Camelid Single-Domain Antibodies As an Alternative to Overcome Challenges Related to the Prevention, Detection, and Control of Neglected Tropical Diseases

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Single-Domain Antibody-Gold Nanoparticle Bioconjugates as Immunosensors for the Detection of Hantaviruses

INTRODUCTION

Hantavirus, a zoonotic pathogen, causes severe syndromes like hemorrhagic fever with renal syndrome (HFRS), sometimes fatal in humans. Considering the importance of detecting the hantavirus antigen, the construction of an immunosensor is essential. The structural and functional characteristics of camelid nanobodies (VHHs) encourage their application in the areas of nanobiotechnology, therapeutics, diagnostics, and basic research. Therefore, this study aimed to standardize stable bioconjugates using gold nanoparticles (AuNPs) and VHHs, in order to develop immunobiosensors for the diagnosis of hantavirus infection.

METHODS

Immobilized metal affinity chromatography (IMAC) was performed to obtain purified recombinant anti-hantavirus nucleocapsid nanobodies (anti-prNΔ85 VHH), while AuNPs were synthesized for bioconjugation. UV-visible spectrophotometry and transmission electron microscopy (TEM) analysis were employed to characterize AuNPs.

RESULTS

The bioconjugation stability parameters (VHH-AuNPs), analyzed by spectrophotometry, showed that the ideal pH value and VHH concentration were obtained at 7.4 and 50 μg/mL, respectively, after addition of 1 M NaCl, which induces AuNP aggregation. TEM performed before and after bioconjugation showed uniform, homogeneous, well-dispersed, and spherical AuNPs with an average diameter of ~ 14 ± 0.57 nm. Furthermore, high-resolution images revealed a thin white halo on the surface of the AuNPs, indicating the coating of the AuNPs with protein. A biosensor simulation test (dot blot-like [DB-like]) was performed in stationary phase to verify the binding and detection limits of the recombinant nucleocapsid protein from the Araucária hantavirus strain (prN∆85).

DISCUSSION

Using AuNPs/VHH bioconjugates, a specific interaction was detected between 5 and 10 min of reaction in a dose-dependent manner. It was observed that this test was sensitive enough to detect prNΔ85 at concentrations up to 25 ng/μL. Considering that nanostructured biological systems such as antibodies conjugated with AuNPs are useful tools for the development of chemical and biological sensors, the stability of the bioconjugate indicates proficiency in detecting antigens. The experimental results obtained will be used in a future immunospot assay or lateral flow immunochromatography analysis for hantavirus detection.

Development of polyclonal heavy chain antibodies targeting programmed death ligand-1

Programmed death ligand-1 (PD-L1, CD274 and B7-H1) has been described as a ligand for immune inhibitory receptor programmed death protein 1 (PD-1). With binding to PD-1 on activated T cells, PD-L1 can prevent T cell responses via motivating apoptosis. Consequently, it causes cancers immune evasion and helps the tumor growth; hence, PD-L1 is regarded as a therapeutic target for malignant cancers. The anti-PD-L1 monoclonal antibody targeting PD-1/PD-L1 immune checkpoint has attained remarkable outcomes in clinical application and has turned to one of the most prevalent anti-cancer drugs. The present study aimed to develop polyclonal heavy chain antibodies targeting PD-L1via Camelus dromedarius immunization. The extra-cellular domain of human PD-L1 (hPD-L1) protein was cloned, expressed, and purified. Afterwards, this recombinant protein was utilized as an antigen for camel immunization to acquire polyclonal camelid sera versus this protein. Our outcomes showed that hPD-L1 protein was effectively expressed in the prokaryotic system. The antibody-based techniques, such as enzyme-linked immunosorbent assay, western blotting, and flow cytometry displayed that the hPD-L1 protein was detected by generated polyclonal antibody. Due to the advantages of multi-epitope-binding ability, our study exhibited that camelid antibody is effective to be applied significantly for detection of PD-L1 protein in essential antibody-based studies.

A Novel Fusion Protein System for the Production of Nanobodies and the SARS-CoV-2 Spike RBD in a Bacterial System

Antibodies are key proteins of the immune system, and they are widely used for both research and theragnostic applications. Among them, camelid immunoglobulins (IgG) differ from the canonical human IgG molecules, as their light chains are completely missing; thus, they have only variable domains on their heavy chains (VHHs). A single VHH domain, often called a nanobody, has favorable structural, biophysical, and functional features compared to canonical antibodies. Therefore, robust and efficient production protocols relying on recombinant technologies are in high demand. Here, by utilizing ecotin, an Escherichia coli protein, as a fusion partner, we present a bacterial expression system that allows an easy, fast, and cost-effective way to prepare nanobodies. Ecotin was used here as a periplasmic translocator and a passive refolding chaperone, which allowed us to reach high-yield production of nanobodies. We also present a new, easily applicable prokaryotic expression and purification method of the receptor-binding domain (RBD) of the SARS-CoV-2 S protein for interaction assays. We demonstrate using ECD spectroscopy that the bacterially produced RBD is well-folded. The bacterially produced nanobody was shown to bind strongly to the recombinant RBD, with a K_d of 10 nM. The simple methods presented here could facilitate rapid interaction measurements in the event of the appearance of additional SARS-CoV-2 variants.

Dengue virus infection - a review of pathogenesis, vaccines, diagnosis and therapy

The transmission of dengue virus (DENV) from an infected Aedes mosquito to a human, causes illness ranging from mild dengue fever to fatal dengue shock syndrome. The similar conserved structure and sequence among distinct DENV serotypes or different flaviviruses has resulted in the occurrence of cross reaction followed by antibody-dependent enhancement (ADE). Thus far, the vaccine which can provide effective protection against infection by different DENV serotypes remains the biggest hurdle to overcome. Therefore, deep investigation is crucial for the potent and effective therapeutic drugs development. In addition, the cross-reactivity of flaviviruses that leads to false diagnosis in clinical settings could result to delay proper intervention management. Thus, the accurate diagnostic with high specificity and sensitivity is highly required to provide prompt diagnosis in respect to render early treatment for DENV infected individuals. In this review, the recent development of neutralizing antibodies, antiviral agents, and vaccine candidates in therapeutic platform for DENV infection will be discussed. Moreover, the discovery of antigenic cryptic epitopes, principle of molecular mimicry, and application of single-chain or single-domain antibodies towards DENV will also be presented.

The Effectiveness of Brolucizumab and Aflibercept in Patients with Neovascular Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a progressive, chronic disease of the central area of the retina, which, if untreated, leads to blindness. This study aimed to compare the effectiveness of therapy using anti-VEGF drugs, namely brolucizumab and aflibercept, in patients with neovascular AMD (nAMD) during a monitoring period lasting around 20 weeks. The analysis consisted of 40 patients diagnosed with neovascular age-related macular degeneration, with 20 patients receiving aflibercept (Eylea, Bayer) at a dose of 2 mg/50 µL into the vitreous chamber at the following intervals—3 doses, 4 weeks apart, followed by a fourth dose after 8 weeks. The remaining 20 patients received brolucizumab (Beovu, Novartis) at a dose of 6 mg/50 µL, administered in the following schedule—3 initial doses, 4 weeks apart, with the administration of a fourth dose decided for each patient individually by the doctor, depending on disease activity, assessed through imaging tests. To evaluate treatment effectiveness, the following measurements were used: ‘read distance and near visual acuity’ for each eye separately using the Snellen chart; and non-invasive retinal imaging techniques—optical coherence tomography (OCT) and OCT angiography (OCTA). In patients treated using brolucizumab, during the observation period, statistically significant differences were found in the following parameters: flow area (p = 0.0277); select area (p = 0.0277); FOVEA (p = 0.0073); visus (p = 0.0064). In brolucizumab-treated patients, changes in OCT and OCTA, indicating an improvement, were already visible after the first injection of the drug, whereas in the aflibercept-treated group, changes were only visible after the fourth injection. We found a higher effectiveness of brolucizumab therapy compared to aflibercept in patients with nAMD during an observations period lasting 20 weeks. Our observations are significant, although they require further research.

BROLUCIZUMAB - A NEW PLAYER IN THE FIELD OF ANTI-VEGF THERAPY OF NEOVASCULAR AGE-RELATED MACULAR DEGENERATION. A REVIEW

Vascular endothelial growth factor (VEGF) has been identified as a major promoter of the development of choroidal neovascularization in age-related macular degeneration. The development of choroidal neovascularization can be slowed by preventing the binding of vascular endothelial growth factor to cellular VEGF receptor-2 present on vascular endothelial cells, which represents the major proangiogenic stimulus. Advances in the development of anti-VEGF therapy have led to significant improvement in visual acuity outcomes in recent years that neovascular age-related macular degeneration can no longer be considered an incurable disease. Despite its many advantages, the current standard of care, which is the frequent application of VEGF blockers to the vitreous, is a significant burden on both the patient and the healthcare system. This review is aim on a new brolucizumab molecule (also known as RTH 258 or formerly ESBA 1008). The article focuses on the molecular aspects of the drug and an overview of the basic preclinical and clinical studies that were performed during drug development. Brolucizumab is a single chain fragment of a humanized monoclonal antibody with a molecular weight of 26 kDa that inhibits VEGF-A. Preclinical animal studies have shown good penetration of the molecule through the retina with minimal systemic exposure. The SEE study (phase 1/2) demonstrated safety and tolerability after drug administration. The OSPREY (phase 2) study demonstrated the same efficacy of brolucizumab on visual acuity in the 8-week dosing regimen compared to aflibercept. In the same study, patients were also pilot tested in a 12-week dosing regimen. The HAWK and HARRIER studies (phase 3) demonstrated the efficacy of the drug at a dose of 6 mg in a 12-week dosing schedule in 55.6 % and 51 % of patients, respectively.

Off label intravitreal Brolucizumab in treatment of recurrent macular edema due to branch retinal vein occlusion: A case report

A 59 year old female presented with progressive loss of vision in right eye (RE) of 6 months duration. She had been diagnosed with inferotemporal branch retinal vein occlusion with macular edema in RE and had received 4 doses of intravitreal Ranibizumab previously. Best corrected visual acuity in RE was 20/120, N24. Optical coherence tomography scans of RE showed significant cystoid macular edema with central macular thickness of 546 µm. She was treated with single dose of intravitreal Brolucizumab (6 mg/0.05 ml). Vision improved to 20/32, N6 one month following injection with return to normal foveal architecture. Visual gains and reduction in central macular thickness were maintained with no recurrence of macular edema 2 months following the procedure. No adverse effects were noted during the entire follow up.

A comprehensive comparison between camelid nanobodies and single chain variable fragments

By the emergence of recombinant DNA technology, many antibody fragments have been developed devoid of undesired properties of natural immunoglobulins. Among them, camelid heavy-chain variable domains (VHHs) and single-chain variable fragments (scFvs) are the most favored ones. While scFv is used widely in various applications, camelid antibodies (VHHs) can serve as an alternative because of their superior chemical and physical properties such as higher solubility, stability, smaller size, and lower production cost. Here, these two counterparts are compared in structure and properties to identify which one is more suitable for each of their various therapeutic, diagnosis, and research applications.

Strategic Development of an Immunotoxin for the Treatment of Glioblastoma and Other Tumours Expressing the Calcitonin Receptor

New strategies aimed at treatment of glioblastoma are frequently proposed to overcome poor prognosis. Recently, research has focused on glioma stem cells (GSCs), some quiescent, which drive expansion of glioblastoma and provide the complexity and heterogeneity of the tumour hierarchy. Targeting quiescent GSCs is beyond the capability of conventional drugs such as temozolomide. Here, we discuss the proposal that the calcitonin receptor (CT Receptor), expressed in 76–86% of patient biopsies, is expressed by both malignant glioma cells and GSCs. Forty-two percent (42%) of high-grade glioma (HGG; representative of GSCs) cell lines available from one source express CT Receptor protein in cell culture. The pharmacological calcitonin (CT)-response profiles of four of the HGG cell lines were reported, suggesting mutational/splicing inactivation. Alternative splicing, commonly associated with cancer cells, could result in the predominant expression of the insert-positive isoform and explain the atypical pharmacology exhibited by CT non-responders. A role for the CT Receptor as a putative tumour suppressor and/or oncoprotein is discussed. Both CT responders and non-responders were sensitive to immunotoxins based on an anti-CT Receptor antibody conjugated to ribosomal-inactivating proteins. Sensitivity was increased by several logs with the triterpene glycoside SO1861, an endosomal escape enhancer. Under these conditions, the immunotoxins were 250–300 times more potent than an equivalent antibody conjugated with monomethyl auristatin E. Further refinements for improving the penetration of solid tumours are discussed. With this knowledge, a potential strategy for effective targeting of CSCs expressing this receptor is proposed for the treatment of GBM.

A case of recalcitrant neovascular wet age-related macular degeneration treated with Intravitreal Brolucizumab

A 72-year-old male presented with loss of vision in left eye of 1 year duration. Patient had been diagnosed with wet neovascular age related macular degeneration in left eye and had received multiple injections of anti- vascular endothelial growth factor agents in past. Clinical and imaging studies showed persistent subretinal fluid. The patient was shifted to intravitreal Brolucizumab. There was complete resolution of subretinal fluid with improvement of vision 1 month following injection. Improvement of vison was maintained 3 months following injection with macula remaining dry.

Camelid Single-Domain Antibodies for the Development of Potent Diagnosis Platforms

The distinct biophysical and pharmaceutical properties of camelid single-domain antibodies, referred to as VHHs or nanobodies, are associated with their nanometric dimensions, elevated stability, and antigen recognition capacity. These biomolecules can circumvent a number of diagnostic system limitations, especially those related to the size and stability of conventional immunoglobulins currently used in enzyme-linked immunosorbent assays and point-of-care, electrochemical, and imaging assays. In these formats, VHHs are directionally conjugated to different molecules, such as metallic nanoparticles, small peptides, and radioisotopes, which demonstrates their comprehensive versatility. Thus, the application of VHHs in diagnostic systems range from the identification of cancer cells to the detection of degenerative disease biomarkers, viral antigens, bacterial toxins, and insecticides. The improvements of sensitivity and specificity are among the central benefits resulting from the use of VHHs, which are indispensable parameters for high-quality diagnostics. Therefore, this review highlights the main biotechnological advances related to camelid single-domain antibodies and their use in in vitro and in vivo diagnostic approaches for human health.

Brolucizumab: a novel anti-VEGF humanized single-chain antibody fragment for treating w-AMD

INTRODUCTION

Wet age-related macular degeneration (w-AMD) represents the leading cause of visual impairment in the elderly in the developed countries. Intravitreal antivascular endothelial growth factor (VEGF) drugs are currently considered as the first-line treatment option for treating w-AMD; however, the frequent injection intervals have lit the way to investigate novel anti-VEGF agents allowing a more extended treatment regimen. Brolucizumab is a single-chain antibody fragment targeting all the isoforms of VEGF-A. Phase III HAWK and HARRIER trials have shown a longer durability and superior anatomical outcomes as compared with the standard of care by adopting a quarterly regimen for treating w-AMD. Brolucizumab has been approved in Europe, USA, and Japan for the management of w-AMD.

AREAS COVERED

This article presents an overview of w-AMD and investigates the progress of brolucizumab through clinical trials. It offers insights into where brolucizumab may be placed in the current market of anti-VEGF agents and its potential advantages over the previous molecules adopted for treating w-AMD.

EXPERT OPINION

The possibility of administering brolucizumab with more dilated treatment intervals represents an important advantage to decrease the treatment burden and improve patient compliance. Brolucizumab represents a possible drug switching option in non-responding patients to other anti-VEGF drugs.

Neovascular Macular Degeneration: A Review of Etiology, Risk Factors, and Recent Advances in Research and Therapy

Neovascular age-related macular degeneration (exudative or wet AMD) is a prevalent, progressive retinal degenerative macular disease that is characterized by neovascularization of the choroid, mainly affecting the elderly population causing gradual vision impairment. Risk factors such as age, race, genetics, iris color, smoking, drinking, BMI, and diet all play a part in nvAMD's progression, with anti-vascular endothelial growth factor (anti-VEGF) therapy being the mainstay of treatment. Current therapeutic advancements slow the progression of the disease but do not cure or reverse its course. Newer therapies such as gene therapies, Rho-kinase inhibitors, and levodopa offer potential new targets for treatment.

Zika virus serological diagnosis: commercial tests and monoclonal antibodies as tools

Zika virus (ZIKV), an emerging arthropod-borne virus (arbovirus) of the Flaviviridae family, is a current issue worldwide, particularly because of the congenital and neurological syndromes associated with infection by this virus. As the initial clinical symptoms of all diseases caused by this group are very similar, clinical diagnosis is difficult. Furthermore, laboratory diagnostic efforts have failed to identify specific and accurate tests for each virus of the Flaviviridae family due to the cross-reactivity of these viruses in serum samples. This situation has resulted in underreporting of the diseases caused by flaviviruses. However, many companies developed commercial diagnostic tests after the recent ZIKV outbreak. Moreover, health regulatory agencies have approved different commercial tests to extend the monitoring of ZIKV infections. Considering that a specific and sensitive diagnostic method for estimating risk and evaluating ZIKV propagation is still needed, this review aims to provide an update of the main commercially approved serological diagnostics test by the US Food and Drug Administration (FDA) and Brazilian National Health Surveillance Agency (ANVISA). Additionally, we present the technologies used for monoclonal antibody production as a tool for the development of diagnostic tests and applications of these antibodies in detecting ZIKV infections worldwide.

Humoral responses to Schistosoma japonicum soluble egg antigens in domestic animals in Lindu Subdistrict, Central Sulawesi Province, Indonesia

Background and Aim: Schistosomiasis japonica, a disease caused by Schistosoma japonicum, is a public health problem in the Philippines, the Republic of Indonesia, and the People's Republic of China. The disease is known as zoonotic, meaning other than humans, animals are involved as the reservoirs. In Indonesia, schistosomiasis surveillance in animals is not continuous. Thus, the study to determine the prevalence of the disease in animals is needed. The study was aimed to determine the seroprevalence of S. japonicum infection among four species of domestic animals in the Lindu Sub-district, Central Sulawesi Province of Indonesia. Materials and Methods: Blood samples of domestic animals were collected and analyzed for the presence of anti-S. japonicum immunoglobulin G antibodies against S. japonicum soluble egg antigens using the indirect hemagglutination assay. Animal stool samples were collected, and the miracidia-hatching assay was used for the detection of S. japonicum infection. Additional data concerning the animal identity and the management practices were obtained through a questionnaire used in surveys and interviews. Results: A total of 146 sera from 13 cattle, 24 buffaloes, 54 pigs, and 55 dogs were collected. The overall schistosomiasis seroprevalence was 64.4%. The serology prevalence in cattle, buffalo, pig, and dog was 100.0%, 41.7%, 74.1%, and 56.4%, respectively. Domestic animals in all of five villages have previous exposure with S. japonicum as seropositive animals detected in every village. A total of 104 animal stool samples from 146 animals sampled were obtained. The overall schistosomiasis prevalence determined by the miracidia hatching assay was 16.35%. The sensitivity and specificity of indirect hemagglutination assay (IHA) in the current study were 88.24% and 41.37%, respectively, with miracidia hatching assay as the gold-standard method. Conclusion: This study has shown a high seroprevalence of schistosomiasis japonica among domestic animals in the Lindu Subdistrict. IHA can be used as the screening method for the detection of S. japonicum infection in domestic animals. Chemotherapy and animal livestock grazing management programs to reduce the parasite burden and Schistosoma egg contamination in the environment must be implemented as part of one health approaches, in addition to other control measures.

CRISPR interference of nucleotide biosynthesis improves production of a single-domain antibody in Escherichia coli

Growth decoupling can be used to optimize the production of biochemicals and proteins in cell factories. Inhibition of excess biomass formation allows for carbon to be utilized efficiently for product formation instead of growth, resulting in increased product yields and titers. Here, we used CRISPR interference to increase the production of a single‐domain antibody (sdAb) by inhibiting growth during production. First, we screened 21 sgRNA targets in the purine and pyrimidine biosynthesis pathways and found that the repression of 11 pathway genes led to the increased green fluorescent protein production and decreased growth. The sgRNA targets pyrF, pyrG, and cmk were selected and further used to improve the production of two versions of an expression‐optimized sdAb. Proteomics analysis of the sdAb‐producing pyrF, pyrG, and cmk growth decoupling strains showed significantly decreased RpoS levels and an increase of ribosome‐associated proteins, indicating that the growth decoupling strains do not enter stationary phase and maintain their capacity for protein synthesis upon growth inhibition. Finally, sdAb production was scaled up to shake‐flask fermentation where the product yield was improved 2.6‐fold compared to the control strain with no sgRNA target sequence. An sdAb content of 14.6% was reached in the best‐performing pyrG growth decoupling strain.

Nanobodies: a new approach for the diagnosis and treatment of viral infectious diseases

With the rise of viral infections and antibiotic resistance, there is a constant need for the development of more sensitive and effective treatment and diagnostic tools. Since their discovery in the early 1990s, Camelidae antibodies have been investigated as potential tools due to their unique structure and favorable characteristics. Members of this family produce conventional IgG antibodies as well as heavy-chain only IgG antibodies that do not possess light chains. The variable domain (VHH), or nanobody, demonstrates unique antigen-binding capabilities, enhanced stability, and its small size allows for delivery into the body using a nebulizer, thereby eliminating the unfavorable use of injections. In addition, the cost-effective and easy in vitro production of these antibodies are an attractive quality in terms of mass production. This review covers the past and current nanobody treatment and diagnostic developments aimed at viral infectious diseases, including a brief overview of protozoal, bacterial, and veterinary viral approaches.

Brolucizumab: Evolution through Preclinical and Clinical Studies and the Implications for the Management of Neovascular Age-Related Macular Degeneration

Improving or maintaining visual acuity is the main goal for the treatment of neovascular age-related macular degeneration (nAMD). Current nAMD standard of care dictates frequent intravitreal (IVT) anti-vascular endothelial growth factor (VEGF) injections, which places a substantial burden on patients, caregivers, and physicians. Brolucizumab, a newly developed anti-VEGF molecule for nAMD treatment, has demonstrated longer durability and improvement in visual and anatomic outcomes in clinical studies in a q12-week regimen, indicating its potential to reduce treatment burden as an important therapeutic tool in nAMD management. This review focuses on the development of brolucizumab and the preclinical and clinical studies evaluating its efficacy, tolerability, and safety. Brolucizumab (also known as "RTH258" and "ESBA1008") is a humanized, single-chain variable fragment (scFv) antibody with a molecular mass of approximately 26 kDa that inhibits VEGF-A. Preclinical studies show that brolucizumab readily penetrates the retina to reach the retinal pigment epithelium (RPE)/choroid with minimal subsequent systemic exposure. The safety, tolerability, and efficacy of a single IVT brolucizumab administration in patients with treatment-naïve nAMD were first demonstrated in the SEE Phase 1/2 study. The OSPREY Phase 2 study showed brolucizumab to be as efficacious as aflibercept in a q8-week regimen with regard to best-corrected visual acuity (BCVA) and brolucizumab achieving greater fluid resolution. Brolucizumab-treated patients in the OSPREY study were subsequently challenged with a q12-week dosing interval, and the outcomes provided key information for the study design and end points of the Phase 3 studies. In the HAWK and HARRIER Phase 3 studies, after 3 monthly loading injections, brolucizumab treatment regimen (q12-week or q8-week) was guided by individual disease activity assessment using functional and anatomic parameters (central subfield thickness [CST], intraretinal fluid [IRF], or subretinal fluid [SRF]) versus aflibercept (q8-week). Fewer brolucizumab 6-mg treated eyes had disease activity versus aflibercept, and anatomic outcome results at weeks 16 and 48 demonstrate brolucizumab as a potent drying agent. Moreover, of patients treated with 6 mg brolucizumab, 55.6% and 51.0% maintained a q12-week dosing interval immediately after the loading phase until week 48 in HAWK and HARRIER, respectively. These Phase 3 studies demonstrated that the brolucizumab q12-week regimen maintains efficacy and safety while reducing treatment burden associated with regular IVT injections for patients with nAMD.

How can monoclonal antibodies be harnessed against neglected tropical diseases and other infectious diseases?

Introduction: Monoclonal antibody-based therapies now represent the single-largest class of molecules undergoing clinical investigation. Although a handful of different monoclonal antibodies have been clinically approved for bacterial and viral indications, including rabies, therapies based on monoclonal antibodies are yet to fully enter the fields of neglected tropical diseases and other infectious diseases. Areas covered: This review presents the current state-of-the-art in the development and use of monoclonal antibodies against neglected tropical diseases and other infectious diseases, including viral, bacterial, and parasitic infections, as well as envenomings by animal bites and stings. Additionally, a short section on mushroom poisonings is included. Key challenges for developing antibody-based therapeutics are discussed for each of these fields. Expert opinion: Neglected tropical diseases and other infectious diseases represent a golden opportunity for academics and technology developers for advancing our scientific capabilities within the understanding and design of antibody cross-reactivity, use of oligoclonal antibody mixtures for multi-target neutralization, novel immunization methodologies, targeting of evasive pathogens, and development of fundamentally novel therapeutic mechanisms of action. Furthermore, a huge humanitarian and societal impact is to gain by exploiting antibody technologies for the development of biotherapies against diseases, for which current treatment options are suboptimal or non-existent.

Selection and Characterization of Anti-Dengue NS1 Single Domain Antibodies

Reliable detection and diagnosis of dengue virus (DENV) is important for both patient care and epidemiological control. Starting with a llama immunized with a mixture of recombinant nonstructural protein 1 (NS1) antigen from the four DENV serotypes, a phage display immune library of single domain antibodies was constructed and binders selected which exhibited specificity and affinity for DENV NS1. Each of these single domain antibodies was evaluated for its binding affinity to NS1 from the four serotypes, and incorporated into a sandwich format for NS1 detection. An optimal pair was chosen that provided the best combination of sensitivity for all four DENV NS1 antigens spiked into 50% human serum while showing no cross reactivity to NS1 from Zika virus, yellow fever virus, tick-borne encephalitis virus, and minimal binding to NS1 from Japanese encephalitis virus and West Nile virus. These rugged and robust recombinant binding molecules offer attractive alternatives to conventional antibodies for implementation into immunoassays destined for resource limited locals.

A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes through their two different arms. bsAbs have been actively studied for their ability to directly recruit immune cells to kill tumor cells. Currently, the majority of bsAbs are produced in the form of recombinant proteins, either as Fc-containing bsAbs or as smaller bsAb derivatives without the Fc region. In this study, GPC3-S-Fab, an antibody fragment (Fab) based bispecific antibody, was designed by linking the Fab of anti-GPC3 antibody GC33 with an anti-CD16 single domain antibody. The GPC3-S-Fab can be expressed in Escherichia coli and purified by two affinity chromatographies. The purified GPC3-S-Fab can specifically bind to and kill GPC3 positive liver cancer cells by recruiting natural killer cells, suggesting a potential application of GPC3-S-Fab in liver cancer therapy.

Peptide and protein nanoparticle conjugates: versatile platforms for biomedical applications

Peptide- and protein-nanoparticle conjugates have emerged as powerful tools for biomedical applications, enabling the treatment, diagnosis, and prevention of disease. In this review, we focus on the key roles played by peptides and proteins in improving, controlling, and defining the performance of nanotechnologies. Within this framework, we provide a comprehensive overview of the key sequences and structures utilised to provide biological and physical stability to nano-constructs, direct particles to their target and influence their cellular and tissue distribution, induce and control biological responses, and form polypeptide self-assembled nanoparticles. In doing so, we highlight the great advances made by the field, as well as the challenges still faced in achieving the clinical translation of peptide- and protein-functionalised nano-drug delivery vehicles, imaging species, and active therapeutics.

Camelid Single-Domain Antibodies: Historical Perspective and Future Outlook

Tremendous effort has been expended over the past two and a half decades to understand many aspects of camelid heavy chain antibodies, from their biology, evolution, and immunogenetics to their potential applications in various fields of research and medicine. In this article, I present a historical perspective on the development of camelid single-domain antibodies (sdAbs or V_HHs, also widely known as nanobodies) since their discovery and discuss the advantages and disadvantages of these unique molecules in various areas of research, industry, and medicine. Commercialization of camelid sdAbs exploded in 2001 with a flurry of patents issued to the Vrije Universiteit Brussel (VUB) and later taken on by the Vlaams Interuniversitair Instituut voor Biotechnologie (VIB) and, after 2002, the VIB-founded spin-off company, Ablynx. While entrepreneurial spirit has certainly catalyzed the exploration of nanobodies as marketable products, IP restrictions may be partially responsible for the relatively long time span between the discovery of these biomolecules and their entry into the pharmaceutical market. It is now anticipated that the first V_HH-based antibody drug, Caplacizumab, a bivalent anti-vWF antibody for treating rare blood clotting disorders, may be approved and commercialized in 2018 or shortly thereafter. This elusive first approval, along with the expiry of key patents, may substantially alter the scientific and biomedical landscape surrounding camelid sdAbs and pave the way for their emergence as mainstream biotherapeutics.