The effect of small dose of topiroxostat on serum uric acid in patients receiving hemodialysis

Drug-Induced Hypouricemia

Hypouricemia is defined as a serum uric acid concentration of ≤ 2.0 mg/dL or 119 μmol/L. Hypouricemia may occur secondarily to a number of underlying conditions, including severe hepatocellular disease, neoplasia, defective renal tubular reabsorption of uric acid, inherited metabolic defect in purine metabolism, and drugs. Medications are an important cause of hypouricemia. They can cause hypouricemia by a variety of mechanisms. Drug-induced hypouricemia mostly occurs as overtreatment of hyperuricemia by urate-lowering therapies including xanthine oxidase inhibitors, uricosuric agents and uricases. Drugs not used in the treatment of gout may also lead to a decrease of uric acid levels. In this literature review, medications leading to hypouricemia are summarized with regard to their mechanism of action and clinical significance.

Discovery of derivatives from Spartina alterniflora-sourced moiety as xanthine oxidase inhibitors to lower uric acid

In this work, hit compounds Spartinin F1-F20 sharing the Spartina alterniflora-sourced ferulic acid backbone were synthesized and evaluated on inhibiting xanthine oxidase and lowering uric acid level. The top hit Spartinin F2 exhibited inhibition percentages at 10 μM dosage as high as 84.48 (higher than that of the positive control allopurinol) and low cyto-toxicity. Spartinin F2 inferred potential efficiency in lowering the serum UA level (from 631.6 μM to 295.0 μM), which was comparable with allopurinol (to 309.2 μM). Spartinin F2 was also beneficial for other serum indexes. The bioavailability of Spartinin F2 was 63.71% from the preliminary pharmacokinetics test and the molecular docking simulation indicated that except for retaining the hydrogen bonds with the key residues such as THR 1010 and LYS 771, the introduction of the π-sulfur interactions via the sulfonate might also be beneficial for developing more potent XO inhibitors.

Efficacy of Xanthine Oxidase Inhibitors in Lowering Serum Uric Acid in Chronic Kidney Disease: A Systematic Review and Meta-Analysis

Objective: Current guidelines for gout recommend a treat-to-target approach with serum uric acid (SUA). However, there is little evidence for the dose-dependent effects of urate-lowering therapy (ULT). Herein, we analyzed the reported SUA-lowering effect and SUA target achievement differences for various doses of xanthine oxidase inhibitors. Methods: Approved ULT drugs were selected from the FDA Drug Database. We included prospective randomized controlled trials of ULT drugs from ClinicalTrials.gov, articles published in the journal “Drugs”, and Embase, a literature database. A meta-analysis was performed to determine the ability of different ULT drugs and doses to lower and maintain a target SUA < 6 mg/dL. Results: We identified 35 trials including 8172 patients with a baseline SUA of 8.92 mg/dL. The allopurinol, febuxostat, and topiroxostat showed dose-proportional SUA-lowering responses. Compared with allopurinol 300 mg daily, febuxostat 80 mg daily and 120 mg daily more effectively maintained SUA < 6 mg/dL. Conclusion: Allopurinol, febuxostat, and topiroxostat showed dose-proportional ability to lower and achieve a target SUA < 6 mg/dL. Significance and Innovations. We showed dose-dependent SUA lowering effects of allopurinol, febuxostat, and topiroxostat. Febuxostat is effective at ULT compared to allopurinol and could be potentially offered as an alternative agent when patients (1) have CKD, (2) have the human leukocyte antigen HLA-B*5801 allele, and (3) become refractory to allopurinol. Gradual allopurinol dose increase with a lower starting dose is needed in CKD.

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.

Clinical Effects of Xanthine Oxidase Inhibitors in Hyperuricemic Patients

This review aims to critically present the available clinical evidence supporting the treatment of chronic hyperuricemia with xanthine oxidase inhibitors. For this reason, the studies published on uric acid (UA)-lowering drugs in the English language from 2000 to August 2019 have been carefully reviewed. The terms "serum uric acid," "xanthine oxidase," "allopurinol," "febuxostat," and "topiroxostat" were incorporated into an electronic search strategy, alone and in combinations, in both MEDLINE (National Library of Medicine, Bethesda, MD) and the Cochrane Register of Controlled Trials (The Cochrane Collaboration, Oxford, UK). Even if new urate-lowering drugs seem of particular efficacy for acute treatment of refractory hyperuricemia, their use is supported by relatively small clinical evidence. On the contrary, large long-term clinical trials have demonstrated that xanthine oxidase inhibitors (XOIs, namely, allopurinol and febuxostat) are effective, safe, and relatively well-tolerated in most of the patients. They have mainly been tested in the elderly, in patients affected by chronic diseases such as heart failure and cancer, and in patients taking a large number of drugs, confirming their safety profile. Recent data also show that they could exert some positive effects on vascular health, renal function, and glucose metabolism. Their cost is also low. In conclusion, XOIs remain the first choice of UA-lowering drug for chronic treatment.

Safety and tolerability of available urate-lowering drugs: a critical review

INTRODUCTION

Urate-lowering therapy (ULT) is the cornerstone of gout management, which is a widespread chronic illness characterized by hyperuricemia, arthropathy, tophus development, and urolithiasis. Since asymptomatic increased serum urate levels are associated with a higher risk of cardiovascular, renal and metabolic disorders, a larger use of ULTs in the general population is expected in the near future.

AREAS COVERED

This review will focus on the safety and tolerability profile of the available urate-lowering drugs: xanthine oxidase inhibitors (XOIs), uricosuric agents and injectable uricases.

EXPERT OPINION

Older drugs for ULT like allopurinol are well studied and extensively described from typical adverse effects (mild skin rash) to unusual fatal reactions, while febuxostat seems to be overall well tolerated. More evidence is required to define the safety profile of topiroxostat, arhalofenate, tranilast, and sulfinpyrazone. Furthermore, there are some unanswered questions about the pharmacological interactions of probenecid and the hepatotoxicity of benzbromarone. Despite a limited use in clinical practice, combination therapy with lesinurad or verinurad and XOI is not frequently accompanied by side effects. Rasburicase and pegloticase are usually well tolerated with some specific exceptions. Before prescribing UL drugs, physicians should take into account their safety profile tailoring the treatment on the patient characteristics.