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

Abstract 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.