The activity of AA-193, a new uricosuric agent, in animals

Discovery of a Potent and Orally Bioavailable Xanthine Oxidase/Urate Transporter 1 Dual Inhibitor as a Potential Treatment for Hyperuricemia and Gout

The main uric acid-lowering agents in clinical use for hyperuricemia and gout are xanthine oxidase (XO) inhibitors or urate transporter 1 (URAT1) inhibitors. While these therapies can partially control the disease, they have various limitations. The development of XO/URAT1 dual inhibitors offers the potential to enhance therapeutic potency and reduce toxicity compared with single-target inhibitors. Through scaffold hopping from the XO inhibitor febuxostat (2) and the URAT1 inhibitor probenecid (3), followed by structure-activity relationship (SAR) studies, we identified compound 27 as a potent dual inhibitor of XO and URAT1. Compound 27 demonstrated significant dual inhibition in vitro (XO IC50 = 35 nM; URAT1 IC50 = 31 nM) and exhibited favorable pharmacology and pharmacokinetic (PK) profiles in multiple species including monkeys. Furthermore, toxicity studies in rats and monkeys revealed general safety profiles, supporting that compound 27 emerges as a promising novel drug candidate with potent XO/URAT1 dual inhibition for the treatment of gout.

Main contribution of UGT1A1 and CYP2C9 in the metabolism of UR-1102, a novel agent for the treatment of gout

UR-1102, a novel uricosuric agent for treating gout, has been confirmed to exhibit a pharmacological effect in patients. We clarified its metabolic pathway, estimated the contribution of each metabolic enzyme, and assessed the impact of genetic polymorphisms using human in vitro materials. Glucuronide, sulfate and oxidative metabolites of UR-1102 were detected in human hepatocytes. The intrinsic clearance by glucuronidation or oxidation in human liver microsomes was comparable, but sulfation in the cytosol was much lower, indicating that the rank order of contribution was glucuronidation ≥ oxidation > sulfation. Recombinant UGT1A1 and UGT1A3 showed high glucuronidation of UR-1102. We took advantage of a difference in the inhibitory sensitivity of atazanavir to the UGT isoforms and estimated the fraction metabolised (fm) with UGT1A1 to be 70%. Studies using recombinant CYPs and CYP isoform-specific inhibitors showed that oxidation was mediated exclusively by CYP2C9. The effect of UGT1A1 and CYP2C9 inhibitors on UR-1102 metabolism in hepatocytes did not differ markedly between the wild type and variants.

Uricosuric agents decrease the plasma urate level in rats by concomitant treatment with topiroxostat, a novel xanthine oxidoreductase inhibitor

OBJECTIVES

The aim of this study was to establish the rat model for evaluating hypouricemic effects by some uricosuric agents.

METHODS

Rats were made hyperuricemic by subcutaneous administration of potassium oxonate, a uricase inhibitor, or made hypouricemic by oral administration of topiroxostat, a xanthine oxidoreductase inhibitor. Furthermore, rats were co-treated with topiroxostat and inosine, a urate precursor. In each condition, hypouricemic effects by uricosuric agents were examined.

KEY FINDINGS

In potassium oxonate-treated rats, treatment with uricosuric agents such as FYU-981, F12859 and probenecid showed no hypouricemic effect. On the other hand, in topiroxostat-treated rats, uricosuric agents remarkably lowered plasma urate level compared with topiroxostat treatment alone, with a dose dependency of 30 and 100 mg/kg for FYU-981 and F12859 each. The decrease in the plasma urate level observed in the topiroxostat-treated rats disappeared by further co-treatment with inosine.

CONCLUSIONS

Effects of uricosuric agents on the plasma urate level in rats were sensitive to the rate of urate formation. Induction of slower urate formation by topiroxostat provides valuable model for evaluation of hypouricemic effects by uricosuric agents in rats.

Effects of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) on the serum uric acid level and xanthine oxidase activity in hyperuricemic mice

This study was aimed at evaluating the hypouricemic effect of the anthocyanin-rich purple sweet potato extract (APSPE).

Simiao pill ameliorates urate underexcretion and renal dysfunction in hyperuricemic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Simiao pill is one of the most frequently prescription in traditional Chinese medicine to treat gout and hyperuricemia.

AIM OF THE STUDY

We investigated the effects of Simiao pill on urate excretion and renal function and examined whether renal organic ion transporters are involved in potassium oxonate-induced hyperuricemic mice.

MATERIALS AND METHODS

Water extract of Simiao pill at 507, 1014 and 2028mg/kg was orally administered to hyperuricemic and normal mice for 7 days, and allopurinol (5mg/kg) was given as a positive control. Serum and urine levels of uric acid and creatinine, and fractional excretion of uric acid (FEUA) were measured in hyperuricemic and normal mice treated with Simiao pill and allopurinol. Simultaneously, the mRNA and protein levels of mouse urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9) and organic anion transporter 1 (mOAT1) and organic cation/carnitine transporters (mOCT1, mOCT2, mOCTN1 and mOCTN2) in the kidney were analyzed by semi-quantitative RT-PCR and Western blotting methods, respectively.

RESULTS

Simiao pill significantly reduced serum uric acid levels and increased FEUA dose-dependently in hyperuricemic mice. And it effectively reversed oxonate-induced alterations in renal mURAT1, mGLUT9 and mOAT1 mRNA and protein levels, resulting in the enhancement of renal urate excretion in mice. Moreover, Simiao pill decreased serum creatinine levels, as well as increased renal mOCT1, mOCT2, mOCTN1 and mOCTN2 mRNA and protein levels, leading to improve renal dysfunction in this model.

CONCLUSION

These findings suggest that Simiao pill processes uricosuric and nephroprotective actions by regulating renal organic ion transporters in hyperuricemic animals.

Mechanism of the uricosuric action of E3040, a drug used to treat inflammatory bowel disease II: study using DBA/2N mice

In the initial phase of clinical studies, it was shown that E3040, a new type of anti-inflammatory drug, reduced plasma uric acid levels. The present study describes a comparison of the excretion of uric acid in the proximal tubules of the kidney after administration of E3040 and its conjugates, sulphate and glucuronide, with that of other general uricosuric agents in DBA/2N mice. The aim of this investigation was to elucidate the mechanism for the uricosuric action of E3040. It was found that E3040 increased the excretion rate of uric acid in a dose-dependent manner, and the excretion rates following 10 and 50 mg/kg doses were significantly greater than that of the control group. The paradoxical effect observed with probenecid was not seen in the E3040 dose-response curve for the uric acid excretion rate. Neither E3040-sulphate nor E3040-glucuronide increased the excretion rate of uric acid significantly, even at a high dose, such as 200 mg/kg. In the pyrazinoic acid suppression test, the uric acid excretion rate after concomitant administration of E3040 and pyrazinoic acid was significantly higher than that after administration of pyrazinoic acid alone, and the rate after concomitant administration was 30% of the level after administration of E3040 alone. The change in the excretion rate of uric acid after concomitant administration of E3040 and pyrazinoic acid was similar to that of AA193, a selective inhibitor of the presecretory reabsorption of uric acid. From these results, it appears that E3040 may exert its uricosuric action by reducing the presecretory reabsorption of uric acid rather than increasing its secretion.

Mechanism of the uricosuric action of the anti-inflammatory drug E3040 used to treat inflammatory bowel disease I: study using a rat model of hyperuricemia

E3040, a new class of anti-inflammatory drug, was found to reduce the plasma uric acid level in the first phase of clinical studies. In the present study, the mechanism of the uricosuric action of E3040 was investigated using the hyperuricemia model rat. The fractional excretion of uric acid (FEurate), an indicator of the excretion of uric acid in the renal tubules, at 30, 60 and 90 min after administration of E3040 (50 mg kg(-1)) was significantly elevated as compared with that in the control. This elevation of the FEurate by E3040 was dose-dependent. Although the FEurate was elevated spontaneously 30 min after administration of E3040-sulfate (E-Sul) and glucuronide (E-Glu) (100 mg kg(-1), respectively), the value was not significantly different from the control. Based on these results, it was suggested that E3040 has a uricosuric action, probably in the proximal tubules, and the uricosuric action after administration of E3040 may be mainly due to the parent drug. Concerning the tissue distribution, the kidney concentration of E-Sul after i.v. administration of the E3040 (50 mg kg(-1)) was higher than that of the parent drug (kidney/plasma ratio approximately 2).

The uricosuric effect in rats of E5050, a new derivative of ethanolamine, involves inhibition of the tubular postsecretory reabsorption of urate

N-[3-[4'-(2",6"-Dimethylheptyl)phenyl]butanoyl]ethanolamine (E5050), a newly synthesized compound, was shown recently to induce uricosuria in humans via inhibition of the postsecretory reabsorption of urate. We examined the effects of this compound on urate excretion in rats loaded with oxonate and compared these effects with those of the uricosuric drugs trichlormethiazide and probenecid. When administered i.p., E5050 (0.3-15 mg/kg) increased the urinary excretion rate of urate and the ratio of urate clearance to inulin clearance in a dose-dependent manner, while the urine volume increased only slightly, and the glomerular filtration rate and plasma urate level were not changed. No paradoxical effect on urate excretion was observed. In contrast, trichlormethiazide and probenecid had a biphasic effect on urate excretion. In a pyrazinoic acid suppression test, the uricosuric effect of E5050 was completely inhibited by pretreatment with pyrazinoic acid. In a phenolsulfonphthalein (PSP) test, E5050 did not affect urinary PSP excretion, while probenecid strongly decreased such excretion. Thus, E5050 also appears to be uricosuric in rats.

Hypouricemic and uricosuric actions of AA-193 in a hyperuricemic rat model

In normal rats, consecutive administrations of AA-193 for 7 days maintained the dose-dependent uricosuric activity without significant changes of the plasma urate level. In clearance studies, AA-193 produced an increase in the fractional excretion of urate (FEua) namely an inhibition of the net urate reabsorption in the nephron, which was probably dependent on the plasma concentration of the agent. During in vitro studies, 1 mmol/L AA-193 had no effect on liver uricase activity and 0.2 mmol/L AA-193 did not inhibit xanthine dehydrogenase activity. Therefore, it is unlikely that AA-193 at physiologic doses has a significant effect on either the production or degradation of urate. To assess the hypouricemic effect of AA-193 derived from its uricosuric effect, we used uricase-inhibited rats produced by oxonate feeding. In the hyperuricemic rat model, consecutive administrations of AA-193 for 7 days increased urate excretion and decreased the plasma urate level. We conclude that AA-193 has a hypouricemic effect caused by increases in urate excretion in hyperuricemic rats.

Uricosurics inhibit urate transporter in rat renal brush border membrane vesicles

It has been proposed that a urate-anion exchanger system in brush border membrane vesicles (BBMV), which mediates hydroxyl ion (OH-) gradient-dependent urate uptake, is the most likely route for the mediation of urate transport in the first step of urate reabsorption in the proximal tubules. Luminal drugs which inhibit urate reabsorption would inhibit the transport of urate into the cell by blocking the urate-anion exchanger. To confirm this hypothesis, we investigated the inhibitory effects of well-known uricosuric drugs on the OH-/urate exchange in BBMV. The rank order of potency was benzbromarone greater than tienilic acid greater than sulfinpyrazone greater than probenecid, which is consistent with clinical doses in man. AA-193 (5-chloro-7,8-dihydro-3-phenylfuro[2,3-g]-1,2-benzisoxazole-7-carb oxylic acid), an excellent candidate for a uricosuric, exerted the most potent inhibition on urate uptake (Ki = 0.12 microM). In contrast with that by stilbene disulfonates, the inhibition by AA-193 or benzbromarone was reversible.