Predicting Response or Non-response to Urate-Lowering Therapy in Patients with Gout

Predictors of Inadequate Serum Urate Response to Low-Dose Febuxostat in Male Patients with Gout

Objective

This study aimed to understand predictors of inadequate response (IR) to low-dose febuxostat treatment based on clinical variables.

Methods

We pooled data from 340 patients of an observational cohort and two clinical trials who received febuxostat 20 mg/day for at least 3 months. IR was defined as failure to reach the target serum urate level (sUA<6 mg/dL) at any time point during 3 months treatment. The potential predictors associated with short- or mid-term febuxostat IR after pooling the three cohorts were explored using mixed-effect logistic analysis. Machine learning models were performed to evaluate the predictors for IR using the pooled data as the discovery set and validated in an external test set.

Results

Of the 340 patients, 68.9% and 51.8% were non-responders to low-dose febuxostat during short- and mid-term follow-up, respectively. Serum urate and triglyceride (TG) levels were significantly associated with febuxostat IR, but were also selected as significant features by LASSO analysis combined with age, BMI, and C-reactive protein (CRP). These five features in combination, using the best-performing stochastic gradient descent classifier, achieved an area under the receiver operating characteristic curve of 0.873 (95% CI [0.763, 0.942]) and 0.706 (95% CI [0.636, 0.727]) in the internal and external test sets, respectively, to predict febuxostat IR.

Conclusion

Response to low-dose febuxostat is associated with early sUA improvement in individual patients, as well as patient age, BMI, and levels of TG and CRP.

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.

Behavioral Characteristics of Gout Patients and Their Impact on the Results of Urate Lowering Therapy

Background. Gout is frequently accompanied by hypertension, obesity, and/or impaired glucose tolerance, which are often complicated with heavy smoking and dietary violations, especially in male patients.

Objective. To determine the behavioral characteristics of gout patients that could impact the results of urate lowering therapy.

Subjects and methods. The relationship between behavioral characteristics and results of urate lowering therapy were investigated in 74 male gout patients of Chengdu Rheumatism Hospital. The results of treatment were evaluated using serum uric acid contents before and after treatment, VAS pain score before and after treatment. Behavioral characteristics for the last ten years (smoking status, daily volume of drinking water, etc.) were accessed by means of retrospective survey.

Results. In gout patients with poor treatment response, serum uric acid at the beginning of the treatment was already significantly lower (365.76 ± 163.06 μmol/L); this trend was also noted in a “slow progress” group, while patients with higher serum uric acid before treatment had notably better response to urate lowering therapy. During further analysis age negatively correlated with serum uric acid (r = –0.328; p = 0.002) and uric acid clearance ratio (r = –0.299; p = 0.002).

In patients with uric acid clearance ratio above 40 % the prevalence of kidney diseases (stones or dysfunction) was significantly lower compared to other groups. There was no significant influence of hypertension, diabetes mellitus, fatty liver or hyperlipidaemia on uric acid clearance ratio (p > 0.05).

Amount of drinking water also influenced the serum uric acid clearance ratio. Bigger amount of patients in the “fast progress” group (40.0 % compared to 30.44 and 25.0 %) tended to drink more water.

Conclusion. In most gout patients, serum uric acid levels before treatment acted as the reliable predictor of good response to urate lowering therapy. Treatment response (serum uric acid clearance ratio) correlated positively with the hyperuricemia and drinking sufficient amounts of water, negatively – with prolonged smoking (more than 10 years) and age.

Predictors of poor response to urate-lowering therapy in patients with gout and hyperuricemia: a post-hoc analysis of a multicenter randomized trial

INTRODUCTION

Clinical guidelines have recommended a target of serum uric acid (SUA) level below 6.0 mg/dL for the urate-lowering therapy (ULT) of gout patients, but there are still a high proportion of patients failing to achieve the therapeutic target above. This study aimed to identify possible predictors of poor response to ULT in gout patients.

METHODS

We performed a post-hoc analysis of a multicenter randomized double-blind trial which assessed the efficacy of febuxostat in patients with hyperuricemia (serum urate level ≥ 8.0 mg/dL) and gout. Demographic characters and baseline data including SUA levels were collected. Poor response to ULT was defined as average SUA after ULT was more than 6.0 mg/dL. Factors associated with poor response to ULT in gout patients were analyzed, and multivariate logistic regression analysis was also carried out to find out those independent predictors.

RESULTS

A total of 370 patients were enrolled in this post-hoc analysis. Compared with those with good response to ULT, patients with poor response to ULT had younger age (P < 0.001), higher proportion of obesity (P = 0.003), higher proportion of statins use (P = 0.019), higher body mass index (BMI) (P < 0.001), higher baseline SUA (P < 0.001), higher proportion of males (P = 0.001), higher alanine transaminase (P < 0.001), higher aspartate transaminase (P = 0.017), higher total cholesterol (P = 0.005), higher triglyceride (P = 0.042), and higher low density lipoprotein (P = 0.037). Multivariate logistic regression analysis showed that younger age (odds ratio (OR) = 0.965, 95% CI 0.943-0.987, P = 0.002), higher BMI (OR = 1.133, 95% CI 1.049-1.224, P = 0.001), higher baseline SUA (OR = 1.006, 95% CI 1.002-1.009, P = 0.001), and no application of febuxostat therapy (OR = 0.41, 95% CI 0.25-0.68, P < 0.001) were independent predictors of poor response to ULT in patients with gout.

CONCLUSION

In patients with gout and hyperuricemia, younger age, higher BMI, and higher baseline SUA are predictors of poor response to ULT. These findings could help physicians better identify patients who may fail in ULT and give individualized treatment precisely.

TRIAL REGISTRATION

The trial was registered at chinadrugtrials.org.cn in 2012 (CTR20130172).Key Points• A post-hoc analysis of a multicenter randomized double-blind trial which assessed the efficacy of febuxostat in patients with hyperuricemia and gout was performed.• Multivariate logistic regression analysis showed that younger age, higher BMI, and higher baseline SUA are predictors of poor response to urate-lowering therapy.

Genome-Wide Association and Functional Studies Reveal Novel Pharmacological Mechanisms for Allopurinol

Allopurinol, which lowers uric acid (UA) concentration, is increasingly being recognized for its benefits in cardiovascular and renal disease. However, response to allopurinol is variable. We gathered samples from 4,446 multiethnic subjects for a genome-wide association study of allopurinol response. Consistent with previous studies, we observed that the Q141K variant in ABCG2 (rs2231142), which encodes the efflux pump breast cancer resistance protein (BCRP), associated with worse response to allopurinol. However, for the first time this association reached genome-wide level significance (P = 8.06 × 10^-11 ). Additionally, we identified a novel association with a variant in GREM2 (rs1934341, P = 3.22 × 10^-6 ). In vitro studies identified oxypurinol, the active metabolite of allopurinol, as an inhibitor of the UA transporter GLUT9, suggesting that oxypurinol may modulate UA reabsorption. These results provide strong evidence for a role of BCRP Q141K in allopurinol response, and suggest that allopurinol may have additional hypouricemic effects beyond xanthine oxidase inhibition.