Zenas BioPharma Inc. (NASDAQ:ZBIO) stock is trading lower on Monday after the company released results from the Phase 3 INDIGO trial of obexelimab in Immunoglobulin G4-Related Disease (IgG4-RD).
IgG4-RD is an immune system disorder where the body creates excess IgG4 antibodies, leading to inflammation and dense, tumor-like tissue growths (fibrosis) in multiple organs.
Obexelimab met the primary endpoint, demonstrating a highly statistically significant and clinically meaningful 56% reduction in the risk of IgG4-RD flare compared to placebo during the 52-week randomized placebo-controlled period.
Obexelimab also met and demonstrated highly statistically significant activity compared to placebo on all four key secondary endpoints, which were reduction in investigator-assessed IgG4-RD flare, the number of flares requiring rescue therapy, the proportion of patients achieving complete remission, and the cumulative use of IgG4-RD rescue therapy.
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Rates of infections, including Grade 3, were lower in the obexelimab arm compared to placebo, and the incidence of injection site reactions was similar across both study arms.
The company expects that full data from the INDIGO trial will be presented at a future medical meeting.
Despite touting encouraging data from the pivotal trial, Zenas BioPharma stock is trading lower.
In April 2025, the U.S. Food and Drug Administration (FDA) approved Amgen Inc.’s (NASDAQ:AMGN) Uplizna (inebilizumab-cdon) as the first and only treatment for adult patients with IgG4-RD.
The approval was supported by data from the MITIGATE trial that showed an 87% reduction in the risk of IgG4-RD flare compared to placebo during the 52-week placebo-controlled period.
10.3% of participants receiving Uplizna experienced a flare compared to 59.7% of participants receiving a placebo.
Amgen added Uplizna via a $27.8 billion acquisition of Horizon Therapeutics.
What’s Next
Zenas anticipates submitting the obexelimab Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) for IgG4-RD in the second quarter of 2026.
Zenas also intends to submit a Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) in the second half of 2026. Zenas’ partner Bristol Myers Squibb Co (NYSE:BMY) holds exclusive development and commercialization rights for obexelimab in Japan, South Korea, Taiwan, Hong Kong, Singapore, and Australia.
Zenas also expects to report topline results of the obexelimab Phase 2 SunStone trial in SLE in the fourth quarter of 2026.
ZBIO Price Action: Zenas BioPharma shares were down 53.14% at $16.16 at the time of publication on Monday, according to Benzinga Pro data.
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