ROS-MS is a clinical pharmacological substudy to the OVERLORD-MS study (NCT04578639), designed to examine the possibilities of personalized treatment with rituximab and ocrelizumab in patients with relapsing-remitting multiple sclerosis.

OVERLORD-MS is a 30 months prospective randomized double blinded multicenter non-inferiority study. The objective of OVERLORD-MS is to demonstrate if rituximab is non-inferior to ocrelizumab with regards to efficacy and safety in treatment naïve patients with relapsing-remitting multiple sclerosis (RRMS), diagnosed within the last 12 months.

In the patients enrolled in the clinical pharmacological substudy ROS-MS the serum concentrations of rituximab and ocrelizumab will be quantified using liquid chromatography tandem mass spectrometry (LC MS/MS) at predefined points during the dosing interval. Relevant biochemical parameters will also be analyzed in these samples.

Based on these measurements, the investigators will examine correlations between serum concentrations, biochemical parameters and the clinical outcomes in the OVERLORD-MS study. The objective is to evaluate whether clinical pharmacological tools, such as therapeutic drug monitoring (TDM) and pharmacokinetic pharmacodynamic models (PK-PD models), may be of value in the personalization of treatment with rituximab and ocrelizumab in patients with relapsing-remitting multiple sclerosis.

Inclusion Criteria:

• Included in OVERLORD-MS (NCT04578639)
• Willing to attend laboratory for blood sample collection at scheduled time points

Exclusion criteria:

* Not willing to attend laboratory for blood sample collection at scheduled time points

In OVERLORD-MS, treatment-naïve male and female patients aged 18-60 years, with newly diagnosed multiple sclerosis, are randomized 2:1 to treatment with rituximab or ocrelizumab. In the sub-study ROS-MS, patients are recruited from the patients included i OVERLORD-MS.