The primary objective of the study is to compare the antigenicity of the new fetal bovine serum (FBS)-free/human serum albumin (HSA)-free Rebif® formulation (RNF) to historical data.

As has been seen with other recombinant protein molecules, the use of injectable recombinant proteins may result in the development of neutralising antibodies (NAbs). Antibodies are considered neutralising by their ability to inhibit the biological effect of interferon in a bioassay system. Serono has actively pursued improvements in the formulation of interferon (IFN) beta-1a to reduce aggregate levels and to develop a formulation that is HSA-free. Reducing aggregates should reduce antigenicity of the product while removal of HSA may have an unpredictable effect on antigenicity. Serono will conduct a study to assess the immunogenicity and safety of the new HSA-free formulation, manufactured using IFN-ß-1a drug substance produced by a new clone from the FBS-free process.

The design of this study assumes that the Phase I tolerability and pharmacokinetic (PK) data of the selected formulation is similar to the currently approved HSA-containing formulation.

Inclusion Criteria:

• Subject has a relapsing form of Multiple Sclerosis (MS); diagnosis of MS is in accordance with the McDonald criteria
• Subject is eligible for interferon therapy
• Subject is between 18 and 60 years old
• Subject has an Expanded Disability Status Scale (EDSS) < 6.0.
• Subject is willing to follow study procedures
• Subject has given written informed consent
• Female subjects must be neither pregnant nor breast-feeding, and must lack childbearing potential, as defined by either:
• Being post-menopausal or surgically sterile, or
• Using a hormonal contraceptive, intra-uterine device, diaphragm with spermicide or condom with spermicide for the duration of the study.
• Confirmation that the subject is not pregnant must be established by a negative serum or urinary hCG test within 7 days prior to start of study treatment. A pregnancy test is not required if the subject is post-menopausal or surgically sterile.

Exclusion Criteria:

• Subject has a Clinically Isolated Syndrome (CIS), Primary Progressive MS, or Secondary Progressive MS without superimposed relapses.
• Subject had any prior interferon beta therapy (either beta-1b or beta-1a)
• Subject has an ongoing MS relapse.
• Subject received any other approved disease modifying therapy for MS (e.g. glatiramer acetate) or any cytokine or anti-cytokine therapy within the 3 months prior to SD1.
• Subject had prior use of cladribine or has previously received total lymphoid irradiation.
• Subject received oral or systemic corticosteroids or adrenocorticotropic hormone (ACTH) within 30 days of SD1.
• Subject received intravenous immunoglobulins or underwent plasmapheresis within the 6 months prior to SD1.
• Subject received immunomodulatory or immunosuppressive therapy (including but not limited to cyclophosphamide, cyclosporin, methotrexate, azathioprine, linomide, mitoxantrone, teriflunomide, natalizumab, laquinimod, Campath) within the 12 months prior to SD1.
• Subject requires chronic or monthly pulse corticosteroids during the study.
• Subject received any investigational drug or experimental procedure within 12 weeks of SD1.
• Subject has inadequate liver function, defined by a total bilirubin, aspartate aminotransferase (AST) or alanine aminotransferase (ALT) or alkaline phosphatase > 2.5 times the upper limit of the normal values.
• Subject has inadequate bone marrow reserve, defined as a white blood cell count less than 0.5 x lower limit of normal.
• Subject suffers from current autoimmune disease.
• Subject suffers from major medical or psychiatric illness that in the opinion of the investigator creates undue risk to the subject or could affect compliance with the study protocol.
• Subject has a known allergy to IFN or the excipients.