Zenas BioPharma (ZBIO) Investor update summary

Pipeline and upcoming milestones

• SunStone Phase 2b topline overall-population and biomarker results expected in 4Q26; ZB021 SAD/MAD data also expected in 4Q26.

• Obexelimab IgG4-RD BLA under FDA review with a May 27, 2027 PDUFA date; EMA marketing authorization application submitted, with launch expected several weeks after approval in Q2.

• Orelabrutinib Phase 3 PriMroSe in PPMS and Monarch in naSPMS ongoing; initial clinical data for ZB022 and ZB014 expected in 2027.

• Obexelimab OLE and vaccine data scheduled for presentation at ACR, November 6–11.

Obexelimab in SLE

• SunStone is a randomized, double-blind, placebo-controlled Phase 2b trial of weekly obexelimab or placebo for 24 weeks, with 95 patients per arm; BICLA is primary and SRI-4 is also assessed at week 24.

• Safety population n=190; mITT efficacy population n=160 and biomarker population n=177; BICLA and SRI-4 analyses include overall and biomarker-positive populations. Trial powered to detect a ~20% treatment-placebo difference at alpha 0.10, assuming 30% placebo response.

• Exploratory biomarker analyses will assess multiple cutoffs and efficacy-population frequency; results may inform prospective Phase 3 validation and an overall-population hierarchical or biomarker-positive-only strategy.

• Prior Phase 2a post-hoc analysis showed week-32 improvement versus placebo in 17% of the intention-to-treat group and 52% of biomarker-positive patients; results considered hypothesis-generating.

• U.S. SLE opportunity estimated at >$8B, with ~125,000 moderate-to-severe patients and >35,000 estimated biomarker-positive patients.

ZB021 oral IL-17 inhibitor

• Oral allosteric inhibitor of IL-17AA and IL-17AF; keratinocyte assay IC50 1.5 ± 0.49 nM and IC90 6.8 ± 8.5 nM; rat arthritis studies showed dose-dependent activity comparable to a reference anti-IL-17 biologic.

• Non-human-primate oral bioavailability was ~80%; minipig skin and joint concentrations were similar to or above plasma, supporting potential exposure in disease-relevant tissues.

• Phase 1 healthy-volunteer study includes single- and multiple-ascending-dose cohorts, once-daily dosing for seven days, and fed/fasted comparisons; primary objective is safety and tolerability, with PK assessed secondarily.

• Dose selection targets average drug concentration above the IC90 in disease-relevant tissues; upcoming data will include safety, tolerability and PK, including Cavg relative to IC90.

• Rheumatologic indications are the strategic direction for proof of concept; psoriatic arthritis and axial disease highlighted for unmet need, with tissue penetration and once-daily oral dosing as potential differentiators. Patient proof-of-concept study planned at two dose levels.