nAb: Camelid Antibodies, Nanobodies, VHH

Ablynx Develops Nano Antibody for Treatment of Rare Clotting Disorder

Last week, Ablynx announced substantial progress in the development of the nano antibody drug caplicizumab to treat acquired thrombotic thrombocytopenic purpura (aTTP), a rare, but life-threatening autoimmune disease. The Belgian biopharmaceutical company has submitted a Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) for approval. If accepted, caplicizumab will not only be the first therapeutic specifically indicated for the treatment of aTTP, but also the first approved nano antibody drug on the market.

aTTP is characterized by the autoimmune impairment of ADAMTS13, an enzyme that normally cleaves multimeric von Willebrand factor (vWF) into its functional form. Without the function of ADAMTS13, multimeric vWF forms aggregates with platelets in the blood. Low free platelet count and excess clotting result in thrombotic complications and a significant risk of organ damage due to the blockages of blood flow to tissues.

The current standard of care for aTTP involves immunosuppression and daily plasma exchange transfusion, in which a patient’s plasma is replaced with donor plasma to remove platelet-vWF aggregates. Caplicizumab is an anti-vWF nano antibody that prevents the formation of aggregates by blocking the interaction of multimeric vWF complexes with platelets.

While dozens of monoclonal antibodies have been approved by the FDA for therapeutic use (with hundreds more undergoing clinical trials), caplicizumab is the first therapeutic nano antibody. Nano antibodies are single-domain antibody fragments that bear full antigen binding capacity like monoclonal antibodies, but have a smaller size and unique structure, giving them features of small-molecule drugs. Nano antibodies are more stable than conventional monoclonal antibodies, allowing for multiple administration routes, and can be humanized to lower toxicity and immunogenicity. Because they are encoded by single genes, nano antibodies are easier and more cost-effective than traditional antibodies to engineer and manufacture.

Currently, caplicizumab is undergoing Phase III clinical trials and a three-year follow-up study has been initiated to determine the long-term safety and efficacy of this drug. Ablynx aims to commercialize caplicizumab in North America and Europe upon the trial’s conclusion and approval of BLA filing in 2018.

With the obvious advantages of nano antibodies over conventional monoclonal antibodies as biological drugs, caplicizumab is likely only the first of many to come.

Allele Researchers Engineer Modified Nanoantibodies to Increase Sensitivity in Biochemical Assays

Researchers at Allele have published new work demonstrating a novel application for nanoantibodies (nAbs) in direct signal amplification. nAbs have distinguishable qualities that set them apart from their traditional IgG counterparts, including significantly smaller size, better stability, and excellent specificity. However, because of their small size, there are no suitable secondary antibodies for traditional assays like immunohistochemistry, immunofluorescence, and other biochemical assays that require an enhanced signal.

The researchers engineered a modified nAb, termed “nAb Plus,” to directly amplify nAb signal detection through the addition of a small scaffolding protein containing numerous reporter binding sites. nAb Plus bypasses the need for secondary antibodies or additional amplification steps, streamlining biochemical assays and decreasing costs of reagents. The authors demonstrate the use of nAb Plus using immunohistochemistry, an assay typically requiring one or more signal amplification steps. However, nAb Plus could also be incorporated in any biochemical assay needing signal enhancement.

Abstract: Revealing the spatial arrangement of molecules within a tissue through immunohistochemistry (IHC) is an invaluable tool in biomedical research and clinical diagnostics. Choosing both the appropriate antibody and amplification system is paramount to the pathologic interpretation of the tissue at hand. The use of single domain VHH nanoantibodies (nAbs) promise more robust and consistent results in IHC, but are rarely used as an alternative to conventional immunoglobulin G (IgG) antibodies. nAbs are originally obtained from llamas and are the smallest antigen-binding fragments available. To determine whether the unique biophysical properties of nAbs give them an advantage in IHC, we first compared a basic fibroblast growth factor nAb to polyclonal IgG antibodies using tissue isolated from pancreatic adenocarcinoma. The nAb was extremely effective in antigen signal detection and allowed for a more streamlined and reproducible protocol. Furthermore, because nAbs are expressed in Escherichia coli from a single gene, they are quite amenable to genetic engineering. As such, we then covalently bound a highly biotinylated amplifier protein to basic fibroblast growth factor and p16 nAbs (termed nAb Plus), resulting in improved IHC sensitivity. The use of a biotinylated nAb Plus not only achieved local, covalent signal amplification, but also eliminated the need for a secondary antibody and subsequent amplification steps. These results highlight nAbs as valuable alternatives to conventional IgG antibodies, decreasing overall processing time and costs of reagents while increasing sensitivity and reproducibility across individual IHC assays.

Link to full text

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The NIH Awards Allele with Grant for the Development of a New Antibody Therapy for Treating Alzheimer’s Disease

SAN DIEGO–(BUSINESS WIRE)–

The National Institute on Aging of the NIH has awarded a grant to Allele Biotechnology and Pharmaceuticals (“Allele”) to develop a new antibody therapy for treating Alzheimer’s disease. Alzheimer’s disease is the most common cause of dementia, but there are currently no treatments to stop or reverse its progression.

Alongside academic collaborators, scientists at Allele have revealed a strong correlation between a previously uncharacterized target gene and Alzheimer’s disease. They discovered that expression of the gene reduces beta-amyloid production and tau phosphorylation, two components of plaque formation in Alzheimer’s disease. Furthermore, high levels of this protein in the brain can counteract loss of synapses and cognitive impairments in mice.

Allele will generate a panel of antibodies that recognize this protein with the goal of employing one of these antibodies as a therapeutic drug candidate. The antibodies’ unique size and shape allow them to pass the blood-brain barrier to reach crucial regions of the brain, and each antibody can be easily modified and engineered to heighten its therapeutic potential. Researchers at Allele hope that an antibody treatment will improve the function of its target protein in the brains of Alzheimer’s patients and ultimately reduce pathogenesis of the disease.

Recombinant antibodies represent one of the most important classes of biological therapeutics: 80% of the best selling drugs on the market are antibodies; immune checkpoint therapies and CAR-T cell therapies rely on antibodies. Continuously seeking unique antibodies against high value targets is a key focus of Allele, along with its induced pluripotent stem cell (iPSC) programs and iPSC-based drug screening projects. With the support of the new NIH grant, Allele will not only move closer to finding antibody drug candidates in fighting one of the most devastating diseases, but also generate long-needed research tools for other scientists to further study Alzheimer’s disease. For example, fusion of these antibodies to fluorescent proteins such as mNeonGreen can be used to image Alzheimer’s disease-related factors in cultured neurons, astrocytes, oligodendrocytes, or “minibrain”-like organoids derived from human iPSCs.

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Researchers use GFP nano antibody to study organ growth

Single-domain nano antibodies have a broad range of applications in biochemistry due to their small size, high affinity, and high specificity. Now, a team of researchers from the University of Basel and the University of Zurich has demonstrated that nano antibodies can be used for research in complex living organisms such as Drosophila, uncovering another new and exciting application for nano antibodies.

The team used nano antibodies to develop an assay for studying morphogens, molecules that regulate the pattern of tissue growth and the positions of various cell types within tissue. Morphogens form long-range concentration gradients from a localized source, ultimately determining the fate and arrangement of cells that respond to that gradient. Drosophila is a classic model system for understanding how morphogens regulate organ development. One morphogen called Dpp controls uniform proliferation and growth of the wing imaginal disc. Yet because Dpp is an extracellular, diffusible protein, it is difficult to immobilize in situ. Therefore, despite over 20 years of studying the role of Dpp as a morphogen, the lack of a dynamic system for controlling Dpp gradients has prevented researchers from understanding precisely how Dpp governs development of the wing disc.

By developing a novel synthetic system using nano antibodies, the researchers were able to modulate the concentration gradient of Dpp at the protein level. Their system—coined “morphotrap”—uses a membrane-bound GFP nano antibody to “trap” GFP-tagged Dpp at different locations along the wing imaginal disc. By tethering Dpp in a controlled spatial manner, researchers were able to determine how Dpp gradients affect wing disc development. They discovered that the gradient of Dpp is required for the patterning of the wing disc but not for lateral growth, disproving one of the field’s popular theories that address the role of Dpp. In addition to resolving the controversy with respect to the role of Dpp as a morphogen, this study pioneers a new method for using nano antibodies in situ.

“Dpp spreading is required for medial but not for lateral wing disc growth.”
Harmansa S., Hamaratoglu F., Affolter M., Caussinus E.
Nature. 2015 Nov 19;527(7578):317-22. doi: 10.1038/nature15712. Epub 2015 Nov 9.

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A breakdown of your burning nAb questions

Allele Biotechnology just released its latest batch of nAbs (nano antibodies), the first wave on a long list of new antibodies to come! You might have a few questions about how these “antibodies of the future”, as we call them, can help your research:  What can I use them for?  How much should I use?  And how do they work compared to a traditional antibody? 
 
To answer these questions, we need to first discuss some antibody basics.  Conventional antibodies (your typical mouse or rabbit derived antibody) have a “Y” shape and tightly bind targeted antigens as a result of two factors.  The first is affinity between each monomer Fab fragment and the antigen.  The second is the fact that traditional antibodies are di-valent, i.e. they have two identical binding sites for each antigen, which is known as avidity. 
 
When developing a nano-antibody, we screen and select our clones to have extremely high affinity as a monomer.  This is because nAbs are mono-valent VHH fragments. The intrinsic high affinity VHHs possess for their antigens can make up for the lack of multivalency (avidity).  As a result, nAb binding is often superior to conventional antibody binding, which leads to superior performance in a variety of biological assays (immunoprecipitation, immune-staining, FACS staining, immunofluorescent imaging, etc.). 
 
Each nAb is roughly one tenth (1/10) the size of a traditional antibody.  The small size and stable conformation of nano-antibodies enable pinpointed localization of target antigens and allow access to antigen and cellular regions generally restrictive to larger antibodies. As a result of this smaller size, when measured by weight 1mg of a nAb is equivalent to 5 – 10mg of a traditional antibody (the lower end takes di-valency into account).  When substituting a nAb for a traditional antibody you can use as little as one tenth (1/10) the amount by weight. 
 
There are a couple of different ways to use nAbs.  The first is immobilizing the nano-antibody on a resin (i.e. magnetic-agarose resin) for immunoprecipitation.  The nano-antibody will not be released from the resin upon elution so you will not have contaminating bands.  The second method is direct labeling with a fluorescent dye or hapten.  nAb’s are compatible with standard NHS-ester amine chemistry binding.  This enables single or multiple fluorophore labeling per antibody.  Moving forward, additional platforms will be released that allow for a more flexible and adaptable labeling system, allowing you to harness nAbs for any biological assay you can imagine.  Have some suggestions? Don’t hesitate to let us know by emailing at nAb@allelebiotech.com. Or call 858-587-6645 and ask for a nAb expert.

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