Pegloticase and Methotrexate Co-administered in Participants With Uncontrolled Gout Who Previously Failed Pegloticase Monotherapy

All participants who meet eligibility criteria at Screening will begin once-weekly subcutaneous (SC) MTX Run-in period. Participants must be able to tolerate MTX at a minimum dose of 15 mg during the 6-week MTX Run-in Period to be eligible to participate in the Pegloticase + MTX Treatment Period. All participants who meet the inclusion/exclusion criteria and complete the MTX Run-in Period will be considered enrolled participants. During the Pegloticase + MTX Treatment Period, pegloticase 8 mg will be administered IV every 2 weeks and MTX SC weekly. Two sequential cohorts of participants will be enrolled in this trial. Cohort 1 is targeted to enroll 10 participants who previously failed to maintain sUA response with pegloticase monotherapy and stopped pegloticase treatment without a history of pegloticase-related infusion reaction. If the safety assessment during Cohort 1 indicates that the pegloticase infusions are well tolerated, then the trial can begin enrolling Cohort 2 for 20 participants who failed to maintain sUA response with pegloticase monotherapy with or without a history of pegloticase-related clinically mild IRs. Study acquired from Horizon in 2024.