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The FDA is expected to decide on Obexelimab for IgG4-related disease by May 27, 2027, under a BLA from Zenas BioPharma.
What the FDA is deciding on Obexelimab for IgG4-related disease
The FDA is reviewing Zenas BioPharma's application to approve Obexelimab for IgG4-related disease.
Self-injected antibody that dials down B cells without depleting them. In the Phase 3 INDIGO trial it cut the risk of IgG4-RD flare by 56% over 52 weeks, with 73% of treated patients flare-free versus 45% on placebo, and reduced steroid use. Zenas disclosed the acceptance and date in its August 13, 2026 quarterly update.
Who the Obexelimab decision matters to
IgG4-related disease is a chronic fibroinflammatory condition characterized by tumor-like swelling in affected organs, dense lymphoplasmacytic infiltration rich in IgG4-positive plasma cells, storiform fibrosis, and often (but not always) elevated serum IgG4 levels. It can affect virtually any organ but most commonly involves the pancreas, bile ducts, salivary glands, lacrimal glands, kidneys, and retroperitoneum.
Left untreated, it causes progressive organ damage and fibrosis.
Prevalence: Approximately 5 in 100,000 people; an estimated 57,000 diagnosed individuals in the U.S. as of 2024. See our full IgG4-Related Disease page for current treatments, recruiting trials, and community resources.
How Obexelimab works
Obexelimab: antibody with 2 binding ends that attaches to CD19 and to FcγRIIb on B cells at the same time, sending a stop signal that holds B cells back without destroying them. Our full Obexelimab profile covers how it works, side effects in plain language, and its trial history.
What an approval or a rejection of Obexelimab would mean
An approval starts a second race rather than ending the first one: specialty pharmacy setup, insurance review, and patient assistance typically take weeks even when everything goes right. Our guide to the 90 days after a rare disease approval explains the timeline and the moves families can make on day 1.
A complete response letter would mean the FDA declined to approve in the application's current form. The letter describes what the FDA wants addressed, and the company then decides whether to resubmit, run more studies or stop. Either way, this page updates with the outcome and what it means.
Where IgG4-Related Disease treatment stands today
Read our full IgG4-Related Disease treatment summary
The approval of inebilizumab (Uplizna) in April 2025 was a turning point for IgG4-RD, but research is far from over. Trials are studying optimal duration of B-cell depletion therapy, whether early aggressive treatment prevents irreversible fibrosis, and how to manage the subset of patients who relapse despite B-cell targeted therapy.
Ask your rheumatologist or treating specialist whether tissue biopsy has confirmed your diagnosis (serum IgG4 alone is insufficient), whether your current organ involvement warrants immediate inebilizumab or whether glucocorticoid induction is appropriate first, and whether PET-CT surveillance should be part of your monitoring plan to detect subclinical organ involvement.
If you were initially misdiagnosed with cancer, lymphoma, or another autoimmune condition, re-evaluation by an IgG4-RD specialist at an academic center is worthwhile. Mass General, Mayo Clinic, and Stanford have dedicated IgG4-RD programs.
The IgG4-Related Disease page has every treatment and trial →Meanwhile, 25 IgG4-Related Disease studies are recruiting or not yet recruiting
Whatever the FDA decides here, research on IgG4-Related Disease does not stop. Of these, 20 test a treatment; the others follow patients over time. The most recently updated:
We'll email you when the decision is public, with what it means in plain language, and when new trials open for IgG4-Related Disease. Unsubscribe anytime.
- Trial Alerts, when a new trial opens or a trial changes
- Disease Updates, FDA decisions and condition news, usually 1 or 2 emails a month
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Frequently asked questions
When will the FDA decide on Obexelimab?
The FDA's target date (PDUFA date) for Obexelimab in IgG4-related disease is May 27, 2027.
Who disclosed it: Zenas BioPharma. The FDA does not publish these dates.
Can it move: the FDA can act early, and a major amendment to the application can push the date back 3 months.
Source: Zenas press release
What is Obexelimab being reviewed for?
Zenas BioPharma submitted a BLA for Obexelimab in IgG4-related disease.
What to know: Self-injected antibody that dials down B cells without depleting them. In the Phase 3 INDIGO trial it cut the risk of IgG4-RD flare by 56% over 52 weeks, with 73% of treated patients flare-free versus 45% on placebo, and reduced steroid use. Zenas disclosed the acceptance and date in its August 13, 2026 quarterly update.
How it works: Antibody with 2 binding ends that attaches to CD19 and to FcγRIIb on B cells at the same time, sending a stop signal that holds B cells back without destroying them.
More: the Obexelimab drug page explains it in plain language.
Is there already an FDA-approved treatment for IgG4-Related Disease?
Yes. Trial Friend's drug list includes 1 FDA-approved drug for IgG4-Related Disease.
Approved: Uplizna (inebilizumab).
Check: the IgG4-Related Disease page also searches FDA drug labels for approved treatments.
What did the Obexelimab trials show?
INDIGO (NCT05662241) is a Phase 3, double-blind, placebo-controlled trial in adults with active IgG4-related disease. From January 2023 through November 2024 it randomized 194 people, 97 to each group, to weekly obexelimab or placebo for 52 weeks; in both groups, steroids were tapered on a set schedule and stopped by week 8.
More: the Obexelimab drug page has the full trial history and sources.
What are the side effects of Obexelimab?
Obexelimab has no FDA label, so its official side effects and warnings are not set. In INDIGO, side effects more common on obexelimab than placebo included joint pain (19.6% vs 11.3%), allergic-type reactions called hypersensitivity (16.5% vs 11.3%) and diarrhea (11.3% vs 6.2%).
More: the Obexelimab drug page has the safety details reported so far.
Can I get Obexelimab before the FDA decides?
Usually only through a clinical trial or an expanded access program, and the company decides whether to offer one.
Trials: 25 IgG4-Related Disease studies are recruiting or not yet recruiting, 20 of them testing a treatment. See them.
Check your fit: Match Me compares your details with every open trial.
Expanded access: your doctor can ask Zenas BioPharma directly. Registered programs are listed on ClinicalTrials.gov.
How much will Obexelimab cost?
Zenas BioPharma has not announced a price. Drugmakers usually set it around approval.
Help paying: drugmaker programs and charity funds usually open at launch.
Find help: the patient assistance finder lists programs by insurance type.
What happens after the Obexelimab decision?
This page updates with the outcome the day it is announced.
If approved: getting the drug still takes time. Specialty pharmacy setup, insurance review and patient assistance often take weeks. Our guide covers what families can do on day 1.
If not approved: a complete response letter means the FDA declined the application in its current form. Many are about manufacturing or how data were presented, and companies often resubmit.
Where this date comes from
The FDA does not publish PDUFA dates; companies disclose them. This one comes from Zenas press release. Dates can move, and the FDA can act early or late. This page rechecks against our calendar, which is re-verified daily.