A Study of Obexelimab in Patients With Relapsing Multiple Sclerosis (MoonStone)

A Phase 2, Multicenter, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Obexelimab in Patients With Relapsing Multiple Sclerosis

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