Inclusion Criteria:

• Confirmed diagnosis of NPC (NPC1 or NPC2) and at least one neurological symptom.
• The patient is two years of age or above.
• The patient is a permanent resident of US. -If taking miglustat (Zavesca®), the patient must have been on the target dose for the past six weeks.
• If the patient is sexually active, it is agreed to use effective contraception.
• Confirmed negative urine pregnancy test for sexually active female of child-bearing potential (post-menarche).
• If the patient has a history of seizures, the condition must be adequately controlled; i.e., the pattern of seizure activity must be stable, and the patient must be on a stable dose and regimen of antiepileptic medication during one month prior to screening.
• Patient or parent/guardian must provide written informed consent to participate in EAP.

Exclusion Criteria:

• Severe liver insufficiency.
• Renal insufficiency.
• Known or suspected allergy or intolerance to arimoclomol or its constituents.
• The patient is pregnant, planning to become pregnant (while on the study) or is currently breastfeeding.
• The patient will undergo treatment with another investigational drug, whilst participating in the program or in the 4 weeks prior to commencing treatment with arimoclomol.
• The patient is either eligible and able to participate in or is currently participating in an active interventional clinical trial within the indication. The patient, in the opinion of the clinician, is unable to comply with the treatment or has a medical condition that would potentially increase the risk to the patient by participation.
• The patient has a medical condition which hinders the clinician's assessment of arimoclomol safety and efficacy (e.g., certain epileptic conditions or severe cataplexy).