Bispecific monoclonal antibody
A bispecific monoclonal antibody (BsMAb, BsAb) is an artificial
Development history
The original concept of BsAbs was proposed by Nisonoff and his collaborators in the 1960s, including the first idea of antibody architecture and other findings.
Structural types and manufacturing methods
There are many formats of BsAbs, but the two main categories are IgG-like and non-IgG-like.[3] The main types of manufacturing methods are quadromas, chemical conjugation, and genetic recombination, and each method results in a unique format.[3][10]
IgG-like
This format retains the traditional
However, the quadroma method relies on random chance to form usable BsAb, and can be inefficient. Another method for manufacturing IgG-like BsAb is called "knobs into holes," and relies on introducing a mutation for a large amino acid in the heavy chain from one mAb, and a mutation for a small amino acid in the other mAb's heavy chain. This allows the target heavy chains (and their corresponding light chains) to fit together better, and makes the production of BsAbs more reliable.[3][10]
Non-IgG-like
There are other BsAbs that lack an Fc region entirely, and thus leads to relatively simple design strategies.
Despite the considerable differences between the various types and formats of bispecific antibodies, their manufacturing processes correspond in several steps:
- Genetic engineering and cloning – Different monoclonal antibodies or antibody fragments are fused. Recombinant DNA technology is applied to generate one single, bispecific antibody.
- Preparation of expression system – An expression system is chosen and prepared for antibody expression. Frequently used expression systems for therapeutic bispecific antibodies are mammalian cells, such as CHO cells, as they are effective in performing complex post-translational modifications.
- Transfection and protein production – Either via stable or transient transfection, genetic information of the desired bispecific antibodies is inserted into the expression system, which consequently expresses the proteins accordingly.
- Protein purification – Steps to isolate and enrich bispecific antibodies are taken. This can include several purification processes, such as protein A affinity chromatography or peptide tagging.
- Antibody characterization – Characterization and quality control conclude the production process. Effector functions, stability and binding specificity are examined at this stage.[20]
Mechanism of action
Recruiting and activating of immune cells
The binding of a BsAb to its target antigens can lead to a variety of effects. The most widely used application of this approach is in
Interfering with receptor signaling and inactivating signaling ligands
The growth of tumor cells can be simulated or modulated by receptor tyrosine kinase (RTKs), including members of the Her family or insulin-like growth factor (IGF). The RTKs are therefore preferred targets in cancer therapy. Although monospecific RTK-targeting IgGs have already been available in the market, such as cetuximab (Erbitux) and panitumumab (Vectibix), both of which are directed against HER1. However, cancer cells can switch to a different pathway to escape the growth inhibition generated by blocking one signaling pathway. To improve the therapeutic efficacy, simultaneously interfering/blocking of two (or more) RTK signaling pathways, achieved through the mediation of BsAb to inactivate either the RTKs or their ligand, reduces the possibility of the escape mechanisms adopted by the tumor cells.[21][22]
In addition, in working with Ebolavirus vaccines, a study has shown that a DVD-Ig antibody can be used to prevent viral escape from the endosome. Ebolaviruses infect cells by receptor-mediated endocytosis. Researchers developed DVD-Igs where the outer variable regions bind to the surface glycoproteins of the viral coat and enter the cell with the virus. These outer regions are cleaved in the viral endosome, revealing the inner variable regions that then bind to both the virus and internal receptors in the endosome. Blocking the interaction between the virus and endosomal proteins prevents viral escape from the endosome and further infection.[23]
Forcing association of protein complexes
As an example, emicizumab (formerly RG6013) is an IgG derivative containing H-chain heterodimerization motifs, which was combined with the common light chain approach to prevent L-chain mispairing issues.[24][25] With a bivalent composition, emicizumab brings two protein antigens together into one complex. Factor IXa and Factor X in the coagulation cascade are the cognate antigens which are bound by RG6013. These two factors are brought together by coagulation factor VIIIa in a healthy individual, while patients with bleeding disorder hemophilia A do not have VIIIa. Current treatment of this disorder is to supplement the patients with FVIII to reduce bleeding complications. But FVIII can be recognized as a foreign protein in these patients due to the absence of this protein and thus an immune response will be generated against this protein. Besides, FVIII has a short half-life (less than 15 hours) and thus is cleared rapidly. However, the humanized BsAb has lower immunogenicity and long serum half-life compared with FVIII and thus provide a better treatment for hemophilia.[2]
Advantages over ordinary monoclonal antibodies
Additionally, targeting more than one molecule can be useful to circumvent the regulation of parallel pathways and avoid resistance to the treatment. Binding or blocking multiple targets in a pathway can be beneficial to stopping disease, as most conditions have complicated multifaceted effects throughout the body.[28] Together with combination therapies, BsAbs are being used more and more to treat certain types of cancers, as, over time, some tumors develop resistances to checkpoint inhibitors and/or co-stimulatory molecules.[29]
Current Scenario of bsAb drugs
Currently, nine bsAb drugs have been approved by the US FDA / EMA and over 180 are currently in clinical trials. The first bispecific antibody to gain regulatory approval, blinatumomab, targets CD19 on B cells and CD3 on T cells, leading to the activation of T cells and the destruction of B cells.[30] A total of eight more bispecific antibody drugs have since been approved by the US FDA: blinatumomab, emacizumab, amivantamab, tebentafusp, faricimab, teclistamab, mosunetuzumab, epcoritamab, glofitamab.[31] Among the bsAb programs currently under development, the combination of CD3 and tumor surface targets are the most popular targets pairs. Other popular targets are CD3, HER2, PD-1, PD-L1, EGFR, CTLA-4, etc., which as well as immune targets of PD-1, PD-L1, BCMA, CD47, CTLA-4, LAG-3, 4 -1BB.[32] Additionally, with the approval of the several new bsAb since 2022, and new mechanisms for improving efficacy like development of hetero-dimer bispecific molecules, several additional possibilities of target pairs have emerged.[32]
Problems and current disadvantages
IgG-like antibodies can be immunogenic, which means the Fc region could cause detrimental downstream immune responses caused by cells that are activated by Fc receptors.[3] The therapeutic use of BsAbs as a whole is still largely in development, with many clinical trials currently ongoing that are determining the efficacy and safety of BsAbs for treatment.[14]
Applications
Bispecific antibodies have a wide variety of applications in diagnosis and therapy. BsAbs can be combined with HRPO, can be used in pre-targeting strategies, and can be used to provide better imaging for early detection in diagnosis. To treat cancer, BsAbs can target immune cells precisely, help and reactive the immune cells, fine-tune the fate and function of immune cells, improve the tolerance of immune cells, and promote the return to immune homeostasis. BsAbs can also be applied to treat other diseases, including hemophilia A, diabetes, Alzeimer's disease, and ophthalmological diseases.[1]
BsAbs on the market
Three bispecific antibodies are presently in clinical use.
References
This article incorporates
- ^ PMID 34025638.
- ^ PMID 25728220.
- ^ PMID 26692321.
- S2CID 19267292.(subscription required)
- PMID 13729244.(subscription required)
- S2CID 4161444.(subscription required)
- S2CID 4264730.(subscription required)
- PMID 3045807.
- S2CID 41622760.(subscription required)
- ^ PMID 28184223.
- ^ S2CID 27797190.
- ^ PMID 20073127.
- ^ S2CID 34289723.
- ^ PMID 28036020.
- ^ PMID 19509221.
- PMID 20150180.
- PMID 10512714.
- PMID 25875246.
- PMID 29213270.
- ^ Schofield, Desmond (August 3, 2023). "Bispecific antibody production – a comprehensive overview". Retrieved December 11, 2023.
- S2CID 4235503.
- PMID 3798106.
- ^ PMID 27608667.
- S2CID 13125020.
- PMID 23468998.
- ^ S2CID 22628198.
- S2CID 30441206.
- PMID 26187740.
- PMID 32344837.
- ^ Research, Center for Drug Evaluation and (2023-08-02). "Bispecific Antibodies: An Area of Research and Clinical Applications". FDA.
- ^ Research, Center for Drug Evaluation and (2023-08-02). "Bispecific Antibodies: An Area of Research and Clinical Applications". FDA.
- ^ a b krishgen2023 (2023-03-24). "Popular Targets for Bispecific Antibody Drugs". Krishgen Biosystems. Retrieved 2023-09-16.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - PMID 31028837.
- ^ "Removab: Withdrawal of the marketing authorisation in the European Union" (PDF). European Medicines Agency. 2017-07-10.
- S2CID 235334950.
External links
- Bispecific monoclonal antibody entry in the public domain NCI Dictionary of Cancer Terms
- Bispecific+antibodies at the U.S. National Library of Medicine Medical Subject Headings (MeSH)