Zenas BioPharma (NASDAQ:ZBIO) shares surged 80% on Monday following the release of highly encouraging Phase 2 results from its MoonStone clinical trial evaluating obexelimab in patients with Relapsing Multiple Sclerosis (RMS).
The company said the investigational therapy achieved its primary endpoint, delivering a 95% relative reduction in new gadolinium-enhancing T1 lesions compared to placebo. The statistically robust results (p=0.0009) showed near-complete suppression of inflammatory activity by week 8, with the effect persisting through week 12.
According to the data, the adjusted mean number of new lesions per scan was 0.01 in the obexelimab arm versus 0.23 in the placebo group. Obexelimab also produced a meaningful reduction in the cumulative number of new and/or enlarging T2 weighted hyperintense lesions — a key indicator of total disease burden.
“These profound MoonStone trial results, including the near elimination of new GdE T1 lesions, provide strong evidence of the deep and sustained inhibitory mechanism of obexelimab and further validate the potential for obexelimab to become a meaningful therapy across multiple autoimmune diseases,” said Lonnie Moulder, Founder and Chief Executive Officer of Zenas.
The company added that the drug’s safety profile remained consistent with previous studies, with most adverse events being mild injection site reactions. Some patients experienced infections and hypersensitivity, but no unexpected safety signals emerged.
Zenas expects to present 24-week results from MoonStone in the first quarter of 2026. Additional topline data from the Phase 3 INDIGO trial in IgG4-RD are anticipated by late 2025, while findings from the Phase 2 SunStone trial in Systemic Lupus Erythematosus are slated for mid-2026.