The primary purpose of this study is to evaluate the safety and tolerability of arimoclomol in ALS patients following 90 days of dosing. In addition, the amount of arimoclomol in blood and cerebrospinal fluid will be measured.

Arimoclomol is a small molecule that upregulates "molecular chaperones" in cells under stress. Arimoclomol extends survival by five weeks when given both pre-symptomatically and at disease onset in a mutant superoxide dismutase (SOD1) transgenic mouse model of ALS. Furthermore, it has been demonstrated to have neuroprotective and neuroregenerative effects in other rat models of nerve damage. Molecular chaperone proteins are critical in the cellular response to stress and protein misfolding. Recent data suggest that the SOD1 mutation responsible for ALS in some patients with familial disease reduces the availability of a variety of molecular chaperones, and thus weakens their ability to respond to cellular stress. Protein misfolding and consequent aggregation may play a role in the pathogenesis of both the familial and sporadic forms of ALS. Therapeutic agents such as arimoclomol that improve cellular chaperone response to protein misfolding may be helpful in ALS.

Inclusion Criteria:

• Familial or sporadic ALS
• Vital capacity equal to or more than 60% predicted value for gender, height and age at the screening visit
• First ALS symptoms occurred no more than five years prior to screening
• Must be able to take oral medication

Exclusion Criteria:

• Dependence on mechanical ventilation