OBJECTIVES: Previous clinical trials have demonstrated that gout patients who achieve the target serum urate acid (SUA) level ≤6 mg/dL with urate lowering therapy (ULT) experience a reduction in the frequency of gout flares over time. This finding has not been fully exploited in pharmacoeconomic models of ULTs that associate constant flare rates with SUA levels. The objective of this study was to quantify the long-term rate of decrease in flare frequency among subjects who achieved the target SUA level in the fEbuXostat/allopurinol Comparative Extension Long-term study (EXCEL). METHODS: The EXCEL trial reported the proportion of subjects experiencing ≥1 gout flare requiring treatment by two-month intervals. Binomial regression was used to fit Gompertz and Weibull survival models to the observations at least 6 months after baseline, pooled across treatment arms. Model fit was assessed by a chi-square test of the model deviance. RESULTS: The goodness of fit test for the Gompertz survival model indicated that the model provides an adequate fit to the data (model deviance = 14.14 with 15 degrees of freedom; p=.5146). However, the goodness of fit test for the Weibull survival model indicated an inadequate fit to the data (model deviance = 55.01 with 15 degrees of freedom; p<.0001). The maximum likelihood estimate of the shape parameter of the Gompertz survival model is -0.0906, where time is measured in months. CONCLUSIONS: The long-term (≥6 months after baseline) gout flare results reported in the EXCEL trial can be adequately modeled by a Gompertz survival model, which estimates that the gout flare rate decreased by 9.06% per month for subjects who achieved the target SUA level of ≤6 mg/dL. The results of this analysis may be useful for modeling the long-term clinical and economic outcomes of ULTs in patients with gout.