European regulators weigh approval of IgG4-RD injection therapy

The European Medicines Agency (EMA) has accepted for review an application seeking approval of the experimental injection therapy obexelimab for people with  immunoglobulin G4-related disease (IgG4-RD).

The agency confirmed that the Marketing Authorization Application (MAA) submitted by the therapy’s developer, Zenas Biopharma, contains all the required information for scientific assessment. Once the formal scientific review starts, a decision is expected in about a year.

The European milestone follows similar progress in the U.S., where the Food and Drug Administration (FDA) accepted Zenas’ Biologics License Application (BLA), setting a target date of May 27, 2027.

“Following the FDA’s acceptance of our BLA in August of this year and the recent submission of our MAA to the EMA, we remain focused on commercial readiness ahead of the potential launch,” Lonnie Moulder, founder and CEO of Zenas, said in a company press release.

Both regulatory applications are supported primarily by positive results from the placebo-controlled portion of the global Phase 3 INDIGO clinical trial (NCT05662241). This portion tested weekly under-the-skin injections of obexelimab against a placebo in 194 adults with active IgG4-RD for up to one year.

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Single-dose pen option

The European application includes data showing that obexelimab reaches comparable levels in the bloodstream whether administered with the prefilled syringe used in the INDIGO trial or a single-dose, prefilled pen. This suggests that either device could be used to deliver the treatment.

Zenas plans to submit these data separately to the FDA if obexelimab is ultimately approved in the U.S.  The company said the pen could offer patients a more convenient way to take the treatment.

IgG4-RD occurs when clusters of immune cells, mainly B-cells producing IgG4 antibodies, accumulate in tissues. This causes inflammation and scarring that can damage organs and lead to a wide range of IgG4-RD symptoms.

First-line treatment for IgG4-RD commonly relies on glucocorticoids, a type of anti-inflammatory and immunosuppressive treatment. While effective at dampening inflammation and easing symptoms, high doses or prolonged use can cause serious side effects.

To reduce reliance on glucocorticoids, doctors may use glucocorticoid-sparing treatments, including therapies that kill B-cells. However, because B-cells also play an important role in protecting the body against infections, eliminating them can weaken immune responses, including responses to vaccines.

Obexelimab takes a different approach. Rather than killing B-cells, it is designed to reduce their activity by blocking two proteins, CD19 and FCGR2B, involved in their activation. In doing so, the therapy aims to control IgG4-RD while preserving levels of these immune cells.

In INDIGO, all participants were on glucocorticoids at study’s start. Doses were gradually reduced and discontinued over the first two months of treatment with either obexelimab or a placebo. Afterward, these medications were used only to manage disease flares.

Obexelimab reduced the risk of flares by 56% over one year when compared with the placebo, meeting the trial’s main goal.

All four key secondary goals were also met. Compared with the placebo, obexelimab reduced the annual rate of disease flares requiring rescue treatment with glucocorticoids by 52% and increased the proportion of participants achieving complete remission (37.1% vs. 19.6%).

Treatment also significantly reduced the cumulative dose of glucocorticoids needed to manage disease flares, by about 65%. Correspondingly, fewer obexelimab-treated participants experienced clinically meaningful worsening of glucocorticoid-related side effects. Obexelimab was also generally safe and well tolerated.

Meanwhile, Zenas continues to gather evidence on obexelimab’s benefits, including its long-term safety and effectiveness, through INDIGO’s ongoing open-label extension portion. In this part of the study, all participants are receiving obexelimab for up to three years.

Findings from the extension portion, covering more than one year of treatment, showed that most participants (87%-93%) experienced no flares during that period, and that obexelimab continued to be associated with lower glucocorticoid toxicity.

In addition, data from a small substudy showed that most participants who temporarily paused treatment around vaccination against influenza or COVID-19 to allow the immune system to respond were able to produce protective antibodies. No disease flares occurred during the treatment interruption, which lasted an average of a month.

“We continue to generate meaningful data supporting the unique … mechanism of obexelimab, including open-label extension data, data demonstrating the reduction in glucocorticoid-associated toxicity, and data from the INDIGO vaccine sub-study,” Moulder said, adding that the company expects to present “open-label extension data from INDIGO in a late-breaking poster at [American College of Rheumatology] Convergence 2026 next week.”