Discovery and characterization of verinurad, a potent and specific inhibitor of URAT1 for the treatment of hyperuricemia and gout

Transport mechanism and structural pharmacology of human urate transporter URAT1

Urate is an endogenous product of purine metabolism in the liver. High urate levels in the blood lead to gout, a very common and painful inflammatory arthritis. Excreted urate is reabsorbed in the kidney mainly by URAT1 antiporter, a key target for anti-gout drugs. To uncover the mechanisms of urate transport and drug inhibition, we determined cryo-EM structures of human URAT1 with urate, counter anion pyrazinoate, or anti-gout drugs of different chemotypes - lesinurad, verinurad, and dotinurad. We captured the outward-to-inward transition of URAT1 during urate uptake, revealing that urate binds in a phenylalanine-rich pocket and engages with key gating residues to drive the transport cycle. In contrast to the single binding site for urate, pyrazinoate interacts with three distinct, functionally relevant sites within URAT1, a mechanism that has not yet been observed in other anion antiporters. In addition, we found that while all three drugs compete with substrates and halt the transport cycle, verinurad and dotinurad further hijack gating residues to achieve high potency. These insights advance our understanding of organic anion transport and provide a foundation for designing improved gout therapeutics.

Verinurad Plus Allopurinol for Heart Failure With Preserved Ejection Fraction: The AMETHYST Randomized Clinical Trial

Importance

Elevated serum uric acid (SUA) level may contribute to endothelial dysfunction; therefore, SUA is an attractive target for heart failure with preserved ejection fraction (HFpEF). However, to the authors' knowledge, no prior randomized clinical trials have evaluated SUA lowering in HFpEF.

Objective

To investigate the efficacy and safety of the novel urate transporter-1 inhibitor, verinurad, in patients with HFpEF and elevated SUA level.

Design, Setting, and Participants

This was a phase 2, double-blind, randomized clinical trial (32-week duration) conducted from May 2020 to April 2022. The study took place at 59 centers in 12 countries and included patients 40 years and older with HFpEF and SUA level greater than 6 mg/dL. Data were analyzed from August 2022 to May 2024.

Interventions

Eligible patients were randomized 1:1:1 to once-daily, oral verinurad, 12 mg, plus allopurinol, 300 mg; allopurinol, 300 mg, monotherapy; or placebo for 24 weeks after an 8-week titration period. Allopurinol was combined with verinurad to prevent verinurad-induced urate nephropathy, and the allopurinol monotherapy group was included to account for allopurinol effects in the combination therapy group. All patients received oral colchicine, 0.5 to 0.6 mg, daily for the first 12 weeks after randomization.

Main Outcomes and Measures

Key end points included changes from baseline to week 32 in peak oxygen uptake (VO2), Kansas City Cardiomyopathy Questionnaire total symptom score (KCCQ-TSS), and SUA level; and safety/tolerability (including adjudicated cardiovascular events).

Results

Among 159 randomized patients (53 per treatment group; median [IQR] age, 71 [40-86] years; 103 male [65%]) with median (IQR) N-terminal pro-brain natriuretic peptide level of 527 (239-1044) pg/mL and SUA level of 7.5 (6.6-8.4) mg/dL, verinurad plus allopurinol (mean change, -59.6%; 95% CI, -64.4% to -54.2%) lowered SUA level to a greater extent than allopurinol (mean change, -37.6%; 95% CI, -45.3% to -28.9%) or placebo (mean change, 0.8%; 95% CI, -11.8% to 15.2%; P < .001). Changes in peak VO2 (verinurad plus allopurinol, 0.27 mL/kg/min; 95% CI, -0.56 to 1.10 mL/kg/min; allopurinol, -0.17 mL/kg/min; 95% CI, -1.03 to 0.69 mL/kg/min; placebo, 0.37 mL/kg/min; 95% CI, -0.45 to 1.19 mL/kg/min) and KCCQ-TSS (verinurad plus allopurinol, 4.3; 95% CI, 0.3-8.3; allopurinol, 4.5; 95% CI, 0.3-8.6; placebo, 1.2; 95% CI, -3.0 to 5.3) were similar across groups. There were no adverse safety signals. Deaths or cardiovascular events occurred in 3 patients (5.7%) in the verinurad plus allopurinol group, 8 patients (15.1%) in the allopurinol monotherapy group, and 6 patients (11.3%) in the placebo group.

Conclusions and Relevance

Results of this randomized clinical trial show that despite substantial SUA lowering, verinurad plus allopurinol did not result in a significant improvement in peak VO2 or symptoms compared with allopurinol monotherapy or placebo in HFpEF.

Trial Registration

ClinicalTrials.gov Identifier: NCT04327024.

Crystal structure validation of verinurad via proton-detected ultra-fast MAS NMR and machine learning

The recent development of ultra-fast magic-angle spinning (MAS) (>100 kHz) provides new opportunities for structural characterization in solids. Here, we use NMR crystallography to validate the structure of verinurad, a microcrystalline active pharmaceutical ingredient. To do this, we take advantage of 1H resolution improvement at ultra-fast MAS and use solely 1H-detected experiments and machine learning methods to assign all the experimental proton and carbon chemical shifts. This framework provides a new tool for elucidating chemical information from crystalline samples with limited sample volume and yields remarkably faster acquisition times compared to 13C-detected experiments, without the need to employ dynamic nuclear polarization.

Combination Treatment with Verinurad and Allopurinol in CKD: A Randomized Placebo and Active Controlled Trial

Key Points

The SAPPHIRE trial was designed to assess albuminuria-lowering effects of the urate transporter 1 inhibitor verinurad combined with allopurinol in patients with CKD. Verinurad 3, 7.5, and 12 mg in combination with allopurinol 300 mg did not reduce albuminuria during 34 weeks treatment compared with allopurinol alone or placebo. Verinurad/allopurinol combination dose-dependently reduced serum urate concentrations compared with placebo.

Background

Hyperuricemia is associated with elevated risks of cardiovascular and chronic kidney disease (CKD). Since inhibition of urate transporter 1 has been suggested to be potentially nephroprotective, we performed a phase 2b study to assess albuminuria-lowering effects of the urate transporter 1 inhibitor verinurad combined with the xanthine oxidase inhibitor allopurinol in patients with CKD and hyperuricemia.

Methods

In this randomized placebo and active controlled trial, we enrolled participants with serum urate concentrations ≥6.0 mg/dl, eGFR ≥25 ml/min per 1.73 m2, and a urinary albumin-creatinine ratio (UACR) 30–5000 mg/g to one of five treatment arms: placebo, placebo+allopurinol 300 mg/day, verinurad 3 mg+allopurinol 300 mg/day, verinurad 7.5 mg+allopurinol 300 mg/day, or verinurad 12 mg+allopurinol 300 mg/day in a 1:1:1:1:1 ratio. The primary end point was the change in UACR from baseline to 34 weeks. Secondary end points were changes from baseline in UACR at week 60 and changes in serum urate and eGFR at weeks 34 and 60.

Results

Between August 2019 and November 2021, 861 adults with CKD (mean age 65 years, 33.0% female, mean eGFR 48 ml/min per 1.73 m2, median UACR 217 mg/g) were enrolled. At 34 weeks, the geometric mean percentage change in UACR from baseline did not differ among treatment groups (16.7%, 95% confidence interval [CI], −0.6 to 37.1 in the 3 mg group, 15.0% [95% CI, −1.85 to 34.6] in the 7.5 mg group, 14.0% [95% CI, −3.4 to 34.4] in the 12 mg group versus 9.9% [95% CI, −6.6 to 29.4] in the allopurinol group, and 37.3% [95% CI, 16.6 to 61.8] in the placebo group). UACR and eGFR change from baseline did not differ among treatment groups after 60 weeks. Verinurad/allopurinol combination dose-dependently reduced serum urate concentrations compared with placebo. The proportion of patients with adverse events and serious adverse events was balanced among treatment groups.

Conclusions

Verinurad in combination with allopurinol did not decrease UACR or eGFR decline, but further reduced serum urate compared with allopurinol alone or placebo.

Clinical Trial registry name and registration number:

SAPPHIRE Trial registration number, NCT03990363 .

A System for Discovering Novel Uricosurics Targeting Urate Transporter 1 Based on In Vitro and In Vivo Modeling

Hyperuricemia has become a global burden with the increasing prevalence and risk of associated metabolic disorders and cardiovascular diseases. Uricosurics act as a vital urate-lowering therapy by promoting uric acid excretion via the kidneys. However, potent and safe uricosurics are still in urgent demand for use in the clinic. In this study, we aimed to establish in vitro and in vivo models to aid the discovery of novel uricosurics, and to search for potent active compounds, especially targeting urate transporter 1 (URAT1), the major urate transporter in the kidney handling uric acid homeostasis. As a result, for preliminary screening, the in vitro URAT1 transport activity was assessed using a non-isotopic uric acid uptake assay in hURAT1-stably expressed HEK293 cells. The in vivo therapeutic effect was evaluated in a subacute hyperuricemic mouse model (sub-HUA) and further confirmed in a chronic hyperuricemic mouse model (Ch-HUA). By utilizing these models, compound CC18002 was obtained as a potent URAT1 inhibitor, with an IC50 value of 1.69 μM, and favorable uric acid-lowering effect in both sub-HUA and Ch-HUA mice, which was comparable to that of benzbromarone at the same dosage. Moreover, the activity of xanthine oxidoreductase, the key enzyme catalyzing uric acid synthesis, was not altered by CC18002 treatment. Taken together, we have developed a novel screening system, including a cell model targeting URAT1 and two kinds of mouse models, for the discovery of novel uricosurics. Utilizing this system, compound CC18002 was investigated as a candidate URAT1 inhibitor to treat hyperuricemia.

Systematic review and model-based analysis to identify whether renal safety risks of URAT1 inhibitors are fully determined by uric acid-lowering efficacies

OBJECTIVE

Renal safety risk is currently an important factor that hinders the development of uric acid transporter 1 (URAT1) inhibitors. This study aimed to compare the renal safety and uric acid-lowering efficacy of different URAT1 inhibitors and clarify the association between them.

METHODS

A systematic review of published randomized controlled trials on URAT1 inhibitors was conducted to investigate the incidence of renal safety events. A model-based analysis was performed to predict the uric acid-lowering efficacy of representative URAT1 inhibitors.

RESULTS

The overall renal safety event incidences of lesinurad, verinurad, dotinurad, SHR4640, and benzbromarone in patients with hyperuricemia were 11.2 % (142/1264), 12.0 % (34/284), 0.5 % (2/421), 2.3 % (5/213), and 1.3 % (5/393), respectively. A semi-mechanistic pharmacokinetic/pharmacodynamic model was used to establish the dose-exposure-effect relationship of lesinurad, verinurad, dotinurad, and SHR4640 with or without the combination of xanthine oxidase inhibitors (XOIs). The efficacy ranking of the intermediate dose of URAT1 inhibitors with once-daily dosing was 2 mg dotinurad > 10 mg verinurad > 5 mg SHR4640 > 400 mg lesinurad. The combination of 80 mg febuxostat and 600 mg allopurinol reduced the 24-h cumulative renal uric acid excretion by 48.4 % and 48.3 %, respectively.

CONCLUSION

Uric acid-lowering efficacy is not an independent factor for the renal safety risk of different URAT1 inhibitors, and structural differences could be responsible for the difference. The adverse renal effects of URAT1 inhibitors are dose-dependent, and the combination with high doses of XOIs can significantly reduce the renal safety risk by reducing uric acid excretion by the kidneys.

Emerging Urate-Lowering Drugs and Pharmacologic Treatment Strategies for Gout: A Narrative Review

Hyperuricemia with consequent monosodium urate crystal deposition leads to gout, characterized by painful, incapacitating inflammatory arthritis flares that are also associated with increased cardiovascular event and related mortality risk. This narrative review focuses on emerging pharmacologic urate-lowering treatment (ULT) and management strategies in gout. Undertreated, gout can progress to palpable tophi and joint damage. In oral ULT clinical trials, target serum urate of < 6.0 mg/dL can be achieved in ~ 80-90% of subjects, with flare burden reduction by 1-2 years. However, real-world ULT results are far less successful, due to both singular patient nonadherence and prescriber undertreatment, particularly in primary care, where most patients are managed. Multiple dose titrations commonly needed to optimize first-line allopurinol ULT monotherapy, and substantial potential toxicities and other limitations of approved, marketed oral monotherapy ULT drugs, promote hyperuricemia undertreatment. Common gout comorbidities with associated increased mortality (e.g., moderate-severe chronic kidney disease [CKD], type 2 diabetes, hypertension, atherosclerosis, heart failure) heighten ULT treatment complexity and emphasize unmet needs for better and more rapid clinically significant outcomes, including attenuated gout flare burden. The gout drug armamentarium will be expanded by integrating sodium-glucose cotransporter-2 (SGLT2) inhibitors with uricosuric and anti-inflammatory properties as well as clinically indicated antidiabetic, nephroprotective, and/or cardioprotective effects. The broad ULT developmental pipeline is loaded with multiple uricosurics that selectively target uric acid transporter 1 (URAT1). Evolving ULT approaches include administering selected gut anaerobic purine degrading bacteria (PDB), modulating intestinal urate transport, and employing liver-targeted xanthine oxidoreductase mRNA knockdown. Last, emerging measures to decrease the immunogenicity of systemically administered recombinant uricases should simplify treatment regimens and further improve outcomes in managing the most severe gout phenotypes.

Investigation of the Inhibition Mechanism of Xanthine Oxidoreductase by Oxipurinol: A Computational Study

Xanthine oxidoreductase (XOR) is an enzyme found in various organisms. It converts hypoxanthine to xanthine and urate, which are crucial steps in purine elimination in humans. Elevated uric acid levels can lead to conditions like gout and hyperuricemia. Therefore, there is significant interest in developing drugs that target XOR for treating these conditions and other diseases. Oxipurinol, an analogue of xanthine, is a well-known inhibitor of XOR. Crystallographic studies have revealed that oxipurinol directly binds to the molybdenum cofactor (MoCo) in XOR. However, the precise details of the inhibition mechanism are still unclear, which would be valuable for designing more effective drugs with similar inhibitory functions. In this study, molecular dynamics and quantum mechanics/molecular mechanics calculations are employed to investigate the inhibition mechanism of XOR by oxipurinol. The study examines the structural and dynamic effects of oxipurinol on the pre-catalytic structure of the metabolite-bound system. Our results provide insights on the reaction mechanism catalyzed by the MoCo center in the active site, which aligns well with experimental findings. Furthermore, the results provide insights into the residues surrounding the active site and propose an alternative mechanism for developing alternative covalent inhibitors.

Identification of 5-[5-cyano-1-(pyridin-2-ylmethyl)-1H-indole-3-carboxamido] thiazole-4-carboxylic acid as a promising dual inhibitor of urate transporter 1 and xanthine oxidase

In combination with allopurinol, tranilast is used as an urate transporter 1 (URAT1) inhibitor for the treatment of hyperuricemia, but its structure-activity relationship concerning URAT1 inhibitory activity is rarely studied. In this paper, analogs 1-30 were designed and synthesized using scaffold hopping strategy on the basis of tranilast and the privileged scaffold indole. Then, URAT1 activity was evaluated using ¹⁴C-uric acid uptake assay with HEK293-URAT1 overexpressing cells. Compared with tranilast (inhibitory rate = 44.9% at 10 μM), most compounds displayed apparent inhibitory effects, ranging from 40.0% to 81.0% at 10 μM on URAT1. Surprisingly, along with the bringing in of a cyano group at the 5-position of indole ring, compounds 26 and 28-30 exerted xanthine oxidase (XO) inhibitory activity. In particular, compound 29 presented potency on URAT1 (48.0% at 10 μM) and XO (IC₅₀ = 1.01 μM). Molecular simulation analysis revealed that the basic structure of compound 29 had an affinity with URAT1, and XO. Furthermore, compound 29 demonstrated a significant hypouricemic effect in a potassium oxonate-induced hyperuricemia rat model at an oral dose of 10 mg/kg during in vivo tests. In summary, tranilast analog 29 was identified as a potent dual-target inhibitor of URAT1 and XO, and a promising lead compound for further investigation.

Pharmacological evaluation of a novel skeleton compound isobavachin (4',7-dihydroxy-8-prenylflavanone) as a hypouricemic agent: Dual actions of URAT1/GLUT9 and xanthine oxidase inhibitory activity

Previously we discovered a novel natural scaffold compound, isobavachin (4', 7-dihydroxy-8-prenylflavanone), as a potent URAT1 inhibitor by shape and structure based on a virtue screening approach. In this study, further urate-lowering mechanism, pharmacokinetics and toxicities of isobavachin were conducted. Isobavachin inhibited URAT1 with an IC₅₀ value of 0.24 ± 0.06 μM, and residues S35, F365, I481 and R477 of URAT1 contributed to high affinity for isobavachin. Isobavachin also inhibited glucose transporter 9 (GLUT9), another pivotal urate reabsorption transporter, with an IC₅₀ value of 1.12 ± 0.26 μM. Molecular docking and MMGBSA results indicated that isobavachin might compete residues R171, L75 and N333 with uric acid, which leads to inhibition of uric acid transport of GLUT9. Isobavachin weakly inhibited urate secretion transporters OAT1 with an IC₅₀ value of 4.38 ± 1.27 μM, OAT3 with an IC₅₀ of 3.64 ± 0.62 μM, and ABCG2 with an IC₅₀ of 10.45 ± 2.17 μM. Isobavachin also inhibited xanthine oxidase (XOD) activity in vitro with an IC₅₀ value of 14.43 ± 3.56 μM, and inhibited the hepatic XOD activities at 5-20 mg/kg in vivo. Docking and MMGBSA analysis indicated that isobavachin might bind to the Mo-Pt catalyze center of XOD, which leads to inhibition of uric acid production. In vivo, isobavachin exhibited powerful urate-lowering and uricosuric effects at 5-20 mg/kg compared with the positive drugs morin (20 mg/kg) and RDEA3170 (10 mg/kg). Safety assessments revealed that isobavachin was safe and had no obvious toxicities. Isobavachin has little cell toxicity in HK2 cells as indicated by the MTT assay. In vivo, after treatment with 50 mg/kg isobavachin for 14 days, isobavachin had little renal toxicity, as revealed by serum CR/BUN levels, and no hepatotoxicity as revealed by ALT/AST levels. Further HE examination also suggests that isobavachin has no obvious kidney/liver damage. A pharmacokinetic study in SD rats indicated isobavachin had lower bioavailability (12.84 ± 5.13 %) but long half-time (7.04 ± 2.68 h) to maintain a continuous plasma concentration. Collectively, these results indicate that isobavachin deserves further investigation as a candidate anti-hyperuricemic drug with a novel mechanism of action: selective urate reabsorption inhibitor (URAT1/GLUT9) with a moderate inhibitory effect on XOD.

Longitudinal changes in uric acid concentration and their relationship with chronic kidney disease progression in children and adolescents

BACKGROUND

Elevated serum uric acid concentration is a risk factor for CKD progression. Its change over time and association with CKD etiology and concomitant changes in estimated glomerular filtration rate (eGFR) in children and adolescents are unknown.

METHODS

Longitudinal study of 153 children/adolescents with glomerular (G) and 540 with non-glomerular (NG) etiology from the CKD in Children (CKiD) study. Baseline serum uric acid, change in uric acid and eGFR over time, CKD etiology, and comorbidities were monitored. Adjusted linear mixed-effects regression models quantified the relationship between within-person changes in uric acid and concurrent within-person changes in eGFR.

RESULTS

Participants with stable uric acid over follow-up had CKD progression which became worse for increased baseline uric acid (average annual percentage changes in eGFR were - 1.4%, - 7.7%, and - 14.7% in those with G CKD with baseline uric acid < 5.5 mg/dL, 5.5 - 7.5 mg/dL, and > 7.5 mg/dL, respectively; these changes were - 1.4%, - 4.1%, and - 8.6% in NG CKD). Each 1 mg/dL increase in uric acid over follow-up was independently associated with significant concomitant eGFR decreases of - 5.7% (95%CI - 8.4 to - 3.0%) (G) and - 5.1% (95%CI - 6.3 to - 4.0%) (NG) for those with baseline uric acid < 5.5 mg/dL and - 4.3% (95%CI - 6.8 to - 1.6%) (G) and - 3.3% (95%CI - 4.1 to - 2.6%) (NG) with baseline uric acid between 5.5 and 7.5 mg/dL.

CONCLUSIONS

Higher uric acid levels and increases in uric acid over time are risk factors for more severe progression of CKD in children and adolescents. A higher resolution version of the Graphical abstract is available as Supplementary information.

Virtual screening and activity evaluation of human uric acid transporter 1 (hURAT1) inhibitors

Hyperuricemia is a disease caused by disorder of purine metabolism, mainly due to insufficient renal excretion of uric acid. Urate transporter 1 (URAT1) is the most widely studied target of urate transporters, and used for uric acid (UA) reabsorption. This study used the AlphaFold2 algorithm to predict the structure of URAT1. Virtual screening and biological evaluation were used to discover novel URAT1 inhibitors that target the critical amino acids. Seven compounds were screened from the T2220 database and validated as URAT1 inhibitors by cell biology experiments. The IC50 values of benbromarone, NP023335, TN1148, and TN1008 were 6.878, 18.46, 24.64, and 53.04 μM, respectively. Molecular dynamics simulation was used to investigate the binding mechanism of URAT1 to NP023335, which forms stable contact with Ser35, Phe365, and Arg477. These interactions are essential for maintaining the biological activity of NP023335. The three compounds' pharmacokinetic characteristics were predicted, and NP023335's properties matched those of an empirical medication with the benefits of high solubility, low cardiotoxicity, good membrane permeability, and oral absorption. The natural product NP023335 will serve as a promising hit compound for facilitating the further design of novel URAT1 inhibitors.

Design, synthesis and activity evaluation of novel lesinurad analogues containing thienopyrimidinone or pyridine substructure as human urate transporter 1 inhibitors

Urate Transporter 1 (URAT1) plays a crucial role in uric acid transport, making it an attractive target for the treatment of gout and hyperuricemia. As a representative URAT1 inhibitor, Lesinurad treat gout by promoting the uric acid excretion. However, its lower in vitro and in vivo activity should be highly attracted attention. Herein, the bioisosterism, molecular hybridization and scaffold hopping strategies were exploited to modify all the structural components of Lesinurad and finally thirty novel compounds bearing thienopyrimidinone or pyridine core were obtained. Most of the compounds displayed certain URAT1 inhibitory activity in vitro. Among them, thienopyrimidinones 6 (IC50 = 7.68 μM), 10 (IC50 = 7.56 μM), 14 (IC50 = 7.31 μM) and 15 (IC50 = 7.90 μM) showed slightly better potency than positive control Lesinurad (IC50 = 9.38 μM). Notably, 10 also displayed inhibitory activity (IC50 = 55.96 μM) against GLUT9. Additionally, in vivo serum uric acid (SUA)-lowering experiments were performed on some representative compounds and it was revealed that all the selected compounds could decrease the SUA level in mice, of which the decrease rate of SUA was 73.29% for the most promising compound 10, significantly greater than that of Lesinurad (26.89%). Meanwhile, the preliminary SARs based on the URAT1 inhibitory activity were discussed in detail, which pointed out the direction for further structural optimization. Overall, the thienopyrimidinone and pyridine are prospective skeletons for the developing novel URAT1 inhibitors with considerable potential for optimization.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2020-present)

INTRODUCTION

The urate transporter 1 (URAT1) is a membrane transporter located in the apical membrane of human renal proximal tubule epithelial cells, which mediates most of the reabsorption of urate. Hyperuricemia (HUA) is a common disease caused by metabolic disorders, which has been considered as the key factor of gout. Approximately 90% of patients suffer from hyperuricemia due to insufficient or poor uric acid excretion. Therefore, the drug design of URAT1 inhibitors targeting improve the renal urate excretion by reducing the reabsorption of urate anions represent a hot topic in searching for anti-gout drugs currently.

AREAS COVERED

In this review, we summarize URAT1 inhibitors patents reported since 2020 to present through the public database at https://worldwide.espacenet.com and some medicinal chemistry strategies employed to develop novel drug candidates.

EXPERT OPINION

Ligand-based drug design (LBDD) strategies have been frequently used developing new URAT1 inhibitors. Meanwhile, the discovery of dual drugs targeting both inhibition of xanthine oxidase (XOD) and URAT1 may be an emerging horizon for designing novel uric acid-lowering candidates in future. Furthermore, advanced techniques in the field of molecular biology and computer science can increase the chances to discover and/or optimize URAT1 inhibitors, contributing to the development of novel drug candidates.

A Brief Review of Natural Products with Urate Transporter 1 Inhibition for the Treatment of Hyperuricemia

Hyperuricemia is a common disease caused by a high level of uric acid. Urate transporter 1 (URAT1) is an important protein and mediates approximately 90% of uric acid reabsorption. Therefore, the URAT1 inhibitor is a class of uricosuric medicines widely used in the clinic for the treatment of hyperuricemia. To find the new medicine with stronger URAT1 inhibition and lower toxicity, researchers have been exploring natural products. This study systematically summarizes the natural products with URAT1 inhibition. The results show that many natural products are potential URAT1 inhibitors, such as flavonoids, terpenoids, alkaloids, coumarins, stilbenes, and steroids, among which flavonoids are the most promising source of URAT1 inhibitors. It is worth noting that most studies have focused on finding natural products with inhibition of URAT1 and have not explored their activities and mechanisms toward URAT1. By reviewing the few existing studies of the structure-activity relationship and analyzing common features of natural products with URAT1 inhibition, we speculate that the rigid ring structure and negative charge may be the keys for natural products to produce URAT1 inhibition. In conclusion, natural products are potential URAT1 inhibitors, and exploring the mechanism of action and structure-activity relationship will be an important research direction in the future.

Mutation in Transmembrane Domain 8 of Human Urate Transporter 1 Disrupts Uric Acid Recognition and Transport

Human urate transporter 1 (hURAT1) is the most pivotal therapeutic target for hyperuricemia. Due to a lack of crystal structure information, the atomic structure of URAT1 is not clearly understood. In this study, a multiple sequence alignment was performed, and K393, a positively charged residue in transmembrane domain (TMD) 8, was observed to be highly conserved in organic anion transporters (OATs). K393 was substituted with a positively, negatively, and neutrally charged amino acid via site-directed mutagenesis and then used to transfect HEK293 cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) analyses indicated that mutants of K393 showed mRNA and protein expression levels similar to those in the WT group. The nonpositively charged mutants K393A, K393D, and K393E eliminated 70-80% of ¹⁴C-uric acid transport capacity, while the K393H mutant showed slight and the K393R mutant showed no reduced transport capacity compared with the WT group. Binding assays indicated that K393A, K393D, and K393E conferred lowered uric acid binding affinity. As indicated by the K _m and V _max values obtained from saturation kinetic experiments, K393A, K393D, and K393E showed increased K _m values, but K393R and K393H showed K _m values similar to those in the WT group. K393 also contributed to a high affinity for benzbromarone (BM) interaction. The inhibitory effects of BM were partly abolished in K393 mutants, with increased IC₅₀ values compared with the WT group. BM also exhibited weaker inhibitory effects on ¹⁴C-uric acid binding in K393R and K393H mutants. In an outward homology model of URAT1, K393 was located in the inner part of the transport tunnel, and further molecular docking analysis indicated that uric acid and BM showed possible hydrogen bonds with K393. Mutants K393R and K393H showed possible interactions with uric acid, and positive charges confer high affinity for uric acid as revealed by their surface electrostatic potential. In conclusion, our data provide evidence that K393 is an important residue for the recognition of uric acid or inhibitors by URAT1.

Research progress of risk factors and early diagnostic biomarkers of gout-induced renal injury

Gout renal injury has an insidious onset, no obvious symptoms, and laboratory abnormalities in the early stages of the disease. The injury is not easily detected, and in many cases, the patients have entered the renal failure stage at the time of diagnosis. Therefore, the detection of gout renal injury–related risk factors and early diagnostic biomarkers of gout renal injury is essential for the prevention and early diagnosis of the disease. This article reviews the research progress in risk factors and early diagnostic biomarkers of gout renal injury.

Discovery of novel benzbromarone analogs with improved pharmacokinetics and benign toxicity profiles as antihyperuricemic agents

Benzbromarone (BM) is a potent URAT1 inhibitor approved for the treatment of gout. However, the low URAT1-selectivity and hepatotoxcity limit its clinical use. To solve these problems, we rationally designed and synthesized a series of BM derivatives by chemotype hybridization and bioisosteric replacement. Most compounds exhibited potent inhibitory activities against URAT1 with IC₅₀ values ranging from 5.83 μM to 0.80 μM. Among them, JNS4 exhibited the highest URAT1 inhibitory activity with an IC₅₀ of 0.80 μM, comparable to that of BM (IC₅₀ = 0.53 μM). Molecular dynamic simulations showed that JNS4 formed π-cation interaction with R477, the same as BM. Different from BM, JNS4 bound to W357 and H245 via π-π interactions and formed a hydrogen bond with S35, which might contribute to the high URAT1 binding affinity of JNS4. JNS4 hardly inhibited GLUT9 (IC₅₀ > 20 μM), another urate reabsorption transporter. In addition, JNS4 showed little inhibitory effects against OAT1 and ABCG2 with IC₅₀ of 4.04 μM and 10.16 μM, respectively. Importantly, JNS4 displayed higher in vivo urate-lowering effects at doses of 1-4 mg/kg in a mouse model of hyperuricemia, as compared to BM and lesinurad. Furthermore, JNS4 possessed favorable pharmacokinetic properties with an oral bioavailability of 55.28%, significantly higher than that of BM (36.11%). Moreover, JNS4 demonstrated benign toxicity profiles (no cytotoxicities against HepG2 and HK2 cells; no hepatic and renal toxicities observed in vivo). Collectively, these results suggest that JNS4 represents a novel, safe and selective URAT1 inhibitor with excellent druggabilities and is worthy of further investigation as an anti-hyperuricemic agent.

Susceptibility genes of hyperuricemia and gout

Gout is a chronic metabolic disease that seriously affects human health. It is also a major challenge facing the world, which has brought a heavy burden to patients and society. Hyperuricemia (HUA) is the most important risk factor for gout. In recent years, with the improvement of living standards and the change of dietary habits, the incidence of gout in the world has increased dramatically, and gradually tends to be younger. An increasing number of studies have shown that gene mutations may play an important role in the development of HUA and gout. Therefore, we reviewed the existing literature and summarized the susceptibility genes and research status of HUA and gout, in order to provide reference for the early diagnosis, individualized treatment and the development of new targeted drugs of HUA and gout.

UHPLC-MS/MS-based method for quantification of verinurad in rat plasma and its application in a bioavailability study

A rapid and sensitive UHPLC-MS/MS method was developed and fully validated for the quantification of verinurad in rat plasma. Lesinurad was used as an internal standard (IS) and simple protein precipitation was utilized to prepare the analytes from the matrix. Chromatographic separation was carried out on a Zorbax SB C18 column. The mobile phase consisted of water with 0.1% formic acid (A) and acetonitrile with 0.1% formic acid (B) at a flow rate of 0.3 mL/min. The short run time of 4 min made it possible to analyze more than 300 samples per day. The ion transitions were quantified in negative mode with MRM transitions of 347.1→261.1 for verinurad and 404.2→178.9 for the internal standard. The validated linear ranges of verinurad were 10-5000 ng/mL in rat plasma. The validated UHPLC-MS/MS method was further applied to the pharmacokinetic study of verinurad in rat plasma after oral (2 mg/kg) and intravenous (1 mg/kg) administrations. The pharmacokinetic study revealed that verinurad showed high clearance and high bioavailability (78.1%). To the best of our knowledge, this is the first report of the bioavailability study of verinurad.

Rationale, design, demographics and baseline characteristics of the randomized, controlled, Phase 2b SAPPHIRE study of verinurad plus allopurinol in patients with chronic kidney disease and hyperuricaemia

BACKGROUND

Verinurad is a human uric acid (UA) transporter (URAT1) inhibitor known to decrease serum UA (sUA) levels and that may reduce albuminuria. In a Phase 2a study (NCT03118739), treatment with verinurad + febuxostat lowered urine albumin-to-creatinine ratio (UACR) at 12 weeks by 39% (90% confidence interval 4-62%) among patients with Type 2 diabetes mellitus, hyperuricaemia and albuminuria. The Phase 2b, randomized, placebo-controlled Study of verinurAd and alloPurinol in Patients with cHronic kIdney disease and hyperuRicaEmia (SAPPHIRE; NCT03990363) will examine the effect of verinurad + allopurinol on albuminuria and estimated glomerular filtration rate (eGFR) slope among patients with chronic kidney disease (CKD) and hyperuricaemia.

METHODS

Adults (≥18 years of age) with CKD, eGFR ≥25 mL/min/1.73 m2, UACR 30-5000 mg/g and sUA ≥6.0 mg/dL will be enrolled. Approximately 725 patients will be randomized 1:1:1:1:1 to 12, 7.5 or 3 mg verinurad + allopurinol, allopurinol or placebo. An 8-week dose-titration period will precede a 12-month treatment period; verinurad dose will be increased to 24 mg at Month 9 in a subset of patients in the 3 mg verinurad + allopurinol arm. The primary efficacy endpoint the is change from baseline in UACR at 6 months. Secondary efficacy endpoints include changes in UACR, eGFR and sUA from baseline at 6 and 12 months.

CONCLUSIONS

This study will assess the combined clinical effect of verinurad + allopurinol on kidney function in patients with CKD, hyperuricaemia and albuminuria, and whether this combination confers renoprotection beyond standard-of-care.

Pharmacokinetics, pharmacodynamics, and safety of verinurad with and without allopurinol in healthy Asian, Chinese, and non-Asian participants

Verinurad is a selective inhibitor of uric acid transporter 1 (URAT1). Here, we assessed the safety, pharmacokinetics, and pharmacodynamics of verinurad + allopurinol and verinurad monotherapy in healthy participants. Studies 1 (NCT03836599) and 2 (NCT02608710) were randomized Phase 1 studies. In Study 1, 12 healthy Asian participants received 24 mg verinurad + 300 mg allopurinol or placebo, and 9 healthy Chinese participants received 12 mg verinurad + 300 mg allopurinol. In Study 2, 24 healthy non-Asian male participants received 12 mg verinurad. Safety analyses included assessment of adverse events (AEs). Pharmacokinetic parameters included maximum concentration (Cmax ) and area under plasma concentration-time curve (AUC) over 24 h (AUCτ ). Pharmacodynamic parameters included percentage change from baseline (day -1) in serum uric acid (sUA) and urinary uric acid (uUA). There were no serious AEs or deaths in either study. In Study 1, steady-state geometric mean (gCV%) Cmax and AUCτ values of verinurad after 7 days' dosing were 73.6 (29.0) ng/mL and 478 (18.4) ng·h/mL, respectively, in healthy Asian participants, and 42.0 (40.1) ng/mL and 264 (36.1) ng·h/mL, respectively, in healthy Chinese participants; in Study 2, gCV% values were 36.3 (36.5) ng/mL and 271 (31.0) ng·h/mL, respectively. sUA decreased and uUA excretion increased compared with baseline following verinurad + allopurinol (Study 1) or verinurad (Study 2). When accounting for dose, the steady-state pharmacokinetics of verinurad following multiple dosing were comparable between healthy Asian and Chinese participants and healthy non-Asian participants. Verinurad treatments were well tolerated, including at higher verinurad exposures than previously evaluated after repeated dosing.

U-shaped association of uric acid to overall-cause mortality and its impact on clinical management of hyperuricemia

Serum uric acid (SUA) is significantly elevated in obesity, gout, type 2 diabetes mellitus, and the metabolic syndrome and appears to contribute to the renal, cardiovascular and pulmonary comorbidities that are associated with these disorders. Most previous studies have focused on the pathophysiologic effects of high levels of uric acid (hyperuricemia). More recently, research has also shifted to the impact of hypouricemia, with multiple studies showing the potentially damaging effects that can be caused by abnormally low levels of SUA. Along with these observations, recent inconclusive data from human studies evaluating the treatment of hyperuricemia with xanthine oxidoreductase (XOR) inhibitors have added to the debate about the causal role of UA in human disease processes. SUA, which is largely derived from hepatic degradation of purines, appears to exert both systemic pro-inflammatory effects that contribute to disease and protective antioxidant properties. XOR, which catalyzes the terminal two steps of purine degradation, is the major source of both reactive oxygen species (O2.-, H2O2) and UA. This review will summarize the evidence that both elevated and low SUA may be risk factors for renal, cardiovascular and pulmonary comorbidities. It will also discuss the mechanisms through which modulation of either XOR activity or SUA may contribute to vascular redox hemostasis. We will address future research studies to better account for the differential effects of high versus low SUA in the hope that this will identify new evidence-based approaches for the management of hyperuricemia.

The potential of probiotics in the amelioration of hyperuricemia

Hyperuricemia is a common disease caused by metabolic disorders or the excessive intake of high-purine foods. Persistent hyperuricemia in extreme cases induces gout, and asymptomatic hyperuricemia is probably linked to other metabolic diseases, such as hypertension. The typical damage caused by asymptomatic hyperuricemia includes inflammation, oxidative stress and gut dysbiosis. Probiotics have broad potential applications as food additives, not as drug therapies, in the amelioration of hyperuricemia. In this review, we describe novel methods for potential hyperuricemia amelioration with probiotics. The pathways through which probiotics may ameliorate hyperuricemia are discussed, including the decrease in uric acid production through purine assimilation and XOD (xanthine oxidase) inhibition as well as enhanced excretion of uric acid production by promoting ABCG2 (ATP binding cassette subfamily G member 2) activity, respectively. Three possible probiotic-related therapeutic pathways for alleviating the syndrome of hyperuricemia are also summarized. The first mechanism is to alleviate the oxidation and inflammation induced by hyperuricemia through the inhibition of NLRP3 inflammasome, the second is to restore damaged intestinal epithelium barriers and prevent gut microbiota dysbiosis, and the third is to enhance the innate immune system by increasing the secretion of immunoglobulin A (sIgA) to resist the stimulus by hyperuricemia. We propose that future research should focus on superior strain resource isolation and insight into the cause-effect mechanisms of probiotics for hyperuricemia amelioration. The safety and effects of the application of probiotics in clinical use also need verification.

Discovery of novel verinurad analogs as dual inhibitors of URAT1 and GLUT9 with improved Druggability for the treatment of hyperuricemia

Verinurad (RDEA3170) is a selective URAT1 inhibitor under investigation for the treatment of gout and hyperuricemia. In an effort to further improve the pharmacodynamics/pharmacokinetics of verinurad and to increase the structural diversity, we designed novel verinurad analogs by introducing a linker (e.g. aminomethyl, amino or oxygen) between the naphthalene and the pyridine ring to increase the flexibility. These compounds were synthesized and tested for their in vitro URAT1-inhibitory activity. Most compounds exhibited potent inhibitory activities against URAT1 with IC₅₀ values ranging from 0.24 μM to 16.35 μM. Among them, compound KPH2f exhibited the highest URAT1-inhibitory activity with IC₅₀ of 0.24 μM, comparable to that of verinurad (IC₅₀ = 0.17 μM). KPH2f also inhibited GLUT9 with an IC₅₀ value of 9.37 ± 7.10 μM, indicating the dual URAT1/GLUT9 targeting capability. In addition, KPH2f showed little effects on OAT1 and ABCG2, and thus was unlikely to cause OAT1/ABCG2-mediated drug-drug interactions and/or to neutralize the uricosuric effects of URAT1/GLUT9 inhibitors. Importantly, KPH2f (10 mg/kg) was equally effective in reducing serum uric acid levels and exhibited higher uricosuric effects in a mice hyperuricemia model, as compared to verinurad (10 mg/kg). Furthermore, KPH2f demonstrated favorable pharmacokinetic properties with an oral bioavailability of 30.13%, clearly better than that of verinurad (21.47%). Moreover, KPH2f presented benign safety profiles without causing hERG toxicity, cytotoxicity in vitro (lower than verinurad), and renal damage in vivo. Collectively, these results suggest that KPH2f represents a novel, safe and effective dual URAT1/GLUT9 inhibitor with improved druggabilities and is worthy of further investigation as an anti-hyperuricemic drug candidate.

Discovery of Novel Bicyclic Imidazolopyridine-Containing Human Urate Transporter 1 Inhibitors as Hypouricemic Drug Candidates with Improved Efficacy and Favorable Druggability

Lesinurad is a uricosuric agent for the treatment of hyperuricemia associated with gout, which was found lacking in efficacy and safety. Here, scaffold hopping and molecular hybridization were exploited to modify all the structural components of lesinurad, and 36 novel compounds bearing bicyclic imidazolopyridine core were obtained. In a mouse model of acute hyperuricemia, 29 compounds demonstrated increased serum uric acid (SUA)-reducing activity; SUA was treated with 12, 23, and 29 about fourfold lower compared with that of lesinurad. Moreover, 23 exhibited stronger URAT1 inhibition activity (IC₅₀ = 1.36 μM) than lesinurad (IC₅₀ = 5.54 μM). Additionally, 23 showed favorable safety profiles, and no obvious acute toxicity was observed in Kunming mice under a single dose of 1000 mg·kg^-1. 23 also achieved excellent pharmacokinetic properties with the oral bioavailability of 59.3%. Overall, all the results indicated that 23 is a promising drug candidate in the treatment of hyperuricemia and gout.

CDER167, a dual inhibitor of URAT1 and GLUT9, is a novel and potent uricosuric candidate for the treatment of hyperuricemia

Urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) are important targets for the development of uric acid-lowering drugs. We previously showed that the flexible linkers of URAT1 inhibitors could enhance their potency. In this study we designed and synthesized CDER167, a novel RDEA3710 analogue, by introducing a linker (methylene) between the naphthalene and pyridine rings to increase flexibility, and characterized its pharmacological and pharmacokinetics properties in vitro and in vivo. We showed that CDER167 exerted dual-target inhibitory effects on both URAT1 and GLUT9: CDER167 concentration-dependently inhibited the uptake of [14C]-uric acid in URAT1-expressing HEK293 cells with an IC50 value of 2.08 ± 0.31 μM, which was similar to that of RDEA3170 (its IC50 value was 1.47 ± 0.23 μM). Using site-directed mutagenesis, we demonstrated that CDER167 might interact with URAT1 at S35 and F365. In GLUT9-expressing HEK293T cells, CDER167 concentration-dependently inhibited GLUT9 with an IC50 value of 91.55 ± 15.28 μM, whereas RDEA3170 at 100 μM had no effect on GLUT9. In potassium oxonate-induced hyperuricemic mice, oral administration of CDER167 (10 mg·kg-1 · d-1) for 7 days was more effective in lowering uric acid in blood and significantly promoted uric acid excretion in urine as compared with RDEA3170 (20 mg·kg-1 · d-1) administered. The animal experiment proved the safety of CDER167. In addition, CDER167 displayed better bioavailability than RDEA3170, better metabolic stability and no hERG toxicity at 100 μM. These results suggest that CDER167 deserves further investigation as a candidate antihyperuricemic drug targeting URAT1 and GLUT9.

URAT1-selective inhibition ameliorates insulin resistance by attenuating diet-induced hepatic steatosis and brown adipose tissue whitening in mice

Objective

Accumulating evidence indicates that high uric acid (UA) is strongly associated with obesity and metabolic syndrome and drives the development of nonalcoholic fatty liver disease (NAFLD) and insulin resistance. Although urate transporter-1 (URAT1), which is primarily expressed in the kidneys, plays a critical role in the development of hyperuricemia, its pathophysiological implication in NAFLD and insulin resistance remains unclear. We herein investigated the role and functional significance of URAT1 in diet-induced obese mice.

Methods

Mice fed a high-fat diet (HFD) for 16–18 weeks or a normal-fat diet (NFD) were treated with or without a novel oral URAT1-selective inhibitor (dotinurad [50 mg/kg/day]) for another 4 weeks.

Results

We found that URAT1 was also expressed in the liver and brown adipose tissue (BAT) other than the kidneys. Dotinurad administration significantly ameliorated HFD-induced obesity and insulin resistance. HFD markedly induced NAFLD, which was characterized by severe hepatic steatosis as well as the elevation of serum ALT activity and tissue inflammatory cytokine genes (chemokine ligand 2 (Ccl2) and tissue necrosis factor α (TNFα)), all of which were attenuated by dotinurad. Similarly, HFD significantly increased URAT1 expression in BAT, resulting in lipid accumulation (whitening of BAT), and increased the production of tissue reactive oxygen species (ROS), which were reduced by dotinurad via UCP1 activation.

Conclusions

In conclusion, a novel URAT1-selective inhibitor, dotinurad, ameliorates insulin resistance by attenuating hepatic steatosis and promoting rebrowning of lipid-rich BAT in HFD-induced obese mice. URAT1 serves as a key regulator of the pathophysiology of metabolic syndrome and may be a new therapeutic target for insulin-resistant individuals, particularly those with concomitant NAFLD.

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URAT1 is expressed in the liver and brown adipose tissue other than in the kidneys.

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URAT1-selective inhibitor ameliorates HFD-induced insulin resistance.

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URAT1-selective inhibitor improves NAFLD through the inhibition of Ccl2 and TNFα.

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URAT1-selective inhibitor promotes rebrowning of HFD-induced lipid-rich BAT.

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URAT1 serves as a key regulator of the pathophysiology of metabolic syndrome.

Urate transport in health and disease

Circulation of urate levels is determined by the balance between urate production and excretion, homeostasis regulated by the function of urate transporters in key epithelial tissues and cell types. Our understanding of these physiological processes and identification of the genes encoding the urate transporters has advanced significantly, leading to a greater ability to predict risk for urate-associated diseases and identify new therapeutics that directly target urate transport. Here, we review the identified urate transporters and their organization and function in the renal tubule, the intestinal enterocytes, and other important cell types to provide a fuller understanding of the complicated process of urate homeostasis and its role in human diseases. Furthermore, we review the genetic tools that provide an unbiased catalyst for transporter identification as well as discuss the role of transporters in determining the observed significant gender differences in urate-associated disease risk.

Recent Updates of Natural and Synthetic URAT1 Inhibitors and Novel Screening Methods

Human urate anion transporter 1 (hURAT1) is responsible for the reabsorption of uric acid in the proximal renal tubules and is a promising therapeutic target for treating hyperuricemia. To mitigate the side effects of URAT1-targeted clinical agents such as benzbromarone, there is significant interest in discovering new URAT1 inhibitors and developing technology that can evaluate URAT1 inhibition. This review summarizes the methods for assay of URAT1 inhibition and the progress on the discovery of natural and synthetic URAT1 inhibitors in the past five years.

A brief review of urate transporter 1 (URAT1) inhibitors for the treatment of hyperuricemia and gout: Current therapeutic options and potential applications

Hyperuricemia is a common metabolic condition, cause by increased levels of serum urate (SUA). Reduced excretion of uric acid is reported as the key factor of primary hyperuricemia, accounting for approximately 90% of the cases. Urate transporter 1 (URAT1) is a major protein involved in uric acid reabsorption (about 90%). Therefore, URAT1 inhibitors are considered to be a highly effective and promising class of uricosuric agents for treating hyperuricemia. This review summarizes the development of URAT1 inhibitors for the treatment of hyperuricemia, including approved URAT1 inhibitors, URAT1 inhibitors under development in clinical trials, substances with URAT1 inhibitory effects from derivatives and natural products, and conventional drugs with new uses. This review provides new ideas regarding research on URAT1 inhibitors by introducing the structure, properties, and side effects of chemical drugs, as well as the sources and categories of natural drugs. We also discuss new mechanisms of classic drugs, which may provide guidance to many practicing clinicians. The research and discovery of new inhibitors remain in full swing, and tremendous developments are expected in the field.

Persistent Purine Metabolic Abnormality Induces the Aggravation of Visceral Inflammation and Intestinal Microbiota Dysbiosis in Magang Goose

Gout is a disease involving abnormal purine metabolism that is widespread in mammals and birds. Goose is especially susceptible for gout in early stage. However, a few studies investigated the ontogenetic pattern of goslings with purine metabolic abnormality. Our studies were conducted to investigate whether persistent purine metabolic abnormality would lead to aggravation of visceral inflammation and intestinal microbiota dysbiosis in goose. A total of 132 1-day-old Magang geese were randomly divided into six replicates and fed a high-calcium and protein meal-based diet from 1 to 28 days. The experiment lasted for 28 days. Liver and kidney damages were observed in 14- and 28-day-old Magang geese, and liver inflammation increased with increasing age. In 28-day-old Magang geese, serum CAT and liver GSH-Px activity were significantly reduced. Furthermore, jejunum intestinal barrier was impaired and the abundance of Bacteroides was significantly reduced at the genus level. Collectively, the high-calcium and high-protein (HCP) meal-based diet caused liver and kidney damage in 28-day-old Magang geese, leading to hyperuricemia and gout symptoms, and the intestinal barrier is impaired and the intestinal flora is disrupted.

In Vitro Assessment of the Drug-Drug Interaction Potential of Verinurad and Its Metabolites as Substrates and Inhibitors of Metabolizing Enzymes and Drug Transporters

Verinurad is a selective uric acid transporter 1 (URAT1) inhibitor in development for the treatment of chronic kidney disease and heart failure. In humans, two major acyl glucuronide metabolites have been identified: direct glucuronide M1 and N-oxide glucuronide M8. Using in vitro systems recommended by regulatory agencies, we evaluated the interactions of verinurad, M1, and M8 with major drug-metabolizing enzymes and transporters and the potential for clinically relevant drug-drug interactions (DDIs). The IC50 for inhibition of CYP2C8, CYP2C9, and CYP3A4/5 for verinurad was ≥14.5 µM, and maximum free plasma concentration (Iu,max)/IC50 was <0.02 at the anticipated therapeutic Cmax and therefore not considered a DDI risk. Verinurad was not an inducer of CYP1A2, CYP2B6, or CYP3A4/5. Verinurad was identified as a substrate of the hepatic uptake transporter organic anion-transporting polypeptide (OATP) 1B3. Since verinurad hepatic uptake involved both active and passive transport, there is a low risk of clinically relevant DDIs with OATP, and further study is warranted. Verinurad was a substrate of the efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), and renal transporter organic anion transporter 1 (OAT1), although it is not considered a DDI risk in vivo because of dose-proportional pharmacokinetics (P-gp and BCRP) and limited renal excretion of verinurad (OAT1). M1 and M8 were substrates of multidrug resistance-associated protein (MRP) 2 and MRP4 and inhibitors of MRP2. Apart from verinurad being a substrate of OATP1B3 in vitro, the potential for clinically relevant DDIs involving verinurad and its metabolites as victims or perpetrators of metabolizing enzymes or drug transporters is considered low. SIGNIFICANCE STATEMENT: Drug transporters and metabolizing enzymes have an important role in the absorption and disposition of a drug and its metabolites. Using in vitro systems recommended by regulatory agencies, we determined that, apart from verinurad being a substrate of organic anion-transporting polypeptide 1B3, the potential for clinically relevant drug-drug interactions involving verinurad and its metabolites M1 and M8 as victims or perpetrators of metabolizing enzymes or drug transporters is considered low.

Modulation of Urate Transport by Drugs

BACKGROUND

Serum urate (SU) levels in primates are extraordinarily high among mammals. Urate is a Janus-faced molecule that acts physiologically as a protective antioxidant but provokes inflammation and gout when it precipitates at high concentrations. Transporters play crucial roles in urate disposition, and drugs that interact with urate transporters either by intention or by accident may modulate SU levels. We examined whether in vitro transporter interaction studies may clarify and predict such effects.

METHODS

Transporter interaction profiles of clinically proven urate-lowering (uricosuric) and hyperuricemic drugs were compiled from the literature, and the predictive value of in vitro-derived cut-offs like C_max/IC₅₀ on the in vivo outcome (clinically relevant decrease or increase of SU) was assessed.

RESULTS

Interaction with the major reabsorptive urate transporter URAT1 appears to be dominant over interactions with secretory transporters in determining the net effect of a drug on SU levels. In vitro inhibition interpreted using the recommended cut-offs is useful at predicting the clinical outcome.

CONCLUSIONS

In vitro safety assessments regarding urate transport should be done early in drug development to identify candidates at risk of causing major imbalances. Attention should be paid both to the inhibition of secretory transporters and inhibition or trans-stimulation of reabsorptive transporters, especially URAT1.

Highly permselective uric acid detection using kidney cell membrane-functionalized enzymatic biosensors

Abnormal blood uric acid (UA) levels can lead to its crystallization in the joints, consequently resulting in gout. Accurate detection of UA in the blood is imperative for the early diagnosis of gout. However, electrochemical UA biosensors are vulnerable to antioxidants in the blood, limiting accurate UA detection. To address this issue, we focused on the function of uric acid transporter 1 (URAT1), which is selectively permeable to UA. URAT1 is abundant in the kidney cell membrane (KCM). To apply URAT1 to a sensor, we developed a KCM-coated UA biosensor (called the KCM sensor) that could selectively detect UA through URAT1. The KCM coating in the fabricated KCM sensor was verified via scanning electron microscopy, atomic force microscopy, and confocal microscopy. The KCM sensor enabled the detection of UA in the range of 0-1000 μM, with a limit of detection of 8.5 μM, suggesting that it allows the diagnosis of the early stages of gout. On the other hand, the UA permeability of the KCM sensor was significantly reduced in the presence of a URAT1 inhibitor, implying that URAT1 is a key factor for UA detection. The selectivity of the KCM sensor was demonstrated by measuring the amount for UA in the presence of various antioxidants. Finally, the KCM sensor was capable of measuring UA in human serum and was reproducible with 0.5-1.6% deviation. The UA permeability and selectivity of the KCM sensor were maintained even after 3 weeks of storage.

A semi-mechanistic exposure-response model to assess the effects of verinurad, a potent URAT1 inhibitor, on serum and urine uric acid in patients with hyperuricemia-associated diseases

Verinurad, a uric acid transporter 1 (URAT1) inhibitor, lowers serum uric acid by promoting its urinary excretion. Co-administration with a xanthine oxidase inhibitor (XOI) to simultaneously reduce uric acid production rate reduces the potential for renal tubular precipitation of uric acid, which can lead to acute kidney injury. The combination is currently in development for chronic kidney disease and heart failure. The aim of this work was to apply and extend a previously developed semi-mechanistic exposure–response model for uric acid kinetics to include between-subject variability to verinurad and its combinations with XOIs, and to provide predictions to support future treatment strategies. The model was developed using data from 12 clinical studies from a total of 434 individuals, including healthy volunteers, patients with hyperuricemia, and renally impaired subjects. The model described the data well, taking into account the impact of various patient characteristics such as renal function, baseline fractional excretion of uric acid, and race. The potencies (EC50s) of verinurad (reducing uric acid reuptake), febuxostat (reducing uric acid production), and oxypurinol (reducing uric acid production) were: 29, 128, and 13,030 ng/mL, respectively. For verinurad, symptomatic hyperuricemic (gout) subjects showed a higher EC50 compared with healthy volunteers (37 ng/mL versus 29 ng/mL); while no significant difference was found for asymptomatic hyperuricemic patients. Simulations based on the uric acid model were performed to assess dose–response of verinurad in combination with XOI, and to investigate the impact of covariates. The simulations demonstrated application of the model to support dose selection for verinurad.

The Management of Gout in Renal Disease

Gout, a debilitating inflammatory arthritis, currently affects more than 9 million Americans. Hyperuricemia, the laboratory abnormality associated with the development of gout, also occurs in a significant number of patients with chronic kidney disease (CKD), a condition that affects approximately 14% of the US population. Several recent studies have attempted to provide a definitive link between the presence of hyperuricemia and progression of CKD; however, the treatment of asymptomatic hyperuricemia in CKD is not supported by recent randomized controlled trials. The pharmacology of acute gout flares and urate lowering is complicated in patients who also have evidence of CKD, primarily because of an increased risk of medication toxicity. Recipients of kidney transplants are particularly at risk of debilitating gout and medication toxicity. We review the available data linking CKD, gout, and hyperuricemia, providing practice guidelines on managing gout in CKD patients and kidney transplant recipients. We advocate for much greater involvement of nephrologists in the management of gout in renal patients.

Therapeutic Strategies for the Treatment of Chronic Hyperuricemia: An Evidence-Based Update

This article aims to critically review the evidence on the available therapeutic strategies for the treatment of hyperuricemia. For this reason, several papers were reviewed. Xanthine oxidase inhibitors are the safest and most effective uric acid lowering drugs for the management of chronic hyperuricemia, while the efficacy of uricosuric agents is strongly modulated by pharmacogenetics. Emergent drugs (lesinurad, peglotidase) were found to be more effective for the acute management of refractory hyperuricemia, but their use is supported by a relatively small number of clinical trials so that further well-designed clinical research is needed to deepen their efficacy and safety profile.

Baicalein alleviates hyperuricemia by promoting uric acid excretion and inhibiting xanthine oxidase

BACKGROUND

Insufficient renal urate excretion and/or overproduction of uric acid (UA) are the dominant causes of hyperuricemia. Baicalein (BAL) is widely distributed in dietary plants and has extensive biological activities, including antioxidative, anti-inflammatory and antihypertensive activities.

PURPOSE

To investigate the anti-hyperuricemic effects of BAL and the underlying mechanisms in vitro and in vivo.

METHODS

We investigated the inhibitory effects of BAL on GLUT9 and URAT1 in vitro through electrophysiological experiments and ¹⁴C-urate uptake assays. To evaluate the impact of BAL on serum and urine UA, the expression of GLUT9 and URAT1, and the activity of xanthine oxidase (XOD), we developed a mouse hyperuricemia model by potassium oxonate (PO) injection. Molecular docking analysis based on homology modeling was performed to explain the predominant efficacy of BAL compared with the other test compounds.

RESULTS

BAL dose-dependently inhibited GLUT9 and URAT1 in a noncompetitive manner with IC₅₀ values of 30.17 ± 8.68 μM and 31.56 ± 1.37 μM, respectively. BAL (200 mg/kg) significantly decreased serum UA and enhanced renal urate excretion in PO-induced hyperuricemic mice. Moreover, the expression of GLUT9 and URAT1 in the kidney was downregulated, and XOD activity in the serum and liver was suppressed. The docking analysis revealed that BAL potently interacted with Trp336, Asp462, Tyr71 and Gln328 of GLUT9 and Ser35 and Phe241 of URAT1.

CONCLUSION

These results indicated that BAL exerts potent antihyperuricemic efects through renal UA excretal promotion and serum UA production. Thus, we propose that BAL may be a promising treatment for the prevention of hyperuricemia owing to its multitargeted inhibitory activity.

Structural Insights into the Atomistic Mechanisms of Uric Acid Recognition and Translocation of Human Urate Anion Transporter 1

Background: Human urate transporter 1 (hURAT1) is the most pivotal therapeutic target for treating hyperuricemia. However, the molecular interactions between uric acid and URAT1 are still unknown due to lack of structural details. Methods: In the present study, several methods (homology modeling, sequence alignment, docking, and mutagenesis) were used to explain the atomistic mechanisms of uric acid transport of hURAT1. Results: Residues W357-F365 in the TMD7 and P484-R487 in the TMD11 present in the hURAT1 have unique roles in both binding to the uric acid and causing subsequent structural changes. These residues, located in the transport tunnel, were found to be related to the structural changes, as demonstrated by the reduced V _max values and an unaltered expression of protein level. In addition, W357, G361, T363, F365, and R487 residues may confer high affinity for binding to uric acid. An outward-open homology model of hURAT1 revealed a crucial role for these two domains in the conformational changes of hURAT1. F241 and H245 in TMD5, and R477 and R487 in TMD11 may confer high affinity for uric acid, and as the docking analysis suggests, they may also enhance the affinity for the inhibitors. R477 relation to the structural changes was demonstrated by the V _max values of the mutants and the contribution of positive charge to the uric acid selectivity. Conclusions: W357-F365 in TMD7, P484-R487 in TMD11, and residues F241, H245, and R477 were found to be critical for the translocation and recognition of uric acid.

Effect of Intensive Urate Lowering With Combined Verinurad and Febuxostat on Albuminuria in Patients With Type 2 Diabetes: A Randomized Trial

RATIONALE & OBJECTIVE

Hyperuricemia has been implicated in the development and progression of chronic kidney disease. Verinurad is a novel, potent, specific urate reabsorption inhibitor. We evaluated the effects on albuminuria of intensive urate-lowering therapy with verinurad combined with the xanthine oxidase inhibitor febuxostat in patients with hyperuricemia and type 2 diabetes mellitus (T2DM).

STUDY DESIGN

Phase 2, multicenter, prospective, randomized, double-blind, parallel-group, placebo-controlled trial.

SETTING & PARTICIPANTS

Patients 18 years or older with hyperuricemia, albuminuria, and T2DM.

INTERVENTION

Patients randomly assigned 1:1 to verinurad (9mg) plus febuxostat (80mg) or matched placebo once daily for 24 weeks.

OUTCOMES

The primary end point was change in urinary albumin-creatinine ratio (UACR) from baseline after 12 weeks' treatment. Secondary end points included safety and tolerability and effect on glomerular filtration.

RESULTS

60 patients were enrolled (n=32, verinurad and febuxostat; n=28, placebo). UACRs after treatment with verinurad plus febuxostat were lower than after placebo at 1, 12, and 24 weeks: -38.6% (90% CI, -60.9% to-3.6%), -39.4% (90% CI, -61.8% to-3.8%), and-49.3% (90% CI, -68.2% to-19.0%), respectively. Serum urate levels after treatment with verinurad plus febuxostat were 59.6% and 63.7% lower than after placebo at 12 and 24 weeks, respectively. No clinically meaningful changes were observed in estimated glomerular filtration rate or serum creatinine or serum cystatin C concentrations. Verinurad plus febuxostat was well tolerated.

LIMITATIONS

Sample size and study duration were insufficient to evaluate definitive effects of verinurad plus febuxostat on UACR and glomerular filtration. Generalizability was limited by exclusion of patients with stages 4 and 5 chronic kidney disease.

CONCLUSIONS

Verinurad plus febuxostat reduced albuminuria and lowered serum urate concentrations in patients with T2DM, albuminuria, and hyperuricemia. Definitive assessment of their combined impact on preservation of kidney function awaits larger clinical studies.

FUNDING

This study was supported by AstraZeneca.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT03118739.

Novel Human Urate Transporter 1 Inhibitors as Hypouricemic Drug Candidates with Favorable Druggability

Lesinurad, a human urate transporter 1 (URAT1) inhibitor approved as a medication for the treatment of hyperuricemia associated with gout in 2015, can cause liver and renal toxicity. Here, we modified all three structural components of lesinurad by applying scaffold hopping, bioisosterism, and substituent-decorating strategies. In a mouse model of acute hyperuricemia, 21 of the synthesized compounds showed increased serum uric acid (SUA)-reducing activity; SUA was about 4-fold lower in animals treated with 44, 54, and 83 compared with lesinurad or benzbromarone. In the URAT1 inhibition assay, 44 was over 8-fold more potent than lesinurad (IC₅₀: 1.57 μM vs 13.21 μM). Notably, 83 also displayed potent inhibitory activity (IC₅₀ = 31.73 μM) against GLUT9. Furthermore, we also preliminarily explored the effect of chirality on the potency of the promising derivatives 44 and 54. Compounds 44, 54, and 83 showed favorable drug-like pharmacokinetics and appear to be promising candidates for the treatment of hyperuricemia and gout.

Bioactive Compounds from Plant-Based Functional Foods: A Promising Choice for the Prevention and Management of Hyperuricemia

Hyperuricemia is a common metabolic disease that is caused by high serum uric acid levels. It is considered to be closely associated with the development of many chronic diseases, such as obesity, hypertension, hyperlipemia, diabetes, and cardiovascular disorders. While pharmaceutical drugs have been shown to exhibit serious side effects, and bioactive compounds from plant-based functional foods have been demonstrated to be active in the treatment of hyperuricemia with only minimal side effects. Indeed, previous reports have revealed the significant impact of bioactive compounds from plant-based functional foods on hyperuricemia. This review focuses on plant-based functional foods that exhibit a hypouricemic function and discusses the different bioactive compounds and their pharmacological effects. More specifically, the bioactive compounds of plant-based functional foods are divided into six categories, namely flavonoids, phenolic acids, alkaloids, saponins, polysaccharides, and others. In addition, the mechanism by which these bioactive compounds exhibit a hypouricemic effect is summarized into three classes, namely the inhibition of uric acid production, improved renal uric acid elimination, and improved intestinal uric acid secretion. Overall, this current and comprehensive review examines the use of bioactive compounds from plant-based functional foods as natural remedies for the management of hyperuricemia.

Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids

Enalaprilat is the active metabolite of enalapril, a widely used antihypertension drug. The human organic anion transporter 3 (OAT3), which is highly expressed in the kidney, plays a critical role in the renal clearance of many drugs. While urinary excretion is the primary elimination route of enalaprilat, direct involvement of OAT3 has not been reported so far. In the present study, OAT3-mediated uptake of enalaprilat was first characterized, and the inhibition of OAT3 transport activity was then examined for a number of flavonoid and drug molecules with diverse structures. A varying degree of inhibition potency was demonstrated for flavonoids, with IC₅₀ values ranging from 0.03 to 22.6 µM against OAT3 transport activity. In addition, commonly used drugs such as urate transporter 1 (URAT1) inhibitors also displayed potent inhibition on OAT3-mediated enalaprilat uptake. Pharmacophore and three-dimensional quantitative structure-activity relationship (3D-QSAR) analyses revealed the presence of a polar center and a hydrophobic region involved in OAT3-inhibitor binding. For the polar center, hydroxyl groups present in flavonoids could act as either hydrogen bond donors or acceptors and the number and position of hydroxyl groups were critical drivers for inhibition potency, while carboxyl groups present in some drugs could form ionic bridges with OAT3. The predicted inhibition potencies by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were correlated well with experimental IC₅₀ values. Taken together, the present study identified OAT3-mediated uptake of enalaprilat as an important mechanism for its renal clearance, which may be liable for drug-drug and herb-drug interactions. The established computational models revealed unique structural features for OAT3 inhibitors and could be used for structure-activity relationship (SAR) analysis of OAT3 inhibition. The clinical relevance of the inhibition of OAT3-mediated enalaprilat uptake warrants further investigation, particularly in populations where herbal remedies and drugs are used concomitantly.

Recent approaches to gout drug discovery: an update

INTRODUCTION

Inflammation induced by urate deposition in joints causes gout. Healthy individuals maintain serum levels of urate by balancing urate production/excretion, whereas a production/excretion imbalance increases urate levels. Hyperuricemia is diagnosed when the serum urate level is continuously above 7 mg/dl as the solubility limit, and urate accumulates in the kidneys and joints. Because hyperuricemia increases the risk of gout, therapies aim to eliminate urate deposition to prevent gouty arthritis and kidney injury.

AREAS COVERED

This review discusses the mechanism underlying hyperuricemia with respect to urate production and urate transport, along with urate-lowering therapeutics, including urate synthesis inhibitors, uricolytic enzymes, and uricosuric agents. The authors asses published data on relevant commercial therapy development projects and clinical trials.

EXPERT OPINION

Available treatment options for hyperuricemia are limited. Allopurinol, a urate synthesis inhibitor, is generally administered at a reduced dosage to patients with renal impairment. Some URAT1 inhibitors have an unfavorable side effect profile. A promising strategy for treatment is the use of uricosuric agents that inhibit transporters (e.g. URAT1, URATv1/GLUT9, OAT10) which reabsorb urate from the urine.