RecruitingPhase 3Drug trialA Pivotal Study of N-Acetyl-L-Leucine on Niemann-Pick Disease Type CA pivotal, randomized, double-blind, placebo controlled, multi-center therapeutic study for patients age 4 and older with a confirmed diagnosis of Niemann Pick disease type C (NPC). The objective of this study is to evaluate the safety, tolerability and efficacy of N-acetyl-L-leucine (IB1001) compared to standard of care. Following this randomized, double-blind, placebo-controlled "Parent Study", an extension phase is conducted for (1) patients who completed the "Parent Study" and (2) patients who are enrolled directly into the Extension Phase. Currently, the Extension Phase provides patients with 3 years of open-label treatment.