Zenas BioPharma shares jump on 95% lesion reduction in MS trial
Obexelimab shows robust efficacy in Phase 2 MoonStone study, positioning drug as potential 'franchise molecule'
Zenas BioPharma shares rose 3.8% to $21.80 on Monday after the clinical-stage biotech reported robust results from a Phase 2 trial of its experimental multiple sclerosis treatment, achieving a 95% relative reduction in inflammatory brain lesions.
The Waltham, Massachusetts-based company's lead drug candidate, obexelimab, met the primary endpoint in the MoonStone trial of 116 patients with relapsing multiple sclerosis, demonstrating a highly statistically significant reduction in new gadolinium-enhancing T1 lesions compared with placebo over weeks 8 and 12 of treatment (p=0.0009). Only two new lesions were observed in patients receiving obexelimab versus 19 in the placebo group during this period.
The results, which were selected for a late-breaking presentation at the ACTRIMS Forum 2026, showed near-complete suppression of inflammatory lesions by week 8 that was sustained through week 12 and maintained at week 24. The adjusted mean number of new lesions per scan was 0.01 in the obexelimab arm compared with 0.23 in the placebo group.
"The robust and durable activity of obexelimab through week 24 provides strong validation for the potential of B-cell inhibition across various autoimmune diseases," said Lonnie Moulder, founder and chief executive officer of Zenas. He described obexelimab as a potential "franchise molecule" that could significantly improve patient outcomes.
Obexelimab represents a novel approach to treating autoimmune conditions. The drug is an Fc-engineered bifunctional monoclonal antibody that targets both CD19 and FcγRIIb, inhibiting B-cell activity without causing cell depletion. This mechanism differs from existing B-cell therapies that eliminate B cells entirely, potentially offering a different safety profile and preserving important immune functions.
Beyond the primary endpoint, obexelimab demonstrated benefits across multiple secondary measures. The drug reduced serum Neurofilament Light (NfL) by 40% through week 24, a biomarker associated with neurodegeneration in multiple sclerosis. Patients also showed stability in Expanded Disability Status Scale (EDSS) scores, indicating no progression in physical disability.
The safety profile was consistent with previous trials, with common adverse events including infections, hypersensitivity, and mild injection site reactions. No new safety signals emerged through 24 weeks of treatment.
The multiple sclerosis market presents a significant commercial opportunity, with global therapeutics revenues projected to reach approximately $33.4 billion in 2026. The competitive landscape includes established B-cell therapies such as Roche's Ocrevus (ocrelizumab) and Novartis's Kesimpta (ofatumumab), as well as emerging Bruton's tyrosine kinase (BTK) inhibitors including Sanofi's tolebrutinib, which awaits an FDA approval decision in December 2025.
Zenas's broader pipeline includes orelabrutinib, a BTK inhibitor licensed from InnoCare that is already in Phase 3 trials for primary progressive multiple sclerosis, with another Phase 3 study for secondary progressive MS expected to begin in the first quarter of 2026.
The company also expects to submit marketing applications to the FDA and European Medicines Agency for obexelimab in IgG4-Related Disease in 2026, and anticipates reporting topline results from the Phase 2 SunStone trial for systemic lupus erythematosus.
Analyst sentiment remains positive on the stock, with 7 buy ratings and 1 hold rating among coverage analysts. The consensus price target of $43.57 suggests potential upside of more than 100% from current levels, though the stock has traded in a wide 52-week range between $6.11 and $44.60.
Zenas's market capitalization stands at approximately $1.91 billion. The company, which went public in 2024, reported trailing twelve-month revenue of $15 million and negative operating margins of 13%, typical for a clinical-stage biotechnology company with significant research and development expenses.
The positive Phase 2 data positions Zenas to advance obexelimab into larger Phase 3 trials for multiple sclerosis, though regulatory approval and market launch for this indication are not expected before 2027 at the earliest. The company's near-term catalysts remain the IgG4-Related Disease regulatory submissions and the systemic lupus erythematosus trial results.