REduCing Immunogenicity to PegloticasE (RECIPE) Study

Pegloticase is highly efficacious therapy for chronic refractory gout patients (n = > 400K in
the US alone). It decreases serum urate (sUA) levels to often undetectable levels and reduces
tophi burden. However, its long-term real world effectiveness is severely limited due to its
immunogenicity caused by anti-pegloticase antibody formation. REducing Immunogenicity to
PEgloticase (RECIPE) is a Phase II, double-blind, placebo controlled, proof-of-concept trial
in 32 subjects initiating pegloticase for treatment of chronic refractory gout. RECIPE will
investigate the preliminary efficacy and safety of using immune modulating therapy with
mycophenolate mofetil (MMF) to prevent immunogenicity conferred by pegloticase. Subjects will
be randomized 3:1 to receive MMF vs. placebo in addition to everyone receiving pegloticase.
The co-primary aims of the RECIPE trial are to 1) determine if a 12 week course of immune
modulating therapy with daily MMF can safely and significantly attenuate immunogenicity to
pegloticase as determined by the proportion of participants achieving and maintaining an sUA
less than or equal to 6 mg/dL through 12 weeks, compared to concurrent controls, and 2) to
assess the incidence and types of adverse events and infusion reaction. After 12 weeks of
co-administration, all participants will continue on pegloticase for an additional 12 weeks
without combination MMF immune modulating therapy to evaluate the longer term benefits
(durability) and safety of this approach. The secondary aims are to: 1) Determine the 6 month
durability of immune modulation after discontinuation of the short course of MMF by: a)
assessing the absolute change in sUA from baseline to Week 24, and Week 12 to Week 24 and b)
determining the proportion of participants with sUA ≤ 6 mg/dL through 24 weeks, and Week 12
to Week 24; 2) Identify and characterize the pegloticase immune response by immunoglobulin
isotypes (IgG and IgM), specificities, and antibody titer; and 3) Examine patient reported
outcomes (PROs) using the NIH supported Patient Reported Outcomes Measurement Information
System (PROMIS) and Gout Impact Scale (GIS) instruments. The University of Alabama at
Birmingham (UAB) and the University of Michigan (UM), two large academic gout and immunology
research centers, which in aggregate see nearly 10,000 gout patients annually, will serve as
the two lead study sites and are very well-positioned to address the clinical and immunologic
questions posed.

Inclusion Criteria:

- Men and women > 18 years of age

- Diagnosed with chronic refractory gout*

- Defined as: Persons whose signs and symptoms are inadequately controlled with
urate lowering therapy (e.g. xanthine oxidase inhibitors or uricosuric agents) at
a medically appropriate dose or for whom these drugs are contraindicated.

Exclusion Criteria:

- Any serious acute bacterial infection (2 weeks prior to Visit 1), unless treated and
completely resolved with antibiotics

- Severe chronic or recurrent bacterial infections (such as recurrent pneumonia, chronic
bronchiectasis)

- Current immunocompromised condition, including current or chronic treatment with
immunosuppressive agents

- Subjects at risk for tuberculosis. Specifically, subjects with: i) current clinical,
radiographic or laboratory evidence of active or latent TB; ii) a history of active TB
within the last 3 years even if it was treated; iii) a history of active TB greater
than 3 years ago unless there is documentation that the prior anti-TB treatment was
appropriate in duration and type

- Known Hepatitis B surface antigen-positive or Hepatitis B DNA positive subjects

- Known Hepatitis C RNA-positive subjects

- Human Immunodeficiency Virus (HIV) infection

- G6PD deficiency (tested at Screening Visit 1)

- Severe chronic renal impairment (glomerular filtration rate [GFR] <25 mL/min/1.73 m2)
or currently on dialysis

- Subjects having any transplant surgery requiring maintenance immunosuppressive therapy

- Non-compensated congestive heart failure, uncontrolled arrhythmia, treatment for acute
coronary syndrome (myocardial infarction or unstable angina), or hospitalization for
congestive heart failure within 3 months of screening or uncontrolled blood pressure
(>160/100 mm Hg) at baseline (Screening Visit 1 and Week 0/Baseline visits)

- Participants who are pregnant, planning to become pregnant, breastfeeding, or not on
an effective form of birth control (defined in Study Protocol section 7.1)

- Prior treatment with pegloticase, another recombinant uricase, or concomitant therapy
with a polyethylene glycol (PEG)-conjugated drug

- Known allergy to pegylated products or history of anaphylactic reaction to a
recombinant protein or porcine product

- Subjects in whom MMF treatment is contraindicated or considered inappropriate

- Recipient of an investigational drug within 4 weeks prior to study drug administration
or plans to take an investigational agent during the study

- Current liver disease as determined by alanine transaminase ALT or aspartate
transaminase (AST) levels >3 times upper limit of normal

- Currently receiving treatment for ongoing cancer, excluding non-melanoma skin cancer

- History of malignancy within 5 years other than skin cancer or in situ carcinoma of
cervix

- Uncontrolled hyperglycemia with a plasma glucose value >240 mg/dL at screening

- Diagnosed osteomyelitis

- Individuals with hypoxanthine-guanine phosphoribosyl-transferase (HGPRT) deficiency
such as Lesch-Nyhan and Kelley-Seegmiller syndrome

- Not good candidate for the study based on opinion of the Investigator (e.g., cognitive
impairment) that might create undue risk to the participant or interfere with the
participant's ability to comply with the protocol requirements, or to complete the
study