Effect of Clinical Typing on Serum Urate Targets of Benzbromarone in Chinese Gout Patients: A Prospective Cohort Study

Hyperuricemia Subtypes Classified According to Renal Uric Acid Handling Manifesting Distinct Phenotypic and Genetic Profiles in People With Gout

OBJECTIVE

Hyperuricemia can be stratified into four subtypes according to renal uric acid handling. The aim of this study was to comprehensively describe the biologic characteristics (including genetic background) of clinically defined hyperuricemia subtypes in two large geographically independent gout cohorts.

METHODS

Hyperuricemia subtype was defined as renal uric acid overload (ROL), renal uric acid underexcretion (RUE), combined, or renal normal. Twenty single nucleotide polymorphisms (SNPs) previously identified as gout risk loci or associated with serum urate (SU) concentration in the East Asian population were genotyped. Weighted polygenic risk scores were calculated to assess the cumulative effect of genetic risks on the subtypes.

RESULTS

Of the 4,873 participants, 8.8% had an ROL subtype, 60.9% RUE subtype, 23.1% combined subtype, and 7.2% normal subtype. The ROL subtype was independently associated with older age at onset, lower SU, tophi, and diabetes mellitus; RUE was associated with lower body mass index (BMI) and non-diabetes mellitus; the combined subtype was associated with younger age at onset, higher BMI, SU, estimated glomerular filtration rate (eGFR), and smoking; and the normal subtype was independently associated with older age at onset, lower SU, and eGFR. Thirteen SNPs were associated with gout with 6 shared loci and subtype-dependent risk loci patterns. High polygenic risk scores were associated with ROL subtype (odds ratio [OR] = 9.63, 95% confidence interval [95% CI] 4.53-15.12), RUE subtype (OR = 2.18, 95% CI 1.57-3.03), and combined subtype (OR = 6.32, 95% CI 4.22-9.48) compared with low polygenic risk scores.

CONCLUSION

Hyperuricemia subtypes classified according to renal uric acid handling have subtype-specific clinical and genetic features, suggesting subtype-unique pathophysiologic mechanisms.

Superiority of Low-Dose Benzbromarone Add-On to Low-Dose Febuxostat Compared With Febuxostat Monotherapy in Gout With Combined-Type Hyperuricemia

OBJECTIVE

There is an unmet need for simpler urate-lowering therapy (ULT) regimens that achieve the serum urate target and improve the overall quality of gout care. We report a comparative effectiveness trial of febuxostat monotherapy versus benzbromarone add-on to low-dose febuxostat in gout specifically with combined renal urate underexcretion and overload.

METHODS

A prospective randomized trial was conducted on patients with combined-type hyperuricemia and estimated glomerular filtration rate >60 mL/min/1.73 m2 1:1 randomly assigned to febuxostat and benzbromarone combination therapy (initially febuxostat at 20 mg/day, with benzbromarone at 25 mg/day added onto 20 mg/day of febuxostat if not at target) or febuxostat monotherapy (initially 20 mg/day, escalating to 40 mg/day if not at target). The primary end point at 12 weeks was the proportion achieving a serum urate (SU) level <360 μmol/L. Other outcomes included altered liver and kidney function, new-onset urolithiasis, and gout flares.

RESULTS

There were 250 participants randomized; 219 completed 12-week treatment. More patients in the febuxostat and benzbromarone combination group achieved the SU target compared to patients in the febuxostat monotherapy group (75.5% vs 47.7%; odds ratio 3.37 [95% confidence interval 1.90-5.98]). Safety profiles were comparable between the two groups.

CONCLUSION

Simply adding on low-dose benzbromarone (25 mg/day) to low-dose (20 mg/day) febuxostat showed superior urate lowering compared to febuxostat monotherapy in gout with a combined-type hyperuricemia. For selected patients, expedited achievement of the SU target in more than 75% of patients using one titration step and low xanthine oxidase inhibitor and uricosuric doses is a potential alternative to standard ULT regimens.

Response to febuxostat according to clinical subtypes of hyperuricemia: a prospective cohort study in primary gout

BACKGROUND

While xanthine oxidase inhibitors target uric acid production, renal urate underexcretion is the predominant subtypes in gout. This study was to compare treatment response to the XOI febuxostat in a gout cohort according to clinical subtypes of hyperuricemia.

METHODS

A prospective cohort study was conducted to compare the efficacy and safety of febuxostat (initially 20 mg daily, escalating to 40 mg daily if not at target) in 644 gout patients with the three major clinical subtypes for 12 weeks. Hyperuricemia was defined as the renal overload subtype, the renal underexcretion subtype, or the combined subtype based on UUE > or ≤ 600 mg/d/1.73 m2 and FEUA < or ≥ 5.5%. The primary endpoint was the rate of achieving serum urate (SU) < 6 mg/dL at week 12.

RESULTS

Fewer participants with combined subtype achieved the SU target, 45.5% compared with 64.8% with overload subtype (P = 0.007), and 56.6% with underexcretion subtype (P = 0.022). More participants with combined subtype (82%) had febuxostat escalated to 40 mg than those with overload (62%, P = 0.001) or underexcretion subtype (68%, P = 0.001). In all participants, combined subtype hyperuricemia (OR = 0.64, 95%CI 0.41-0.99, P = 0.048) and baseline SU (OR = 0.74, 95%CI 0.62-0.89, P = 0.001) were independently associated with lower rates of achieving SU target.

CONCLUSIONS

People with combined subtype have a lower response to febuxostat, compared to those with either overload or underexcretion subtype. Assessment of hyperuricemia subtype may provide useful clinical data in predicting febuxostat response.