Recombinant antibody technology addressed many problems associated with hybridoma platforms, opening the door to a new class of biologic drugs. Today, this technology continues to contribute to the discovery and development of new antibody-based therapeutics and improve the performance of novel modalities.
Many Drivers for the Recombinant Approach
Early monoclonal antibody (mAb) therapies were developed using the hybridoma platform, which requires production of the target antigen or immunogen and involves animal immunizations. The hybridoma technology suffers not only from ethical issues but also batch-to-batch variability, antibody heterogeneity, loss of antibody productivity, and limitations with respect to scale and cost. In addition, the process is time-consuming and typically takes multiple months from immunization to establishment of specific hybridoma clones and production of mAbs.1,2
Recombinant antibodies are generated from host cell lines by recombinant DNA technology. This approach not only greatly reduces the reliance on animal use but also enables the production of large quantities of products much more quickly — within just a few weeks in most cases.3,4 Since recombinant antibodies are based on the known DNA sequences and can be exactly replicated, their production is highly controlled, reproducible, and consistent.5 Moreover, recombinant antibodies offer advantages including targeting hybridoma-refractory antigens and amenability to antibody engineering.
Many Advantages of Engineering
Recombinant antibody engineering provides many opportunities for creating unique molecules with optimal attributes for treating specific diseases. The fragment crystallizable (Fc) region can be modified to prevent the initiation of any undesired responses, while tiny variable regions can be designed to bind to the target more effectively.6 The antibodies initially discovered in mice or other animals can be humanized to reduce potential immunogenicity.
In addition, years of experience inspires confidence about which changes are necessary to realize specific benefits. As artificial intelligence (AI) algorithms advance, the level of predictability will only increase. In fact, many drug developers are leveraging AI technologies to predict and analyze potential therapeutics from antibody sequences before production.7,8 Then high-throughput recombinant antibody production and characterization to validate the predictions in the wet lab further accelerate the discovery and development. Platform processes, meanwhile, allow for rapid scale-up of recombinant antibody production to meet clinical and commercial demand.
Fragment Understanding
One of the important advantages of recombinant antibody technology is the ability to explore and understand many flavors of mAbs –– limited only by the imagination. Recent years have witnessed the rise of engineered antibody fragments as biopharmaceuticals, such as monovalent formats (e.g., Fab, scFv, and VHH) and bispecific constructs (e.g., BiTE and Diabody).
The conventional mAbs have certain limitations in clinical applications. Immunoglobulin G (IgG) molecules are relatively large (~150 kDa), which can prevent them from effectively penetrating into tissues. In addition, the presence of the Fc region in the IgG molecule can mediate bystander activation of the immune system. However, antibody fragments not only retain the targeting specificity of intact mAbs but also possess superior properties for a range of therapeutic and diagnostic applications. Due to their small size, antibody fragments offer enhanced tissue penetration, the ability to bind to traditionally inaccessible epitopes, and reduced immunogenicity. Additionally, these fragments provide flexibility in structure and ease of production and engineering, and they serve as building blocks for novel constructs.
Production and purification of antibody fragments require extensive expertise, especially with the increase in their design complexity and diversification in recent years. A combination of aspects should be carefully considered, including design strategies, how the upstream production can offer high productivity while suppressing the generation of impurities, and what downstream processing requirements will likely be involved in producing the desired fragment in a highly pure form.9
Different Modifications for Research, Diagnostic, and Therapeutic Applications
While antibodies for research, diagnostic, and therapeutic applications must all exhibit high binding affinity and specificity, there are other aspects that are uniquely sought for each specific application. When biomedical researchers require antibodies that can penetrate different tissues to assess different molecular and behavioral characteristics, antibody fragments with better tissue penetration than the full-length IgG are ideal for these applications. In the field of diagnostics, engineered multivalent antibodies with enhanced antigen-binding avidity are promising agents.10–12 For therapeutic applications, recombinant antibodies can be modified in endless ways: to avoid cross-reactivity, to target effector cells more strongly, to enable site-specific conjugation to small molecule payloads, and to achieve many other desired characteristics.
Significant Potential Yet to be Unlocked
While there is tremendous excitement about the therapeutic possibilities presented by cell and gene therapies and other novel modalities, recombinant antibodies still have significant potential going forward. Recombinant antibodies, for instance, will continue to play critical roles in advancing treatments for various human diseases, including cancers and autoimmune, metabolic, and infectious diseases, because they enable targeted therapies with minimal side effects.13 Beyond mAbs, bispecifics, antibody fragments, antibody–drug conjugates, and other next-generation antibody therapeutics exhibit novel functionalities and have even greater targeting abilities and thus enhanced efficacy. From a diagnostic standpoint, recombinant antibodies allow the highly selective and sensitive detection of specific biomarkers present at varying disease stages and thus facilitate the development of more tailored treatments focusing on disease progression.
Innovations in Targets and Modifications Expected
The recombinant antibody sector will continue to grow and expand to include novel targets and modifications. With a deeper insight into genomic and proteomic changes in diseases, many new targets have emerged for which no antibody drugs are available. There is a considerable gap between target discovery and corresponding therapeutic antibody development. To address the pressing need for antibodies to be developed for these novel entities, recombinant antibodies enabling precise design, powerful engineering, and efficient production have a widening application in medicine.
Greater understanding of the design landscape, investigating different known and unknown opportunities, and identifying the best possible engineering steps required are critical to provide the optimal affinity, specificity, and other properties necessary for a given target or application. In this way, we expect the near future to include advances that further revolutionize the recombinant antibody universe, and antibody therapies will likely be available for targets that are unthinkable today.
The Role of Recombinant Antigens and Antibodies in the COVID-19 Pandemic Response
The COVID-19 pandemic represented a tragic time with respect to the loss of life around the world. It also, however, showed the public many positive aspects of the biopharma industry that are normally not apparent. Sino Biological remained very busy throughout the pandemic producing research reagents and providing contract research services for biopharma and diagnostic industries to help advance therapeutics, vaccines, and immunodiagnostic assays for the SARS-CoV-2 virus. The company has produced a comprehensive collection of recombinant antigens and antibodies for SARS-CoV-2 and supported scientists worldwide for their SARS-CoV-2 research, which led to over 2,000 publications to date.
In the race against time to fight the pandemic, Sino Biological has been extremely fast at developing reagents and implementing contract research services. For example, in January 2020, the company produced the key SARS-CoV-2 spike protein reagents within a record 11 days; then, in December 2021, it developed the Omicron RBD protein in a new record of six days. They were developed and manufactured using the company’s proprietary recombinant platforms. Since the COVID-19 outbreak, Sino Biological has been actively tracking the change of new variants to make sure products that are "up to date" and that its SARS-CoV-2 reagent portfolio fully covers the variants of interest (VOIs) and variants under monitoring (VUMs). Sino Biological has developed the world’s largest viral antigen bank, ProVir®, antibodies for almost all of these viral antigens, and even antibody pairs with high specificity and sensitivity, which have a significant impact on vaccine, therapeutic, and diagnostic research in areas like COVID-19, influenza, RSV, and many other fields of virology and immunology.
Tailoring Supply to Meet Client Needs
The biopharma industry is increasingly turning to contract research organizations (CROs) for custom antibody production to leverage their specialized expertise, advanced technologies, and established platforms and thus to achieve risk mitigation, cost reduction, and time saving. Recombinant technology provides greater possibility and flexibility to tailor production to precise needs, and the ever-increasing complexity and diversification of antibody-based biopharmaceuticals have further driven the outsourcing trend.
Typically, conversations begin with a discussion about the end application, followed by review of the target antigen and any specific requirements that will impact the design, engineering, and production of the desired antibody against the target. Ensuring the best-fit strategies depending on what the client is seeking is key to generate high-performing antibodies with desired properties for specific applications.
Sino Biological: Building Recombinant Antibody Expertise for Over 15 Years
At Sino Biological, recombinant technology has been not only leveraged from the outset to generate catalog protein and antibody products but also widely employed in the company’s contract development and manufacturing business. For both applications, there is a powerful drive to continually fine-tune and advance the company’s capabilities. Sino Biological has been highly involved in supporting COVID-19 therapy and vaccine developers and continues to provide custom services for novel therapy and diagnostic product developers.
A Plethora of Platforms
Sino Biological has comprehensive expression platforms in place to meet the diverse needs of customers, ranging from cell-based production platforms, such as mammalian cell and baculovirus–insect cell expression systems, to fast and efficient cell-free platforms.
Mammalian Cell Expression: For human research or clinical studies, producing recombinant proteins and antibodies from mammalian cells delivers a host of advantages. Mammalian cells allow for the manufacture of a protein or antibody that mimics nature, and the proper posttranslational modifications are executed on the molecule. Sino Biological’s optimized mammalian cell expression platforms utilize proprietary culture media, transfection reagents, expression vectors, supplements, and boosters. The company’s high-throughput platform can work on more than 1,000 projects at the same time from genes to recombinant antibodies for discovery and screening purposes — a customer can receive more than 1,000 different antibodies in just two weeks. Plus, Sino Biological can provide products on scales that range from micrograms to kilograms to make sure that customers worldwide have not only the quality and consistency of the product but also the quantity that they desire.
Cell-Free Synthesis: Cell-free systems allow rapid protein and antibody production in vitro without the need for living cells. Typical protein and antibody synthesis in cell-free systems takes only hours. Moreover, cell-free systems enable the production of difficult-to-express proteins and antibodies, and their open nature facilitates direct manipulation of the chemical environment and high-throughput potential. The cell-free platform developed by Sino Biological has proven itself with the successful production of proteins and antibodies that are difficult to express in other systems with shorter lead times, accelerating the research and development process of customers. For example, based on the company’s cell-free platform, the expression of antibody fragments, such as VHH and scFv, can be completed in three hours and purified antibodies can be achieved in one day with high purity and binding activity comparable to that of antibody fragments expressed in mammalian cells.
A Broad Range of Antibody Formats
Customers can benefit from Sino Biological’s many years of experience working not only with IgGs but also dimeric IgAs, multivalent IgMs (pentameric or hexameric), antibody fragments, and bispecifics.
Not Just IgGs: Antibody isotypes other than IgG have started to draw more attention in scientific research and drug development. IgM and IgA antibodies show higher avidity, lower T cell toxicity, and better accessibility to mucosal compartments compared with traditional IgG. Additionally, they can be used as new modalities of engineered antibodies. However, recombinant IgM and IgA production is more difficult due to low expression and less efficient purification. Thus, process optimization is of necessity for specific projects. Sino Biological can optimize the production of customers’ IgM and IgA antibodies, delivering products with high purity.
Antibody Fragments: Sino Biological has proven proficiency and has successfully completed numerous antibody fragment production projects. With multiple expression platforms, including HEK293, CHO, and cell-free systems, the company has thorough experience in the production and purification of diverse antibody fragments, including monovalent formats, such as Fab, scFv, and VHH, and bispecific constructs.
Bispecific Antibodies: Bispecifics are challenging to manufacture, owing to their high complexity. To facilitate the rapid discovery and development of bispecific therapeutics, Sino Biological provides fast and efficient bispecific antibody production service based on its proprietary mammalian cell expression platforms. Starting with antibody sequences, Sino Biological can deliver a wide range of bispecific antibody formats, such as BiTE, IgG(H)-scFv, Diabody, CrossMab, DVD-IgG, and DutaMab.
New U.S.-based Center for Bioprocessing
Headquartered in Beijing with subsidiaries in the United States, Europe, and Japan, Sino Biological has over 900 employees and serves researchers in academia and industry worldwide. In October 2023, the company announced the formal opening of its new Center for Bioprocessing (C4B) in Houston, Texas, which marks a significant milestone in Sino Biological’s global presence. The new center specializes in CRO services, including custom recombinant protein and recombinant antibody development and manufacture. The C4B represents Sino Biological’s natural global expansion of its CRO service capabilities and extends upon the company’s already strong CRO service offering at its Beijing headquarters. The team is committed to delivering high-quality, custom recombinant proteins and antibodies and looks forward to partnering with researchers and industry leaders worldwide to forge a brighter future in the life sciences.
Future Outlook
The future of recombinant antibodies is exciting. Growth in the cell, gene, and mRNA therapy markets will further boost the recombinant antibody sector, as these fields are intimately linked and will most likely merge eventually. There is, of course, always room for improvement. It is key to keep asking questions. Continuous inquiry leads to more information and increases our understanding of all aspects of recombinant antibody technology. At Sino Biological, we believe that this continual exploration will lead to compelling answers and ultimately novel technologies that facilitate the discovery, development, and production of novel recombinant antibodies that can change patient lives.
References
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- Wilkinson, Ian et al. “Fc-engineered antibodies with immune effector functions completely abolished.” PLoS One. 21 Dec. 2021.
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- Abd-Alrazag, Alaa et al. “Artificial Intelligence in the Fight Against COVID-19: Scoping Review.” Journal of Medical Internet Research. 15 Dec. 2020.
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