Safety and Tolerability Study of MEDI-551, a B-cell Depleting Agent, to Treat Relapsing Forms of Multiple Sclerosis

This is a Phase 1, multicenter, multinational, randomized, blinded, placebo-controlled,
dose-escalation study to evaluate the safety and tolerability of IV and SC doses of MEDI-551
in adult subjects with relapsing forms of MS.

Inclusion Criteria:

- Confirmed relapsing form of MS (ie, RRMS, SPMS, PRMS, or CIS) according to revised
2010 McDonald criteria and MRI brain lesions consistent with MS on screening

- At least 1 documented relapse within the past 3 years prior to screening

- EDSS between 0.0 and 6.5 at screening

- Have no more than 20 Gd-enhancing T1 brain lesions detected by cranial MRI scan

Exclusion Criteria:

- Subjects with impaired renal function

- Major surgery within 8 weeks of the screening visit

- Subjects who are unable to undergo cranial MRI scan

- A history of hypersensitivity to Gd-containing MRI contrast agents

- Has received within 1 year prior to screening: monoclonal antibodies, experimental
B-cell depleting agents, or treatment with natalizumab (Tysabri) for greater than 3
months

- Receiving monthly methylprednisone or equivalent glucocorticoid for disease
modification of a relapsing form of MS

- Known sensitivity to acetaminophen/paracetamol, diphenhydramine or equivalent
antihistamine, methylprednisolone or equivalent glucocorticoid, or to any component of
the investigational drug

- Diagnosis of PPMS, neuromyelitis optica, or other non-MS variant of neuro-inflammatory
or demyelinating diseases

- Any history of opportunistic infection or the presence of active infection within two
months prior to screening or any herpes zoster infection that has not resolved within
12 weeks prior to screening

- Any clinically significant findings during the screening phase, including physical,
neurological, laboratory, or ECG examination as per protocol