Infusion Duration Study To Assess Tolerability of Pegloticase Administered With a Shorter Infusion Duration in Subjects with Uncontrolled Gout Receiving Methotrexate

1. Adult men or women ≥18 years of age. 2. Uncontrolled gout, defined as meeting the following criteria: ° Hyperuricemia during the screening period defined as sUA ≥6 mg/dL ° Failure to maintain normalization of sUA with xanthine oxidase inhibitors at the maximum medically appropriate dose, or with intolerable side effects or a contraindication to xanthine oxidase inhibitor therapy based on medical record review or subject interview. ° Symptoms of gout including at least 1 of the following: - Presence of at least one tophus - Recurrent flares defined as 2 or more flares in the past 12 months prior to screening - Presence of chronic gouty arthritis 3. Willing to discontinue all oral urate-lowering therapy at least 7 days prior to MTX dosing at Week -4 and remain off of urate lowering therapy when receiving pegloticase infusions during the study.

1. Severe chronic or recurrent bacterial infections, such as recurrent pneumonia or chronic bronchiectasis. 2. Current or chronic treatment with systemic immunosuppressive agents such as MTX, azathioprine, or mycophenolate mofetil; prednisone ≥10 mg/day or equivalent dose of other corticosteroid on a chronic basis (defined as 3 months or longer) would also meet exclusion criteria. 3. Glucose-6-phosphate dehydrogenase (G6PD) deficiency (tested at Screening Visit). 4. Severe chronic renal impairment (estimated glomerular filtration rate <40 mL/min/1.73 m2) at the Screening Visit based on 4 variable-Modification of Diet in Renal Disease [MDRD] formula or currently on dialysis. 5. Non-compensated congestive heart failure or hospitalization for congestive heart failure or treatment for acute coronary syndrome (myocardial infarction or unstable angina) within 3 months of the Screening Visit, or current uncontrolled arrhythmia, or current uncontrolled blood pressure (BP) (>160/100 mmHg) prior to Week -4. 6. Pregnant, planning to become pregnant, breastfeeding, planning to impregnate female partner, or not on an effective form of birth control, as determined by the Investigator. 7. Prior treatment with pegloticase (KRYSTEXXA), another recombinant uricase (rasburicase), or concomitant therapy with a polyethylene glycol-conjugated drug. 8. Currently receiving systemic or radiologic treatment for ongoing cancer. 9. History of malignancy within 5 years other than non-melanoma skin cancer or in situ carcinoma of cervix.