– Webcast to be held Wednesday, February 11, 2026, at 8:00 a.m. ET –

WALTHAM, Mass., Feb. 10, 2026 (GLOBE NEWSWIRE) — Upstream Bio, Inc. (Nasdaq: UPB), a clinical-stage company developing treatments for inflammatory diseases, with an initial focus on severe respiratory disorders, today announced it will report top-line results from the Phase 2 VALIANT trial of verekitug, the only known antagonist currently in clinical development that targets and inhibits the thymic stromal lymphopoietin (TSLP) receptor, on Wednesday, February 11, 2026 at 8:00 a.m. ET.

The VALIANT trial (NCT06196879) is a Phase 2 global, randomized, double-blind, placebo-controlled, dose-ranging, parallel group clinical trial that evaluated the safety and efficacy of verekitug for up to 60 weeks, with a minimum of 24 weeks of treatment, in 478 patients with severe asthma. Participants were randomized into one of four groups, receiving either 100 mg of verekitug every 24 weeks, 400 mg of verekitug every 24 weeks, 100 mg of verekitug every 12 weeks, or placebo, administered subcutaneously.

Webcast Information
Upstream Bio’s webcast to discuss the top-line results from the Phase 2 VALIANT trial will begin Wednesday, February 11, 2026, at 8:00 a.m. ET. The live webcast can be accessed via this link or on the Events tab on the Investors section of the Company’s website at https://investors.upstreambio.com/news-events/events. A replay of the webcast will be available on the website following the call.

About Upstream Bio
Upstream Bio is a clinical-stage biotechnology company developing treatments for inflammatory diseases, with an initial focus on severe respiratory disorders. The Company is developing verekitug, the only known antagonist currently in clinical development that targets the receptor for thymic stromal lymphopoietin (TSLP), a cytokine which is a clinically validated driver of inflammatory response positioned upstream of multiple signaling cascades that affect a variety of immune mediated diseases. The Company has advanced this highly potent monoclonal antibody into separate Phase 2 trials for the treatment of chronic rhinosinusitis with nasal polyps (CRSwNP), severe asthma, and chronic obstructive pulmonary disease (COPD). Upstream Bio’s team is committed to maximizing verekitug’s unique attributes to address the substantial unmet needs for patients underserved by today’s standard of care. To learn more, please visit www.upstreambio.com.

Investor and Media Contact:
Meggan Buckwell
Director, Corporate Communications and Investor Relations
ir@upstreambio.com