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.

Study with completed results acquired from Horizon in 2024.

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.