This report is based on public company disclosures, filings and announcements reviewed by GSN; figures are as stated by the company and have not been independently verified.

Zenas BioPharma Inc (Nasdaq: ZBIO) said on September 22, 2026 that further data from its Phase 3 INDIGO trial of obexelimab in immunoglobulin G4-related disease will be presented at two meetings: the 6th International Symposium on IgG4-Related Disease in Cambridge, Massachusetts on October 8 to 10, and the American College of Rheumatology’s ACR Convergence 2026 in Orlando on November 6 to 11.

Three analyses are scheduled. Longer-term flare protection and safety data from the INDIGO open-label extension will be presented on October 10 by Emma Culver of the University of Oxford. An analysis titled “Obexelimab Reduced Glucocorticoid-Associated Toxicity in Patients with IgG4-Related Disease,” presented by Matthew Baker of Stanford University, is scheduled as an oral presentation on October 10 and again at ACR on November 9 as abstract 1882. A third, on influenza and SARS-CoV-2 vaccine responses following a treatment-free window of obexelimab, presented by Guy Katz of Massachusetts General Hospital, is a poster at both meetings, abstract 2612 at ACR.

Lisa von Moltke, the company’s head of research and development and chief medical officer, said the presentations build on the Phase 3 INDIGO results presented earlier this year. Obexelimab is an antibody designed to bind both CD19 and FcγRIIb on B cells, inhibiting rather than depleting them, and is given by self-administered subcutaneous injection. The company said the drug has been evaluated in nine clinical trials in 667 subjects. Separately, it said topline results from the Phase 2 SunStone trial of obexelimab in systemic lupus erythematosus are expected in the fourth quarter of 2026.

Reading the release

The release announces that data will be presented; it contains no data. What it does contain is the titles of the abstracts, and two of the three titles state a conclusion: that obexelimab “reduced” steroid-associated toxicity, and that vaccine responses were “clinically meaningful.” Abstract titles are written by the authors and accepted by the meeting; the numbers behind them are what the meetings will show. Conference organisers generally publish abstracts ahead of the meeting, and the release does not say when these will appear.

Only one of the three is described as new. The open-label extension data on longer-term flare protection is the item the release calls new. The steroid-toxicity and vaccine analyses are “additional analyses” of the same Phase 3 trial whose primary results were presented earlier this year, which means they are secondary cuts of an existing dataset rather than new trial results.

Why these two secondary analyses exist is worth spelling out, because they are the company’s argument for the drug beyond its primary endpoint. IgG4-related disease is treated with glucocorticoids, and the long-term harms of steroids are the reason a steroid-sparing therapy is sought; an analysis showing less steroid toxicity is a claim about practical benefit, not just about flares. The vaccine analysis speaks to the drug’s design: antibodies that deplete B cells are known to blunt vaccine responses, and obexelimab’s pitch is that it inhibits B cells without depleting them. Whether a “treatment-free window” was needed to get those vaccine responses, and how long it was, is the detail to look for.

Two things the release does not mention: a regulatory submission, or its timing. Its forward-looking statements refer generically to the timing of regulatory submissions and approvals. And in the same statements the company lists, as risks it faces, that its sole contract manufacturer for obexelimab is WuXi Biologics (Hong Kong) Limited and its partner InnoCare is in China, that it needs substantial additional financing, and that it carries indebtedness. Those are the company’s own words about itself, and they sit in the same document as the presentation schedule.

Questions worth asking

What is the flare rate over the extended follow-up, and against what? An open-label extension has no placebo arm, so the comparison will be with the trial’s earlier blinded period or with history, and the choice matters.

How was steroid toxicity measured, and over what period? The abstract title says “reduced”; the presentation will have to say by how much, on which index, and compared with what.

What does the “treatment-free window” mean for dosing in practice? If patients must pause the drug to respond to vaccines, that is a feature of how the drug would be used.

When does the company intend to file for approval? The release does not say, and the question is the one the meetings will not answer.

Key terms in this story

Open-label extension. A continuation of a trial in which every participant receives the active drug and everyone knows it. It measures how a drug performs over a longer period; it cannot measure the drug against a placebo.

Glucocorticoid-sparing. A therapy is steroid-sparing if patients on it need less of the steroids that are the standard treatment. Because long-term steroid use causes its own harm, reducing that exposure is a treatment goal in its own right.

Non-depleting B-cell inhibition. Some antibodies treat autoimmune disease by destroying B cells; obexelimab is designed to switch them off instead. The intended advantage is a quicker return of normal immune function, including the response to vaccines, when treatment stops.

Oral presentation and poster. Meetings assign a small number of abstracts to spoken sessions and the rest to posters. An oral slot is a judgement by the meeting’s reviewers about the interest of the work, not about its result.

What to watch

October 8, 2026: vaccine-response poster at the IgG4-RD symposium, Cambridge, Massachusetts.

October 10, 2026: oral presentations on steroid toxicity at 9:00 a.m. Eastern and on longer-term open-label extension results at 9:40 a.m. Eastern.

November 9, 2026, 1:30 p.m. Eastern: steroid-toxicity oral presentation at ACR Convergence, abstract 1882; November 10: vaccine-response poster, abstract 2612.

Fourth quarter of 2026: topline results from the Phase 2 SunStone trial in lupus, per the company.

Sources