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Antibody biopolymer conjugate (ABC) refers to the product of coupling monoclonal antibodies with biopolymers by using molecular engineering. At this stage, the development of ABC is mainly to couple antibodies with phosphatidylcholine biopolymers. Phosphatidylcholine biopolymer can effectively simulate some natural properties of cell membrane, showing good biocompatibility. Biopolymers consist of monomeric units that are covalently bonded to form larger molecules. Biopolymers are divided into three main groups: polynucleotides (DNA, RNA or oligonucleotide), polypeptides and polysaccharides. Biopolymers are natural polymers produced by organisms. In other words, they are polymeric biomolecules derived from cells or extracellular substances. Biopolymers are widely used in tissue engineering, medical devices and pharmaceutical industries. Therefore, ABC has high biocompatibility and biodegradability.
ABC is intended to be the following characteristics:
Fig. 1 The structure of antibody-biopolymer conjugate (Chandrasekaran, 2021)
KSI-301 is an ABC targeting VEGF, which is composed of all human VEGF monoclonal antibodies and optically transparent and branched phosphatidylcholine biopolymers coupled by stable and site-specific chemical bonds. The structure of KSI-301 is shown in the figure 1. The molecular weight of KSI-301 is about 950 kda, of which the antibody is about 150 kda and the phosphatidylcholine biopolymer is about 800 kda. KSI-301 will greatly prolong the intraocular half-life of drugs and reduce the frequency of administration which may become a highly differentiated first-line treatment for retinal vascular diseases. At present, this ABC is being studied for the treatment of wet age-related macular degeneration (Wamd), diabetes macular edema (DME), retinal vein occlusion (RVO), and diabetes retinopathy (DR). KSI-501 is an ABC targeting IL-6 / VEGF. It is coupled with phosphatidylcholine biopolymer by trap antibody fusion (TAF) targeting IL-6/VEGF, aiming to inhibit abnormal angiogenesis and concurrent inflammation in retinal vascular diseases. Preclinical structural and functional studies have shown that the TAF protein can be specifically combined with IL-6 / VEGF targets. The drug may provide more superior treatment options for patients with retinal vascular diseases, especially those with high levels of inflammation, such as DME, and ocular inflammatory diseases, such as uveitis.
By embedding and attaching small molecule drugs into phosphatidylcholine biopolymers, this kind of ABC has the characteristics of high bio-compatibility and high drug loading, and can achieve sustained-release. Coupled with bispecific antibodies, it constitutes a new drug form, which can participate in the regulation of a variety of intracellular and extracellular disease-related pathways. ABC structures water at critical binding interfaces to make it lasts longer in the target location and improves its therapeutic benefit.