Chimeric vs. Humanized Antibodies

Antibody engineering and recombinant production have greatly impacted the research, biotechnology, and therapeutics fields. Recombinant DNA technology allows scientists to reformat antibodies into different isotypes, subtypes, species, formats, etc. and customize them to enhance their performance. A notable outcome of this technology is antibody humanization and chimerization, both of which have led to breakthroughs for therapeutic and in vitro antibodies. The terms “chimeric” and “humanized” antibody can be confusing and are sometimes used incorrectly by those not familiar with the engineering process. So, what is the difference between a chimeric and a humanized antibody and which one is better for your project? Let’s find out.


Figure 1. Progressive humanization of antibodies.
A schematic representation of the advancement from fully mouse antibodies, represented by red domains, to fully human antibodies, represented by blue domains. Note these images are somewhat misrepresentative, as immunoglobulin sequences are highly homologous across species, meaning a so-called fully mouse antibody is still relatively close in sequence to a fully human one.

What is a Chimeric Antibody?

Species switching, also called chimerization, involves reformatting an antibody’s variable regions to the antibody backbone of a different species, while maintaining the original specificity and affinity (Figure 1). Unlike humanization, the variable domain remains exactly the same, and only the constant domain is altered. Chimerization allows for the reformatting of an antibody into many different species, including human.

Chimeric Antibody Uses

Chimeric antibodies have grown in popularity for in vitro research due to their ability to increase compatibility with a secondary antibody and enable easier co-labeling studies. For diagnostic applications, chimeric antibodies reduce the risk of non-specific binding to heterophilic antibodies, such as human anti-mouse antibodies (HAMA), that can cause false positive assay results. Additionally, species switching prevents unwanted antibody interactions in serological assays, allows for the development of serological controls for human or veterinary use, and permits the standardization of Fc domains to streamline conjugation and immobilization protocols. Chimerization also enables the creation of a panel of antibodies from different species to increase options for multiplexing.

Species switched antibodies have been shown to be beneficial for in vivo research due to their ability to reduce immunogenicity. No neutralizing antibodies are induced in the host, meaning the antibody works for longer and cohorts respond more consistently.

What is a Humanized Antibody?

Antibody humanization is an engineering process that involves transferring critical non-human amino acids onto a human antibody framework (Figure 1). This primarily includes the grafting of amino acids in the complementarity-determining regions (CDRs) but also other framework amino acids critical for the variable heavy:variable light (VH:VL) interface and CDR orientation (1). In simplified terms, it is the process of taking important pieces of the variable region of a non-human antibody and putting them into a human antibody template. The newly humanized antibody should show comparable binding activity to the original antibody but be less immunogenic in vivo.

Humanized Antibody Uses

Humanized antibodies are synonymous with therapeutic applications. In 1997, Zenapax (daclizumab), an anti-CD25 antibody used to prevent organ transplant rejection, was the first humanized antibody to be approved by the FDA (2). To date there have been >70 humanized antibody therapeutics approved by the FDA (3), with 6 currently under review (4).

The majority of antibody humanization is for in vivo therapeutic applications, but humanized antibodies have also been utilized for in vitro purposes. For example, researchers in the UK sought to compare 16 different humanized antibody variants targeting Crimean-Congo hemorrhagic fever virus (CCHFV) and assess their function (5). In the US, scientists at the University of Southern California have described how they developed and validated two assays for determining susceptibility, or resistance, of Acinetobacter baumannii to four humanized anti-A. baumannii antibodies (6). Whether used in vivo or in vitro, humanized antibodies are pivotal to improving outcomes for human health.

Which to Choose?

Chimeric and humanized antibodies have significant differences when it comes to the engineering process, but occasionally their applications overlap. Humanized antibodies are most often used for in vivo therapeutic applications, but they can also be used for immunoassays. Chimeric antibodies are generally utilized for in vitro purposes but can be used in vivo for animal and human therapeutics. If you’re not certain which type of antibody is right for you, check out the flow chart below to help you get started on your antibody engineering journey.

*Please note that the flow chart is for entertainment purposes only and is not a replacement for expert scientific consultation.

Figure 2. Chimeric vs humanized flow chart for entertainment purposes only.

Custom Antibody Engineering Services

Antibody Humanization Service

Absolute Antibody offers antibody humanization for murine and non-murine species, including rabbit and single-domain camelid nanobodies. Our custom service is uniquely focused on delivering humanized antibodies with strong manufacturability, enabling the optimized large-scale production required for clinical use. We offer a royalty-free service with a guarantee that the humanized antibody will have comparable activity to the parent. Download our Manufacturability and Non-Murine Species humanization posters for more information.

Chimeric Antibody Service

Absolute Antibody has developed a proprietary cloning system that enables the rapid reformatting of antibodies. Our chimerization service provides the constant domains from a variety of different species, including pig, chicken, fish, platypus, and a range of non-human primates. Our team of expert scientists is always up for a challenge and would enjoy working with a new or unusual species.

Contact us to discuss your antibody needs and to get started on your next project.


  1. Cheetham, G.M., Hale, G., Waldmann, H., and Bloomer, A.C. (1998). Crystal structures of a rat antiCD52 (CAMPATH-1) therapeutic antibody Fab fragment and its humanized counterpart. J. Mol. Biol. 284, 85–99.
  2. Przepiorka D, Kernan NA, Ippoliti C, Papadopoulos EB, Giralt S, Khouri I, Lu JG, Gajewski J, Durett A, Cleary K, Champlin R, Andersson BS, Light S. Daclizumab, a humanized anti-interleukin-2 receptor alpha chain antibody, for treatment of acute graft-versus-host disease. Blood. 2000 Jan 1;95(1):83-9. PMID: 10607689.
  3. “FDA Industry Systems.” FDA FIS, Accessed 13 June 2024.
  4. The Antibody Society. Therapeutic monoclonal antibodies approved or in review in the EU or US. (June 13, 2024);
  5. Dowall, S. D., Graves, L. P., Kennedy, E., Graham, V. A., Alakeely, R. A., Chambers, A., … Hewson,R. (2023). Development of humanised antibodies for Crimean-Congo haemorrhagic fever virus: Comparison of hybridoma-based versus Phage Library Techniques. Journal of Immunological Methods, 512, 113405. doi:10.1016/j.jim.2022.113405.
  6. Matthew J. Slarve, … , Brian M. Luna, Brad Spellberg (2024). Clinical assays rapidly predict bacterial susceptibility to monoclonal antibody therapy. JCI Insight. 2024;9(2):e174799.

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