Upstream Bio (UPB) investor relations material

Company overview and strategy

• Clinical-stage immunology company developing verekitug, a high-potency TSLP receptor antagonist for severe respiratory diseases.

• Completed Phase 2 trials in severe asthma and CRSWNP; ongoing Phase 2 in COPD.

• Targeting large commercial opportunities, with asthma and COPD markets projected to exceed $35B globally by 2033.

• Phase 3 trials in severe asthma and CRSWNP planned for Q1 2027, with FDA engagement in mid-2026.

• Existing capital expected to fund operations through 2027.

Verekitug mechanism and clinical profile

• Verekitug is a fully human IgG1 antibody, uniquely antagonizing the TSLP receptor with ~300-fold greater potency than tezepelumab.

• Demonstrated robust efficacy and favorable safety in ~500 participants across Phase 1 and 2 trials.

• Enables extended interval dosing (every 12 weeks) with strong clinical benefit in severe asthma and CRSWNP.

• Well-characterized immunogenicity profile with no meaningful impact on safety or efficacy.

Market opportunity and positioning

• Severe asthma and COPD represent the largest biologics markets, with US accounting for ~80% of severe asthma biologic sales.

• Less than 25% of eligible severe asthma patients currently receive biologics, indicating significant growth potential.

• Tezspire, a comparator, is projected to reach over $3B in severe asthma and $5B in COPD annual sales by 2033.

• Quarterly at-home dosing and best-in-class efficacy are prioritized to maximize commercial value.