Syrian hamster model of COVID-19 following nebulized delivery of NIH-CoVnb-112. These findings support the further development of NIH-CoVnb-112 as a potential adjunct preventative therapeutic for the treatment of SARS-CoV-2 infection.Abbreviations: ACE2 - angiotensin converting enzyme 2BSA - buried surface areaCDR - complementary determining regionRBD - receptor binding domainRBM - receptor-binding motifSARS-CoV-2 - severe acute respiratory syndrome coronavirus 2.

Highly synergistic combinations of nanobodies that target SARS-CoV-2 and are resistant to escape

The emergence of SARS-CoV-2 variants threatens current vaccines and therapeutic antibodies and urgently demands powerful new therapeutics that can resist viral escape. We therefore generated a large nanobody repertoire to saturate the distinct and highly conserved available epitope space of SARS-CoV-2 spike, including the S1 receptor binding domain, N-terminal domain, and the S2 subunit, to identify new nanobody binding sites that may reflect novel mechanisms of viral neutralization. Structural mapping and functional assays show that indeed these highly stable monovalent nanobodies potently inhibit SARS-CoV-2 infection, display numerous neutralization mechanisms, are effective against emerging variants of concern, and are resistant to mutational escape. Rational combinations of these nanobodies that bind to distinct sites within and between spike subunits exhibit extraordinary synergy and suggest multiple tailored therapeutic and prophylactic strategies.

Animal models of SARS-CoV-2 and COVID-19 for the development of prophylactic and therapeutic interventions

Infections of the Coronavirus SARS-CoV-2 continue to spread around the globe, causing Coronavirus Disease (COVID)-19. Infected people are at risk of developing acute interstitial pneumonia, which can result in lethal complications, particularly in patients with pre-existing co-morbidities. Novel prophylactic and therapeutic interventions are urgently needed to limit the infection-associated health risk for the population and to contain the pandemic. Animal models are indispensable to assessing the efficacy and safety of potential new antivirals, vaccines, and other innovative therapies, such as nucleic acid agonists of innate immune sensing receptors. In this review, we provide an overview of the commonly used animal models to study SARS-CoV-2 and COVID-19, including a summary of their susceptibility to infection, the spectrum of symptoms elicited, and the potential for drug development in each model. We hope that this review will help researchers to decide on the right model organism to quickly address their specific scientific questions.

Development of Neutralizing Multimeric Nanobody Constructs Directed against IL-13: From Immunization to Lead Optimization

IL-13 is a pleiotropic cytokine mainly secreted by Th2 cells. It reacts with many different types of cells involved in allergy, inflammation, and fibrosis, e.g., mastocytes, B cells, and fibroblasts. The role of IL-13 in conditions involving one or several of these phenotypes has therefore been extensively investigated. The inhibition of this cytokine in animal models for various pathologies yielded highly promising results. However, most human trials relying on anti-IL-13 conventional mAbs have failed to achieve a significant improvement of the envisaged disorders. Where some studies might have suffered from several weaknesses, the strategies themselves, such as targeting only IL-13 using conventional mAbs or employing a systemic administration, could be questioned. Nanobodies are recombinant Ag-binding fragments derived from the variable part of H chain-only Abs occurring in Camelidae. Thanks to their single-domain structure, small size (≈15 kDa), good stability, and solubility, they can be engineered into multispecific constructs for combined therapies or for use in new strategies such as formulations for local administration, e.g., pulmonary administration. In this study, we describe the generation of 38 nanobodies that can be subdivided into five CDR3 families. Nine nanobodies were found to have a good affinity profile (K_D = 1-200 nM), but none were able to strongly inhibit IL-13 biological activity in vitro (IC₅₀ > 50 µM: HEK-Blue IL-13/IL-4 cells). Multimeric constructs were therefore designed from these inhibitors and resulted in an up to 36-fold improvement in affinity and up to 300-fold enhancement of the biological activity while conserving a high specificity toward IL-13.

Nebulized delivery of a broadly neutralizing SARS-CoV-2 RBD-specific nanobody prevents clinical, virological and pathological disease in a Syrian hamster model of COVID-19

There remains an unmet need for globally deployable, low-cost therapeutics for the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Previously, we reported on the isolation and in vitro characterization of a potent single-domain nanobody, NIH-CoVnb-112, specific for the receptor binding domain (RBD) of SARS-CoV-2. Here, we report on the molecular basis for the observed broad in vitro neutralization capability of NIH-CoVnb-112 against variant SARS-CoV-2 pseudoviruses, including the currently dominant Delta variant. The structure of NIH-CoVnb-112 bound to SARS-CoV-2 RBD reveals a large contact surface area overlapping the angiotensin converting enzyme 2 (ACE2) binding site, which is largely unencumbered by the common RBD mutations. In an in vivo pilot study, we demonstrate effective reductions in weight loss, viral burden, and lung pathology in a Syrian hamster model of COVID-19 following nebulized delivery of NIH-CoVnb-112. These findings support the further development of NIH-CoVnb-112 as a potential adjunct preventative therapeutic for the treatment of SARS-CoV-2 infection.

Prediction of pharmacokinetic parameters of inhaled indacaterol formulation in healthy volunteers using physiologically-based pharmacokinetic (PBPK) model

BACKGROUND

Inhaled formulations are the first choices for treating asthma and chronic obstructive pulmonary disease (COPD), attracting the increasing investment and development in the pharmaceutical industry. Both the equivalence of local and systemic exposures need to be considered when assessing the equivalence of generic inhaled drugs, which has become a dilemma in the development of generic inhaled drugs. There is an urgent need for reliable methods such as physiologically-based pharmacokinetic (PBPK) model to assist in the development of inhaled drugs.

METHOD

To test the strategy that in silico simulation is an effective tool in developing inhaled products and further assessing their clinically feasibility, a long-acting beta2-adrenergic agonists indacaterol, which was referred as the first-line therapy for patient with COPD, was selected as a tool drug. The PBPK model was established and the predicted plasma concentration curve was obtained by inputting the physicochemical properties of indacaterol and adjusting model parameters. The accuracy of simulation was verified by an alignment with the actual data. The main factor affecting PK in vivo was investigated by parameter sensitivity analysis. The biological equivalent size of indacaterol was investigated by virtual bioequivalence analysis.

RESULTS

The models of indacaterol after intravenous and oral administration were established and confirmed, and used as a background for PBPK model of inhaled administration. All those models showed favorable stability and applicability. Appropriate lung deposition was generated in the PBPK model, and the predicted plasma profile of indacaterol was consistent with the clinical actual observation values. Particle size is the most important factor affecting the PK of indacaterol in vivo. Furthermore, virtual bioequivalence simulation exhibited statistically comparable results between the particle size fluctuates in the range of 3.5-6.5 μm and baseline levels (D90 = 5 μm).

CONCLUSIONS

The PBPK model can simulate the pharmacokinetics and lung deposition of indacaterol, which will be a powerful tool to assist the development of inhaled drugs.

Structural Biology of Nanobodies against the Spike Protein of SARS-CoV-2

Nanobodies are 130 amino acid single-domain antibodies (V_HH) derived from the unique heavy-chain-only subclass of Camelid immunogloblins. Their small molecular size, facile expression, high affinity and stability have combined to make them unique targeting reagents with numerous applications in the biomedical sciences. The first nanobody agent has now entered the clinic as a treatment against a blood disorder. The spread of the SARS-CoV-2 virus has seen the global scientific endeavour work to accelerate the development of technologies to try to defeat a pandemic that has now killed over four million people. In a remarkably short period of time, multiple studies have reported nanobodies directed against the viral Spike protein. Several agents have been tested in culture and demonstrate potent neutralisation of the virus or pseudovirus. A few agents have completed animal trials with very encouraging results showing their potential for treating infection. Here, we discuss the structural features that guide the nanobody recognition of the receptor binding domain of the Spike protein of SARS-CoV-2.

Nanobodies as powerful pulmonary targeted biotherapeutics against SARS-CoV-2, pharmaceutical point of view

Background Since December 2019, the newly emerged SARS-CoV-2 virus continues to infect humans and many people died from severe Covid-19 during the last 2 years worldwide. Different approaches are being used for treatment of this infection and its consequences, but limited results have been achieved and new therapeutics are still needed. One of the most interesting biotherapeutics in this era are Nanobodies which have shown very promising results in recent researches. Scope of review Here, we have reviewed the potentials of Nanobodies in Covid-19 treatment. We have also discussed the properties of these biotherapeutics that make them very suitable for pulmonary drug delivery, which seems to be very important route of administration in this disease. Major conclusion Nanobodies with their special biological and biophysical characteristics and their resistance against harsh manufacturing condition, can be considered as promising, targeted biotherapeutics which can be administered by pulmonary delivery pharmaceutical systems against Covid-19. General significance Covid-19 has become a global problem during the last two years and with emerging mutant strains, prophylactic and therapeutic approaches are still highly needed. Nanobodies with their specific properties can be considered as valuable and promising candidates in Covid-19 therapy.