Delivery System Based on Fc Fusion Protein

Fc-fusions are now a well-established class of therapeutics. Its precise targeting of effector systems has been characterized and successfully applied in the drug delivery system. With over a decade of experience, Creative Biolabs is dedicated for the development of new therapeutic agent delivery and we offer our clients high-quality services. Now we provide a full range of targeted delivery services based on Fc fusion protein. Our tailored solutions and advanced platforms will promote your novel therapeutic drug research.

Fc Fusion Protein

Fc-based fusion proteins consist of an immunoglobin Fc domain that is directly conjugated to another peptide or other proteinaceous molecules such as a ligand, a peptidic antigen (Ag) or a ‘bait’ protein. The fused partners are linked to an Fc-domain having significant therapeutic potential with a number of additional beneficial biological and pharmacological properties. Most importantly, the fusion of the Fc domain significantly increases their plasma half-life, prolongs therapeutic activity. Besides, the presence of the Fc domain endows these molecules to interact with Fc-receptors (FcRs) located on immune cells, which is particularly important for their use in oncological therapies and vaccines. In addition, the Fc domain also can improve the solubility and stability of the partner molecule both in vitro and in vivo. Generally, most Fc-fusions are expressed as homodimers, and can also be modified to polymerize into well-defined complexes that can increase the avidity and potency.

Fig.1 Different capabilities for different Fc‐fusion stoichiometries.¹

Delivery System Based on Fc Fusion Protein

Many native peptides and proteins are potent agonists representing a rich source of therapeutic potentials, such as the GLP-1-analog peptide drug Exanatide. However, many peptides have low binding affinity and a very short half-life attributing to rapid renal clearance and proteolytic degradation in the blood, kidney, or liver. In particular, they are typically cleared from the bloodstream within minutes after administration. Thus, many strategies have been established to extend stability and improve pharmacokinetic (PK) properties of administrated peptide drugs. One of these approaches is to graft peptides to the Fc region of an immunoglobulin G (IgG), thereby hijacking the FcRn recycling process that provides a long circulating half-life to the fusion protein. Currently, the Fc fusion is one of the most advanced and successful methods used in delivery system. To date, seven peptides-Fc-fusion drugs have been developed and approved for clinical use, and many more targeting various diseases are in the pipeline. For example, Romiplostim is the first peptide-Fc-fusion drug approved for the treatment of immune thrombocytopenic purpura. AMG 386 is currently under evaluation in Phase 3 clinical trials in combination with chemotherapy in women with ovarian cancer. AMG 819 targeting nerve growth factor for pain has also progressed to clinical trials.

Fig.2 The structure of a prototypic IgG Fc-fusion and the means by which it can be presently modified.¹

The Fc fragment usually contains the hinge region, CH2 and CH3 domains of immunoglobulin heavy chain. For therapeutic purposes, most Fc-fusion proteins employ the Fc fragment of human IgG1. All seven currently marketed Fc-fusion proteins contain IgG1 Fc, while Fc fragments of human IgG2 and IgG4 have also been explored actively. Generally, the Fc domain is conjugated at the C-terminus of the effector proteins. In some cases, a small spacer (such as a glycine- and serine-rich peptide) between Fc and the effector protein is useful in preserving the function of the effector protein. The expression of dimeric Fc-fusion proteins requires one expression cassette for the effector protein-Fc fusion. In contrast, the expression of monomeric Fc-fusion proteins usually needs two expression cassettes, and one controls the expression of the effector protein coupled with Fc and the other controls expression of Fc alone. The two expression cassettes can be built within one bi-cistronic vector, or in two separate vectors.

Creative Biolabs is an expert who provides Fc fusion protein-based targeted delivery development services. Our professional scientist team is committed to the field of therapeutic drug research and development and successfully contributed a number of services specifically tailored to antibody-related services including Fc fusion protein construction. We are confident in applying our experience to design actual strategic packages pertinent to customers’ projects. For more information and a detailed quote please contact us.

Reference

1. Czajkowsky, Daniel M., et al. "Fc‐fusion proteins: new developments and future perspectives." EMBO molecular medicine 4.10 (2012): 1015-1028.

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