Comprehensive Monograph: Cysteamine

Executive Summary

Cysteamine is a small molecule aminothiol that serves as the foundational, life-sustaining therapy for cystinosis, a rare and severe lysosomal storage disease. As a cystine-depleting agent, its primary mechanism of action involves a thiol-disulfide interchange reaction within the lysosome, which breaks down the accumulated, insoluble cystine into more soluble compounds that can be cleared from the cell, thereby preventing or delaying the catastrophic multi-organ damage characteristic of the disease. The therapeutic journey of Cysteamine is a notable example of pharmaceutical lifecycle management, evolving from an initial immediate-release oral formulation (Cystagon®) with a burdensome dosing schedule to a more patient-centric, delayed-release oral formulation (Procysbi®) and from a frequently administered ophthalmic solution (Cystaran®) to a more convenient viscous eye drop (Cystadrops®). These advancements have significantly improved treatment adherence and patient quality of life. While highly effective, Cysteamine possesses a significant safety profile that requires careful management, including risks of gastrointestinal distress, severe skin and bone lesions at high doses, and central nervous system effects. The drug's interaction profile is largely dependent on its formulation, with the delayed-release product being particularly sensitive to agents that alter gastric pH. Beyond its established role in cystinosis, Cysteamine is the subject of extensive research for new applications, most prominently in dermatology as a topical depigmenting agent for conditions like melasma and post-inflammatory hyperpigmentation, positioning it as a molecule with an expanding and promising therapeutic future.

Drug Identification and Chemical Profile