A novel sustained‐release cysteamine bitartrate formulation for the treatment of cystinosis: Pharmacokinetics and safety in healthy male volunteers

The strict intake regimen of cysteamine bitartrate formulations, associated with side effects, is a concern for the treatment compliance in cystinosis therapy. Therefore, there is a need for a cysteamine formulation with an improved pharmacokinetic profile. This study investigated the pharmacokinetics, safety and tolerability of a new sustained‐release cysteamine dosage form, PO‐001, in healthy volunteers. This was a randomized, investigator‐blinded, three‐way cross‐over study to compare single doses (600 mg) of PO‐001 with Cystagon(®) (immediate‐release) and Procysbi(®) (delayed‐release). Collected blood samples were analyzed for plasma cysteamine concentrations and pharmacokinetic parameters were estimated by noncompartmental analysis. In addition, plasma cysteamine concentrations were analyzed using a population pharmacokinetic approach using NONMEM(®). Pharmacokinetics showed clear sustained‐release characteristics of PO‐001 over time with a lower C (max) and longer T (max) compared to Cystagon(®) and Procysbi(®). All treatment‐emergent adverse events were of mild severity, with the exception of two subjects who reported moderate severity gastrointestinal problems including vomiting and diarrhea, which were related to Cystagon(®) intake. Population PK simulations showed a favourable PK profile based on C (max) and C (trough) concentrations at steady state. In conclusion, a single dose of 600 mg PO‐001 was well tolerated with no findings of clinical concern. This new cysteamine bitartrate formulation showed pharmacokinetics of a sustained‐release formulation, which may be beneficial for the treatment of cystinosis patients. This study supports advancing this type of sustained‐release formulation into a subsequent study to confirm reduced dosing frequency with efficient control of white blood cells (WBCs) cystine levels. Netherlands Trial Registry (NTR) (NL67638.056.18).