Recombinant Antibodies-A Growing Market

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Recombinant antibody production is a practice that is constantly growing. The use of innovative techniques has widened the spectrum of its application in therapies and research in recent years. So much so that currently, the worldwide therapeutic antibody market is estimated at around $50 billion/year, the diagnostic market exceeds $10 billion/year, and the research market expenses are around $3 billion/year (1), revealing that recombinant antibodies are gaining unprecedented popularity.

The Engineering of Recombinant Antibodies

Recombinant antibodies (rAbs) are antibody fragments produced in vitro by using recombinant synthetic genes. Unlike monoclonal antibodies, rAbs do not require hybridomas or animals for their synthesis (2). Antibody genes are isolated and subsequently incorporated into plasmid DNA vectors. These are then transferred into hosts such as bacteria or mammalian cells, which then behave as transcriptors that will express the desired protein. Today, the most produced antibodies are the Fab fragments, single-chain fragment variables (scFV), and single domain antibodies (sdAb) (2).

The first type, the Fab fragment, contains four domains — one constant domain and one variable domain of each of the heavy and light chains in immunoglobulins — and has a molecular weight of around 50 kDa. Fab fragments are commonly used in toxicology, for the detection of free drugs in serum, as they compete with drugs for the binding sites of antibodies.

A scFV polypeptide, the second type of antibody, contains the variable domains of the heavy and light chains of immunoglobulins, linked by a flexible peptide linker, and has a molecular weight of around 27 kDa. ScFV polypeptide recombinant antibodies operate as drugs, as components of drugs, or as domains of drug candidates. They are also utilized to measure protein-protein interactions (3).

The final type, sdAb, consists of a single monomeric variable antibody domain. Because these recombinant antibodies are very small and stable, transformation into bacterial cells is easy, making them valuable elements for research purposes (3).

Recombinant Antibodies in Action

The development of new technologies to measure binding affinity and protein stability has substantially contributed to the engineering and design of highly specific recombinant antibodies. Better techniques have also reduced the propensity of rAbs to misfold and aggregate, helping to preserve the quaternary structure of the protein and its functionality.

Recombinant antibodies require less antigen and are faster to produce than monoclonal antibodies, which means they can take fewer months to synthesize (3). rAbs can easily fuse with a wide range of toxins and drugs, and therefore can be used in therapeutics (4). In addition, their production does not necessarily require the use of animals.

The improvement in the quality and quantity of rAbs has contributed to building antibody libraries that are of high input in the design of targeted therapies to treat many diseases, such as cancer. This is the case with Ibritumomab Tiuxetan Zevalin™, used for cancer radioimmunotherapy and the anti-programmed death-1 Nivolumab Opdivo™, used for the treatment of advanced cancers. Many other therapies have also gained FDA approval (5,6).

Furthermore, there are many advantages in using rAbs to develop immunosensors or immunoassays (7). There has been an increasing use of these antibodies as recognition elements for biosensors to detect antigens or cells bearing antigens. They can be chemically modified under controlled conditions to increase their avidity and sensitivity and in that way, replace traditional whole antibodies that can often lack specificity or present cross reactivity (7).

The flexibility of recombinant antibody coupling with nanoparticles reveals a promissory future for nanomedicine. Given the convincing treatment results and supplementary evidence, we can anticipate the release of many rAbs that are already in the pipeline in the near future.

SOURCES:

  1. De Marco A. Recombinant antibody production evolves into multiple options aimed at yielding reagents suitable for application-specific needs. Microb Cell Fact. 2015; 14: 125. Published online 2015 Sep 2. doi:  10.1186/s12934-015-0320-7
  2. Hornsby M. et al.  A High Through-put Platform for Recombinant Antibodies to Folded Proteins. Mol Cell Proteomics. 2015 Oct; 14(10): 2833–2847. Published online 2015 Aug 19. doi:  10.1074/mcp.O115.052209
  3. Smith K, et al. Demystified… Recombinant antibodies. J Clin Pathol. 2004 Sep; 57(9): 912–917. doi:  10.1136/jcp.2003.014407.
  4. Pietersz GA. et al. Therapeutic targeting in nanomedicine: the future lies in recombinant antibodies. Nanomedicine (Lond). 2017 Aug;12(15):1873-1889. doi: 10.2217/nnm-2017-0043. Epub 2017 Jul 13.
  5. Chamarthy M, et al. Radioimmunotherapy of Non-Hodgkin’s Lymphoma: From the ‘Magic Bullets’ to ‘Radioactive Magic Bullets’. Yale J Biol Med. 2011 Dec; 84(4): 391–407. Published online 2011 Dec.
  6. Rajan A, et al. Nivolumab, anti-programmed death-1 (PD-1) monoclonal antibody immunotherapy: Role in advanced cancers. Hum Vaccin Immunother. 2016 Sep; 12(9): 2219–2231. Published online 2016 May 2. doi: 10.1080/ 21645515.2016.1175694

Zeng X, Shen Z, Mernaugh R. Recombinant antibodies and their use in biosensors. Anal Bioanal Chem. Author manuscript; available in PMC 2018 Jan 12. Published in final edited form as: Anal Bioanal Chem. 2012 Apr; 402(10): 3027–3038.  Published online 2011 Dec 13. doi:  10.1007/s00216-011-5569-z

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