Journal Article

Tuning the serum persistence of human serum albumin domain III:diabody fusion proteins

Vania E. Kenanova, Tove Olafsen, Felix B. Salazar, Lawrence E. Williams, Scott Knowles and Anna M. Wu

in Protein Engineering, Design and Selection

Volume 23, issue 10, pages 789-798
Published in print October 2010 | ISSN: 1741-0126
Published online August 2010 | e-ISSN: 1741-0134 | DOI:
Tuning the serum persistence of human serum albumin domain III:diabody fusion proteins

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The long circulation persistence of human serum albumin (HSA) is enabled by its domain III (DIII) interaction with the neonatal Fc receptor (FcRn). A protein scaffold based on HSA DIII was designed. To modify the serum half life of the scaffold, residues H535, H510, and H464 were individually mutated to alanine. HSA DIII wild type (WT) and variants were fused to the anti-carcinoembryonic antigen (CEA) T84.66 diabody (Db), radiolabeled with 124I and injected into xenografted athymic mice for serial PET/CT imaging. All proteins targeted the CEA-positive tumor. The mean residence times (MRT) of the proteins, calculated by quantifying blood activity from the PET images, were: Db-DIII WT (56.7 h), H535A (25 h), H510A (20 h), H464A (17 h), compared with Db (2.9 h). Biodistribution confirmed the order of blood clearance from slow to fast: Db-DIII WT > H535A > H510A > H464A > Db with 4.0, 2.0, 1.8, 1.6 and 0.08 %ID/g of remaining blood activity at 51 h, respectively. This study demonstrates that attenuating the DIII–FcRn interaction provides a way of controlling the pharmacokinetics of the entire Db-DIII fusion protein without compromising tumor targeting. H464 appears to be most crucial for FcRn binding (greatest reduction in MRT), followed by H510 and H535. By mutating the DIII scaffold, we can dial serum kinetics for imaging or therapy applications.

Keywords: blood clearance; FcRn; HSA DIII; PET imaging; protein scaffold

Journal Article.  7019 words.  Illustrated.

Subjects: Proteins

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