Pilot Study of Safety, Tolerability, Pharmacokinetics/Pharmacodynamics of RP103 Compared to Cystagon® in Patients With Cystinosis

This is a single-dose, open-labeled, non-randomized, two-period study of Cysteamine
Bitartrate Delayed-release Capsules (RP103) and Cystagon® in up to 10 patients (male or
female) with nephropathic cystinosis under fasting conditions. It will involve a 4 night
check-in to a clinical research center.

Inclusion Criteria:

- Male and female subjects must have nephropathic cystinosis.

- Children less than 22.5 kg will only be included in the study if the investigator
feels they can safely participate in the study including the required blood draw
volume for the safety and PK/PD assessments.

- Subjects must be on a stable dose of Cystagon® at least 21 days prior to Screening.

- Subjects must be able to swallow a 150 mg Cystagon® capsule with the capsule intact.

- Within the last 2 months, no clinically significant change in liver function [i.e.,
ALT, AST, alkaline phosphatase, bilirubin (total and direct)] and renal function
[i.e., serum creatinine, albumin, total protein] at Screening as determined by the
Investigator.

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

- If in the opinion of the investigator, patients can safely provide the study required
blood draw volume.

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

Exclusion Criteria:

- If, in the opinion of the investigator, the planned study dose would exceed the
patient's tolerability of cysteamine based on their prior Cystagon® steady state drug
requirements.

- Evidence of or verbal attestation of Helicobacter pylori infection, presently, or
within the last 90 days prior to Screening.

- Subjects with a known history, currently or within the past 90 days prior to
Screening, of the following conditions or other health issues that make it, in the
opinion of the investigator, unsafe for them to participate, or whose concomitant
medical problems preclude them from committing to the study schedule including the
following: Crohn's disease, inflammatory bowel disease (if currently active) or have
had prior resection of small intestine; • History of heart disease, e.g., myocardial
infarction, heart failure, arrhythmias; Any bleeding disorder; Malignant disease;
Severe liver disease as defined as ALT or AST > 2 times the upper limit of normal.

- Subjects who have had a kidney transplant.

- Subjects who are planning or are a registered candidate for a kidney transplant
within 3 months of the Screening or have a serum creatinine > 2.4.

- Subjects with known hypersensitivity to cysteamine.

- If female (of child-bearing potential), are nursing, planning a pregnancy, known or
suspected to be pregnant, or have a positive urine pregnancy screen.

- Patients with a hemoglobin level < 10.5.

- Subjects who have a made a blood donation within 60 days prior to study initiation.

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