This study aims to examine the efficacy and safety of obexelimab in participants with relapsing multiple sclerosis

The study consists of a Screening Period (Day -28 to Day -1), a 24-week treatment period (Part A and Part B), a 52 week open label extension and an expected 12-week Follow-up Period. Patients with Relapsing Multiple Sclerosis will be randomized in 2:1 ratio to obexelimab or placebo. Randomization will be stratified by Gd lesion status at screening (≥ 1 vs 0).

Part A is the 12-week Randomized Placebo-Controlled Period (RCP), during which obexelimab or placebo will be administered as weekly subcutaneous (SC) injections. Following Part A, all patients will enter the Part B, a 12-week Open-Label Period (OLP), during which all patients will receive obexelimab administered as weekly SC injections. After Part B, patients will enter Part C, a 52-week Open-Label Extension (OLE), after which they will return for an in-clinic Safety Follow-Up Visit 12 weeks after the completion of Part C (i.e. Week 88). If at this time, B cells have not returned to baseline or above the lower limit of normal (LLN), patients will be asked to return every 12 weeks until B cells return to baseline or above the LLN (at minimum). The maximum expected duration of the study is 92 weeks (Screening Period = 4 weeks, Parts A, B and C = 76 weeks, Follow-up Period = 12 weeks).

Inclusion Criteria:

1. Diagnosis of RMS (relapsing-remitting or secondary progressive with relapses) according to the 2017 revision of the McDonald diagnostic criteria

2. An EDSS of ≤ 5.5 at the Screening Visit

3. Must have documentation of:

   1. . at least 1 relapse within the previous year OR
   2. . ≥ 2 relapses within the past 2 years OR
   3. . ≥ 1 active Gd-enhancing brain lesion on an MRI scan within the past 6 months prior to screening

4. Not of childbearing potential or willing to follow contraceptive guidance

Exclusion Criteria:

1. Primary progressive MS or secondary progressive MS without relapses
2. Meet criteria for neuromyelitis optica spectrum disorder
3. Relapse in the 30 days prior to randomization
4. ≥ 10 years disease duration from onset with patient's EDSS ≤ 2.0 (patient reported is adequate in absence of written medical record)
5. Has > 20 Gd+ lesions on brain MRI at screening

Participants, Care Providers, Investigator, Outcomes Assessor