Zenas BioPharma (ZBIO) Study Result summary

INDIGO Phase III Trial Results and Study Design

• Obexelimab met the primary endpoint, reducing IgG4-RD flare risk by 56% versus placebo (HR=0.443, p=0.0005), with 27% of patients in the obexelimab arm experiencing flares compared to 55% in placebo; over 70% were protected from flare.

• All four key secondary endpoints were achieved with high statistical significance, including time to flare, flare rate, complete remission, and reduced glucocorticoid rescue therapy use.

• The trial enrolled 194 patients globally in a multicenter, randomized, double-blind, placebo-controlled design, representing the largest IgG4-RD clinical trial to date, with balanced baseline characteristics.

• Obexelimab demonstrated a compelling safety and tolerability profile, with lower rates of serious adverse events (10% vs. 19%) and infections than placebo, and similar injection site reactions; no new safety signals or increased malignancy risk observed.

• The separation in flare rates between arms became apparent after steroid taper, with sustained benefit in the obexelimab group.

Mechanism of Action, Administration, and Differentiation

• Obexelimab is a bifunctional antibody targeting CD19 and FcγRIIb, inhibiting B cells without depletion, offering a unique mechanism compared to current therapies.

• It is the only at-home, subcutaneously administered treatment for IgG4-RD, providing convenience over infusion therapies and no need for glucocorticoid premedication.

• The safety profile allows for vaccination pauses and is particularly advantageous for older patients.

• At-home administration may result in lower out-of-pocket costs for patients and more manageable costs for payers.

• KOLs and advisors view the efficacy and safety profile as highly favorable for first-line use.

Market Opportunity, Disease Context, and Future Plans

• IgG4-RD is a chronic fibro-inflammatory disease affecting multiple organs, with an estimated 20,000 diagnosed patients in the U.S. and up to 40,000 total prevalence; similar numbers in Europe.

• The U.S. and European market opportunity is estimated at $3 billion and $2 billion, respectively.

• Obexelimab is positioned as a first-line, long-term maintenance therapy, with BLA submission to FDA planned for Q2 2026 and MAA to EMA in 2H 2026.

• Bristol Myers Squibb holds exclusive rights for obexelimab in several Asia-Pacific territories.

• Additional data from MoonStone RMS and SunStone SLE trials, as well as pipeline expansion with orelabrutinib and oral IL-17 and TYK2 inhibitors, are expected.