Must be within 18 months of diagnosis, have an FRS of at least 35 and erect SVC% predicted equal to or above 80% at screening, and not use BiPAP more than 2 hours while awake. The trial recruitment page is not as clear as the NIH entry on those criteria.
Just heard they seem to be offering early access of arimoclomol for those interested and not eligible for the trial. Scroll down on this link for details.