Nanobodies (Nbs) are heavy-chain-only antibodies derived from the variable region of camelids, with a molecular weight that is only about one-tenth that of heavy-chain antibodies. Nanobodies have strong penetrating ability into solid tumors, high affinity, superior physical and chemical properties, and are not easily denatured in extreme conditions. At the same time, nanobodies can quickly screen and verify antigens, which can speed up the development of new drugs. At present, it has gradually emerged in the development of antibody drugs. Nanobody-drug conjugates (NDCs) developed from nanobodies is a potential optimization direction for improving the efficacy of ADC. BOC Sciences has broad capabilities in the development of NDCs. We have expertise in the design, production and characterization of nanobodies and in conjugating these molecules with a variety of drugs to achieve targeted delivery and enhance therapeutic efficacy.
In terms of disease diagnosis and treatment, nanobodies have the advantages of easy penetration and rapid renal clearance. They can be labeled with fluorescent probes, enzyme tracers, biotin and other molecules as tracers. Combining nanobodies with molecular imaging techniques can optimize imaging systems and make them ideal for in vitro and in vivo imaging. In addition, due to the small molecular weight, strong penetrating power, high sensitivity and strong specificity of nanobodies, when they enter the body, they can efficiently penetrate cells to quickly capture antigens and neutralize viruses to achieve therapeutic purposes. Nanobodies have shown excellent application value and prospects in central nervous system diseases, circulatory system diseases, infectious diseases, tumors and inflammatory diseases. Based on the structural characteristics of nanobodies, the advantages of nanobodies are summarized as follows:
Fig. 1. Potential applications of nanobodies in bacterial therapeutics and diagnostics (Biochemical Pharmacology. 2023, 214: 115640).
In order to improve the efficiency of NDCs, scientists from BOC Sciences usually consider the key points of NDCs development from several factors, such as enhancing the specificity/affinity of Nbs, the selection of conjugated drugs, site-specific conjugation strategies, the location of drugs and the ratio of drugs to Nbs.
Currently, conjugated drugs used to prepare NDCs are mainly divided into DNA damaging agents and microtubule inhibitors. It is worth mentioning that BOC Sciences has been committed to providing a variety of DNA damaging agents and microtubule inhibitors for research and development purposes for many years. We have strong supply capabilities for these products, focusing on high quality and purity. In addition, our strong R&D team provides custom synthesis and manufacturing services for these products, allowing for tailor-made solutions based on specific research requirements.
Linker molecular design is a key factor affecting pharmacokinetics/pharmacodynamics. In order to maximize NDC efficiency, the ideal linker should have high stability in human plasma; be self-cleavable in tumor-specific environments; and use hydrophilic linkers to reduce NDCs aggregation. BOC Sciences can provide one-stop linker design and synthesis services for NDC development to ensure optimal conjugation and drug release. Our linkers undergo rigorous characterization and quality control processes to ensure linker quality and purity, providing researchers with reliable and consistent materials for NDC studies.
Compared with ADC, the simple chemical conjugation strategy of nanobodies and drugs has wider applicability and even surpasses ADC in terms of low production cost and long-term stability. For nanobodies, we generally support lysine conjugation, cysteine conjugation, aspartate conjugation, and glutamate conjugation as chemical conjugation sites to achieve a higher drug to nanobody ratio. In addition, with the progress of protein chemistry in recent years, we also provide homogeneous conjugation support services for drugs and nanobodies, including lysine amide conjugation, insertion of cysteine residues, unnatural amino acids conjugation and enzymatic conjugation.
Although theoretically NDC does not show any drug loading advantage over mAbs, the effective accumulation and stability of NDC at the tumor site is better than that of ADC. One study reported that despite the higher drug loading capacity of mAbs compared with Nbs, only 1.56% of ADCs were able to effectively enter the target site. However, the powerful properties of Nbs (high antigen specificity, stability, solubility, and lower immunogenicity) will make them more effective than mAbs in entering target cells. Based on this, BOC Sciences' drug-to-antibody ratio (DAR) and drug distribution analysis services can provide comprehensive support services for NDC. Our DAR services are tailored to meet the unique requirements of each project, ensuring an efficient and precise coupling process. The stability, specificity, and biological activity of the NDCs were thoroughly tested to ensure their suitability for further development and application in targeted drug delivery and therapy.
Using nanobodies to develop NDCs has many advantages over traditional ADCs in terms of production cost and specificity, and has a wide range of clinical application scenarios. The main advantages of nanobodies in ADC drugs are:
Fig. 2. Application of nanobody-drug conjugates in fungal treatment (Acta Biomaterialia. 2023, 69: 398-409).
Additionally, BOC Sciences has the ability to thoroughly characterize NDCs, including assessment of their binding affinity, stability, pharmacokinetics, and pharmacodynamics. This allowed us to optimize the conjugation process and ensure the development of efficient and selective NDCs. In addition, we have the ability to perform in vitro analysis and in vivo analysis to evaluate the efficacy and safety of NDCs. This includes cell-based assays, animal models, and pharmacokinetic studies to evaluate the therapeutic potential of NDCs. Overall, BOC Sciences' nanobody-drug conjugate development capabilities enable us to provide comprehensive support for the discovery and development of novel targeted therapeutics, improve efficacy and reduce off-target effects.