A Trivalent Enzymatic System for Uricolytic Therapy of HPRT Deficiency and Lesch-Nyhan Disease

Luca Ronda,Riccardo Percudani,Romina Corsini,Anastasia Liuzzi,Stefano Bettati,Riccardo Piano,Marialaura Marchetti

doi:10.1007/s11095-017-2167-6

Abstract

PurposeBecause of the evolutionary loss of the uricolytic pathway, humans accumulate poorly soluble urate as the final product of purine catabolism. Restoration of uricolysis through enzyme therapy is a promising treatment for severe hyperuricemia caused by deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT). To this end, we studied the effect of PEG conjugation on the activity and stability of the enzymatic complement required for conversion of urate into the more soluble (S)-allantoin.MethodsWe produced in recombinant form three zebrafish enzymes required in the uricolytic pathway. We carried out a systematic study of the effect of PEGylation on the function and stability of the three enzymes by varying PEG length, chemistry and degree of conjugation. We assayed in vitro the uricolytic activity of the PEGylated enzymatic triad.ResultsWe defined conditions that allow PEGylated enzymes to retain native-like enzymatic activity even after lyophilization or prolonged storage. A combination of the three enzymes in an appropriate ratio allowed efficient conversion of urate to (S)-allantoin with no accumulation of intermediate metabolites.ConclusionsPharmaceutical restoration of the uricolytic pathway is a viable approach for the treatment of severe hyperuricemia.

Highlights

Different from hominoids, most mammals do not show gout or urate kidney stones formation as they are able to convert the uric acid to its much more soluble metabolite (S)-allantoin
Pharmaceutical restoration of the uricolytic pathway is a viable approach for the treatment of severe hyperuricemia
We recently proposed that the treatment of severe early onset hyperuricemia, as observed in hereditary hypoxanthine-guanine phosphoribosyltransferase (HPRT)deficiency and Lesch-Nyhan disease (LND), could be approached by facilitating rather than blocking the purine degradation pathway

Summary

Introduction

Different from hominoids, most mammals do not show gout or urate kidney stones formation as they are able to convert the uric acid to its much more soluble metabolite (S)-allantoin. It has been recently reported that urate oxidase (uricase, Uox) is not the unique enzyme involved in this process [1,2,3]. Excess of serum urate (hyperuricemia) increases the risk of gout and metabolic comorbidities such as obesity, hypertension, and diabetes [4,5,6]. The current pharmacological approaches to hyperuricemia-related diseases exploit competitive inhibitors of xanthine oxidase (e.g. allopurinol and febuxostat), inhibitors of the renal urate transporters (e.g. probenecid), or the intravenous administration of recombinant Uox. Two different formulations of the latter have been approved for human use in US and Europe: Rasburicase (Elitek®, Sanofi-Aventis, for the prevention and treatment of tumor lysis syndrome) [7] and Pegloticase (Krystexxa®, Savient Pharmaceuticals, for treatment-refractory, chronic gout) [8,9]

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