Pegloticase in Combination With Methotrexate in Patients With Uncontrolled Gout: A Multicenter, Open-label Study (MIRROR)

Objective. To examine the efficacy and safety of pegloticase in combination with methotrexate (MTX) in patients with uncontrolled gout in an exploratory, open-label clinical trial (ClinicalTrials.gov: NCT03635957) prior to a randomized, controlled trial. Methods. A multicenter, open-label efficacy and safety study of pegloticase with MTX co-treatment was conducted in patients with uncontrolled gout. Patients were administered oral MTX (15 mg/week) and folic acid (1 mg/day) 4 weeks prior to and throughout pegloticase treatment. The primary study outcome was the proportion of responders, defined as serum uric acid (sUA) < 6 mg/dL for >= 80% of the time during Month 6 (Weeks 20, 22, and 24). All analyses were performed on a modified intent-to-treat population, defined as patients who received >= 1 pegloticase infusion. Results. Seventeen patients were screened and 14 patients (all men, average age 49.3 +/- 8.7 years) were enrolled. On Day 1, mean sUA was 9.2 +/- 2.5 mg/dL, and 12 of the 14 patients had visible tophi. At the 6-month timepoint, 11/14 (78.6%, 95% CI 49.2-95.3%) met the responder definition, with 3 patients discontinuing after meeting protocol-defined treatment discontinuation rules (preinfusion sUA values > 6 mg/dL at 2 consecutive scheduled visits). All patients tolerated MTX. No new safety concerns were identified. Conclusion. In this study, an increased proportion of patients maintained therapeutic response at 6 months when treated concomitantly with MTX and pegloticase as compared to the previously reported 42% using pegloticase alone. These results support the need for a randomized study of MTX or placebo with pegloticase to validate these open-label findings.