The purpose of this study is to determine whether Tcelna (imilecleucel-T, autologous T-Cell Immunotherapy) is effective in the treatment of secondary progressive multiple sclerosis (SPMS).

Subjects whose myelin reactive T-cell can be identified by EPA will are randomized and provide blood to manufacture Tcelna. Approximately 5 weeks after receipt of the subject's whole blood procurement, the subjects will receive either Tcelna or placebo and will complete baseline assessments and will receive study treatments at Weeks 0, 4, 8, 12, and 24 (Visits 3-7), totaling 5 doses in year one.

Approximately one month prior to the Week 52 visit a second blood procurement will be performed and the subject will receive the second series of treatments as received in the first year study schedule. Subjects will be evaluated for changes in disability and cognitive function every 3 months, and radiographic changes annually.

Inclusion Criteria:

• Diagnosed with MS as defined by the modified McDonald criteria
• SPMS defined as relapsing-remitting disease with recent progression in MS-related neurological deficits
• EDSS score 3.0 - 6.0, inclusively
• Presence of myelin reactive T-cells

Exclusion Criteria:

• Diagnosed with primary progressive MS
• Treatment with beta-interferon, glatiramer acetate or dimethyl fumarate 30 days prior to screening
• Treatment with ACTH, any over-the-counter or prescription corticosteroids 60 days prior to screening
• Treatment with IVIG, plasmapheresis or cytopheresis 90 days prior to screening
• Treatment with mitoxantrone, teriflunomide, fingolimod, natalizumab, azathioprine, cyclosporine, methotrexate or mycophenolate mofetil 1 year prior to baseline
• Any prior treatment with cladribine, cyclophosphamide, total lymphoid irradiation, T cell or T cell receptor products, or any therapeutic monoclonal antibody, except natalizumab
• Previous treatment with any other MS investigational drug 1 year prior to screening
• All non-MS investigational drugs must have a minimum washout of 30 days prior to screening or 5 half-lives, whatever is the longest period of time.
• HIV or hepatitis infection
• History of cancer
• Any other significant medical condition that, in the opinion of the investigator, could cause CNS tissue damage or limit its repair.