Improving protein pharmacokinetics by engineering erythrocyte affinity

Area of Science:

• Biotechnology
• Pharmacology
• Drug Delivery

Background:

• Poor pharmacokinetics, particularly short circulation half-life, hinder the clinical translation of novel protein therapeutics.
• Current strategies to improve protein half-life primarily rely on passive methods, such as increasing hydrodynamic radius.
• An active method for extending protein circulation time by targeting specific blood components is needed.

Purpose of the Study:

• To develop an active method for increasing the circulation half-life of proteins by enabling them to bind to erythrocytes.
• To identify and characterize a peptide that specifically binds to the erythrocyte surface.
• To evaluate the pharmacokinetic improvements of protein therapeutics engineered with erythrocyte-binding capabilities.

Main Methods:

• Screening a naive phage-displayed peptide library against mouse erythrocytes to identify erythrocyte-binding peptides.
• Characterizing the binding specificity and affinity of the identified peptide (ERY1) using flow cytometry and affinity experiments.
• Assessing the in vivo pharmacokinetics (half-life, clearance, bioavailability) of an erythrocyte-binding protein fusion in animal models.

Main Results:

• A 12-amino acid peptide (ERY1) was identified, showing high specificity for erythrocyte binding and negligible binding to leukocytes.
• ERY1-displaying phage exhibited significantly higher binding to mouse and rat erythrocytes compared to wild-type phage.
• Fusion proteins incorporating ERY1 demonstrated a 3.2- to 6.3-fold increase in circulation half-life, reduced clearance, and enhanced bioavailability.
• The ERY1 peptide did not induce an immune response, but it did not bind to human erythrocytes.

Conclusions:

• Engineering erythrocyte affinity into therapeutic proteins is an effective strategy to enhance their circulation half-life.
• This active targeting approach offers a viable solution to overcome pharmacokinetic limitations of protein drugs.
• The findings support the potential of erythrocyte-binding proteins for improving therapeutic efficacy and advancing drug development pipelines.