Zenas completes enrollment for Phase 2 trial of obexelimab for MS
MoonStone results expected later this year
Enrollment is complete for a Phase 2 trial testing Zenas Biopharma’s obexelimab in people with relapsing forms of multiple sclerosis (MS).
The trial, MoonStone (NCT06564311), is investigating how safe obexelimab is when given as weekly under-the-skin (subcutaneous) injections, and how well it works in approximately 93 participants with relapsing-remitting MS or active secondary progressive MS.
The company said it will announce results from the randomized part of the trial, in which participants receive either obexelimab or a placebo for 12 weeks, before the year’s end. The main goal for that part is to show that the experimental therapy can reduce the cumulative number of new lesions with active inflammation compared with a placebo, as measured by scans taken at eight and 12 weeks.
“We are very pleased with the rapid advancement of our broad obexelimab development program, including the completion of enrollment for the Phase 2 MoonStone trial in patients with Relapsing Multiple Sclerosis,” Lonnie Moulder, Zenas’ founder, chairman, and CEO, said in a company press release. “We look forward to reporting the results from the primary analysis of the trial.”
Targeting B-cells
MS is caused by mistaken immune system attacks that target healthy parts of the brain and spinal cord, causing nervous system inflammation and damage that interferes with nerve cell signaling.
Many immune cells are known to play a role in this inflammatory attack, but immune B-cells seem to have a central role in MS. These cells produce disease-causing antibodies that target the nervous system, and can also activate several other immune cells to take part in the attack.
Some of the most promising therapies approved for MS target these cells. They include Ocrevus (ocrelizumab), Briumvi (ublituximab), and Kesimpta (ofatumumab), which are antibody-based therapies that aim to eliminate B-cells by targeting the CD20 protein at their surface.
But these therapies only target a subset of B-cells carrying this protein, and because they eliminate B-cells, it takes patients a long time to return to normal B-cell levels after discontinuing treatment.
Zenas developed obexelimab to target a broader population of B-cells and inhibit their activity, rather than depleting them. The drug works by targeting two B-cell proteins, CD19 and FcgammaRIIb, which is expected to reduce the production of antibodies and other inflammatory molecules, limit B-cell proliferation, and reduce the activation of other immune cells.
The MoonStone trial is being conducted in two parts. In the first part, patients receive obexelimab or a placebo for 12 weeks. Researchers will examine changes in several types of brain lesions as well as changes in neurofilament light chain levels, a biomarker of nerve cell damage.
After completing this part, participants from both the obexelimab and placebo groups will receive 12 weeks of obexelimab injections. Investigators will assess the treatment’s safety throughout these two portions.
Participants may then choose to join an open-label extension and continue on weekly obexelimab for another year.
Zenas is also investigating obexelimab in lupus and immunoglobulin G4-related disease, two other autoimmune conditions.
“Given the differentiated profile of obexelimab, along with our extensive development capabilities and commercialization experience, we are well positioned to execute on the significant opportunity ahead to potentially impact the lives of patients living with autoimmune diseases worldwide,” Moulder said.
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