Lesinurad Monotherapy in Gout Subjects Intolerant to Xanthine Oxidase Inhibitors

Allopurinol is the standard of care for the treatment of gout. In practice, approximately
20% of patients report side effects with allopurinol and 5% discontinue allopurinol due to
side effects. Allopurinol can cause gastrointestinal intolerance, such as nausea and
diarrhea, which appears to be dosedependent. Rash develops in about 2% of patients treated
with allopurinol, and in about 20% of patients treated with allopurinol and ampicillin or
amoxicillin. Allopurinol hypersensitivity syndrome remains a major concern among physicians.
Mortality has been estimated to be up to nearly one quarter of AHS cases, with multiorgan
system disease including hepatocellular changes and renal failure being a serious concern.
Allopurinol is also relatively contraindicated for use in combination with 6-mercaptopurine
and azathioprine, for which 1/4 to 1/3 lower doses must be given in order to avoid
hematologic toxicity. Febuxostat, in clinical trials, has shown a similar AE profile to
allopurinol. Liver function abnormalities, nausea, arthralgia and rash were the most
commonly reported AEs. In postmarketing experience, Stevens Johnson Syndrome and
hypersensitivity rashes have been reported (febuxostat prescribing information). Withdrawals
due to AEs were similar in frequency to allopurinol as well. Relative contraindications in
combination with 6-mercaptopurine and azathioprine are similar to allopurinol as well.
Lesinurad may be an important therapeutic option for patients who either cannot tolerate or
who have a contraindication to the use of allopurinol or 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 meets the diagnosis of gout as per the American Rheumatism Association
Criteria for the Classification of Acute Arthritis of Primary Gout.

- Subject has an sUA level ≥ 6.5 mg/dL at the Screening and Day -7 Visits.

- Subject must be able to take gout flare prophylaxis with colchicine or NSAID
(including Cox-2 selective NSAID) ± PPI.

- Subject has a history (either by medical record or subject interview) of intolerance
or a contraindication to either allopurinol or febuxostat.

- Body mass index (BMI) < 45 kg/m2

Exclusion Criteria:

- Subject who is taking any other approved urate-lowering medication that is indicated
for the treatment of gout at the Screening Visit.

- Subject with a documented history or suspicion of kidney stones.

- Subject who is pregnant or breastfeeding.

- 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 that requires or may require systemic immunosuppressive or immunomodulatory
treatment.

- Subject with a 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
class III or IV heart failure, myocardial infarction, stroke, or deep venous
thrombosis; or subjects currently receiving anticoagulants.

- Subject with uncontrolled hypertension.

- Subject with an estimated creatinine clearance < 30 mL/min.

- Subject with active peptic ulcer disease requiring treatment.

- Subject with active liver disease, or hepatic dysfunction.

- Subject receiving chronic treatment with more than 325 mg 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.