Zenas Puts Obexelimab's 12-Month Flare-Free Probability At 0.93 Or 0.87, Depending On Who Counts
Open-label extension data in IgG4-related disease also cover steroid toxicity and a small vaccine sub-study; lupus results are expected next.
Zenas BioPharma said the 12-month probability of staying flare-free on obexelimab was 0.93 or 0.87, depending on how flares were counted, in open-label extension data from its Phase 3 INDIGO trial. The company furnished the data in an 8-K dated Tuesday, built on a press release it issued Monday.
What the extension data show
Patients who finished the 52-week randomized period of INDIGO could join an open-label extension and take 250 mg of obexelimab by weekly injection under the skin. Open-label means everyone knew they were getting the drug, and the extension has no placebo comparison.
The 0.93 figure rests on flares confirmed by investigators and an adjudication committee that required rescue therapy. The 0.87 figure counts flares requiring rescue therapy as determined by investigators. Five patients were still pending adjudication at the data cutoff.
Median cumulative glucocorticoid rescue dose was 0 mg and the mean was 105 mg. Adverse event rates were comparable to or lower than in the randomized period.
The data were presented at the 6th International Symposium on IgG4-Related Disease, held October 8-10 in Cambridge, Massachusetts.
Steroid toxicity and the vaccine sub-study
A separate analysis of the randomized period used the Glucocorticoid Toxicity Index. At week 52, obexelimab reduced cumulative steroid toxicity versus placebo, with a Cumulative Worsening Score difference of -11.4 (p=0.021). Fewer obexelimab patients reached clinical thresholds for that toxicity.
In a small sub-study, patients vaccinated during a planned treatment-free window showed seroimmunity to influenza in 6 of 7 participants and to COVID-19 in 4 of 4. No flares were seen during the window, which averaged 34.6 days. Seven participants kept pre-existing immunity markers after long-term treatment: 71% for influenza and 50% for COVID-19.
CEO Lonnie Moulder said the findings "reinforce the potential role of obexelimab in long-term disease management."
What to watch
Zenas said topline results from its Phase 2 SunStone trial in systemic lupus erythematosus are expected in the fourth quarter of 2026. Obexelimab has been evaluated in nine clinical trials in 667 subjects, including INDIGO, the company said.
ZBIO closed at $26.40 on Monday, down about 3%, before the data were disclosed Tuesday at 6:01 a.m. ET.
The next dated marker is the SunStone lupus readout, which Zenas expects in the fourth quarter of 2026.
Sources
- 8-K Filing — Zenas BioPharma, Inc. (ZBIO) — SEC EDGAR
- Exhibit tm2627406d1_ex99-1.htm — Zenas BioPharma, Inc. 8-K exhibit — SEC EDGAR
- Zenas BioPharma (ZBIO) Is Down 5.1% After New Phase 3 Obexelimab IgG4-RD Data Release — Yahoo Finance
- Zenas BioPharma Announces Upcoming Presentations of Orelabrutinib Data in Relapsing Remitting Multiple Sclerosis, Clinical Trial Designs in Progressive Multiple Sclerosis and Other Multiple Sclerosis Portfolio Data at MSToronto2026 — Yahoo Finance
- Zenas BioPharma Announces Upcoming Presentations of — rss.globenewswire.com
