Phase 3 Study of Cysteamine Bitartrate Delayed-release (RP103) Compared to Cystagon® in Patients With Cystinosis

This is a multi-center, open-label, randomized, cross-over study to determine whether
steady-state, twice a day treatment with Cysteamine Bitartrate Delayed-release
Capsules(RP103) results in comparable depletion of white blood cell (WBC) cystine levels
compared to the existing four times a day cysteamine treatment. It will involve up to 20
clinic visits plus intermittent home use of the RP103. Most of these clinic visits occur in
clusters of 3-4 consecutive days. Eligible patients will be offered enrollment into a
long-term follow up study.

Inclusion Criteria:

- Male and female subjects must have nephropathic cystinosis.

- Subjects must be on a stable dose of Cystagon® sufficient to maintain their white
blood cell (WBC) cystine level at ≤ 1.0 nmol/half-cystine/mg protein.

- Subjects must be able to swallow their typically administered Cystagon® capsule with
the capsule intact.

- Within the last 6 months, no clinically significant change in liver function [i.e.,
ALT, AST, total bilirubin] and renal function [i.e., estimated GFR] at Screening as
determined by the Investigator.

- Subjects with an estimated GFR (corrected for body surface area) > 30 mL/min/1.73m2.

- Sexually active female subjects of childbearing potential (i.e., not surgically
sterile [tubal ligation, hysterectomy, or bilateral oophorectomy] or at least 2 years
naturally postmenopausal) must agree to utilize the same acceptable form of
contraception from Screening through completion of the study.

- Subjects must be willing and able to comply with the study restrictions and
requirements.

- Subjects or their or their parent or guardian must provide written informed consent
and assent (where applicable) prior to participation in the study.

Exclusion Criteria:

- Subject's age < 6 years old or subject's weight < 21 kg.

- Subjects with a known history, currently of the following conditions or other health
issues that make it, in the opinion of the investigator, unsafe for them to
participate: inflammatory bowel disease (if currently active) or have had prior
resection of small intestine; Heart disease (e.g., myocardial infarction, heart
failure, arrhythmias or poorly controlled hypertension) 90 days prior to Screening;
Active bleeding disorder 90 days prior to Screening; Malignant disease within the
last 2 years.

- Patients with a hemoglobin level < 10 g/dL at Screening or a level that, in the
opinion of the investigator, makes it unsafe for the subject to participate.

- Subjects receiving any form of cysteamine medication through a gastric tube.

- Subjects who are receiving maintenance dialysis or who have had a kidney transplant.

- Subjects who are on an active kidney transplant list or who are planning to receive a
kidney transplant within 3 months of Screening.

- Subjects with known hypersensitivity to cysteamine or penicillamine.

- Female subjects who are nursing, planning a pregnancy, known or suspected to be
pregnant, or have a positive serum pregnancy screen.

- Subjects who have a made a blood donation within 30 days of Screening.

- Subjects who, in the opinion of the Investigator, are not able or willing to comply
with the protocol.