Investigating Mechanism of Action of DAC HYP in the Treatment of High-Inflammatory Multiple Sclerosis (MS)

Objective: The primary goal of this study is to investigate the mechanism of action (MOA) of CD25-blocking therapies in high inflammatory multiple sclerosis (HI-MS). The secondary goal of this study is to assess long-term safety and efficacy of CD25-blocking therapies in HI-MS. Study population: Two cohorts of patients will be enrolled: * Long-term daclizumab therapy cohort: Up to 15 daclizumab-treated patients with relapsing-remitting (RR-MS) or secondary-progressive MS (SP-MS) previously classified as HI-MS based on MRI/clinical criteria, who have been treated with IV daclizumab for a minimum of 1 year and responded to this therapy with significant (\>70%) decrease in contrast-enhancing lesions (CEL) or stabilization/improvement of disease activity (\>60% decrease in MS relapses and stable or improved EDSS disability score). * New treatment cohort: Up to 15 HI-MS patients (RR- or SP-MS) with inadequate therapeutic response to first-line, FDA-approved immunomodulatory therapies for MS or who cannot, for any reason, be treated with first-line, FDA-approved immunomodulatory therapies for MS. Design: This is an open label, Phase I trial of 150 mg of daclizumab high yield process (DAC HYP) administered subcutaneously (SC) every 4 weeks for a total of 3 years. Outcome measures: Because the main goal of this study is to investigate the MOA of CD25-blocking therapies in MS, the primary outcomes are mechanistic immunological studies performed on clinical samples (peripheral blood mononuclear cells (PBMC), cerebrospinal fluid (CSF) cells and skin biopsies) derived from DAC HYP-treated patients. The secondary outcome measure is long-term safety and tolerability of subcutaneous DAC HYP in HI-MS patients.