A Therapeutic Uricase with Reduced Immunogenicity Risk and Improved Development Properties

PLoS One. 2016 Dec 21;11(12):e0167935. doi: 10.1371/journal.pone.0167935. eCollection 2016.


Humans and higher primates are unique in that they lack uricase, the enzyme capable of oxidizing uric acid. As a consequence of this enzyme deficiency, humans have high serum uric acid levels. In some people, uric acid levels rise above the solubility limit resulting in crystallization in joints, acute inflammation in response to those crystals causes severe pain; a condition known as gout. Treatment for severe gout includes injection of non-human uricase to reduce serum uric acid levels. Krystexxa® is a hyper-PEGylated pig-baboon chimeric uricase indicated for chronic refractory gout that induces an immunogenic response in 91% of treated patients, including infusion reactions (26%) and anaphylaxis (6.5%). These properties limit its use and effectiveness. An innovative approach has been used to develop a therapeutic uricase with improved properties such as: soluble expression, neutral pH solubility, high E. coli expression level, thermal stability, and excellent activity. More than 200 diverse uricase sequences were aligned to guide protein engineering and reduce putative sequence liabilities. A single uricase lead candidate was identified, which showed low potential for immunogenicity in >200 human donor samples selected to represent diverse HLA haplotypes. Cysteines were engineered into the lead sequence for site specific PEGylation and studies demonstrated >95% PEGylation efficiency. PEGylated uricase retains enzymatic activity in vitro at neutral pH, in human serum and in vivo (rats and canines) and has an extended half-life. In canines, an 85% reduction in serum uric acid levels was observed with a single subcutaneous injection. This PEGylated, non-immunogenic uricase has the potential to provide meaningful benefits to patients with gout.

MeSH terms

  • Animals
  • Calorimetry, Differential Scanning
  • Dogs
  • Escherichia coli / metabolism
  • Gout / drug therapy*
  • Half-Life
  • Humans
  • Hydrogen-Ion Concentration
  • Kinetics
  • Papio
  • Polyethylene Glycols / chemistry
  • Rats
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / immunology
  • Recombinant Proteins / pharmacokinetics
  • Recombinant Proteins / therapeutic use
  • Substrate Specificity
  • Swine
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism
  • Urate Oxidase / adverse effects
  • Urate Oxidase / immunology
  • Urate Oxidase / therapeutic use*


  • Recombinant Proteins
  • Polyethylene Glycols
  • Urate Oxidase

Grants and funding

The funder provided support in the form of salaries for authors (MedImmune LLC – ACN CW AZ, BC, LG, JG, RB, MW, FB, EO, FG, VI, HF, VR, MB, SN, CYW, SW, LJ, HW, SC, and MB; MedImmune LTD – DAO and JO; Ardea – JNM, DMW, DZ, and CW), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.