Safety Study of an Immunomodulating Microparticle to Treat Progressive Multiple Sclerosis

This is a single center, open-label, non-randomized, dose-escalation study, to be conducted in two phases: * a dose-escalation (DE) phase, to evaluate the safety, tolerability, MTD, and PD of MIS416 administered IV once weekly for 4 doses; and * a dose-confirmation (DC) phase, which will be a cohort expansion at or below the MTD (i.e., the RTD) of MIS416, dosed once weekly for up to 12 doses. Subjects will be treated with a weekly IV dose of MIS416 in 28-day cycles: 1 cycle in the DE phase, and up to 3 cycles in the DC phase. Subjects will be evaluated and dosed weekly each cycle in each phase. Subjects will return for a follow-up visit 7 days after completion of the last dose of study drug. The primary objectives of this study are: 1. To determine the safety and tolerability, dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), and recommended therapeutic dose (RTD) of intravenously (IV) administered MIS416 weekly in patients with chronic progressive multiple sclerosis (CPMS); and 2. To assess the pharmacodynamic (PD) effects of MIS416, including effects on serum cytokine levels and peripheral blood mononuclear cell (PBMC) composition, cytokine/chemokine expression and function. The secondary objectives of this study are: 1. To document any changes in MS clinical status occurring during the 12-week MIS416 dosing period in the dose-confirmation phase, as determined by the Multiple Sclerosis Functional Composite (MSFC), Fatigue Severity Scale (FSS), Short Form Health Survey (SF-36), and Expanded Disability Status Scale (EDSS); the frequency of clinical relapses; and signs of clinical activity on serial cranial MRI scans; and 2. To evaluate, in exploratory fashion, any correlations between clinical, radiological and PD outcomes.