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

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.