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Many of the biotherapeutics suffer from a short half-life requiring frequent applications. The half-life extension strategies have become an essential part of a variety of biotherapeutics. A strategy utilizing fusion with an albumin-binding domain (ABD) has been investigated which is aimed at increasing pharmacokinetics. Moreover, fusing such domains to therapeutic proteins has been proved to achieve great success. Creative Biolabs has been committed to extending the half-life of drugs in various ways. We will choose the most appropriate method according to the characteristics of the drugs to help you carry out the project.

Introduction of ABD

The naturally occurring ABD with human serum albumin (HSA) binding property is a small, three-helical protein domain found in various surface proteins expressed by gram-positive bacteria. Three homologous HSA-binding domains are designated ABD1, ABD2, and ABD3, which have similar sequences. ABDs have been extensively studied as half-life extension modules and various derivatives with altered affinity for albumin have been developed. For example, the half-life can be significantly extended by combining an ABD to recombinant antibody fragments.

Fig.1 Schematic model of albumod technology. (Jussing, 2020)

Multiple Functions of ABD

Using an albumin-binding domain is similar to the approaches based on albumin-binding peptides. The utilizing complexation with naturally occurring albumin indicates that ABD fusion proteins exhibit a high affinity and can improve the pharmacokinetics of proteins. Combinatorial protein libraries have generated many new variants with desired binding characteristics. In addition, the half-life of a bispecific single-chain diabody was extended via genetic fusion to ABD3, indicating that ABD3 can act as a half-life extension fusion partner for peptides and proteins. Moreover, variants with improved affinity for HSA were designed and obtained. The consensus sequence design method was applied to construct an ABD3 variant, named ABDCon, based on the consensus sequence of the homologs to ABD3. It demonstrated that the higher binding affinity of ABDCon variants for HAS resulted in a longer half-life for the fusion partner. Phage display technology has also been used to select an ABD with a higher affinity for HSA. In addition, one variant denoted ABD035, has shown an extremely high affinity over the affinity of the original ABD3.

ABD Based Half-Life Extension Services

Among the half-life extension strategies, the ABD based method has gained increased interest. After years of intensive research, considerable evidence of ABD based molecule conjugation has accumulated and an advanced half-life service platform has been built. Based on our rich experience and advanced platform, Creative Biolabs provides a variety of services of ABD based conjugation. We can extend the half-life of peptide and protein drugs with ABD or small albumin-binding tags. In addition, many ABD3 variants for HAS such as ABDCon and ABD035 have been constructed in our half-life extension platform.

Altogether, these examples illustrate the versatility of the albumin-binding domain as a scaffold for protein engineering. If you are interested in our services, please contact us in time.

Reference

1. Jussing, E.; et al. [68 Ga] ABY-028: an albumin-binding domain (ABD) protein-based imaging tracer for positron emission tomography (PET) studies of altered vascular permeability and predictions of albumin-drug conjugate transport. EJNMMI research. 2020, 10(1): 1-18.