Single-domain antibodies as therapeutics for solid tumor treatment

Single-domain antibodies(sdAbs),initially identified in camelids or sharks and commonly referred to as nanobodies or VNARs,have emerged as a promising alternative to conventional therapeutic antibodies.These sdAbs have many superior physicochemical and pharmacological properties,including small size,good solubility and thermostability,easier accessible epitopes,and strong tissue penetration.However,the inherent challenges associated with the animal origin of sdAbs limit their clinical use.In recent years,various innovative humanization technologies,including complementarity-determining region(CDR)grafting or complete engineering of fully human sdAbs,have been developed to mitigate potential immunogenicity issues and enhance their compatibility.This review provides a comprehensive exploration of sdAbs,emphasizing their distinctive features and the progress in humanization methodologies.In addition,we provide an overview of the recent progress in developing drugs and therapeutic strategies based on sdAbs and their potential in solid tumor treatment,such as sdAbedrug conjugates,multispecific sdAbs,sdAb-based delivery systems,and sdAb-based cell therapy.

Fusion mechanism of 2019-nCoV and fusion inhibitors targeting HR1 domain in spike protein

Very recently,a novel coronavirus,2019-nCoV,emerged in Wuhan,China and then quickly spread worldwide,resulting in>17,388 confirmed cases and 361 deaths as of 3 February 2020,thus calling for the development of safe and effective therapeutics and prophylatics.1,2 Similar to severe acute respiratory syndrome(SARS)-CoV,2019-nCoV belongs to lineage B betacoronavirus,and it has the ability to utilize human angiotensin-converting enzyme 2(ACE2)as a receptor to infect human cells.

A novel coronavirus (2019-nCoV) causing pneumonia-associated respiratory syndrome

By the end of 2019,the World Health Organization(WHO)was informed about an outbreak of pneumonia of unknown etiology in Wuhan,China.Some patients were linked to a seafood market,suggesting animal-to-human transmission,but,soon,human-tohuman transmission was confirmed.The pathogen was promptly identified as a novel coronavirus belonging to lineage B betacoronaviruses that also include severe acute respiratory syndrome coronavirus(SARS-CoV),which caused a pandemic in China in 2002/2003,and bat SARS-like coronaviruses.

Human monoclonal antibodies as candidate therapeutics against emerging viruses

The emergence of new pathogens, such as severe acute respiratory syndrome coronavirus （SARS-CoV）, Middle East respiratory syndrome coronavirus （MERS-CoV）, and Ebola virus, poses serious challenges to global public health and highlights the urgent need for novel antiviral approaches. Monoclonal antibodies （mAbs） have been successfully used to treat various diseases, particularly cancer and immunological disorders. Antigen-specific mAbs have been isolated using several different approaches, including hybridoma, transgenic mice, phage display, yeast display, and single B-celi isolation. Consequently, an increasing number of mAbs, which exhibit high potency against emerging viruses in vitro and in animal models of infection, have been developed. In this paper, we summarize historical trends and recent developments in mAb discovery, compare the advantages and disadvantages of various approaches to mAb production, and discuss the potential use of such strategies for the development of antivirals against emerging diseases. We also review the application of recently developed human mAbs against SARS-CoV, MERS-CoV, and Ebola virus and discuss prospects for the development of mAbs as therapeutic agents against emerging viral diseases.

RBD-Fc-based COVID-19 vaccine candidate induces highly potent SARS-CoV-2 neutralizing antibody response

The pandemic of coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has posed serious threats to global health and economy,thus calling for the development of safe and effective vaccines.The receptorbinding domain(RBD)in the spike protein of SARS-CoV-2 is responsible for its binding to angiotensin-converting enzyme 2(ACE2)receptor.It contains multiple dominant neutralizing epitopes and serves as an important antigen for the development of COVID-19 vaccines.Here,we showed that immunization of mice with a candidate subunit vaccine consisting of SARS-CoV-2 RBD and Fc fragment of human IgG,as an immunopotentiator,elicited high titer of RBD-specific antibodies with robust neutralizing activity against both pseudotyped and live SARS-CoV-2 infections.The mouse antisera could also effectively neutralize infection by pseudotyped SARS-CoV-2 with several natural mutations in RBD and the IgG extracted from the mouse antisera could also show neutralization against pseudotyped SARS-CoV and SARS-related coronavirus(SARSr-CoV).Vaccination of human ACE2 transgenic mice with RBD-Fc could effectively protect mice from the SARS-CoV-2 challenge.These results suggest that SARS-CoV-2 RBD-Fc has good potential to be further developed as an effective and broad-spectrum vaccine to prevent infection of the current SARS-CoV-2 and its mutants,as well as future emerging SARSr-CoVs and re-emerging SARS-CoV.

Recent advances in developing small-molecule inhibitors against SARS-CoV-2

The COVID-19 pandemic caused by the novel SARS-CoV-2 virus has caused havoc across the entire world.Even though several COVID-19 vaccines are currently in distribution worldwide,with others in the pipeline,treatment modalities lag behind.Accordingly,researchers have been working hard to understand the nature of the virus,its mutant strains,and the pathogenesis of the disease in order to uncover possible drug targets and effective therapeutic agents.As the research continues,we now know the genome structure,epidemiological and clinical features,and pathogenic mechanism of SARS-CoV-2.Here,we summarized the potential therapeutic targets involved in the life cycle of the virus.On the basis of these targets,small-molecule prophylactic and therapeutic agents have been or are being developed for prevention and treatment of SARS-CoV-2 infection.

Antibody Cocktail Exhibits Broad Neutralization Activity Against SARS-CoV-2 and SARS-CoV-2 Variants

Severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)has precipitated multiple variants resistant to therapeutic antibodies.In this study,12 high-affinity antibodies were generated from convalescent donors in early outbreaks using immune antibody phage display libraries.Of them,two RBD-binding antibodies(F61 and H121)showed high-affinity neutralization against SARS-Co V-2,whereas three S2-target antibodies failed to neutralize SARS-Co V-2.Following structure analysis,F61 identified a linear epitope located in residues G446–S494,which overlapped with angiotensinconverting enzyme 2(ACE2)binding sites,while H121 recognized a conformational epitope located on the side face of RBD,outside from ACE2 binding domain.Hence the cocktail of the two antibodies achieved better performance of neutralization to SARS-Co V-2.Importantly,these two antibodies also showed efficient neutralizing activities to the variants including B.1.1.7 and B.1.351,and reacted with mutations of N501 Y,E484 K,and L452 R,indicated that it may also neutralize the recent India endemic strain B.1.617.The unchanged binding activity of F61 and H121 to RBD with multiple mutations revealed a broad neutralizing activity against variants,which mitigated the risk of viral escape.Our findings revealed the therapeutic basis of cocktail antibodies against constantly emerging SARS-Co V-2 variants and provided promising candidate antibodies to clinical treatment of COVID-19 patients infected with broad SARS-Co V-2 variants.

Receptor-binding domain-specific human neutralizing monoclonal antibodies against SARS-CoV and SARS-CoV-2

The outbreaks of severe acute respiratory syndrome(SARS)and Coronavirus Disease 2019(COVID-19)caused by SARS-CoV and SARS-CoV-2,respectively,have posed severe threats to global public health and the economy.Treatment and prevention of these viral diseases call for the research and development of human neutralizing monoclonal antibodies(NMAbs).Scientists have screened neutralizing antibodies using the virus receptor-binding domain(RBD)as an antigen,indicating that RBD contains multiple conformational neutralizing epitopes,which are the main structural domains for inducing neutralizing antibodies and T-cell immune responses.This review summarizes the structure and function of RBD and RBD-specific NMAbs against SARS-CoV and SARS-CoV-2 currently under development.

Establishment of Novel Monoclonal Fabs Specific for Epstein-Barr Virus Encoded Latent Membrane Protein 1

Dear Editor,Epstein-Barr virus(EBV,also termed human herpesvirus-4)was the first identified human tumor virus.Since its discovery in 1964,studies have shown that EBV infects over 90%of all people by the time they are adults(Williams and Crawford 2006).EBV infection can result in mucocutaneous and systemic diseases,ranging from selflimited illnesses to aggressive malignancies,including B cell Hodgkin lymphoma and nasopharyngeal carcinoma.In vitro,EBV transforms resting B cells into proliferating blast cells(Pope et al.1968).

The impact of receptor-binding domain natural mutations on antibody recognition of SARS-CoV-2

Dear Editor,The ongoing COVID-19 pandemic has resulted in over 25.0 million confirmed cases and over 840,000 deaths globally.As the third severe respiratory disease outbreak caused by the coronavirus,COVID-19 has led to much larger infected populations and coverage of geographic areas than SARS and MERS.Such high prevalence of infection has raised significant concerns about the emergence and spread of escape variants,which may evade human immunity and eventually render candidate vaccines and antibody-based therapeutics ineffective.Indeed,some naturally mutated SARS-CoV or MERS-CoV strains from the sequential outbreaks were reported to resist neutralization by the antibodies isolated during the first outbreak1,2.

Recent advances in“universal”influenza virus antibodies:the rise of a hidden trimeric interface in hemagglutinin globular head

Influenza causes seasonal outbreaks yearly and unpredictable pandemics with high morbidity and mortality rates.Despite significant efforts to address influenza,it remains a major threat to human public health.This issue is partially due to the lack of antiviral drugs with potent antiviral activity and broad reactivity against all influenza virus strains and the rapid emergence of drug-resistant variants.Moreover,designing a universal influenza vaccine that is sufficiently immunogenic to induce universal antibodies is difficult.Some novel epitopes hidden in the hemagglutinin(HA)trimeric interface have been discovered recently,and a number of antibodies targeting these epitopes have been found to be capable of neutralizing a broad range of influenza isolates.These findings may have important implications for the development of universal influenza vaccines and antiviral drugs.In this review,we focused on the antibodies targeting these newly discovered epitopes in the HA domain of the influenza virus to promote the development of universal anti-influenza antibodies or vaccines and extend the discovery to other viruses with similar conformational changes in envelope proteins.

A non-ACE2 competing human single-domain antibody confers broad neutralization against SARS-CoV-2 and circulating variants

The current COVID-19 pandemic has heavily burdened the global public health system and may keep simmering for years.The frequent emergence of immune escape variants have spurred the search for prophylactic vaccines and therapeutic antibodies that confer broad protection against SARS-CoV-2 variants.Here we show that the bivalency of an affinity maturated fully human singledomain antibody(n3113.1-Fc)exhibits exquisite neutralizing potency against SARS-CoV-2 pseudovirus,and confers effective prophylactic and therapeutic protection against authentic SARS-CoV-2 in the host cell receptor angiotensin-converting enzyme 2(ACE2)humanized mice.The crystal structure of n3113 in complex with the receptor-binding domain(RBD)of SARS-CoV-2,combined with the cryo-EM structures of n3113 and spike ecto-domain,reveals that n3113 binds to the side surface of up-state RBD with no competition with ACE2.The binding of n3113 to this novel epitope stabilizes spike in up-state conformations but inhibits SARS-CoV-2 S mediated membrane fusion,expanding our recognition of neutralization by antibodies against SARS-CoV-2.Binding assay and pseudovirus neutralization assay show no evasion of recently prevalent SARS-CoV-2 lineages,including Alpha(B.1.1.7),Beta(B.1.351),Gamma(P.1),and Delta(B.1.617.2)for n3113.1-Fc with Y58L mutation,demonstrating the potential of n3113.1-Fc(Y58L)as a promising candidate for clinical development to treat COVID-19.

Inhalable antibodies for the treatment of COVID-19

By the end of July 2022,the SARS-CoV-2 pandemic had caused more than 6 million deaths worldwide.This viral infection results in a series of atypical respiratory diseases termed COVID-19,from asymptomatic infection to severe symptoms such as acute respiratory distress syndrome and pulmonary fibrosis.Development of vaccines and therapeutic measures that mitigate the sufferings caused by the pandemic has been achieved in a short period of time.Only 1 year after the emergence of the pandemic,COVID-19 vaccines have been approved in several countries.

Characterization of human IgM and IgG repertoires in individuals with chronic HIV-1 infection

Advancements in high-throughput sequencing(HTS)of antibody repertoires(Ig-Seq)have unprecedentedly improved our ability to characterize the antibody repertoires on a large scale.However,currently,only a few studies explored the influence of chronic HIV-1 infection on human antibody repertoires and many of them reached contradictory conclusions,possibly limited by inadequate sequencing depth and throughput.To better understand how HIV-1 infection would impact humoral immune system,in this study,we systematically analyzed the differences between the IgM(HIV-IgM)and IgG(HIV-IgG)heavy chain repertoires of HIV-1 infected patients,as well as between antibody repertoires of HIV-1 patients and healthy donors(HH).Notably,the public unique clones accounted for only a negligible proportion between the HIV-IgM and HIV-IgG repertoires libraries,and the diversity of unique clones in HIV-IgG remarkably reduced.In aspect of somatic mutation rates of CDR1 and CDR2,the HIV-IgG repertoire was higher than HIV-IgM.Besides,the average length of CDR3 region in HIV-IgM was significant longer than that in the HH repertoire,presumably caused by the great number of novel VDJ rearrangement patterns,especially a massive use of IGHJ6.Moreover,some of the B cell clonotypes had numerous clones,and somatic variants were detected within the clonotype lineage in HIV-IgG,indicating HIV-1 neutralizing activities.The in-depth characterization of HIV-IgG and HIV-IgM repertoires enriches our knowledge in the profound effect of HIV-1 infection on human antibody repertoires and may have practical value for the discovery of therapeutic antibodies.

Defining a highly conserved cryptic epitope for antibody recognition of SARS-CoV-2 variants

Dear Editor,In recent months,additional Omicron variants of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),including the BA.5 sublineage BF.7 and BQ.1.1 and the BA.2 linage recombination XBB,XBB.1.5 and XBB.1.16,have emerged following the BA.2 and BA.5 subvariants.Remarkably,BQ.1.1 and XBB showed substantial neutralization escape as compared with the previous variants,and have gradually become the dominant variants worldwide.1 These facts emphasize the urgency of identifying highly conserved SARS-CoV-2 epitopes,which would be essential for the design of universal vaccines and broadly neutralizing antibodies.

Insights into biological therapeutic strategies for COVID-19

The worldwide pandemic of novel coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)that emerged in late December 2019 requires the urgent development of therapeutic options.So far,numerous studies have investigated and uncovered the underlying epidemiology and clinical characteristics of COVID-19 infections in order to develop effective drugs.Compared with antiviral small-molecule inhibitors,biotherapeutics have unique advantages such as fewer side effects by virtue of their high specificity,and thus can be rapidly developed for promising treatments of COVID-19.Here,we summarize potential biotherapeutics and their mechanisms of action,including convalescent plasma,therapeutic antibodies,peptides,engineered ACE2,interferons,cytokine inhibitors,and RNAi-based therapeutics,and discuss in depth the advancements and precautions for each type of biotherapeutics in the treatment of COVID-19.