高尿酸血症是一种严重危害人类健康的多发病，可导致关节炎和肾病变的反复发作。尿酸氧化酶（UOX）能有效降低患者体内的尿酸水平，但存在着免疫原性强和半衰期短等缺点。聚乙二醇（PEG）修饰UOX可解决这些问题。然而，PEG化UOX易诱导产生抗PEG抗体，而且活性保持率低，影响了其临床应用。.本项目提出了一种分子机制，即抗PEG抗体的产生与UOX四聚体的解聚存在关联。通过生物药剂学、免疫学和生物物理学的研究可证明这一机制。在此基础上，使用四臂PEG制备分子内交联的UOX，可阻止UOX四聚体的解聚，避免暴露其内部的抗原表位；使用少量低分子量且不带甲氧基的PEG继续修饰交联的UOX，减少PEG抗原表位的种类和数量，从而降低其免疫原性；通过减少PEG对UOX活性中心的屏蔽作用，提高PEG化UOX的活性保持率。通过研究PEG化UOX在体内的稳定性和生物安全性，确定其在动物体内的长效机制和成药性。

Hyperuricemia is a kind of frequently-occurring disease that is seriously harmful to human health. Hyperuricemia usually leads to repeated seizure of arthritis and renal lesions. Urate oxidase (UOX) can effectively decrease the uric acid level of the patients. However, UOX suffers from the disadvantages of high immunogenicity and short half-life. Conjugation of polyethylene glycol (PEG) with UOX can solve these problems. However, the PEGylated UOX suffers from easy induction of anti-PEG antibody and low bioactivity retention，which limit its clinical application..The present project proposes a molecular mechanism, i.e., the production of anti-PEG antibody is related to the tetramer dissociation of UOX. This mechanism is demonstrated by biopharmaceutical, immunological and biophysical studies . Based on this mechanism, 4-arm PEG is used to intra-molecularly crosslink UOX, which can prevent the tetrameric dissociation of UOX and avoid the exposure of its interior antigenic epitopes. Afterwards, small amount of low molecular weight PEG without the methoxy group is used to modify the crosslinked UOX. The immunogenicity of the PEGylated UOX can be decreased by lowering the number and type of the antigenic epitopes of PEG. The bioactivity retention of the PEGylated UOX can be improved by decreasing the steric shielding effect of PEG on the bioactive domain of UOX. By studying the in vivo stability and biosafety of the PEGylated UOX, the long-acting mechanism and the druggability of the PEGylated UOX are determined.