Nanourchin‐like Uricase‐Poly( _L ‐proline) Conjugate with Retained Enzymatic Activity, Mitigated Immunogenicity, and Sustained Efficacy Upon Repeated Administrations

The poor half-life and strong immunogenicity of proteins such as uricase (UOx), a therapeutic enzyme for chronic refractory gout and hyperuricemia, are pressing clinical challenges. Although conjugation of poly(ethylene glycol) (PEGylation) of UOx can improve the pharmacokinetics, preexisting or induced anti-PEG antibodies, which lead to accelerate blood clearance (ABC) and reduced response rate, have been a major clinical hurdle. Herein, we report the facile "grafting-from" preparation of a nanourchin-like uricase-poly(_L-proline) conjugate, namely UOx-PLP, with high grafting-density, enhanced thermal, lyophilization, freeze-thaw, and proteolytic stability. Through a transient preblocking strategy in the synthesis, the UOx-PLP overcomes activity loss and retains ~82 % enzyme activity. In Sprague-Dawley rats, UOx-PLP stimulates minimum complement activation and anti-UOx antibodies. Unlike PEG-UOx gave a significantly reduced half-life after repetitive administrations, UOx-PLP shows no sign of ABC effect. Moreover, the half-life of UOx-PLP remain almost unchanged when cross-administrated to rats previously received PEG-UOx and with high titers of anti-UOx antibodies. Finally, UOx-PLP shows minimum loss of efficacy after five straight administrations in a UOx knock-out hyperuricemia mice model, whereas PEG-UOx experiences sharp loss of efficacy upon the same treatment. Overall, the simple preparation and outstanding nonclinical results highlight the enormous potential of UOx-PLP for future clinical translation.