One Year, Open Label, Dose Escalation Long-term Safety Study in Multiple Sclerosis (MS) Subjects With Spasticity

Clinical protocol OS440-3003 is a multicenter, open-label, non-randomized, uncontrolled, dose escalation study to evaluate the safety and tolerability of Arbaclofen Extended Release Tablets (AERT) over 1 year in MS subjects with spasticity. All subjects in this study will receive arbaclofen in the extended release tablet formulation. All subjects will begin treatment with arbaclofen at 20 milligrams (mg) per day (2 X 10 mg) for two weeks, then increase to 30 mg per day (2 X 15 mg) for two weeks, and then increase to 40 mg per day (2 X 20 mg) based on the Dose Escalation Criteria. Once the subject reaches the Maintenance Dose, they will remain on that dose for approximately 1 year. The Maintenance Dose is the highest tolerated dose, not to exceed 40 mg per day. In this study, the Up Titration Period begins with Visit 2 and ends when the Maintenance Dose is determined. The Maintenance Period is the time from establishment of the Maintenance Dose until the down-titration visit. For subjects that complete the study, the Maintenance Period is for approximately 1 year in duration. The Down Titration Period will be 2 weeks for subjects on the maintenance dose of 40 mg per day and 1 week for subjects on the maintenance dose of 30 mg per day. There is no down titration phase for subjects on a 20 mg per day maintenance dose. Subjects for whom the Maintenance Dose is 20 mg per day (i.e., subjects who did not tolerate the 30 mg/ day dose) will begin the 1 year Maintenance Period at Visit 4 and complete the study at Visit 8. Subjects for whom the Maintenance Dose is either 30 mg or 40 mg per day will begin the Maintenance Period at Visit 5 and complete the maintenance portion of the study at Visit 9. The next portion of the study is down titration. The subjects on the 20 mg per day Maintenance Dose will not have a down-titration. For subjects on the 30 mg per day Maintenance Dose, down-titration will begin at Visit 9 and continue for 1 week. These subjects will return for Visit 10 after the 1 week down-titration. For subjects on the 40 mg per day Maintenance Dose, down titration will begin at Visit 9 and continue for 2 weeks. These subjects will return for Visit 10 after the 2 week down-titration. Study visits will occur every two weeks until the Maintenance Dose is reached and then study visits will occur every three months with telephone follow-up calls monthly in between visits