Phase 2 trial of obexelimab recruiting adults with relapsing MS
Trial to assess number of new actively inflamed lesions on MRI after treatment
A Phase 2 clinical trial is currently recruiting adults with relapsing types of multiple sclerosis (MS) to investigate Zenas Biopharma’s experimental therapy obexelimab as a weekly subcutaneous, or under-the-skin, injection, the company has announced in a press release.
The study, called MoonStone (NCT06564311), is open to adults ages 18 to 60 with relapsing-remitting MS or active secondary progressive MS. Enrollment is ongoing at more than 40 sites across the U.S., Europe, and China, and results are expected in the third quarter of 2025.
In MS, inflammation in the brain and spinal cord causes damage to nerve cells, causing problems with normal nerve signaling that ultimately give rise to symptoms of MS.
One type of immune cell with a central role in MS inflammation are B-cells. Several approved MS treatments, such as Ocrevus (ocrelizumab), Briumvi (ublituximab), and Kesimpta (ofatumumab), work by depleting B-cells by targeting a protein called CD20.
Obexelimab designed to reduce activity of B-cells without depleting them
Obexelimab is designed to reduce the activity of B-cells without depleting them. The therapy specifically targets two B-cell proteins called CD19 and FcgammaRIIb. According to Zenas, the therapy is expected to reduce the activity of a broader range of B-cells than available treatments that target CD20.
“This unique mechanism of action and self-administered, subcutaneous once-weekly injection regimen may broadly and effectively address the [disease-driving] role of B cell lineage in chronic autoimmune disease,” the company stated.
The trial is enrolling patients who experienced at least one disease relapse in the preceding year or two relapses in the past two years, or who had at least one actively inflamed lesion detected by an MRI scan done up to six months before entering the study.
About 93 participants will be randomly assigned to receive 250 mg obexelimab or a placebo, given by subcutaneous injections once weekly for 12 weeks (about three months).
After completing the placebo-controlled part of the study, participants will have the option to enter an open-label period where all will receive obexelimab for at least three months. This will be followed by another open-label extension lasting one year.
The trial’s main goal is to test whether obexelimab is better than a placebo at reducing the number of new actively inflamed lesions visible on MRI scans. The treatment’s effects on other MRI outcomes and markers of nerve damage will also be assessed.
In addition to MS, Zenas is running other trials testing obexelimab as a potential treatment for various other conditions that are driven by abnormal B-cell activity, such as lupus.
“We enter 2025 with an opportunity to achieve major value-driving milestones with the anticipated results from our ongoing obexelimab Phase 2 and Phase 3 clinical trials,” said Lonnie Moulder, founder and CEO of Zenas. “We are extremely proud of the accomplishments of our dedicated team.”
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