Arimoclomol is an investigational drug for amyotrophic lateral sclerosis (ALS) 
that amplifies heat shock protein gene expression during cell stress. The 
objectives of the present study were to assess the safety, tolerability, and 
pharmacokinetics of arimoclomol in ALS. Eighty-four participants with ALS 
received arimoclomol at one of three oral doses (25, 50, or 100 mg three times 
daily) or placebo. The primary outcome measure was safety and tolerability. A 
subset of 44 participants provided serum and cerebrospinal fluid (CSF) samples 
for pharmacokinetic analysis. Participants who completed 12 weeks of treatment 
could enroll in a 6-month open-label study. Arimoclomol at doses up to 300 
mg/day was well tolerated and safe. Arimoclomol resulted in dose-linear 
pharmacologic exposures and the half-life did not change with continued 
treatment. Arimoclomol CSF levels increased with dose. Arimoclomol was shown to 
be safe, and it crosses the blood-brain barrier. Serum pharmacokinetic profiles 
support dosing of three times per day. An efficacy study in ALS is planned.