Urate-lowering therapy, serum urate, inflammatory biomarkers, and renal function in patients with gout following pegloticase discontinuation.

BACKGROUND/PURPOSE: Little is known about long-term clinical outcomes or urate-lowering (ULT) therapy use following pegloticase discontinuation. We examined ULT use, serum urate (SU), inflammatory biomarkers, and renal function following pegloticase discontinuation. METHODS: We conducted a retrospective analysis of gout patients who discontinued pegloticase using the Rheumatology Informatics System for Effectiveness (RISE) registry from 1/2016 to 6/2022. We defined discontinuation as a gap ≥ 12 weeks after last infusion. We examined outcomes beginning two weeks after last dose and identified ULT therapy following pegloticase discontinuation. We evaluated changes in lab values (SU, eGFR, CRP and ESR), comparing on- treatment (≤ 15 days of the second pegloticase dose) to post-treatment. RESULTS: Of the 375 gout patients discontinuing pegloticase, median (IQR) laboratory changes following discontinuation were: SU: +2.4 mg/dL (0.0,6.3); eGFR: -1.9 mL/min (- 8.7,3.7); CRP: -0.8 mg/L (-12.8,0.0); and ESR: -4.0 mm/hr (-13.0,0.0). Therapy post-discontinuation included oral ULTs (86.0%), restarting pegloticase (4.5%), and no documentation of ULT (9.5%), excluding patients with multiple same-day prescriptions (n = 17). Oral ULTs following pegloticase were: 62.7% allopurinol, 34.1% febuxostat. The median (IQR) time to starting/restarting ULT was 92.0 days (55.0,173.0). Following ULT prescribing (≥ 30 days), only 51.0% of patients had SU < 6 mg/dL. Patients restarting pegloticase achieved a median SU of 0.9 mg/dL (IQR:0.2,9.7) and 58.3% had an SU < 6 mg/dL. CONCLUSION: Pegloticase treats uncontrolled gout in patients with failed response to xanthine oxidase inhibitors, but among patients who discontinue, optimal treatment is unclear. Based on this analysis, only half of those starting another ULT achieved target SU. Close follow-up is needed to optimize outcomes after pegloticase discontinuation.

Photosensitized covalent organic framework as a light-induced oxidase mimic for colorimetric detection of uric acid.

As large numbers of people are suffering from gout, an accurate, rapid, and sensitive method for the detection of gout biomarker, uric acid, is important for its effective control, diagnosis, and therapy. Although colorimetric detection methods based on uricase have been considered, they still have limitations as they produce toxic H2O2 and are expensive and not stable. Here, a novel uricase-free colorimetric method was developed for the sensitive and selective detection of uric acid based on the light-induced oxidase-mimicking activity of a new photosensitized covalent organic framework (COF) (2,4,6-trimethylpyridine-3,5-dicarbonitrile-4-[2-(4-formylphenyl)ethynyl]benzaldehyde COF [DCTP-EDA COF]). DCTP-EDA COF has a strong ability to harvest visible light, and it could catalyze the oxidation of 1,4-dioxane, 3,3',5,5'-tetramethylbenzidine under visible light irradiation to produce obvious color changes. With the addition of uric acid, however, the significant inhibition of the oxidase-mimicking activity of DCTP-EDA COF remarkably faded the color, and thus uric acid could be colorimetrically detected in the range of 2.0-150 µM with a limit of detection of 0.62 µM (3σ/K). Moreover, the present colorimetric method exhibited high selectivity; uric acid level in serum samples was successfully determined, and the recoveries ranged from 96.5% to 105.64%, suggesting the high accuracy of the present colorimetric method, which demonstrates great promise in clinical analysis.

Intensive urate-lowering with pegloticase plus methotrexate co-therapy in uncontrolled gout patients with and without chronic kidney disease: A retrospective case series.

Chronic kidney disease (CKD) and gout commonly co-occur. Pegloticase lowers serum urate (SU) in uncontrolled gout patients but antidrug antibodies limit urate-lowering response and increase infusion reaction (IR) risk. Methotrexate (MTX) co-administration increases pegloticase response rate and mitigates IR risk but CKD limits MTX use. This pooled case series examined pegloticase + MTX co-therapy in uncontrolled gout patients with and without CKD. Cases of pegloticase + MTX co-therapy in existing datasets were retrospectively examined. Baseline eGFR classified patients as CKD (eGFR < 60 mL/min/1.73 m2) or non-CKD (eGFR ≥ 60 mL/min/1.73 m2). Patient characteristics, treatment parameters, laboratory values, urate-lowering response rate (≥12 pegloticase infusions received and SU < 6 mg/dL just before infusion 12), and AEs were examined. Fifteen CKD (eGFR: 43.2 ±â€…11.3 mL/min/1.73 m2; SU: 8.6 ±â€…2.2 mg/dL), 27 non-CKD (eGFR: 82.9 ±â€…19.0 mL/min/1.73 m2; SU: 9.5 ±â€…1.7 mg/dL) patients were included. Comorbidity profiles were similar, but CKD patients were older (72.0 ±â€…9.9 vs 52.3 ±â€…14.3 years) and more often female (33.3% vs 7.4%). Treatment parameters were similar with 4-week MTX Run-in followed by mean of 14.7 ±â€…8.1 [CKD] vs 14.1 ±â€…7.1 [non-CKD] pegloticase infusions. However, CKD patients had lower MTX dose (14.8 ±â€…5.8 vs 19.3 ±â€…4.9 mg/week). Urate-lowering response was similar (92% vs 86%). eGFR increased during treatment in 60% of CKD (+11.5 ±â€…20.9 mL/min/1.73 m2, 87% stable/improved CKD-stage) and 44% of non-CKD (+4.2 ±â€…15.0 mL/min/1.73 m2) patients. AEs were similar (≥1 AE CKD: 53%, non-CKD: 67%; gout flare most-reported). One case each of pancytopenia and IR (mild) occurred in non-CKD patients. These real-world data show similar pegloticase + MTX efficacy in CKD and non-CKD patients. No new safety signals were identified, with most CKD patients showing renal function stability or improvement during therapy.

Treatment with Rasburicase in Hospitalized Patients with Cardiorenal Syndrome: Old Treatment, New Scenario.

Cardiorenal syndrome (CRS) involves joint dysfunction of the heart and kidney. Acute forms share biochemical alterations like hyperuricaemia (HU) with tumour lysis syndrome (TLS). The mainstay treatment of acute CRS with systemic overload is diuretics, but rasburicase is used in TLS to prevent and treat hyperuricaemia. An observational, retrospective study was performed to assess the effectiveness and safety of a single dose of rasburicase in hospitalized patients with cardiorenal syndrome, worsening renal function and uric acid levels above 9 mg/dL. Rasburicase improved diuresis and systemic congestion in the 35 patients included. A total of 86% of patients did not need to undergo RRT, and early withdrawal was possible in the remaining five. Creatinine (Cr) decreased after treatment with rasburicase from a peak of 3.6 ± 1.27 to 1.79 ± 0.83 mg/dL, and the estimated glomerular filtration rate (eGFR) improved from 17 ± 8 to 41 ± 20 mL/min/1.73 m2 (p = 0.0001). The levels of N-terminal type B Brain Natriuretic Peptide (Nt-ProBNP) and C-reactive protein (CRP) were also significantly reduced. No relevant adverse events were detected. Our results show that early treatment with a dose of rasburicase in patients with CRS and severe HU is effective to improve renal function and systemic congestion, avoiding the need for sustained extrarenal clearance, regardless of comorbidities and ventricular function.

Flow-Through Amperometric Biosensor System Based on Functionalized Aryl Derivative of Phenothiazine and PAMAM-Calix-Dendrimers for the Determination of Uric Acid.

A flow-through biosensor system for the determination of uric acid was developed on the platform of flow-through electrochemical cell manufactured by 3D printing from poly(lactic acid) and equipped with a modified screen-printed graphite electrode (SPE). Uricase was immobilized to the inner surface of a replaceable reactor chamber. Its working volume was reduced to 10 µL against a previously reported similar cell. SPE was modified independently of the enzyme reactor with carbon black, pillar[5]arene, poly(amidoamine) dendrimers based on the p-tert-butylthiacalix[4]arene (PAMAM-calix-dendrimers) platform and electropolymerized 3,7-bis(4-aminophenylamino) phenothiazin-5-ium chloride. Introduction of the PAMAM-calix-dendrimers into the electrode coating led to a fivefold increase in the redox currents of the electroactive polymer. It was found that higher generations of the PAMAM-calix-dendrimers led to a greater increase in the currents measured. Coatings consisted of products of the electropolymerization of the phenothiazine with implemented pillar[5]arene and PAMAM-calix-dendrimers showing high efficiency in the electrochemical reduction of hydrogen peroxide that was formed in the enzymatic oxidation of uric acid. The presence of PAMAM-calix-dendrimer G2 in the coating increased the redox signal related to the uric acid assay by more than 1.5 times. The biosensor system was successfully applied for the enzymatic determination of uric acid in chronoamperometric mode. The following optimal parameters for the chronoamperometric determination of uric acid in flow-through conditions were established: pH 8.0, flow rate 0.2 mL·min-1, 5 U of uricase per reactor. Under these conditions, the biosensor system made it possible to determine from 10 nM to 20 µM of uric acid with the limit of detection (LOD) of 4 nM. Glucose (up to 1 mM), dopamine (up to 0.5 mM), and ascorbic acid (up to 50 µM) did not affect the signal of the biosensor toward uric acid. The biosensor was tested on spiked artificial urine samples, and showed 101% recovery for tenfold diluted samples. The ease of assembly of the flow cell and the low cost of the replacement parts make for a promising future application of the biosensor system in routine clinical analyses.

Polyvinylpyrrolidone-Coated Cubic Hollow Nanocages of PdPt3 and PdIr3 as Highly Efficient Self-Cascade Uricase/Peroxidase Mimics.

Uricase-catalyzed uric acid (UA) degradation has been applied for hyperuricemia therapy, but this medication is limited by H2O2 accumulation, which can cause oxidative stress of cells, resulting in many other health issues. Herein, we report a robust cubic hollow nanocage (HNC) system based on polyvinylpyrrolidone-coated PdPt3 and PdIr3 to serve as highly efficient self-cascade uricase/peroxidase mimics to achieve the desired dual catalysis for both UA degradation and H2O2 elimination. These HNCs have hollow cubic shape with average wall thickness of 1.5 nm, providing desired synergy to enhance catalyst's activity and stability. Density functional theory calculations suggest the PdIr3 HNC surface tend to promote OH*/O* desorption for better peroxidase-like catalysis, while the PdPt3 HNC surface accelerates the UA oxidation by facilitating O2-to-H2O2 conversion. The dual catalysis power demonstrated by these HNCs in cell studies suggests their great potential as a new type of nanozyme for treating hyperuricemia.

Study of uricase-polynorbornene conjugates derived from grafting-from ring-opening metathesis polymerization.

PEGylation has been the 'gold standard' in bioconjugation due to its ability to improve the pharmacokinetics and pharmacodynamics of native proteins. However, growing clinical evidence of hypersensitivity reactions to PEG due to pre-existing anti-PEG antibodies in healthy humans have raised concerns. Advancements in controlled polymerization techniques and conjugation chemistries have paved the way for the development of protein-polymer conjugates that can circumvent these adverse reactions while retaining the benefits of such modifications. Herein, we show the development of polynorbornene based bioconjugates of therapeutically relevant urate oxidase (UO) enzymes used in the treatment of gout synthesized by grafting-from ring-opening metathesis polymerization (ROMP). Notably, these conjugates exhibit comparable levels of bioactivity to PEGylated UO and demonstrate increased stability across varying temperatures and pH conditions. Immune recognition of conjugates by anti-UO antibodies reveal low protein immunogenicity following the conjugation process. Additionally, UO conjugates employing zwitterionic polynorbornene successfully avoid recognition by anti-PEG antibodies, further highlighting a potential replacement for PEG.

A stable liver-specific urate oxidase gene knockout hyperuricemia mouse model finds activated hepatic de novo purine biosynthesis and urate nephropathy.

Urate oxidase (Uox)-deficient mice could be an optimal animal model to study hyperuricemia and associated disorders. We develop a liver-specific conditional knockout Uox-deficient (UoxCKO) mouse using the Cre/loxP gene targeting system. These UoxCKO mice spontaneously developed hyperuricemia with accumulated serum urate metabolites. Blocking urate degradation, the UoxCKO mice showed significant de novo purine biosynthesis (DNPB) in the liver along with amidophosphoribosyltransferase (Ppat). Pegloticase and allopurinol reversed the elevated serum urate (SU) levels in UoxCKO mice and suppressed the Ppat up-regulation. Although urate nephropathy occurred in 30-week-old UoxCKO mice, 90 % of Uox-deficient mice had a normal lifespan without pronounced urate transport abnormality. Thus, UoxCKO mice are a stable model of human hyperuricemia. Activated DNPB in the UoxCKO mice provides new insights into hyperuricemia, suggesting increased SU influences purine synthesis.

A facile, low-cost bimetallic iron-nickel MOF nanozyme-propelled ratiometric fluorescent sensor for highly sensitive and selective uric acid detection and its smartphone application.

As a kind of well-known disease biomarker, uric acid (UA) is closely associated with normal metabolism and health. Despite versatile nanozymes facilitating the analysis of UA, most previous works could only generate single-signal outputs with unsatisfactory detection performance. Exploring a novel ratiometric fluorescent UA sensor with high sensitivity, reliability and portable sensing ability based on facile, low-cost nanozymes is still challenging. Herein, we report the first metal-organic-framework (MOF) nanozyme-originated ratiometric fluorescent UA sensor based on Fe3Ni-MOF-NH2 propelled UA/uricase/o-phenylenediamine tandem catalytic reaction. Different from previous reports, the peroxidase-like property and fluorescence of Fe3Ni-MOF-NH2 were simultaneously employed. In the absence of UA, only the MOF's fluorescence at 430 nm (FI430) can be observed, while the addition of UA will initiate UA/uricase catalytic reaction, and the generated H2O2 could oxidize o-phenylenediamine into highly fluorescent 2,3-diaminophenazine (DAP) (emission at 565 nm, FI565) under the catalysis of the MOF nanozyme. Coincidently, MOF's fluorescence can be quenched by DAP via the inner filter effect, resulting in a low FI430 value and high FI565 value, respectively. Therefore, H2O2 and UA can be alternatively detected through monitoring the above contrary fluorescence changes. The limit of detection for UA is 24 nM, which is much lower than those in most previous works, and the lowest among nanozyme-based ratiometric fluorescent UA sensors reported to date. Moreover, the portable sensing of UA via smartphone-based RGB analysis was facilely achieved by virtue of the above nanozyme-propelled tandem catalytic system, and MOF nanozyme-based molecular contrary logic pairs were further implemented accordingly.

Intestine-Targeted Explosive Hydrogel Microsphere Promotes Uric Acid Excretion for Gout Therapy.

Uric acid metabolism disorder triggers metabolic diseases, especially gout. However, increasing uric acid excretion remains a challenge. Here, an accelerative uric acid excretion pathway via an oral intestine-explosive hydrogel microsphere merely containing uricase and dopamine is reported. After oral administration, uricase is exposed and immobilized on intestinal mucosa along with an in situ dopamine polymerization via a cascade reaction triggered by the intestinal specific environment. By this means, trace amount of uricase is required to in situ up-regulate uric acid transporter proteins of intestinal epithelial cells, causing accelerated intestinal uric acid excretion. From in vitro data, the uric acid in fecal samples from gout patients could be significantly reduced by up to 37% by the mimic mucosa-immobilized uricase on the isolated porcine tissues. Both hyperuricemia and acute gouty arthritis in vivo mouse models confirm the uric acid excretion efficacy of intestine-explosive hydrogel microspheres. Fecal uric acid excretion is increased around 30% and blood uric acid is reduced more than 70%. In addition, 16S ribosomal RNA sequencing showed that the microspheres optimized intestinal flora composition as well. In conclusion, a unique pathway via the intestine in situ regulation to realize an efficient uric acid intestinal excretion for gout therapy is developed.

Development of a continuous fermentation process for the production of recombinant uricase enzyme by Pichia pastoris.

Recent studies in the biopharmaceutical industry have shown an increase in the productivity and production efficiency of recombinant proteins by continuous culture. In this research, a new upstream fermentation process was developed for the production of recombinant uricase in the methylotrophic yeast Pichia pastoris. Expression of recombinant protein in this system is under the control of the AOX1 promoter and therefore requires methanol as an inducing agent and carbon/energy source. Considering the biphasic growth characteristics of conventional fed-batch fermentation, physical separation of the growth and induction stages for better control of the continuous fermentation process resulted in higher dry-cell weight (DCW) and enhanced recombinant urate oxidase activity. The DCW and recombinant uricase activity enzyme for fed-batch fermentation were 79 g/L and 6.8 u/mL. During the continuous process, in the growth fermenter at a constant dilution rate of 0.025 h-1 , DCW increased to 88.39 g/L. In the induction fermenter, at methanol feeding rates of 30, 60, and 80 mL/h, a recombinant uricase activity was 4.13, 7.2, and 0 u/mL, respectively. The optimum methanol feeding regime in continuous fermentation resulted in a 4.5-fold improvement in productivity compared with fed-batch fermentation from 0.04 u/mL/h (0.0017 mg/mL/h) to 0.18 u/mL/h (0.0078 mg/mL/h).

Enhancing uric acid electrochemical detection with copper ion-activated mini protein mimicking uricase within ZIF-8: response surface methodology (RSM) optimization.

This study aims to investigate the influence of copper(II) ions as a cofactor on the electrochemical performance of a biocomposite consisting of a mini protein mimicking uricase (mp20) and zeolitic immidazolate framework-8 (ZIF-8) for the detection of uric acid. A central composite design (CCD) was utilized to optimize the independent investigation, including pH, deposition potential, and deposition time, while the current response resulting from the electrocatalytic oxidation of uric acid was used as the response. The statistical analysis of variance (ANOVA) showed a good correlation between the experimental and predicted data, with a residual standard error percentage (RSE%) of less than 2% for predicting optimal conditions. The synergistic effect of the nanoporous ZIF-8 host, Cu(II)-activated mp20, and reduced graphene oxide (rGO) layer resulted in a highly sensitive biosensor with a limit of detection (LOD) of 0.21 µM and a reproducibility of the response (RSD = 0.63%). The Cu(II)-activated mp20@ZIF-8/rGO/SPCE was highly selective in the presence of common interferents, and the fabricated layer exhibited remarkable stability with signal changes below 4.15% after 60 days. The biosensor's reliable performance was confirmed through real sample analyses of human serum and urine, with comparable recovery values to conventional HPLC.

Use of rasburicase to improve kidney function in children with hyperuricemia and acute kidney injury.

BACKGROUND: Hyperuricemia contributes to decrease in kidney function and induces additional renal damage in children with acute kidney injury (AKI). Rasburicase oxidizes uric acid (UA), decreasing its serum quantities in less than 24 h. METHODS: This is a retrospective study involving hospitalized patients under 18 years of age with underlying pathology diagnosed with AKI and severe hyperuricemia treated with rasburicase over a 4-year period. RESULTS: We describe 15 patients from 4 days of life to 18 years (median: 4.4 years). Seventy-three percent had known underlying pathologies. All presented worsening of basal renal function or AKI data. All received the usual medical treatment for AKI without response. Twenty percent received an extrarenal depuration technique. All had hyperuricemia with a mean (± SD) of 13.1 (± 2.19) mg/dl. After rasburicase administration UA levels fell to a mean (± SD) of 0.76 (± 0.62) mg/dl (p < 0.001) in less than 24 h. In parallel, a decrease in the mean plasma creatinine was observed (2.92 mg/dl to 1.93 mg/dl (p = 0.057)) together with a significant improvement of the mean glomerular filtration rate (16.3 ml/min/1.73 m2 to 78.6 ml/min/1.73 m2) (p = 0.001)). No side effects were recorded. Kidney function normalized in all cases or returned to baseline levels. CONCLUSIONS: Although the use of rasburicase is not routinely approved in pediatric patients with severe hyperuricemia and AKI, it has been used successfully without complications, and helped prevent progressive kidney damage. This study could serve as a basis for suggesting the off-label use of rasburicase for the management of complex pediatric patients in whom UA plays an important role in the development of AKI.

Pipeline Therapies for Gout.

PURPOSE OF REVIEW: Despite effective available treatments, gout management is often unsuccessful in getting patients to target serum urate goal and in managing flares in the setting of comorbidities. Studies addressing future treatment options for short- and long-term management are reviewed. RECENT FINDINGS: URAT-1 blocking agents have been helpful but have had limitations related to effects on renal function, lack of efficacy with renal impairment, and potential to increase renal stones. Dotinurad may function in the setting of decreased renal function. Arhalofenate has anti-URAT-1 activity and may also blunt gout flares. A new xanthine oxidase inhibitor (XOI), tigulixostat, is under study. New uricase treatments manufactured in combination with agents that can reduce immunogenicity may make uricase treatment simpler. A unique strategy of inhibiting gut uricase may offer the benefits of avoiding systemic absorption. For gout flares, IL-1ß inhibitor studies in progress include different dosing schedules. Dapansutrile, an oral agent under investigation, inhibits activation of the NLRP3 inflammasome and may be an effective anti-inflammatory. New treatments for gout that are under study may work in the setting of comorbidities, simplify management, utilize new mechanisms, or have reduced side effects.

Calcium Fluoride/Manganese Dioxide Nanocomposite with Dual Enzyme-like Activities for Uric Acid Sensing: A Comparative Study of Enzyme and Nonenzyme Methods.

The debate over enzyme methods versus nonenzyme methods in the field of nanosensing has lasted for decades despite hundreds of published studies on this topic. In this study, we first present a comparative analysis of these methods using a reaction based on the CaF2/MnO2 nanocomposite (CM Nc) with dual-enzyme activity, presenting oxidase- and peroxidase-like activities. Uric acid (UA) is a byproduct of purine metabolism in the body, and abnormal levels can cause many diseases; hence, tracking the amount of UA in human serum is crucial. The enzyme method was established using uricase and CM Nc: UA produced H2O2 when catalyzed by uricase; H2O2 was then catalyzed into reactive oxygen species (ROS) by the peroxidase activity of the CM Nc; this ROS oxidized 3,3',5,5'-tetramethylbenzidine (TMB), which was oxidized into blue oxidized TMB (oxTMB). The nonenzyme method was built on the scavenging effect of UA on the ROS, which prevented the catalytic capability of CM Nc toward TMB and induced blue oxTMB fading. The results of further tests revealed the good selectivity of the enzyme method compared to the fast response of the nonenzyme method. Additionally, both methods were effective in determining the UA concentration in human serum. The two separate methods can also independently verify each other, increasing the accuracy of the detection results in accordance with the relatively independent detection principles. This research provided theoretical backing for the practical design of multienzyme nanozyme catalysts, which can facilitate the precise detection of UA in biochemical products.

In vivo study of newly developed albumin-conjugated urate oxidase for gout treatment.

BACKGROUND: Exogenously providing engineered Uox with enhanced half-life is one of the important urate-lowering treatments for gout. The potential of PAT101, a recombinant human albumin (rHA)-conjugated variant, was evaluated and compared as a novel gout treatment through various in vivo studies with PAT101 and competing drugs. METHODS: PAT101 was produced by site-specific conjugation of rHA and Aspergillus flavus Uox (AfUox-rHA) through clickable non-natural amino acid (frTet) and Inverse electron demand Diels-Alder (IEDDA) reaction. In vivo pharmacokinetics, efficacy tests and in vitro immunogenetic assay were performed after single or multiple doses of PAT101 and its competitors in BALB/c mice, transgenic (TG) mice, Sprague-Dawley (SD) rats, and non-human primate (NHP). RESULTS: The half-life of PAT101 in single-dose treated TG mice was more than doubled compared to pegloticase. In SD rats with 4 weeks of repeated administration of rasburicase, only 24% of Uox activity remained, whereas in PAT101, it was maintained by 86%. In the Uox KO model, the survival rate of PAT101 was comparable to that of pegloticase. In addition, human PBMC-based CD4+/CD8+ T-cell activation analysis demonstrated that PAT101 has a lower immune response compared to the original drug, rasburicase. CONCLUSION: All results suggest that this rHA-conjugated AfUox, PAT101, can be provided as a reliable source of Uox for gout treatment.

Pegloticase co-administered with high MW polyethylene glycol effectively reduces PEG-immunogenicity and restores prolonged circulation in mouse.

The interactions between polymers and the immune system remains poorly controlled. In some instances, the immune system can produce antibodies specific to polymer constituents. Indeed, roughly half of pegloticase patients without immunomodulation develop high titers of anti-PEG antibodies (APA) to the PEG polymers on pegloticase, which then quickly clear the drug from circulation and render the gout treatment ineffective. Here, using pegloticase as a model drug, we show that addition of high molecular weight (MW) free (unconjugated) PEG to pegloticase allows us to control the immunogenicity and mitigates APA induction in mice. Compared to pegloticase mixed with saline, mice repeatedly dosed with pegloticase containing different MW or amount of free PEG possessed 4- to 12- fold lower anti-PEG IgG, and 6- to 10- fold lower anti-PEG IgM, after 3 rounds of pegloticase dosed every 2 weeks. The markedly reduced APA levels, together with competitive inhibition by free PEG, restored the prolonged circulation of pegloticase to levels observed in APA-naïve animals. In contrast, mice with pegloticase-induced APA eliminated nearly all pegloticase from the circulation within just four hours post-injection. These results support the growing literature demonstrating free PEG may effectively suppress drug-induced APA, which in turn may offer sustained therapeutic benefits without requiring broad immunomodulation. We also showed free PEG effectively blocked the PEGylated protein from binding with cells expressing PEG-specific B cell receptors. It provides a template of how we may be able to tune the interactions and immunogenicity of other polymer-modified therapeutics. STATEMENT OF SIGNIFICANCE: A major challenge with engineering materials for drug delivery is their interactions with the immune system. For instance, our body can produce high levels of anti-PEG antibodies (APA). Unfortunately, the field currently lack tools to limit immunostimulation or overcome pre-existing anti-PEG antibodies, without using broad immunosuppression. Here, we showed that simply introducing free PEG into a clinical formulation of PEG-uricase can effectively limit induction of anti-PEG antibodies, and restore their prolonged circulation upon repeated dosing. Our work offers a readily translatable method to safely and effectively restore the use PEG-drugs in patients with PEG-immunity, and provides a template to use unconjugated polymers with low immunogenicity to regulate interactions with the immune system for other polymer-modified therapeutics.

Mechanisms and rationale for uricase use in patients with gout.

Xanthine oxidase inhibitors such as allopurinol and febuxostat have been the mainstay urate-lowering therapy (ULT) for treating hyperuricaemia in patients with gout. However, not all patients receiving oral ULT achieve the target serum urate level, in part because some patients cannot tolerate, or have actual or misconceived contraindications to, their use, mainly due to comorbidities. ULT dosage is also limited by formularies and clinical inertia. This failure to sufficiently lower serum urate levels can lead to difficult-to-treat or uncontrolled gout, usually due to poorly managed and/or under-treated gout. In species other than humans, uricase (urate oxidase) converts urate to allantoin, which is more soluble in urine than uric acid. Exogenic uricases are an exciting therapeutic option for patients with gout. They can be viewed as enzyme replacement therapy. Uricases are being used to treat uncontrolled gout, and can achieve rapid reduction of hyperuricaemia, dramatic resolution of tophi, decreased chronic joint pain and improved quality of life. Availability, cost and uricase immunogenicity have limited their use. Uricases could become a leading choice in severe and difficult-to-treat gout as induction and/or debulking therapy (that is, for lowering of the urate pool) to be followed by chronic oral ULT. This Review summarizes the evidence regarding available uricases and those in the pipeline, their debulking effect and their outcomes related to gout and beyond.