Upstream Bio Soars 5.08% on Positive Verekitug Trial Results

Upstream Bio's stock surged 5.08% in pre-market trading on September 2, 2025, driven by the release of positive top-line results from the Phase 2 VIBRANT trial of its drug verekitug for the treatment of chronic rhinosinusitis with nasal polyps (CRSwNP).

The Phase 2 VIBRANT trial, a global, randomized, placebo-controlled study, evaluated the efficacy and safety of verekitug, a unique monoclonal antibody targeting the TSLP receptor, in patients with CRSwNP. The trial's primary endpoint focused on measuring changes in endoscopic nasal polyp score at Week 24. Participants received either 100 mg of verekitug or a placebo subcutaneously every 12 weeks for 24 weeks.

Upstream Bio, a clinical-stage biotechnology company, is developing treatments for inflammatory diseases, with an initial focus on severe respiratory disorders. The company's verekitug is the only known antagonist in clinical development that targets the receptor for thymic stromal lymphopoietin (TSLP), a cytokine that drives inflammatory responses. The company has advanced this highly potent monoclonal antibody into separate Phase 2 trials for the treatment of CRSwNP, severe asthma, and chronic obstructive pulmonary disease (COPD).

Upstream Bio will host a conference call and webcast on September 2, 2025, at 8:00 a.m. ET to discuss the top-line data results from the Phase 2 VIBRANT trial. The live webcast can be accessed via the company's website, and a replay will be available following the call. The company'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.