Combination Treatment Study in Subjects With Tophaceous Gout With Lesinurad and Febuxostat

Inclusion Criteria: * Subject is able to understand the study procedures, the risks involved and willing to provide written informed consent before the first study related activity. * Subject is willing to adhere to the visit/protocol schedules. * Subject meets the diagnosis of gout as per the American Rheumatism Association * Criteria for the Classification of Acute Arthritis of Primary Gout. * Subject meets one of the following criteria: * Subjects who are not currently taking an approved ULT must have an sUA value of ≥ 8 mg/dL (476 µmol/L). * Subjects entering the study on a medically appropriate dose of febuxostat or allopurinol must have an sUA value of ≥ 6.0 mg/dL (357 µmol/L). * Subject must be able to take gout flare prophylaxis with colchicine or non-steroidal anti-inflammatory drug (NSAID) (including Cox-2 selective NSAID) ± PPI. * Subject with at least 1 measurable tophus on the hands/wrists and/or feet/ankles ≥ 5 mm and ≤ 20 mm in the longest diameter. * Body mass index (BMI) \< 45 kg/m2 Exclusion Criteria: * Subject with known hypersensitivity or allergy to febuxostat. * Subject who is taking any approved urate-lowering medication other than allopurinol or febuxostat that is indicated for the treatment of gout within 8 weeks of the Screening Visit. * Subject who previously received pegloticase. * Subject who consumes more than 14 drinks of alcohol per week (eg, 1 drink = 5 oz \[150 mL\] of wine, 12 oz \[360 mL\] of beer, or 1.5 oz \[45 mL\] of hard liquor). * Subject with a history or suspicion of drug abuse within the past 5 years. * Subject with a history of myositis/myopathy or rhabdomyolysis. * Subject that requires or may require systemic immunosuppressive or immunomodulatory treatment. * Subject with known or suspected human immunodeficiency virus (HIV) infection. * Subject with a positive test for active hepatitis B or hepatitis C infection. * Subject with a history of malignancy within the previous 5 years with the exception of non-melanoma skin cancer that has been treated with no evidence of recurrence, treated cervical dysplasia or treated in situ Grade 1 cervical cancer. * Subject within the last 12 months with: unstable angina, New York Heart Association thrombosis; or subjects currently receiving anticoagulants. * Subject with uncontrolled hypertension. * Subject with an estimated creatinine clearance \< 30 mL/min. * Subjects with a creatine kinase \> 2.5 x ULN at any time during the Screening Period. * Subject with active peptic ulcer disease requiring treatment. * Subject with a history of xanthinuria, active liver disease, or hepatic dysfunction. * Subject receiving chronic treatment with more than 325 mg of salicylates per day. * Subject taking valpromide, progabide, or valproic acid. * Subject who has received an investigational therapy within 8 weeks or 5 half-lives (whichever is longer) prior to the Screening Visit. * Subject with any other medical or psychological condition, which in the opinion of the Investigator and/or Medical Monitor, might create undue risk to the subject or interfere with the subject's ability to comply with the protocol requirements, or to complete the study.