WALTHAM, Mass. — February 9, 2026 — Leads & Copy —
Zenas BioPharma, Inc. (Nasdaq: ZBIO) announced results from the Phase 2 MoonStone trial of obexelimab in Relapsing Multiple Sclerosis (RMS) were presented at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2026, held February 5-7 in San Diego, California.
The trial results, announced Feb. 9, 2026, showed obexelimab met the primary endpoint with a 95% relative reduction in new gadolinium (Gd)-enhancing T1 lesions compared to placebo over weeks 8 and 12 (p=0.0009). Separately announced 24-week data supported the robust and durable activity of obexelimab, and further validated its unique inhibitory mechanism of action. Obexelimab was well tolerated, and no new safety signals were observed.
According to the company, obexelimab demonstrated a statistically significant 95% relative reduction in the cumulative number of new gadolinium (Gd)-enhancing (GdE) T1 hyperintense lesions over week 8 and week 12 compared with placebo (p=0.0009). Near-complete suppression of new GdE T1 hyperintense lesions, markers of active inflammation, was observed with obexelimab by 8 weeks of treatment and sustained through week 12. The adjusted mean number of new GdE T1 hyperintense lesions per scan was 0.01 (95% CI: 0.00, 0.06) in the obexelimab group compared to 0.23 (95% CI: 0.11, 0.51) with placebo.
The company said that over weeks 8 and 12, only two new GdE T1 lesions were observed in obexelimab-treated patients compared to 19 in placebo-treated patients, with 97.2% of obexelimab treated patients free from T1 lesions over this period. Consistent with the inhibitory mechanism of obexelimab, mean B cell values remained within the normal range for obexelimab-treated patients. The safety profile of obexelimab was consistent with that observed in prior completed trials, including cases of infections and hypersensitivity, most commonly mild injection site reactions.
The company also reported that separately announced 24-week data further confirmed the robust and durable activity of obexelimab. The highly statistically significant reductions in total GdE T1 lesions observed with obexelimab over weeks 8 and 12 were maintained through week 24; unadjusted means were 0.87 at baseline, 0.08 at week 12 and 0.04 at week 24 for obexelimab indicating a 95% reduction. Obexelimab meaningfully reduced serum Neurofilament Light (NfL) by 40% through week 24; 15.28 pg/mL at baseline declining to 12.7 pg/mL at week 12 and 9.2 pg/mL at week 24. New and/or enlarging T2 lesions were also lower in the obexelimab arm and the Expanded Disability Status Scale (EDSS) scores were stable, indicating a lack of progression in physical disability. No new safety signals were observed at week 24.
According to Lonnie Moulder, Founder and Chief Executive Officer of Zenas, the company is pleased that the MoonStone study was selected as a late-breaker oral presentation at ACTRIMS Forum 2026, and is excited to share that through week 24 of the MoonStone trial, obexelimab demonstrated robust and durable activity, including near complete elimination of gadolinium-enhancing T1 hyperintense lesions. Moulder added that the MoonStone 12-week primary endpoint results and 24-week data provide additional strong validation of obexelimab and the potential of B cell inhibition to offer meaningful clinical activity in a wide range of autoimmune diseases. With its unique mechanism of action, compelling safety and tolerability profile, and at-home subcutaneous self-administration, obexelimab has the potential to become a franchise molecule and meaningfully impact the lives of patients living with autoimmune diseases. The company looks forward to reporting on additional progress this year, including the submission of marketing applications for Immunoglobulin G4-Related Disease to the U.S. FDA and the European Medicines Agency and topline results from its Phase 2 SunStone trial for Systemic Lupus Erythematosus.
The ongoing open-label expansion portion of the Phase 2 MoonStone trial continues to follow patients for longer-term outcomes. Within Multiple Sclerosis, Zenas is currently advancing orelabrutinib, a potentially best-in-class, highly selective central nervous system (CNS)-penetrant, oral, small molecule Bruton’s Tyrosine Kinase (BTK) inhibitor. Orelabrutinib is being studied in a global Phase 3 clinical trial in patients with Primary Progressive Multiple Sclerosis (PPMS). Zenas also expects to initiate a global Phase 3 trial of orelabrutinib in patients with non-active Secondary Progressive Multiple Sclerosis (naSPMS) in this quarter.
Obexelimab is a bifunctional monoclonal antibody designed to bind both CD19 and FcγRIIb, which are broadly present across B cell lineage, to inhibit the activity of cells that are implicated in many autoimmune diseases without depleting them. This unique inhibitory mechanism of action and self-administered, subcutaneous injection regimen may broadly and effectively address the pathogenic role of the B cell lineage in chronic autoimmune disease. Obexelimab has been evaluated in eight clinical trials in a total of 383 subjects. Obexelimab was well tolerated and demonstrated clinical activity across these clinical trials. The registrational Phase 3 INDIGO trial for Immunoglobulin G4-Related Disease (IgG4-RD) met its primary endpoint and all four key secondary endpoints with high statistical significance. Zenas remains on track to submit a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) in the second quarter of 2026 and a Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) in the second half of 2026. The trial continues to evaluate patients in the 3-year open label extension period which will further build upon the largest body of clinical data reported for IgG4-RD patients to date. A randomized Phase 2 trial for Systemic Lupus Erythematosus is ongoing and Zenas expects to report topline results, including biomarker data from this trial in the fourth quarter of 2026.
Zenas BioPharma is a clinical-stage global biopharmaceutical company committed to becoming a leader in the development and commercialization of transformative therapies for patients living with autoimmune diseases. Zenas’ earlier stage programs include ZB021, a preclinical, potentially best-in-class, oral, IL-17AA/AF inhibitor, and ZB022, a preclinical, potentially best-in-class, oral, brain-penetrant, TYK2 inhibitor. Zenas expects to initiate Phase 1 clinical development for ZB021 in 2026. Pending Phase 1 data, Zenas expects to advance development of ZB021 for rheumatic and/or dermatologic diseases. In addition, Zenas expects to initiate Phase 1 clinical development for ZB022 in 2026. Pending Phase 1 data, Zenas expects to advance development of ZB022 for neurologic diseases.
Source: Zenas BioPharma
