Safety and Tolerability of ISX (Isoxsuprine HCL) in MS Relapses

This is a proof of concept, randomized, double-blind, placebo-controlled, 2-arm, parallel group study of Isoxsuprine in MS subjects experiencing a typical relapse. All subjects will have a documented diagnosis of relapsing MS or a clinically isolated syndrome by international criteria. The relapse will be of sufficient severity that their physician recommends treatment with a high dose corticosteroid pulse. All subjects will have a physical examination and history with questions on drug sensitivities. Subjects experiencing the onset of objective neurological deficits consistent with relapse within 7 days of randomization are eligible for screening for this study. Those currently on MS disease modifying therapy will have received a stable regimen of the medications for at least 30 days prior to screening and will continue the same doses and regimens for the duration of their study participation. Consented subjects will be assessed for relapse criteria and those who meet study eligibility criteria and agree to be treated with a standard 3 to 5 day pulse of high dose corticosteroids, will be randomized with equal probability to 1 of 2 treatment groups: placebo capsule or active Isoxsuprine (ISX). The Screening Visit will take place within 7 days of relapse onset and within 48 hours of initiating high dose steroids. Subjects may start corticosteroids anytime during this 7 day window. During the screening period, subjects will be assessed with the Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite (MSFC), and cognitive testing prior to treatment with ISX or placebo (1:1 ratio). Safety Assessments during screening will include a physical exam, electrocardiogram, vital signs, weight and a urine pregnancy test for females of child bearing potential. At 7 (± 1) days following the completion of the 5-day ISX dosing, subjects will be re-assessed with the EDSS. Subjects will be evaluated for treatment response using the EDSS and other standard measures. Study drug will be administered as one (1) 10 mg capsule, 3 times daily for 5 days in conjunction with concomitant dosing with high dose corticosteroids. This can be any accepted regimen, including daily iv methylprednisolone 1000 mg/day or 600mg oral prednisone two times a day at approximately 8AM and noon, with food, as typically provided by UNM MS Specialty Clinic.