This is a 24-month, prospective, exploratory, observational study to investigate immune phenotypes in patients with MS following treatment with ocrelizumab.

This is a 24-month, prospective, exploratory, observational study to investigate immune phenotypes in patients with MS following treatment with ocrelizumab. The study will be conducted on Health Sciences University Istanbul Haydarpaşa Numune Training and Research Hospital, Neurology Department.

The decision to treat with ocrelizumab must be made prior to and independently from the proposal to enroll the patient into this study and in line with the Summary of Product Characteristics (SmPC) approved by the Turkish Ministry of Health.

Data will be recorded at screening visit, baseline visit (month 0), second visit on 6th month, third visit on 12th month and last visit (end of the study [EOS]) on 24th month according to local clinic practice. Optional ad hoc visits could be conducted if relapse of MS or infection after vaccination occurs during ocrelizumab treatment.

The duration of the study for each patient will be 24 months.

Inclusion Criteria:

• Adults (≥18 years old) with a diagnosis of relapsing forms of multiple sclerosis (RMS) or primary progressive multiple sclerosis (PPMS) according to the 2017 revised McDonald criteria.
• Previous MS treatment with at least one of other DMT(*). The patients can be without treatment before switching until the end of wash-out period of previous DMT(s) or until lymphocytes parameter is in normal range.
• Previous treatment change with the reasons inefficacy, safety related issues or lack of compliance.
• Decision to initiate ocrelizumab therapy (in accordance with the product characteristics approved in Turkey) has already been taken for the treatment of MS patient as part of routine clinical practice. The decision to treat with Ocrelizumab must be made prior to and independently from the proposal to enroll the patient into this study.
• Agreed and signed informed consent.

(*) A DMT is defined as any of the following drugs: Teriflunomide, Interferon beta 1a, Interferon beta 1b, Peginterferon beta 1a, Glatiramer acetate, Fingolimod, Daclizumab, Alemtuzumab, Cladribine, Dimethyl fumarate, and Natalizumab.

Exclusion Criteria:

• Previously treated with anti-CD20 therapy (rituximab, atacicept, belimumab or ofatumumab).
• Medical history of a malignancy, active infection (including Hepatitis B virus) or chronic inflammatory disease.
• Medical history or use of any medication other than a DMT as defined above which may affect immunophenotypes of the participants.

MS patients will be stratified for gender to reflect epidemiological incidence of MS subtypes. Gender ratios (Female/Male) for RMS and PPMS are set for 2:1 and 1:1, respectively.

A total of 20 MS patients who were previously treated with at least one of other DMT will be recruited. Participants will be recruited by specialized physicians who are experienced in the diagnosis and treatment of MS and ocrelizumab use.

• Consecutive MS patients with an already planned ocrelizumab therapy will be screened for recruitment in study recruiting clinics. Ocrelizumab treatment will not be initiated to recruit study patients.
• MS patients will be stratified for gender to reflect epidemiological incidence of MS subtypes. Gender ratios (Female/Male) for RMS and PPMS are set for 2:1 and 1:1, respectively.